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• Cisco StackWise and StackWise Plus Technology

  May 4, 2016 by Cisco Channel / 626 Views

  This white paper provides an overview of the Cisco StackWise and Cisco StackWise Plus technologies and the specific mechanisms that they use to create a unified, logical switching architecture through the linkage of multiple, fixed configuration switches. This paper focuses on the following critical aspects of the Cisco StackWise and Cisco StackWise Plus technologies: stack interconnect behavior, stack creation and modification; Layer 2 and Layer 3 forwarding; and quality-of-service (QoS) mechanisms. The goal of the paper is to help the reader understand how the Cisco StackWise and StackWise Plus technologies deliver advanced performance for voice, video, and Gigabit Ethernet applications. First, this white paper will discuss the Cisco Catalyst 3750 Series Switches and StackWise and second, the Cisco Catalyst 3750-E and Catalyst 3750-X Series Switches with StackWise Plus will be discussed, highlighting the differences between the two. Please note that the Cisco Catalyst 3750-E and Catalyst 3750-X will run StackWise Plus when connected to a stack of all Cisco Catalyst 3750-E and Catalyst 3750-X switches, while it will run StackWise if there is one or more Cisco Catalyst 3750 in the stack. (See Figures 1 and 2.)

  Figure 1. Stack of Cisco Catalyst 3750 Series Switches with StackWise Technology

  

  Figure 2. Stack of Cisco Catalyst 3750-E Series Switches with StackWise and StackWise Plus Technologies

  

  Technology Overview

  Cisco StackWise technology provides an innovative new method for collectively utilizing the capabilities of a stack of switches. Individual switches intelligently join to create a single switching unit with a 32-Gbps switching stack interconnect. Configuration and routing information is shared by every switch in the stack, creating a single switching unit. Switches can be added to and deleted from a working stack without affecting performance.

  The switches are united into a single logical unit using special stack interconnect cables that create a bidirectional closed-loop path. This bidirectional path acts as a switch fabric for all the connected switches. Network topology and routing information is updated continuously through the stack interconnect. All stack members have full access to the stack interconnect bandwidth. The stack is managed as a single unit by a master switch, which is elected from one of the stack member switches.

  Each switch in the stack has the capability to behave as a master or subordinate (member) in the hierarchy. The master switch is elected and serves as the control center for the stack. Both the master member switches act as forwarding processors. Each switch is assigned a number. Up to nine separate switches can be joined together. The stack can have switches added and removed without affecting stack performance.

  Each stack of Cisco Catalyst 3750 Series Switches has a single IP address and is managed as a single object. This single IP management applies to activities such as fault detection, virtual LAN (VLAN) creation and modification, security, and QoS controls. Each stack has only one configuration file, which is distributed to each member in the stack. This allows each switch in the stack to share the same network topology, MAC address, and routing information. In addition, it allows for any member to become the master, if the master ever fails.

  The Stack Interconnect Functionality

  Cisco StackWise technology unites up to nine individual Cisco Catalyst 3750 switches into a single logical unit, using special stack interconnect cables and stacking software. The stack behaves as a single switching unit that is managed by a master switch elected from one of the member switches. The master switch automatically creates and updates all the switching and optional routing tables. A working stack can accept new members or delete old ones without service interruption.

  Bidirectional Flow

  To efficiently load balance the traffic, packets are allocated between two logical counter-rotating paths. Each counter-rotating path supports 16 Gbps in both directions, yielding a traffic total of 32 Gbps bidirectionally. The egress queues calculate path usage to help ensure that the traffic load is equally partitioned.

  Whenever a frame is ready for transmission onto the path, a calculation is made to see which path has the most available bandwidth. The entire frame is then copied onto this half of the path. Traffic is serviced depending upon its class of service (CoS) or differentiated services code point (DSCP) designation. Low-latency traffic is given priority.

  When a break is detected in a cable, the traffic is immediately wrapped back across the single remaining 16-Gbps path to continue forwarding.

  Online Stack Adds and Removals

  Switches can be added and deleted to a working stack without affecting stack performance. When a new switch is added, the master switch automatically configures the unit with the currently running Cisco IOS ^® Software image and configuration of the stack. The stack will gather information such as switching table information and update the MAC tables as new addresses are learned. The network manager does not have to do anything to bring up the switch before it is ready to operate. Similarly, switches can be removed from a working stack without any operational effect on the remaining switches. When the stack discovers that a series of ports is no longer present, it will update this information without affecting forwarding or routing.

  Physical Sequential Linkage

  The switches are physically connected sequentially, as shown in Figure 3. A break in any one of the cables will result in the stack bandwidth being reduced to half of its full capacity. Subsecond timing mechanisms detect traffic problems and immediately institute failover. This mechanism restores dual path flow when the timing mechanisms detect renewed activity on the cable.

  Figure 3. Cisco StackWise Technology Resilient Cabling

  

  Subsecond Failover

  Within microseconds of a breakage of one part of the path, all data is switched to the active half of the bidirectional path (Figure 4).

  Figure 4. Loopback After Cable Break

  

  The switches continually monitor the stack ports for activity and correct data transmission. If error conditions cross a certain threshold, or there is insufficient electromagnetic contact of the cable with its port, the switch detecting this then sends a message to its nearest neighbor opposite from the breakage. Both switches then divert all their traffic onto the working path.

  Single Management IP Address

  The stack receives a single IP address as a part of the initial configuration. After the stack IP address is created, the physical switches linked to it become part of the master switch group. When connected to a group, each switch will use the stack IP address. When a new master is elected, it uses this IP address to continue interacting with the network.

  Stack Creation and Modification

  Stacks are created when individual switches are joined together with stacking cables. When the stack ports detect electromechanical activity, each port starts to transmit information about its switch. When the complete set of switches is known, the stack elects one of the members to be the master switch, which will be responsible for maintaining and updating configuration files, routing information, and other stack information. The entire stack will have a single IP address that will be used by all the switches.

  1:N Master Redundancy

  1:N master redundancy allows each stack member to serve as a master, providing the highest reliability for forwarding. Each switch in the stack can serve as a master, creating a 1:N availability scheme for network control. In the unlikely event of a single unit failure, all other units continue to forward traffic and maintain operation.

  Master Switch Election

  The stack behaves as a single switching unit that is managed by a master switch elected from one of the member switches. The master switch automatically creates and updates all the switching and optional routing tables. Any member of the stack can become the master switch. Upon installation, or reboot of the entire stack, an election process occurs among the switches in the stack. There is a hierarchy of selection criteria for the election.

  1. User priority - The network manager can select a switch to be master.

  2. Hardware and software priority - This will default to the unit with the most extensive feature set. The Cisco Catalyst 3750 IP Services (IPS) image has the highest priority, followed by Cisco Catalyst 3750 switches with IP Base Software Image (IPB).

  Catalyst 3750-E and Catalyst 3750-X run the Universal Image. The feature set on the universal image is determined by the purchased license. The "show version" command will list operating license level for each switch member in the stack.

  3. Default configuration - If a switch has preexisting configuration information, it will take precedence over switches that have not been configured.

  4. Uptime - The switch that has been running the longest is selected.

  5. MAC address - Each switch reports its MAC address to all its neighbors for comparison. The switch with the lowest MAC address is selected.

  Master Switch Activities

  The master switch acts as the primary point of contact for IP functions such as Telnet sessions, pings, command-line interface (CLI), and routing information exchange. The master is responsible for downloading forwarding tables to each of the subordinate switches. Multicast and unicast routing tasks are implemented from the master. QoS and access control list (ACL) configuration information is distributed from the master to the subordinates. When a new subordinate switch is added, or an existing switch removed, the master will issue a notification of this event and all the subordinate switches will update their tables accordingly.

  Shared Network Topology Information

  The master switch is responsible for collecting and maintaining correct routing and configuration information. It keeps this information current by periodically sending copies or updates to all the subordinate switches in the stack. When a new master is elected, it reapplies the running configuration from the previous master to help ensure user and network continuity. Note that the master performs routing control and processing. Each individual switch in the stack will perform forwarding based on the information distributed by the master.

  Subordinate Switch Activities

  Each switch has tables for storing its own local MAC addresses as well as tables for the other MAC addresses in the stack. The master switch keeps tables of all the MAC addresses reported to the stack. The master also creates a map of all the MAC addresses in the entire stack and distributes it to all the subordinates. Each switch becomes aware of every port in the stack. This eliminates repetitive learning processes and creates a much faster and more efficient switching infrastructure for the system.

  Subordinate switches keep their own spanning trees for each VLAN that they support. The StackWise ring ports will never be put into a Spanning Tree Protocol blocking state. The master switch keeps a copy of all spanning tree tables for each VLAN in the stack. When a new VLAN is added or removed, all the existing switches will receive a notification of this event and update their tables accordingly.

  Subordinate switches wait to receive copies of the running configurations from the master and begin to start transmitting data upon receipt of the most current information. This helps ensure that all the switches will use only the most current information and that there is only one network topology used for forwarding decisions.

  Multiple Mechanisms for High Availability

  The Cisco StackWise technology supports a variety of mechanisms for creating high resiliency in a stack.

  • CrossStack EtherChannel^® technology - Multiple switches in a stack can create an EtherChannel connection. Loss of an individual switch will not affect connectivity for the other switches.

  • Equal cost routes - Switches can support dual homing to different routers for redundancy.

  • 1:N master redundancy - Every switch in the stack can act as the master. If the current master fails, another master is elected from the stack.

  • Stacking cable resiliency - When a break in the bidirectional loop occurs, the switches automatically begin sending information over the half of the loop that is still intact. If the entire 32 Gbps of bandwidth is being used, QoS mechanisms will control traffic flow to keep jitter and latency-sensitive traffic flowing while throttling lower priority traffic.

  • Online insertion and removal - Switches can be added and deleted without affecting performance of the stack.

  • Distributed Layer 2 forwarding - In the event of a master switch failure, individual switches will continue to forward information based on the tables they last received from the master.

  • RPR+ for Layer 3 resiliency - Each switch is initialized for routing capability and is ready to be elected as master if the current master fails. Subordinate switches are not reset so that Layer 2 forwarding can continue uninterrupted. Layer 3 Nonstop Forwarding (NSF) is also supported when two or more nodes are present in a stack.

  Layer 2 and Layer 3 Forwarding

  Cisco StackWise technology offers an innovative method for the management of Layer 2 and Layer 3 forwarding. Layer 2 forwarding is done with a distributed method. Layer 3 is done in a centralized manner. This delivers the greatest possible resiliency and efficiency for routing and switching activities across the stack.

  Forwarding Resiliency During Master Change

  When one master switch becomes inactive and while a new master is elected, the stack continues to function. Layer 2 connectivity continues unaffected. The new master uses its hot standby unicast table to continue processing unicast traffic. Multicast tables and routing tables are flushed and reloaded to avoid loops. Layer 3 resiliency is protected with NSF, which gracefully and rapidly transitions Layer 3 forwarding from the old to new master node.

  High-Availability Architecture for Routing Resiliency Using Routing Processor Redundancy+

  The mechanism used for high availability in routing during the change in masters is called Routing Processor Redundancy+ (RPR+). It is used in the Cisco 12000 and 7500 Series Routers and the Cisco Catalyst 6500 Series Switch products for high availability. Each subordinate switch with routing capability is initialized and ready to take over routing functions if the master fails. Each subordinate switch is fully initialized and connected to the master. The subordinates have identical interface addresses, encapsulation types, and interface protocols and services. The subordinate switches continually receive and integrate synchronized configuration information sent by the current master and monitor their readiness to operate through the continuous execution of self-tests. Reestablishment of routes and links happens more quickly than in normal Layer 3 devices because of the lack of time needed to initialize the routing interfaces. RPR+ coupled with NSF provides the highest performance failover forwarding.

  Adding New Members

  When the switching stack has established a master, any new switch added afterward automatically becomes a subordinate. All the current routing and addressing information is downloaded into the subordinate so that it can immediately begin transmitting traffic. Its ports become identified with the IP address of the master switch. Global information, such as QoS configuration settings, is downloaded into the new subordinate member.

  Cisco IOS Software Images Must Be Identical

  The Cisco StackWise technology requires that all units in the stack run the same release of Cisco IOS Software. When the stack is first built, it is recommended that all of the stack members have the same software feature set - either all IP Base or all IP Services. This is because later upgrades of Cisco IOS Software mandate that all the switches to be upgraded to the same version as the master.

  Automatic Cisco IOS Software Upgrade/Downgrade from the Master Switch

  When a new switch is added to an existing stack, the master switch communicates with the switch to determine if the Cisco IOS Software image is the same as the one on the stack. If it is the same, the master switch sends the stack configuration to the device and the ports are brought online. If the Cisco IOS Software image is not the same, one of three things will occur:

  1. If the hardware of the new switch is supported by the Cisco IOS Software image running on the stack, the master will by default download the Cisco IOS Software image in the master's Flash memory to the new switch, send down the stack configuration, and bring the switch online.

  2. If the hardware of the new switch is supported by the Cisco IOS Software image running on the stack and the user has configured a Trivial File Transfer Protocol (TFTP) server for Cisco IOS Software image downloads, then the master will automatically download the Cisco IOS Software image from the TFTP server to the new switch, configure it, then bring it online.

  3. If the hardware of the new switch is not supported by the Cisco IOS Software image running on the stack, the master will put the new switch into a suspended state, notify the user of a version incompatibility, and wait until the user upgrades the master to a Cisco IOS Software image that supports both types of hardware. The master will then upgrade the rest of the stack to this version, including the new switch, and bring the stack online.

  Upgrades Apply to All Devices in the Stack

  Because the switch stack behaves like a single unit, upgrades apply universally to all members of the stack at once. This means that if an original stack contains a combination of IP Base and IP services software feature sets on the various switches, the first time a Cisco IOS Software upgrade is applied, all units in the stack will take on the characteristic of the image applied. While this makes it much more efficient to add functionality to the stack, it is important to make sure all applicable upgrade licenses have been purchased before allowing units to be upgraded from IP Base .to IP Services functions. Otherwise, those units will be in violation of Cisco IOS Software policy.

  Smart Unicast and Multicast - One Packet, Many Destinations

  The Cisco StackWise technology uses an extremely efficient mechanism for transmitting unicast and multicast traffic. Each data packet is put on the stack interconnect only once. This includes multicast packets. Each data packet has a 24-byte header with an activityJame list for the packet as well as a QoS designator. The activity list specifies the port destination or destinations and what should be done with the packet. In the case of multicast, the master switch identifies which of the ports should receive a copy of the packets and adds a destination index for each port. One copy of the packet is put on the stack interconnect. Each switch port that owns one of the destination index addresses then copies this packet. This creates a much more efficient mechanism for the stack to receive and manage multicast information (Figure 5).

  Figure 5. Comparison of Normal Multicast in Stackable Switches and Smart Multicast in Cisco Catalyst 3750 Series Switches Using Cisco StackWise Technology

  

  QoS Mechanisms

  QoS provides granular control where the user meets the network. This is particularly important for networks migrating to converged applications where differential treatment of information is essential. QoS is also necessary for the migration to Gigabit Ethernet speeds, where congestion must be avoided.

  QoS Applied at the Edge

  Cisco StackWise supports a complete and robust QoS model, as shown in Figure 6.

  Figure 6. QoS Model

  

  The Cisco Catalyst 3750-E, Catalyst 3750-X and Cisco Catalyst 3750 support 2 ingress queues and 4 egress queues. Thus the Cisco Catalyst 3750-E, Catalyst 3750-X and Cisco Catalyst 3750 switches. support the ability to not only limit the traffic destined for the front side ports, but they can also limit the amounts of and types of traffic destined for the stack ring interconnect. Both the ingress and egress queues can be configured for one queue to be serviced as a priority queue that gets completely drained before the other weighted queue(s) get serviced. Or, each queue set can be configured to have all weighted queues.

  StackWise employs Shaped Round Robin (SRR). SRR is a scheduling service for specifying the rate at which packets are dequeued. With SRR there are two modes, Shaped and Shared (default). Shaped mode is only available on the egress queues. Shaped egress queues reserve a set of port bandwidth and then send evenly spaced packets as per the reservation. Shared egress queues are also guaranteed a configured share of bandwidth, but do not reserve the bandwidth. That is, in Shared mode, if a higher priority queue is empty, instead of the servicer waiting for that reserved bandwidth to expire, the lower priority queue can take the unused bandwidth. Neither Shaped SRR nor Shared SRR is better than the other. Shared SRR is used when one wants to get the maximum efficiency out of a queuing system, because unused queue slots can be used by queues with excess traffic. This is not possible in a standard Weighted Round Robin (WRR). Shaped SRR is used when one wants to shape a queue or set a hard limit on how much bandwidth a queue can use. When one uses Shaped SRR one can shape queues within a ports overall shaped rate. In addition to queue shaping, the Cisco Catalyst 3750-E can rate limit a physical port. Thus one can shape queues within an overall rate-limited port value.

  As stated earlier, SRR differs from WRR. In the examples shown in figure 7, strict priority queuing is not configured and Q4 is given the highest weight, Q3 lower, Q2 lower, and Q1 the lowest. With WRR, queues are serviced based on the weight. Q1 is serviced for Weight 1 period of time, Q2 is served for Weight 2 period of time, and so forth. The servicing mechanism works by moving from queue to queue and services them for the weighted amount of time. With SRR weights are still followed; however, SRR services the Q1, moves to Q2, then Q3 and Q4 in a different way. It doesn't wait at and service each queue for a weighted amount of time before moving on to the next queue. Instead, SRR makes several rapid passes at the queues, in each pass, each queue may or may not be serviced. For each given pass, the more highly weighted queues are more likely to be serviced than the lower priority queues. Over a given time, the number of packets serviced from each queue is the same for SRR and WRR. However, the ordering is different. With SRR, traffic has a more evenly distributed ordering. With WRR one sees a bunch of packets from Q1 and then a bunch of packets from Q2, etc. With SRR one sees a weighted interleaving of packets. In the example in Figure 7, for WRR, all packets marked 1 are serviced, then 2, then 3, and so on till 5. In SRR, all A packets are serviced, then B, C, and D. SRR is an evolution of WRR that protects against overwhelming buffers with huge bursts of traffic by using a smoother round-robin mechanism.

  Figure 7. Queuing

  

  In addition to advanced queue servicing mechanisms, congestion avoidance mechanisms are supported. Weighted tail drop (WTD) can be applied on any or all of the ingress and egress queues. WTD is a congestion-avoidance mechanism for managing the queue lengths and providing drop precedences for different traffic classifications. Configurable thresholds determine when to drop certain types of packets. The thresholds can be based on CoS or DSCP values. As a queue fills up, lower priority packets are dropped first. For example, one can configure WTD to drop CoS 0 through 5 when the queue is 60% full. In addition, multiple thresholds and levels can be set on a per queue basis.

  Jumbo Frame Support

  The Cisco StackWise technology supports granular jumbo frames up to 9 KB on the 10/100/1000 copper ports for Layer 2 forwarding. Layer 3 forwarding of jumbo packets is not supported by the Cisco Catalyst 3750. However, the Cisco Catalyst 3750-E and Catalyst 3750-X. do support Layer 3 jumbo frame forwarding.

  Smart VLANs

  VLAN operation is the same as multicast operation. If the master detects information that is destined for multiple VLANs, it creates one copy of the packet with many destination addresses. This enables the most effective use of the stack interconnect (Figure 8).

  Figure 8. Smart VLAN Operations

  

  Cross-Stack EtherChannel Connections

  Because all the ports in a stack behave as one logical unit, EtherChannel technology can operate across multiple physical devices in the stack. Cisco IOS Software can aggregate up to eight separate physical ports from any switches in the stack into one logical channel uplink. Up to 48 EtherChannel groups are supported on a stack.

  StackWise Plus

  StackWise Plus is an evolution of StackWise. StackWise Plus is only supported on the Cisco Catalyst 3750-E and Catalyst 3750-X switch families. The two main differences between StackWise Plus and StackWise are as follows:

  1. For unicast packets, StackWise Plus supports destination striping, unlike StackWise support of source stripping. Figure 9 shows a packet is being sent from Switch 1 to Switch 2. StackWise uses source stripping and StackWise Plus uses destination stripping. Source stripping means that when a packet is sent on the ring, it is passed to the destination, which copies the packet, and then lets it pass all the way around the ring. Once the packet has traveled all the way around the ring and returns to the source, it is stripped off of the ring. This means bandwidth is used up all the way around the ring, even if the packet is destined for a directly attached neighbor. Destination stripping means that when the packet reaches its destination, it is removed from the ring and continues no further. This leaves the rest of the ring bandwidth free to be used. Thus, the throughput performance of the stack is multiplied to a minimum value of 64 Gbps bidirectionally. This ability to free up bandwidth is sometimes referred to as spatial reuse. Note: even in StackWise Plus broadcast and multicast packets must use source stripping, because the packet may have multiple targets on the stack.

  Figure 9. Stripping

  

  2. StackWise Plus can locally switch. StackWise cannot. Furthermore, in StackWise, since there is no local switching and since there is source stripping, even locally destined packets must traverse the entire stack ring. (See Figure 10.)

  Figure 10. Switching

  

  3. StackWise Plus will support up to 2 line rate 10 Gigabit Ethernet ports per Cisco Catalyst 3750-E.

  Combining StackWise Plus and StackWise in a Single Stack

  Cisco Catalyst 3750-E and Catalyst 3750-X StackWise Plus and Cisco Catalyst 3750 StackWise switches can be combined in the same stack. When this happens, the Cisco Catalyst 3750-E, or Catalyst 3750-Xswitches negotiate from StackWise Plus mode down to StackWise mode. That is, they no longer perform destination stripping. However, the Cisco Catalyst 3750-E and the Catalyst 3750-X will retain its ability to perform local switching.

  Management

  Products using the Cisco StackWise and StackWise Plus technologies can be managed by the CLI or by network management packages. Cisco Cluster Management Suite (CMS) Software has been developed specifically for management of Cisco stackable switches. Special wizards for stack units in Cisco CMS Software allow the network manager to configure all the ports in a stack with the same profile. Predefined wizards for data, voice, video, multicast, security, and inter-VLAN routing functions allow the network manager to set all the port configurations at once.

  The Cisco StackWise and StackWise Plus technologies are also manageable by CiscoWorks.

  Summary

  Cisco StackWise and StackWise Plus technologies allow you to increase the resiliency and the versatility of your network edge to accommodate evolution for speed and converged applications. 

  Read more »

• Compact Optical Splitter Module for PON Architecture FTTH Deployment

  Feb 8, 2016 by Articles / 612 Views

   

  Passive Optical Network (PON) system has expanded extensively as an optical network in the construction of Fiber To The Home (FTTH) economically. To allow multiple users to share an optical fiber in a PON, the Optical Splitter that branches an optical signal is indispensable. Recently, plug-and-play structures that make use of modules and connectors are desired to simplify the installation construction of optical splitters. Moreover, because the splitter module is installed in the outside plant, high reliability that can endure harsh environmental conditions is a critical requirement. In addition, compactness and cost savings are also important considerations. Therefore, we have developed it by economically using a superior flame-retardant plasticresin for the module case. We have confirmed that the optical splitter modules have excellent optical characteristics and sufficient reliability.

  
  

  1. Introduction of Optical Splitter Modules

  PON system has expanded extensively as an optical network in the construction of FTTH economically. As shown in Fig. 1, PON architecture allows a signal transmitted over a single optical fiber from the telephone exchange office to be shared with multiple users, hence achieving cost reduction per subscriber. Planar Lightwave Circuit (PLC) splitter, an optical splitter is a key to realize the branching of optical signal in the telecommunication network, and currently has a maximum of 32 split ratio capability.

  

  Installation of optical splitter is simplified with the application of latch-on or snap method that can expedite the process with quick plug-in action. This plug-and-play method is commonly applied at the interconnection points in the FTTH network (This method enables field installation of optical components without any special tools or skills in managing bare optical fibers). To effectively deploy with such simple techniques and modular designs, connectorized components are essential to be integrated in the structure design of optical splitters. In addition, flexibility of network is achieved with the application of module terminated with connector cord, which allows easy reconfiguration of the network. Furthermore, in the FTTH PON architecture, the function of Fiber Distribution Hub (FDH) is to house optical splitter outdoor, therefore the FDH is critical in ensuring high reliability against environmental factors. Due to the space constraint in the FDH, down-sizing of optical splitter module design is done. The pervasive FTTH deployment worldwide has been called for an imminent need to develop low-cost solutions. The newly developed small sized and lightweight optical splitter is made from retardant plastic resin with sturdiness comparable to the conventional metal packaging in withstanding outdoor environmental conditions, but at a fraction of its original cost. This article illustrates the development of 1×16, 1×32 and 2×32 Wavelength Division Multiplexing (WDM) optical splitter module. The characteristics and reliability evaluation will also be discussed in this article.

  2. Structure of Optical Splitter Modules

  2.1. PLC-Type Splitter

  As shown in Fig. 2, the optical fiber is being branched to 32 outputs through a 1×32 PLC-type optical splitter. PLC chip is a silica glass embedded with optical wave circuit. The circuit pattern is designed to branch a single input into multiple output channels. Optical fiber is adhered to PLC chip with resin curedby ultraviolet exposure; this interface conforms to Telcordia GR-1209 and GR-1221 test conditions, hence good reliability is ensured. Furthermore, inorder to actualize the size reduction, bend insensitive Single Mode Fiber (SMF) has been introduced into this module.

  

  2.2. Flame Retardant Plastic Package

  The structure of optical splitter module developed is shown in Fig. 3. Bend insensitive fiber with bending radius of 15 mm is applied to the optical splitter module to achieve a considerable size reduction of the packed module. The overall dimension of L118mm×D87 mm×H13 mm is 3/5 of the size of the conventional optical module utilizing SMF of bending radius 30 mm. In addition, as a flame retardant plastic resin has replaced metallic materialin the splitter packaging, the weight decreases to 1/3 of the conventional metallic packaging version.

  

  Figure 4 illustrates the internal configuration of the optical splitter module. The splitter module is terminated with optical connector pigtails. The 2 mm fiber cords are fixed onto the cable retainer with adhesive.This structure is designed to withstand tensile strength of maximum 68.6 N. Moreover, as the optical cord has a similar structure to the loose tube cables, allowing the optical fiber free movement within the cord effects the expansion and contraction of the optical cord that will not exert any external tension onto the fiber.

  

  The structure of strain relief boot is shown in Fig.5. The boot is designed to control the bending radius to a minimum of optical fiber limit, i.e., 15 mm. This prevents an increase in attenuation brought upon by fiber bend. The flexible boot developed has taken factors like hardness, thickness and the quantity of cord per boot into the design considerations to control the bending radius to a minimum of 15 mm when a loadis applied at 90° bend to the optical cord perpendicularly.

  

  3. OPTICAL PERFORMANCE AND CHARACTERISTIC

  3.1. Functionality of FDH

  Figure 6 captures the appearance of FDH system in configuration with optical splitter module load. The hub, optical connector, and optical adapters are all mounted onto a panel to enable ease of operation with a latch mechanism. The pigtail is elegantly managed in a U-shape through the mandrel. This plug-and-play method makes installation extremely simple and efficient.

  

  3.2. Fundamental Optical Characteristics

  The 1×16 and 1×32 splitter modules were fabricated to be mountable onto the above described fiber distribution hub. The vacant port (a port which is not in service) present in the FDH will result in back reflections of the optical signal. To prevent return loss from the end face of vacant port, SC connector is polished to an Angled Physical Contact (APC) interface. Data below tabulates the optical characteristics of the optical splitter module, inclusive of the connector pigtails.

  The histograms shown in Figs. 7 and 8 illustratethe insertion loss performance of 1×16 and 1×32 optical splitter module respectively. At operating wavelength 1310 nm, the average insertion loss of 1×16 splitter stands at 13.23 dB while that of 1×32 splitter is 16.33 dB. Similarly, at 1550 nm operation wavelength, the insertion loss of 1×16 and 1×32 splitter module is 13.10 dB and 16.22 dB respectively. In addition, the standard deviation of 1×16 splitter is 0.29 dB while 1×32 splitter yields a standard deviation of 0.34dB. At the same time, this value decreases to 0.23 dB for 1×16 splitter and 0.28 dB for the 1×32 splitter at wavelength 1550 nm.

  

  The performances of other optical characteristics apart from insertion loss are shown in Table 1. These results show consistent good performances, as exhibited in the insertion loss histogram, in characteristics including uniformity, return loss and PDL values.

  

  3.3. Temperature dependent loss

  History from past experimental results has shown that components terminated with optical pigtail cord are susceptible to insertion loss fluctuation with temperature change. To isolate the effects of cordage expansion/contraction on the optical fiber within, the optical cord is designed to allow free movement of optical fiber, thus eliminating the external stress fromthe expansion/contraction of the cord. Figure 9 depicts the insertion loss variation of the 1×32 optical splitter module during temperature cycling from −40 °C to +85 °C. The average, minimum, and maximum values obtained from the 32 output ports are illustrated in the graph shown in Fig. 9. From the graph, the maximum loss deviation between the ports with maximum and minimum insertion loss is 0.17 dB. This result has an evident exceptional stability of the optical splitter module that is developed.

  

  3.4. Wavelength dependent loss

  The wavelength dependent loss of the 1×32 optical splitter module is shown in Fig. 10. The performances of insertion losses over wavelengths from 1260 nm to 1680 nm are measured. Again, the average loss from 32 ports and minimum and maximum wavelength dependent losses are illustrated in the graph. The average deviation is 0.36 dB while the maximum deviation from all the 32 ports is 0.86 dB.

  

  This proves that the splitter module has shown resilience in insertion loss variation over a broad spectrum of wavelength.

  A variety of optical devices are stored in this optical splitter module, making it multifunctional. An example is the 2×32 WDM optical splitter module shown in Fig. 11 and the structure of its cable retainer in Fig.12. A WDM filter was built in front of a 1×32 splitter module, enabling the structure to have multiple wavelengths.

  

  Figure 13 shows the wavelength dependent loss of the 2×32 WDM optical splitter module. With the WDM filter, the wavelength ranging from 1530nm to1570nm are transmitted from the B port, and the other wavelength ranges are transmitted from the A port. The wavelength dependent loss of A port and B port are split evenly among the 32 fibers, hence excellent loss performance is obtained in each port.

  

  4. Reliability of Optical Splitter Modules

  The reliability of 1×32 splitter module is evaluated in accordance to test procedures stipulated in the Telcordia GR-1209 and GR-1221. The test conditions and the results of the 1×32 splitter module measured at 1550 nm are shown in Table 2. The average, maximum, and minimum values of 32 output ports measured are recorded in Table 2. The results of side pulltest and cable retention test are maximum in-situ datamonitored during load application onto the cable cord. On the other hand, the recorded data of damp heat, temperature cycling, mechanical shock, vibration, and water immersion shows the variation of insertion loss before and after the test conditions. From the results, it is confirmed about the reliability of 1×32 splitter module.

  

  The results of high temperature and humidity test are depicted in Fig. 14. The optical splitter samples underwent a total of 2000 hours of storage at 85 °C and of 85% relative humidity. Insertion loss data at 100 hrs, 168 hrs, 500 hrs, 1000 hrs, and 2000 hrs juncture were measured. The average insertion loss of the 32 ports, maximum and minimum insertion loss measured at 1550 nm are displayed in the graph. From the graph in Fig. 14, it is concluded that there is very minimal loss variation even after 2000 hrs. The optical splitter module has shown good stability when exposed to high temperature and humidity conditions.

  

  Furthermore, to meet the flame retardant requirements for optical components and accessories, we have applied frame retardant plastic material of 1.5 mm thickness complying to UL-94 V-0. On the same note, the jacket of optical fiber cord is made of grade V-0 flame retardant PVC.

  5. Conclusion

  A compact and economical optical splitter that boasts of superior optical performance and reliability against stringent environmental conditions suited for outdoor installation has been successfully developed. This plug-and-play design for installation of the above optical splitter has enabled simple and speedy installation, at the same time provided added flexibility for future network reconfigurations, thus making this optical splitter module the perfect solution for PON architecture FTTH deployment.

   

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• Qualcomm goes big on wifi and IoT with multiple chip launches

  Jun 1, 2016 by Telecom News / 590 Views

  By Tim Skinner        telecoms.com

  

  Qualcomm has announced new chips and technologies designed to boost domestic wifi coverage, at-home IoT connectivity, wearable tech capability and next generation broadband delivery.

  Starting off with domestic wifi coverage boosting, and Qualcomm launched a new family of 802.11ac platforms designed to optimise device wifi usage by intelligently allocating radio spectrum in the home. It says its new three radio solutions combine two 5 GHz radios and a 2.4 GHz radio to help improve connectivity; and its platform, used on new routers and repeaters, can appropriately dedicate radio in the legacy 2.4 GHz band to devices only compatible with the 802.11n standard. This, in theory, can alleviate congestion on domestic networks and ensure more bandwidth availability for devices compatible with the newer 802.11.ac band.

  Qualcomm says the self-organising features integrated into the new platform means it will become much easier to register and configure new devices on the network; while automatically allocating capacity for devices based on real-time conditions.

  “As people rely on their home network to support more devices accessing the internet and streaming media, Wi-Fi is being stretched to the limit,” said Gopi Sirineni, vice president of product management, Qualcomm Atheros, Inc. “We are changing the game with features designed to deliver the best possible Wi-Fi experiences and now, uniquely, we are driving those technologies into more cost-effective products to extend the benefits to a wider swath of consumers.”

  IoT is also in Qualcomm’s sights, as it unveiled a new chip set targeting low-power smart home devices. It says the QCA4012 chip brings dual band wifi, enhanced security, low power and small form factor for connected devices. Companion SDKs and services from partners Ayla, Exosite and Iota Labs include API interfaces and other tools to support IoT device and cloud integration.

  “IOTA Labs has developed cutting edge IoT solutions integrating Qualcomm Technologies’ latest products with the IOTA Labs platform,” said Amit Singh, director and co-founder, IOTA Labs. “IOTA Labs’s leading edge IoT platform and experience acts as an accelerator for clients to transform their offerings into leading smarter products and services with a lower cost of ownership.”

  The Snapdragon Wear 1100, included in the raft of announcements, joins the product line and targets consumer-led IoT products, including smart-accessories and wearable tech. Qualcomm says it has been designed to target  the wearable segment where a smaller size, longer battery life, smarter sensing, enhanced security. It also comes with a modem capable of LTE, wifi and Bluetooth support.

  “We are delighted to add Snapdragon Wear 1100 to our Snapdragon Wear family, thus making it easier for customers to develop connected wearables with targeted use cases such as kid and elderly tracking,” said Anthony Murray, SVP of IoT for Qualcomm Technologies. “We are actively working with the broader ecosystem to accelerate wearables innovation and are excited to announce a series of customer collaborations today.”

  Finally, Qualcomm also announced a fixed networking launch which it claims will help operators deliver up to 1 Gbps data rates on existing infrastructure up to 100 meters. The GigaDSL chipsets are intended to support gigabit data rates on existing telephone lines providing a high-speed extension for VDSL without losing spectrum capacity. It says existing infrastructure can be upgraded to the new processors without having to rip up the network and start again. The product line will become available from June for both fibre to the building and customer premises equipment.

  “With these new GigaDSL product offerings, we are able to meet carriers’ broadband goals, complementing fiber deployment in time for major events, such as the 2018 Winter Games in Korea and the 2020 Summer Games in Japan,” said Irvind Ghai, VP of product management at Qualcomm Atheros.

   

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• Fiber Optic Patch Panels Tutorial

  Feb 8, 2016 by Articles / 582 Views

  What Is Fiber Optic Patch Panel?

  Fiber optic patch panel, or fiber optic patch bay, is a common cable management facilities. It includes a series of connection points of electronic equipment and the mainly connections are fiber optic patch cables. The patch panel allows circuits to be easily arranged and rearranged by simply plugging and unplugging the path cables, or changing the circuit of select signals without the use of expensive dedicated switching equipment. It can be an opened box used to protect the bare fiber and the optical fiber cables, meanwhile it protects spaces for fusion splicing and components connections by fiber adapters. During the unused condition, all fiber optic connectors, fiber patch cables and adapters should be kept away from dust. Fiber optic patch panels help with the installation density of the fiber optic cabling and provide more convenient organization and management.

  A typical fiber optic patch panel has some jacket on the front side to receive short patch cables while on the back of the panel. There are either jacks or punch down blocks that receive the connections of longer and more permanent cables. The patch panels are often used to connect several computers by linking them via the panel, which enables the LAN to connect to the Internet or another WAN.

  Types of Fiber Optic Patch Panels

  According to the installation ways, there are mainly two types of fiber optic patch panels: wall-mounted patch panels and rack-mounted patch panels.

  Wall-Mounted Fiber Optic Patch Panel Wall-mounted fiber optic patch panels basically keep 12 different fibers separated from one another. If the amount of the fiber is more than 12, the extra fibers can be moved to a second panel or an engineer can use a panel that is designed to hold more fibers separately. The wall-mounted patch panels can be constructed to hold up to 144 fibers at once. Wall-mounted fiber optic patch panels use the inside fiber optic adapters panels, patch cables and pigtails to realize the function of optical fiber distribution. They are used for protective connections for the fiber cables and pigtails in fiber optic cabling and user terminal applications. The patch panels are installed on the indoor wall and terrace to provide a flexible fiber management system for transitional outside plant cable to inside cable and connector assemblies.

   

  Rack-Mounted Fiber Optic Patch Panel Rack-mounted fiber optic patch panels hold the fibers horizontally and are often designed to open like a drawer. The sliding-opened structure offers engineers an easy access to the optical fibers inside. The rack-mounted patch panels are optional with different kinds of fiber optic adapter ports and pre-installed inner trays and accessories. And fiber optic pigtails of different types are optional, such as SC, FC, ST, LC, E2000 etc. Also, rack-mounted patch panels can be customized by the quantity of optical fibers. Rack-mounted fiber patch panels are used to terminated and distributed optical fiber cables. They are convenient to organize and connect the fiber optic links. These patch panels are applied to many fiber optic products, such as DWDM MUX DEMUX, Rack Chassis Splitter, Optical Distribution Frame(ODF) etc. They are fully stable with no risk of movement and offer secure environment for fiber optic adapters, patch cables and pigtails.

   

  According to different applications, fiber optic patch panels can be classified as following:

  Loaded Fiber Optic Patch Panel Loaded fiber optic patch panels are usually designed for fitting on a standard 19" rack and can provide the best protection for fiber optic applications. There are rubber grommets on the back of loaded fiber optic patch panels to protect the fiber cables from damage. Each loaded patch panel has fiber splice trays and cable routing spools. What's more, it includes zip ties, cable routing clamps and mounting screws, fiber splice sleeves and installation instructions. There is a special black textured which can be installed a sleek look in the server rack of these loaded fiber patch panels.

   

  Swing-Out Fiber Optic Patch Panel Swing-out fiber optic patch panels are lightweight and robust patch panels. They are designed for the installation of up to 48 standard optical fibers. These patch panels offer an economic alternative to metal fiber enclosures. The lower tray is designed to gain access to preformed fiber and splice management areas, at the same time, make it easy for installation and dressing of fiber optic cables. All common adapter panel/plate types, includes LC, SC, and ST can be changed with the front plates that can accommodate 6 or 12 duplex, or 12 simplex adapters each.

   

  Fixed Fiber Optic Patch Panel Fixed fiber optic patch panels are 19" rack-mountable for connecting up to 24 optical fibers. They are suitable for use with manufactured pigtails or field installation connectors. The installation size is adapted by using appropriate mounting brackets, while the chassis will not be changed. Fixed patch panels are easy to use and more artistic while they can also keep rugged design. These patch panels are easier to terminate, providing greater capacity and easier fiber cable managements. Generally, fixed rack-mounted patch panels do not slide out, but we do offer sliding patch panels for even quicker access to the fiber terminations.

   

  Slide-Out Fiber Optic Patch Panel Slide out fiber optic patch panels fit with standard 19" or 23" racks and are designed to support both patching and splicing in one unit. Each slide-out patch panel has a slide-out master panel with an integrated tray stop to prevent over extension of fiber cables. The slide-out patch panel also has a two-piece top and swell latch door to allow for easy access to the adapter panels.

   

  High-Density Fiber Optic Patch Panel High-density fiber optic patch panels have been engineered to be able to significantly increase density for both patching and splicing. High-density patch panels maximize the amount of adapter panels per rack unit of height, so by utilizing LC quad style adapters you can effectively terminate up to 96 fibers per rack unit of space. There are several other features that make a high density fiber patch panel in an exceptionally nice product to work with. The sliding tray has locking positions to prevent over-extending the fibers. High-density patch panels also have a split top design which allows for easier cable management, and improved strain relief for the cable ingress.

   

  Fiber Optic Patch and Splice Combos Patch Panel Fiber optic patch and splice combos patch panels fit with standard 19" or 23" racks and are designed to support both patching and splicing in one unit. Fiber patch and splice combos have to support termination panels in an upper slide-out shelf with a lower compartment for splice trays in a slide-out shelf. This allows for a full front access application. Blank panels are available to fill unused panel positions.

   

  Signature Series Patch Panel The Signature Series fiber patch panel offers a solution in which you can adapt the fiber patch panel to many fiber adapter panels or fiber module footprints you want in a way that has never been offered before. This new fiber patch panel series is engineered to allow adaptation to a wide variety of fiber patching applications as well as fiber module installations, including a bulkhead that fits Corning adapter plates. You can now adjust to any of these scenarios with just a simple swap of the fiber bulkhead bracket. The unique master panel design allows for easy and secure routing of fiber without obstructions or compromising your bend radius.

   

  LGX Fiber Optic Patch Panel LGX fiber optic patch panels are rack-mountable patch panels designed to support the storage of splice trays. They provide high-density fiber connectivity solutions. LGX patch panels have universal mounting hardware to hold fully terminated LGX cassettes. This maximizes the performance of networking space while saving valuable installation time.

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• The Composition and Classification of Fiber Optic Cables

  Feb 6, 2016 by Articles / 569 Views

  To satisfy optical, mechanical and environmental performances and specifications, fiber optic cable was born. The fiber optic cable uses one or more fibers that placed in the sheath as the transmission medium. Accompanied by the continuous advancement of network technology, fiber optic cable constantly participates in the construction of telecommunications networks, the construction of the national information highway, Fiber To The Home (FTTH) and other occasions for large-scale use. Although fiber optic cable is still more expensive than other types of cable, it's favored for today's high-speed data communications because it eliminates the problems of twisted-pair cable and so fiber optic cable is still a good choice for people. But how to really get a good performance, state-of-the-art products, we need to understand some basics to identify the types of fiber optic cables.

  Composition

  Fiber optic cable consists of the core, the cladding and the coating. The core is a cylindrical rod of dielectric material. Dielectric material conducts no electricity. Light propagates mainly along the core of the fiber. The core is generally made of glass. The core is described as having a radius of (a) and an index of refraction n1. The core is surrounded by a layer of material called the cladding. Even though light will propagate along the fiber core without the layer of cladding material, the cladding does perform some necessary functions. (The basic structure of an optical fiber is shown in the following figure.)

   

  Structure: Core: This central section, made of silica, is the light transmitting region of the fiber.Cladding: It is the first layer around the core. It is also made of silica, but not with the same composition as the core. This creates an optical wave guide which confines the light in the core by total reflection at the core-cladding interface.Coating: It is the first non-optical layer around the cladding. The coating typically consists of one or more layers of a polymer that protect the silica structure against physical or environmental damage.Strengthening Fibers: These components help protect the core against crushing forces and excessive tension during installation. The materials can range from Kevlar to wire strands to gel-filled sleeves.Cable Jacket: This is the outer layer of any cable. Most fiber optic cables have an orange jacket, although some may be black or yellow. The jacket material is application specific. The cable jacket material determines the mechanical robustness, aging due to UV radiation, oil resistance, etc.

   

  Jacket Material: PolyEthylene (PE): PE (black color) is the standard jacket material for outdoor fiber optic cables. PE has excellent moisture- and weather-resistance properties. It has very stable dielectric properties over a wide temperature range. It is also abrasion-resistant.PolyVinyl Chloride (PVC): PVC is the most common material for indoor cables, however it can also be used for outdoor cables. It is flexible and fire-retardant. PVC is more expensive than PE.PolyVinyl DiFluoride (PVDF): PVDF is used for plenum cables because it has better fire-retardant properties than PE and produces little smoke.Low Smoke Zero Halogen (LSZH) Plastics: LSZH plastics are used for a special kind of cable called LSZH cables. They produce little smoke and no toxic halogen compounds. But they are the most expensive jacket material. 

   

  Fiber Size

  The size of the optical fiber is commonly referred to by the outer diameter of its core, cladding and coating. Example: 50/125/250 indicates a fiber with a core of 50 microns, cladding of 125 microns, and a coating of 250 microns. The coating is always removed when joining or connecting fibers. A micron (µm) is equal to one-millionth of a meter. 25 microns are equal to 0.0025 cm. (A sheet of paper is approximately 25 microns thick).

   

  Classification

  Besides the basics, Fiber optic cables can be classified by other ways.

  Transmission Mode:

  • Multi-Mode Fiber (MMF) Cable: Center glass core is coarse (50 or 62.5 µm). It can transmit a variety of patterns of light. However, because its dispersion is large, which limits the frequency of the transmitted digital signal, and with increasing distance, the situation will be more serious. For example, 600Mb/km of 2km fibers provide the bandwidth of only 300 Mbps. Therefore, MMF cable's transmission distance is relatively short, generally only a few kilometers. General MMF patch cables are in orange, also some are gray, joints and protection are beige or black. 
  • Single-Mode Fiber SMF Cable: Center glass core is relatively fine (core diameter is generally 9 or 10 µm), only one mode of light transmission. Therefore, the dispersion is very small, suitable for remote communication, but it plays a major role in the chromatic dispersion, so that SMF cable has a higher stability requirement to the spectral width of the light source, just as narrower spectrum width, better stability. General SMF patch cables are in yellow, with joints and cases in blue.

   

  Transmission Way:

  • Simplex Cable: Single strand of fiber surrounded by a 900µm buffer then a layer of Kevlar and finally the outer jacket. Available in 2 mm or 3 mm and plenum or riser jacket. Plenum is stronger and made to share in fire versus riser is made to melt in fire. Riser cable is more flexible.
  • Duplex Cable: Two single strands of fiber optic cable attached at the center. Surrounded by a 900µm buffer then a layer of Kevlar and finally the outer jacket. In data communications, the simultaneous operation of a circuit in both directions is known as full duplex; if only one transmitter can send at a time, the system is called half duplex.

   

  Cable Core Structure:

  • Central Tube Cable: Fiber, optical fiber bundles or fiber optic cable with no stranding directly into the center position.
  • Stranded Tube Cable: A few dozens or more root fiber or fiber tape unit helically stranded around the central strength member (S twist or SZ twisted) into one or more layers of fiber optic cable.
  • Skeleton After Tube Cable: Fiber or fiber after spiral twisted placed into the plastic skeleton cable slot.

   

  Fiber Road Laying:

  • Aerial Cable: Aerial cables are for outside installation on poles. They can be lashed to a messenger or another cable (common in CATV) or have metal or aramid strength members to make them self supporting. The cable shown has a steel messenger for support. It must be grounded properly. A widely used aerial cable is optical power ground wire which is a high voltage distribution cable with fiber in the center. The fiber is not affected by the electrical fields and the utility installing it gets fibers for grid management and communications. This cable is usually installed on the top of high voltage towers but brought to ground level for splicing or termination. 
  • Direct-Buried Cables:
    • Armored Cable: Armored cable is used in direct-buried outside plant applications where a rugged cable is needed and/or rodent resistance. Armored cable withstands crush loads well, needed for direct burial applications. Cable installed by direct burial in areas where rodents are a problem usually have metal armoring between two jackets to prevent rodent penetration. Another application for armored cable is in data centers, where cables are installed underfloor and one worries about the fiber cable being crushed. Armored cable is conductive, so it must be grounded properly. 
    • Breakout Cable: Breakout cable is a favorite where rugged cables are desirable or direct termination without junction boxes, patch panels or other hardware is needed. It is made of several simplex cables bundled together inside a common jacket. It has a strong, rugged design, but is larger and more expensive than the distribution cables. It is suitable for conduit runs, riser and plenum applications. It's perfect for industrial applications where ruggedness is needed. Because each fiber is individually reinforced, this design allows for quick termination to connectors and does not require patch panels or boxes. Breakout cable can be more economic where fiber count is not too large and distances are not too long, because it requires so much less labor to terminate.
  • Submarine Cable: Submarine cable is the cable wrapped with insulating materials, laying at the bottom of the sea, to set up a telecom transmission between countries.

   

  Cable State. Based on 900µm tight buffered fiber and 250µm coated fiber there are two basic types of fiber optic cable constructions:

  • Tight Buffered Cable: Multiple color coded 900µm tight buffered fibers can be packed tightly together in a compact cable structure, an approach widely used indoors, these cables are called tight buffered cables. Tight buffered cables are used to connect outside plant cables to terminal equipment, and also for linking various devices in a premises network. Multi-fiber tight buffered cables often are used for intra-building, risers, general building and plenum applications. Tight buffered cables are mostly built for indoor applications, although some tight buffered cables have been built for outdoor applications too.
  • Loose Tube Cable: On the other hand multiple (up to 12) 250µm coated fibers (bare fibers) can be put inside a color coded, flexible plastic tube, which usually is filled with a gel compound that prevents moisture from seeping through the hollow tube. Buffer tubes are stranded around a dielectric or steel central member. Aramid yarn are used as primary strength member. Then an outer polyethylene jacket is extruded over the core. These cables are called loose tube cables. Loose tube structure isolates the fibers from the cable structure. This is a big advantage in handling thermal and other stresses encountered outdoors, which is why most loose tube fiber optic cables are built for outdoor applications. Loose-tube cables typically are used for outside-plant installation in aerial, duct and direct-buried applications. 

   

  Environment & Situation:

  • Indoor Cable: Such as distribution cables. Distribution cable is the most popular indoor cable, as it is small in size and light in weight. They contain several tight-buffered fibers bundled under the same jacket with Kevlar strength members and sometimes fiberglass rod reinforcement to stiffen the cable and prevent kinking. These cables are small in size, and used for short, dry conduit runs, riser and plenum applications. The fibers are double buffered and can be directly terminated, but because their fibers are not individually reinforced, these cables need to be broken out with a "breakout box" or terminated inside a patch panel or junction box to protect individual fibers.
  • Outdoor Cable: Outdoor fiber cable delivers outstanding audio, video, telephony and data signal performance for educational, corporate and government campus applications. With a low bending radius and lightweight feature, this cable is suitable for both indoor and outdoor installations. These are available in a variety of configurations and jacket types to cover riser and plenum requirements for indoor cables and the ability to be run in duct, direct buried, or aerial/lashed in the outside plant.

  To purchase your fiber cables, please click link below:

  Fiber Patch Cables

   

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