How to Overcome the Challenges of Adopting WDM-PON in FTTx?


The bandwidth demand in the access network has been increasing rapidly over the past several years. Passive optical networks (PONs), as the most economical FTTx architecture that needs no power supply, have evolved to provide much higher bandwidth in the access network. A PON is a point-to-multipoint optical network, where an optical line terminal (OLT) at the central office (CO) is connected to many optical network units (ONUs) at remote nodes through one or multiple 1:N optical splitters. WDM-PON combines the virtues of point-to-point dedicated connections with the fiber efficiency and economics of PON, which is considered as a candidate solution for FTTx network. This article offers solutions for deploying WDM-PON in regard to its cost and technical challenges

WDM-PON Technology Explanation

WDM-PON is the passive optical network (PON) based on wavelength division multiplexing (WDM) technology, which delivers higher network security. This system allows ONUs to have light sources at different tuned wavelengths coexisting in the same fiber, increasing the total network bandwidth and the number of users served in the optical access network. The CO contains multiple transceivers at different wavelengths with each output wavelength creating a dedicated path or channel for a particular user by passing through a wavelength selective/dependent element at the remote node (RN). Wavelength selection can also be achieved by filtering at the user. The upstream connection similarly utilizes a dedicated wavelength channel.

WDM-PON system

Why Apply WDM-PON in FTTx Networks?

We have known that WDM-PON supplies each subscriber with a wavelength instead of sharing wavelength among 32 or even more subscribers in TDM PON, thus providing higher bandwidth provisioning. WDM-PON is regarded as a candidate solution for next-generation PON systems in competition with TDM PON for possessing the following advantages:

  • WDM-PON allows each user being dedicated with one or more wavelengths, thus allowing each subscriber to access the full bandwidth accommodated by the wavelengths.
  • WDM-PON networks typically provide better security and scalability because each home only receives its own wavelength.
  • The MAC layer control in WDM-PON is more simplified as compared to TDM PON because WDM-PON provides P2P connections between the OLT and the ONU, and does not require the point-to-multipoint (P2MP) media access controllers found in other PON networks.
  • Wavelength in a WDM-PON network is effectively a P2P link, thus allowing each link to run at a different speed and with a different protocol for maximum flexibility and pay-as-you-grow upgrades.
WDM-PON Challenges: How to Deal with Them?

Despite these attractive features, there are also some demerits that hinder the implementation of WDM-PON networks.

  1. When implementing WDM-PON, one should apply wavelength routers or power splitters in the ONUs, and both of the methods need a colorless ONU.
  2. As for long reach WDM-PON system, the protection is necessary to ensure the network reliability and performance.

Concerning the challenges that remain in WDM-PON deployment, here we provide some solutions for your reference.

For Colorless ONU

The ONUs in WDM-PON need to be colorless, which means no ONU is wavelength specific in order to reduce the costs of operation, administration, maintenance and production. Local emission is proposed to solve this problem. There basically exist two local emission approaches: wavelength tuning and spectrum slicing. The ONU of the wavelength tuning approach consists of a tunable laser diode (TLD) as a transmitter (Tx), an optical receiver (Rx) with wavelength selector (WS), and a WDM coupler that divides or combines the upstream and downstream signals. The configuration of the ONU in the spectrum slicing approach is similar to that of wavelength tuning approach, except that a broadband light source (BLS) with WS is used instead of the TLD.

colorless ONUs for WDM-PON

For Long-Reach Protection

As for long-reach network, protecting the feeder fiber that transmits data from potential damage is vital. Then how to achieve the protection? It is suggested to adopt 3-dB optical couplers, which can be used to split or combine the path of WDM signals to or from both the working and protection fibers in the OLT or in the wavelength router. Note that the OLT and the wavelength router are typically located in the central office (CO) and in the access node (AN) respectively. However, this protection method has a low loss budget because of the adoption of the 3-dB optical couplers. To this end, a wavelength-shifted protection scheme has been proposed, which is deploying the cyclic property of the 2×N athermal arrayed-waveguide grating (AWG) and two wavelength allocations for working and protection. In this case, 3-dB optical couplers are not needed.


WDM-PON is proving to be the most promising long-term, scalable solution for delivering high bandwidth to the end user. Meanwhile, advances in key device technologies had laid the foundation for realization of a high performance, low cost WDM based PON system. Thus, in competition with other high-speed access network technologies, WDM-PON is considered the most favorable for the required bandwidth in the near future.

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How Does Erbium Doped Fiber Amplifier (EDFA) Benefit WDM Systems

Optical network that involves WDM (wavelength division multiplexing) currently gains in much popularity in existing telecom infrastructure. Which is expected to play a significant role in next generation networks to support various services with very different requirement. WDM technology, together with EDFA (Erbium Doped Fiber Amplifier), allowing the transmission of multiple channels over the same fiber, that makes it possible to transmit many terabits of data over distances from a few hundred kilometers to transoceanic distances, which satisfy the data capacity required for current and future communication networks. This article explains how can WDM system benefit from this technology.

Basics of EDFA

The key feature of EDFA technology is the Erbium Doped Fiber (EDF), which is a conventional silica fiber doped with erbium. Basically, EDFA consists of a length of EDF, a pump laser, and a WDM combiner. The WDM combiner is for combining the signal and pump wavelength, so that they can propagate simultaneously through the EDF. EDFA can be designed that pump energy propagates in the same direction as the signal (forward pumping), the opposite direction to the signal (backward pumping), or both direction together. The pump energy may either by 980nm pump energy or 1480nm pump energy, or a combination of both. The most common configuration is the forward pumping configuration using 980nm pump energy. Because this configuration takes advantage of the 980nm semiconductor pump laser diodes, which feature effective cost, reliability and low power consumption. Thus providing the best overall design in regard to performance and cost trade-offs.

basic EDFA design

Why EDFA Is Essential to WDM Systems?

We know that when transmitting over long distance, the signal is highly attenuated. Therefore it is essential to implement an optical signal amplification to restore the optical power budget. This is what EDFA commonly used for: it is designed to directly amplify any input optical signal, which hence eliminates the need to firstly transform it to an electronic signal. It simply can amplify all WDM channels together. Nowadays, EDFA rises as a preferable option for signal amplification method for WDM systems, owing to its low-noise and insensitive to signal polarization. Besides, EDFA deployment is relatively easier to realize compared with other signal amplification methods.

4-Channel WDM System With or Without EDFA: What Is the Difference?

Two basic configurations of WDM systems come in two forms: WDM system with or without EDFA. Let’s first see the configuration of WDM system without using it. At the transmitter end, channels are combined in an optical combiner. And these combined multiple channels are transmitted over a single fiber. Then splitters are used to split the signal into two parts, one passes through the optical spectrum analyzer for signal’s analysis. And other passes through the photo detector to convert the optical signal into electrical. Then filter and electrical scope is used to observe the characteristics of signal. In this configuration signals at long distance get attenuated. While this problem can be overcome by using erbium doped fiber amplifier.

WDM system without EDFA

As for WDM system which uses EDFA, things are a little bit different. Although the configuration is almost the same as WDM system without it, some additional components are used. These components are EDFAs which are used as a booster and pre-amplifier, and another additional component is optical filter. With the adoption of optical amplifier, this system doesn’t suffer from losses and attenuation. Hence, it is possible to build broadband WDM EDFA which offer flat gain over a large dynamic gain range, low noise, high saturation output power and stable operation with excellent transient suppression. The combination provides reliable performance and relatively low cost, which makes EDFAs preferable in most applications of modern optical networks.

WDM system with EDFA


Among the various technologies available for optical amplifiers, EDFA technology proves to be the most advanced one that holds the dominate position in the market. In future, the WDM system integrated with high performance EDFA, as well as the demand for more bandwidth at lower costs have made optical networking an attractive solution for advanced networks.

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CWDM and DWDM for Metro Networks: How to Make it Economical?

Fiber exhaust still appears to be a common problem faced by most metro (or metropolitan) networks. Although the cost of fiber optic cable is consistently dropping, the trenching, labor, and other installation costs towards optical fiber stay rather high. This may partially explain why an increasing number of metro networks incline to adopt WDM technology to enhance fiber capacity. It is known that WDM technology used in metro networks generally takes two forms: coarse WDM (CWDM) and dense WDM (DWDM). This article will deliver an overall comparison of CWDM and DWDM in metro networks, from the perspective of the roles each plays and the operating cost. Help you to decide how to reach an economical solution.


CWDM vs. DWDM: Different Role in Metro Network

As for the major difference between the two WDM technology, their names imply it all: is the channel spacing within the window of the optical spectrum (see the picture below). CWDM has a wider pass-band that spaced at 20 nm apart, which allows for the use of less expensive components like uncooled lasers and thin-film filter technology. The cost advantage of CWDM makes it a more appropriate alternative for the shorter distance typically found in metro access networks.


However, metro networks sometimes demand for longer distance and more wavelengths that CWDM simply cannot satisfy, then DWDM with its narrow channel spacing (0.8 nm) should be put into use. The problem is that the components related to the latter are too expensive for some edge networks. In this case, the best solution is to combine both CWDM and DWDM in metro area networks.


CWDM in the Metro Access

CWDM nowadays commonly supports at least eight of the eighteen ITU-T G.694.2 defined channels over distances of up to 80 km. With simple point-to-point and ring network topology, CWDM eliminates the need for erbium doped-fiber amplifier (EDFA) typically associated with DWDM. CWDM’s lower cost and small footprint fit well with customer premises and co-location installations. And due to the readily available of Gigabit interface converters and small form factor pluggable (SFP) transceivers for CWDM platform, it gains in much popularity in enterprise and storage networks. CWDM is most fit in networks with the following features:

  • Low channel count of 4 to 8 channels
  • Transmission rates of <2.5 Gbits/sec per channel, and short distances of <80 km
DWDM in the Metro Core

Carriers are consistently looking for a cheaper and simpler version of long-haul DWDM, which drives the equipment suppliers to adapt DWDM systems accordingly. Banded wavelength filters, elimination of dispersion compensation, and more tolerant channel spacing were seen as ways to accomplish this goal. Nowadays, DWDM is well suited to high-capacity core networks in the metro, and to regional extensions between metro areas.

Cost Concerning CWDM and DWDM

The cost is still presented as a key difference in metro network systems. DWDM lasers are generally more expensive than those applied in CWDM system, the cooled DFB lasers offer cost-effective solutions for high-capacity large metro rings. And the cost of the this system is amortized over the large number of customers served by the systems. Whereas for metro access networks that demand for lower-cost and lower-capacity systems, it heavily depends on what the customer is willing to pay for broadband service. Since a metro access application would have fewer wavelengths, so based on equipment cost, CWDM is a more profitable solution for metro access points where cost is more important than capacity.

The Future of CWDM and DWDM in Metro Network

Some vendors offering both CWDM and DWDM technologies have merged the system building blocks onto a single platform. This approach allows the de-multiplexed CWDM traffic to be directly connected to DWDM transponders, saving equipment and space. It also enables end-to-end performance monitoring and cost optimization throughout the entire metro network. Then there is no need to choose between these two WDM technologies. The better choice is an integrated solution that makes use of the economies of CWDM for shorter distances, and provides the power of a DWDM network where longer distances and more capacity are needed. The result is an integrated, economical network that doesn’t require a carrier to compromise on quality, quantity, or cost. The DWDM building blocks are shown below.

DWDM building blocks


From what we have discussed in this article, we can conclude that metro networks will benefit from the mixture of CWDM and DWDM systems. And metro networks are becoming more flexible over this converged solution: with CWDM fitting the needs of today, and DWDM for the growing demand for increased coverage in the future. Take advantage of both the coarse and dense WDM technology, this integrated metro network that delivers much reliability and flexibility is the trend of the future.

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Comparison Between CFP-100G-SR10 and CFP-100G-LR4 Module

Although 10/40G Ethernet nowadays still captures the major position in the world of telecommunication, service providers and enterprise data centers are actually undertaking a transformation of infrastructures. Which fuels the demand for higher speeds, greater scalability, and better performance and reliability, making migration to 100G network an inevitable trend. Optical transceiver modules always pertain to an integral part of overall system design, as for 100G CFP modules, the options vary widely. This article makes a comparison of the most commonly two: CFP-100G-SR10 and CFP-100G-LR4 transceiver module.

Basics of 100G CFP Transceiver Module

CFP transceiver module is a hot pluggable form factor designed for optical networking applications. CFP the acronym from 100G (here C equals 100 in Roman numerals) form factor pluggable. The name clearly indicates that CFP transceiver module is introduced typically for 100G interfaces. To make it easier to understand, let’s begin with general CFP architecture. It basically consists of two parts—electrical interface interacting with equipment, and line card interface and optical line interface.

100G CFP architecture

From equipment line card to electrical interface, CFP has several “M-Lines” with 10Gbps speed. If CFP is working 100GBase-LR4 mode, then it has 10 x 10Gbps M-Lines. As for 40GBase-LR4, it uses 4 x 10Gbps M-Lines. The so called “gear box”is electrical 10:4 mux/demux module aggregating up to 10 M-Line interfaces in maximum 4 N-Line interfaces. Each N-Line is 25Gbps for 100GBase-LR4 and 10Gbps for 40GBase-LR4. The N-Line is converted to optical signal with different wavelength and all four wavelengths are transmitted to CFP line interface using built in passive optical multiplexers.

CFP-100G-SR10 and CFP-100G-LR4 Overview

100G CFP modules offer connectivity options for a wide range of service provider transport, data center networking, and enterprise core aggregation applications. The basic information of CFP-100G-SR10 and CFP-100G-LR4 module is provided below.

CFP-100G-SR10 Module

CFP-100G-SR10 is an IEEE standardized CFP module supporting link lengths of 100 m and 150 m respectively on laser-optimized OM3 and OM4 multifiber cables. It primarily enables high-bandwidth 100-gigabit links over 24-fiber ribbon cables terminated with MPO/MTP-24 connectors. It can also be used in 10 x 10 Gigabit Ethernet mode along with ribbon to duplex fiber breakout cables for connectivity to ten 10GBASE-SR optical interfaces. CFP-100G-SR10 interface serves as a more cost-effective solution, which is optimized for data center application and is limited to short distances.


CFP-100G-LR4 Module

CFP-100G-LR4 is standardized by IEEE using standard LC dual fiber interface with single-mode cable, but running four optical wavelengths each direction (1295.56 nm, 1300.05 nm,1304.59 nm, 1309.14 nm) and muxing/demuxing of these wavelengths happening inside CFP module. Each wavelength is running at 25.78 Gbps and it is possible to achieve up to 10 km. Compared to CFP-100G-SR10, CFP-100G-LR4 delivers much better reach for long-haul applications, but at a cost premium.

Comparison Between CFP-100G-SR10 and CFP-100G-LR4

In this section, we’re trying to figure out the difference between CFP-100G-SR10 and CFP-100G-LR4 from the perspective of connectors and cabling used on each. For connectors, 24-fiber MPO/MTP connector is for CFP-100G-SR10 module while dual SC/PC connector for CFP-100G-LR4. Note that only patch cords with PC or UPC connectors are supported. The cabling specification and features for CFP-100G-SR10 and CFP-100G-LR4 are presented in the following diagrams.

100G CFP Module Signal Wavelength (nm) Cable Type Connector Cable Distance Power
CFP-100G-SR10 10×10Gbps 850 MMF (multimode ribbon) Multifiber Push-On (MPO/MTP) 100 m
150 m
6 Watts
CFP-100G-LR4 4×25Gbps 1310 SMF (single-mode duplex) LC/SC 10 km 20 Watts

Service providers and data centers are embracing the trend of 100G network migrations, IT managers and network designers must think twice when choosing from those various 100G transceiver options. CFP-100G-SR10 is preferred due to lower cost over LR4, but its reaching distance is limited. Whereas CFP-100G-LR4 enables data transmission up to 10 km with higher price. This article generally offers some basic knowledge of CFP-100G-SR10 and CFP-100G-LR4 transceiver modules, the decision actually depends on your specific demands and requirements of your applications. Always be aware of what you need, which will work best for you.

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QSFP28 Transceiver: Making the Switch to 100G Network

As data centers around the world explore their options for increasing network speeds and bandwidth, 10G has been a traditional favorite, and 40G is not able to keep pace with the requirements. In this case, 100G network appears to be a preferable option to accelerate data flow for those bandwidth-hungry applications. QSFP28 transceiver module hence becomes the universal data center form factor for 100G optical transmission. This article will address the necessity of 100G network, while illustrating QSFP28 transceiver modules used in 100G transmission.

100G: The Optical Revolution in Data Centers

The 100G adoption rate in optical landscape is consistently on the rise for the past few years. It is predicted that over half of the data center optical transceiver transmission will make the shift to 100G. The traditional 10G or even 40G may not be enough considering the explosion of data, therefore, 100G is going to become the new standard, and it has the following advantages.

100G optical transmission vs. 40G optical transmission

Cost Efficiency—100G now delivers a compelling price point, offering far greater capacity increases for the cost. And it still future-proofing the network with unsurpassed bandwidth.

Proactive Scale—100G offers the expansion and scalability to support the reliability, manageability and flexibility demanded of modern networks while preparing data centers for future bandwidth and speed requirements.

Speed and Capacity—100G optical transport will not be enough for data intensive industries. Thus 100G is specifically designed to transport enormous amounts of data with ultra-low latency.

Flexibility—100G will be the preferred technology across long-haul networks. 100G networking can be customized, optimized, and easily expanded to allow for changes in the future.

Cost Decrease—The market transition to 100GE is now in full force. The growth in 100G deployments will undoubtedly drive down the cost of 100G transceiver modules.

100G QSFP28 Transceiver Unravel

QSFP28 transceiver generally has the exact same footprint and faceplate density as 40G QSFP+ . Just as the 40G QSFP+ is implemented using four 10Gbps lanes, the 100G QSFP28 transceiver is implemented with four 25-Gbps lanes. With an upgrade electrical interface, QSFP28 transceiver is capable of supporting signal up to 28Gbps. Though QSFP28 transceiver keeps all of the physical dimensions of its predecessors, it surpasses them with the strong ability to increase density, decrease power consumption, and decrease price per bit. The Following are some QSFP28 transceivers for different applications.

100G QSFP28 transceiver


100G QSFP28-SR4 came out firstly to support short distance transmission via multimode fiber. This transceiver module can support 100G transmission up to 70m on OM3 MMF and 100m on OM4 MMF. With MTP interface, the 100G QSFP28-SR4 module enables 4×25G dual way transmission over 8 fibers.



100G QSFP28-LR4 is specifically designed for long distance transmission. The module utilizes WDM technology for 4×25G data transmission, and these four 25G optical signals are transmitted over four different wavelengths. With a duplex LC interface, the 100G QSFP28-LR4 module enables 100G dual-way transmission up to 10 km over single-mode fiber.



PSM4 uses four parallel fibers (lanes) operating in each direction, with each lane carrying a 25G optical transmission. It sends the signal down to eight-fiber cable with an MTP interface. The operating distance of 100G QSFP28-PSM4 is limited to 500 m.



DWDM4 uses WDM technology—an optical multiplexer and de-multiplexer to reduce the number of fibers to 2. It can operate on single-mode fiber up to 2 km over duplex LC interface. Compared with QSFP28-LR4, it has shorter transmission distance and lower cost.


100G QSFP28 Cables

In addition to the QSFP28 transceiver modules mentioned above, cables can also be deployed in 100G transmission. The cables can be either direct-attach copper cables (DACs), or active optical cables (AOCs). QSFP28 DACs offer the lowest cost but are limited in reach to about 3 m. They are typically used within the racks of the data center, or as chassis-to-chassis interconnect in large switch and routers. QSFP28 AOCs are much lighter and offer longer reach up to 100 m and more.

Frequently Asked Questions About QSFP28 Transceiver
What Is the Difference Between QSFP28 Transceiver and QSFP+?

These two have the same size form factor and the number of ports, however the lane speeds of QSFP28 transceiver are increased from 10 Gbps to 25 Gbps. The increase in density is even more dramatic when compared to other 100Gbps form factors: 450% versus the CFP2.

How Many QSFP28 Transceiver Modules Can Fit into One Switch?

With QSFP28 transceiver, a one rack-unit (RU) switch can accommodate up to 36 QSFP28 ports. While many more varieties of transceivers and cables (DACs and AOCs) can plug into these ports.


100G QSFP28 transceiver offers direct compatibility with your existing switches and routers, and it facilitates the process of scaling to 100G networks with the simplicity as 10G networks. With higher port density, lower power consumption and lower cost, QSFP28 transceiver is an ideal alternative for large scale data centers, as well as future network expansions. All the QSFP28 transceiver modules presented in this article are available at FS.COM. For more details, please visit

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How to Integrate PoE to Your Network?

You may come across the situation when it is needed to install IP telephones, wireless access points or IP cameras to somewhere AC power outlets are not available. What would you do then? As extra power supply and wiring installation can be labor-intensified and time-consuming. The most feasible solution is to deploy PoE (Power over Ethernet)—a system standardized by IEEE802.3 that supplies low voltage power to Ethernet-enabled devices via the communication line. Here we illustrate how to upgrade your existing network to PoE.

PoE Network Explained

As its name suggests, PoE (power over Ethernet) is the technology to supply power directly via data cable, eliminating the need for additional electrical wiring. It makes network planning flexible and independent of switch sockets and cabinets, requiring no extra costs for excess wiring. Thus devices can be installed wherever structured Ethernet wiring is located, without the need for AC power outlets nearby.

PoE-power over ethernet network

Generally speaking, this technology enables network cables carry electrical power. Let’s take surveillance camera for example: it typically requires two connections when it is installed: a network connection to communicate with video recording and display equipment, and a power connection to deliver the electrical power to operate the camera. However, if this surveillance camera is PoE compatible, all we need is the network connection, as it can receive the needed electrical power from the cable as well.

PoE IP Camera

Advantages of PoE Network

We know that powered devices such as surveillance cameras and wireless access points are often located in places where traditional power outlets are difficult to install or even not available. Under such circumstances, PoE functions to facilitate the use of wireless access devices, IP phones, surveillance cameras, the benefits of which is thus obvious.

The advantages of power of Ethernet features that Ethernet is always ubiquitous, hence it greatly increases mobility for end devices. And as no AC power involved, PoE is safer to use. Moreover, it simplifies installation and operation without the need for extra AC power wiring, keeping the cabling secure while not interfering with the network operation. This makes power over Ethernet a much securer, more reliable and cost-saving solution.

How to Integrate PoE to Your Network?

Before upgrading your existing network to PoE-enabled one. You’d better firstly make clear that there are two types of devices involved in this system: power sourcing equipment (PSE) and powered devices (PD). PD refers to a power over Ethernet compatible network end device equipped to accept power transmitted over structured Ethernet cabling. PSE provides DC power to PD. A PSE may be an endspan device or a midspan device. An endspan device typically is a network switch enabled to provide PoE power on each port. A midspan device is connected in-line to each end device and adds power to the line.

There generally exist three routes to achieve power over Ethernet to your network.

1. By PoE switch: a PoE switch is a network switch that with built-in power over Ethernet injection. Simply by connecting other network devices to the switch as normal, the switch will detect whether they are compatible to power over Ethernet and then enable power automatically. This kind of switches are available to suit all applications, from low-cost unmanaged edge switches with a few ports, up to complex multi-port rack-mounted units with sophisticated management.

PoE switch

2. Using midspan: a midspan enables PoE capability to regular network switches. With midspan, one can upgrade existing LAN installations to PoE. Midspan also provides a versatile solution where fewer ports are required. Upgrading each network connection to power over Ethernet is as simple as patching it through the midspan.

PoE midspan injector

3. Via a PoE splitter: it is also feasible to upgrade powered devices (PDs) to power over Ethernet enabled ones by splitter. This splitter is patched into the camera’s network connection, and taps off the PoE power, which it converts into a lower voltage suitable for the camera.

PoE splitter


The simplicity of combining signal and power in one Ethernet cable connection makes PoE technology an ideal solution for enterprise network. In this case, PSE can provide power to a wide variety of PD in areas with no access to AC power. Deploying this technology in your network will lead to a safe, reliable, and economical way to deliver consistent and dependable power to common networking devices.

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Advice on Server Rack Cable Management

The proliferation of the cloud network and virtualization has brought higher network demands, which means data centers and network closets need to house and support an abundance of power and data cables. It is obvious that fail to deliver proficient cable management within a server rack can be devastated, either for network efficiency and performance, or for the overall look of the data center. The biggest challenge therefore is server rack cable management. This article intends to guide you through the process of achieving effective server rack cable management.

rack cable management

Benefits of Server Rack Cable Management

Here comes a frequently asked question: what exactly can data center operators benefit from valid rack cable management? The aspects listed below may explain.

Improved system performance: rack cable management incline to separate power and data cables within the racks, which greatly decrease the chance for crosstalk and interference between power and data cables.

Enhanced availability: mess of cable sometimes may confuse data center operators, resulting in human error that leads to an assortment of problems to the overall system. Effective rack cable management allows easier cable and IT device management, yet to reduce human error.

Improved maintenance and serviceability: effective rack cable management also ensures easier and safer access to individual components.

Increased cooling efficiency: by allowing hot exhaust air to escape out the back of the rack, cable management keeps cables organized and out of critical airflow paths.

Improved scalability: rack cable management simplifies moves, adds, and changes, making it easier to integrate additional racks and components for future growth.

Steps for Achieving Server Rack Cable Management

Then, we have made clear the importance and advantage of rack cable management. But how to achieve a well-organized and aesthetic appealing data center? We offer this seven-step guide for successful rack cable management.

Step One: Plan appropriately. Planning serves as the very primary stage for power and data cable management in server racks. An appropriate planning contributes to deliver smooth rack cable management process. Consulting a professional cabling contractor can be beneficial to complete the entire project.

Step Two: Determine the routes for power cables and data cables. First to consider if the power and data cabling will enter from the top or bottom of the rack. Then, determine the routes to separate power and data cables, and copper data cables and fiber. This helps to prevent erratic or interference from degrading the performance of the system.

separate power cable and data cableseparate fiber and copper cable

Step Three: Identify cables. Good cable identification and administration are investments in infrastructure. Implement best practices like using colored cables as well as labeling cables to ensure easier cable identification, which contributes a lot to rack cable management.

labeling cable for cable management in rack

Step Four: Route and retain cables. Cables must be protected at points where they might rub or contact with sharp edges or heated areas. Rack cable management accessories like flexible cable tie and cable management arms can be used to route and retain cables.

Step Five: Secure cables and connectors. Cables and connectors should be secured to prevent excessive movement and to provide strain relief of critical points.

Step Six: Avoid thermal issues. Ensure the airflow path is rather important, since restrained airflow can cause temperatures rise. Sustained higher temperatures can shorten devices’ expected lifespan and lead to unexpected failures, resulting in unscheduled system downtime.

Step Seven: Document and maintain organization. Documenting the complete infrastructure including diagrams, cable types, patching information, and cable counts is important for future cable management. IT managers should commit to constructing standard procedures and verifying that they are carried out.


Effective rack cable management helps to improve physical appearance, cable traceability, airflow, cooling efficiency and troubleshooting time while eliminates the chance for human error. Meanwhile, power and data cable management within server racks also ensures the health and longevity of your cables. Hope what we discussed in the article is informative enough.

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How to Use WDM for Fiber Capacity Expansion?

Imagine turning a cottage into a majestic skyscraper without having to deliver any innovation or construction. This is what wavelength division multiplexing (WDM) allows with your existing fiber optic network. The hunger for bandwidth propels service providers to make a substantial investment in upgrading fiber cabling infrastructure. This can be a challenge both economically and practically. However, the WDM technology offers an alternative to increase capacity on the fiber links that are already in place. Without deploying additional optical fiber, WDM greatly reduces the cost of network expansion.

WDM Technology Explanation

Let’s begin with the most fundamental question: What is WDM technology? Short for wavelength division multiplexing, WDM is a way of transmitting multiple simultaneous data streams over the same fiber. Since this happens simultaneously, WDM does not impact transmission speed, latency or bandwidth. WDM functions as multiplexing multiple optical signals on a single fiber by using different wavelengths, or colors, of laser light to carry different signals. Network managers can thus realize a multiplication effect in their available fiber’s capacity with WDM.


To implement WDM to the infrastructure is rather simple, WDM setup generally consists of the following:

  • WDM transmit devices, each operating at a different wavelength
  • Multiplexer, a passive device that combines the different light sources into a blended one
  • Fiber infrastructure
  • De- Multiplexer, a passive device that splits the blended light source into separate ones
  • WDM receive devices


What Capacity Increase Can We Expect?

There are two variants of WDM: CWDM (coarse wave-division multiplexing) and DWDM (dense wave-division multiplexing). The only difference between them is the band in which they operate, and the spacing of the wavelengths and thus the number of wavelength or channels that can be used.

When using WDM on existing fiber cabling, you should also consider the fiber type (single-mode or multimode) and loss level. For CWDM, 8 to 18 devices may be possible, whereas for DWDM, up to 40 channels are the most common case, but it is possible to reach up to 160 channels.


Choose the Right Type of WDM

We’ve known that both CWDM and DWDM are available to optimize network capacity. Then, here comes another question: should I choose CWDM or DWDM technology? Let’s make a comparison of them.

Coarse Wave Division Multiplexing (CWDM)

CWDM increases fiber capacity in either 4, 8, or 18 channel increments. By increasing the channel spacing between wavelengths on the fiber, CWDM allows for a simple and affordable method of carrying up to 18 channels on a single fiber. CWDM channels each consume 20 nm of space and together use up most of the single-mode operating range.


Benefits of CWDM:

  • Passive equipment that uses no electrical power
  • No configuration is necessary, much lower cost per channel than DWDM
  • Scalability to grow the fiber capacity as needed
  • With little or no increased cost
  • Protocol transparent and ease of use

Drawbacks of CWDM:

  • 18 channels may not be enough, and fiber amplifier cannot be used with them
  • Passive equipment that has no management capabilities
  • Not the ideal choice for long-haul networks
Dense Wave Division Multiplexing (DWDM)

DWDM allows many more wavelengths to be combined onto one fiber. DWDM comes in two different versions: an active solution and a passive solution. An active solution requires wavelength management and is well-suited for applications involving more than 32 links over the same fiber. In most cases, passive DWDM is regarded as a more realistic alternative to active DWDM.


Benefits of DWDM:

  • Ideal for use in long-haul and areas of greater customer density
  • Up to 32 channels can be done passively
  • Up to 160 channels with an active solution
  • Active solutions involve EDFA optical amplifiers to achieve longer distances


Drawbacks of DWDM:

  • DWDM solutions are quite expensive
  • Active DWDM solutions require a lot of set-up and maintenance expense
  • Very little scalability for deployments under 32 channels, much unnecessary cost is incurred per channel

To sum it up, CWDM can be typically used for applications that do not require the signal to travel great distances and in locations where not many channels are required. While for applications that demand for a high number of channels or for long-haul applications, DWDM is the ideal solution.

Considerations for Deploying WDM

Making sure that the CWDM and DWDM will perform properly is critical, so one should account for the following aspects for when deploying.

1.Before buying a mux or demux for use in an unconditioned cabinet or splice case, verify that the operating temperature will fit the application. And ensure that the CWDM or DWDM will be able to operate within the temperatures in which they will be placed.

2.Take the insertion loss of WDM network into account. Using the maximum insertion loss value in the link budget is a good idea. Calculate the loss for both the mux and demux components.


WDM technology provides an ideal solution for fiber exhaust problem that many communication providers are experiencing. It eliminates the need for investing on new fiber construction projects while greatly increases fiber capacity of the existing infrastructure. Hope what presented in the article could help you to choose the right WDM solution.

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Server Rack Choice: How to Make the Right Decision?

Server rack functions to organize IT equipment (servers and network switches) into assembly order to make the most use of space and resources. Therefore, it can affect the availability, serviceability, flexibility and manageability of the data center to a large extent. In other words, your daily operation and maintenance rely heavily on your rack choice. Well, since not all the server racks are created equal, it is thus essential to choose the right one that matches your current needs as well as future network growth. Then, let’s see how to choose the right server rack.

What Is a Server Rack and Why We Need it?

A  server rack basically consists of two or four vertical mounting rails and the supporting framework required to keep the rails in place. Typically made of steel or aluminum, rails and framework are capable of holding hundreds or even thousands of pounds of equipment. For now, the vast majority of IT applications use 19-inch racks and equipment. As the width of which is always the same, the height and depth can be various.

data center server rack

Be it a data center, server room or even cabinet closet, racks are always needed to accommodate IT production equipment, such as servers, storage, network switches, routers, telecommunication hardware and other devices. Server rack is designed to hold all standard 19-inch rack-mountable equipment, as long as it isn’t too deep for the cabinet or too high to fit in the available rack spaces. Moreover, server rack also holds IT infrastructures and rack accessories that support the operation of the production equipment, including UPS systems, PDUs, cable managers, KVM switches, patch panels and shelves.

Common Server Rack Types Analysis

Generally, there are three types of server rack: open frame racks, rack enclosures and wall-mount racks.

Open frame racks are just open frames—with mounting rails but no sides or doors. This kind of rack is typically used for applications that do not need the rack to perform airflow control or provide physical security. Open frame racks are optimal for network wiring closet and distribution frame applications that have high-density cabling, due to they offer flexible access and lots of open space that facilitate cable management.

open frame rack

Rack enclosures are also referred to as rack cabinets, they have removable front and rear doors, removable side panels and four adjustable vertical mounting rails. The front and rear design of rack enclosures achieves ample airflow for any installed equipment. Rack enclosures provide an ideal alternative for applications which require heavier or hotter equipment. And they often include additional rails to mount accessories like vertical cable managers and PDUs. Nowadays, rack enclosures have gained in much popularity in data centers and server rooms.

rack enclosure

Wall-mount racks just do what the name indicates—they can be attached to the wall. In this case, wall-mount racks can save floor space and fit in areas where other racks cannot. They can be open frame racks or enclosed cabinets. Wall-mount racks fail to support as much weight as their counterparts since they are basically smaller than those floor-standing ones. However, by adding rolling casters, they can also accommodate floor-standing applications.

wall-mount rack

What Should I Look for a Server Rack?

There exist a dazzling array of server rack options, in terms of different heights, sizes and styles. When selecting the server rack for your installation, here are some factors to consider:

AV vs. IT-based installations: the choice should better depend on the equipment being installed. IT racks are designed for use with traditional IT equipment in which the I/O and cabling is on the front of the rack. This makes easier troubleshooting and network monitoring. AV racks, however, are typically shallower in depth, enabling a cleaner installation by using equipment with rear facing I/O so that cabling is hidden in the back.

Airflow and cooling: these two factors are critical to the performance and longevity of the equipment installed in the server rack. Depending on the airflow condition of the place where the server rack will be located, you may need to increase the rack’s cooling capability. Fortunately, multiple cooling options are available now, but remember to consider the noise level tolerated.

Equipment width: with 19-inches being the traditional standard for rack mounted network hardware, some vendors make custom sizes for other types of equipment. Make sure to check what size of server rack your equipment requires.

Security options: while there might be a great amount of expensive equipment installed on the server rack, you have always to bear security in mind. A server rack that meets the security goal is thus essential. Locking cabinet and tinted door glass can help protecting your network from prying eyes and hands.


Although selecting the server rack may not sound like a big decision to make, your choice can actually affect the overall performance and operation of the network. The right type of server rack that meets your installation demand helps you improve power protection, cooling, cable management, and physical security. Taking the above factors into consideration and thinking thoroughly before making the choice.

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How to Install Splice Protection Sleeve in Splice Holder?

Fusion splicing offers a simplified and convenient way to achieve fiber optic connectivity. Providing a rather consistent and low loss mating of fiber optic stands, fusion splicing is preferred by many installers as an efficient method to connect fibers together. Fragile as the fiber joint is, it is easily impacted by stress and outside force. Hence, a splice protection sleeve should be necessarily used to safeguard the fiber splice in field and factory operations. We will present several common types of splice protection sleeve here, and try to explain how to install it in splice holder.

Splice Protection Sleeve Description

Generally speaking, splice protection sleeve is typically used to protect fiber joint in the fiber optic fusion splicing work. It basically consists of three parts: a hot melt type adhesive inner tube and a strength member, enclosed in a cross-linked, polyethylene heat shrinkable outer tube. The design ensures consistent and reliable protection of spliced fiber, and secures fiber alignment from damage during shipping, handing and installation. Here we introduce the commonly used splice protection sleeve for you.

splice protection sleeve

Single Fiber Splice Protection Sleeve

Single fiber splice protection sleeve is often with 40mm or 60mm length, whereas 45mm sleeve is specifically provided by some vendors. It is designed to offer simple, convenient and highly reliable ways to protect and reinforce single fiber splice. The highly transparent tube of single fiber splice sleeve allows for direct view of the inside joint part, which facilitates regular inspection and maintenance.

single fiber splice protection sleeve

Ribbon Fiber Splice Protection Sleeve

Ribbon fiber splice protection sleeve is used to protect mass fusion splices of ribbons. Different from single fiber splice protection sleeve, it is capable of accommodating multiple fiber splices, ranging from 2, 4, 8, and up to 12 spliced fibers. The tubes of ribbon fiber splice protection sleeve are clear to allow viewing of the fiber during and after splicing. The entire assembly is designed to ensure that all members maintain perfect alignment during handling and shrinking.

ribbon fiber splice protection sleeve

Considerations Before Installing Splice Protection Sleeve

Before installing the splice sleeve to the splice holder, do not forget to carefully inspect the finished sleeve. Basically there may exist the following common problems.

1. Debris inside the sleeve, which can cause an attenuation increase or fiber break. The solution is to thoroughly clean the fiber before sliding on the sleeve and to store the sleeves in a plastic bag to prevent debris from entering the splice protection sleeve during storage.

Debris inside the sleeve

2. Improper tension on the fiber. Fail to maintain tension on the fiber during the heat shrink process my cause non-parallel fibers that result in an attenuation increase or broken fibers. So it is essential to maintain tension on the fibers when placing into the tube heater, and avoid twisting the fiber when placing or removing from the heater.

Improper tension on the fiber

3. Cable gel or grease inside sleeve. This may have a similar effect on the fibers as solid debris and may cause bending of the fibers in a relatively short span. The solution is to thoroughly clean the fiber before sliding on the sleeve, and to not touch the fibers once they have been properly cleaned.

cable gel in sleeve

4. Sleeve splitting when heated. This happens due to improper tube heater settings or because the sleeve suffered a cut or puncture before being heated. This can be avoided by ensuring correct tube heater settings and by keeping the splice protection sleeve in the plastic bag until ready for use.

split sleeve

Method to Install Splice Protection Sleeve in Splice Holder

The spliced fibers are always stored in a splice sleeve holding apparatus of splice trays. The holders can be foam or plastic depending on the construction and dimensions of the splice tray. In this part, we offer you a proper way to achieve safe and successful installation.

splice protection sleeve in splice tray holder

Correct Installation Method

The strength member inside the splice protection sleeve is designed to provide protection during installation and removal from splice holders. To this end, one could insert the spliced fiber into a holder with the strength member in the down position. Which means it is the strength member, not the fiber, that should be installed firstly into the target holder position. This minimizes contact of the fiber and facilitates remove a splice sleeve whenever necessary.

correct splice protection sleeve installation

Incorrect Installation Method

Never install the fiber prior to the strength member or put the fiber and strength member parallel to the base of the fiber holder. This would exert excess stress to the fiber, splice protection sleeve and the fiber holder as well. The consequence is increased insertion loss of the fiber.

incorrect splice protection sleeve installation

incorrect splice protection sleeve installation-2


Small as it might be, splice protection sleeve provides robust and reliable protection to fiber splice in fusion splicing work. Appropriate installation of splice protection sleeve ensures optimum performance and accessibility when placed in splice holders and trays. And do remember to visually inspect the splice protection sleeve before seating them in holders.

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