Hybrid CWDM-DWDM System Boosts Your Network Capacity


Should I choose a medium capacity but more cost-effective CWDM solution, or to adopt the cost-prohibitive DWDM approach with comparably enhanced capacity? This is a problem that consistently faced by WDM technology users. The wrong decision, however, may inevitably lead to bandwidth shortage or even potential bankruptcy derived from unnecessary capacity investment. This article introduces the hybrid CWDM-DWDM solution that combines both CWDM and DWDM technologies within a single system, helping decrease costs and simplify installation while maintain the flexibility to upgrade.

Hybrid CWDM-DWDM System Explanation

Hybrid CWDM-DWDM system utilizes the technology to merge DWDM and CWDM traffic seamlessly at the optical layer. Which allows carriers to add many channels to networks originally designed for the more limited CWDM capacity and reach. In other words, hybrid CWDM-DWDM system is used to empower CWDM system by integrating CWDM and DWDM equipment. Hybrid CWDM-DWDM system deliver true pay-as-you-grow capacity growth and investment protection. It offers a simple, plug-and-play option for creating hybrid system of DWDM channels interleaved with existing CWDM channel plans.

Benefits of Hybrid CWDM-DWDM System

Hybrid CWDM-DWDM system typically provides three benefits for carriers and users:

  • Reduced Cost: CWDM is more cost-effective than DWDM due to the lower cost of lasers and the filters used in CWDM modules. This cost saving becomes quite significant for large deployments.
  • Pay-As-You-Grow: Adding one new channels at a time allows for on-demand service introduction with minimal initial investment—a critical feature in terms of reduced OPEX and CAPEX spending.
  • Investment Protection: Carriers and end-users need always to bear the future growth in mind. With hybrid CWDM-DWDM system, carriers no longer have to choose between CWDM and DWDM—both options can be deployed simultaneously or as part of future growth. This module can be used in either CWDM or DWDM system. Current capital investment can always be used in the upgraded network.
How to Deploy Hybrid CWDM-DWDM System

The CWDM wavelength grid typically has 16 channels spacing at 20 nm intervals, with 8 channels (1470 nm-1610 nm) of them are most commonly used. Within the pass band of these channels, it is capable of adding 25 100 GHz spaced DWDM channels under the 1530nm envelope and 25 more under the 1550nm envelope. However, it is not so practical to add 25 DWDM channels in the pass-band of both the 1530nm and 1550nm CWDM channels. DWDM filter technology does allow 38 additional channels to clear the CWDM archway, which is shown as following.

hybrid CWDM-DWDM systems

To add more DWDM channels to the MUX side of the conventional CWDM system, one need to plug in a DWDM MUX with the appropriate channels under the pass band of the existing CWDM filters. The picture below illustrates the configuration of a CWDM system upgraded with 38 additional 100 GHz spaced DWDM channels. This hybrid CWDM-DWDM system consists of 38 DWDM channels and the existing 6 CWDM channels. The equipment required to go from the first architecture to the second are 2 DWDM MUX/DEMUXs, as well as the additional transmitter and receiver pairs. The additional loss incurred by the upgrade is equal to the additional loss of the DWDM elements and the additional connection points.


Flexible Hybrid CWDM-DWDM System Solution by FS.COM

The most vital elements concerning hybrid CWDM-DWDM system are the CWDM MUX/DEMUX and DWDM MUX/DEMUX. FS.COM developed and introduces FMU series products to facilitate installation and operation of WDM MUX/DEMUX. The prominent feature of this series products is that they combine the MUX/DEMUX into half-U plug-in modules, which can be installed in a 1U rack. As for hybrid CWDM-DWDM system, a FMU CWDM MUX/DEMUX and a DWDM half-U plug-in module can be installed together in a FMU 1U rack chassis, facilitating connections of these two modules while allowing for better cable management and network operation in hybrid CWDM-DWDM system.



Hybrid CWDM-DWDM system generally offers a cost-effective and future-proofing approach for service providers and end-users, by overcoming the obstacles faced by users of WDM technology today, providing a starting platform that scales smoothly and protecting the investment. A user can commence with the more cost-effective CWDM technology and then later add DWDM in the when the capacity is required. FS.COM FMU series WDM solution makes the process even easier and more flexible. For more information, please visit www.fs.com or contact sales@fs.com.

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Extending DWDM Network Reach With Raman Amplifier

Raman amplifier is appearing to be a critical technology which is consistently developed for using in optical communication networks. Typically applied in long-haul networks, Raman amplifier is also expected to extend its reach in dense wavelength-division multiplexing (DWDM) networks. This escalating adoption, therefore, is fueled by the massive bandwidth demand that network operators are continuously facing. This article explains the necessities and related considerations for deploying Raman amplifier in DWDM networks.

Why Use Raman Amplifier and How it Works?

Raman amplifier has proved itself beneficial for applications in 100G network and above. It is gaining in popularity because it is capable of meeting the need for higher transmission capacity. There exist various alternatives to enhance network transmission capacity: like extending beyond the C-band into the L-band, increasing the symbol rate or increasing spectral efficiency. Any of the options requires a higher optical signal-to-noise ratio (OSNR). Raman amplifier generally offers higher OSDR required to increase capacity, while eliminates the need for expensive opto-electronic regeneration.

EDFA vs.Raman amplifier

Raman amplification generally leverages the network fiber as the gain medium. By adding a distribution Raman amplifier to a fiber span with EDFAs, signal power loss can be decreased. The commonly deployed counter-propagating Raman amplifier consists of one or more Raman pump lasers and a wavelength combiner, so that the Raman pump wavelengths are transmitted into the fiber in the opposite direction of the signal. Signal propagating along the fiber will be attenuated, but as it moves along toward the fiber end where the Raman pump is located, it will start to experience some gain from the Raman pump wavelength. The higher power in the signal thus increases OSDR, which enables longer fiber span, higher capacity and spectral efficiency, and longer link distance.

Solutions for Extending DWDM Reach With Raman Amplifier

With EDFA being the default amplifier for use in DWDM transmission, Raman amplifier is found critical and effective in complementing the EDFA for transmission distance expansion. It typically provides an improvement in performance that cannot be obtained by EDFA alone. The application of Raman amplifier in DWDM network is demonstrated below.

The following picture illustrates the effect of Raman amplification on a simple multispan link with 23 dB loss per span compensated by 23 dB of amplification. In one case, each span loss is compensated with an EDFA, while in the other case, the gain is divided between the distributed Raman amplifier and the EDFA. Inferring from the figure, it is clearly that with the hybrid EDFA/Raman amplification, the OSNR curve has shifted upwards towards higher OSNR values. This means the link can obtain higher OSNR for the same span number, or, the same OSNR for a much larger span number. By incorporating Raman amplifier into DWDM networks, the link becomes more robust, with more margin available for future repairs or changes along the link.

hybrid EDFA and Raman amplifier

Deployment Considerations for Raman Amplifier

It is undoubted that Raman amplifier can provide significant benefit to DWDM networks, what should be noticed here is that, there are also several key precautions to deploy Raman amplifier in real-life environment, which must be addressed so that the potential benefits can be fully realized.

Keep Fiber Clean

When deploying Raman amplifier in a DWDM system, the equipment needs to be connected to the network fiber with minimum connection loss. Since contamination like dust and dirt, or misalignment is detrimental to fiber attenuation, network operators must keep the fiber and connectors clean during the connection process, not degrade the performance of the system.

Connection Loss

Connection loss could have a significant impact on the whole network. The following picture shows the reduction in Raman gain due to different connector losses when the connector is located very close to the Raman pump. The three curves correspond to different fiber attenuation levels at 1550 nm. In this example, a Raman amplifier with a net gain of 15 dB is involved, a 1 dB connection loss can result in a 4 dB gain reduction, and a 2dB connection loss increases the reduction in Raman gain to 7 dB.

impact of connection loss on Raman amplifier

Location of the Loss Element

The location of the loss element serves as a vital factor. The figure below shows the Raman gain reduction according to different position of the loss elements, at 0 km, 5 km, 10 km and 20 km away from the Raman pump. It reveals that the Raman gain reduction is lower if the connection loss is located further away from the Raman pump. This is because most of the Raman gain occurs close to the Raman pump. We can also conclude that most of the gain obtained through Raman amplification is obtained in the region of the effective length of the fiber, which is in the ~20km range.

location of loss elements with raman amplifier


Adoption of Raman amplifier significantly consolidates optical link while extends transmission reach in DWDM networks. Raman amplifier also serves as a good implementation of EDFAs, enabling applications which are not feasible or practical with conventional EDFA technology. Thus increasing the distance and capacity of long-haul DWDM systems.

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Optical Transponder (O-E-O) Used in WDM Network

WDM technology is commonly used in today’s optical network. It basically assigns each service (10G LAN, SONET/SDH, Fiber Channel, etc) an independent dedicated wavelength—which then is multiplexed into one single fiber. Eliminating the use of multiple fibers while increasing fiber capacity, WDM system is beneficial to both service providers and end users. Optical transponder, also referred to as O-E-O (optical-electrical-optical), serves as an integrated part of WDM system and it is critical for signal transmission in the whole system. This article will guide you through how optical transponder operates in a WDM network.

Basics of Optical Transponder (O-E-O)

The optical transponder (O-E-O) works as a re-generator which converts an optical input signal into electrical form, then generates a logical copy of an input signal and uses this signal to drive a transmitter to generate an optical signal at the new wavelength (optical-electrical-optical). Its most prominent feature is that it automatically receives, amplifies, and then re-transmits a signal on a different wavelength without altering the data/signal content. Clients can be electrical or optical (1310 or 1550 nm), co-located or some distance away. Line side interfaces can be fiber, CWDM or DWDM with a variety of reaches supported.

optical transponder (O-E-O)

Common Applications of Optical Transponder (O-E-O)

Optical transponder is widely accepted in WDM networking and many other applications. let’s go through some commonly used ones.

1. Multimode to single-mode conversion

Some optical transponders can convert from multimode to single-mode fiber, short reach to long reach lasers, and/or 850/1310 nm to 1550 nm wavelengths. Each optical transponder module is protocol transparent and operates fully independent of the adjacent channels.

multimode to single-mode conversion

2. Redundant fiber path

Each optical transponder module can also include a redundant fiber path option for extra protection. The redundant fiber option transmits the source signal over two different optical paths to two redundant receivers at the other end. If the primary path is lost, the backup receiver is switched on. Since this is done electronically, it is much faster and more reliable.

redundant fiber path

3. Repeater

As an optical repeater, some optical transponders effectively extend an optical signal to cover the desired distance. With the clock recovery option, a degraded signal can be dejittered and retransmitted to optimize signal quality.


4. Mode Conversion

Mode conversion is one of the quickest and simplest ways of extending multimode optical signals over greater distances on signal-mode fiber optics. And most receivers are capable of receiving both multimode and single-mode optical signals.

mode conversion

5. Wavelength Conversion

Wavelength conversion in commercial networks today is only carried out by optical transponder. We know that optical network equipment with conventional fiber interfaces like LC, SC, ST, etc operates over legacy wavelength of 850 nm, 1310 nm, and 1550 nm. Which means they must be converted to CWDM or DWDM wavelength to fit in the system, and this is what WDM transponders used for—converse wavelength by automatically receiving, amplifying, and re-transmitting a signal on a different wavelength without altering the data/signal content. The following picture depicts the conversion process: a 10G switch (with signal output of 1310 nm) is to be linked to a CWDM Mux/Demux channel port (1610 nm). An optical transponder with a standard SMF SFP+ and a 1610nm CWDM SFP+ is adopted between the switch and CWDM Mux/Demux, thus the wavelength conversion is realized by the optical transponder.

wavelength conversion

Network Structure with Optical Transponder

Then how exactly optical transponder benefits your network system? Here we provide two possible configurations of network over WDM ring which deploys optical transponder.

For line network over a WDM ring

The line network consists basically of two point-to-point links between A-B and B-C, each requiring transponders at the endpoints. If node B fails, communication between A and C should still be possible, because B can be bypassed by the two adjacent optical transponders. For this the protection in/outputs of the transponders are connected by a bypass link. If node B fails, S1 in both transponders switch to the protection connection.

optical transponder in line network

For star network over a WDM ring

As for a star network over a WDM ring, where the nodes A, C and D are connected to the star node B. Node B has a backup node B’ for redundancy. Here the protection in/outputs of the transponders are used to connect the nodes A, C and D to node B’ if node B failed.

optical transponder in star network


Optical transponder holds a critical position in WDM networking system and cannot simply be underestimate. We have illustrated the functionality and applications of optical transponder, as well as presenting possible configurations of network over WDM rings. Hope that may help you to have a better understanding of the optical transponder.

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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 www.fs.com.

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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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