What’s DAC Cable And Why Choose It Over Fiber Transceiver?


Driven by demand for higher speed fiber cables, network cabling has gone through great changes over the years. Cat5e copper cabling and 1000BASE-T have dominated data center interconnection application for years. However, SFP cable becomes a new favorite with less cost and lower power consumption, which is a form of the high-speed cable with pluggable connectors on either end. This direct attach cable can be classified to DAC cable and AOC cable. DAC cable is the most basic form of high speed direct attach cabling. This article intends to introduce the DAC cable and its benefits. For more information, read Active Optical Cable (AOC) – Rising Star of Telecommunications & Datacom Transceiver Markets

What Is DAC Cable?

Direct attach copper cable, short for DAC cable, is a kind of fixed high speed copper cable assembly. It consists of shielded twinax copper cable with pluggble  connectors on either end with varying gauges from 24 to 30AWG: The longer the distance, the higher the AWG rating should be. It can be used to connect switches to routers or servers for short transmission distance. In addition, DAC cables are commonly available in several different categories: SFP+ DAC, XFP DAC, QSFP DAC and so on.

DAC cable

Figure 1: DAC cable

Types of DAC Cable

Generally, according to the construction difference, the DAC cables can be classified into two types: passive DAC cable and active DAC cable.

Passive DAC cables have no electrical components built into the cable assembly. Hence, it has the minimal power consumption of no more than 0.15w and generally for short reach up to 7m.

Active DAC cables have signal amplification and equalization built into the cable assembly. Therefore, it allows a little longer transmission distance up to 15m and ensures better transmission quality. whereas it has a higher price and consumes more power around 0.5-1w.

passive and active DAC cables

Figure 2: passive and active DAC cables

Why Choose DAC Cables Over Optical Transceivers?

When considering whether to use DAC cables or optical transceivers, one may be confused. Nowadays, DAC cable is very popular with the following advantages:

  • Less Power Consumption – Compared to optical transceiver modules, DAC cables, especially passive copper cables consume less power.
  • Lower Price – DAC cables are less costly for they do not need patch panels or additional cables when connected to devices as optical transceiver modules.
  • Simpler Deployment – DAC cable has only one component to be interconnected. However, the optical transceiver has to be connected with more devices, which must be matched with each other. Besides, it is convenient for installers to conserve DAC cables, they don’t need to clean and inspect optical fiber before plugging cables.

Where to Use DAC Cables?

Utilized in various applications in a data center, the DAC cables can extend the life of the switch hardware without having to change the existing infrastructure. In general, this direct attach copper cable is effective for the following applications:

  • ToR/Adjacent Racks – Passive and active DAC cables both are suitable for shorter ToR or adjacent racks.
  •  Middle of Row – As long as the distance is no more than 15m, the active DAC cable may be the best solution in this application.
  • End of Row – DAC cables are ideal for the end of row architectures as long as the distance is suited.
application of DAC Cables

Figure 3: application of DAC Cables


According to the aforementioned details, we know that there are two types of DAC cables, namely passive DAC and active DAC. The former is recommended for the transmission which is no more than 7 m and the latter is suitable for 7-15 m. DAC cable is an ideal high-speed solution for data center interconnections. And all the DAC cables mentioned above are supplied in FS. If you need to know more details, please visit www.fs.com.

Related Article: SFP+ DAC Twinax Cable Deployment Considerations

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What Is RJ45 SFP Module And How to Use It?

Transceiver module, known as the essential optics for data transmission, is widely used to connect network applications like switches and network interface cards. Various types of transceiver modules exist, such as copper SFP, fiber SFP, CWDM SFP and so on. RJ45 SFP module is a kind of transceiver modules, which has been utilized as a legacy solution for some years. This article will give a clear explanation to RJ45 SFP module, its benefits and how to use it.

What Is RJ45 SFP Module?

RJ45 SFP module, also known as copper SFP, is a kind of hot-pluggable transceiver module. It supports 10/100/1000 Mbps data rate over Cat5e or Cat6 cables with RJ45 connector interface. And it allows communications over the twisted-pair copper cable of link lengths up to 100 m. So it is commonly used for transmitting data in a short distance, for instance, for server switching, LANs in data centers, for uplinks or directly to the desktop for broadband applications. In addition, with the increasing demand for high-speed communication links, some vendors started implementing a popular and updated copper module: 10GBASE-T SFP+ copper transceiver. It is the first 10G copper SFP RJ45 module, which requires 10 gigabit Ethernet over Cat 6a/7 cable and offers great savings and flexibility during network deployment.

RJ45 SFP module

Figure 1: RJ45 SFP module

Why Choose RJ45 SFP Module Over Optical SFP Module?

The battle between fiber optic SFP module and RJ45 SFP module still hot in the field of the transceiver module. Optical SFP module with LC or SC optical connectors is used in Fast Ethernet and Gigabit Ethernet allowing transmission distance up to 120km. Compared to optical SFP, RJ45 SFP module has the following advantages:

  • Cost-effective in Short Runs

Cost is an important factor in employment. When the link distance is under 100 m, choosing the copper SFP module to connect the switches might be more economical since copper SFP and Cat5e or Cat6 cables are lower-priced than optical SFP transceiver module.

  • Simpler Deployment

Copper SFP transceiver is convenient for operators to deploy their network systems. Copper SFP module can be plugged directly into the existing copper cabling system, which can make seamless upgrades and replacements by minimizing network disruptions. While if you choose optical transceiver, you have to tear down the existing copper cabling and redeploy the fiber cabling.

How to Use RJ45 SFP Module?

RJ45 SFP module is usually utilized to connect two switches with copper interface over Cat5e or Cat6 cable. The following will show you how to install, connect and remove the RJ45 SFP module in detail.

Installing A RJ45 SFP Module
  1. Attach an ESD preventive wrist strap to your wrist and to a bare metal surface.
  2. Remove the copper SFP module from the protective packaging.
  3. Find the copper SFP markings on the module and align them in front of the slot opening.
  4. Insert the copper SFP module into the slot on the switch until the copper SFP module snaps into position.
Connecting A Cat5 Cable
  1. Insert Cat5 cable into the RJ45 connector of the copper SFP module.
  2. Make sure the Cat5 cable has been pushed into the copper SFP module.
Removing A RJ45 SFP Module
  1. Attach an ESD preventive wrist strap to your wrist and to a bare metal surface as well.
  2. Disconnect the cable in the SFP module.
  3. Unlock and remove the copper SFP module
  4. Put the removed SFP module within the protective packaging or antistatic bag.


When you choose an RJ45 SFP module, the quality and cost matter a lot. So the three-party vendor may be a good choice. FS.COM not only supplies compatible RJ45 SFP modules which all meet the standards or MSA, but also provides reliable switches and patch cables. If you have any needs, welcome to visit FS.COM.

Related Article: Understanding of 10GBASE-T SFP+ Copper Transceiver Modules

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Single Mode SFP vs Multimode SFP: What’s the Difference?

SFP transceiver module, also known as small form-factor pluggable or mini GBIC, is a hot-pluggable optical transceiver module which is commonly used for both telecommunication and data communications applications. According to the cable type it used together with, SFP transceivers are divided into single mode SFP and multimode SFP. Single mode SFP works with single mode fiber, while multimode SFP works with multimode fiber. Well, what’s the other differences between single mode SFP and multimode SFP? Here has a detailed introduction for single mode SFP vs multimode SFP.

single mode SFP vs multimode SFP

Figure 1: single mode SFP vs multimode SFP

What are Single Mode SFP & Multimode SFP?

As mentioned above, single mode SFP (SMF SFP) works over single mode fiber whose typical core diameter is 9µm. And the cladding diameter of a single mode fiber is 125µm. Single mode SFP works mainly in 1310nm and 1550nm wavelength. Therefore, it is suitable for long-reach data transmission applications reaching 2 km, 10 km, 40 km, 60 km, 80 km and 120 km. There are many types of single mode SFP modules, for instance, 1000BASE-EX, 1000BASE-ZX and so on.

Multimode SFP (MMF SFP) works over multimode fiber with the core diameter of 50 µm and 62.5 µm, and the cladding diameter is 125µm as well. The common multimode SFPs work in 850nm wavelength and are used for short distance transmission, reaching 100 m and 500 m. There are many types of multimode SFP modules such as 1000BASE-SR and so on.

Single Mode SFP vs Multimode SFP: What’s the Difference?

There are several main differences between single mode SFP and multimode SFP:

Single Mode SFP vs Multimode SFP: Working Wavelength

Single mode SFP module has a narrower laser wavelength, which works mainly in 1310nm and 1550nm wavelength. Whereas multimode SFP module works in 850nm wavelength due to the larger core size.

Single Mode SFP vs Multimode SFP: Color Coding

The color coded bale clasp and color arrow of single mode SFP modules are generally designed in blue, yellow or purple. Blue is the 1310nm module, yellow is the 1550nm module and purple is the 1490nm module. And the color of compatible fiber optic patch cord is yellow. While the color coded bale clasp and color arrow on the label of multimode SFP modules are black and the used fiber optic patch cord is usually orange.

Single Mode SFP vs Multimode SFP: Transmitter

Single mode SFP and multimode sfp use different types of transmitters. VCSELs are typically used in multimode SFP transceivers. They can be tested on the wafer level and don’t need a hermetic package. Edge-emitting lasers, such as Fabry–Pérot, DFB and DBR lasers, are utilized in single mode SFP modules for different reaches and applications. They have complex layer structures and often require a hermetic package to achieve higher emission power and stable single mode operation. Therefore, Edge-emitting lasers are more costly than VCSELs.

Single Mode SFP vs Multimode SFP: Cost

When comparing single mode SFP vs multimode SFP in terms of cost, single mode SFP is more expensive than multimode SFP. The cost difference between single mode SFP and multimode SFP mainly arises from the different transmitters they use. As mentioned above, the transmitter of single mode SFP is more costly than that of multimode SFP. Hence, multimode SFP module is cheaper.

How to buy And Use Single Mode SFP & Multimode SFP?

When we buying single mode SFP or multimode SFP in the market, we must confirm the transmission distance and wavelength we need. This will help us to choose the right SFP types more efficiently. The cost for transceiver modules is also a significant factor considered by many users. Well, the compatible SFP module should be recommended as a simple and convenient choice. Because it not only sacrifices no quality or reliability but also has a low cost. Hope these tips could help you make an informed decision.

SFP module

Figure 2: how to buy single mode & multimode SFP

Tips on using Single Mode SFP & Multimode SFP

Single mode SFP and multimode SFP modules are both used in the switch slot and support communication over either fiber optic or copper networking cable. When you use single mode SFP or multimode SFP, you’d better keep these tips in mind:

  • Make sure that SFPs in both ends of the fiber patch cord are of the same wavelength and consistent in color coding.
  • To ensure the data accuracy, short-wave SFP modules are generally utilized with multimode fibers (ie. orange fiber patch cord), while long-wave SFP modules with single mode fiber (ie. yellow fiber patch cord).
  • Protect the optical port by dust plug when not using the SFP.

Single Mode SFP vs Multimode SFP:Which One to Choose?

After the comparison of single mode SFP vs multimode SFP, we can see that single mode SFP is suitable for long-reach data transmission applications while multimode SFP is generally utilized for short transmission distance. Which to choose depends on the actual needs. FS supplies various kinds of optic transceivers available in both single-mode and multimode. If you have any needs, welcome to visit FS.COM.

Related Article: How Many Types of SFP Transceivers Do You Know?

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Passive CWDM vs DWDM: What’s the Difference?

WDM (Wavelength Division Multiplexing) is a commonly used technology in optical communications. It is often deployed to join multiple wavelengths onto a single fiber. In the WDM system, there are two main types: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). Both CWDM and DWDM are available as active or passive systems. This article will focus on discussing the difference between passive CWDM vs DWDM.

passive cwdm vs dwdm

Figure 1: passive CWDM vs DWDM

What Is Passive CWDM?

CWDM is often employed in situations where only a few channels are needed and there is no need for distances longer than 70 km. The passive CWDM is an implementation of CWDM that uses no electrical power. It divides the wavelengths by passive optical components like bandpass filters and prisms. Most CWDM devices are passive. CWDM Mux Demux is the most commonly used device in passive CWDM system.

What Is Passive DWDM?

DWDW technology is used for long haul optical transmissions. It can be divided into two different versions: an active solution and a passive solution. The active solution is a good fit for applications involving more than 32 links over the same fiber. Passive DWDM solutions have fewer active elements, in other words, the solutions have higher reliability and less latency. In a passive DWDM network, the line functions only due to the use of optical transceiver. Passive DWDM systems allow to arrange a high speed system with high channel capacity, but the transmission distance and management are limited. The major applications of passive DWDM system are metro networks and high speed communication lines.

passive DWDM

Figure 2: passive DWDM

Passive CWDM vs DWDM: What’s the Difference?

Passive DWDM and CWDM are based on the same concept of using multiple wavelengths of light on a single fiber. Both of them require no power and are easy to employ. However, they still differ to each other in some aspects. The following will describe some differences between passive CWDM vs DWDM.

Wavelength Spacing

Passive CWDM transports up to 18 wavelengths (from 1470nm to 1610nm) with a channel spacing of 20nm. While passive DWDM can accommodate 40, 80 or up to 160 wavelengths with a narrower wavelength spacing of 0.8nm, 0.4nm or even 0.2nm. Its wavelengths are from 1525nm to 1565nm (C band) and 1570nm to 1610nm (L band).

Channel Number

Passive DWDM supports more channels than passive CWDM. The former can provide up to 80 channels while the latter just supports up to 18 channels.

Transmission Distance

The maximum reach of the passive CWDM is about 160 km. Although the passive DWDM system has no optical amplifiers to achieve a fairly long distance, it can reach longer than the passive CWDM.


Actually, the cost is associated with the deployment of the system. In general, the passive DWDM devices are more expensive than that of passive CWDM systems. But the passive CWDM is just cost-effective for the connection rates below 10G and for short distance.


After the comparison of passive CWDM vs DWDM, we can see that each one has its advantages and disadvantages. Which to deploy depends on the actual needs. Hope what we discussed in the article could help make an informed decision. If you want to know more details, welcome to visit FS.COM.

Related Article:
How to Install Your CWDM MUX DEMUX System?

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Server Cabinet, Network Cabinet, Server Rack and Network Rack Differences

With the increasing demand for computing power and space in the data center, server cabinet, network cabinet, server rack and network rack are often used to hold networking hardware and assemblies in data center. Well, among them, which one matches your needs best? It is thus essential to find the answer.

cable management

Figure 1: cable management

What Are Server Rack And Network Rack?

A commonly used server rack is open frame with mounting rails but no sides or doors. It is applied to accommodate equipments such as servers, storage and monitors. Server racks come in many different shapes and sizes. The width of a server rack is always the same with the standard (traditional) size of 19 inches, while the height and depth can be various. Besides, it has two basic types: 2-post and 4-post rack. As shown in the figure 2:

A network rack is similar to the server rack in sizes and shapes. It is also called relay rack or open rack. It is a metal frame chassis that holds, stacks, organizes, secures and protects various computer network and server hardware devices.

server rack

Figure 2: server rack

There are several advantages of server racks and network racks:

  • Better Air Flow – The rack is just an open structure with no doors, which allows abundant and unobstructed airflow to help to cool the equipment.1
  • Ideal for Cable Management – Since the rack can offer enough open space and easy access, it is convenient for us to install and manage hundreds or even thousands of devices and cables in the open rack.

Despite these advantages, the server rack and network rack have some challenges:

  • Insecurity – Anyone has access to the rack, so the equipment in the rack is lack of security.
  • Exposed to Dust – The equipment mounted on the rack is exposed to the dust, debris and other contaminants, which may cause the equipment damaged over time.

What Are Server Cabinet And Network Cabinet?

A server cabinet, also called an enclosed rack, has removable front and rear doors, side panels and four adjustable vertical mounting rails. The standard data center server cabinet has a height of 42U (73.5 inches high). And for the most part, server cabinets are 24 inches in width, and 36 inches deep. Nowadays, server cabinets have gained much popularity in data centers and server rooms.

A network cabinet is generally used for routers, switches, fiber patch panels and other networking equipments. In most cases, a network cabinet is far shallower than a server cabinet, generally less than 31 inches deep. It sometimes has a glass or a strong plastic front door. What’s more, the network cabinet also commonly do not have perforated enclosures.

server cabinet

Figure 3: server cabinet

Cabinets are popular mainly for the following reasons:

  • More Secure – Unlike the insecure rack, cabinet can provide added protection. The cabinet can be locked, which might avoid visitors or other unauthorized people accessing the equipment.
  • Added More Protection for Cables – With doors and side panels, the cables in the cabinet has much less access to outside air. So it can help the cables to reduce the risk of getting damaged by contaminants.
  • Better of Air Segregation – Server cabinets can be used by engineer to provide a variety of air segregation strategies, for instance, cold aisle containment, hot aisle containment, and cabinet-level containment.

However, there are some disadvantages:

  • High Price – Compared to the rack, cabinet is significantly more expensive.
  • Uneasy Accessibility – Due to the restricted accessibility, it takes more time to do the operation or maintenance of the equipment in a cabinet.


When you are designing a data center, deciding which server rack & cabinet or network rack & cabinet to deploy should be put at the first place. The right one that meets your installation demand can help you improve power protection, cooling, cable management, and physical security. Well, FS.COM offers all of the solutions mentioned above, which can help you maximize the work efficiency and minimize the downtime risks of networks. Welcome to visit fs.com.

Related Article: Proper Vertical Rack Cable Management Solutions

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QSFP-40G-SR-BD Transceiver: An Ideal Option for 40G Ethernet

The demands for higher bandwidth, larger capacity and greater performance in the network are still increasing fiercely. Hence, the migration from 10G to 40G has become a significant and inevitable option for network service providers. Well, this article will recommend an ideal option for you to get 40G Ethernet: QSFP-40G-SR-BD.

QSFP-40G-SR-BD Transceiver Overview

QSFP-40G-SR-BD transceiver, known as a type of QSFP 40-Gbps BiDi transceiver, is a standard QSFP+, MSA compliant optical transceiver. It is designed to work at the wavelength from 832 nm to 918 nm and has a duplex LC interface. What’s more, QSFP-40G-SR-BD transceiver supports the transmission distance of 100m and 150m over a laser-optimized OM3 or OM4 multi-mode fiber (MMF). So this module is commonly used for short-reach data communication.


Figure1: QSFP-40G-SR-BD

Operational Principle of QSFP-40G-SR-BD Transceiver

Bidirectional Optical Sub-Assembly (BOSA) technology is now available that allows components to both transmit and receive optical signals at the same time. By using BOSA, QSFP-40G-SR-BD transceiver can provide two different wavelengths on each fiber transmit 40Gbps data over the traditional 10G MMF cabling.

In the QSFP-40G-SR-BD transceiver, there are four 10Gbps signal channels which are converted to two bidirectional channels of 20Gbps signals. Each 20Gbps signals are transmitted over two different wavelengths (usually 850nm and 900nm). As shown in the following:

qsfp 40g sr bd using duplex LC MMF

Figure2: QSFP-40G-SR-BD using duplex LC MMF

Advantages of SFP-40G-SR-BD 40G Transceiver

  • Easier for upgrading to 40G -With QSFP-40G-SR-BD transceiver, it is easier to rescue existing 10G fiber infrastructure for higher speed 40G cable connections. And you don’t need to upgrade cabling or rewire your data center for larger capacity anymore.
  • Cost-saving – If you set up the 40G data center fabric by a traditional way, you may need much more fibers. Take the 40GBASE-SR4 transceiver as an example, it requires eight fibers for 40G Ethernet. While QSFP-40G-SR-BD transceiver just requires two fibers but can meet the 40GBASE-SR4 performance criteria. So with a QSFP-40G-SR-BD transceiver, there is no need for you to add more fibers.
  • Time saving – As what has been mentioned above, 10G Ethernet is too slow to meet the demand for great performance in the network. With QSFP-40G-SR-BD 40G transceiver, you can get 40G Ethernet, which is faster than before. That is to say, you can save more time to get what you need in the network.


QSFP-40G-SR-BD 40G Transceiver is an ideal and feasible option for 10G Ethernet to 40G Ethernet migration. By using the QSFP-40G-SR-BD 40G transceiver, it is unnecessary to update the fiber infrastructure with high-cost money and long time. FS provides various 40G QSFP BiDi transceivers with cheap price and reliable quality. If you have any needs, welcome to visit FS.COM.

Related Article: 40GE Data Center Cabling Options – Transceivers & Direct Attach Cables

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How Much Do You Know About PoE Powered Switch?

PoE (Power over Ethernet) technology allows network cable to provide both data and power for the PoE-enabled device. It can provide higher power and reduce a lot of power cables during network. And it has changed the current situation of the wireless network. Well, the PoE powered switch plays a crucial role in the PoE technology. So this article will give a clear explanation to PoE powered switch.

What Is PoE Powered Switch?

PoE powered switch is a fiber switch with PoE passthrough which has multiple Ethernet ports to connect network segments. It not only transmits network data but also supplies power via a length of Ethernet network cable, like Cat5 or Cat6. There are two standards for PoE powered ethernet switch. One is 802.3af which provides 15.4 watts of power. The other is 802.3at which provides 25.5 watts. What’s more, most PoE switches offered in the market can provide the speed of 10/100/1000Mbps. And the types of hubs can be classified into 8/12/24/48 port PoE network switch, or unmanaged and managed PoE network switch. Among the various port designs, the 24 port PoE switch is considered as a decent option for both business and home network.

managed 24 port PoE switch

Figure1: managed 24 port PoE switch

Why Use PoE Powered Switch?

PoE powered switch brings many advantages to an installation, so it has become an optimized choice for users. The following are some main advantages of PoE network switch:

  • Flexibility

The PoE network switch is powered through existing PoE network infrastructure and eliminates the demand for additional electrical wiring. Therefore, you can deploy it without an external power adapter. This gives you the flexibility to install the switch exactly wherever you need it.

  • Reliability

Since PoE power comes from a central source and separates from the data signal rather than a collection of distributed wall adapters. There is no interference of the PoE power transmission and data can be backed up by an uninterruptible power supply.

  • Safety

PoE network switch is intelligent and designed to protect network equipment from overload, underpowering, or incorrect installation. It also allows administrators visibility and control.

  • Cost-efficient

With PoE network switch, there is no need for users to purchase and deploy additional electrical wires and outlets. So it make significant savings on installation and maintenance costs.

What Is PoE Powered Switch Used for?

PoE network switch has many network applications. There are three key types of PoE networking architectures:

  • IP Cameras

PoE is now ubiquitous on networked surveillance cameras. It allows each camera to be controlled remotely from any point in the IP camera systems. Besides, it also enables fast deployment and easy repositioning.

  • VoIP Phones

VoIP phone is the most common and original PoE application with a single connection to a wall socket. It can be remotely powered down just like with the older analog systems. With PoE powered ethernet switch, only data network cable is required. PoE network switch has facilitated business communication and reduced deployment costs of VoIP.

  • Wireless Access Points (WAP)

The wireless network is greatly enhanced by the usage of PoE. Data network can be transmitted by running Cat5e or Cat6 network cable from the WAP to the nearest power. And power can be also provided over the same cable. In addition, Wifi, Bluetooth APs, and RFID readers are commonly PoE-compatible. So, these devices allow remote location away from AC outlets, and relocation following site surveys.

PoE powered switch solution

Figure2: PoE powered switch solution


PoE powered switch works as the heart of a PoE network. It saves both time and money for network deployment and maintenance. FS is a good place to go for the reliable and cheap PoE network switch. If you have any needs, welcome to visit FS.COM.

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Single Mode Fiber Comparison: G.652 vs G.655

Single mode fiber is designed as a carrier for the transmission of a single mode of light to propagate at a time. Its specifications are divided into two categories, One is the ITU-T G.65x series, and the other is IEC 60793-2-50 (published as BS EN 60793-2-50). Rather than referring to both ITU-T and IEC terminologies, we’ ll only focus on the simpler ITU-T G.65x in this article. There are 6 different single mode fiber types defined by the ITU-T: G.652, G.653, G.654, G.655, G.656, and G.657, among which G.652 and G.655 are two options commonly used. So what’ s the difference between G.652 and G.655?

Single mode fiber

What is G.652 Single Mode Fiber?

G.652 single mode fiber, also known as standard single fiber, is the most commonly deployed single mode fiber. It has G.652A, B, C and D four variants. The G.652.A and G.652.B are designed to have a zero-dispersion wavelength near 1310 nm, therefore they are optimized for operation in the 1310nm band. However, they are not suitable for applications in Wavelength Division Multiplexing (WDM) due to water peak. The more advanced variants G.652.C and G.652.D fibers are optimized with a reduced water peak for spectrum operation, which allows them to be utilized in the wavelength region between 1310 nm and 1550 nm to support Coarse Wavelength Division Multiplexed (CWDM) transmission.

What is G.655 Single Mode Fiber?

G.655 single mode fiber is also called non zero dispersion-shifted fiber (NZDSF) , because the dispersion at the wavelength of 1550 nm is close to zero but not zero. It contains 655 A, B and C three variants. G.655 fiber optic cable has a small, controlled amount of chromatic dispersion in the C-band (1530-1560 nm), where amplifiers work best, and has a larger core area than G.652 fiber. Besides, there are two types of NZDSF: (-D)NZDSF and (+D)NZDSF. They have respectively a negative and positive slope versus wavelength. The positive dispersion of G.655 can suppress four-wave mixing and other nonlinear effects. Hence G.655 single mode fiber distance is long and transmission capacity is high, it is suitable for DWDM transmission.

Difference between G.652 and G.655

G.652 vs G.655 Single Mode Fiber: What Is the Difference?

G.652 and G.655 differ in several specifications, for example, wavelength, dispersion, the parameter of attenuation and PMD, division and so on. Unlike G.652 which has a zero-dispersion wavelength at 1310 nm and reduced water peak to support CWDM, G.655 fiber is a non-zero dispersion-shifted fiber with the characteristics of elimination of FWM and low dispersion value,  applied to DWDM. When it comes to the fiber optic cable price, G.652 is lower than G.655. Besides, there are other detailed differences between G.652 and G.655 in the following table.

Single Mode Fiber Difference


This article gave an explanation of two categories of single mode fiber types and made a comparison between G.652 and G.655. If you need the transmission with not very high rate and long distance, G.652. D is recommended. If you need the DWDM system required much higher capacity and long distance, G655 can be the best choice regardless of much higher cost. For more detailed information about single mode fiber, you can contact fs.com.

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SFP-10G-SR vs X2-10G-SR: Which One to Choose?

The 10G transceiver is considered as the mainstream module in the market due to its mature technology and low price. There are various types of 10G transceiver modules like 10GBASE SR10GBASE LR, etc. SFP-10G-SR and X2-10G-SR are two very popular 10GBASE SR optical transceivers, which offer customers a wide variety of 10 Gigabit Ethernet connectivity options for data center, enterprise wiring closet, and service provider transport applications. Here, we will make a comparison between SFP-10G-SR and X2-10G-SR.

What is SFP-10G-SR?

SFP-10G-SR belongs to 10GBase SR SFP+ transceiver modules family. It has the industry’s smallest 10G form factor and the highest density of each chassis. As a hot-swappable module, it can be plugged into the Ethernet SFP+ port on a Cisco switch without the need to power down the host network system. Besides, it provides 10GBase SR throughput up to 300m over laser-optimized OM3 multi-mode fiber (MMF). This module has LC duplex connector operating over 850nm for short reach. In addition, minimum cabling distance for SR modules is 2m, according to the IEEE 802.3ae.


What is X2-10G-SR?

The X2-10G-SR is a highly integrated 10GBase SR module for high-speed 10Gbit/s data transmission applications. It is a hot-pluggable 70-pin connector with XAUI electrical interface. X2-10G-SR is Designed for 300m transmission distance over multi-mode fiber with a vertical cavity surface emitting laser(VCSEL). It has SC duplex connector operating over 850nm for short reach. The operating case temperature standard is from 0℃ to 70℃. What’s more, X2-10G-SR is compatible with X2 MSA Rev.2.0b and SFF-8724 Digital optical monitoring.


SFP-10G-SR vs X2-10G-SR

SFP-10G-SR and X2-10G-SR have many similarities, for instance, they support 10 Gigabit Ethernet, provide a link length of up to 300m on multi-mode fiber, deliver serialized data at a line rate of 10.3125 Gbit/s, have the same receiver sensitivity and TX power and so on. However, these two transciver modules still differ in some aspects.


Obviously, X2-10G-SR is paired with SC duplex connector interface with MMF while SFP-10G-SR has LC duplex connector with MMF. So it is a very important distinction for you to consider choosing the right transceiver modules. If you want to buy a 10G transceiver module with LC connector, SFP-10G-SR might be an ideal choice.


Although different vendors may make the different price of SFP-10G-SR and X2-10GB-SR transceivers. In general, the SFP-10G-SR price is lower than the X2-10GB-SR.


Both SFP-10G-SR and X2-10GB-SR are intended for 10 Gigabit Ethernet deployments in diverse networking environments. But the former can also be applied in 10GBASE-EW at 9.95Gbps, 1000 Base-LX Ethernet, 8x FC at 8.5Gbps, 4x FC at 4.25Gpbs, 2x FC at 2.125Gpbs and other optical links.

Module Type

SFP-10G-SR is with SFP+ transceiver package and are used in SFP compatible slots. While X2-10GB-SR is with X2 package and used in X2 compatible slots.


After the comparison of SFP-10G-SR vs X2-10GB-SR, we can see that each one has its own set of advantages and disadvantages. In fact, it totally depends on your actual needs. As a reliable and qualified fiber optics supplier, FS is your ideal choice for compatible transceivers. Kindly contact fs.com for more details if you are interested.

Related Article: A Comprehensively Understanding of Cisco 10G SFP+

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Understanding Ports on CWDM MUX/DEMUX

WDM (Wavelength Division Multiplexing) is a commonly used technology in optical communications. CWDM and DWDM MUX/DEMUX are two important components in WDM systems, which are often deployed to join multiple wavelengths onto a single fiber. There are some ports on CWDM and DWDM MUX/DEMUX like channel port, line port, monitor port, etc. This article will focus on discussing the functions of ports on CWDM MUX/DEMUX.

CWDM MUX ports


CWDM MUX/DEMUX (Coarse Wavelength Division Multiplexer/Demultiplexer) is a flexible, low-cost solution that enables the expansion of existing fiber capacity. CWDM multiplexer is for combining signals together, while demultiplexer is for splitting signals apart. The wavelengths used in CWDM implementations are defined by the ITU-T G.694.2, listing 18 wavelengths from 1270nm to 1610nm with a channel spacing of 20 nm. CWDM Multiplexer/Demultiplexer is designed to support a broad range of architectures, ranging from scalable point-to-point links to two fiber-protected rings.

Common Ports on CWDM MUX/DEMUX

For CWDM MUX/DEMUX, channel port and line port are the most common and necessary ports for normal operation of the CWDM Multiplexer/Demultiplexer.

Channel Port

A CWDM MUX/DEMUX usually has several channel ports on different wavelengths. Each channel port works for a specific wavelength. It  uses 18 wavelengths ranging from 1270nm to 1610nm with a channel space of 20nm. The number of channel ports on CWDM Multiplexer/Demultiplexer is usually ranging from 2 to 18.

Line Port

Line port of CWDM MUX/DEMUX can be divided into dual-fiber and single-fiber types. The wavelengths’ order and the applications of them are totally different. Dual-fiber line port is used for bidirectional transmission, which means the TX port and RX port of every duplex channel port supporting the same wavelength. The CWDM MUX/DEMUX with dual fiber line ports installed on the two ends of the network could be the same. However, single-fiber line port only supports one direction data flow, thus the transmit and receive port of the duplex channel will support different wavelengths. The wavelengths’ order of single-fiber CWDM Multiplexer/Demultiplexer should be reversed at both sides of the network.

Ports on CWDM MUX

Special Ports on CWDM MUX/DEMUX

Except for the common ports, some special ports can also be found on CWDM MUX/DEMUX for particular needs.

1310nm Port and 1550nm Port

1310nm and 1550nm ports are certain wavelength ports. The port can be used to combine an existing legacy 1310nm or 1550 nm network with CWDM channels, allowing the CWDM channels to be overlaid on the same fiber pair as the existing 1310nm or 1550 nm network. Besides, the wavelengths which are 0 to 40 nm higher or lower than 1310 nm or 1550 nm cannot be added to the device. Many optical transceivers, especially the CWDM SFP/SFP+ transceiver, use these two wavelengths for a long-haul network.

Expansion Port

Expansion port is used to add or expand more wavelengths or CWDM channels to the network.  It means that when a CWDM MUX/DEMUX cannot meet all the wavelength needs, it is convenient to use the expansion port to add different wavelengths by connecting to another CWDM Multiplexer/Demultiplexer line port. However, not every CWDM MUX/DEMUX has an expansion port.

Monitor Port

Monitor port is used for signal monitoring or testing. If you choose a single-fiber CWDM MUX/DEMUX, the monitor port should be a simplex fiber optic port. For a dual-fiber MUX/DEMUX, you can add a duplex or a simplex monitor port for the whole network monitoring.


The common ports and the special ports on CWDM MUX/DEMUX all have their own features and application. Certainly, CWDM Multiplexer/Demultiplexer is a popular technology which can provide cost-effective solutions for users to upgrade their network. FS.COM supplies various types of CWDM MUX/DEMUX, for instance, dual fiber, single fiber, and 4/8/9/18channels. All the above-mentioned ports especially the special ports can be customized for your preference. If you have any needs, welcome to visit FS.COM.

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