Fiber Optic Blog

SFP cable, also known as 10G SFP+ cable, SFP+ DAC twinax cable or SFP+ AOC cable, is a form of high speed cable with Small Form Factor Pluggable Plus on either end. They are suitable for in-rack connections between servers and switches. SFP cable’s popularity can be attributed to that Cat5e copper cabling and 1000BASE-T have dominated data center interconnection application for years, however, the upgrading to 10GE, 40GE and beyond poses a significant hindrance in both power consumption and cost. At this point, 10G SFP+ direct attach copper swoops in and becomes a new favor of Top of rack switching.

What Is SFP Cable?

SFP twinax cable which replaces two optical modules and a connectorized optical fiber with a twinaxial copper cable assembly offers the higher density, lower cost, and lower power 10 Gigabit Ethernet solution than other cable types such as 10GBASE-CX4 and CAT6/CAT6A 10GBASE-T. The SFP cables can be classified to 10G SFP+ DAC cable and 10G SFP+ AOC cable. SFP+ AOC features longer transmission distances(>100m), isolation from signal interference and crosstalk and higher signal transmission capacities but it’s more expensive than SFP+ DAC. SFP+ DAC consists of active DAC and passive DAC. Passive DAC cables have no signal amplification built into the cable assembly hence for ultra short reach(<5m), whereas active DAC cables have signal amplification and equalization built into the cable assembly for a litter longer reach(5-15m) in the same time with a higher price.

SFP Cable: 10G SFP+ Cable vs. 25G SFP28 Cable

We’ve already known that SFP+ is made to operate at 10Gb/s. And SFP28, as the enhanced version of SFP+, is designed for 25G signal transmission. SFP28 utilizes the same familiar form factor as SFP+, but the electrical interface is upgraded to handle 25Gbps per lane. To put it simply, 10G SFP+ cable and 25G SFP28 cable just has the same form factor but with different speed. What’s more, 25G SFP ports can support a full range of 10G SFP+, which means 10G SFP+ cable can be plugged into 25G SFP ports.

How SFP Cable Is Used?

As 10G network is widely deployed in today’s data center, 10G SFP cables are commonly used in interconnect applications below 100m, such as server to switch or storage to switch interconnection in the same rack (Shown in the below picture). And now 25GbE is popular and 25G direct attach cable assemblies, such as SFP28 DACs, are already available in the market. For 40GbE, 40G QSFP+ DACs and AOCs are used. Of course, higher speed and more bandwidth are needed for spine switches. Thus, 100G DACs, like QSFP28 DACs are used in this case.

Conclusion

With the convenience of plug and play technology, fiber-mart.COM’s family of 10G SFP cable delivers throughput that exceeds those of industry standards. Besides, they also offer a variety of high speed interconnect DAC assemblies including 40G/56G QSFP+ cable, and 100G QSFP28 cables to satisfy the demands from 10G to 100G interconnection. All of direct attach copper cables can meet the ever growing need to cost-effectively deliver more bandwidth, and can be customized to meet different requirements.

40G network is gradually being applied in today’s backbone transmission network, during which long distance transmission is required. 40G QSFP+ SR4 fiber optic transceiver is being widely applied for 40G transmission in short distances. Generally, 40G QSFP+ SR4, working on wavelength of 850 nm, can support 40G fiber optic transmission a distance up to 150 m over OM4 multimode optical fiber. Inserted in switch, QSFP+ SR4 module utilizes a MTP/MPO interface for dual way transmission. There are a lot of methods to connect QSFP+ SR4 transceivers with other devices for different applications, by using different connectivity products. In addition, the cabling for 40G is relatively more difficult than that of 10G network, which requires more cables and spaces. The following will introduce several high density QSFP+ SR4 transceiver cabling methods.

QSFP+ SR4 40G to 40G Applications

40G to 40G transmission is needed in a 40G fiber optic network. The following picture simply illustrates how 40G to 40G multimode transmission is being achieved by QSFP+ SR4 transceivers. Two QSFP+ SR4 modules are separately inserted in two 40G switches. Then the two transceiver are connected by a length of multimode MTP trunk cable. This is the simplest way to use QSFP+ SR4 transceiver.

In some cases, there are lot of 40G connections required at the same time and same places, which means the increasing of both cable count and cabling difficulty. For better cable management and higher density cabling, a 48-port 1U rack mount MTP fiber patch enclosure can be used as shown in the following picture. Up to four 12-port MTP fiber adapter panels can be deployed in this standard 1U rack mount enclosure. With the help of this 48-port MTP fiber enclosure, cable management for 40G connections could be easier.

QSFP+ SR4 40G to 10G Applications

QSFP+ SR4 is a parallel fiber optic transceiver which means it uses four fibers for transmitting and four fibers for receiving at the same time. The 40G fiber optic signal can be separated into four 10G signals to meet the 40G to 10G transferring requirements. The fiber optic cable count will be increased at the 10G distribution end. Usually a breakout MTP-8LC harness cable is used. For better cable management, a 1U 96-fiber enclosure is recommended, which includes four HD MTP cassettes transferring MTP front the 40G end to LC at the 10G end. Four 10G-SR SFP+ modules, inserted in 10G switch/ports, can be connected to the corresponding LC ports on this fiber enclosure to achieve the duplex transmission between 40G and 10G.

For higher cabling density, the above mentioned 48-port 1U rack mount MTP fiber patch enclosure is still being recommended, which can provide high density 40G MTP cabling environment. And additional MTP-8LC harness cables should be used for transferring signals between 40G and 10G (shown in the following picture).

Conclusion

Depending on its parallel transmission mode, QSFP+ SR4 modules can meet a variety of cabling applications with great flexibility. The above methods is just several commonly used ones, detailed cabling methods for QSFP+ SR4 modules are depended on the practical applications and cabling environments. Related products for the above mentioned methods are listed in the following tables. Kindly visit fiber-mart.COM or click the attached links for more details. You can also contact sales@fiber-mart.com for more information about 40G cabling.

DWDM network has been widely accepted as the most cost-effective and feasible solution to increase the fiber optic network capacity over long distance. Except the bandwidth, the transmission distance is also an important factor during the deployment of DWDM network. This post is to introduce how to ensure and extend the transmission distance in DWDM network.

Proper DWDM Fiber Optic Transceiver Is Essential

Generally, the fiber optic transmission distance is affected by the data rate, light loss, light source, etc. During the deployment, technicians usually need to select proper fiber optic transceivers to ensure the light source is strong enough to support the long transmission distances. For instance, 1G DWDM SFP modules provided by the market can usually support transmission distance up to 100km, while for 10G DWDM SFP+ modules this distance decrease to 80km. If the longer transmission distance is to achieve, proper fiber optic devices should be added in the DWDM network to ensure the transmission quality. The following part will take the examples of 10G DWDM network which uses DWDM SFP+ modules supporting transmission distance up to 80km on both ends of the fiber link. This 10G DWDM network will be required to support fiber optic links up to 40km, 80km, 120km and 200km separately.

Case Study One: 40km DWDM Network

In this first case, this 10G DWDM network is required to support 40km transmission distance. As we are using the 80km DWDM SFP+ modules, if there are no other locations deployed between the two ends of this network, generally no other devices are required to be installed between the two DWDM MUX/DEMUXs. The light source of 80km DWDM SFP+ modules can support 10G transmission over 40km.

Case Study Two: 80km DWDM Network

If this DWDM network is required to support 80km transmission distance, we will still use the 80km DWDM SFP+ modules. The light source of these 80km DWDM SFP+ modules might not be able to support such long transmission distance, as their might have light loss during transmission. In this case, pre-amplifier (PA) is usually deployed before the receiver to improve the receiver sensitivity and extend signal transmission distance. Meanwhile, the dispersion compensation module (DCM) can be added in this link to handle the accumulated chromatic dispersion without dropping and regenerating the wavelengths on the link. The following diagram shows the deploying method of this 80km DWDM network.

Case Study Three: 120km DWDM Network

It is known that the light power will decrease with the increasing of transmission distance. More fiber optic devices should be added in the 120km DWDM network to amplify the optical signal transmission from the 80km DWDM SFP+ modules. The following diagram shows how to deploy this 120km DWDM network. Except the above mentioned pre-amplifier and dispersion compensation module, a booster EDFA (BA) is suggested to deploy before at the beginning of the transmitting side to further ensure optical signal can achieve 120km.

The above cases just simply illustrate the deployment of 40km, 80km and 120km 10G DWDM network that uses 80km DWDM SFP+ modules as light source. Related products in the above mentioned cases are listed in the following table. Please note that during the deployment of these long haul DWDM network, the light loss and compensation dispersion should be well calculated.

fiber-mart.com.COM Long Haul DWDM Solution

In fact, DWDM technologies and products can achieve transmission distance much longer than 120km, like 170km DWDM and 200km DWDM. If you are interested, kindly visit our Long Haul DWDM Network page where you can find specific details for complete DWDM network deployment solutions.

LC-LC patch cable has already become the main force of high density cabling network infrastructure. To future increase the profits of LC-LC fiber patch cable, manufactures has invented LC-LC patch cables of different features to meet various requirements in data center and increase the network performance.

What Kind of Fiber Patch Cable Is Required in Data Center?

Data center is a place of thousands fiber links. The selection of fiber patch cables will directly affect the network performance. More and more data centers choose to select fiber patch cable of high performance. Generally, insertion loss and return loss of connectors terminated on patch cable and light loss of optical fiber used for fiber patch cable are three most basic factors for fiber patch cable selection. To satisfy the increasing demands for higher density and easier management in data center, the optimization of fiber patch cable has never stopped. The following introduces several popular LC-LC fiber patch cables which represent the trends of fiber patch cable that data center is asking for.

Low Insertion Loss and Bend Loss LC-LC Patch Cable

When a length of fiber patch cable is connected in network, optical light loss occurs at the optical fiber and the connectors terminated on it. There are different optical light losses, among which insertion loss at the connectors and bend loss in fiber optic cables are the two most commonly light losses that technicians are trying to overcome. Manufactures provides LC-LC fiber patch cables which can minimize these losses to the most.

Insertion loss refers to the fiber optic light loss caused when a fiber optic component insert into another one to form the fiber optic link. To provide low insertion loss patch cable, LC connectors terminated on the patch cable has been optimized. Standard LC-LC patch cable usually has an insertion loss less than 0.3 dB. However, for upgraded LC-LC patch cable, the insertion loss is usually lower than 0.2 dB. To decrease the bend loss, a type of bend insensitive fiber (BIF) has been used in fiber patch cable. With optimized LC connectors and bend insensitive fiber, LC-LC fiber patch cable could provide lower light loss during network transmission.

High Density LC-LC Patch Cable

LC connector was invented for higher cabling density. standard duplex LC-LC fiber patch cable can provide much higher cabling density than other duplex fiber patch cables. To further increase cabling density in data center, the connectors and cable diameter of LC-LC patch cable are becoming smaller. Uniboot LC-LC patch cable is a typical example. This kind of fiber patch cable designed the two fibers of the duplex patch cable into a single cable. In adding the two connectors terminated at each end of the duplex patch cable share the same boot. With less using cable counts, uniboot patch cable can provide higher cabling density and better cooling environment in data center.

Polarity Switchable LC-LC Patch Cable

The development of patch cable won’t stop at low loss and high density. Making fiber patch cable easier-to-use is also important. Polarity of fiber patch cable matters a lot during installation of fiber patch cable, especially for duplex fiber patch cable and MTP patch cable. It is common to change the polarity of a duplex patch cable during deployment. Technicians might need tools to change the polarity of patch cable. However, a polarity switchable LC-LC patch cable can make things much easier. Without any tools you can polarity reversal could be really easy. The following picture shows the polarity reversal of a special designed LC-LC patch cable.

Conclusion

LC-LC patch cable has been designed into many different types. A high performance fiber patch cable should not only provide low insertion loss and bend loss, but also higher cabling density and easy-to-use features. This is also the trend of data center development.

Due to the rapid increase of communication traffic, the requirement for core networks to handle larger capacity and longer distance on their links has led to a spread of 100G optical networks. For this environment, service providers are adopting coherent transceivers for their 100G DWDM backbone applications. Until recently, coherent CFP/CFP2 DWDM optical transceivers had been the technology of choice for transporting 100G traffic over long distances or as part of a DWDM network. This paper will mainly discuss 100G coherent CFP module for metro network application.

Coherent Technology: Making 100Gb/s Available

Moving from 10Gb/s to 100Gb/s line speeds comes with technical challenges. Coherent technology had been investigated for optical transmission since the 1980s as a means to increase transmission distances. By 2010 to 2011, the technology had reached a point of market maturity. At this time, it could genuinely allow 100G coherent signals. This result forms the foundation of the industry’s drive to achieve transport speeds of 100G and beyond, which helps to deliver Terabits of information across a single fiber pair at a lower cost. Until now, coherent technology has been mainly deployed in long-haul networks, and it is now starting to be deployed in metro networks.

Metro Requirements for 100G

100G rates were initially deployed in the long-haul and core networks. In the Metro, 10G is still the most dominant rate. In the coming years, the trend toward aggregation into 100G in the larger metro areas or data center connectivity will become more significant. The metro covers a broad range of distances: the metro regional and metro core cover distances of 500-1000 km and 100-500 km respectively, while the metro access links are generally point-to-point connections shorter than 100 km. Although these distances are shorter than long-haul links, the characteristics of metro network- including flexible protocol support, higher granularity of signal rates and increased number of nodes- create the requirements for 100G rates.

100G Coherent CFP Module for Metro Network Applications

While metro and long haul applications have different requirements, the lower-cost 100G technology for the metro is demanded for service providers. To achieve this feat, equipment vendors consider coherent CFP modules as the ultimate solutions for metro 100G deployments. Coherent 100G CFP can overcome optical transmission impairments and still achieve acceptable performance.

since the 100G rates are more susceptible to dispersion, they would require extra dispersion compensation and optical power boost. Thus an extra 100GHz DWDM multiplexer is first used to combine all the 100G rates together followed by a combined dispersion compensation and amplification stage. This architecture conveniently supports the ‘pay-as-you-grow’ model for service providers. When the bandwidth is exhausted, the existing legacy 10G channels may be seamlessly interchanged with 100G services. The same remaining components can even be reused to extend the data rate up to 2.4 Tb/s.

This scenario would require 24 differently colored CFP modules deployed together with the already existing 48 channel 100 GHz DWDM multiplexer. All the 100G services are first multiplexed together such that only one dispersion compensation and amplification stage suffices. Clearly, such a network architecture provides higher density with capability to reuse existing infrastructure with flexibility while remaining cost friendly.

In this scenario, the switch was tested with SFP+ OEO transponders for simple distance extension solutions. The 100G output signals from the switch are converted to DWDM signals that can be transmitted over longer distance. The solution removes the distance limitations by using a coherent CFP module to connect the output signal to the line fiber and carry the signal over longer distances.

to achieve higher cabling density with Cisco CFP 100G optics, the architecture mixed a 16 channels dual fiber DWDM Mux Demux which can be used for CWDM/DWDM hybrid and 8 channels dual fiber CWDM Mux Demux, by adding MTP harness cable and WDM SFP+ OEO converter to transfer the regular SR wavelength to DWDM wavelengths. Therefore, building a long distance 2500km DWDM networks in 100G coherent CFP modules and cost effective way will be achieved.

Conclusion

100G coherent CFP modules provide cost-effective electronic equalization of fiber impairments and extensive performance monitoring capabilities that enable easy installation and network management. These benefits help service providers meet bandwidth demand growth while reducing the total cost of ownership.

10G connection in telecommunication network is gradually moving from the backbone to layer 2 and layer 3. Both technology and market of 10G SFP+ transceiver modules are mature: the 10G transceiver modules have advanced from XENPAK which is the first generation of 10G transceiver to SFP+ which is now the most popular 10G optics. In addition, the price of 10G modules is getting lower. 10G modules are becoming affordable. Some genius guys even buy 10 SFP+ modules online to DIY private point to point 10G network. This article will offer basic information about 10G SFP+ transceiver modules and their connection instructions.

Basic of 10G SFP+ Transceiver Module

10G SFP+ transceiver has the same form factor of Gigabit SFP transceiver. Thus, many 10G modules can support 1/10G data rate to increase its flexibility during practical using. A SFP+ transceiver usually has two LC ports (as shown in the following picture). While 10G BiDi SFP+ transceiver, which transmitting and receiving signals from the same fiber optic cable, only has one LC port.

Except fiber optical transceivers, there are also various factory terminated copper-based or fiber optic based cables which are terminated with a SFP+ module on each end of the cable. There are mainly three types of these 10G cables: 10G SFP+ passive direct attached copper cable, 10G active direct attached copper cable and 10G SFP+ active optical cable. These 10G SFP+ cables eliminate the used of additional patch cable and can be directly plugged into the 10G SFP+ ports on switches. It is acceptable that these cables are an cost-effective and reliable solutions for 10G connections in short distance.

Optical Standards of 10G SFP+ Transceiver

According to IEEE standards, there are a variety 10GBASE SFP+ transceivers. For short distance transmission, 10GBASE-SR SFP+ and 10GBASE-LRM SFP+ can support transmission distance up to 300 meters and 220 meters over multimode fiber optic cables separately. 10GBASE-SR SFP+ modules is the most commonly used transceiver for short distance. It is suggested to work over wavelength of 850 nm.

There are a lot of 10G SFP+ transceivers that support long distance, like 10GBASE-LR SFP+, 10GBASE-ER SFP+, 10GBASE-ZR SFP+, CWDM SFP+, DWDM SFP+, BiDi SFP+, etc. These transceivers can support transmission distances ranging from 10 km to 120 km over single-mode fiber optic cables.

There is another special type of 10G transceivers which has been mentioned in this post, which is known as dual-rate SFP+. For example, dual-rate 1000BASE-LX and 10GBASE-LR SFP+ transceiver can be adjusted to support both 1G and 10G data rate up to 10 km over wavelength of 1310 nm.

Fiber Patch Cable Selection Guide for 10G SFP+ Transceivers

As 10G SFP+ DAC and AOC eliminate the using of additional patch cords. This part will introduce the selection guide for 10G SFP+ transceivers. During the selection of fiber optic patch cables for 10G SFP+ transceivers, the transmission distance is the first element to be considered. Single-mode patch cable is used for long distance transmission and multimode is designed for short distance transmission. Then the ports on the transceiver for receiving and transmitting should be considered. As mentioned, most 10G transceiver use duplex LC port, while BiDi SFP+ use simplex port (as shown in the above picture). Thus, simplex LC patch cords or duplex LC patch cords are used according to the port type on the transceiver. The following chart introduces detailed cabling information for 10G SFP+ transceivers.

This post just introduced the basic information of 10G optics and cabling information. For more specific information, please visit fiber-mart.COM, where you can find a variety of 10G SFP+ optics modules.