40G Parallel & Bidirectional Optical Transceiver Introduction

by http://www.fiber-mart.com

Speeds in data centers have maintained their growth in the past years, and will continue to do so in the predictable future. High-data-rate systems have become increasingly popular among some enterprises for high-performance computing networks, such as 40 Gigabit Ethernet (GbE) infrastructure, in which 40G fiber optic transceivers and cables are needed to ensure the high-performance and great-bandwidth of the 40GbE system. This article mainly introduces 40G fiber optic transceivers: the pluggable optical Enhanced Quad Small Form-Factor Pluggable (QSFP+), with focus on the bidirectional optical transceivers and parallel optical transceivers.

40G Optical Transceiver Types

The transceiver is an electronic device that receives an electrical signal, converts it into a light signal, and launches the signal into a fiber. It also receives the light signal, from another transceiver, and converts it into an electrical signal. With the 40G QSFP being the dominant transceiver form factor used for 40GbE applications, the IEEE standard 802.3ba released several 40-Gbps based solutions in 2010, including a 40GBASE-SR4 parallel optics solution for multi-mode fiber (MMF). Another solution is a bidirectional 40-Gbps transceiver that uses a two-fiber LC optical interface.

40G Parallel Optical Transceiver

40G parallel optical transceiver enables high-bandwidth 40G optical links over 12-fiber parallel fiber terminated with MPO/MTP connectors. Four fibers on one side are used to transmit, while another four on the other side are utilized to receive, leaving the middle four fibers unused. In total, eight of the twelve fiber are used. That is to say, when used for 40GBASE-SR4 and 40GBASE-CSR4, parallel optical transceiver has 10-Gbps electrical lanes that are mirrored in the optical outputs, causing the requirement of eight fibers with a MTP connector interface. Each fiber either transmits (Tx) or receives (Rx) 10-Gbps traffic at a single wavelength.

Just as mentioned above, 40GBASE-SR4 QSFP+ transceiver belongs to 40G parallel optical transceivers, which uses multi-mode MPO trunks to establish 40G links. This port type 40G QSFP+ module can support link lengths of 100 meters and 150 meters over laser-optimized OM3 and OM4 MMFs respectively. It can also be used to connect with four 10GBASE-SR optical interfaces using an 8-fiber MTP to 4 duplex LC cable. fiber-mart.com listed 40GBASE-SR4 optical transceivers are fully compatible with such famous brands, as Cisco, Intel, Juniper (QFX-QSFP-40G-SR4), and so on. All are quality-and compatiblity-assured, offering the high performance to customers.

40G Bidirectional Optical Transceiver

By contrast, 40G bidirectional optical transceiver consists of two 20-Gbps transmit and receive channels, enabling an aggregated 40-Gbps link over a two-strand MMF connection. That is, the bidirectional optical transceiver used for 40GBASE-SR-BD uses the same 10-Gbps electrical lanes, which are then combined in the optical outputs, thus requiring two fibers with an LC connector interface. Each fiber simultaneously transmits and receives 20-Gbps traffic at two different wavelengths.

Just as mentioned above, 40GBASE-SR4 QSFP+ transceiver belongs to 40G parallel optical transceivers, which uses multi-mode MPO trunks to establish 40G links. This port type 40G QSFP+ module can support link lengths of 100 meters and 150 meters over laser-optimized OM3 and OM4 MMFs respectively. It can also be used to connect with four 10GBASE-SR optical interfaces using an 8-fiber MTP to 4 duplex LC cable. fiber-mart.com listed 40GBASE-SR4 optical transceivers are fully compatible with such famous brands, as Cisco, Intel, Juniper (QFX-QSFP-40G-SR4), and so on. All are quality-and compatiblity-assured, offering the high performance to customers.

40G Bidirectional Optical Transceiver

By contrast, 40G bidirectional optical transceiver consists of two 20-Gbps transmit and receive channels, enabling an aggregated 40-Gbps link over a two-strand MMF connection. That is, the bidirectional optical transceiver used for 40GBASE-SR-BD uses the same 10-Gbps electrical lanes, which are then combined in the optical outputs, thus requiring two fibers with an LC connector interface. Each fiber simultaneously transmits and receives 20-Gbps traffic at two different wavelengths.

Cabling Options for 40G Parallel & Bidirectional Optical Transceiver

Cabling Options for 40G Parallel Optical Transceiver

As previously mentioned, in 2010 IEEE 802.3ba approved the 40GBASE-SR4 physical-medium-dependent (PMD) multi-mode parallel optic solution, which uses eight fibers to transmit four duplex channels each at 10-Gbps. This is an economical path to 40GbE data rates, while using many of components of 10GbE solutions. The main advantage of the parallel optical transceiver over the bidirectional transceiver at 40GbE is the reach. For example, if you cable your data center with OM3 at 10GbE, you can support distances up to 300m. Then if you move to 40GbE, you can support the same 300m distance with the same OM3 fiber and a 40GBASE-CSR4 transceiver. However, if your cabling distances do not justify the extra distance capability, then the bidirectional solution would be used.

There exists a problem in this parallel optical cabling solution—MTP cable assemblies which built on 12-fiber position connectors, leaving four unused fibers in each link. There are several basic cabling options for parallel optics connectivity. One approach is to ignore the unused fibers and continue to deploy 12 fibers. Another approach is to use a conversion device to convert two 12-fiber links into three 8-fiber links.

Cabling Options for 40G Bidirectional Optical Transceiver

This two-fiber 40G bidirectional multi-mode solution tackles the challenge—polarity correction that occurs in a 12-fiber MTP connector., using two different transmission windows (850 and 900nm) that are transmitted bidirectionally over the same fiber. This approach allows the use of the same cabling infrastructure for 40GbE as was used for 1 and 10 Gigabit Ethernet. The pluggable bidirectional transceiver has the same QSFP+ format as the existing 40GBASE-SR4 transceivers. Therefore, the same switch line card with QSFP+ ports can support either parallel optics 40GBASE-SR4 or bidirectional optics 40GBASE-SR-BD solutions.

As such, while connecting a 40GbE bidirectional transceiver to another bidirectional transceiver, a Type A-to-B standard LC duplex patch cord can be considered, with one fiber in connector position A on one end and in connector position B on the other end. Such reverse fiber positioning allows a signal to be directed from the transmit position on one end of the network to the receive position on the other end of the network. However, this direct connectivity is recommended only within a given row of cabinets.


40G QSFP+ transceivers can meet the growing data center applications, such as big data and high-frequency trading (HFT) applications, and virtualized and clustered environments. With 40G bidirectional optical transceivers, no big changes to the existing cabling infrastructure are required, a cost-effective way for migration from 10-Gbps to 40-Gbps connectivity in data center networks. As a professional fiber optical product manufacturer and supplier, fiber-mart.com offers various 40G QSFP+ transceivers for your choice. Besides, many 40G cables (ie. QSFP-4SFP10G-CU5M) are also available for the smooth migration. For more information about 40GbE solutions (40G QSFP+ and 40G cables), you can visit fiber-mart.com.

SMF&MMF 40G QSFP+ Transceiver Overview

by http://www.fiber-mart.com

The demand for better network throughput and performance has never ceased. Instead, it has become more and more vigorous. The server consolidation, virtualization, as well as networking-service performance improvements, all these have pushed the necessity for dense 40GbE switch connections in data centers.

But when migrating to 40GbE from10GbE, some companies or organizations are challenged by two main factors in re-configuring the physical layer of the network: firstly, the possible reduced reach of the OM3/OM4 multi-mode optics from 10GBASE-SR (300/400 m) to 40GBASE-SR4 (100/150m), and secondly, the need to upgrade the existing fiber optic cabling plant so as to support the IEEE-defined 40GBASE-SR4 parallel optics. In order to avoid these questions, SMF&MMF 40G QSFP+ transceiver is brought to the market.

SMF&MMF 40G QSFP+ Transceiver Definition

It’s know that a fiber optic transceiver may either operate on single-mode fiber (SMF) or multi-mode fiber (MMF). However, this SMF&MMF 40G QSFP+ transceiver is able to communicate with both SMF and MMF, without the need for any software/hardware changes to the transceiver module or any additional hardware in the network. It has 4 channels (1270, 1290,1310, and 1330nm) of 10G multiplexed inside the module to transmit and receive an aggregate 40G signal over 2 strands of fiber with a duplex LC connector.

Based on IEEE defined 40GBASE-LR4 specifications, this supports distances up to 150m over OM3 or OM4 MMF and up to 500m over SMF. Certainly, different fiber optic equipment vendors may have different specifications.

SMF&MMF 40G QSFP+ Transceiver Advantages

SMF&MMF 40G QSFP+ transceiver is designed for seamless migrations from existing 10GbE to 40GbE networking without modification or expansion of the fiber network. It addresses several challenges faced by today’s data centers and the passages highlight the advantages of this transceiver.

No Redesign or Expansion of Fiber Network

Other short-reach 40G QSFP+ transceiver types, such as MMF 40GBASE-SR4 transceivers (100m over OM3 MMF), utilize four independent 10G transmitters and receivers for an aggregate 40G link. These 40GBASE-SR4 transceivers (eg. JG325B) use a MPO-12 connector and require 8-fiber parallel OM3 or OM4. As a result, customers installing MTP/MPO fiber systems may need to deploy new fiber while upgrading from 10G to 40G. However, SMF&MMF 40G QSFP+ transceiver uses duplex LC connector, which is consistent with the existing 10G connections. It works on existing OM3 and OM4 MMF infrastructure which is widely installed and used for 10GbE networks, thus free from redesign or expansion of the fiber network.

Increase in the Number of 40G Links

The existing MMF 40GbE solutions use of 8 fibers for a 40G link, and customers have to add additional fiber if they want to increase the number of 40G links. But if you deploy SMF&MMF 40G QSFP+ transceiver, the number of 40G links is 4our times of that existing MMF 40GbE solutions without any changes to their fiber infrastructure. During this link increase, the network scale and performance are also expanded.

A Cost-effective Solution for SMF Infrastructure

Limited in the distance reach that multi-mode transceivers can support, the migration from 10G to 40G, to 100G, or even 400G would become simpler with SMF. But single-mode transceivers typically cost up to 4 times more compared to multi-mode transceivers. Since SMF&MMF QSFP+ transceiver interoperates with QSFP-LR4 and QSFP-LR4L optics, it’s a cost effective solution for SM fiber infrastructure for distances up to 500m. And customers can deploy mixed connections without fiber concerns.

Simplification in Infrastructure Deployment

SMF&MMF QSFP+ transceiver boasts of the unique characteristic of working through both SMF and MMF without any requirement for additional fiber. Customers can consolidate their optics and use SMF&MMF QSFP+ transceiver in their network without concern about the fiber type, which makes the full use of existing cabling infrastructure, leading to the reduced equipment cost and simplification of deployment.


SMF&MMF QSFP+ transceiver allows data centers to migrate from 10GbE to 40GbE without redesigning or modifying the cabling infrastructure, providing companies or organizations a cost-effective solution to expand their fiber network. With SMF&MMF QSFP+ transceiver in hand, a smooth 40GbE migration at low cost is around the corner. fiber-mart.com SMF&MMF 40G QSFP+ transceivers are supplied to help you achieve smooth 40G migration. Besides, their interoperate QSFP-LR4 and QSFP-LR4L transceivers are also available, such as Cisco QSFP-40G-LR4 and WSP-Q40GLR4L. For more information about SMF&MMF QSFP+ transceivers, you can visit fiber-mart.com.

Cost Comparison: Fusion Splicing Versus Pre-terminated System

by http://www.fiber-mart.com

Fiber optic joints or termination is a necessary process when installing a network. Every network operators who aim to deploy a next-generation fiber network have to determine how to build a flexible, reliable and long-lasting infrastructure at the lowest possible cost. In general, there are mainly two fiber optic termination methods: splices which create a permanent joint between the two fibers, or connectors that mate two fibers to create a temporary joint. When people decide to use either method, many factors should be taken into account. Today’s article will evaluate both methods from the aspect of cost to help you choose the effective termination method.

Weighting the Two Methods

Besides the features of low loss, minimal reflectance and high mechanical strength, fiber optic termination must be compatible to the environment in which they are installed. Before we come to the cost comparison of these two termination methods, let’s firstly have a brief overview.

Fusion splicing

As it known to all that, splices create a permanent joint between two fibers, so its use is limited to place where cables are not expected to be available for servicing in the future. The most common application for splicing is joining cables in long outside plant cable runs where the length of the run requires more than one cable. There are two types of splices, fusion and mechanical. Fusion splicing is most widely used as it provides for the lowest loss and least reflectance, as well as providing the strongest and most reliable joint.

Fusion splicing machines are usually called fusion splicer available on the market that splice a single fiber or a ribbon of 12 fibers at one time. The above picture shows how to splice a fiber optic jumper. Virtually all single-mode splices are fusion. Fusion splices are made by “welding” the two fibers together usually by an electric arc. To be safe, you should not do that in an enclosed space like a manhole or an explosive atmosphere, and the equipment is too bulky for most aerial applications, so fusion splicing is usually done above ground in a truck or trailer set up for the purpose.

Today’s single-mode fusion splicers are automated and you have a hard time making a bad splice as long as you cleave the fiber properly. Fusion splicers cost thousands US dollars (up to $5,000), but the splices only cost a few dollars each. The following part display the main features of the fusion splicing:

Typical average optical losses of 0.05dB or lower

Not de-mateable

Special installation skills needed

Tools sensitive to the environment

Relatively long installation time

Standard organizer techniques required

Pre-terminated System

Pre-termination is the alternative termination method popular on the market. Cables and fibers are terminated to a connector in the factory. When carefully planned, splicing jobs for specialized technicians can be limited to the network construction phase. But provisioning, churn and network testing can be performed by technicians without specific fiber skills, because the organizers can be very simple.

With pre-connectorized products, the connection time is reduced from 20 to less than 5 minutes, including the connector cleaning step. When connecting fibers with connector technology, there is no issue of environmental sensitivity. What’s more, connectors are accessible on the outside of the network element, reducing the need to access a product and the risk of disturbing other lines. The image below shows the MPO pre-terminated cables.

Factory pre-termination is also compatible with optical budget requirements by selecting the appropriate grade as defined by the international IEC standards. When properly planned, pre-connectorized

products do not add extra connectivity points, thus eliminating extra optical loss or reflections. In all, the most obvious features of the pre-terminated system lies in the following part:

Typical losses of 0.15dB or less

Fully de-mateable

No special installation skills required

Reduced installation time

Very simple organizer systems

Insensitive to environmental conditions

Cost Comparison

The start-up costs for the fusion splice are significantly higher, as fusion splicers can be very expensive. Even the cheapest fusion splicer will cost nearly $2,900 (fiber-mart-F600 Fusion Splicer from fiber-mart.COM) more than the most expensive crimp kit. Not counting the initial start-up costs, splices will run anywhere from $7.20 to $8.25 per splice, which is much lower than the pre-terminated connector. The following image shows the vivid comparison between fusion splicing and pre-terminated system.

Cable Plant Used in a Fiber Optic Data Link

by http://www.fiber-mart.com

A fiber optic data link carries signals for communications, security, control and similar purposes by using transceivers and optical fibers. Designed to protect the fibers, an optical fiber cable should be installed, spliced and terminated with the proper hardware to mate the data link transceivers, and included in a fiber optic cable plant. This cable plant must be selected and installed to withstand the environment, and typically terminated at outlets or patch panels near the communications equipment. It’s connected to the transceiver by short fiber optic jumper. Last blog introduces fiber optic data links: parts, signals and power budget. Today’s blog details another device used in data links: fiber optic cable plant.

Cable Plant Basicst Basics

Since the fiber optic cable plant consists of the optical cable which is terminated with the transceiver, this cable plant must be compatible with the performance parameters of the transceivers for the link to operate properly. This includes types of fiber capped with different connectors (e.g. LC to SC fiber patch cable), optical loss and bandwidth of the cable plant. For the cable plant, a loss budget must be calculated to estimate its loss and a power budget to determine if the planned communications system will operate over the cable plant.

Cable Plant Performance Factors Factors

For a fiber optic data link performances, the parameters are those that define the communications signals to be carried on the link or bandwidth at which the link operates, the length of the link and the specifications (bandwidth and optical loss) of the fiber optic cable plant. These factors determine the types of transceivers and cable plant components that must be chosen for a communications system. (Among these factors, the loss of the cable plant and the bandwidth have effects on the link design and testing after installation.)

Cable Plant Lossant Loss

The loss of the cable plant is determined by the summation of the loss in the cable plant because of fiber attenuation, splice loss and connector loss. In some cases, the fiber attenuation may be increased due to improper installation of the cable. As a signal travels down the fiber, the signal will be attenuated by the optical fiber and reduced by the loss in connectors and splices.

Loss Budgets Budgets

For each cable plant designed, the loss budget must be calculated. Then according to the loss budget, the loss of the fiber in the cable plant can be estimated by multiplying the length (km) by the attenuation coefficient (dB/km), then adding the loss from connectors and/or splices determined by the number of connectors and/or splices times the estimated loss each to get the total estimated loss of the cable plant. The cable plant loss budget must be lower than the power budget of the link transceivers (see below) for the link to work properly.


Dispersion or pulse spreading limits the bandwidth of the link. Transceivers have some dispersion caused by the limitations of the electronics and electro-optical components, but most of the dispersion results from the limited bandwidth of the fiber in the cable plant.

Dispersion in multi-mode fiber (MMF) occurs by modal dispersion or chromatic dispersion. Modal dispersion is caused by the different velocities of the various modes being transmitted in the fiber. Chromatic dispersion is caused by the different velocities of light at different wavelengths.

Single-mode fiber (SMF) also causes dispersion, but generally only in very long links. Chromatic dispersion has the same cause as MMF, the differences in the speed of light at different wavelengths. SMF may also suffer from polarization-mode dispersion causes by the different speeds of polarized light in the fibers.

The transceiver must be chosen to offer proper performance to the communications system’s requirements for bandwidth or bitrate, and to supply an optical transmitter output of sufficient power and receiver of adequate sensitivity to operate over the optical loss caused by the cable plant of the communications system. The difference in the transmitter output and receiver sensitivity defines the optical power budget of the link.

The cable plant components, optical fiber, splices and connectors, are chosen to allow sufficient distance and bandwidth performance with the transceivers to meet the communications system’s optical power budget requirements. The power budget of the link defines the maximum loss budget for the cable plant. The maximum link length will be determined by the power budget and loss budget for low bit rate links that will be derated for dispersion for higher bandwidth links.

Most communications systems with short links have options for both MMF and SMF, while longer links use only SMF. All networks may provide guidance as to the types or grades of fiber needed to support certain applications.

Every manufacturer of data links components and systems specifies their link for receiver sensitivity (perhaps a minimum power required) and minimum power coupled into the fiber from the source. In order for a manufacturer or system designer to test them properly, it is necessary to know the test conditions. For data link components, that includes input data frequency or bitrate and duty cycle, power supply voltages and the type of fiber coupled to the source. For systems, it will be the diagnostic software needed by the system.


Fiber optic cable plant is an integral part of a fiber optic data link, and it should be managed in the exact path that every fiber in each cable follows, including intermediate connections and every connector type.

What Kinds of Optical Fibers Do You Know?

by http://www.fiber-mart.com

Optical fibers can be divided according to the material they are made of. As mentioned in previous post, optical fibers can be made of glass, but they can also be made of plastic. Both of the materials have their pros and cons.

The fibers made of glass are great for long-distance transmission, but are very expensive. They are divided into two different types: Single mode and Multimode. The main difference between both of them is the core diameter and the number of light bundles in the fiber. Single mode fibers allow only one beam of light to be transmitted, and Multimode fibers can transmit multiple light beams at a time.

As we already said, we also know optical fibers made of plastic, also called POF fibers (Polymer optic fiber). Plastic fibers are used at shorter distances and have a larger core diameter. Their transmission routes are less reliable than the ones of glass fibers, but their main gain is the low cost. Plastic fibers are, compared to the glass ones, really inexpensive.  So if we combine both, pros and cons, we can conclude that plastic fiber are mainly used on short distances (inside our homes etc.) to lower the cost. Most of the time, POFs at home are found in connecting audio devices. The attenuation for fiberglass is 0.2dB / Km, for POF this is 100dB / Km.

A huge part of human population has an access to the worldwide internet and if we are lucky enough to live in a bigger city, there is a good chance that our internet providers are not only able to offer us an internet connection through copper fibers, but through optical fiber as well.

According to the topology used by the ISP-Internet Service Provider, there is an optical fiber that leads to our houses. Mainly the fibers that lead to our homes are known as Single mode optical fibers (search above for an explanation) which are best suited for long distance transmissions. The connection is tailored to the economic and physical capacities, and most providers provide at least two optical fibers for security and faster debugging if some kind of error occurs. However, where economic or physical capacities do not allow the use of two fibers, the providers provide only one optical fiber through which the two-way communication is used.

Depending on the number of fibers, we have an adapted method of communication between the modem and the control panel. The simplest solution is if there are two optical fibers available. In this case one of the fibers represents the TX receiving fiber and the other optical fiber represents the transmitting fiber – RX.  Depending on the number of optical fibers that are available, the entire system, which includes the technology in the switchboard and the modem or the receiving side, must also be adapted.

In case we do not have enough (at least two) optical fibers, we use Bi-direction connection, which means that we use one optical fiber for the two-way communication and connection. The way this works is that the system uses two wavelengths. One wavelength is used for TX (Transmit) and the other one is used for RX (Receive).

Unlike Single mode optical fibers, Multi mode optical fibers are mainly represented in very old communication routes. They are most commonly encountered in older LAN extensions with Media Converters. The problem with these fibers is that they are harder to bond and have several different core diameters. Technology is older the support is poor.

We know two different ways to connect (splice) optical fibers. One way of connecting or splicing two fibers, is with the help of connector. If we chose to use this way of connecting the fibers, we have to be extra careful and pay attention to the kind of the connector we use. There are quite a few different types of connector, but the ones that are most commonly used are SC, LC, FC, E-2000 connectors. If choosing this way of connecting the fibers we also have to consider the surface areas of the fibers we are splicing. This means that wa have to pay special attention to the grinding angle.

Another way of splicing the optical fibers is the permanent welding of optical fibers. This way of splicing requires special equipment suitable for welding a particular type of optical fiber. The work itself is precise and demanding, and also includes the complex preparation of the optical fiber before splicing. Proper and quality preparation of the fiber and the joint is of paramount importance, since it later affects the quality of the transmission route itself. This way of splicing optical fibers is better than connecting the fibers with connectors, because the joints and routes are more reliable and the attenuation is lower.

Why are SFP Transceivers so extensively utilized in Communication?

by http://www.fiber-mart.com

The electrical circuitry of the SFP transceiver modules is connected to copper or optical network. This type of transceivers is widely used for both data communications and telecommunication applications. Any official standards organization does not regularize the fiber optic SFP. The construction and specifications of this form-factor are specified by an MSA (multisource agreement) between competing manufacturers. SFP transceivers are readily available in a diverse range of options.

Advantages of SFP Transceivers

SFP Transceiver Module can be considered as the improved version of GBIC, and it is also called mini-GBIC. However, it allows better port density as its physical attributes are much compact than the GBIC. These transceivers are designed to offer data rates of up to 5 gigabits per second and even higher. With SFP transceiver, the up-gradation and maintenance of fiber optic network become more convenient than it has been with soldered-in modules. A single module SFP module can be replaced or repaired easily as it is hot-pluggable, and you won’t need to replace the entire board with multiple modules on it. This benefit can bring significant savings in terms of both; up-gradation and maintenance. The SFP form-factor is designed to support Fiber Channel, Gigabit Ethernet, SONET, and various other communication standards. Today`s SFP transceivers come with DDM and DOM functions. These functions offer real-time monitoring of various important networking parameters such as optical input and output power, laser-bias current, temperature, and transceiver supply voltage.

Availability in Various Types and Capacities

The availability of fiber-optic SFP in a broad range of types allows users to choose the best suitable transceiver according to their existing network requirements. Different types of SFP transceivers are available to operate over different wavelengths. Moreover, you can also choose an SFP transceiver based on the required link distance, please check the following summary:

Transmission rates: 100 Mbps to 4 Gbps

Possible Wavelengths: 850 nm, 1310nm, 1550ns, CWDM

Working Distance: 500 meters to 100 kilometers

What is Bending Radii or Bend Radius?

Following types of SFP modules are available at CBO – one of the finest networking equipment vendors:

It is essential to understand that the Copper SFP transceivers offer communication between optical fiber compatible host devices over twisted pair networking cables.

SFP Duplex

SFP Bidi

SFP Copper





SFP Applications

Fiber optic SFP transceivers provide interference between network devices such as media converters, routers, switches, and a copper or fiber optic networking cable. These transceivers are designed to support a broad range of networking and communications standards. SFP transceivers allow the transmission of gigabit ethernet and fast ethernet LAN packets over WANs. Besides this, the transmission of E1/T1 streams is also possible over packet-switched networks with SFP transceivers.

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