Optical Transceivers

A fiber optic transceiver is a module that transmits and receives data over a fiber optic cable rather than an electrical wire. The medium used for transfer of the signals from one end to the other end is a light beam often referred to as a laser beam. On the contrary, the electrical wire uses the electric current as a medium to transfer the signals. Fiber optic communication has completely changed the landscape of networking world. It has enabled high speed networks and efficient and reliable data transfer. All of the fiber optic networks make use of the optical transceivers that are hot-swappable modules plugged into the communication equipment. A variety of optical transceivers have been developed and are currently in use in various networks all over the world. This article will provide an insight into the different types of optical transceivers, the applications which can make use of the optical transceivers and also explain the use of CBO-IT’s optical transceivers with communication equipment of several original equipment manufacturers (OEMs). Let us start with getting deeper into understanding the basics of an optical transceiver.

What is an Optical Transceiver?

As previously mentioned, an optical transceiver is an interface module that is used to connect fiber optic cable to a communication equipment. An optical transceiver uses a hot-swappable design so that it can be plugged in and pulled out of the communication equipment without turning it off. Figure 1 shows a basic block diagram of an optical transceiver illustrating its functionality. An optical transceiver has a transmitter and a receiver built-in the module to enable duplex communication. Similarly, on the other end, a similar transceiver is installed which completes the communication cycle. An optical transceiver also houses a light source. For very precise optical transceivers, the light source is a laser beam. Laser beams provide very low scattering, hence are useful for the communication over single-mode fiber optic cables. On the other hand, LED light source is used for communication over multi-mode fiber optic cables as the multi-mode fiber optic cable can tolerate scattered light. The wavelengths used for optical fiber communication ranges between 850nm to 1550nm. In the next section, we will discuss the different form-factors available in optical transceivers.

What types of Optical Transceivers are available?

There are several types of optical transceivers are available in the market. The optical transceivers can be classified on the basis of many factors such as:

• Form-factor (Physical Dimensions)
• Bandwidth (100 Mbps, 1 Gbps, 10 Gbps, 40 Gbps, 100 Gbps etc.)
• Application (Fibre Channel, Ethernet, InfiniBand etc.)

Let us study the classification of optical transceivers based on the form-factor. Optical transceivers are available in form-factors, mainly:

• Gigabit Interface Converter, commonly referred to as GBIC
• Small Form-Factor Pluggable, commonly referred to as SFP
• Quad Small Form-Factor Pluggable, commonly referred to as QSFP
• C Form-Factor Pluggable, commonly referred to as CFP

Gigabit Interface Converter (GBIC)

GBIC transceiver was first introduced and standardized in 1990 by the Small Form-Factor Committee (SFF Committee). The primary reason to develop such a transceiver was to enable the use of fiber optic cables to connect two or more communication devices and allow more bandwidth and longer distance direct links. GBIC transceiver usually provides up to 1Gbps duplex bandwidth over a single link, although it has been tested for speeds up to 2.5Gbps.

GBIC transceiver commonly uses the SC connector to terminate the fiber optic cable. Transceivers are also available for 1000BASE-T to terminate the common twisted pair copper cables. One of the main features of GBIC is that it is hot-swappable, i.e., one does not need to power off the communication equipment to insert or remove the GBIC. This allows the communication network to be always-on despite new links being added on it.

Figure 1 depicts a typical GBIC transceiver. The dimensions of the GBIC transceiver as defined by the SFF Committee standard document are 57.15mm x 12.01mm x 30.48mm (L x H x W). GBIC slot in the communication equipment is also designed keeping in view the mentioned dimensions.

Small Form-Factor Pluggable (SFP)

SFP transceiver was the next step in the development of fiber optic transceivers, this was also developed as a standard by SFF Committee in 2001. SFP transceiver is much smaller in size as compared to its predecessor. The size of the SFP slot in a communication equipment is somewhat comparable to the normal electrical Ethernet port. Dimensions given in the SFF Committee standard document are given in Table 1.

It is necessary to mention here that several variants of SFP have been developed to support higher bandwidth using the similar form-factor. SFP+ is a transceiver that supports 10Gbps duplex link, similarly QSFP+ supports up to 40Gbps links with a little larger size than the SFP and SFP+.

Quad Small Form-Factor Pluggable (QSFP)

QSFP+ (Quad Small Form-factor Pluggable) transceivers are the most widely used 40 Gbps ethernet transceivers. Initially the QSFP standard was developed to support 4 x 1 Gbps channels over a single transceiver and later on the technology was introduced to allow 4 x 10 Gbps channels allowing for 40 Gbps link capacity. QSFP+ transceivers are compact and provide excellent support for extended distance links. Figure 1 illustrates a 40 Gbps QSFP+ transceiver. The QSFP+ transceivers can also support the fibre channel and Infiniband traffic. QSFP+ transceivers are being extensively deployed in datacenters to carry 40 Gbps ethernet traffic, 10G fibre channel or QDR Infiniband.

The leading original equipment manufacturers such as Cisco, HP and Juniper have a wide range of network equipment that supports 40 Gbps ethernet and QSFP+ transceivers.

C Form-Factor Pluggable (CFP)

To meet the ever-growing demand for higher speed communications, engineers started working on developing a transceiver that could support 100Gbps and higher bandwidths. In 2009, CFP MSA came out with a new standardized transceiver called CFP which could support 100Gbps traffic. Figure 3 represents a CFP module with dimensions of 144.8mm x 82mm x 13.6mm (LxWxH).

A CFP transceiver supports up to 10km link length on single-mode optical fiber cable and up to 150m on laser optimized multi-mode optical fiber cable.

Variants of CFP transceivers have also been developed as standards, CFP2 supports up to 200Gbps with a smaller form-factor and CFP4 supports up to 100Gbps with form-factor similar to SFP transceivers.

What applications can I use with an Optical Transceiver?

Optical transceivers are used for a large number of applications and are usually independent of the protocol. Optical transceivers are physical layer devices and their purpose is only to send and receive data in the form of light pulses. These light pulses are then converted to bits and presented to the communication equipment. The major applications of optical transceivers are:

• Ethernet
• Fibre Channel
• InfiniBand
• SDH/SONET

Ethernet is the most widely used networking technology. Almost every data network uses ethernet as its base technology. The other widely used technology is fibre channel, which is primarily used for storage networking. Fibre channel uses customized optical transceivers to support the fibre channel protocol and its speeds which are different than the ethernet standards. For example, ethernet optical transceivers are available in 1 Gbps, 10 Gbps, 40 Gbps and 100 Gbps bandwidths whereas the fibre channel optical transceivers are available in the speeds of 4 Gbps, 8 Gbps, 16 Gbps, 32 Gbps and so on. InfiniBand optical transceivers are also used in specific networks where InfiniBand protocol is being used. QSFP optical transceivers support InfiniBand. Other less commonly used transceivers are SDH/SONET optical transceivers which are used in active optical networks. These enable faster communication over fiber optic cables on a large-scale network that can be spread over a large physical and geographical area. SDH/SONET also enables multi-protocol transmissions.

Are BlueOptics Optical Transceivers compatible with other Vendors?

Optical transceivers are standards based equipment with the form-factor, pin configurations and other electrical and optical parameters exactly the same for every manufacturer. It is not necessary to use the optical transceiver of the equipment manufacturer with the equipment, rather, any standardized optical transceiver can be used. BlueOptics optical transceivers offer a wide range of choice and is completely based on the standards, hence, it can be used with almost every standard-compliant equipment manufacturer. The leading vendors supported by the BlueOptics optical transceivers are:

• Cisco
• Juniper
• HP
• DELL
• Huawei
• Brocade
• Lenovo
• Fortinet
• Barracuda

In addition to the above mentioned vendors, BlueOptics optical transceivers are supported by all other leading equipment manufacturers. To view the complete range of optical transceivers available, please visit www.gbic-shop.de