Optoelectronics

How to choose the best optical transceivers

26th April 2022
Beatrice O'Flaherty

For optical transceivers, many users no longer solely consider the stability and reliability of the transceiver itself, but also evaluate additional factors such as price, quality and specifications. With so many options on the market, how do you ensure you choose the best optical transceiver for your application? Here Marcin Bala, CEO of telecommunications solutions provider Salumanus, discusses what to consider when choosing optical transceivers.

Advancements in technology have led to an even greater need for reliable and stable data transmission, resulting in transceivers becoming an essential part of any network's hardware configuration. Optical transceivers are often regarded as one of the simplest pieces of hardware in a network, but this is not true. Selecting the wrong transceiver or one of poor quality could lead to a number of unforeseen issues.

There are many important factors to consider when choosing an optical transceiver for your application, such as data rates, wavelengths and transmission distance. To help narrow down this search, here are three categories of transceivers — SFP, QSFP and CFP — and their core benefits.

Compact and flexible

Small form-factor pluggable (SFP) transceivers are the most popular optical transceiver type, mainly due to their compact size. The small size allows these transceivers to be compatible with various applications, which is especially useful for tight networking spaces  that still require fast transmissions. The SFP module is also hot-pluggable, meaning it can be easily adjusted to existing networks without the need for cable infrastructure redesign. SFP transceivers are very flexible and are compatible with both copper and fibre networks.

In copper networks, these transceivers are perfect for connecting transmissions between switches that are up to 100 metres apart. However, when used in fibre optics, they can have a communication range of around 500 metres to over 100 kilometres. These transceivers are mainly used in Ethernet switches, routers and firewalls.

There is also a more advanced version of the SFP, called the SFP+, that is faster than its original counterpart and can support speeds up to 10 Gbps. SFP+ are not the only advanced versions of the SFP transceiver — there are also the SFP28 and the SFP56. The SFP28 differs as it can support up to 28.1Gbps, whereas the SFP56 has double the capacity of SFP28 when combined with PAM4 modulation.

The SFP transceivers support both single-mode and multi-mode fibre and can transmit data over a duplex or a simplex fibre strand. The flexibility of SFP transceivers makes them compatible with almost all applications that require high-speed over long ranges, such as dark fibre, passive optical networks and multiplexing.

High density and compact 

Quad small form-factor pluggable (QSFP) transceivers are used for 40 Gigabit Ethernet (40GbE) data transmission applications. Like SFP transceivers, QSFP ones are also hot-pluggable. However, in comparison to SFP+ optic modules, QSFP ones have four transmission channels, each with a data rate of 10Gbps, allowing for the port-density to be four times higher than that of SFP+ transceivers.

The QSFP transceiver, like the SFP, can support bother single-mode and multi-mode applications but is capable of doing this over a 100 kilometre distance. QSFP transceivers are ideal for networks that require higher data rates. QSFP28 transceivers can support both high speed and high-density data transmissions, thanks to their ability to provide even higher data rates of 28Gbps on all four channels. QSFP transceivers use four wavelengths that can be enhanced using coarse wavelength division multiplexing (such as CWDM and LanWDM) technology.

A popular configuration of the transceiver is the 100G QSFP28 DWDM PAM4 solution. This configuration is capable of connecting multiple data centres within over a distance of 80 kilometre. The advantage of using this configuration is that it enables an embedded dense wavelength division multiplexing (DWDM) network to be built using the transceiver directly in the switch.

Like the SFP transceiver, this one also has a more advanced version, the QSFP dual density (QSFP-DD). This essentially provides double the channels and double the speed, meaning the transceiver has eight channels capable of 400G (8x50G).

Ultra-high bandwidths and high speeds

The C form-factor pluggable (CFP) transceiver is a common form factor used for high-speed digital signal transmissions. There are four different types of CFP transceivers, CFP, CFP2, CFP4 and CFP8, all of which can support ultra-high-bandwidth requirements, including next-generation high-speed Ethernet. The most recent module, CFP8, can support a broad range of polarisation mode dispersions at 400G and is already made to support 800Gbs. On the other hand most frequently chosen one is still CFP2.

The 100G CFP coherent module supports a range of applications such as 80 kilometre interfaces or 2,500 kilometres DWDM links. This module is also configurable to optimise power dissipation for a given application.

CFP transceivers are mainly used in wide area networks (WANs), wireless base stations, video and other telecommunication network systems. They are widely used in data centres, high-performance computing and internet provider systems as they have a long transmission distance and fast speeds.

The high variety of transceivers on the market can make it difficult to find the most suitable one for our application, but whether network owners require high bandwidths or strong connections over long distances, there is a transceiver to deliver that. At Salumanus, we have delivered over 500,000 optical modules in the last few years, offering expert support in choosing the most suitable transceiver for clients’ networks.

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