Optical transceivers: SFP, QSFP or CFP?

Article By : Marcin Bala

To help network managers make an informed decision, Marcin Bala of Salumanus discusses three different types of transceivers and their main applications.

Optical transceivers are nowadays widely used in networking hardware installations in virtually all sectors. According to the Transparency Market Research, the optical transceiver market is expected to dominate the transceiver market with a revenue of $36.8 billion by the end of 2027. Their growth is mostly visible in electronics, particularly electronic warfare systems and in IT.

Due to their popularity, they are believed to be one the simplest pieces of hardware in a network, but that is not the case. There are a great number of transceivers and possible configurations, and their quality and reliability can change from brand to brand.

Choosing the wrong transceiver or ignoring any quality verification means that at the end of the day, system administrators might have to deal with unexpected issues caused by poor quality transceivers. So, what are the three main categories of transceivers and how are they best used in different applications?

Telecommunications

SFP transceivers

The most popular format for transceiver is the Small-Form-Pluggable (SFP) transceiver. The SFP transceiver is a small, compact and hot-swappable device, which can be used in different applications, including in tight networking spaces to provide fast communication between switches. They are designed to support several communication standards, including SONET, Ethernet, Gigabit and Fiber Channel.

They are also highly flexible, as their interfaces on networking devices — such as routers — can be readily adjusted to fiber optic and copper networking specifications. SFP transceivers also support both single mode and multimode fiber and transmit data over a pair of optical fibers (duplex) or over a single optical fiber (simplex), and also in CWDM/DWDM technology.

SFP+ transceivers are an advanced version of SFP with higher data rates of up to 16Gbps. This version is mostly used for 10G Ethernet and other high-speed transmissions, but it works across shorter distances than SFP. However, not all SFP modules are compatible. For most vendors, it is possible to fit an SFP module into an SFP+ one but not vice-versa, meaning that users can’t insert SFP+ transceivers in an SFP slot.

Recently, two new advanced versions of SFP transceivers have been developed, the SFP28, which supports a speed of up to 28.1Gbps, and SFP56, which is capable of doubling the capacity of SFP28, if set up with a PAM4 modulation.

The versatility of these SFP transceivers allows them to be used in almost all applications that require high-speed and long-range cables, from high-definition audio transmission and reception, passive optical networks (PON), to multiplexing and simplex networking. In copper networks, they are ideal for bridging communication between switches on a distance of up to 100m. In fiber optics, they can be used in Ethernet switches, routers, and firewalls with a network range anywhere from around 500m to over 100km.

QSFP transceivers

QSFP stands for Quad (four channel) Small Form-Factor Pluggable transceiver, and it was developed as a response to the growing demand for gigabit Ethernet. Network managers are now migrating to 40G and QSFP transceivers are an essential component that ensures high speed internet.

The 40G QSFP optical module is a compact hot-swappable light module that provides four transmission channels in one pluggable interface, each with a data rate of 10Gbps. Compared to SFP+ optic modules, the QSFP modules can increase the port-density by four times.

QSFP+ is a parallel and hot-swappable fiber optical module that provides high-density 40G connectivity options for high-performance computing networks and modern data centers. QSFP+ switches can connect an entire electrical circuitry of a system to an optical external network.

Further demand for higher data rates has led to the development of QSFP28, which supports 28Gbps data rates on each of its four channels. This transceiver supports both single mode and multimode applications for distances of up to 100km. It also uses four wavelengths, some of which can be enhanced using CWDM technology, with each channel carrying up to 28Gbps.

An advanced version of QSFP is QSFP-DD (dual density), which has 8 channels and allows for double speed on a single channel and is able to carry 400G over just one transceiver.

CFP transceivers

The CFP module is a hot pluggable form factor transceiver that serves 100G interfaces. Different types of this module, such as CFP2, CFP4 or CFP8 can support ultra-high bandwidth requirements of data communication networks, including next-generation High-Speed Ethernet. The most recent module, the CFP8, provides support for a broad range of PMD’s at 400G and is future-proof for supporting 800Gb/s.

These transceivers are primarily used in WAN, Metro, wireless basestations, video and other telecommunication networks systems. They have widely been implemented in enterprise data centers, High Performance Computing and Internet provider systems due to their long-distance transmission and fast speeds.

Whether network owners are looking for higher bandwidth at the expense of distance transmission or they need strong connectivity over tens of kilometers, they can choose from a wide selection of modules. At Salumanus, we have delivered over 500,000 optical modules in the last few years.

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