Component · Photonics, MEMS & Sensors
Optical transceiver
A module combining transmit and receive optics with driver, amplifier and DSP electronics to convert between an electrical host interface and optical fibre. It is sold in standardised pluggable form factors defined by multi-source agreements.
- Also known as
- Optical module, Pluggable optic
- Type
- Component
- Domain
- Photonics, MEMS & Sensors, Optical components
Notes
Pluggable modules now consume a significant share of switch power, which is the core commercial argument for co-packaged optics.
Overview
An optical transceiver is a module that converts electrical signals from a switch, server or accelerator into light for transmission over optical fibre, and converts received light back into electrical signals. Most are hot-pluggable modules in standard shapes defined by industry multi-source agreements, such as QSFP-DD and OSFP, so equipment makers can buy them from several suppliers. They are the workhorse of data centre and telecom networks, and AI clusters now use them in very large numbers.
How it works
On the transmit side, a driver amplifies the electrical data stream to modulate a laser, either directly or through a separate optical modulator. On the receive side, a photodetector turns light back into a small current, and a transimpedance amplifier (TIA) converts that into a usable voltage. Many high-speed modules also contain a retimer or DSP that cleans up the signal and recovers its timing, and some include a gearbox to convert between electrical and optical lane rates, or forward error correction for long reaches. The host manages the module and reads its status through a management interface, commonly OIF's CMIS.
The electrical side presents several lanes to the host. An OSFP module, for example, has eight high-speed electrical lanes, giving 400 Gb/s with 50G lanes, 800 Gb/s with 100G lanes or 1.6 Tb/s with 200G lanes. The optical side depends on reach: multimode fibre for short links inside a rack or row, single-mode fibre for kilometres, and coherent optics, as in OIF's 400ZR and 800ZR agreements, for longer data centre interconnects.
Mechanical size, power dissipation and cooling are limiting factors. The OSFP format includes an integrated heat sink. Power at the highest speeds is one reason vendors are building co-packaged optics switches; NVIDIA, for example, claims 3.5 times better power efficiency for its photonics switches, while expecting pluggable modules to remain in use alongside them.
Examples
- An 800 Gb/s OSFP module with eight 100G electrical lanes connecting a GPU server to a leaf switch.
- A 400ZR coherent module carrying traffic between data centres tens of kilometres apart.
- A switch managing hundreds of pluggable modules through the Common Management Interface Specification (CMIS).
Why it matters
Every link in a large cluster needs a pair of modules, so cost, power and supply of transceivers affect how big AI and cloud networks can grow. Optical module engineers, TIA and driver designers, SerDes teams and test engineers all work on them, and chip companies supply the lasers, DSPs, drivers and TIAs inside.
Related terms
Part of the Photonics, MEMS & Sensors glossary, with every term in the topic and the lifecycles, tools and standards that use them.
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Last reviewed . Written by The Semiconductor Hub editorial team. The full glossary