optical switch

An optical switch directs beams of light along different paths inside fiber optic networks or photonic circuits. Instead of moving electrons through copper conductors as a conventional switch does, it redirects photons traveling through glass fibers or waveguides. The core function remains identical: connect input A to output B, or break that connection entirely. What changes is the medium and the mechanisms that control the routing.

Optical switches fall into two main categories by construction. Mechanical switches use motorized mirrors or rotating prisms to physically redirect light beams; these are robust and offer very high contrast ratios but switch relatively slowly, typically in milliseconds. Electro-optic switches use the Pockels effect or similar phenomena in materials like lithium niobate to alter the refractive index under an electric field, steering light without moving parts. Electro-optic devices switch in microseconds or faster but demand precise voltage control and often exhibit higher insertion loss.

Where optical switches live in a network

In telecommunications infrastructure, optical switches handle wavelength routing and cross-connect operations at network nodes. A 1x2 switch splits one input fiber to two outputs; larger matrices like 16x16 or 32x32 switch multiple fibers simultaneously. Insertion loss, measured in decibels, degrades signal strength; modern designs target losses below 1 dB per switch. Crosstalk, the leakage of light from one channel into another, must stay below minus 40 dB or signal quality suffers at high data rates.

Wavelength-selective switches combine optical switching with filtering, routing different wavelengths on a single fiber to different physical outputs. This allows one fiber pair to carry dozens of independent signals that are then separated and routed by wavelength. Such switches are essential in dense wavelength division multiplexed (DWDM) systems where each wavelength carries 100 Gbps or higher.

The term optical switch distinguishes this device from an electrical crossbar that operates downstream after photodiodes convert light to electrical signals. For most long-haul and metro networks, switching at the optical layer reduces power consumption and latency compared to optoelectronic conversion at every node. As data center traffic has grown, demand for fast, low-loss optical switching has driven development of silicon photonic integrated switches that combine routing, filtering, and signal conditioning on a single chip.