An optical fuse is a passive component that can be placed at the input port of an optical device such as a detector, or at the output port of a high-power device such as a laser or optical amplifier, to protect the system from power spikes and surges. The typical operating power of a protected system is roughly 3 dB below the threshold power, and the insertion loss of the fuse itself is between 0.5 and 1 dB. It is available in a patch cord style package for installation between pieces of equipment or as a bare fiber assembly for simple fusion splice integration.

A new invention recently introduced by Molex (NASDAQ: MOLX), the device will not only protect expensive components, it promises to reduce system downtime, as a fuse is easier to replace than a damaged component.

When the power is lower than a designated threshold level, the fuse remains transparent; and when the power exceeds the threshold level, the fuse turns permanently opaque. An activated fuse blocks the forward power without increasing the reflected power, protecting both ends of the system.