Basic parameters of optical fiber devices

Basic parameters of optical fiber devices

Optical fiber devices have two basic parameters, namely insertion loss and isolation. Optical fiber transmission system requires small insertion loss and large isolation.

Insertion loss The optical power loss caused by the insertion of optical fiber devices into the optical fiber transmission system. It is usually expressed by the logarithm of the ratio of the output power and input power Pi of the device, that is, for a device with multiple output terminals, it should be the sum of the power of each output terminal. The main causes of insertion loss are light leakage, radiation, scattering and aberration. Insertion loss is usually measured by truncation method, temporary contact method (or two-point method) under the condition of steady mode distribution.

Isolation: After some optical fiber components are inserted into the optical fiber transmission system, light will leak from one optical path to another, which is often called crosstalk. It is usually expressed by the logarithm of the ratio of the power P1 leaked to another optical path to the input power Pi of the main optical path: the main causes of crosstalk are Fresnel reflection of the fiber end face in the device, improper cladding thickness between optical paths, and poor absorption performance of leakage and radiation modes.