Measuring physical value by fibre=optic sensor - using two sensor leads alternatively used as send and receive fibres and useful and reference light beams

摘要

An optical fibre sensor (10) is used for working with useful (13) and reference (12) light beams. Light is bidirectional applied to two fibre-optic sensor leads (6.1, 6.2) operated as send and receive fibres. Each light beam is led to a different path according to its direction of dispersion through a light junction. The latter pref. consists of two optical elements allowing the light to propagate in one direction but interrupting it in the other direction to function as light valves. The latter are arranged in opposed directions for sensor and reference branches. The light valves can be realised as an optical isolators using the Faraday effect. ADVANTAGE - Does not depend upon reflection of a definite part of the light in the send fibre. Thus no parasitic reflections can occur to affect the measuring process.