An intensity-modulated optical fiber sensor with concave mirror for measurement of displacement

Abstract

Two fiber intensity-modulated sensors are investigated and used in number of applications, including those in military, industry, biomedical, and aerospace. A common form of two fiber intensity-modulated optical fiber sensor performs its measurement by making use of a pair of straight optical fibers with a plane reflector. The reflected optical intensity is a function of distance between fiber tips and plane reflector as well as refractive index of the medium. This paper describes an alternative sensing structure with a concave reflector instead of a plane reflector and demonstrates the derivation of the geometric mathematical model for analyzing its sensing characteristics. The mathematical model shows that the blind region is minimized, when the plane reflector is replaced by a concave reflector. Such type of optical sensor can be used where space required for the measurement is the major limitation. Experimental results obtained confirm the model.