Single mode fiber optic evanescent wave refractometer

摘要

The invention relates broadly to a fiber optic sensor device, advantageously, a refractive index measurement device. A light emitting member transmits light, preferably coherent light, to a light splitter. The light splitter splits the light into a first portion that is transmitted to a first fiber optic coupler having an input optical fiber member and an optical fiber member having a waist region. A first output optical fiber member emerges from the first fiber optic coupler waist region. The light splitter is positioned to insert light into the first fiber optic coupler input optical fiber member. A reference fiber optic coupler includes an input optical fiber member and an optical fiber member having a waist region. The reference fiber optic coupler is enclosed in a potting medium stable reference of constant refractive index. A reference output optical fiber member emerges from the reference fiber optic coupler waist region. The light splitter member inserts a second portion of the split light into the reference fiber optic coupler input optical fiber member. A sum difference device processes the measured light emitted from the first output optical fiber member and from the reference output optical fiber member whereby the value derived said measured light emitted from said first output optical fiber member is independent of variations in light from said light emitting member.