STRAIN-ISOLATED BRAGG GRATING TEMPERATURE SENSOR

摘要

A strain-isolated Bragg grating temperature sensor includes an optical sensing element (20, 600) which includes an optical fiber (10) having at least one Bragg grating (12) disposed therein which is encased within and fused to at least a portion of a glass capillary tube (20) and/or a large diameter waveguide grating (600) having a core and a wide cladding and having the grating (12) disposed therein, which senses temperature changes but is substantially not sensitive to strains on the element caused by the fiber or other effects. Light (14) is incident on the grating (12) and light (16) is reflected at a reflection wavelength μ1. The shape of the sensing element (20, 600) may be other geometries and/or more than one concentric tube may be used or more than one grating or pair of gratings may be used or more than one fiber or optical core may be used. At least a portion of the element (20, 600) may be doped between a pair of gratings (150, 152), disposed therein to form a temperature tuneable laser or the grating (12) or gratings (150, 152) may be constructed as a temperature tuneable DFB laser disposed in the element. Also, the element may have an inner or outer tapered regions (22, 27), respectively, to provide strain relief and/or added pull strength for the fiber (10). Further, the fiber (10) and the tube (20) may be made of different coefficients of thermal expansion for increased sensitivity.