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Title: Microbend fiber-optic temperature sensor

A temperature sensor is made of optical fiber into which quasi-sinusoidal microbends have been permanently introduced. In particular, the present invention includes a graded-index optical fiber directing steady light through a section of the optical fiber containing a plurality of permanent microbends. The microbend section of the optical fiber is contained in a thermally expansive sheath, attached to a thermally expansive structure, or attached to a bimetallic element undergoing temperature changes and being monitored. The microbend section is secured to the thermally expansive sheath which allows the amplitude of the microbends to decrease with temperature. The resultant increase in the optical fiber's transmission thus allows temperature to be measured. The plural microbend section of the optical fiber is secured to the thermally expansive structure only at its ends and the microbends themselves are completely unconstrained laterally by any bonding agent to obtain maximum longitudinal temperature sensitivity. Although the permanent microbends reduce the transmission capabilities of fiber optics, the present invention utilizes this phenomenon as a transduction mechanism which is optimized to measure temperature.
  1. (Albuquerque, NM)
Issue Date:
OSTI Identifier:
Sandia Corporation () SNL
Patent Number(s):
US 5419636
Contract Number:
Research Org:
Country of Publication:
United States
microbend; fiber-optic; temperature; sensor; optical; fiber; quasi-sinusoidal; microbends; permanently; introduced; particular; graded-index; directing; steady; light; section; containing; plurality; permanent; contained; thermally; expansive; sheath; attached; structure; bimetallic; element; undergoing; changes; monitored; secured; allows; amplitude; decrease; resultant; increase; transmission; measured; plural; completely; unconstrained; laterally; bonding; agent; obtain; maximum; longitudinal; sensitivity; reduce; capabilities; optics; utilizes; phenomenon; transduction; mechanism; optimized; measure; temperature change; bonding agent; temperature changes; fiber optics; fiber optic; optical fiber; temperature sensor; permanent microbends; microbend section; quasi-sinusoidal microbends; permanently introduced; index optical; metallic element; measure temperature; /374/250/385/