Optical-fiber Fabry-Perot embedded sensor.

A reflectively monitored optical-fiber Fabry-Perot interferometer was embedded in a graphite-epoxy composite material. Its performance as a temperature sensor was demonstrated from 20 to 200 degrees C. The change in relative phase shift with temperature, Deltaø/øDeltaT, was measured to be 8.0 x 10(-6)/ degrees C for this embedded sensor. This value is 4% lower than for one employing a similar fiber in an air ambient. A thermal expansion coefficient for the composite material in the direction of the fiber axis is estimated from these data to be 2.1 x 10(-7)/ degrees C.