High-speed fiber-optic temperature sensor

The temporal response of a fiber-optic Fabry-Perot-type interferometer, formed by cleaving the ends of a length of highly birefringent (Hi-Bi) fiber, to high-frequency heat pulses is investigated both theoretically and experimentally. The heat pulses are produced by amplitude modulating the output of an argon laser with a variable frequency Bragg cell. This beam is focused at one of the cleaved ends of the interferometer; the fastest temporal response occurs when the beam is focused onto the core of the fiber. A time response of ~2.5 micros is measured.