Abstract: The present invention relates to optical fiber measuring systems comprising a light source, a modulator for modulating the amplitude of the light signal emitted by the light source at a modulation frequency, an optical connecting fiber, a resonant cavity, a phase detector and a phase comparator. According to the invention, a sensor which is sensitive to an ambient parameter is incorporated into the cavity such that a variation in the parameter causes a variatioin in the phase of the signal at the modulation frequency. The invention can be applied to measuring systems for use in a severe environment.

Abstract: The invention relates to a fiber-optic detector and concerns more particularly a detector capable of producing microbends in an optical fiber in response to the variation of a physical quantity or of an environmental parameter. The sensor of the invention consists of an optical fiber provide with a sheath which is covered by a layer exhibiting periodic discontinuities. The sheath and its covering react to the variation of the parameter to be detected in such a manner as to produce microbends of the same periodicity as that of the discontinuities.