Coherence multiplexing of fiber-optic pressure and temperature sensors based on highly birefringent fibers

In this paper, we present several coherence-based configurations of sensor systems that have been designed and studied specifically for multiplexing of white-light interferometric pressure and temperature transducers based on highly birefringent optical fibers. The first discussed is a serial system that may be composed of up to four pressure (range 0-20 MPa) and temperature (range -50°C-+50°C) sensors powered by a single broadband laser source. An electronically scanned interferometer based on a Wollaston prism with a step-delay line and a CCD array was used as a decoding unit. To increase the number of multiplexed sensors we also proposed a mixed serial-parallel configuration in which two serially connected sensors for measuring pressure and temperature are further arranged in parallel branches powered by several independent sources. The absolute system accuracy is about 0.5% of full scale. In addition to the full characterization of all multiplexed pressure sensors against a primary pressure standard, system response to fast temperature changes, to connecting additional cables, to input-output replacing, and to exchanging sources is also presented