Characterization of a multipoint sensor based on fiber Bragg gratings

Abstract

The industrial processes need to control many variables such as temperature, flow, pressure, position, etc. For this reason, one sensor is required for each signal to be controlled. Therefore, multipoint sensors that can measure different signals in the same system have been proposed. In this work a multipoint sensor, which consists of a fiber laser with two Fabry-Perot cavities based on fiber Bragg gratings was studied. The sensor operation principle is based on the overlapping of the gratings reflection spectra, which produce a laser emission with a wavelength of 1536 nm. For this kind of sensors, various detection methods to identify and quantify the signals from its intermodal frequencies, have been used which employ some circuits like PLL (Phase Loop Lock), lock-in amplifiers and electrical spectrum analyzers. However these equipments are quite expensive. Therefore in the present work signal analysis with Fourier discrete transform to identify and quantify the sensor signals based on the laser intermodal frequencies is proposed. Such frequencies were 200 and 800 kHz corresponding to cavities of 500 and 130 m length, respectively.