FMCW multiplexing of fiber Bragg grating sensors

We report on the use of frequency-modulated continuous wave (FMCW) techniques for multiplexing fiber Bragg grating (FBG) sensors. This technique is based on the modulation of light intensity from a broadband source by a linear swept-frequency RF carrier. Signals from the FBG sensors located at different positions in an array are separated in frequency domain and demodulated using a tunable optical filter. The potential and limitation of the technique are discussed. A three-sensor FMCW multiplexed FBG array of parallel topology and a six-sensor hybrid FMCW/WDM system were experimentally demonstrated with -30 dB crosstalk between sensors and 2 /spl mu//spl epsi/ resolution in terms of root mean square (RMS) strain value.