Fiber Bragg grating interrogation and multiplexing with a 3 x 3 coupler and a scanning filter

We present a new technique for fiber Bragg grating (FBC) sensor interrogati on and multiplexing, The technique combines a scanning bandpass filter used to multiplex by wavelength multiple gratings in a single fiber, and an unb alanced Mach-Zehnder fiber interferometer made with a 3 x 3 coupler to dete ct strain-induced wavelength shifts. A demonstration system interrogates fo ur gratings in a single fiber at a sampling rate up to 20 kHz, with a noise floor measured at less than 10 n epsilon/root Hz above 0.1 Hz.