A 4-ELEMENT FIBER GRATING SENSOR ARRAY WITH PHASE-SENSITIVE DETECTION

A four-element, time-division multiplexed, fiber grating sensor array operating between the wavelengths of 1280 and 1310 nm was constructed and tested, The array consists of a 1300-nm edge-emitting LED that illuminates four gratings spaced five meters apart Each grating in the array reflects a spectrally narrow-band (0.3-0.5 nm) wavelength region. Measurand-induced changes In the grating period change the wavelength of the light reflected by each grating, The wavelength shifts are converted to phase changes by routing the reflected signal through a nearly path balanced fiber Mach Zehnder interferometer, The minimum detectable strain was measured to be as low as 2 nanostrain/root Hz for frequencies greater than 10 Hz.