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 ill uminates four gratings spaced five meters apart Each grating in the ar ray 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 conv erted to phase changes by routing the reflected signal through a nearl y path balanced fiber Mach Zehnder interferometer, The minimum detecta ble strain was measured to be as low as 2 nanostrain/root Hz for frequ encies greater than 10 Hz.