Dual-Wavelength Differential Detection of FBGs Using a Frequency-Scanning Pulsed Laser

The dual-wavelength differential detection of fiber Bragg gratings is reported. A directly modulated distributed-feedback laser array is used as a frequency-scanning pulsed light source. Trains of four 100-ns pulses with a frequency drift of 6.5 GHz and the same intensity are generated. Interrogating two serially connected Bragg gratings using the pulse trains, we show the selectivity of the high-sensitivity measurement and the wide measurement range, and the possibility of expansion to time-division multiplexing systems with a simple setup.