Wavelength-Division Multiplexed Interrogation of FBGs Using a Distributed-Feedback Laser Array

Wavelength-division multiplexed interrogation of fiber Bragg gratings (FBGs) is reported. A directly modulated distributed-feedback laser array is used as a multi-wavelength, frequency scanning, pulsed-light source. A heterodyne detection technique is used to increase the signal-to-noise ratio of weak reflection signals. Reflections from three fiber Bragg gratings with different peak wavelengths are simultaneously observed as beat oscillations. Reflection spectra are clearly seen with a signal-to-noise ratio of approximately 20 dB from the three fiber Bragg gratings with a reflectivity of 1% and an interval of approximately 1.5 m.