Time- and Wavelength-Multiplexed Wavelength Shift Detection for High-Resolution, Low-Cost Distributed Fiber-Optic Sensing

We present a concept for time- and wavelength-multiplexed readout of wavelength-encoded fiber optic sensors, useful for low-cost distributed sensing and high-resolution monitoring in critical applications such as battery management and energy systems. By taking advantage of the unused photodetector bandwidth in a wavelength-multiplexed fiber Bragg grating (FBG) sensing system based on an arrayed waveguide grating (AWG), we can time-multiplex the detection of 100s of FBG sensors. Our initial implementation is capable of monitoring over 100 sensors at a simultaneous readout rate of 100 Hz with sensor crosstalk below 100 fm and wavelength noise of 11.5 fm Hz –1/2 from 10 to 50 Hz; the light source used to illuminate the FBGs is the dominant contributor to this noise. We present a simplified theoretical framework for understanding system tradeoffs in terms of AWG channel spacing and a sensor slope factor.