High-Resolution Real-time FBG Interrogation System using a Gain-Switched Dual Optical Frequency Comb

We demonstrate a compact, low-cost fibre Bragg grating interrogation system combining an externally injected gain-switched dual optical frequency comb with embedded real time processing that achieves 0.6 pm resolution at 1011 Hz interrogation rates and <75 fm resolution at measurement rates below 3Hz. The system employs optical heterodyning and receiver integrated curve fitting algorithms to enable real-time operation. Comprehensive characterization of dual-comb stability, receiver processing performance, and algorithm accuracy validates the system's capabilities and identifies wavelength-dependent resolution behaviour linked to variations in comb-line signal-to-noise ratio. The demonstrated resolution speed trade-off and femtometre-scale measurement capability establish this architecture to be well-suited for high-sensitivity, fast-response sensing applications.