Monolithically Integrated Laser Chip for Interrogation of Large-Capacity Weak Fiber Bragg Grating (WFBG) Arrays

We report a monolithically integrated distributed feedback multiwavelength laser array (DFB-MLA) photonic chip for large capacity interrogation of weak fiber Bragg grating (WFBG) arrays. The chip integrates multiwavelength generation, optical power combining, power equalization, and pulse gating on a single InP platform. Based on the reconstruction-equivalent-chirp (REC) technique, the 8 × 3 laser array exhibits an adjacent-channel wavelength spacing of approximately 2.5 nm and a total tuning range of 60 nm. In the photonic chip, the outputs of different channels are combined through an on-chip three-stage Y-branch combiner and subsequently pass through two functionally separated semiconductor optical amplifiers (SOAs). The power-equalization SOA (PE-SOA) compensates for wavelength-dependent power variations, reducing the interchannel power variation from approximately 10 to 0.3 dB. The pulse-gating SOA (PG-SOA) converts the continuous wavelength-swept output into optical pulses for time-domain addressing. Based on a time- and wavelength-division multiplexing (TWDM) scheme, the chip-based demodulation system successfully demodulated 100 WFBGs with a spatial interval of 0.2 m between adjacent gratings. These results demonstrate the potential of the integrated photonic source for compact, large-capacity optical fiber sensing systems.