Hardware-efficient phase noise compensation for km-scale and mm-level resolution OFDR.

We demonstrate a hardware-efficient, linewidth-tolerant OFDR system that eliminates the need for an independent auxiliary receiver and a high hardware sampling rate. Using a multiplexed delay configuration, a single integrated coherent receiver simultaneously captures the laser phase noise reference and sensing signal. By introducing an upsampling process in the phase noise compensation algorithm, the unnecessary sampling rate overhead in the experiment is avoided. Finally, using a 200 kHz linewidth laser, the system achieves a 1.5 mm spatial resolution over a 1.9 km fiber, proving its high practicality for low-cost and high-performance distributed fiber sensing.