Polarization Independent Phase-OFDR in Rayleigh-Based Distributed Sensing

Phase change of Rayleigh scattering along a SMF can be measured in OFDR to provide distributed strain or temperature sensing with high spatial resolution and high accuracy. However, the polarization state (SOP) change in SMF will lead to failure of phase measurement in a traditional OFDR system. In this paper, OFDR with polarization diversity launch and detection is used to obtain two fiber core responses in response to two orthogonal incident SOPs for phase calculation. A phase algorithm is investigated to obtain stable phase change with high accuracy, which is independent to incident SOP and birefringence in the sensing fiber. Additionally, a misalignment compensation scheme using reference look-up-table (LUT) is proposed to compensate misalignment and enhance the computational efficiency. Experimental results demonstrate continuous phase change calculated along the fiber with birefringence is independent to SOP change, and 0.4 rad accuracy can be obtained. In addition, strain can be measurement with 5 μϵ accuracy in 1mm spatial resolution. The proposed method has potential to high performance Rayleigh-based distributed sensing and shape sensing.