Coherent Optical Pulse Phase Rotation Reflectometry Insensitive to I/Q Quadrature Imbalance

The In-Phase/Quadrature (I/Q) imbalance is a limiting factor for accurate phase demodulation in coherent communication systems. Recently, the 90° optical/electrical hybrid I/Q demodulator have been introduced into distributed optical fiber sensor (DOFS) system to significantly reduce the phase measurement time but concurrently bring the limitation of I/Q quadrature imbalances that might corrupt the accuracy of the measured phase signal. This paper introduces a novel coherent optical pulse phase rotation reflectometry (COPPRR) system insensitive to I/Q quadrature imbalance. The theoretical basis of the COPPRR system is the optical pulse phase rotation and integration (PRI) technique that stipulates the use of integration of N groups of I/Q signals with regular phase-shift to mutually eliminate the effects of quadrature imbalance carried in the individual pair of signals. Experimental results effectively demonstrated a phase recovery of 100 Hz sinusoidal vibration robust against various types of simulated quadrature imbalance where the I/Q demodulation completely failed to restore the phase signal.