PDM Signal Amplification Using PPLN-Based Polarization-Independent Phase-Sensitive Amplifier

We demonstrate the first polarization-independent phase-sensitive amplification of a polarization-division multiplexing (PDM) signal. A novel polarization-diversity loop configuration using periodically poled LiNbO3 waveguides is proposed to achieve the polarization-independent amplification of both a single-polarized signal and a PDM signal. The proposed configuration provides two independent optical parametric amplification processes for two orthogonal polarization components in the loop, while preventing the amplification of the reflection noise by a counter-propagating pump. Polarization-independent error-free operation was confirmed with a bit-error-rate measurement for a 40-Gb/s quadrature phase-shift keying (QPSK) signal. We then demonstrated the phase regenerative amplification of an 80-Gb/s PDM-QPSK signal with artificial phase noise.