Physical layer encryption for polarization division multiplexing coherent optical communication system based on the rotation of the state of polarization

In this paper, we propose an optical physical layer encryption method to encrypt the signal of polarization division multiplexing (PDM) coherent optical communication system by introducing an artificially controlled fast rotation of the state of polarization (RSOP) into the signal. Simulations conducted in a 40 Gbps PDM-QPSK system show that the authorized user can successfully decrypt the received signal, while the eavesdroppers cannot derive useful information with bit error rates (BER) at 0.38~0.48, which shows that the method effectively improves the security of the system.