Tradeoff Between Reach and Security in Nyquist WDM Transmission of PSK Y-00 Quantum Stream Cipher

Y-00 quantum stream cipher is a signal-level encryption technique that prevents signal interception in optical fiber communications. Security of the Y-00 cipher depends on the signal power, and thus the cipher system has a tradeoff between the security and signal quality. This letter reports theoretical analysis of Nyquist wavelength-division multiplexed transmission of phase-shift keying Y-00 cipher over a nonlinear fiber channel. A tradeoff formula between reach and signal security is derived utilizing the Gaussian noise model. Numerical study shows that the PSK Y-00 cipher achieves high-capacity ultra-long-haul transmission with a countermeasure against interception.