Step-size selection for split-step based nonlinear compensation with coherent detection in 112-Gb/s 16-QAM transmission

Non-uniform step-size distribution is implemented for split-step based nonlinear compensation in singlechannel 112-Gb/s 16 quadrature amplitude modulation （QAM） transmission. Numerical simulations of the system including a 20 × 80 km uncompensated link are performed using logarithmic step size distribution to compensate signal distortions. 50% of reduction in number of steps with respect to using constant step sizes is observed. The performance is further improved by optimizing nonlinear calculating position （NLCP） in case of using constant step sizes while NLCP optimization becomes unnecessary when using logarithmic step sizes, which reduces the computational effort due to uniformly distributed nonlinear phase for all successive steps.

Scalable nonlinear equalization in high-bit-rate optical transmission systems

In this paper,we report on the performance comparison of all-optical signal processing methodologies to compensate fiber transmission impairments,namely chromatic dispersion and nonlinear distortion caused by the Kerr effect,in a coherent 112 Gbit∕s dual-polarization 64 bit quadrature amplitude modulation system over 800 km standard single-mode fiber.We numerically compare optical backward propagation(OBP)with optical phase conjugation(OPC)techniques,namely.mid-link spectral inversion,predispersed spectral inversion,and OPC with nonlinearity module.We also evaluate a self-phase-modulation-based optical limiter with an appropriate prechirping to compensate for the intensity fluctuations as a hybrid approach with OBP.The results depict improvement in system performance by a factor of∼4 dB of signal input power by all-optical signal processing methods,which is comparative with ideal digital backward propagation where the high complexity is the intrinsic impediment in the real-time implementation of the technique with coherent receivers.