It is known that fiber nonlinearities induce crosstalk in a wavelength division multiplexed (WDM) system, which limits the capacity of such systems as the transmitted signal power is increased. A network user in a WDM system is an entity that operates around a given optical wavelength. Traditionally, the channel capacity of a WDM system has been analyzed under different assumptions for the transmitted signals of the other users, while treating the interference arising from these users as noise. In this paper, we instead take a multiuser information theoretic view and treat the optical WDM system impaired by cross-phase modulation and dispersion as an interference channel. We characterize an outer bound on the capacity region of simultaneously achievable rate pairs, assuming a simplified K-user perturbative channel model using genie-aided techniques. Furthermore, an achievable rate region is obtained by time-sharing between certain single-user strategies. It is shown that such time-sharing can achieve better rate tuples compared to treating nonlinear interference as noise. For the single-polarization single-span system under consideration and a power 4.4 dB above the optimum launch power, treating nonlinear interference as noise results in a rate of 1.67 bit/sym, while time-sharing gives a rate of 6.33 bit/sym.
翻译:众所周知,纤维非线性会在波长分多维化(WDM)系统中诱导交叉跟踪,从而限制传输信号功率等系统的能力。WDM系统中的网络用户是围绕某一光波长运作的实体。传统上,WDM系统的频道能力是根据其他用户传送信号的不同假设进行分析的,同时将来自这些用户的干扰作为噪音处理。在本文中,我们采用多用户信息理论视角,将受到跨阶段调制和分散影响的光学WDM系统作为干扰通道处理。我们把同时可实现的电率配对的容量区域外缘区域定性为同时可实现的电率配对,假设使用基因辅助技术的简化K用户渗透性信道模型。此外,通过某些单一用户战略之间的时间共享,可以实现可实现的电速率区域,而将非线性干扰作为噪音处理。对于正在审议的单级单级单级调频波系统,以及超过最佳发射速率4.4 dB,同时将非线干涉率率作为6.33的比位干涉率处理。