Digital Signal Processing for Optical Communications and Networks I: Linear Compensation

The achievable information rates of optical communication networks have been widely increased over the past four decades with the introduction and development of optical amplifiers, coherent detection, advanced modulation formats, and digital signal processing techniques. These developments promoted the revolution of optical communication systems and the growth of Internet, towards the direction of high-capacity and long-distance transmissions. The performance of long-haul high-capacity optical fiber communication systems is significantly degraded by transmission impairments, such as chromatic dispersion, polarization mode dispersion, laser phase noise and Kerr fiber nonlinearities. With the entire capture of the amplitude and phase of the signals using coherent optical detection, the powerful compensation and effective mitigation of the transmission impairments can be implemented using the digital signal processing in electrical domain. This becomes one of the most promising techniques for nextgeneration optical communication networks to achieve a performance close to the Shannon capacity limit. Chromatic dispersion can be compensated using the digital filters in both time domain and frequency domain. Polarization mode dispersion can be equalized adaptively using the least-mean-square method and constant modulus algorithm. Phase noise from laser sources can be estimated and compensated using the feed-forward and feed-back carrier phase estimation approaches. Kerr fiber nonlinearities, including self-phase modulation, cross-phase modulation and fourwave mixing, can be mitigated using single-channel digital back-propagation and In-doc controls