Digital Signal Processing for Optical Communications and Networks

Abstract

T h ea c h i e v a b l ei n f o r m a t i o nr a t e so fo p t i c a lcommunication networks have been widelyincreased 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 next-generation optical communication networks to achieve a performance close to the Shannon capacity limit. This chapter will focus on the introduction and investigation of digital signal processing employed for channel impairments compensation based on the coherent detection of optical signals, to provide a roadmap for the design and implementation of real-time optical fiber communication systems.

Graphene-based integrated photonics for next-generation datacom and telecom

“…In datacom, link lengths are shorter, hence, smaller extinction ratios are tolerable in some cases, because the priority is to reduce size [293], insertion loss and power consumption [293].In telecoms, the penalty contributions arise from chromatic dispersion, channel losses, nonlinearities and accumulated amplified spontaneous emission noise of erbium doped optical amplifiers [85]. Although chromatic dispersion can be managed by a combination of appropriate signal coding and digital post-processing at the receiver [294] and losses can be compensated by optical amplifiers, nonlinearities and noise remaincrucial impairment factors [85].…”

Performance analysis of symmetrical and bidirectional 40 Gbps TWDM-PON employing m-QAM-OFDM modulation with multi-color LDs based VLC system

“…ℎ means the adaptive FIR filter with tap coefficient. Moreover, frequency domain equalizers are mostly used as a most popular and promising CD filters and its transfer function for coherent transmission system is represented in equation ( 15) (Xu 2017). After two polarization channels separation by the adaptive equalizer, phase-tracking is done in digital domain.…”

“…To recover and remove the persisting phase mismatch between the signal and the local oscillator, CPE process is used (Renaudier et al 2010). For CPE one-tap normalized LMS filter is effectively employed for coherent m-QAM transmission in the proposed system and the tap weight can be presented as (Xu 2017):…”

“…Also, means the step size in one-tap normalized LMS filter in the DSP unit. Thus BER in m-QAM coherent transmission system can be expressed as (Mandal et al 2021;Xu 2017):…”

Semiconductor Optical Amplifier (SOA)-Driven Reservoir Computing for Dense Wavelength-Division Multiplexing (DWDM) Signal Compensation

“…[1][2][3]. However, the advanced modulation format, e.g., high-order quadrature-amplitude modulation (QAM), requires a higher optical signal-to-noise ratio (OSNR), resulting in optical signal processing (OSP) as the crucial function at the optical receiver [4][5][6]. A digital signal processing (DSP)based OSP could perform the functions of frequency and phase estimation, dispersion compensation, channel equalization, etc., enabling mitigation of impacts from the linear or nonlinear effects in the transmission link.…”