Anatomy of a Digital Coherent Receiver

Abstract

SUMMARYDigital coherent receivers have gained significant attention in the last decade. The reason for this is that coherent detection, along with digital signal processing (DSP) allows for substantial increase of the channel capacity by employing advanced detection techniques. In this paper, we first review coherent detection technique employed in the receiver as well as the required receiver structure. Subsequently, we describe the core part of the receiver -DSP algorithms -that are used for data processing. We cover all basic elements of a conventional coherent receiver DSP chain: deskew, orthonormaliation, chromatic dispersion compensation/nonlinear compensation, resampling and timing recovery, polarization demultiplexing and equalization, frequency and phase recovery, digital demodulation. We also describe novel subsystems of a digital coherent receiver: modulation format recognition and impairment mitigation via expectation maximization, which may gain popularity with increasing importance of autonomous networks.

Low-penalty up to 16-QAM wavelength conversion in a low loss CMOS compatible spiral waveguide

“…The received waveforms from the digital sampling oscilloscope (DSO, 80 Gsamples/s, 33 GHz) were processed by offline digital signal processing (DSP) [16] including adaptive time-domain equalization using constant and multimodulus algorithms, carrier recovery by decision-directed phase lock loop and error vector magnitude (EVM) measurements followed by bit error rate (BER) estimation based on the EVM [17].…”

Effective Linewidth of Semiconductor Lasers for Coherent Optical Data Links

“…The receiver consists of an integrated coherent receiver, an ECL and a digital storage oscilloscope (DSO). Data demodulation is performed offline using standard DSP algorithms as described in [22]. The CPR algorithm used is again BPS [21].…”

Impairment mitigation in superchannels with digital backpropagation and MLSD

“…This value was chosen to match the specifications of standard commercial devices. A set of DSP algorithms [16] was applied to compensate for channel impairments and estimate the transmitted data: decimation to 2 samples/symbol, frequency domain chromatic dispersion equalization or DBP, adaptive equalization with the constant modulus algorithm (CMA, 21 taps) for DP-QPSK, and multi-modulus algorithm (MMA, 21 taps) for DP-16QAM, carrier recovery (digital PLL), maximum likelihood sequence detection (MLSD), digital demodulation and error counting. The adaptive equalizer was used to approximate the matched filter at the receiver for each tested configuration.…”