Bangning Mao

Nonlinear impairment compensation using expectation maximization for dispersion managed and unmanaged PDM 16-QAM transmission

In this paper, we show numerically and experimentally that expectation maximization (EM) algorithm is a powerful tool in combating system impairments such as fibre nonlinearities, inphase and quadrature (I/Q) modulator imperfections and laser linewidth. The EM algorithm is an iterative algorithm that can be used to compensate for the impairments which have an imprint on a signal constellation, i.e. rotation and distortion of the constellation points. The EM is especially effective for combating non-linear phase noise (NLPN). It is because NLPN severely distorts the signal constellation and this can be tracked by the EM. The gain in the nonlinear system tolerance for the system under consideration is shown to be dependent on the transmission scenario. We show experimentally that for a dispersion managed polarization multiplexed 16-QAM system at 14 Gbaud a gain in the nonlinear system tolerance of up to 3 dB can be obtained. For, a dispersion unmanaged system this gain reduces to 0.5 dB.

112-Gbit/s × 4-lane duobinary-4-PAM for 400GBase

Novel duobinary-4-PAM signaling is experimentally demonstrated to support a 4-lane low-latency 400GbE client side solution. Direct detection of 112 Gbps transmission over a 5 km single wavelength and polarization fiber link is achieved.

A circuit enabling clock extraction in coherent receivers

We present a method for clock extraction in polarization multiplexed coherent optical systems using frequency domain timing phase detector. The phase detector input signal is pre-processed using a simplified polarizer transfer function enabling the maximum clock tone quality.

Digital Phase Detector for Nyquist and Faster than Nyquist Systems

The quality of clock tone in many practical phase detectors depends on the width of the non-zero portion of the signal spectrum. In Nyquist systems that deploy the raised-cosine filter, most of the known timing extraction methods completely fail when the roll-off factor (ROF) approaches the zero value. In this letter, we present a novel digital phase detector that is based on two samples per symbol with a performance that is practically independent of the shape of the Nyquist filter and modulation formats. Excellent timing-error detector performance is demonstrated even in extremely band-limited systems - the so-called faster than Nyquist systems (FTN).

Efficient and low-complexity chromatic dispersion estimation in coherent optical systems

In this paper, we present an accurate blind method for chromatic dispersion estimation in coherent optical receivers. The method is independent on modulation formats and signal spectra. Additionally, the estimation method is proven to be robust against sampling phase, polarization mode dispersion, carrier phase and frequency offset, and clock frequency offset. Excellent performance is demonstrated even in extremely bandlimited systems, so-called faster than Nyquist systems.

Adaptive joint carrier recovery and turbo decoding for nyquist terabit optical transmission in the presence of phase noise

An adaptive joint carrier recovery and soft LDPC turbo decoding scheme in the presence of nonlinear phase noise is proposed and experimentally verified with 1.9dB coding gain in Nyquist Terabit PDM-DQPSK systems.

Experimental demonstration of single-stage frequency domain equalization for single-carrier coherent receivers

Low complexity, single-stage frequency-domain equalization supported by blind CD estimation and training-aided 2×2 MIMO channel estimation is proposed and experimentally demonstrated in a 32 GBaud Nyquist PDM-QPSK transmission system.

Experimental Demonstration of Joint Frame Synchronization and Carrier-Frequency Estimation for Training-Aided Digital Coherent Receivers

Joint frame synchronization and carrier-frequency estimation employing CAZAC sequences is demonstrated in a 42.5 GBaud PDM-QPSK transmission system. Experimental verification has been performed on data transmitted over 1040 km of SSMF.