VCO clock synchronization loop combined with dispersion equalization in optical coherent receivers

In optical coherent receivers,the timing error detector （TED） in synchronization loop can not work normally when signal is distorted by large dispersion.This paper proposes a novel clock synchronization scheme which adds a butterfly-structured adaptive equalizer to the loop to fulfill synchronizations,equalizations and polarization de-multiplexing of two polarization states simultaneously under the control of single voltage-controlled oscillator （VCO）.Simulink simulation demonstrates the rationality and the feasibility of the combined loop with single VCO.

Spectrally sliced heterodyne coherent receiver with halved electrical bandwidth

A spectrally sliced heterodyne coherent receiver(SHCR)employing four balanced photodetectors and analog-to-digital converters with half of the signal bandwidth is proposed to complete the signal reception and field recovery.We first numerically characterize the performance of SHCR compared with an intradyne coherent receiver and then validate the principle of the SHCR in a proof-of-concept single-polarization experiment.A 60 GBaud 16-quadrature amplitude modulation transmission is experimentally demonstrated over 80 km standard single-mode fiber with a bit-error-rate of 8.5×10^(-4) below the 7%hard-decision forward error correction threshold of 3.8×10^(-3).The SHCR offers a low-cost,hybrid-free,and channel-skew-tolerant candidate for data center interconnects.

Super-Receiver Design for Superchannel Coherent Optical Systems

In this paper, we propose a novel superreceiver architecture for Nyquistwavelengthdivision multiplexing （WDM） superchannel optical coherent systems. As opposed to a conventional coherent receiver, where each subchannel is demodulated independently, the proposed superreceiver jointly detects and demodulates multiple subchannels simultaneously. By taking advantage of information from side channels that use joint DSP to cancel interchannel interference （ICI）, the proposed super receiver performs much better than a conventional receiver. This architecture also has the potential to compensate for crosschannel impairments caused by linear and nonlinear effects. We examine the proposed architecture through experiment and simulation. OSNR is improved by more than 5 dB after 1280 km fiber transmission with narrow channel spacing.

Blind estimation of phase offset in OFDM subcarrier for coherent demodulation

An adaptive algorithm named low complexity phase off- set estimation （LC-POE） is proposed for orthogonal frequency division multiplexing （OFDM） signals. Depending on the requirement, the estimation procedure is divided into several scales to accelerate the adaptive convergence speed and ensure the estimation accuracy. The true phase offset is estimated through shrinking the detection range and raising the resolution scale step by step. Both the convergence performance and complexity are discussed in the paper. Simulation results show the effectiveness of the proposed algorithm. The LC-POE algorithm is promising in the application of OFDM systems.