Timing Recovery For High Speed Coherent Optical Receiver

With the evolution of computer networks, people are increasingly demanding highdata bandwidth, such as LTE and3G. Currently, a40Gb/s backbone networktechnology has been commercialized. However, a100Gb/s backbone network is alsobeing tested, but that’s just for a short time to ease the pressure on network bandwidth.In recent years, most of the communication equipment manufacturers are graduallyfocusing on the400Gb/s transmission network instead of100Gb/s or40Gb/s. Thisthesis is about timing recovery (also known as clock recovery) for a high-speed opticalcoherent transmission system. This technology is a key technology of the400Gb/stransmission network. It is also one of the research focuses for optical communicationtechnology currently. The contents of this work are presented below.A study of the key technologies of200Gb/s PM-NRZ-16QAM optical coherenttransmission systems is done, then VPI and MATLAB are utilized to build a systemsimulation platform. The transmitter and fiber channel are built in a VPI transmissionmaker to ensure the accuracy of the channel model, and the receiver’s DSP algorithmsare tested by MATLAB.This thesis has focused on the design of the system’s timing recovery algorithm andsimulations have been done by MATLAB. The advantages and disadvantages of thedifferent timing recovery algorithms are compared. The algorithm has been optimizedfor the high-speed16QAM optical coherent transmission systems. The results of timingrecovery algorithms that run under different channels are shown.A simulation of the different degree of channel impairments (such as noise, CD,PMD) for the timing recovery is done. Because the timing recovery algorithm issensitive to the chromatic dispersion (CD) and polarization mode dispersion (PMD), thestudies of CMA, MMA, DD-LMS algorithm are necessary.Due to chromatic dispersion(CD) and polarization mode dispersion (PMD), a CMA/MMA/DD-LMS filter equalizeris designed to enhance the timing recovery performance and robustness.Improvement of stability and timeliness for timing recovery is necessary to makethe system adapt better to future commercialization. A multi-level timing recovery structure to ensure the stability and performance of timing recovery is also proposed inthis paper.