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Proceedings Paper

An improved adaptive interpolation clock recovery loop based on phase splitting algorithm for coherent optical communication system
Author(s): Xuan Liu; Bo Liu; Li-jia Zhang; Xiang-jun Xin; Qi Zhang; Yong-jun Wang; Qing-hua Tian; Feng Tian; Ya-ya Mao
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Paper Abstract

Traditional clock recovery scheme achieves timing adjustment by digital interpolation, thus recovering the sampling sequence. Based on this, an improved clock recovery architecture joint channel equalization for coherent optical communication system is presented in this paper. The loop is different from the traditional clock recovery. In order to reduce the interpolation error caused by the distortion in the frequency domain of the interpolator and to suppress the spectral mirroring generated by the sampling rate change, the proposed algorithm joint equalization, improves the original interpolator in the loop, along with adaptive filtering, and makes error compensation for the original signals according to the balanced pre-filtering signals. Then the signals are adaptive interpolated through the feedback loop. Furthermore, the phase splitting timing recovery algorithm is adopted in this paper. The time error is calculated according to the improved algorithm when there is no transition between the adjacent symbols, making calculated timing error more accurate. Meanwhile, Carrier coarse synchronization module is placed before the beginning of timing recovery to eliminate the larger frequency offset interference, which effectively adjust the sampling clock phase. In this paper, the simulation results show that the timing error is greatly reduced after the loop is changed. Based on the phase splitting algorithm, the BER and MSE are better than those in the unvaried architecture. In the fiber channel, using MQAM modulation format, after 100 km-transmission of single-mode fiber, especially when ROF(roll-off factor) values tends to 0, the algorithm shows a better clock performance under different ROFs. When SNR values are less than 8, the BER could achieve 10-2 to 10-1 magnitude. Furthermore, the proposed timing recovery is more suitable for the situation with low SNR values.

Paper Details

Date Published: 10 January 2018
PDF: 9 pages
Proc. SPIE 10617, 2017 International Conference on Optical Instruments and Technology: Optoelectronic Devices and Optical Signal Processing, 106170S (10 January 2018); doi: 10.1117/12.2295352
Show Author Affiliations
Xuan Liu, Beijing Univ. of Posts and Telecommunications (China)
Bo Liu, Nanjing Univ. of Information Science and Technology (China)
Li-jia Zhang, Beijing Univ. of Posts and Telecommunications (China)
Xiang-jun Xin, Beijing Univ. of Posts and Telecommunications (China)
Qi Zhang, Beijing Univ. of Posts and Telecommunications (China)
Yong-jun Wang, Beijing Univ. of Posts and Telecommunications (China)
Qing-hua Tian, Beijing Univ. of Posts and Telecommunications (China)
Feng Tian, Nanjing Univ. of Information Science and Technology (China)
Ya-ya Mao, Nanjing Univ. of Information Science and Technology (China)


Published in SPIE Proceedings Vol. 10617:
2017 International Conference on Optical Instruments and Technology: Optoelectronic Devices and Optical Signal Processing
Liquan Dong; Yi Dong; Jian Chen; Fabien Bretenaker, Editor(s)

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