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Frontiers of Optoelectronics

Front Optoelec Chin    2011, Vol. 4 Issue (3) : 288-291     DOI: 10.1007/s12200-011-0140-2
RESEARCH ARTICLE |
Compensation of quadrature imbalance in an optical coherent OQPSK receiver in presence of frequency offset
Xinying LI, Bo HUANG, Yufeng SHAO, Junwen ZHANG, Shumin ZOU, Wuliang FANG, Li TAO, Jiangbo ZHU, Chi NAN()
Department of Communication Science and Engineering, State Key Laboratory of Application Specific Integrated Circuit (ASIC) and System, Fudan University, Shanghai 200433, China
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Abstract

In this paper, we describe the impact of quadrature imbalance (QI) in the presence of frequency offset in an optical coherent offset quadrature phase shift keying (OQPSK) receiver. Arbitrary conjugate misalignment was realized in a 2×4 90° optical hybrid, and the ellipse correction (EC) method of quadrature imbalance was applied in our simulation. In the case of transmission, the EC method can significantly improve the system performance.

Keywords offset quadrature phase shift keying (OQPSK)      quadrature imbalance (QI)      ellipse fitting      frequency offset     
Corresponding Authors: NAN Chi,Email:nanchi@fudan.edu.cn   
Issue Date: 05 September 2011
 Cite this article:   
Junwen ZHANG,Shumin ZOU,Xinying LI, et al. Compensation of quadrature imbalance in an optical coherent OQPSK receiver in presence of frequency offset[J]. Front Optoelec Chin, 2011, 4(3): 288-291.
 URL:  
http://journal.hep.com.cn/foe/EN/10.1007/s12200-011-0140-2
http://journal.hep.com.cn/foe/EN/Y2011/V4/I3/288
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Junwen ZHANG
Shumin ZOU
Xinying LI
Bo HUANG
Yufeng SHAO
Wuliang FANG
Li TAO
Jiangbo ZHU
Chi NAN
Fig.1  Simulated optical coherent OQPSK system
Fig.2  EC method by transformation of Eq. (3)
Fig.3  (a) Ideal constellation; (b) impact of QI; (c) impact of frequency offset; (d) impact of QI in presence of frequency offset
Fig.4  (a) Received constellation; (b) after CD compensation; (c) fit constellation into ellipse; (d) transform ellipse into circle; (e) after frequency error correction; (f) after phase error correction
Fig.5  (a) Received constellation; (b) after CD compensation; (c) after frequency error correction; (d) after phase error correction
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