摘要
本文论述相干光纤通信比常规光纤通信的优点。接收端的检测方式有外差检测和零差检测两种,都比常规直接检测有较高的接收机灵敏度。发送端的数字调制方式有移频键控FSK、连续相位移频键控CPFSK,移相键控PSK、差分DPSK,它们的灵敏度和线宽要求各不相同。于是详细说明FSK和CPFSK外差系统的构成和性能。再说明相干通信对单频激光管相位噪声和线宽的要求,表示有必要使用分布反馈DFB结构。又说明双PIN的平衡混频器。其后,叙述实验系统码速-距离乘积的进展,目前的记录是400Mb/s-290km和2Gb/s200km。由于相干通信使邻路光频相隔很近,容许实现密集光载波FDM,理论上可达1000路。又简单提到相位分集接收和偏振分集接收,以改善系统性能。最后,扼要介绍相干光纤通信在市内网应用的设想。相干通信分强相干、中等相干、弱相干三类,现时应用大多是中等相干光纤通信,一俟光电子集成成功,定有广泛应用。
This paper reviews the advantages of the coherent optical fiber communication systems over the conventional systems. There are two kinds of detection schemes: heterodyne and homodyne detection, they provide higher receiver sensitivity than direct detection. On the other hand, there are two kinds of digital modulation schemes: FSK,CPFSK,and PSK.DPSK, their receiver sensitivity and linewidth requirements are dif- ferent from each other. Then the paper discusses the requirments to single frequency laser, including phase noise and linewidth.It shows that DFB structure is desirable. The dual-PIN balanced mixer used for heterodyne detection is mentioned. The progress of bitrate-distancc product of experimental system is discribed, up to now,the best records ars 400 Mb/s-290 km and 2 Gb/s-200km. Since the coherent optical fiber communication offers very close channel spacing, it allows densely packed FDM operation, theorectically up to 1000 channels of optical carriers. The use of phase diversity reception and polarization diversity reception to improve the system performance is briefly described. Finally the paper briefly mentions the possible application of the coherent fiber communication in local subscriber network. There are highly -coherent, medium-coherent and weakly-coherent systems, present applications are mostly of medium-coherent optical fiber communications, which will be widely used after the opto-electronic integration OEIC becomes successful.
出处
《光通信研究》
1989年第1期1-11,共11页
Study on Optical Communications
