Coherent optical communication is a technology in the field of optical fiber communication. It mainly uses coherent modulation technology at the sending end and heterodyne detection technology at the receiving end for information transmission. During transmission, the wavelength is the same, the vibration direction is the same, and the phase difference is constant.
Compared with traditional incoherent optical communication, coherent optical communication has the technical advantages of longer transmission distance, larger transmission capacity and higher receiving sensitivity, so it has attracted wide attention from all walks of life in the industry.
In the 1980s, countries such as the United Kingdom, the United States, and Japan conducted a lot of research on coherent technology. AT&T and Bell Laboratories conducted 1.3 μm coherent experiments in 1989 and 1990 between two sites 35 kilometers apart in Pennsylvania. And 1.7G signal with 1.55μm wavelength without repeater coherent transmission experiment. In the 1990s, people found that the combination of DWDM+EDFA technology can solve the problem of optical communication expansion and long-distance transmission more simply and effectively, so the development of coherent transmission technology is temporarily sluggish.
Around 2008, with the development of the mobile Internet, the network data traffic increased explosively, and the backbone network (>1000 kilometers) and the metropolitan area network (100-1000 kilometers) faced a sharp increase in the pressure of upgrading and expansion. At this time, DWDM+EDFA technology has already Going to the extreme, the development potential is getting smaller and smaller. On the other hand, with the maturity of DSP and optical device technologies, coherent optical communication based on these technologies is suitable for relaying DWDM+EDFA technology and breaking the technical bottleneck of long-distance and large-bandwidth optical fiber communication. Therefore, coherent optical communication ushers in a second opportunity for development.
The explosion of data traffic has also promoted the large-scale construction of data centers, and then the development of cloud computing has changed the IT infrastructure of data centers, making distributed data centers mainstream. Distributed data centers need to communicate with each other in order to share data, balance loads, provide backup, and expand capacity when needed. Due to its large bandwidth and long-distance optical interconnection requirements (80-120km), distributed data centers urgently need the support of coherent transmission technology.
To sum up, the upgrade and expansion of the backbone network and metropolitan area network, as well as the optical interconnection of the data center, all urgently need the support of coherent optical transmission technology.