Coherent optical communication technology features and benefits

Coherent optical communication full use of coherent communication has the mixer gain, excellent channel selectivity and adjustable features. Compared with IM/DD system, coherent optical communication system has the following unique advantages:

1. High sensitivity, long distance relay

Coherent optical communications is a major advantage of enabling coherent detection, thereby improving the sensitivity of the receiver. In the coherent optical communication system, the coherent mixing light output current size of the signal light power and the local oscillator optical power proportional to the product. Under the same conditions, the coherent receiver to improve receiver sensitivity than the average of about 18dB, can achieve close to the shot noise limit performance, and therefore increase the unrepeated transmission distance of optical signals.

2. selectivity, large communication capacity

Another major advantage of coherent optical communication is that it can improve the selectivity of the receiver. In direct detection, the reception band is wider, to suppress interference noise, usually takes place before the detector narrowband filter, but the band is still very wide. Coherent heterodyne detection, the probe is a signal light and LO light of the mixed light, so only in the frequency band noise in the system before they can enter, while others are relatively narrow bandwidth microwave noise IF amplifier filtered out. Visible, heterodyne detection has good filtering properties, which will play a major role in the coherent optical communication applications. Furthermore, since the coherent detection excellent wavelength selectivity, coherent receiver can make the frequency spacing WDM system greatly reduced, that is, dense wavelength division multiplexing (DWDM), to replace the traditional light multiplexing of large frequency interval, having a wave division multiplexing potential advantages to achieve higher transfer rates.

3. You can use the equalization electronics to compensate for fiber dispersion effect of light pulses

If heterodyne detection of coherent optical communication transmission function of the IF filter transfer function coincided with the opposite optical fiber, optical fiber can reduce the influence of the dispersion of the system.