| 摘要 |
PROBLEM TO BE SOLVED: To improve the ability to keep track of phase fluctuations of a light source, thereby reducing the occurrence of a transmission error.SOLUTION: A digital coherent receiver 1 comprises: a multiplier 51 for generating an equalization value zby multiplying an input symbol xby a tap coefficient c; output symbol estimation units 52, 53 for estimating and outputting ideal symbol coordinates on the basis of the equalization value z, and also generating a coordinate error e^which is a difference value between the equalization value zand ideal symbol coordinates; and a tap coefficient update unit 54 for calculating a tap coefficient cfor the next input symbol. The output symbol estimation unit 52 sets a threshold larger than a distance from the origin of quasi-farthest symbol coordinates whose distance from the origin is second farthest among the ideal symbol coordinates, and, when a distance from the origin of the equalization value zis determined to be larger than the threshold, estimates the equalization value zas farthest symbol coordinates whose distance from the origin is farthest among the ideal symbol coordinates. |
