Optical receiver and slice level control method

A slice level control method of setting an optimal point of a slice level for a first discriminator of an optical receiver that includes the first discriminator that compares a received signal to the slice level and discriminately outputs the received signal;

• a second discriminator that is connected in parallel to the first discriminator, compares the received signal to a slice level, and discriminately outputs the received signal;
• and
• a computing device that variably controls the slice level of the first and the second discriminators, respectively, the slice level control method comprising:
• executing, by the computing device, a first process of:
• setting the slice level of the first discriminator to be a predetermined slice level,
• calculating a pseudo error rate obtained when the slice level of the second discriminator is caused to variably scan, and
• setting the slice level of the first discriminator within a range in which the error rate does not vary.