Monitor circuit for monitoring property of optical fiber transmission line and quality of optical signal

摘要

An optical reception circuit (10) generates optical electric field data by performing coherent reception of an optical signal transmitted via an optical fiber transmission line (3). An FIR filter (21) filters the optical electric field data so that the optical signal is equalized. A quality monitor unit (24) calculates the average value and the standard deviation value of the amplitude of the optical signal on the basis of the equalized optical electric field data, and further calculates an optical signal-to-noise ratio on the basis of the calculated values.