| 摘要 |
An optical transmitter includes an optical modulator, an optical coupler, a crosspoint monitoring unit, a reference-value setting unit, and a bias circuit. The optical coupler splits an optical signal output from the optical modulator into a plurality of optical signals. The crosspoint monitoring unit receives part of the optical signals, and monitors a crosspoint of the optical signal output from the optical modulator. The reference-value setting unit sets a bias reference value to be assigned to the optical modulator based on an output of the crosspoint monitoring unit so that the crosspoint is constant. The bias circuit applies a bias to the optical modulator based on the bias reference value.
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