| 摘要 |
The present invention provides an optical transmitter, an optical transmission system and a modulation scheme selection method capable of selecting either of an optical duobinary modulation scheme and an optical DPSK modulation scheme. The optical transmitter according to the present invention includes a first exclusive OR circuit which outputs as a first output signal the exclusive OR of binary logic signals input from first and second input terminals, a delayer which delays the first output signal by a predetermined amount and outputs the delayed signal to the second input terminal, a low-pass filter which receives the first output signal as an input, converting the first output signal into a three-value signal and outputting the three-value signal as a second output signal, and a selector which selects one of the first output signal and the second output signal on the basis of a selection signal and outputs the selected signal.
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