| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized and easily mounted wavelength conversion circuit increasing a modulation speed than a reflection type. SOLUTION: A Mach-Zehnder type optical circuit 13 is constituted of a first semiconductor optical amplifier 13-1 connecting one side output port of a first optical coupling circuit to one side input port a second optical coupling circuit and provided with a phase adjusting area 13-3 and a second semiconductor optical amplifier 13-2 connecting the other side output port of the first optical coupling circuit to the other side input port of the second optical coupling circuit. The waveguide of the semiconductor optical amplifier of the optical circuit 13 is made a U-shaped bent structure, and the input end and output end of the semiconductor optical amplifier are placed on the same facet. Thus, a reflection preventive film 12 is formed collectively, and the optical circuit 13 is used as a traveling-wave type semiconductor optical amplifier. Modulation beamsλ1,λ2 are inputted to the semiconductor optical amplifiers 13-1, 13-2 through wavelength multiplexer/demultiplexer circuits 14, 15, and the beam of the wavelength different from the modulation beam passing through the semiconductor optical amplifier is modulated according to the modulation beam.
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