| 摘要 |
PROBLEM TO BE SOLVED: To set the levels of signal light with respective wavelengths to be independent, to speed up and control the levels, to branch/insert the signal light and to equalize the levels without a loss by controlling injecting current, changing the gains of respective semiconductor optical amplifiers and equalizing the levels of the light of the respective wavelengths. SOLUTION: The light flowing in an optical transmission line 134 are branched by two routes by optical branching 740, and are inputted to the semiconductor optical amplifiers 441 and 442. When the both semiconductor optical amplifiers 442 and 443 are set in an off-state and the semiconductor optical amplifier 441 is set in an on-state, and when the semiconductor optical amplifiers 441 and 442 are set in the on-state and the semiconductor optical amplifier 443 is set in the off-state, the insertion loss of a switch becomes zero if the gain of the semiconductor optical amplifier 441 is made equal to the total of the losses of an optical branching unit 210, the optical transmission line 134, the optical branching 740 and 741 and an optical multiplexer 310. Namely, the levels can be equalized when the branching/inserting circuit is used. |
