| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor optical amplifier whose gain can be kept constant at all times, without increasing the size or the cost. SOLUTION: The semiconductor optical amplifier 11-1 to 11-(n+1) comprises n semiconductor optical amplifiers 11-1 to 11-n, for amplifying an inputted optical signal and one semiconductor optical amplifier 11-(n+1) for monitoring, with all of them being formed into an array without being separated by the chip. An optical monitor 12 monitors the optical power of spontaneous emission light outputted by the semiconductor light amplifier 11-(n+1) for monitoring. Meanwhile, an automatic gain controller 2 controls the bias current of the semiconductor light amplifier 11-(n+1) for monitoring, so that the optical power of the spontaneous emission light from the optical monitor may be constant, while monitoring the bias currents of n semiconductor optical amplifiers 11-1 to 11-n in a similar manner, as with the semiconductor optical amplifier 11-(n+1) for monitoring. |
