| 摘要 |
PROBLEM TO BE SOLVED: To control the gain of a signal light to be constant, by making the signal light of optional integer wavelength a monitor signal light, and performing the adjustment so that the gain of signal light may come to a fixed value in case of the singular wavelength, and adjusting the quantity of excited light so that the average value of the ripple of the gain of signal light may be minimum in case of a plurality of wavelengths. SOLUTION: Out of the signal lights of n wavelength (n is an integer not less than 1), the signal light of optional m wavelength (m is an integer not less than 1 and not more than n) is made a monitor signal light. This gain control decreases the quantity of excited light so that the gain of the signal light of monitor wavelength may come to a fixed value, making one signal wavelength 1570 nm or the like the monitor wavelength. Hereby, the maximum gain ripple can be suppressed to about 0.2 dB (1598 nm) in all channels, and even in case that the monitor wavelength is changed to 1598 nm or the like, the maximum gain ripple can be suppressed to about 0.5 dB or under. Moreover, it becomes the same results, even if it monitors two waves or more, and controls the average value of the ripple of the gain of each signal light to be minimum. Hereby, the gain can be controlled to be constant. |
