HIGH OUTPUT OPTICAL TRANSMITTER

PROBLEM TO BE SOLVED: To suppress a residual intensity modulation component by modulating a light source with a low frequency signal whose frequency is less than a low cut-off frequency of an optical amplifier means and amplifying an optical signal from the optical modulation means with the optical amplifier means in the saturated state. SOLUTION: An optical signal from a light source 11 is modulated by a very small frequency with a low frequency signal (a) and an output light (b) is outputted as an optical signal (c) from an optical modulator 13. A synthesizer of an optical fiber amplifier 14 synthesizes the optical signal (c) with an excited light from an excited light source 16 and the result is given to an erbium added optical fiber 17. In this case, the excited light source 16 is controlled by an excited light source drive current constant control circuit 18 so as to make the excited power constant thereby bringing the optical fiber amplifier 14 to be in a saturated state. Then the modulation frequency of the light source 11 is set less than the low cut-off frequency of the optical fiber amplifier 14, then the residual intensity modulation component produced when the carrier line width of the light source 11 is suppressed.