The invention provides a signal light outputting apparatus for use for optical communication by wavelength multiplex transmission and an optical transmission system with the same wherein control of powers and/or wavelengths of signal lights to be transmitted can be performed with certainty and the signal lights can be transmitted and received accurately while making transmission characteristics of the signal lights equal to each other. The signal light outputting apparatus includes a plurality of signal light outputting units (15-1 to 15-n) each including a signal light source (11-1 to 11-n) and an optical amplifier (14-1 to 14-n), an optical combiner (16) for combining signal lights outputted from the signal light outputting units (15-1 to 15-n), a signal light power detector (18) for extracting part of signal light combined by the optical combiner (16) to detect powers of the signal light for individual wavelengths corresponding to the signal light wavelengths, and a signal light output control element (19) for controlling signal light outputs of the corresponding optical amplifiers (14-1 to 14-n) for amplification of the signal lights of the wavelengths in response to the powers of the signal lights of the individual wavelengths detected by the signal light power detector (18). <IMAGE>
Optical signal tranmsitting apparatus and optical transmission system having such an optical signal transmitting apparatus