Optical transmitter, terminal-station apparatus having the optical transmitter and optical communication system, monitoring the optical transmitted signal

An optical transmitter, a terminal-station apparatus having the optical transmitter, and an optical communication system employing the terminal-station apparatus. The optical transmitter comprises: a light-source unit for generating an optical signal; a monitor unit for monitoring a parameter depending on the wavelength of the optical signal; a judgment unit for determining as to whether or not the monitored parameter satisfies a predetermined condition; and a shut-off unit for shutting off the optical signal in case the monitored parameter does not satisfy the predetermined condition. By using the optical transmitter, it can be possible to prevent crosstalk from occurring between WDM (Wavelength Division Multiplexing) channels in the optical communication system.