To maintain control over optical output of an LD (Laser Diode) even in a state where it is difficult to detect temperature of the LD, in an optical transmitter.
A method of controlling temperature of an LD even when defect occurs in a first feedback loop for controlling the temperature of the LD normally, is disclosed. It is determined whether or not defect occurs in the first feedback loop for controlling the temperature of the LD 3 normally. When it is determined that the defect occurs there, controlling of optical output of the LD 3 using a second feedback loop for controlling the optical output of the LD 3 is stopped and a drive current of the current value just before the determination of the defect is supplied to the LD 3. During supply of the drive current of this current value to the LD 3, an ATC controller 9 outputs control signal for controlling temperatures of a TEC 5, a photodetection element 17 and the LD 3 according to input from the photodetection element 17, and a TEC driver 13 outputs drive signal for driving the TEC 5 according to the control signal. The ATC controller 9 and the TEC driver 13 are also used in this method.
IRIE TAKESHI
ITO TOMOKI
OZAKI KAZUHISA
TOGASAKI MASAJI
Shiro Terasaki
Yoshiki Kuroki
Ichira Kondo