Semiconductor laser apparatus, semiconductor laser module, optical transmitter and wavelength division multiplexing communication system

A semiconductor laser module comprising:

• a semiconductor laser apparatus having a light-emitting portion including a light-emitting device for outputting a laser beam, a light-receiving element for receiving the laser beam outputted from said light-emitting device, a first temperature regulating portion coupled to said light-emitting portion, a wavelength monitoring portion comprising an optical system disposed between said light-emitting device and said light-receiving element, a second temperature regulating portion separated from said first temperature regulating portion and coupled to said wavelength monitoring portion, such that the temperature of said wavelength monitoring portion is controlled independently of said light-emitting portion, a control portion for controlling the wavelength of the laser beam outputted from said light-emitting device by controlling said first temperature regulating portion based on the wavelength of the laser beam detected by said wavelength monitoring portion and an optical isolator disposed on the optical path between said light-emitting device and said wavelength monitoring portion for preventing the light from returning from said wavelength monitoring portion back to said light-emitting device;
• a package configured to enclose at least said light-emitting portion and said first temperature regulating portion in said semiconductor laser apparatus;
• and
• an optical fiber mounted to said package and configured to receive and transmitting the laser beam outputted from said light-emitting device to the outside of said package.

A wavelength division multiplexing communication system comprising a plurality of optical transmitters for transmitting optical signals, a multiplexer for wavelength multiplexing multi-channel optical signals transmitted from said optical transmitters, a plurality of optical amplifiers connected to one another in a plurality of stages for amplifying and relaying the multiplexed optical signal from said multiplexer, a branching filter for wavelength separating the amplified optical signals from the optical amplifiers for the respective channels and a plurality of optical receivers for receiving the respective optical signals separated by the branching filter, each of said optical transmitters comprising a semiconductor laser module having a light-emitting portion including a light-emitting device for outputting a laser beam, a light-receiving element for receiving the laser beam outputted from said light-emitting device, a first temperature regulating portion for controlling the temperature of said light-emitting portion, a wavelength monitoring portion comprising an optical system disposed between said light-emitting device and said light-receiving element, a second temperature regulating portion for controlling the temperature of said wavelength monitoring portion, said second temperature regulating portion being separated from said first temperature regulating portion such that the temperature of said wavelength monitoring portion is controlled independently of said light-emitting portion, a control portion for controlling the wavelength of the laser beam outputted from said light-emitting device by controlling said first temperature regulating portion based on the wavelength of the laser beam detected by said wavelength monitoring portion and an optical isolator disposed on the optical path between said light-emitting device and said wavelength monitoring portion for preventing the light from returning from said wavelength monitoring portion back to said light-emitting device.