Optical power monitor device, optical amplifier, and optical transmitter

An optical transmitter comprising:

• a light source for outputting first and second beams;
• a beam splitter for receiving said first beam and dividing said first beam into first and second branch beams;
• an optical amplifying medium for receiving said second branch beam;
• means for pumping said optical amplifying medium so that said optical amplifying medium has a gain band including a wavelength of said second branch beam;
• a first photodetector for receiving said first branch beam and outputting a first signal having a level corresponding to a power of said first branch beam;
• a second photodetector for receiving said second beam and outputting a second signal having a level corresponding to a power of said second beam;
• a first subtracter for receiving said first and second signals and outputting a first error signal corresponding to a difference between said first and second signals;
• and
• a second subtracter for receiving said first signal and said first error signal and outputting a second error signal corresponding to a difference between said first signal and said first error signal.

An optical power monitor device for an optical amplifier having an optical path including an optical amplifying medium, comprising:

• a photodetector operatively connected to said optical path, for outputting an electrical signal having a level corresponding to an optical power in said optical path;
• a peak detecting circuit for receiving said electrical signal and outputting a first signal providing a first peak level corresponding to a maximum level of said electrical signal and a second signal providing a second peak level lower than said first peak level;
• and
• a subtracter for receiving said first and second signals and outputting an error signal corresponding to a difference between said first and second signals.

An optical amplifier comprising:

• an optical amplifying medium provided in an optical path between an input port and an output port;
• means for pumping said optical amplifying medium so that said optical amplifying medium has a gain band;
• a beam splitter for dividing an optical beam propagating along said optical path into first and second branch beams;
• a photodetector for receiving said first branch beam and outputting an electrical signal having a level corresponding to a power of said first branch beam;
• a peak detecting circuit for receiving said electrical signal and outputting a first signal providing a first peak level corresponding to a maximum level of said electrical signal and a second signal providing a second peak level lower than said first peak level;
• and
• a subtracter for receiving said first and second signals and outputting an error signal corresponding to a difference between said first and second signals.