Optical power monitor and optical amplifier having the optical power monitor

An optical amplifier for an optical signal having a signal spectrum superimposed on a noise spectrum, comprising:

• an optical amplifying medium provided on a main optical path;
• first means for pumping said optical amplifying medium so that said optical amplifying medium has a gain band including a wavelength of said optical signal;
• second means operatively connected to said main optical path for extracting said optical signal from said main optical path;
• and
• an optical power monitor for said optical signal extracted;
• said optical power monitor comprising:
• an optical coupler for branching said optical signal into first and second beams;
• a first optical band-pass filter having a first pass band including said signal spectrum, said first beam being supplied to said first optical band-pass filter;
• a second optical band-pass filter having a second pass band including said signal spectrum and narrower than said first pass band, said second beam being supplied to said second optical band-pass filter;
• a first photodetector for receiving said first beam passed through said first optical band-pass filter and outputting a first electrical signal having a level corresponding to an average power of said first beam;
• a second photodetector for receiving said second beam passed through said second optical band-pass filter and outputting a second electrical signal having a level corresponding to an average power of said second beam;
• and
• an operating unit operatively connected to said first and second photodetectors for calculating a power of said optical signal according to said first and second electrical signals.

An optical power monitor for an optical signal having a signal spectrum superimposed on a noise spectrum, said signal spectrum being given by a main signal, comprising:

• a photodetector for receiving said optical signal and outputting an electrical signal having a level which changes according to said main signal;
• a low-pass filter operatively connected to said photodetector for passing a DC component of said electrical signal;
• and
• an operational amplifier operatively connected to said photodetector and said low-pass filter, said operational amplifier being supplied with said electrical signal and said DC component and outputting an error signal corresponding to a difference between said electrical signal and said DC component.

An optical amplifier for an optical signal having a signal spectrum superimposed on a noise spectrum, said signal spectrum being given by a main signal, comprising:

• an optical amplifying medium provided on a main optical path;
• first means for pumping said optical amplifying medium so that said optical amplifying medium has a gain band including a wavelength of said optical signal;
• second means operatively connected to said main optical path for extracting said optical signal from said main optical path;
• and
• an optical power monitor for said optical signal extracted;
• said optical power monitor comprising:
• a photodetector for receiving said optical signal and outputting an electrical signal having a level which changes according to said main signal;
• a low-pass filter operatively connected to said photodetector for passing a DC component of said electrical signal;
• and
• an operational amplifier operatively connected to said photodetector and said low-pass filter, said operational amplifier being supplied with said electrical signal and said DC component and outputting an error signal corresponding to a difference between said electrical signal and said DC component.

An optical power monitor for an optical signal having a signal spectrum superimposed on a noise spectrum, comprising:

• a first optical band-pass filter filtering a portion of the optical signal, the first optical band-pass filter having a pass band which includes the signal spectrum;
• a second optical band-pass filter filtering a different portion of the optical signal than the first optical band-pass filter, the second optical band-pass filter having a pass band which includes the signal spectrum and is narrower than the pass band of the first optical band-pass filter;
• and
• a power level determining unit determining a power of the optical signal in accordance with power levels of said filtered portions.

An optical power monitor for an optical signal having a signal spectrum superimposed on a noise spectrum, comprising:

• an optical coupler branching the optical signal into first and second light;
• a first optical band-pass filter filtering the first light, the first optical band-pass filter having a pass band which includes the signal spectrum;
• a second optical band-pass filter filtering the second light, the second optical band-pass filter having a pass band which includes the signal spectrum and is narrower than the pass band of the first optical band-pass filter;
• and
• an operating unit determining a power of the optical signal in accordance with a power level of the filtered first light and a power level of the filtered second light.

An optical power monitor for an optical signal having a signal spectrum determined by a main signal, comprising:

• a photodetector receiving the optical signal and producing a corresponding electrical signal having a level which changes in accordance with the main signal;
• a low-pass filter passing a DC component of the electrical signal;
• and
• an error signal unit producing an error signal corresponding to a difference between the electrical signal produced by the photodetector and the DC component passed by the low-pass filter.