Apparatus and method for determining wavelength from coarse and fine measurements

An apparatus for determining a wavelength of an optical signal, said apparatus comprising:

• a) an optical filter for providing a wavelength-dependent response to said optical signal;
• b) a detector for determining a coarse wavelength response from said wavelength-dependent response;
• c) an interferometer for receiving said optical signal and generating therefrom an interference pattern;
• d) two photodetectors placed in said interference pattern at a quadrature separation from each other for generating two corresponding intensity signals;
• and
• e) a processing logic for determining said wavelength from said coarse wavelength response and said two intensity signals.

An apparatus for determining a wavelength of an optical signal, said apparatus comprising:

• a) a wedge etalon having a front surface, a back surface and a coating, said wedge etalon receiving said optical signal through said front surface and generating therefrom an interference pattern;
• b) two photodetectors placed in said interference pattern at a quadrature separation from each other for generating two corresponding intensity signals;
• and
• c) a processing logic for determining said wavelength from said two intensity signals.

A method for determining a wavelength of an optical signal, said method comprising:

• a) providing an optical filter having a wavelength-dependent response to said optical signal;
• b) passing said optical signal through said optical filter;
• c) determining a coarse wavelength response from said wavelength-dependent response;
• d) passing said optical signal through an interferometer for generating an interference pattern;
• e) placing two photodetectors in said interference pattern at a quadrature separation from each other for generating two corresponding intensity signals;
• f) determining a fine wavelength response from said two intensity signals;
• and
• g) determining said wavelength from said coarse wavelength response and said fine wavelength response.

A method for determining a wavelength of an optical signal, said method comprising:

• a) passing said optical signal through an optical filter having a wavelength-dependent response to said optical signal;
• b) determining a coarse wavelength response from said wavelength-dependent response;
• c) passing said optical signal through an interferometer to generate an interference pattern;
• d) sampling said fringe pattern at two sampling points at a quadrature separation from each other to generate two corresponding intensity signals;
• and
• e) determining said wavelength from said coarse wavelength response and said two intensity signals.

A method for determining a wavelength of an optical signal, said method comprising:

• a) passing said optical signal through a wedge etalon having a front surface, a back surface and a coating to generate an interference pattern;
• b) sampling said fringe pattern at two sampling points at a quadrature separation from each other to generate two corresponding intensity signals;
• and
• c) determining said wavelength from said intensity signals.