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The present invention provides an apparatus for determining a wavelength of an optical signal by determining a coarse wavelength response and a fine wavelength response. The coarse wavelength response is achieved by utilizing an optical filter. A suitable detector detects the wavelength-dependent re

The present invention provides an apparatus for determining a wavelength of an optical signal by determining a coarse wavelength response and a fine wavelength response. The coarse wavelength response is achieved by utilizing an optical filter. A suitable detector detects the wavelength-dependent response and conveys the determined coarse wavelength response to the processing logic. The fine wavelength response is achieved by utilizing an interferometer that is capable of generating an interference pattern. Two detectors are disposed in the interference pattern at a quadrature separation from each other and detect the intensity responses at their respective locations. The intensity responses are conveyed to a unit that determines the fine wavelength response. Finally, the processing logic determines the wavelength utilizing the determined coarse wavelength response and the determined fine wavelength response.

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1. 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 detection means for determining a coarse wavelength response from said wavelength-dependent response; c) an int

1. 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 detection means 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; e) a unit for determining a fine wavelength response from said two intensity signals; and f) a processing logic for determining said wavelength from said coarse wavelength response and said fine wavelength response. 2. The apparatus of claim 1, wherein said interferometer comprises an etalon.3. The apparatus of claim 2, wherein said etalon is a wedge etalon.4. The apparatus of claim 1, further comprising an aperture for substantially preventing high-order reflections from propagating from said interferometer to said two photodetectors.5. The apparatus of claim 1, wherein said wavelength-dependent response is linear.6. The apparatus of claim 1, wherein said optical filter is a transmission filter.7. The apparatus of claim 6, wherein said transmission filter comprises a coating.8. The apparatus of claim 1, wherein said optical filter is a reflection filter.9. The apparatus of claim 8, wherein said reflection filter comprises a coating.10. The apparatus of claim 9, wherein said interferometer is an etalon and said coating is deposited on a back surface of said etalon.11. The apparatus of claim 9, wherein said wavelength-dependent response is linear.12. 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. 13. The apparatus of claim 12, wherein said interferometer comprises a wedge etalon.14. The apparatus of claim 12, further comprising an aperture for substantially preventing high-order reflections from propagating from said interferometer to said two photodetectors.15. The apparatus of claim 12, further comprising a power detector for detecting a reference power Pref of said optical signal.16. The apparatus of claim 12, wherein said optical filter comprises a wavelength filter in which said wavelength-dependent response is linear.17. The apparatus of claim 12, wherein said optical filter is a transmission filter.18. The apparatus of claim 12, wherein said optical filter is a reflection filter.19. The apparatus of claim 12, further comprising a slit pair disposed proximate to said interferometer for defining two sampling points in said interference pattern, said two photodetectors being positioned at said two sampling points.20. The apparatus of claim 12, wherein said interferometer generates two beams such that the axes of said two beams have a point of intersection, said two photodetectors being placed such that a detection plane of said two photodetectors contains said point of intersection.21. 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. 22. The apparatus of claim 21, wherein a sum power of said two intensity signals comprises a coarse wavelength response.23. The apparatus of claim 21, wherein said coating has a linear wavelength-dependent response to said optical signal.24. The apparatus of claim 23, wherein said coating is deposited on said back surface.25. The apparatus of claim 24, wherein said linear wavelength-dependent response comprises transmission or reflection.26. The apparatus of claim 25, wherein said wavelength-dependent response comprises transmission and said apparatus further comprises a photodetector for measuring said transmission.27. The apparatus of claim 21, further comprising an aperture for substantially preventing high-order reflections from propagating from said wedge etalon to said two photodetectors.28. The apparatus of claim 21, further comprising a power detector for detecting a reference power Pref of said optical signal.29. The apparatus of claim 21, further comprising a slit pair disposed proximate to said wedge etalon for defining two sampling points in said interference pattern, said two photodetectors being positioned at said two sampling points.30. The apparatus of claim 21, wherein said wedge etalon generates two beams such that the axes of said two beams have a point of intersection, said two photodetectors being placed such that a detection plane of said two photodetectors contains said point of intersection.31. 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. 32. The method of claim 31, wherein said coarse wavelength response is determined by a sum power measurement from said two photodetectors.33. The method of claim 31, further comprising integrating said optical filter with said interferometer.34. The method of claim 31, further comprising substantially eliminating high-order reflections from propagating from said interferometer to said two photodetectors.35. 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. 36. The method of claim 35, wherein said interferometer is a wedge etalon having a front surface and a back surface, and said interference pattern in generated by introducing said optical signal into said wedge etalon through said front surface.37. The method of claim 35, further comprising substantially eliminating high-order reflections from propagating from said interferometer to said two photodetectors.38. The method of claim 35, further comprising measuring a reference power Pref of said optical signal and normalizing said two intensity signals with the aid of said reference power.39. The method of claim 35, wherein said optical filter is selected to have a linear wavelength response.40. The method of claim 35, wherein said wavelength-dependent response comprises transmission.41. The method of claim 35, wherein said wavelength-dependent response comprises reflection.42. The method of claim 35, further comprising imaging said interference pattern through a slit pair.43. 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. 44. The method of claim 43, wherein said coating is selected to exhibit a linear wavelength-response.45. The method of claim 44, wherein said coating is deposited on said back surface.46. The method of claim 43, further comprising substantially eliminating high-order reflections from propagating from said interferometer to said two photodetectors by passing said interference pattern through an aperture.47. The method of claim 43, further comprising measuring a reference power Pref of said optical signal and normalizing said two intensity signals with the aid of said reference power.48. The method of claim 43, further comprising imaging said interference pattern through a slit pair.