Patent ID: 6075647
Filing Date: 2000-06-13
Classification: G01J

Abstract:
An optical spectrum analyzer selective to an applied optical signal, comprising:an interference filter having an axis of rotation, at least one contour of substantially equal optical thickness coplanar with the axis of rotation, and a center wavelength that varies according to the angle of rotation of the interference filter about the axis of rotation; anda polarization modifier including a polarizing beam splitter receiving the applied optical signal, directing a first polarization state of the applied optical signal into a first optical beam and directing a second polarization state of the applied optical signal into a second optical beam, the second polarization state orthogonal to the first polarization state,a first nonreciprocal polarization rotator receiving the first optical beam, maintaining the first polarization state of the first optical beam and directing the first optical beam through a first region of incidence on a predefined one of the at least one contour of substantially equal optical thickness of the interference filter,a retroreflector receiving the first optical beam from the first region of incidence and reflecting the first optical beam to a second region of incidence on the predefined one of the at least one contour of substantially equal optical thickness of the interference filter,a second nonreciprocal polarization rotator receiving the first optical beam from the second region of incidence in the first polarization state and rotating the polarization state of the first optical beam from the first polarization state to the second polarization state, anda reflector directing the first optical beam in the second polarization state to the output path, the reflector directing the second optical beam to the second nonreciprocal polarization rotator, which rotates the polarization state of the second optical beam from the second polarization state to the first polarization state and which directs the second optical beam through the second region of incidence, the retroreflector receiving the second optical beam from the second region of incidence and directing the second optical beam through the first region of incidence and to the first nonreciprocal polarization rotator, which maintains the polarization state of the second optical in the first polarization state and directs the second optical beam to the polarizing beam splitter which combines the second optical beam with the first optical beam at the output path.