Patent ID: 6819429
Filing Date: 2004-11-16
Classification: G02B

Abstract:
An optical spectrum analyzer apparatus comprising:an inherently polarization-sensitive tunable filter element; polarization-maintaining optical means for defining paths whereby a light beam is directed to traverse the polarization-sensitive tunable filter element a predetermined number of times; a polarization control module for receiving input light for analysis, decomposing the received input light into its ordinary and extraordinary components to produce fist and second light beams having respective mutually orthogonal liner states of polarization, and applying the first and second light beams to the tunable filter element by way of the optical means with their states of polarization parallel to each other and to one of the principal axes of the tunable filter element, means for adjusting the tunable filter element to select different wavelengths of the input light; and means for detecting the first and second light beams leaving the tunable filter element without first recombining them optically and detecting energy at each of said different wavelengths, wherein the polarization control module comprises means for rotating the state of polarization of at least one of the first and second light beams relative to the state of polarization of the other of the first and second light beams before application to the tunable filter elements, said rotating means comprising at least one polarization-maintaining fiber.