Device and method for reducing polarization dependent loss in an optical monitor device

A method for monitoring one or more optical signals in an optical communications network, comprising the steps of:

• receiving a beam of one or more optical signals;
• collimating the beam to produce a substantially collimated optical beam having a substantially uniform polarization state;
• modifying the collimated optical beam so that the polarization state of the modified beam spatially varies as a function of a sinusoid and that the polarization state of the modified beam is approximately equal to two orthogonal linear polarization states with no relative phase relationship when spatially averaged;
• and
• diffracting the modified beam as a function of wavelength so that the diffracted modified beam is incident on at least one detector element.

An apparatus for monitoring optical signals, comprising:

• an input for receiving an end portion of at least one fiber optic line;
• a lens assembly for collimating an optical beam appearing at the end portion of the at least one fiber optic line;
• means, in optical communication with the lens assembly, for modifying the optical beam so that a polarization state of the optical beam varies as a sinusoidal function along at least one direction;
• a diffraction device in optical communication with the means for modifying and having a pair of principal efficiency axes, the polarization state of the optical beam is approximately 45 degrees offset from a principal efficiency axis of the diffraction device;
• and
• an optical detector in optical communication with the diffraction device, for detecting light diffracted by the diffraction device.