US Patent 8345238 Measuring optical spectral property of light based on polarization analysis

A device for measuring spectrum of light includes a differential group delay (DGD) device positioned to receive light under measurement and to produce output light with a DGD value representing a difference in the group delay between two orthogonal optical polarizations of the light under measurement. An optical detector is positioned to receive the output light from the DGD device to measure a state and a degree of polarization of the output light. A processing device receives and processes measurements of the state and the degree of polarization from the optical detector. A probe light source produces probe light. An optical sensor receives the probe light and interacts with the probe light at a resonance wavelength of the optical sensor. A processing unit processes the optical spectrum of the returned probe light to extract information on a parameter to change the resonance wavelength.