Abstract: The present invention provides a method and apparatus for compensating for polarization mode dispersion in an optical transmission system without perturbing the laser source. The present invention compensates for PMD by transferring a sufficient fraction of the light signal in an optical transmission system substantially into a single PSP of the system. As a result, each light pulse in a data stream is not substantially mixed with temporally adjacent light pulses or bit periods.

Abstract: An optical system and a method for separating overlapping spectra from a diffraction grating and an imaging spectrometer with increased free spectral range are disclosed. The light from a diffraction grating consists of multiple spectra overlapping each other and displaced along a spectral axis. The invention directs the light from the grating to a refractive element such, as a prism. The prism further disperses the light along the same spectral axis. The individual spectra are sufficiently displaced such that they no longer interfere with each other.

Abstract: An optical dispersion sensor for sensing optical dispersion introduced by the atmosphere in near real-time and an optical system using the dispersion sensor to compensate for atmospheric dispersion are described. The input signal to the dispersion sensor is the image of the scene being viewed by a scanning optical system. The image of the scene is passed through an aperture near the image plane of the optical system and then onto at least two individual light detecting systems. One of the detecting systems is adapted to detect light of a first wavelength band. The other detecting system detects light of a second wavelength band. The sensor computes the relative time delay between the signals derived from the two detecting systems. The time delay indicates the spectral dispersion introduced by the atmosphere.