Abstract: A signal recovery system for a phase modulated signal having a signal spectrum, wherein the phase modulated signal is passed along a communications system (1) having at least one filter (3) so as to define the frequency channel of the communication system. Losses result from the passage of the signal through the at least one filter (3) defining the transmission channel. The signal recovery system recovers at least some of the losses by introducing a relative frequency offset between the signal spectrum and the transmission spectrum of the at least one filter (3) in the communications system.

Abstract: An apparatus and method of transmitting a plurality of polarized signals having different wavelengths through a length of signal transmission cable which changes the polarization of the signals in correspondence with their amplitudes and wavelengths. A dynamic filter capable of differential adjustment of the amplitudes of the signals and a polarizing element are provided in series with the length of signal transmission cable and the amplitudes of the different wavelength signals are so adjusted that the polarization states of the signals move towards alignment with the low-loss axis of the polarizing element. An advantage provided by the apparatus and method is that the high-amplitude signals are aligned with the low-loss axis of the polarizing element while low-amplitude noise is aligned with the high-loss axis of the polarizing element, resulting in an improvement in signal-to-noise ratio.

Abstract: An apparatus and method of transmitting a plurality of polarized signals having different wavelengths through a length of signal transmission cable which changes the polarization of the signals in correspondence with their amplitudes and wavelengths. A dynamic filter capable of differential adjustment of the amplitudes of the signals and a polarizing element are provided in series with the length of signal transmission cable and the amplitudes of the different wavelength signals are so adjusted that the polarization states of the signals move towards alignment with the low-loss axis of the polarizing element. An advantage provided by the apparatus and method is that the high-amplitude signals are aligned with the low-loss axis of the polarizing element while low-amplitude noise is aligned with the high-loss axis of the polarizing element, resulting in an improvement in signal-to-noise ratio.