Abstract: The system-level control of a repeatered optical communications system. In a repeatered optical communications system, two terminals are optically coupled via an optical communications span having one or more repeaters. One of the terminals may perform the control by monitoring quality metrics of optical signals received over the communication span. Based on this monitoring, certain adjustments are determined to be performed, and the repeater controllers of the respective optical repeaters are instructed to perform the adjustments. In some case, the optical repeater adjustments cannot be made without impacting the performance of the optical signals traveling in the opposite direction. In that case, the system-level control uses monitored quality metrics from both terminals to determine the adjustments to be made. The system level adjustment may be automated by software or the like thereby making optimization of the optical communications span easier.

Abstract: The system-level control of a repeatered optical communications system. In a repeatered optical communications system, two terminals are optically coupled via an optical communications span having one or more repeaters. One of the terminals may perform the control by monitoring quality metrics of optical signals received over the communication span. Based on this monitoring, certain adjustments are determined to be performed, and the repeater controllers of the respective optical repeaters are instructed to perform the adjustments. In some case, the optical repeater adjustments cannot be made without impacting the performance of the optical signals traveling in the opposite direction. In that case, the system-level control uses monitored quality metrics from both terminals to determine the adjustments to be made. The system level adjustment may be automated by software or the like thereby making optimization of the optical communications span easier.

Abstract: There is provided a method and apparatus for tuning an optical discriminator to the carrier frequency of an optical signal to allow superior reception of said signal. The carrier frequency of the signal is dithered during a test phase in order to provide information that allows a subsequent tuning phase to optimise the reception of the optical signal, as measured by a signal quality metric. The tuning phase may comprise adjustment of one or both of the carrier frequency and the optical discriminator.

Abstract: A polarization mode dispersion compensator that includes two stages, one for reducing or eliminating first order polarization mode dispersion of an optical signal, and second stage for reducing or eliminating higher order polarization mode dispersion of the optical signal. In each stage, the polarization is adjusted so as to reduce polarization mode dispersion. Based on the power levels of various polarization states generated at the second polarization controller, the optical signal to noise ratio may be estimated. Furthermore, based on the amount of adjustment used to control the polarization controllers and the differential group delay, the polarization mode dispersion may be estimated.

Abstract: A system and method are provided for controlling the pre-emphasis applied to an optical signal, in which the output level of individual transmitters is controlled in order to reach a pre-defined desired value of a quality metric. Transmitters are able to adjust their output power without external control in such a way as to optimise the power distribution across the system.

Abstract: A polarization mode dispersion compensator that includes two stages, one for reducing or eliminating first order polarization mode dispersion of an optical signal, and second stage for reducing or eliminating higher order polarization mode dispersion of the optical signal. In each stage, the polarization is adjusted so as to reduce polarization mode dispersion. Based on the power levels of various polarization states generated at the second polarization controller, the optical signal to noise ratio may be estimated. Furthermore, based on the amount of adjustment used to control the polarization controllers and the differential group delay, the polarization mode dispersion may be estimated.

Abstract: A system and method are provided for controlling the pre-emphasis applied to an optical signal, in which the output level of individual transmitters is controlled in order to reach a pre-defined desired value of a quality metric. Transmitters are able to adjust their output power without external control in such a way as to optimise the power distribution across the system.

Abstract: There is provided a method and apparatus for tuning an optical discriminator to the carrier frequency of an optical signal to allow superior reception of said signal. The carrier frequency of the signal is dithered during a test phase in order to provide information that allows a subsequent tuning phase to optimise the reception of the optical signal, as measured by a signal quality metric. The tuning phase may comprise adjustment of one or both of the carrier frequency and the optical discriminator.

Abstract: There is provided a method and system for obtaining an enhanced estimate of bit error rate performance. A receiver module counts a predetermined number of bit errors and concurrently measures the time taken for the predetermined number of bit errors to occur. In this way an estimate of the bit error rate (BER) is obtained which has the same statistical weight regardless of the numerical value of the BER. The estimate of BER can subsequently be used to optimise the parameters of the system such that the true value of BER is at a minimum.

Abstract: A wavelength division multiplexing transmission system, the system comprising: a plurality of channels at different wavelengths, each channel comprising a transmitter, a receiver, and one or more amplifiers, the system further comprising an encoder for encoding data with a coding, and; a decoder for decoding transmitted data; prioritising means for prioritising the data on each channel; monitoring means for monitoring directly or indirectly, raw (uncorrected) bit errors on each channel; power adjusting means for, varying the power on a channel in response to tho bit error rate.