Abstract: Consistent with the present disclosure, a transmitter is provided in a hub node of a point-to-multi-point optical communication system. The transmitter supplies a plurality or group of optical subcarriers, each subgroup of the group of optical subcarriers in, one example, is associated with a respective leaf node. Since the leaf nodes may be located at different distances from the hub node, the modulation of each optical subcarrier subgroup is optimized for the distance and impairments associated with the optical path over which the subcarrier subgroup is transmitted to its designated leaf. Namely, probabilistic shaping is employed, in one example, to adjust the modulation so that a maximum spectral efficiency is supported for a given SNR associated with the hub-leaf link.

Abstract: A random noise generator for generating a plurality of random noise samples per clock cycle, the noise samples having a distribution. The random noise generator comprises at least a first comparator unit and a second comparator unit, the first comparator unit configured to generate a first plurality of samples representing a high-probability part of the distribution and the second comparator unit configured to generate a second plurality of samples representing a low-probability part of the distribution; and a random selection unit connected to at least the first comparator unit and the second comparator unit. The random selection unit is configured to receive the first plurality of samples generated by the first comparator unit and the second plurality of samples generated by the second comparator unit, to output a random selection of samples from the first plurality of samples and the second plurality of samples.

Abstract: A method for digital resampling in a digital communications receiver is described. The method comprises selecting whole samples of a received input signal in the time domain and implementing sub-sample digital interpolation in the frequency domain. This amounts to performing the time shift of the interpolation process in the frequency domain. The method may be performed in conjunction with the operation of a polarisation recovery filter. A digital communications receiver is also provided the receiver being arranged to perform frequency domain sub-sample interpolation on an input data signal.

Abstract: A method for digital resampling in a digital communications receiver is described. The method comprises selecting whole samples of a received input signal in the time domain and implementing sub-sample digital interpolation in the frequency domain. This amounts to performing the time shift of the interpolation process in the frequency domain. The method may be performed in conjunction with the operation of a polarisation recovery filter. A digital communications receiver is also provided the receiver being arranged to perform frequency domain sub-sample interpolation on an input data signal.

Abstract: A method for digital resampling in a digital communications receiver is described. The method comprises selecting whole samples of a received input signal in the time domain and implementing sub-sample digital interpolation in the frequency domain. This amounts to performing the time shift of the interpolation process in the frequency domain. The method may be performed in conjunction with the operation of a polarisation recovery filter. A digital communications receiver is also provided the receiver being arranged to perform frequency domain sub-sample interpolation on an input data signal.

Abstract: A random noise generator for generating a plurality of random noise samples per clock cycle, the noise samples having a distribution. The random noise generator comprises at least a first comparator unit and a second comparator unit, the first comparator unit configured to generate a first plurality of samples representing a high-probability part of the distribution and the second comparator unit configured to generate a second plurality of samples representing a low-probability part of the distribution; and a random selection unit connected to at least the first comparator unit and the second comparator unit. The random selection unit is configured to receive the first plurality of samples generated by the first comparator unit and the second plurality of samples generated by the second comparator unit, to output a random selection of samples from the first plurality of samples and the second plurality of samples.

Abstract: A method for digital resampling in a digital communications receiver is described. The method comprises selecting whole samples of a received input signal in the time domain and implementing sub-sample digital interpolation in the frequency domain. This amounts to performing the time shift of the interpolation process in the frequency domain. The method may be performed in conjunction with the operation of a polarisation recovery filter. A digital communications receiver is also provided the receiver being arranged to perform frequency domain sub-sample interpolation on an input data signal.

Abstract: One or more operational parameters associated with pluggable optical transceivers are estimated to mitigate impairments to an optical signal caused by imperfections in the optical transceivers. A monitoring algorithm within a receiver signal processor may further use the estimated operational parameters associated with the pluggable optical transceivers to determine whether the transceivers are performing correctly. If the monitoring algorithm determines that either the transmitting or receiving optical transceiver is not functioning correctly, it may generate an alarm signal to notify a system administrator about the damaged device.

Abstract: One or more operational parameters associated with pluggable optical transceivers are estimated to mitigate impairments to an optical signal caused by imperfections in the optical transceivers. A monitoring algorithm within a receiver signal processor may further use the estimated operational parameters associated with the pluggable optical transceivers to determine whether the transceivers are performing correctly. If the monitoring algorithm determines that either the transmitting or receiving optical transceiver is not functioning correctly, it may generate an alarm signal to notify a system administrator about the damaged device.

Abstract: One or more operational parameters associated with pluggable optical transceivers are estimated to mitigate impairments to an optical signal caused by imperfections in the optical transceivers. A monitoring algorithm within a receiver signal processor may further use the estimated operational parameters associated with the pluggable optical transceivers to determine whether the transceivers are performing correctly. If the monitoring algorithm determines that either the transmitting or receiving optical transceiver is not functioning correctly, it may generate an alarm signal to notify a system administrator about the damaged device.

Abstract: One or more operational parameters associated with pluggable optical transceivers are estimated to mitigate impairments to an optical signal caused by imperfections in the optical transceivers. A monitoring algorithm within a receiver signal processor may further use the estimated operational parameters associated with the pluggable optical transceivers to determine whether the transceivers are performing correctly. If the monitoring algorithm determines that either the transmitting or receiving optical transceiver is not functioning correctly, it may generate an alarm signal to notify a system administrator about the damaged device.

Abstract: One or more operational parameters associated with pluggable optical transceivers are estimated to mitigate impairments to an optical signal caused by imperfections in the optical transceivers. A monitoring algorithm within a receiver signal processor may further use the estimated operational parameters associated with the pluggable optical transceivers to determine whether the transceivers are performing correctly. If the monitoring algorithm determines that either the transmitting or receiving optical transceiver is not functioning correctly, it may generate an alarm signal to notify a system administrator about the damaged device.

Abstract: One or more operational parameters associated with pluggable optical transceivers are estimated to mitigate impairments to an optical signal caused by imperfections in the optical transceivers. A monitoring algorithm within a receiver signal processor may further use the estimated operational parameters associated with the pluggable optical transceivers to determine whether the transceivers are performing correctly. If the monitoring algorithm determines that either the transmitting or receiving optical transceiver is not functioning correctly, it may generate an alarm signal to notify a system administrator about the damaged device.

Abstract: Use in an optical communications system of multiple detectors to separately detect respective multiple spectral modes of a received optical signal. The invention also provides for corresponding multi-channel, dispersion-tolerant optical receivers. Embodiments are presented both for direct detection and for coherent detection of optical signals.

Abstract: Use in an optical communications system of multiple detectors to separately detect respective multiple spectral modes of a received optical signal. The invention also provides for corresponding multi-channel, dispersion-tolerant optical receivers. Embodiments are presented both for direct detection and for coherent detection of optical signals.

Abstract: In a first aspect, a Raman amplifier is pumped using pumps just above and below the fiber water peak. This enables lower power pumps to be used, as the high attenuation is avoided. In a second aspect, a first pump provides a signal having a first wavelength and a first power, and a second pump source provides a plurality of signals, each having a power lower than the first power and a wavelength in a range approximately one Stokes shift higher than the first wavelength. In this way, the second pump source signals are amplified by the Raman effect by the first pump source signal, and the amplified second pump source signals cause signal amplification. The amplified second pump source signals can then include wavelengths above and below the water peak.

Abstract: A Raman optical amplifier has a plurality of pump sources (14,16,18,20,22). The outputs from at least two pump sources are modulated so as to reduce the interaction between the pump source signals in the fiber. By reducing this interaction, the tilt in the effective noise figure is reduced. In one example, the modulation involves providing the pump signals (1423 nm, 1444 nm and 1464 nm, 1495 nm) at different times.

Abstract: A method of consolidating a body in any of initially powdered, sintered, fibrous, sponge, or other form capable of compaction, including the steps: providing a bed of flowable particles within a contained zone, the particulate including flowable and resiliently compressible carbonaceous particles; positioning the body in the bed, to be surrounded by the particles; effecting pressurization of the bed to cause pressure transmission via the particles to said body, thereby to compact the body into desired shape, increasing its density; the particles being heated to elevated temperature prior to compacting of the body into desired shape; and the heating of the particles being effected by passing electric current through same, with heat generated in the particles also to be transferred to the body.The electrically heated mass of particles may be fluidized; the particles may consist of graphite; and the body may consist of metal, ceramic, or synthetic resin.