Ericsson Ab

Steven Alleston

Nicholas John Doran

Paul Harper

Derek Nesset

Tim Ellingham

Liam Gleeson

Marc Francis Charles Stephens

Stuart Bidmead

Tony Walsh

Donald Govan

Anthony Walsh

Benoit Charbonnier

In an optical transmission system for transmission of data along an optical fiber link, a receiver for an optical supervisory channel is capable of detecting data at a lower rate at which a Raman pump is enabled, and at a higher rate which is commenced when the higher power of a Raman amplified signal has been received.

Optical transmission system

A method of reducing Raman tilt in a transmission apparatus capable of transmitting a plurality of signals, occupying contiguous channels in a transmission band, through a length of optical transmission cable which exhibits the Raman effect of transferring energy from the shorter wavelength signals at one end of the transmission band towards the longer wavelength signals at the other end of the transmission band, including the transmission of half the maximum number of signals at twice the normal channel frequency spacing at a higher-than-normal level and the transmission signals in selected ones, fewer than all, of the available channels at the normal channel spacing at a normal power level. As new channels are added at the lower frequency channel spacing, the powers of both neighboring channels are reduced to the normal power level.

Signal transmission in an optical system

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.

Signal transmission apparatus and a method of signal transmission

An optical signal transmission apparatus for transmitting a plurality of data signals comprising a plurality of inputs for receiving a respective one of the data signals and delivering the respective data signal with a controlled phase and at a controlled data rate. A plurality of optical carrier signals having different wavelength is generated. Each of a plurality of first modulators is operative for modulating a respective one of the optical carriers with a respective data signal to provide a first-modulated optical carrier signal. An optical signal-routing device has a plurality of input ports, each port being for receiving a respective one of the first-modulated optical carrier signals and delivering it to the output port of the device. The apparatus further comprises further modulators for further modulating each of the first-modulated optical carrier signals in dependence upon a clock to provide a plurality of further-modulated optical carrier signals; and a feedback arrangement, including the optical signal-routing device, for feeding back a proportion of each of the further modulated optical carrier signals to a respective input for controlling the phase and rates at which the input delivers the data signal to the first modulator in dependence upon the further modulation to thereby synchronize each input data signal to the clock. The optical signal-routing device delivers each of the further-modulated signals applied to its output to a respective input along a path which is dependent upon the wavelength of the signal.

Optical signal transmission

A method and apparatus for transmitting a plurality of signals having different wavelengths through a length of optical cable which is caused to provide distributed gain by being subjected to Raman pumping at a plurality of pump wavelengths, the power levels of the pump signals being in a set ratio or ratios for providing, preferably, a flat gain profile over the range of wavelengths of the plurality of signals, the set power levels of the pump signals being determined from the measured effects of the pump signals on a probe signal and in relation to the wavelength separations among the probe signal, the pump signals and the plurality of signals having different wavelengths.

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Leamington Spa, United Kingdom

Steven Alleston