| 摘要 |
An equaliser (60) processes, in the electrical domain, a signal obtained from a path of an optical transmission system. The equaliser comprises N cascaded stages (where N≧1). At least one of the stages comprises a cascade of a linear equalisation element (61) and a non-linear equalisation element (62). The equaliser (60) is able to compensate for both linear impairments, such as dispersion, and non-linear impairments. The cascaded linear and non-linear elements can simulate the effect of signal propagation through a fibre which has the opposite propagation parameters (e.g. attenuation, dispersion, non-linearity) to those of the propagation path experienced by a signal in the transmission system. The non-linear equalisation element (62) can be a non-linear phase rotator which rotates phase of an input signal proportional to the squared modulus of the input signal amplitude. The linear equalisation element (61) can comprise a digital filter, such as an Infinite Impulse Response (HR) filter or a Finite Impulse Response (FIR) filter.
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