Equalization, pulse shaping and regeneration of optical signals

An optical transversal filter for processing an optical signal having an intensity which is time varying in amplitude to define an optical signal waveform, the filter comprising;

• a plurality of optical tap waveguides connected to receive the optical signal and comprising respective delay means operable to provide respective different delay periods whereby each optical tap waveguide is operable to output a respective tap signal having a tap signal waveform representative of the optical signal waveform subjected to the respective delay period;
• a modulating means operable to receive an optical input signal and to output a Modulated output signal having an output waveform;
• level control means operable to control the amplitude range of the tap signals to be sufficiently small for the modulation response of the modulating means to be approximately linear;
• and
• means for controlling the modulating means in response to the input of the tap signals such that the output waveform is modulated by the modulating means in dependence upon a substantially linear combination of the amplitudes of the tap signal waveforms.

A method of processing an optical signal having an intensity which is time varying in amplitude to define an optical signal waveform, the method comprising the steps of:

• forming a plurality of optical tap signals from the optical signal such that the tap signals define respective tap signal waveforms representative of the optical signal waveform subjected to different respective delay periods;
• inputting the tap signals as controlling signals to a modulating means;
• inputting an optical input signal to the modulating means to be modulated thereby;
• and controlling the modulating means in response to the input of the tap signals such that the modulating means provides modulation of the input signal to provide an optical output signal defining an output waveform modulated in dependence upon a combination of the amplitudes of the tap signal waveforms;
• wherein the optical signal is pulsed to define a bit period, wherein at least one of the tap signals has a respective delay period substantially equal to one bit period;
• and
• wherein the at least one optical tap is processed by an optical logic element such that the optical tap waveform modulates between two levels representative of binary one and zero corresponding to respective binary valuer of the optical signal.

An optical transversal filter for processing an optical signal having an intensity which is time varying in amplitude to define an optical signal waveform, the filter comprising;

• a plurality of optical tap waveguides connected to receive the optical signal and comprising respective delay means operable to provide respective different delay periods whereby each optical tap waveguide is operable to output a respective tap signal having a tap signal waveform representative of the optical signal waveform subjected to the respective delay period;
• a modulating means operable to receive an optical input signal and to output a modulated output signal having an output waveform;
• and
• means for controlling the modulating means in response to the input of the tap signals such that the output waveform is modulated by the modulating means in dependence upon a combination of the amplitudes of the tap signal waveforms;
• wherein the optical signal is pulsed to define a bit period, and wherein at least one of the delay means is operable to provide a delay period substantially equal to one bit period;
• and
• wherein at least one of the optical tap waveguides comprises an optical logic element operable to modulate the optical tap waveform between two levels representative of binary 1 and 0 corresponding to respective binary values of the optical signal.