Convolutions with optical finite impulse response filters

An apparatus for processing data, wherein the apparatus comprises:

• an optical finite impulse response (FIR) filter comprising several delay stages having weights set in accordance with parameters of a transformation to be applied by the optical FIR filter, the delay stages configured to impose a delay matched to a given input data period corresponding to a given input sample rate, wherein the optical FIR filter is a lattice filter, and the lattice filter is in two-port lattice form, the delay stages being four-terminal lattice filter stages that are optically connected in series, the four-terminal lattice filter stages comprising two waveguides and two phase shifters, the two phase shifters formed at respective portions of the two waveguides;
• a transmitter connected to an optical input of the optical FIR filter and configured to couple an optical signal into the optical FIR filter, wherein, in operation, the optical signal carries a data stream of input samples encoded at the given input sample rate, the data stream representing data to be processed;
• and
• a receiver connected to an optical output of the optical FIR filter and configured to collect output samples in an output data stream carried by an output optical signal obtained in output of the optical FIR filter to obtain a set of the output samples that are representative of the transformation.