Receiving apparatus and method for electronic noise compensation in phase modulated optical transmission

A receiving apparatus for processing a differential phase shift keying signal carrying a plurality of symbols, comprising

• an input unit for receiving electrical signals Re(u(n), Im(u(n), |y(n)|2 derived from an optical signal after self-homodyne reception;
• a calculation unit for calculating a current value of a decision variable x(n) indicative of a differential phase shift in the optical signal between a currently received symbol and a previously received symbol as a function of at least one of the electrical signals representing the optical signal power of the optical signal for the currently received symbol |y(n)|2 and at least one previous value of the decision variable x(n−1), x(n−2) to correct for phase noise;
• a decision unit for determining the differential phase shift from the current value of the decision variable x(n) obtained from the calculation unit to obtain the currently received symbol;
• an electro-optical arrangement for converting the optical signal into the electrical signals comprising at least one interferometer, wherein the at least one interferometer is a free running two-path interferometer coupled to a 3×3 optical coupler;
• and
• an electronic phase converter for converting three signals output from the 3×3 coupler two electrical signals to be input in said input unit.