An integrated optical circuit for an optical neural network, the optical circuit being configured: to process a phase-encoded optical input signal (S in ); and to provide a phase-encoded optical output signal (S out ) depending on the phase-encoded optical input signal (S in ), the phase-encoded optical output signal emulating a synapse functionality with respect to the phase-encoded optical input signal (S in ); the integrated optical circuit comprising: a reference waveguide configured to carry an optical reference signal (S r ); an input waveguide configured to receive the phase-encoded optical input signal (S in ), wherein a phase difference (φ) between the optical reference signal (S r ) and the optical input signal (S in ) represents the phase of the phase encoded optical input signal (S in ); an output waveguide ; an optical interferometer configured to convert the optical reference signal (S r ) and the optical input signal (S in ) into an interference signal (I) by superimposition; a tunable attenuator configured to perform a weighting of the interference signal (I) into a weighted interference signal (IW); and a phase-shifting device configured to convert the weighted interference signal (IW) into the phase-encoded optical output signal (S out ) by inducing a phase shift in the optical reference signal (S r ) in dependence on the weighted interference signal (IW). the optical circuit being configured: to process a phase-encoded optical input signal (S in ); and to provide a phase-encoded optical output signal (S out ) depending on the phase-encoded optical input signal (S in ), the phase-encoded optical output signal emulating a synapse functionality with respect to the phase-encoded optical input signal (S in ); to process a phase-encoded optical input signal (S in ); and to provide a phase-encoded optical output signal (S out ) depending on the phase-encoded optical input signal (S in ), the phase-encoded optical output signal emulating a synapse functionality with respect to the phase-encoded optical input signal (S in ); the integrated optical circuit comprising: a reference waveguide configured to carry an optical reference signal (S r ); an input waveguide configured to receive the phase-encoded optical input signal (S in ), wherein a phase difference (φ) between the optical reference signal (S r ) and the optical input signal (S in ) represents the phase of the phase encoded optical input signal (S in ); an output waveguide ; an optical interferometer configured to convert the optical reference signal (S r ) and the optical input signal (S in ) into an interference signal (I) by superimposition; a tunable attenuator configured to perform a weighting of the interference signal (I) into a weighted interference signal (IW); and a phase-shifting device configured to convert the weighted interference signal (IW) into the phase-encoded optical output signal (S out ) by inducing a phase shift in the optical reference signal (S r ) in dependence on the weighted interference signal (IW). a reference waveguide configured to carry an optical reference signal (S r ); an input waveguide configured to receive the phase-encoded optical input signal (S in ), wherein a phase difference (φ) between the optical reference signal (S r ) and the optical input signal (S in ) represents the phase of the phase encoded optical input signal (S in ); an output waveguide ; an optical interferometer configured to convert the optical reference signal (S r ) and the optical input signal (S in ) into an interference signal (I) by superimposition; a tunable attenuator configured to perform a weighting of the interference signal (I) into a weighted interference signal (IW); and a phase-shifting device configured to convert the weighted interference signal (IW) into the phase-encoded optical output signal (S out ) by inducing a phase shift in the optical reference signal (S r ) in dependence on the weighted interference signal (IW). <EOS>