A receiver, configured for receiving optical signals via an optical transmission channel, comprising a control unit configured to determine an amplitude and a phase of a received optical signal, wherein the control unit is configured to a) determine an estimated amplitude of a sent optical signal and an estimated phase of the sent optical signal based on a measured amplitude of the received optical signal, a predetermined phase of the received optical signal, and an inverse transmission function of the optical transmission channel, wherein the predetermined phase can have any default value; b) determine an estimated amplitude of the received optical signal and an estimated phase of the received optical signal based on the estimated amplitude of the sent optical signal, the estimated phase of the sent optical signal, and a transmission function of the optical transmission channel; c) replace the estimated amplitude of the received optical signal with a first amplitude value which is based on the measured amplitude of the received optical signal and to determine the estimated amplitude of the sent optical signal and the estimated phase of the sent optical signal based on the first amplitude value, a first phase value which is based on the estimated phase of the received optical signal, and the inverse transmission function of the optical transmission channel; and d) determine an estimated amplitude of the received optical signal and an estimated phase of the received optical signal based on the estimated amplitude of the sent optical signal, an assumed phase of the sent optical signal, and the transmission function of the optical transmission channel, wherein the assumed phase is an assumption based on known properties of the sender. a) determine an estimated amplitude of a sent optical signal and an estimated phase of the sent optical signal based on a measured amplitude of the received optical signal, a predetermined phase of the received optical signal, and an inverse transmission function of the optical transmission channel, wherein the predetermined phase can have any default value; b) determine an estimated amplitude of the received optical signal and an estimated phase of the received optical signal based on the estimated amplitude of the sent optical signal, the estimated phase of the sent optical signal, and a transmission function of the optical transmission channel; c) replace the estimated amplitude of the received optical signal with a first amplitude value which is based on the measured amplitude of the received optical signal and to determine the estimated amplitude of the sent optical signal and the estimated phase of the sent optical signal based on the first amplitude value, a first phase value which is based on the estimated phase of the received optical signal, and the inverse transmission function of the optical transmission channel; and d) determine an estimated amplitude of the received optical signal and an estimated phase of the received optical signal based on the estimated amplitude of the sent optical signal, an assumed phase of the sent optical signal, and the transmission function of the optical transmission channel, wherein the assumed phase is an assumption based on known properties of the sender.