A receiver, comprising: a signal acquiring unit, configured to receive a dual-polarization signal and a local oscillation, and separately perform polarization beam splitting processing on the dual-polarization signal and the local oscillation, to obtain signals of the dual-polarization signal in both X and Y polarization directions and signals of the local oscillation in both X and Y polarization directions; a signal diversity unit, connected to the signal acquiring unit and configured to perform coupling processing on the signal of the dual-polarization signal in the X polarization direction and the signal of the local oscillation in the X polarization direction, to obtain coupled signals with different phase shifts in the X polarization direction; and further configured to perform coupling processing on the signal of the dual-polarization signal in the Y polarization direction and the signal of the local oscillation in the Y polarization direction, to obtain coupled signals with different phase shifts in the Y polarization direction; a signal combination unit, connected to the signal diversity unit and configured to perform optical signal combination on a group of one coupled signal in the X polarization direction and one coupled signal in the Y polarization direction, to obtain a combined signal; and convert the combined signal to an electrical signal; and a digital-signal acquiring unit, connected to the signal combination unit and configured to receive the electrical signal output by the signal combination unit, and generate a digital signal of an electrical signal of the dual-polarization signal in the X polarization direction and a digital signal of an electrical signal of the dual-polarization signal in the Y polarization direction according to the received electrical signal. a signal acquiring unit, configured to receive a dual-polarization signal and a local oscillation, and separately perform polarization beam splitting processing on the dual-polarization signal and the local oscillation, to obtain signals of the dual-polarization signal in both X and Y polarization directions and signals of the local oscillation in both X and Y polarization directions; a signal diversity unit, connected to the signal acquiring unit and configured to perform coupling processing on the signal of the dual-polarization signal in the X polarization direction and the signal of the local oscillation in the X polarization direction, to obtain coupled signals with different phase shifts in the X polarization direction; and further configured to perform coupling processing on the signal of the dual-polarization signal in the Y polarization direction and the signal of the local oscillation in the Y polarization direction, to obtain coupled signals with different phase shifts in the Y polarization direction; a signal combination unit, connected to the signal diversity unit and configured to perform optical signal combination on a group of one coupled signal in the X polarization direction and one coupled signal in the Y polarization direction, to obtain a combined signal; and convert the combined signal to an electrical signal; and a digital-signal acquiring unit, connected to the signal combination unit and configured to receive the electrical signal output by the signal combination unit, and generate a digital signal of an electrical signal of the dual-polarization signal in the X polarization direction and a digital signal of an electrical signal of the dual-polarization signal in the Y polarization direction according to the received electrical signal.