  We experimentally demonstrate a quantum receiver based on Kennedy scheme for
discrimination between two phase-modulated weak coherent states. The receiver
is assembled entirely from the standard fiber-optic elements and operates at
the conventional telecom wavelength 1.55 microns. The local oscillator and the
signal are transmitted through different optical fibers, and the displaced
signal is measured with a high-efficiency superconducting nanowire
single-photon detector. We show the discrimination error rate two times below
the shot-noise limit.
