  As part of the effort to make use of squeezed states of light for detection
of sub-shot-noise optical signals, we study the balanced heterodyne scheme, for
which the corresponding spectral density of the photocurrent fluctuations
produced at the output of the detector is calculated as the Fourier transform
of their autocorrelation function. Our analysis shows that, for maximal
signal-to-noise ratio enhancement by use of squeezed states of light, an
optical signal to be measured must be carried in the squeezed quadrature of the
carrier field. We discuss how "the additional heterodyne noise" can be
eliminated in this scheme and its potential application to gravitational-wave
searching. To demonstrate the practical feasibility, we propose and study a
phase-locking technique for this scheme.
