  We present the experimental measurement of a squeezed vacuum state by means
of a bichromatic local oscillator (BLO). A pair of local oscillators at $\pm$5
MHz around the central frequency $\omega_{0}$ of the fundamental field with
equal power are generated by three acousto-optic modulators and phase-locked,
which are used as a BLO. The squeezed vacuum light are detected by a
phase-sensitive balanced-homodyne detection with a BLO. The baseband signal
around $\omega_{0}$ combined with a broad squeezed field can be detected with
the sensitivity below the shot-noise limit, in which the baseband signal is
shifted to the vicinity of 5 MHz (the half of the BLO separation). This work
has the important applications in quantum state measurement and quantum
information
