  We report a laser noise reduction method by locking it to an actively
stabilized fiber-based Mach Zehnder interferometer with 10 km optical fiber to
achieve large arm imbalance. An acousto optic modulator is used for
interferometer stabilization and heterodyne detection. The out-of-loop
frequency noise is reduced by more than 90 dB for Fourier frequency at 1 Hz.
This structure presents an efficient laser noise reduction method both at high
Fourier frequency and low Fourier frequency. The signal of stabilized laser is
transferred via a 10 km fiber link with a fractional frequency stability of
1.12 times 10-16 at 1 s. Compared with the fractional frequency stability of
that when the interferometer is not stabilized, more than one order of
magnitude is improved.
