  Optical-fiber-based polarization scramblers can reduce the impact of
polarization sensitive performance of various optical fiber systems. Here, we
propose a simple and efficient polarization scrambler based on an all optical
Mach-Zehnder structure by combining polarization beam splitter and amplified
fiber ring. To totally decoherence one polarization splitted beam, a fiber ring
together with an amplifier are incorporated. The ratio of two orthogonal beams
can be controlled by varying the amplification factor, and we observe different
evolution trajectories of the output state of polarizations on Poincare sphere.
When the amplification factor exceeds a certain threshold, the scrambler system
exhibits chaotical behavior. A commercial single wavelength laser with
linewidth of 3 MHz is utilized to characterize the scrambling performance. We
found that when the sampling rate is 1.6 MSa/s, a scrambling speed up to 2000
krad/s can be obtained for the average degree of polarization being less than
0.1. We also exploit these chaotic polarization fluctuations to generate random
binary number, indicating that the proposed technique is a good candidate for
random bit generator.
