In this paper, a novel scheme of stabilizing all-optical clock recovery is proposed, which uses a mode-locked fiber ring to extract the same frequency clock pulses from the uneven multiplexing 4×10Gbps optical signals. The super-mode suppression ratio reaches 60dB (for signals of 10Gbit/s) and an improvement of 20dB is achieved by adding stabilization devices. Wavelength shift is less than 0.01nm within 2 hours, and this value is about one sixties of that without adding stabilization devices. The results show much better cavity length stability and noise suppression performance.
Stimulated Brillouin scattering (SBS) is one of important nonlinear effects in optical fiber communication systems. Due to its low threshold, it limits the optical power that couples into the fiber. In this paper, Stimulated Brillouin scattering and the effect of phonon loss to SBS in optical fiber communication systems are investigated. In experiments we measure first the power of backward Stokes wave and output light under various input powers of the systems with different lengths of fibers. Then for observing the effect of the phonon blocker to the SBS threshold, we repeat the same experiments but with a phonon blocker inserted at different locations of the fiber link. The experiments indicate that adding phonon blocker to the fiber is able to increase the SBS threshold, and the blocker at different locations makes different effects.
It is important to know how the degree of polarization (DOP) changes with differential group delay (DGD) when DOP is the feedback parameter for an adaptive polarization mode dispersion compensator (PMDC). We derived the mathematical expression of DOP for pulse sequence with arbitrary and Gauss waveforms under the condition of quasi-monochromatic wave, then analyzed theoretically the relation between DOP and DGD with different power splitting ratio and pulse width. Then we carried out the experiments of DOP with 10Gbit/s RZ/NRZ pseudo random sequence pulses and made comparison between theoretical calculation and experimental data. The comparison showed that they matched closely. We also verified by experiments that DOP is independent of fiber dispersion.