Signal-to-noise Ratio Improvment For Correlation Optical Fiber Fault Location System Based On Chaotic Laser

Chaos, a kind of noise-like signals, generated by deterministic nonlinear dynamical system, has good autocorrelation performance. Previous researches indicate that broad bandwidth chaos can be easily obtained by semiconductor laser subjecting optical feedback, optoelectronic feedback or external optical injection under appropriate conditions. Benefiting from the broad bandwidth and good autocorrelation performances of chaotic laser, chaotic correlation optical time domain reflectometer can locate the faults along fiber with a high, range-independent resolution. However, its signal-to-noise ratio is limited by the peak sidelobe on cross-correlation trace of chaotic laser employed. Fortunately, it is experimentally found that the peak sidelobe on autocorrelation trace of chaotic laser generated by optical feedback semiconductor laser can be suppressed below the noise level without degradation of its full-width at half-maximum (FWHM) through a fiber ring resonator. Thus, chaotic correlation optical time domain reflectometer has broad application prospects for diagnosing the damage events in fiber communication systems. In this thesis, we experimentally research the signal-to-noise ratio improvement for chaotic correlation optical fiber fault location system by suppressing the peak sidelobe on autocorrelation trace and enhancing the low-frequency power of chaotic laser employed via a fiber ring resonator, and adopting appropriate algorithms of data processing. The main works are summarized as below:1. Based on the good autocorrelation characteristic of broad bandwidth chaotic laser and digital oscilloscope, we illustrate the operational principle of high-resolution chaotic laser correlation optical time domain reflectometer employing the chaotic laser generated by optical feedback semiconductor laser as probing signal.2. Inserting a fiber ring resonator into the optical feedback cavity of optical feedback semiconductor laser, we experimentally find that the peak sidelobe on the correlation trace of chaotic laser can be suppressed below the noise level without degradation of its full-width at half-maximum.3. Utilizing a fiber ring resonator, we experimentally find the spectra of chaotic laser generated by optical feedback semiconductor laser can be reshaped. The chaotic energetic component at lower frequencies has been enhanced considerably to improve the actual available power for certain electronic bandwidth of data capture system.4. Furthermore, after chaotic laser with better autocorrelation characteristic and higher power at low frequency is employed as probing light, some algorithms of data processing are adopted to further improve the signal-to-noise ratio level of correlation optical fiber fault location system based on chaotic laser.5. At last, we experimentally qualify the spatial resolution, dynamic range and sensitivity of correlation optical fiber fault location system based on chaotic laser after signal-to-noise improvement.