Visible Fault Location For Optical Fiber Using A Red Chaotic Semiconductor Laser

Optical time domain reflectometry (OTDR) has been the main fiber fault measurement technique. The principle of OTDR is the detection of arriving time of back-reflected light, based on which the distance between the fault and initial position can be calculated out. However, the spatial resolution of OTDR decreases with the increase of measurement range. Furthermore, the location of fiber fault needs some assistant work, especially when the tested fiber is hidden under the earth. In this way, the location of fiber faults requires more in the human and material resources. Fortunately, experiment results demonstrate that the red semiconductor laser can operate in the chaotic state based on the optical feedback. Using the red chaos as the detection light, the faults distance measurement can be carried out by the correlation between the reference and back-reflected light, and the faults position can be obtained by the visible search based on the leakage of red chaos at fiber faults. Therefore, the fault visible chaotic optical time domain reflectometer, which can realize the fault distance measurement and visible search, has a broad future in the applications of fiber fault location, especially in the network based on the FTTx [fiber to the home (FTTH), fiber to the building (FTTB) and fiber to the curb (FTTC)].In this thesis, we study the dynamic characters of red chaos and the faults visible search based on the experimental and theoretical methods. The following are the main works:1. The dynamic characters of red chaos based on the optical feedback were studied theoretically. The route to chaos with the increase of feedback strength was studied, when the biased current and external cavity length were kept stable. The features at different states were compared from the time series, phase portraits and frequency spectrum.2. Variation of laser outputs with the different feedback levels when the biased current and external cavity length were kept stable were demonstrated experimentally. The period-doubling route to chaos of red semiconductor laser and the time series, phase portraits, power spectra and correlation traces at different states were studied.3. The auto-correlation properties of red chaos were studied. According to the requirement of chaotic correlation method, we choose the suitable region of red chaos.4. Fiber faults distance measurement and visible search was carried out based on the red chaos experimentally. We analyses the measurement performance of the proposed method, including the spatial resolution and dynamic range. And the methods of improving the measurement performance were proposed simultaneously.