Research Of High Speed SOP Measurement In Optical Fibers And POTDR

Nowadays, the high-speed state of polarization (SOP) measurement is an important and urgent subject for optical fiber communications, and the measurement technologies can be applied in polarization compensation for coherent optical communications, polarization multiplexing, polarization encoding communications, measurement and compensation of polarization mode dispersion (PMD), etc. Meanwhile, high-speed SOP measurement technologies can also be applied in optical fiber sensing, and the application can improve the measurement accuracy, resolution and real-time ability for polarization-sensitive optical time domain reflectometry (POTDR). The high-speed SOP measurement based POTDR can measure the distribution of PMD along the length of an optical fiber, which will help to improve the PMD properties of optical fiber links for overcoming the PMD limit of40Gbps and above high-speed communication systems. The main research directions of this dissertation are the polarization effects in optical fibers and devices, the method of high-speed SOP measurement in optical fibers, the high-speed SOP measurement baesd POTDR system and the method of PMD spatial distribution measurement. The researches have great significances for more than40Gbps high-speed optical fiber communications and polarization sensitive distributed optical fiber sensing technologes. The main innovations of this dissertation are as follows:1. Under the condition of single optical frequency, a new Mueller transfer matrix was deduced for co-existence of the three polarization effects, polarization dependent phase shift (birefringence), polarization dependent gain (loss) and the polarization mode coupling in optical fibers or optical waveguides. Based on the simulation results, a new phenomenon of SOP rotational contraction was observed, which can be considered as a long-distance dichroism.2. On-line polarization controllers (PC), fiber optic polarization beam splitters (PBS) and differential detection based high-speed SOP measurement method was proposed and the experimental setup was implemented, while a new calibration method which can use a low-speed polarization analyzer as a benchmark was also proposed. Under ideal conditions, there are more than one PC angle combinations which can satisfy the calibration requirements by theoretical analysis. The digital optical signal SOP measurement rate of this measurement system have achieved maximum500Mbps.3. A new high-speed SOP measurement based POTDR system was proposed, which can be used to directly observe the three Stokes parameters time domain waveforms of Reyleigh backscattering light in optical fibers, while a new algorithm for calculating the birefringence vector distribution along the length of an optical fiber--three points algorithm was also proposed. Using the POTDR setup, the measurements of the first-order and the second-order local birefringence vector distributions along an optical fiber under test have been achieved for the first time. Compared with the measurement results, the data of second-order birefringence vector distribution may provide more information and a higher signal to noise ratio (SNR) for the first-order birefringence measurement based optical fiber sensing technologies.4. According to the dynamic equation of PMD vector Ω and birefringence vectorβ, a new solution of the dynamic equation was proposed based on the Ω slowly-varying approximation ((?)2Ω/(?)z2≈0). Then, based on the POTDR system with a tunable light source and the high-speed SOP measurement, a new algorithm of the PMD vector distribution along the length of an optical fiber was proposed, which use the measured data of the birefringence vector distributions at multiple wavelengths. For the first time, the local PMD vector distribution along an optical fiber under test have been calculated from the local birefringence vector distributions at three wavelengths, and the locations and sizes of the abnormal PMD in the optical fiber were detected. The engineering application of this technology can be used for monitoring the PMD vector in the optical cables.