针对空芯光子带隙光纤宽带宽、高效率、高精度的色散测量需求，本文基于干涉法，提出一种适用于测量空芯光子带隙光纤宽带色散的相位提取方法，建立了基于 Mach-Zehnder干涉仪的色散测量系统，开展了空芯光子带隙光纤(HC-PBGF)色散特性的实验研究，重点对研制的19 cell HC-PBGF的色散特性进行了系统的实验研究。实际测量得到19 cell HC-PBGF在1400—1630 nm带宽范围内的基模色散曲线，开展了HC-PBGF的高阶模色散测量研究，测量得到了19 cell HC-PBGF四条高阶模色散曲线。实验测量结果与理论仿真结果吻合，研究成果为深入探究空芯光子带隙光纤的色散特性，推进其在高功率激光脉冲传输、大容量数据通信、光纤非线性等领域的应用具有重要意义。%Due to the unique optical properties of low loss, low nonlinearity, high threshold and low latency, hollow core bandgap fibers are endowed with high expectations in the field of high power delivery, optical fiber communication, nonlinear optics, fiber sensors, etc. Fiber dispersion, as one of the basic transmission characteristics of optical fiber, makes the light pulse broadened during transmission, thus has adverse effects on high power pulse transmission system and high speed optical communication system. Therefore, it is significant to study the dispersion characteristics of the hollow core bandgap fiber for its applications in the field of high power pulse transmission and high speed communications. Because of the simple structure of measurement system, low cost, high accuracy and relatively short length of fiber (just needing a few meters long), interferometric technique is suitable for dispersion measurement of hollow core photonic bandgap fiber. The key to obtaining the dispersion results with interferometric technique is the phase extractiton from the interferogram. In order to meet the requirements of hollow core bandgap fiber for wide bandwidth, high efficiency and high accuracy dispersion measurement, a novel phase extraction method based on interferometry is proposed in this paper, by which the precision of dispersion measurement is improved through using the whole data-set in the interferogram. Combining with the determinations of the peak and center of symmetry points, the extraction of phase information can be implemented directly from the interferogram. The experimental results of measuring a standard single mode fiber indicate that the difference between the experimental measurement and theoretical simulation is just 0.6 ps·nm−1·km−1, which proves that this proposed method possesses high accuracy and is suitable for the measurement of hollow core bandgap fiber. Consequently, according to the proposed phase extraction method, the measurement system based on Mach-Zehnder interferometer is set up and the dispersion measurement of a 19 cell hollow core bandgap fiber with a core diameter of 26 µm is carried out. Experimental results indicate that the fundamental mode dispersion curve of the 19 cell hollow core photonic bandgap fiber in a wavelength range from 1400 nm to 1630 nm can be obtained. Moreover, four high order mode dispersion curves are obtained for the first time. The measurement results are in accordance with the simulation results. These findings are of significant importance for exploring the dispersion characteristics of hollow core photonic bandgap fibers, and also conducible to their applications in the fields of high power laser delivery, high capacity data communications, optical fiber nonlinear, etc.
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