Proposal for optical fiber designs with ultrahigh effective area and small bending loss applicable to long haul communications

A proposal for the multiclad MII optical fiber structure with ultralarge effective area and small bending loss is presented. For the proposed structure small dispersion and dispersion slope are obtained thanks to what we believe to be a novel design method. The suggested design method is based on a weighted fitness function, which is applied to the genetic algorithm optimization technique. In the meantime, the foregoing structure introduces a special fiber whose mode field diameter is small and approximately insensitive to the variation of the effective area. Compared to the work reported previously, our method can precisely set the zero dispersion wavelength. The designed dispersion-shifted single-mode fibers have effective area, mode field diameter, and quality factor respectively within [150-194.79] microm(2), [6.82-7.95] microm, and [3.04-3.85] at lambda(0)=1.55 microm. An analytical method is used for the calculation of the dispersion and its slope. These calculations give dispersion and dispersion slope of [(-2.57 x 10(-4))-(-0.085)] ps/km/nm and approximately 0.064 ps/km x nm(2), respectively.     

非接触式光纤内螺纹测试装置

为克服接触式测量内螺纹方法的不足,研制了基于强度调制型光纤传感器的非接触测量装置.通过与特制的机械结构相结合.实现了相对效率高、速度快、且便于应用的内螺纹参数的测量.该装置主要由进给平台和光纤探头组成,同时采用半导体激光光源(LD)作光源,光电二极管为光电转换器件.测量的信号经光路转换及前置放大后,通过采样保持送入数据采集系统,经数据处理软件Matlab进行处理得出螺距误差.实验表明,经适当改进后,该方法可用于工业生产过程中内螺纹的非接触测量.     

温度应变同时测量的光纤光栅系统的研究

为了同时传感温度和应变,在同一根光纤的两个不同地方写入相同的Bragg光栅,设计制成一种特殊机构的传感系统。由于测量结构特殊,两处光纤光栅的反射峰具有成比例的应变响应系数和不同的温度响应,测出温度后,应变也同时算出。实际测量表明,该系统结构简单,测量精度高,能进行实时测量。     

High-spatial-resolution distributed strain measurement in optical fiber with rayleigh scatter

A method of measuring strain over 30-cm intervals to an accuracy of10 microstrain in unaltered low-loss communications-grade single-modeoptical fiber is presented. The method uses a tunable external cavity diode laser to measure the reflected intensity of a reflector-fiber system as a function of wavelength. This measurement is performed with no strain applied to the fiber to produce a reference and then again after a strain has been induced. Cross correlation of the Rayleigh scatter spectra from a selected section of fiber in the strained and unstrained states determines the spectral shift resulting from the applied strain.     

An automatic commutating device for multicurve strain recording

Conclusion The commutating device described provides facilities for working with any strain-gauge transducers. It can be used with carrier frequency amplifiers and circuits without amplifiers working on direct or alternating current. In addition, the device can be used for checking temperature and many other parameters.     

应变、温度、位移测量光纤光栅传感器的研究

本文介绍了集成式Bragg光纤光栅(FBGI)传感器的结构及其应用该传感器测量应变、温度、位移的基本原理.利用FBGI和相干性干涉信号解调方法实现了用一个传感器同时测量三个参量.实验结果表明温度精度达±1℃,应变精度为±30u ε,位移分辨率达1nm,测量重复性好.     

Thermal characteristics of optical pulse transit time delay and fiber strain in a single-mode optical fiber cable

Thermal characteristics of optical pulse transit time delay and fiber strain in a single-mode optical fiber cable are investigated theoretically and experimentally. Measurements of the transit time delay shift are made by a spatial interference technique using a 1.5-in long fiber, six-fiber unit, and cable. Experimental results for a jacketed fiber whose fiber axis is well centered in nylon coating are in good agreement with those predicted from the theory. A jacketed fiber whose fiber axis is positioned eccentrically from the jacket center exhibits a small change in fiber strain at low temperature due to fiber buckling compared with that for the well-centered jacketed fiber. The loss increase for the off-centered jacketed fiber is explained by the buckling model. Furthermore, thermal characteristics of the unit-type cable examined here are found to coincide with those for the constituent six-fiber unit.     

一种新型全光纤弹速测量系统的研制

研制了一种新型的利用激光光束反射原理的全光纤弹速测量系统。该系统采用了全光纤结构和光纤耦合器等无源器件,以输出光功率1mW, 工作波长1300nm的半导体激光器作为测试系统的光源,用光纤耦合器进行分光,实现了在一根光纤中同时传输光源和接受目标反射的信号光,避免了复杂的调节和准直过程。该系统结构简单、可靠性高,利用它,成功地测量了霍普金森杆发射的子弹速度,结果表明其速度测量相对不确定度小于1%。     

An optical strain measurement system for asphalt mixtures

Knowledge of the conditions governing the initiation and propagation of cracks in hot mix asphalt (HMA) mixtures is a prerequisite for a comprehensive understanding of HMA cracking mechanisms. Traditional strain measurement sensors have proved to be not completely adequate in the sense that they do not provide pointwise measurements, thus not pinpointing the location of crack initiation, and not accounting for non-uniform strain distributions. This paper presents a digital image correlation (DIC) system for non-contact and full strain field measurements, conceived for the purpose of investigating the cracking behavior of HMA mixtures. The whole system was developed so as to account for the special nature of typical HMA testing configurations. An image matching technique (least squares matching) was employed for providing matches with sub-pixel accuracy. The performance of the method was investigated by several tests. The DIC system was shown to overcome the shortcomings of traditional on-specimen strain measurement devices achieving satisfactory accuracy compared to strain gauges.     

An optical fiber sensor for remote pH sensing and imaging

A fiber-optical probe for pH sensing and real-time imaging is successfully fabricated by connecting a polymer imaging fiber and a gradient index (GRIN) lens rod which was modified with a sensing film. By employing an improved metallographic microscope, an optical system is designed to cooperate with the probe. This novel technique has high-quality imaging capabilities for observing remote samples while measuring pH. The linear range of the probe is pH 1.2-3.5. This technique overcomes the difficulty that high-quality images cannot be obtained when directly using conventional imaging bundles for pH sensing and imaging. As preliminary applications, the corrosion behavior of an iron screw and the reaction process of rust were investigated in buffer solutions of pH 2.0 and 2.9, respectively. The experiment demonstrated that the pH values of the analytes' surface were higher than that of buffer solutions due to the chemical reaction. It provides great potential for applications in optical multifunctional detection, especially in chemical sensing and biosensing.     

Spectrum-sliced Fourier-domain low-coherence interferometry for measuring the chromatic dispersion of an optical fiber

We present a novel spectrum-slicing method for measuring the chromatic dispersion of an optical fiber in Fourier-domain low-coherence interferometry. Broadband spectral interference data obtained from a low-coherence interferometer is sliced with Gaussian window functions. Each sliced spectral datum is used to calculate a relative group delay with Fourier transformation at the peak wavelength of a narrow window function. We have demonstrated that our proposed method is very powerful and simple for measuring chromatic dispersion and second-order dispersion in optical fibers and optical devices. Comparison of the proposed method with a conventional measurement method agrees within 0.5%.     

An optical glass plane angle measuring system with photoelectric autocollimator

Optical glass is the most widely used optical material. It is necessary to measure its geometric characteristic quickly and reliably to meet the quality of optical glass. A vision measuring system combining photoelectric autocollimation system with high-precision rotary stage is designed to measure the parallelism and angle of optical glass plane. A novel method is proposed to overcome the difficulty of measuring parallelism of optical glass.The model of parallelism and angle measurement is established and the feasibility is analyzed. The image processing algorithm combining Steger algorithm with the least square method is selected. The uncertainty of angle measurement system for angle measurement is 3.0″. The system can solve the problem of measuring the angle of optical glass with high precision and has important significance for optical system.