The Software Design And Implementation Of Fiber-optic Refractive Index Profile Measuring System

With the continuous development of fiber-optic technology, a variety of new type fiberkeep coming up, and are widely used in the field of fiber-optic communication and sensing.As an important parameter, the refractive index profile of fiber directly affects thetransmission characteristics of fiber, and with the refractive index profile, the geometricparameters and the maximum theoretical numerical aperture of fiber can be calculated.Therefore, accurately measuring the refractive index profile and accurately evaluating thequality of the fiber are with great significance for the development of fiber-optic technology.As a benchmark method for the measurement of the refractive index profile of fiber,refracted near-field technique has many advantages, such as small spatial resolution, highmeasuring accuracy, good repeatability, and without leakage mode correction. The paper aimsto study the software design and implementation of fiber-optic refractive index profilemeasurement system, which is based on refracted near-field technique, work details are asfollows:Firstly, we research on the common method for measuring fiber refractive index profile,including the reflection method, the near-field scanning method, interferometry and focusingmethod; besides deeply study on the basic principle of refracted near-field technique, andderive the calculation formulae of refractive index profile, fiber geometry parameters and themaximum theoretical numerical aperture.Next, the system composition of refractive index profile measuring system is presentedin the paper, including the mechanical structure, the hardware circuit, optical part andsoftware part. Combined with the current conditions, we propose the system software designscheme with LabVIEW, introduce the implementation of software, including focusedplatform control module, X-Y two-dimension scanning platform control module, photodetector data acquisition module, the calculation and display part of refractive index profile,software parameter configuration, data storage and read part, and measurement module.Finally, we present the function and use of the system software in detail. Meanwhile, wemeasured the standard multi-step index reference fiber and analyzed the experimental results;tested62.5/125μm graded index multimode fiber, got the refractive index profile data, geometry parameters and the maximum theoretical numerical aperture, and compared theresults with the standard data.