The Research On Improved C-Lens And The Optimization Of Structure And Parameter

Today, optical fiber communication has become the main transmission mode andhas been widely used in various fields. The passive devices are very importantcomponents of optical fiber communication, such as optical Isolators, opticalCirculators, optical Switches, optical Attenuator, optical WDM, etc. In the course of itworks, there is a certain distance between the input and output fiber end, then opticalcomponents can be inserted to achieve the device function. Typically the light sourceused in optical fiber communication systems is the Fundamental Gaussian beam, thebeam emitted from the optical fiber end face is divergent light with divergent angle,and it cause severe loss of light energy through the optical path, so it is bad to thetransmission of light and coupling. Fiber collimator is used in passive components asthe role of changing the divergent light to a parallel beam, or collimating the parallelbeam into the fiber, so it improves the coupling efficiency of the optical devices.Now, the main components used in fiber collimator are GRIN Lens and C-Lens.C-Lens fiber collimator has the advantage of low Insertion Loss, large WorkingDistance range and low cost, due to these better performances than GRIN Lens,C-Lens is widely used in production for domestic and foreign manufacturers ofoptical devices. However, the EU implement has demanded the RoHS compliancestarting from July1st,2006, C-Lens material was changed to N-SF11instead of SF11.But N-SF11material has the disadvantage of poor optical stability and large thermalexpansion coefficient, it brings the problems of large drift of IL and lens crackingissue, which brought trouble to the fiber optic product, so the market requires muchhigher performance C-Lens. After studying a large number of references, this papermakes detail analysis on the material properties, select the suitable material, and findout the solution to improve the thermal stability. By optimizing the product structureand parameters, the improved C-Lens Collimator has been achieved with lowinsertion loss, low temperature drift of insertion loss and the high-temperaturewelding assembly performance.The research contents of this paper include:1. The fiber collimator history, characteristics and development prospects arestudied, and the current status and problems of C-Lens are introduced. 2. C-Lens design principle, Gaussian beam, and ABCD matrix are studied, whichis the theoretical basis of C-Lens design and research. And optical glass material,main optical parameters and product thermal stability factor are also analysed.Summarized the improving solution of the thermal stability and lower IL, by selectingsuitable new materials of S-NPH2and optimizing the product parameter and theproduct structure, the improved C-Lens design has been achieved.3. The comparing test of N-SF11and S-NPH2fiber collimator has been done,especially high temperature&high humidity test and temperature cycling test. Afterthe analysis on the test data, S-NPH2material is more suitable for the processing ofC-Lens products with IL <0.2dB,△IL <0.05dB. The improved C-Lens collimator iswell with low Insertion loss, low temperature drift and stability of high-temperaturewelding assembly.