Design and analysis of large-mode-area microstructured polymer optical fibre with single-mode operation

Abstract

ABSTRACT A single mode microstructured polymer optical fiber has been designed and analysed based on finite element method (FEM). The design parameters of proposed microstructured polymer optical fiber structure have been optimized to obtain single mode operation along with mode area of 895 µm 2 . The differential loss between fundamental and higher order modes of structure have been obtained very large (~10 3 ) with negligible loss of fundamental mode. The proposed structure is effectively single mode at 632.8 nm wavelength after the short distance 1.65 m with very low loss of guiding mode. The proposed structure is applicable for high power delivery devices. Keywords : Microstructured polymer optical fiber, Large mode area, Single mode operation, Low leakage loss. 1. INTRODUCTION Microstructured optical fibers (MOFs) based on silica glass material, now days, have become an interesting research topic in the development of new optical devices in many re search fields, such as the telecommunication, high power applications and sensing of gaseous, chemical and biologi cal samples [1-10]. Significant efforts have been made by the authors to design MCVD large-mode-area (LMA) fibers using leaky cladding structures in recent past [11-14]. For the polymer fiber community, the recent development of microstructered polymer optical fiber in 2001 opened up a number of possibilities [15]. Microstructured polymer optical fibres are an exciting new development, offering opportunities to develop fibres for a wide range of applications in telecommunications, fiber lasers and optical sensing. Use of polymer materials instead of silica for the fa brication of these fibres allo ws for an even wider range of optical properties to be obtained. The microstructured polymer optical fibers (mPOFs), which have a lower melting temperature, more flexible hole patterns, easier manipulation and improved biocompatibility compared to their silica-based counterparts. Many doppents can be introduced to the polymers after polymerization using solution doping technique [16]. Using this technique it is easy to make single mode polymer fiber and such fiber could have a large number of applications including microstructured polymer optical fiber laser, nonlinear optically active fiber and particularly in sensing. For these applications to be realistic, the loss of the fibers has to be reduced to more acceptable levels. It requires much lower processing temperature an d controllability of the polymerization process allow a variety of ways to produce the polymer preforms. The polymer preform can be made using extrusion and polymer casting techniques. The advantages of mPOFs over silica fiber includes (i) The fluids such as liquids or gases can be introduce in to the mPOF; (ii) We are able to modify the structure to maximize the evanescent fiel d, such as the use of shielded nano-wires; (iii) Macrostructure polymer opti cal fibers are able to chemically func tionalize the surfaces of the holes, and ensure a significant interaction with the surface; (iv) Macrostructure polymer optical fibers allow the guidance of light in low refractive index material either by effective index guidance or band gap guidance.