Periodic structure in graded-index multimode fiber

Abstract

13 2.1 Overview 2.2 Graded-index multimode fiber 2.3 Vector modes of parabolic-index multimode fiber 2.4 Review of coupled-mode theory 2.5 Phase matching of mode coupling 2.6 Formation of periodic structures in GRIN MMF 2.6.1 Photosensitivity and photo-induced grating 2.6.2 CO2 laser method 2.6.3 Periodic microbending 2.7 Review of periodic structures in GRIN MMF 2.7.1 Multimode fiber Bragg grating 2.7.2 LPG in GRIN MMF 2.7.3 GRIN MMF with Periodic Microbend CHAPTER 3 BRAGG GRATING IN GRADED-INDEX MULTIMODE FIBER 48 3.1 Overview 3.2 Fabrication 3.3 Spectral analysis 53 3.4 Mode Coupling in an MMFBG 60 3.5 Sensitivity characteristics of an MMFBG 65 3.6 Conclusions 69 CHAPTER 4 LONG PERIOD GRATING IN GRADED-INDEX MULTIMODE FIBER 71 4.1 Overview 71 4.2 Fabrication 73 1 ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library TABLE OF CONTENTS 4.3 Mode coupling 4.4 Properties of MMF LPG 4.5 Sensing applications of the MMF LPG 4.5.1 Strain sensor 4.5.2 Chemical Sensor 4.6 Conclusions CHAPTER 5 PERIODIC MICROBEND IN GRADED-INDEX MULTIMODE FIBER 97 5.1 Overview 5.2 Periodicity of GRIN MMF 5.3 Theory of microbend-induced mode coupling 5.4 Mode scrambler based on periodic microbend 5.5 Near field images 5.6 Fiber microbend sensors 5.6.1 Generic fiber microbend sensor 5.6.2 FBG incorporated Microbend sensors 5.7 Conclusions CHAPTER 6 APPLICATIONS OF MMFBG IN ERBIUM-DOPED FIBER LASERS 139 6.1 Overview 6.2 Erbium-doped fiber laser 141 6.3 Microbending scheme 143 6.3.1 Principle of operation 143 6.3.2 Experimental results and discussions 149 6.4 Alignment scheme 153 6.4.1 Principle of operation 154 6.4.2 Experimental results and discussions 161 6.5 Conclusions 166 CHAPTER 7 CONCLUSIONS AND RECOMMENDED FUTURE WORKS 168 7.1 Conclusions 168 7.2 Recommended future work