210 likes | 488 Views
Single Mode Fiber Coupling Sensitivities and Tolerancing. Overview. Basic Definitions Misalignments Lateral Angular Longitudinal Mode mismatch Example Tolerancing Problem Coupling between two single mode fibers in air Figure of Merit – Coupling Efficiency Why
E N D
Single Mode Fiber CouplingSensitivities and Tolerancing Lori Moore
Overview • Basic Definitions • Misalignments • Lateral • Angular • Longitudinal • Mode mismatch • Example Tolerancing Problem • Coupling between two single mode fibers in air • Figure of Merit – Coupling Efficiency • Why • Starting point for more complex systems • Non-linear tolerancing problem Lori Moore
Single Mode Fiber Definitions Variables used • ωo = mode field radius (1/e2) • n0 = index outside of fiber • λ = wavelength Lori Moore
Loss Due to Lateral Misalignment Lori Moore
Loss Due to Lateral Misalignmentλ = 1.3 μm ω0 = 4.65 μm Lori Moore
Loss Due to Angular Misalignment Lori Moore
Loss Due to Angular Misalignmentλ = 1.3 μm ω0 = 4.65 μm Lori Moore
Loss Due to Longitudinal Misalignment Lori Moore
Loss Due to Longitudinal Misalignmentλ = 1.3 μm ω0 = 4.65 μm n0 = 1 Lori Moore
Loss Due to Mode Mismatch Lori Moore
Loss Due to Mode Mismatchλ = 1.3 μm ω0 = 4.65 μm n0 = 1 Lori Moore
Example Tolerancing Problem • Goal • Loss < 0.46 dB (10%) • Other constrains • Fiber to Fiber coupling • Wavelength = 1.3 μm • Mode field radius = 4.65 μm (1/e2) • Gap material is air (n = 1) Lori Moore
Perturbation AnalysisCan’t Assume Linearity Lori Moore
One Possible Solution Lori Moore
Closing Remarks and References • Other issues to consider • Dirt on fiber • Burning the fiber with too much power • Humidity • Wavelength • References • OFR catalogue • http://www.ofr.com/misc/OFR_2001_Fiber.pdf • Further Reading • For gaussian beam propagation • Lasers, A. E. Siegman (1986) especially Chapter 17 and 20 Lori Moore
Conversion from Decibels to Transmission Percent Calculating Loss in dB (LdB) Calculating Loss in % (L%) Lori Moore