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Single Mode Fiber Coupling Sensitivities and Tolerancing

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

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Single Mode Fiber Coupling Sensitivities and Tolerancing

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  1. Single Mode Fiber CouplingSensitivities and Tolerancing Lori Moore

  2. 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

  3. Single Mode Fiber Definitions Variables used • ωo = mode field radius (1/e2) • n0 = index outside of fiber • λ = wavelength Lori Moore

  4. Loss Due to Lateral Misalignment Lori Moore

  5. Loss Due to Lateral Misalignmentλ = 1.3 μm ω0 = 4.65 μm Lori Moore

  6. Loss Due to Angular Misalignment Lori Moore

  7. Loss Due to Angular Misalignmentλ = 1.3 μm ω0 = 4.65 μm Lori Moore

  8. Loss Due to Longitudinal Misalignment Lori Moore

  9. Loss Due to Longitudinal Misalignmentλ = 1.3 μm ω0 = 4.65 μm n0 = 1 Lori Moore

  10. Loss Due to Mode Mismatch Lori Moore

  11. Loss Due to Mode Mismatchλ = 1.3 μm ω0 = 4.65 μm n0 = 1 Lori Moore

  12. 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

  13. Perturbation AnalysisCan’t Assume Linearity Lori Moore

  14. One Possible Solution Lori Moore

  15. 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

  16. Conversion from Decibels to Transmission Percent Calculating Loss in dB (LdB) Calculating Loss in % (L%) Lori Moore

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