1. Dec. 5, 2006Lori Moore1 Single Mode Fiber Coupling Sensitivities and Tolerancing

2. Dec. 5, 2006Lori Moore2 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

3. Dec. 5, 2006Lori Moore3 Single Mode Fiber Definitions Variables used ω o = mode field radius (1/e 2 ) n 0 = index outside of fiber λ = wavelength λ (um)ω 0 (um) 1.555.25 1.34.65 1.063.1 0.862.5 0.631.85

4. Dec. 5, 2006Lori Moore4 Loss Due to Lateral Misalignment

5. Dec. 5, 2006Lori Moore5 Loss Due to Lateral Misalignment λ = 1.3 μm ω 0 = 4.65 μm

6. Dec. 5, 2006Lori Moore6 Loss Due to Angular Misalignment

7. Dec. 5, 2006Lori Moore7 Loss Due to Angular Misalignment λ = 1.3 μm ω 0 = 4.65 μm

8. Dec. 5, 2006Lori Moore8 Loss Due to Longitudinal Misalignment

9. Dec. 5, 2006Lori Moore9 Loss Due to Longitudinal Misalignment λ = 1.3 μm ω 0 = 4.65 μm n 0 = 1

10. Dec. 5, 2006Lori Moore10 Loss Due to Mode Mismatch

11. Dec. 5, 2006Lori Moore11 Loss Due to Mode Mismatch λ = 1.3 μm ω 0 = 4.65 μm n 0 = 1

12. Dec. 5, 2006Lori Moore12 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/e 2 ) –Gap material is air (n = 1)

13. Dec. 5, 2006Lori Moore13 Perturbation Analysis Can’t Assume Linearity

14. Dec. 5, 2006Lori Moore14 One Possible Solution

15. Dec. 5, 2006Lori Moore15 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

16. Dec. 5, 2006Lori Moore16 Conversion from Decibels to Transmission Percent Calculating Loss in dB (L dB )Calculating Loss in % (L % )