Design of a double clad optical fiber with particular consideration of leakage losses

1. RESULTS AND DISCUSSION

1.1. Leakage loss calculation

1.1.1. The radiation losses associated with double-clad fiber with wide depressed cladding can be derived in terms of V2, γ, σ and κ (Leonard et al., 1982).

1.1.2. These losses are never zero because the HE11 fundamental mode is cutoff at all wavelengths. piecewise constant refractive index distribution

1.1.3. we observed that the predicted losses for a straight fiber could be significantly increased due to bending effects induced by cabling the fiber.

2. EXPERIMENTAL DESIGN

2.1. Propagation of ray in a leaky structure

2.1.1. In the design of the double clad optical fiber we considered that the optical fiber consists of one core and two cladding that is, the inner and the outer cladding

2.2. Cut-off characteristics

2.2.1. If β/k> n3, then there are no leakage losses. However, if the propagation constant is smaller, so that β/k < n3, then the mode is said to be “cut off” because power radiates through the outer cladding.

3. Comparisons

3.1. The design fiber with double clad has been compared with ordinary fiber at different aspects.

3.2. The cutoff number (Vc) of the single clad fiber is significantly higher than that of the double clad fiber. (Snyder and Love, 1983).

3.3. Wavelength (λc) in μm Cut-off value (Vc) 1.2 14.33 1.25 13.76 1.3 13.23 1.35 12.74 1.4 12.29 1.45 11.86 1.5 11.47

4. INTRODUCTION

4.1. In the leaky waveguides, the low refractive index surrounding region has a finite thickness comparable to the penetration depth of the guided field and beyond this distance the medium has a refractive index equal to or greater than that of the guiding region.

5. Conclusion

5.1. In this paper we have proposed a design of double clad optical fiber and analyzed its characteristics at different conditions with the single clad optical fiber.

5.2. The leakage losses under the bending effect are more than the normal non bending effect for values of λ= (1.3 - 1.45) μm as shown in Figure 8. As the ratio of x2/x1 is around (5 - 6), the difference in leakage loss at λ=1.3 μm and at λ=1.6 μm is quite less. But when the ratio of x2/x1 is around (6.5 - 9) the difference of the leakage loss at λ=1.3 μm and at λ=1.6 μm is comparably high.