Abstract

The analytical formulas of dispersion and mode field radii variation due to the preformfiber drawing ratio (s) and the core-clad index difference (Δn) is derived to approach low loss dispersion-flattened fibers with multiple-cladding. If s²Δn is constant, bend and splice loss will be approximately invariant; both lowering s and raising Δn will lower the dispersion curve. This approach can result in great waveguide dispersion without increasing loss; if s Δn is enlarged, the dispersion curve can be designed to be basically invariant by appropriately lowering s and raising Δn, while bend and splice loss is reduced. Hence the combination of higher core-clad index difference and smaller drawing ratio will be more reasonable for actual low loss dispersion-flattened fibers. On the other hand, adjusting s can compensate dispersion deviation due to disturbed Δn, especially for λ < 1.55 μm. Beyond 1.55 μm, lowering s and raising Δn might make the dispersion-flattening property poor. By selecting suitable s and Δn and adjusting other parameters of arbitrary quadruple-clad profile, low loss dispersion-flattened fibers may be optimized and trial-fabricated.

© 1992 Optical Society of America