Abstract

Single-mode fibers are really bimodal due to the presence of birefringence. The amplitudes of the two modes u and v satisfy the equations where δ = πcΔn/D(λ)λ₀ is the birefringence strength and R = 8πct₀/λ. Other parameters are defined as in Ref ¹. If we assume a pulse whose FWHM width is 5 ps, we find that 0.3 < δ < 3.0 for typical fibers. The smallest value of δ in actual fibers is 1.4 × 10⁻³, while R = 1.4 × 10⁻⁴. We then find that Rδ ≫ 1 in all cases, so that the exponential terms are rapidly oscillatory and can be dropped. As a consequence, there is always an effect due to the birefringence. Solitons which mix the two polarizations are a factor of 6–5 more intense than those which consist of a single polarization. Linearly, the two polarizations will split over 20 km when δ > 0.1, while nonlinearly the two polarizations are bound together even when δ = 1 if the normalized pulse amplitude is large enough to generate a soliton.

© 1986 Optical Society of America