Single-Mode Dual-Step Index

These fibers are single-mode and have a dual cladding. Depressed-clad fiber is also known as doubly clad fiber. Figure 3-10 corresponds to single-mode propagation with a refractive index profile that is called dual-step index.

A depressed-clad fiber has the advantage of very low macrobending losses. It also has two zero-dispersion points and low dispersion over a much wider wavelength range than a singly clad fiber. SMF depressed-clad fibers are manufactured using the inside vapor deposition (IVD) process. The IVD or modified chemical vapor deposition (MCVD) process produces what is called depressed-clad fiber because of the shape of its refractive index profile, with the index of the glass adjacent to the core depressed. Each cladding has a refractive index that is lower than that of the core. The inner cladding a the lower refractive index than the outer cladding.

August 25, 2011

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