Specialty Optical Fibers Handbook

2.7.3 Waveguide Dispersion

The chromatic dispersion of a step-index single-mode fiber resulting from

waveguide effects is referred to as waveguide dispersion. Although not explicitly

discussed in Section 2.1, solutions to the Helmholtz equation for the electric

fields in the cylindrical waveguide and the associated eigenvalues, u, w, and b, are

wavelength dependent. Recall that b and b

t

must obey the relationship

b

t1

¼ (n

2

1

k

2

0

 b

2

)

1=2

. Therefore, even if n

1

is assumed to be constant (i.e., there

is no material dispersion), the wavelength dependence of k

0

¼ 2p=l results in

variation of b and b

t

with wavelength. By recasting Eq. (2.22) for group delay in