also having three components. So we have total 6 field components. However all these components are not independent of each other since are related through the Maxwell's equations. We can take two components as independent components and express the remaining four components in terms of the independent components. Since in this case the wave propagates along the axis of the fiber i.e., in the direction, generally the two components, (also called the longitudinal components) are taken as independent components and the other four transverse field components i.e., are expressed in terms of these two components.

The wave equation is solved for the two longitudinal components and the transverse components can be obtained by substitution of the longitudinal components in the Maxwell's equations.

where ( is the propagation constant of the wave along the axis of the fiber. This parameter is defined subsequently)