- After certain initial length, the pulse distortion increases less rapidly because of mode The energy from one mode is coupled to other mods because of:
- Fiber diameter
- Refractive index variations.
- Microbends in
- Due to the mode coupling, average propagation delay become less and intermodal distortion
- Suppose certain initial coupling length = Lc, mode coupling length, over Lc = Additional loss associated with mode coupling = h (dB/ km).
Therefore the excess attenuation resulting from mode coupling = hZ. The improvement in pulse spreading by mode coupling is given as :
where, C is constant independent of all dimensional quantities and refractive indices. σc is pulse broadening under mode coupling.
σ0 is pulse broadening in absence of mode coupling.
- For long fiber length’s the effect of mode coupling on pulse distortion is significant. For a graded index fiber, the effect of distance on pulse broading for various coupling losses are shown in 2.8.1.
- Significant mode coupling occurs of connectors, splices and with other passive components of an optical