A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening.

Optoelectronics and Optical Communication 

A multimode fiber has RMS pulse broadening per km of 12ns/km and 28ns/km due to material dispersion and intermodal dispersion resp. Find the total RMS pulse broadening.

a) 30.46ns/km 
b) 31.23ns/km 
c) 28.12ns/km 
d) 26.10ns/km

Answer : - 30.46ns/km 

The overall dispersion in multimode fibers comprises both chromatic and intermodal terms. The total RMS pulse broadening σ T is given by 
Where σm = RMS pulse broadening due to material dispersion 
σ i = RMS pulse broadening due to intermodal dispersion.