Frequency response of Multimode (MM) fibers

beyond the baseband is studied both theoretically and

experimentally. It is shown that in the absence of mode group

mixing there are relative flat passbands suitable for transmission

in such fibers if the number of mode groups propagating is not

too large. Such conditions are usually met for typical

contemporary graded index (GI) silica fibers. It is also proved

that the passbands width is related to the baseband width.

Moreover, the 1300 nm window is the most suitable for

transmission due to small chromatic dispersion and reduced

number of mode groups propagating.