Modal dispersion, pulse broadening and maximum transmission rate in GRIN optical fibers encompass a central dip in the core index profile

• Intermodal and intramodal dispersions in optical fiber limits the pulse propagation.
• Interferometry is proposed as an inductive methodology for dispersion analysis.
• The method is applied on GRIN optical fiber has central dip in core profile.
• The equation needed to describe the effect of the dip on modal dispersions is derived.

Intermodal and intramodal dispersions signify one of the problems in graded-index multi-mode optical fibers (GRIN) used for LAN communication systems and for sensing applications. A central index dip (depression) in the profile of core refractive-index may occur due to the CVD fabrication processes. The index dip may also be intentionally designed to broaden the fundamental mode field profile toward a plateau-like distribution, which have advantages for fiber–source connections, fiber amplifiers and self-imaging applications. Effect of core central index dip on the propagation parameters of GRIN fiber, such as intermodal dispersion, intramodal dispersion and root-mean-square broadening, is investigated. The conventional methods usually study optical signal propagation in optical fiber in terms of mode characteristics and the number of modes, but in this work multiple-beam Fizeau interferometry is proposed as an inductive but alternative methodology to afford a radial approach to determine dispersion, pulse broadening and maximum transmission rate in GRIN optical fiber having a central index dip.