A simple but accurate technique of predicting radial variation of pump and signal intensities in erbium-doped graded index fiber amplifier for propagation of first higher order mode

An optically pumped doped fiber amplifier has emerged as an important device for providing broadband amplification in case of multi-channel optical signals in long-haul communication systems. In this context, dual mode graded index fiber is finding application in all optical technology. So it is needed to prescribe accurately the first order modal field in the doped fiber, both for the pump and the signal as well and it is also equally important to study their variations with the distance. Employing the simple but accurate power series expression of first higher order modal field for graded index fiber, we predict the variation of modal intensity with the radial distance from the axis of the fiber, both for pump and signal fields. Taking step and parabolic index fibers of some typical V values as examples, we show that our estimation matches excellently with the exact results. Our formalism involves little computations in the process of evaluation of the concerned parameters. Such simple but accurate analysis will be beneficial for the system engineers.