Power Flow in Multimode Graded-Index Microstructured Polymer Optical Fibers

We investigate mode coupling in a multimode graded-index microstructured polymer optical fiber (GI mPOF) with a solid core by solving the time-independent power flow equation (TI PFE). Using launch beams with various radial offsets, it is possible to calculate for such an optical fiber the transients of the modal power distribution, the length L_c at which an equilibrium mode distribution (EMD) is reached, and the length z_s for establishing a steady-state distribution (SSD). In contrast to the conventional GI POF, the GI mPOF explored in this study achieves the EMD at a shorter length L_c. The earlier shift to the phase of slower bandwidth decrease would result from the shorter L_c. These results are helpful for the implementation of multimode GI mPOFs as a part of communications and optical fiber sensory systems.