AUTHOR=Savović Svetislav , Djordjevich Alexandar , Drljača Branko , Simović Ana , Min Rui 

TITLE=Calculation of the Coupling Coefficient in Step-Index Multimode Polymer Optical Fibers Based on the Far-Field Measurements

JOURNAL=Frontiers in Physics

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2022.927907

DOI=10.3389/fphy.2022.927907

ISSN=2296-424X

ABSTRACT=<p>Using the power flow equation (PFE), this article investigates mode coupling in step-index (SI) multimode (MM) polymer optical fiber (POF). This equation’s coupling coefficient was initially fine-tuned so that it could appropriately reconstruct previously recorded far-field (FF) power distributions. The equilibrium mode distribution (EMD) and steady-state distribution (SSD) in the SI MM POF were found to be obtained at lengths <italic>L</italic><sub><italic>c</italic></sub> = 15 m and <italic>z</italic><sub><italic>s</italic></sub> = 41 m, respectively. These lengths are substantially shorter than their glass optical fiber counterparts. Such characterization of the investigated POF can be used in its employment as a part of the communication or sensory system. Namely, the POF’s bandwidth is inverse linear function of fiber length (<italic>z</italic><sup>−1</sup>) below the coupling length <italic>L</italic><sub><italic>c</italic></sub>. However, it has a <italic>z</italic><sup>−1/2</sup> dependence beyond this equilibrium length. Thus, the shorter the coupling length <italic>L</italic><sub><italic>c</italic></sub>, the sooner transition to the regime of slower bandwidth decrease occurs. It is also important to be able to determine a modal distribution at a certain length of the POF employed as a part of optical fiber sensory system.</p>