Step-index polymer optical fibers (SI-POFs) are deployed in both sensing and data transmission systems. The optical transmission behavior of these fibers is complex and affected by intrinsic influences like modal dispersion, scattering and attenuation as well as extrinsic influences like the launching condition and the angular sensitivity of the receiver. Since a proper modeling of the transmission behavior is important in order to evaluate the suitability of the fiber for a specific application, we present a novel model for step-index multi-mode fibers (SI-MMFs) which considers all the previously mentioned impacts. Furthermore, the model differentiates scattering and attenuation for propagating rays not only by their propagating angle θ z but also by the skewness θ ϕ . It is therefore possible to distinguish between guided, tunneling and refracted modes. The model uses scatter and attenuation data from previously published measurements of an SI-POF and computes the impulse response of the transmission system which is transferred to the frequency domain to derive the amplitude and phase response. A possible application for SI-POF is the length or strain measurement of the fiber by measuring the phase of a harmonically modulated signal. These sensors rely on a linear relation between the length of the fiber and the phase of the modulated signal. We demonstrate the application of the model by simulating the length measurement error that occurs for these sensors by obtaining the phase response for the corresponding optical transmission system. Furthermore, we will demonstrate the flexibility of the model by varying several influences including the excitation of different mode categories and evaluate the impact on the measurement error. Finally, we compare the simulated length error derived from the model to real data obtained from a cutback measurement. An implementation of the model, which was used for all simulations in this paper, is publicly available.
Novel Model for the Angle and Skewness Dependent Transmission Behavior of Step-Index Polymer Optical Fiber