Spectral response of Bragg gratings in multimode polymer waveguides

TL;DR

This paper introduces a method to calculate the spectral response of Bragg gratings in complex multimode polymer waveguides, accounting for multiple modes and energy distribution, validated by numerical and experimental comparisons.

Contribution

A novel technique for calculating the multimodal spectral response of Bragg gratings in non-circular waveguides is proposed and demonstrated.

Findings

The Bragg wavelength is influenced by the number of modes and energy distribution.

Numerical calculations match well with measured spectra.

The method effectively models complex multimode waveguide spectra.

Abstract

A means to calculate the multimodal spectral response of Bragg gratings in general non-circular multimode waveguides is proposed. To illustrate the power of the technique, the spectra of two Bragg temperature sensors are numerically calculated in which coupling between 100 modes considered. It is shown how the Bragg wavelength in multimode Bragg grating waveguides is affected by the number of modes and energy distribution among them. Good matching of the simulated spectrum of a multimode Bragg grating on a planar inverted rib waveguide to the measured spectrum is seen.