Simultaneous Sensing of Refractive Index and Temperature With Supermode Interference

Abstract

In general, a sensor is used to monitor a single parameter only, and in many cases, a reference sensor is necessary to compensate the effect of temperature. Here, we demonstrate that a single supermode interferometer is capable of monitoring two parameters simultaneously. Said interferometer was fabricated with a segment of strongly coupled multicore fiber fusion spliced at the end of a standard single mode fiber. The free end of the multicore fiber was flat, thus, it behaved as a low reflectivity mirror whose reflection depended on the external refractive index. The reflection spectrum of our supermode interferometer consisted of well-defined periodic maxima and minima whose values and position varied when the interferometer was exposed to refractive index and temperature changes. In the Fourier domain, the changes of the interference pattern can be decoded easily. We demonstrate that the supermode interferometer here proposed can be useful to measure the thermo-optic coefficient of a sample. An important advantage of the device reported here is that the length of the multicore fiber is not determinant on the performance of the sensor. In addition, the device can be reused multiple times.

Dual-Parameter Sensing With a Single Supermode Interferometer

“…The cross section of the multicore fiber (MCF) used to fabricate our interferometer; its structure and interrogation are shown in Figure 1. The MCF has been described in more detail in (Amorebieta et al, 2019;Flores-Bravo et al, 2021a). To assemble the interferometer, the multicore fiber was fusion spliced at the distal end of a conventional single mode fiber (SMF).…”

“…To assemble the interferometer, the multicore fiber was fusion spliced at the distal end of a conventional single mode fiber (SMF). After that, the MCF was cleaved at a length L. As demonstrated in (Flores-Bravo et al, 2021a), the length of the MCF is not critical in the sensitivity of the interferometer when it is used for refractive index and temperature sensing. Thus, we chose L = 3.7 cm.…”

“…The working mechanism of the SMF-MCF structure has also been discussed in (Flores-Bravo et al, 2021a) with certain detail. The fundamental SMF mode excites two supermodes in the MCF whose profiles are shown in Figure 1B.…”

“…In this work, we report advances on our previously reported index-temperature multicore fiber interferometer (Flores-Bravo et al, 2021a). We have investigated analytically and experimentally the performance of our dual-parameter sensor in a broader refractive index range.…”

A novel approach to Manufacture a Micro-Structured Surface Plasmon Resonance Multiparameter Sensor based on Inkjet 3D Printing for Simultaneous Measurements of Refractive Index and Temperature

“…In literature are present numerous experimental configurations that performs this kind of measurements, like the ones based on interferometers [3][4][5], no-core optical fibers [6,7], fiber Bragg and long period gratings [8][9][10], and many others [11][12][13][14]. Among all the others, Surface Plasmon Resonance (SPR) is often utilized as physical phenomenon to measure both refractive index and temperature at the same time [15][16][17][18].…”