Investigating the effect of modulation depth of refractive index in cascaded FBGs for dual sensing of strain and temperature

• Published in: Optical and quantum electronics 2024-03, Vol.56 (5), Article 729
• Main Authors: Sahota, Jasjot Kaur, Dhawan, Divya, Gupta, Neena
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Computer Communication Networks; Electrical Engineering; Lasers; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy
• ISSN: 1572-817X; 1572-817X
• DOI: 10.1007/s11082-024-06446-z

Simultaneous measurement of strain and temperature is crucial for various applications that operate in diverse environments. Fiber Bragg gratings, known for their sensitivity to both strain and temperature, can serve as effective sensors for such simultaneous measurements. However, achieving discrimination between strain and temperature in FBG sensors requires the incorporation of a distinct mechanism in their design. This present a novel approach to dual sensing by exploring the impact of modulation depth of refractive index in cascaded FBGs. Modulation depth of refractive index is a significant spectral parameter of FBGs, influencing the grating’s strength. By cascading two gratings with different modulation depths, the reflection spectrum exhibits two peaks, and their amplitudes are influenced by the modulation depth. Notably, the proposed sensor design eliminates the need for complicated packaging, which is often time-consuming and expensive. The study includes a simulation analysis of the proposed sensor, consisting of two FBGs with distinct modulation depths of refractive index. This technique demonstrates a linear variation in both Bragg wavelength and normalized peak difference (M) in response to changes in strain and temperature. The obtained strain and temperature sensitivities in this study were 1.19 pm/με and 11.4 pm/°C, respectively.