Multiplexed detection using two serial long period gratings in a Mach-Zehnder interferometer configuration

We report a novel methodology for multiplexed detection in optical fiber sensors by employing two serial long-period fiber gratings (LPGs) arranged in a Mach-Zehnder interferometer-like configuration on the same fiber. This configuration enables simultaneous measurement of multiple parameters by analyzing the interference pattern resulting from the interaction of the LPGs with their surrounding environment. By tracking selected spectral features of the interference fringes and modelling their evolution with simple bivariate polynomial functions, it is possible to infer the temperatures of the two LPGs, which were used as measurand of interest for our proof-of-principle experiment. Experimental results demonstrate high precision (in the order of the instrumental error) and resolution comparable to that of single LPG-based sensors (40 pm, which is 5 × 10 − 4 times the full-width at half-maximum of the LPG peaks). Furthermore, the proposed method is mathematically general and can be easily extended to other types of measurands (e.g. refractive index, strain) and to the analysis of the spectral characteristics of other interferometric systems. In perspective, it offers a pathway towards accurate and robust multi-parameter detection of any measurand or analyte to which LPGs are sensitive, with potential impact in biosensing and other applications where multi-parameter tracking is essential. • Two-parameter multiplexed detection through interference pattern analysis. • Mach-Zehnder configuration with Long-Period Gratings. • Optical fiber sensor designed for multiplexed detection. • Interference pattern deconvolution for high precision multiplexed sensing.