Addressed Combined Fiber-Optic Sensors as Key Element of Multisensor Greenhouse Gas Monitoring Systems

Abstract

The design and usage of the addressed combined fiber-optic sensors (ACFOSs) and the multisensory control systems of the greenhouse gas concentration on their basis are investigated herein. The main development trend of the combined fiber-optic sensors (CFOSs), which consists of the fiber Bragg grating (FBG) and the Fabry–Perot resonator (FPR), which are successively formed at the optical fiber end, is highlighted. The use of the addressed fiber Bragg structures (AFBSs) instead of the FBG in the CFOSs not only leads to the significant cheapening of the sensor system due to microwave photonics interrogating methods, but also increasing its metrological characteristics. The structural scheme of the multisensory gas concentration monitoring system is suggested. The suggested scheme allows detecting four types of greenhouse gases (СО2, NO2, CH4 and OX) depending on the material and thickness of the polymer film, which is the FPR sensitive element. The usage of the Karhunen–Loève transform (KLT), which allows separating each component contribution to the reflected spectrum according to its efficiency, is proposed. In the future, this allows determining the gas concentration at the AFBS address frequencies. The estimations show that the ACFOS design in the multisensory system allows measuring the environment temperature in the range of −60…+300 °C with an accuracy of 0.1–0.01 °C, and the gas concentration in the range of 10…90% with an accuracy of 0.1–0.5%.

Microwave photonic dual-FBG differential flowmeter: concept design

“…Taking into account the measurement methods developed at the Kazan School of Microwave Photonics [16][17][18] , it is proposed to use either FBG with a phase shift or AFBS in the flowmeters. Since both the former and the latter continue to develop, new and more advanced ways can be found to improve the efficiency of monitoring the flow of liquids, including with a targeted microwave photonic approach using a matrix of sensors located in the cross section of the pipe, which will allow processing not only laminar, but also turbulent currents.…”

Addressed Fiber Bragg Structures: Principles and Applications Overview

“…An attractive solution for simultaneous gas, temperature, and pressure measurement is based on the combination of FBG and a Fabry-Perot resonator (FPR). Such combined fiber-optic sensors (CFOSs) consist of an FPR formed of a thin film at the end face of the optical fiber with FBG near it [45]. The film is made of a polymer, the refractive index of which reversibly changes depending on the gas concentration.…”

“…The usage of AFBS instead of conventional FBG in CFOS has the advantage of simplified interrogation scheme as well as the possibility to include several AFBSs with identical central wavelength and addressable interrogation. The scheme of the addressed combined fiber-optic sensor (ACFOS) incorporating a 2λ-FBG structure is presented in Figure 11 [45]. The thickness of the film h and its material are selected based on the type of gas under test.…”

“…The ACFOS spectrum is a superposition of the AFBS and FPR spectra, therefore it is necessary to separate the FBG and the FPR spectra in order to successfully interrogate the combined sensor, which can be achieved using Karunen-Loeff transform [50]. According to estimations, the sensor system based on ACFOS allows measuring the gas concentration in the range of 10−90% with an error of 0.1−0.5% [45].…”

Development of a Portable and Sensitive CO2 Measurement Device with NDIR Sensor Clusters and Minimizing Water Vapor Impact

“…Optical detection technology can provide great advantages with regards to gas selectivity, accuracy and sensitivity. As a result, it is widely used for environmental CO 2 detection [5,6]. To address global-scale monitoring requirements, probing satellites with spectroscopic techniques have been deployed into space to monitor atmospheric CO 2 concentrations [7][8][9].…”