All-Fiber CO2 Sensor Using Hollow Core PCF Operating in the 2 µm Region

Abstract

A realistic implementation of an all-fiber CO2 sensor, using 74 cm of hollow core photonic crystal fiber (HC-PCF) as the cavity for light/gas interaction, has been implemented. It is based on CO2 absorbance in the 2 µm region. The working range is from 2% to 100% CO2 concentration at 1 atm total pressure and the response time obtained was 10 min. Depending on the concentration level, the sensor operates at one of three different wavelengths (2003.5 nm, 1997.0 nm and 1954.5 nm) to maintain a high sensitivity across all the working range.

Laser-Based Trace Gas Detection inside Hollow-Core Fibers: A Review

“…However, later papers on laser spectroscopy inside PBG HCFs suggest that the origin of these fringes is the propagation of higher-order spatial modes which interfere at the output. Similar background signals can be found in many other papers (e.g., Figure 9 shows spectra presented in [ 39 ]), and various ways to suppress them have been proposed. For example, in [ 43 ], the HCF was thermally cycled so that the fringe pattern could be washed out through averaging.…”

Antiresonant Hollow-Core Fiber-Based Dual Gas Sensor for Detection of Methane and Carbon Dioxide in the Near- and Mid-Infrared Regions

“…To date, the experimental results published on hollow-core fiber-assisted sensing of carbon dioxide and methane are mainly focused on utilizing well-known and commercially available hollow-core photonic bandgap fibers. In the gas sensor published in [19] a HC-PBGF operating in the vicinity of 2 µm wavelength range was used to detect CO 2 , while accessing very strong transitions of this particular gas in the NIR band. That configuration reached a minimum detectable concentration of CO 2 equal to 2%, which is far above the ambient level of this gas (~400 ppmv).…”

“…The result is almost 140 times worse than that achieved in our sensor, which operated in the wavelength range of 1.574 um, where CO 2 has approximately 80 times lower absorption in comparison with the 2-µm band. In [19], the main limiting factor for the performance of the sensor was the type of the fiber used as the low-volume gas cell (in particular its guidance mechanism) and its relatively short length, which resulted in a strong impact of intermodal interference. A multimode characteristic of the HC-PBGFs is the main source of the background noise, which significantly limits the performance of such gas sensors.…”

“…First demonstration of the implementation of HCFs into laser-based gas sensors was relying on the use of photonic bandgap HCFs (HC-PBGFs) and enabled detection of various gas molecules in the NIR and MIR [19,20]. Unfortunately, their performance was strongly limited by the multimode nature of the fibers and relatively high loss in the MIR [20,21].…”

A Review of Methods for Fibre-Optic Distributed Chemical Sensing

“…For distributed measurements, the backscattered intensity profile is measured when using a transmission wavelength within the absorption spectrum of the relevant substance. A local power drop represents the presence of the sample, and the change amount is related to the concentration [49]. This method requires a direct interaction between the light and the analyte, and was performed in different types of fibres modified by tapering or etching of the cladding to ensure that a component of the evanescent wave propagates in free space.…”