26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Field Validation of Laser-Written Fibre Bragg Grating Humidity Sensors in a Wastewater Odour Control Unit

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral ANZOS | Photonics and Optics (ANZCOP)

Speaker

Dr Martin Ams (Macquarie University)

Description

Many industrial environments remain challenging for optical humidity sensing due to prolonged exposure to high humidity, corrosive gases, high temperatures, or contamination. We present a field validation of optical fibre Bragg grating (FBG) temperature and humidity sensors deployed for continuous psychrometric monitoring within an operational activated-carbon wastewater odour control unit (OCU), a particularly harsh environment characterised by chemically aggressive and moisture-laden conditions. The sensors were fabricated using a laser-writing technique that involves directly inscribing an FBG through the commercial polyimide fibre coating, eliminating post-processing or recoating steps while retaining the mechanical robustness of the original fibre.

Optical fibre sensors were installed at representative process locations within the odour control unit ductwork and adjacent plant room environment. The passive all-fibre sensing approach requires no local power or electronic components at the measurement locations while providing simultaneous measurements of temperature and relative humidity, enabling calculation of dew-point margin (DPM), a key parameter governing condensation risk in wastewater infrastructure.

The sensor network captured pronounced diurnal and weather-driven psychrometric variations over seven months of continuous operation. Median DPM in the untreated foul air was only 1.7$~^\circ$C, indicating operation close to condensation, while following activated-carbon treatment the DPM increased to 10.2$~^\circ$C, demonstrating markedly lower condensation potential. Optical measurements further revealed that ambient weather strongly influenced internal psychrometric conditions.

The results demonstrate the capability of passive laser-written FBG temperature and humidity sensors to provide stable, maintenance-free, long-term monitoring in an exceptionally aggressive industrial environment. Beyond wastewater applications, the work highlights the potential of passive fibre-optic psychrometric sensing for environmental monitoring and process control wherever reliable measurements are required in humid, corrosive, or otherwise hostile environments.