Raman Distributed Temperature Sensor with Optical Dynamic Difference Compensation and Visual Localization Technology for Tunnel Fire Detection

Abstract

The field of tunnel fire detection requires a Raman distributed temperature sensor (RDTS) with high-accuracy and visual localization. A novel temperature demodulation method to improve the temperature measurement accuracy of the RDTS systems is presented. This method is based on the optical dynamic difference compensation algorithm, which can eliminate the optical power fluctuation. In addition, the visual localization technology is presented by using the longitudinal lining model (LLM) of a three-dimensional (3D) temperature display, which enhances the engineering application of RDTS in tunnel fire detection. Experimental results indicate that the temperature measurement accuracy is optimized from 7.0 °C to 1.9 °C at the sensing distance of 18.27 km by using the presented method. We provide a solution for temperature field monitoring as well as fire visual localization of the tunnel through RDTS systems.

Deformation measurement within adhesive bonds of aluminium and CFRP using advanced fibre optic sensors

“…The Raman scattering is an inelastic exchange of energy between a photon and solid matter which can be utilised to detect changes in temperature within an optical fibre. Raman sensors are mainly used as temperature monitoring devices in fixed structures such as tunnels [7,8] and is able to detect temperature variations as small as 0.1°C [5]. Rayleigh scattering describes an elastic effect, in optical fibres it can be caused by variations in density or the refractive index.…”

A Review of Modern CMOS Transimpedance Amplifiers for OTDR Applications

“…Unfortunately, conversely from classical OTDR, where recently several ASIC have been reported (see [14,18]) and special OTDR-specific TIAs have been considered [12], no similar works are known to the authors for Raman OTDR applications. Typically, for Raman OTDR applications a laboratory equipment with APD and data acquisition cards are employed (see [19,24]). As no details on the built-in APD or external TIA are provided, very little information can be extracted on Raman OTDR requirements for TIAs.…”

“…The major difference is that as high spatial resolution for distributed temperature sensing is typically not required, the TIA for Raman OTDR application may need significantly lower bandwidth (on the order of several to tens of MHz) when compared to the specification in Table 1. The work [24] reported on the amplifier bandwidth of 50 MHz, while a TIA with only 3 MHz bandwidth was employed in [25].…”

Monitoring a Heatsink Temperature Field Using Raman-Based Distributed Temperature Sensor in a Vacuum and −173 °C Environment

“…In order to compensate for the instability factors in the engineering, a voltage ratio R between the anti-Stokes and Stokes backscattered light beams generated by photoelectric detectors was used, and is shown in Equation (3):R=GasGsKasKs(vasvs)4exp[−(αas−αs)L]exp(−hΔfkT) where Gas and Gs are the electrical characteristic parameters of these two photoelectric detectors, respectively. The attenuation coefficient functions αas(z) and αs(z) can be simplified as constants αas and αs for engineering purposes [18].…”