Recently, IIT Madras researchers revealed that power transmission cables could be monitored using Raman thermometry applied to the fibre optic cable. The significant discovery involved the use of optical fibres already present in power cables for establishing optical communication. This article further delves into the details of this technological development and its potential benefits.
Raman Thermometry Explained
Raman thermometry is a technique used to determine the local temperature in microelectronics systems, utilizing the Raman scattering phenomena. When light is scattered off an object such as a molecule, two bands are seen with frequencies higher and lower than the original light, known as the Stokes and anti-Stokes bands. By comparing the relative intensity of these two bands, the object’s temperature can be estimated.
The anti-Stokes component of Raman scattering is heavily influenced by the material’s temperature. Therefore, by measuring the intensity of the anti-Stokes scattered light, we can gauge the temperature. As current flows through a conductor, a temperature rise occurs due to the Joule heating effect, which also implies that the power cables heat up as current traverses them.
The Optical Fibre Technique
Temperature measurements of wires aren’t concentrated on one location. Instead, an optical fibre is used for distributed measurements. To achieve this, a pulse of light is launched into the optical fibre, and the backscattered radiation is observed.
Optical fibres consist of high-quality composite glass/quartz fibres. Each fibre includes a denser core and rarer cladding. When a light signal is directed at one end of the fibre at a suitable angle, it undergoes repeated total internal reflections along the fibre length, eventually emerging at the other end. The time of flight of the backscattered radiation gives an estimate of the distance from where the light is backscattered.
Significance of Technique
The Raman thermometry technique’s use is instrumental in obtaining real temperature measurements over tens of kilometres. Unlike alternative methods such as using a thermal camera, which can be cumbersome, the method devised by the IIT Madras team is both economical and provides real-time information.
About the Raman Effect
The Raman Effect, or Raman Scattering, a phenomenon discovered by physicist Sir Chandrasekhara Venkata Raman in 1928, plays a crucial role in the application of this new technology. The Raman Effect concerns a change in the wavelength of light occurring when a light beam is deflected by molecules. A small fraction of this scattered light emerges in directions other than that of the incident beam, with wavelengths differing from the incident light. This variation is attributed to the Raman Effect. In 1930, Sir Raman was awarded the Nobel Prize for this monumental discovery, marking India’s first Nobel Prize in the Science field.
