Collaborative research by City, University of London and the Indian Institute of Science is using advanced photonics to detect contamination in India’s watercourses. As Isabella Kaminski reports, this pioneering work could have widespread benefits for India and beyond.

The team has an excellent pedigree for the research, which is important because this is a multidisciplinary job requiring a wide variety of skills and expertise. Professor Rahman of City’s School of Mathematics, Computer Science & Engineering is the world’s leading academic in photonics modelling. Since receiving his BSc and MSc degrees in Electrical Engineering with distinction from Bangladesh University of Engineering and Technology during the 1970s, he has published more than 500 papers, received over £10 million in research funds and coordinated numerous funded projects across India and other countries.

His latest work has focused on the development of the next generation of optical sensors using nanotechnology, such as microstructured optical fibres, nanofibres, silicon slot guides and microresonators. Last year he was shortlisted for the prestigious Newton Prize [see boxed text opposite] for work on sensor technology in Malaysia.

Professor Asokan leads the optical sensor research group at the Indian Institute of Science in Bangalore, which has special expertise in nanotechnology, material characterisation and computing and a very active photonics group spread over many departments. He is the founder of, a water treatment company in India spun off his academic department, so he brings direct and relevant industrial experience to the consortium.

They will work alongside co-investigator Professor Kenneth Grattan OBE FREng, George Daniels Professor of Scientific Instrumentation at the Royal Academy of Engineering and Dean of the City Graduate School, who has a significant international reputation in the field of sensors and instrumentation and has published several papers on water quality monitoring.

Together the team has worked with an impressive array of organisations including Serco, Network Rail, Home Office, UK Border Agency, Arup, Fiat, BAE Systems and Amey Consulting. They met in India in May and will work together for at least the next three years. “Work on some parts has already begun,” says Professor Asokan. “It will give us a good opportunity to add the work of two complementary groups and make a very successful project.”

Professor Rahman explains that the first part of the project is basic optical design. That is, designing optical sensors – sensors that convert light rays into electronic signals – that can detect specific substances in water and relay them back to a central control point.

The sensors will use sophisticated specialist coated fibre Bragg grating technologies (a special type of reflector constructed in a short segment of optical fibre that only reflects particular wavelengths of light), as well as exploring the potential for nanofibres and plasmonic evanescent sensing to detect a range of different contaminants, be it physical, chemical or biological. “For each specific thing we are sensing, we need to work with, say, chemists or biologists in that area”, explains Professor Rahman. “But ultimately we want to see how the presence of something we want to detect changes the optical characteristics of our device.”

The next step is to develop integrated systems that enable the information from a whole series of sensors to be relayed to a central control point without being confused. The idea is that many sensors will be ‘multiplexed’ or strung along a single optical fibre sending ‘guided wave’ signals back to a central control unit. This could vary from a couple of sensors to potentially hundreds; the team has already used a network of more than 330 optical sensors in single acoustic sensing system.

“I could have ten different sensors – one for chromium, one for arsenic, et cetera – on the same sections of an optical fibre,” says Professor Rahman. “We’re talking millimetres long. Each is sensing a different contaminant, but using guided wave photonics, each of these uses a different wavelength, so the signals don’t interact and you can tell which one is sensing the presence of the target you want to detect.”

Professor Rahman says the sensors will be a significant improvement on existing systems for monitoring water quality, which usually rely on electrical feedback or chemical and biological processing. They will be small, light and fast, relaying reliable information directly to the control panel. Chemical and biological analysis can take hours or days, may require a larger sample and have a potentially larger error rate, while electronic cables can be dangerous to use in some places, such as coal or gas fields. This means problems in water supplies can be spotted much quicker, even in remote villages, providing support when and where it is most acutely needed. It also satisfies growing demand from citizens for real-time information about the water they are drinking.

Once the design work has been done, the sensors will be tested in the lab. The Indian Institute of Science’s Department of Civil Engineering has an advanced hydrology laboratory with a complex network of water supply systems where particular substances can be injected and monitored. The team hopes to be testing its sensors there in a couple of years’ time.