Researchers address frequency interference as Digital Britain takes flight

With government plans for a Digital Britain underway, the amount of internet data is set to increase dramatically and, with it, the potential for frequency interference which could corrupt data files and live 'on demand' tv services. Scientists from the National Physical Laboratory believe they have found an answer. Currently, data transmitted through optical fibres is sent down one of a number of internationally agreed channels operating at very specific optical frequencies. Data providers need to ensure they adhere to these frequencies so that their transmitters never drift close to neighbouring channels, which could cause interference and crosstalk. To check the long term performance of these transmitters, manufacturers need to periodically calibrate these sources using frequency standard equipment. However, the increase in data traffic is likely to lead to channel spacing moving closer together, increasing the demand for more accurate, on site frequency standards technology. Frequency standard systems that are accurate enough for industrial applications have already been developed at NPL, but are generally too complex to be deployed in the field - the higher accuracy frequency standards are usually bulky and need to be operated by trained personnel. They are also not designed for extended operation in industrial environments where there are often high levels of temperature fluctuations and vibration. If the user transmitter frequencies are going to be tested on site at a manufacturer's premises, then the next generation of frequency standard technology needs to be able to operate in industrial environments. The development of 'user friendly' frequency stabilised laser sources is proposed over the next three years in a European Metrology Research Programme (EMRP) project which is being coordinated by NPL. "We envisage an optoelectronic system within a 19in rack that provides an onsite frequency calibration service," said Geoffrey Barwood, lead researcher on the project. "We hope the system will be a turnkey standard for companies to use. If we do want to move to a Digital Britain this type of equipment becomes an essential part of the infrastructure." As well as NPL, the collaboration includes Spain, Denmark, Switzerland, Italy, France, Finland and Germany. The success of the project proposal was, in part, due to the large number of letters of support received from various European companies, government agencies and standards committees emphasising the need for this equipment. "The project is not only vital for the telecommunications and broadcast industries, but also for calibrating frequencies in areas such as aerospace, defence, instrument manufacture, gas sensing, and navigation," said Barwood.