While advances have been made in core optical fibre networks, they often terminate in cabinets far from the end consumers. The so called 'last mile' which connects households to the global Internet via the cabinet, is still almost exclusively built with copper cables as the optical receiver needed to read fibre-optic signals is too expensive to have in every home.
Lead researcher, Dr Sezer Erkilinc, said: "We have designed a simplified optical receiver that could be mass-produced cheaply while maintaining the quality of the optical signal. The average data transmission rates of copper cables connecting homes today are about 300Mbit/s and will soon become a bottleneck in keeping up with data demands, which will likely reach about 5 to 10Gbit/s by 2025. Our technology can support speeds up to 10Gbit/s."
The scientists say they have developed a way to solve the 'last mile problem' with fibre-to-the-home (FTTH) broadband technology. They claim to have improved the sensitivity and network reach of the optical receiver compared to existing technology. Once commercialised, it will lower the cost of installing and maintaining active components between the central cabinet and homes.
A major factor limiting the uptake of FTTH is the overall cost associated with laying optical fibre cables to each household and providing affordable optical receivers to connect them to the network. The sensitive coherent optical receivers used in core networks are desirable but are also complex, which makes them expensive to manufacture. Using such receivers in homes increases the cost of FTTH beyond the current copper based solutions.
The UCL optical receiver is said to retain many of the advantages of the ones typically used in core networks, but is smaller and contains around 75 to 80% fewer components, lowering the cost of manufacture and maintenance.
Co-author, Dr Seb Savory, explained: "We achieved this by applying a combination of two techniques. First a coding technique often used in wireless communications was used to enable the receiver to be insensitive to the polarisation of the incoming signals. Second we deliberately offset the receiver laser from the transmitter laser with the additional benefit that this allows the same single optical fibre to be used for both upstream and downstream data."
The researchers are now investigating the laser stability of the receiver, which is an important step to building a commercial prototype of the system.
