New electronic technique promises to double optical fiber communications reach
A new method of processing signals via fiber optic cables could vastly increase the distance at which error-free data is transmitted via submarine cables without additional signal amplification. As the technique is capable of correcting corrupted or distorted data being transmitted, it may also assist in increasing the capacity of all optical fiber communications.
With demand for internet connectivity running at an all time high – and only increasing – the fiber optic cables over which much of the data flows draw ever-closer to reaching capacity. Short of laying more cables, growing demand is being increasingly met by boosting the number of available frequency channels on which the data, in the form of encoded light signals, is transmitted. This is often achieved using a variety of compression and error-correction techniques, as well as employing methods designed to overcome nonlinearity in long lengths of optical fiber.
Unfortunately, given that many of these techniques are reaching the limit of their capaabilities to transmit and receive light without adjacent light signal overlap and subsequent interference, data is often received with distortion errors.
To address this problem, researchers from University College London (UCL) have created a way of avoiding such interference by using a set of frequencies that are coded using amplitude, phase, and frequency to create an exceptionally large-capacity, high-quality optical signal.
In detail, the research team used a laser to generate the optical carrier and passed this through a comb generator to form seven equidistantly-spaced, frequency locked signals in the form of Quadrature Amplitude Modulation (QAM) – specifically a 16QAM super-channel. This super-channel signal was then introduced into one end of a fiber optic cable and captured at the other end with a high-speed super-receiver. Employing a range of new signal processing techniques specifically developed by the researchers, reception of all the channels was received intact and without error.