OptaSense is a platform that is attached to one end of a single-mode fibre-optic cable (which carries a single lightwave with a large bandwidth) turning the cable into an array of acoustic sensors
Distributed sensor arrays are not unique, but this technology differs in that it does not require additional sensors such as strain gauges attached along the length of the cable.
The sensor employs optical time domain reflectometry (OTDR) to continuously monitor the length of existing or installed cable to detect, locate and categorise security breaches every 10m over a 40km length of optical fibre. Signal processing software then analyses the acoustic signals picked up along the cable to determine whether there has been a security breach.
Because the signal is extracted from each 10m section of fibre it is unaffected by the acoustic disturbance on any other sections. When a security breach is recognised its location is relayed to an operator on a map, plan or aerial photograph.
According to Sensoptics, a length of cable buried in 30cm of damp clay can detect a man running from 10m away and a car travelling on an uneven surface at 30mph from 50m away.
The system is considered particularly well suited to long-line security applications such as border and perimeter security as well as cable and pipeline protection. For border security, anybody climbing, cutting, digging or tunnelling near the fence will generate small vibrations in the ground, which disturb the fibre and cause an alarm to be raised.
OptaSense has its origins in a similar system called Cobalt, which was developed by Andrew Lewis and his colleagues at Sensoptics. Cobalt itself was born out of a project undertaken by Sensoptics to detect nearby excavation equipment to protect telecommunications giant AT&T’s fibre-optic cables from accidental damage. Sensoptics realised that excavation vehicles have a unique acoustic signature and that acoustic signatures could be applied to anything that makes contact with the ground.
In its current incarnation as OptaSense, Qinetiq has supplied the device with technology to improve the categorisation of alarms. Previously, Cobalt’s level of classification fell into three categories: human, vehicle and unknown.
‘Imagine converting a fibre-optic cable into a microphone every 10m,’ said Magnus McEwen-King, Qinetiq Ventures investment director. ‘That microphone picks up a lot of noise and you end up with enormous amounts of acoustic data which needs to be analysed.
‘We’re enhancing the product by adding our advanced detection classification and localisation capabilities that have been born out of decades of looking at acoustic signatures and pattern recognition in maritime environments.
‘We’re marrying a technology that gives us an acoustic signature with Qinetiq’s signature pattern recognition capabilities. This means that OptaSense can tell if an animal or a person, a large or small vehicle or even a tracked vehicle, triggers the signal. This level of discrimination makes the product attractive to a host of industries with particular security requirements.’
‘Telecoms companies, for example, are concerned about plant digging up their underground cables. Similarly, there are only so many ways in which a manhole cover can be removed to access ducting and we can code the acoustic signatures and set the variables to trigger an alarm.’
Qinetiq and Sensoptics are now engaged in an exclusive distribution and joint development agreement, with Qinetiq marketing and promoting the technology. The company will also act as the distribution channel for the product. The agreement does not cover US government applications, which is subject to separate arrangements Sensoptics has with AT&T.
According to McEwen-King, there has so far been an enormous amount of interest in the technology.
‘We’ve had rail, telecoms, security and pipeline companies showing an interest. They all have two things in common: distributed infrastructure which is prohibitively expensive, plus most of them have some sort of fibre in the ground already. One of OptaSense’s unique features is its ability to use existing fibre, which means the minimal installation disruption for the customer.’