ENVIRONMENT
FEATURE
can be used for continuous sensing over a 524km live network aerial fibre wound around high-voltage power cables suspended from outdoor poles. The field trial, using an aerial cable
between the Swedish cities of Gothenburg and Karlstad, showed that coherent transceivers could potentially be used to perform both environmental and network sensing using existing aerial fibres. The researchers continuously monitored a 524-km length of aerial fibre in Sweden for 70 hours using time-of-flight measurements. They correlated the sensing measurements with temperatures acquired from stations along the network link. The analysis revealed strong oscillations driven by polarisation changes over 50Hz, likely from the Faraday effect induced by the spun fibre. They demonstrated polarisation sensing of various wind conditions by filtering out the low-frequency portion of these polarisation changes. The key challenges with using existing infrastructure is that anything integrated
‘We can detect ocean waves, so it is plausible that one day we will be able to detect tsunamis’
www.electrooptics.com | @electrooptics
onto the sensor line card has to be compatible with ASIC architectures, which is vastly different from the offline Python/ Matlab implementation that is possible within the fibre sensing field. The current transceiver prototype is a
scaled down system, says Mazur, which allowed the team to understand the algorithms that can be used to do fibre sensing that are compatible and compatible with ASIC infrastructures. The result is that the current transceiver was not built to be the highest performing or have highest sensitivity. Signal-to-noise ratios are much lower, and the effective number of bits they have access to “would make everyone in the fibre sensing field run far, far away”, said Mazur. “We’re not trying to beat dedicated
sensors, we’re trying to create a complementary technique that works well with telecommunications,” he added. The FPGA-based coherent system has a digital signalling processing (DSP) clock rate of 125MHz, the same order of magnitude as an ASIC system. It has eight parallel lanes, and it is completely pilot- based, where all of the DSP blocks are updated every clock cycle. Previous examples of fibre-sensing using existing networks have focused on subsea cables, which provide more favourable
Mikael Mazur at Nokia Bell Labs is working is developing coherent transceivers for environmental sensing that can be implemented in existing telecom networks
conditions than the aerial site above the tree line used in this field trial. Mazur noted: “It is a very exposed environment, which is why we wanted to look at this link. Subsea systems are great for sensing. It’s a perfect environment because it’s so stable. This is probably the polar opposite.” However, Mazur pointed out that because
the frequency ranges for environmental sensing are typically very different to the frequency ranges induced in telecommunication systems, as long as the data can be interpreted appropriately, the use of transceivers for environmental sensing show much promise. “We are just scratching the surface of
potential applications and will continue to perform field trials over various networks in different environments,” said Mazur. “Our goal is to better understand how this sensor can be used in future smart cities to improve the resilience of both communication systems and infrastructure, while getting a better understanding of the environment around us. We are also actively looking at algorithms for real-time analytics and autonomous decision-making based on
May 2023 Electro Optics 21
g
Nokia Bell labs
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42
