Speakers
Description
Fiber sensing is a broad concept that defines the capability within optical networks to leverage existing fiber infrastructure for advanced monitoring and control applications. It can encompass monitoring capabilities that measure static fiber/optical signal properties and/or sensing capabilities that detect dynamic changes in optical signal properties due to external perturbations.
Among the sensing solutions is the one provided by coherent transponders, which are no longer merely receivers for data traffic but also powerful sensing devices. Thanks to their integrated digital signal processors (DSPs), these transponders can continuously monitor the physical state of the fiber in real time—without any additional hardware.
The DSP, by analyzing the received transponder symbols, determines the total accumulated Chromatic Dispersion and nonlinearities. In a subsequent step, an algorithm proposed by Nokia Bell Labs exploits the non-commutative property between Chromatic Dispersion and nonlinear effects, converting this data into power versus distance maps. This method is called Tomography and estimates the network topology (fiber types, length of each traversed span, and amplifier types) without requiring prior knowledge of the network infrastructure. This enables operators to quickly update their existing databases or characterize newly acquired network segments.
During this presentation, we will showcase the results of a field trial conducted by Nokia in early February 2026. This trial took place on a multi-vendor network connecting the Scandinavian Peninsula via operators CSC, Sikt, and SUNET. The optical signal connected Tromsø (Norway) to Espoo (Finland) via two different routes, whose characteristics were unknown to the Nokia team, using the Nokia PSE-Vs transponder (SFM6). The optical signal propagated on the C-Band alongside other traffic, with three different wavelengths measured for each route.
Thanks to the results obtained by the proposed Tomography method, we not only provided a quite accurate estimation of the fiber length (with less than 4% error) and a good match for the amplifier types, but the network operators were also able to correct some erroneous database entries, and an error in the path commissioning was detected.
In conclusion, the coherent transponder with its DSP is evolving from a pure transmission component into a multifunctional element that enables real-time network monitoring. This paradigm shift transforms optical networks from simple data pipes into intelligent infrastructures, improving operational efficiency, resilience, and sustainability. As the technology matures, applications like Tomography will play a significant role in building autonomous, AI-native networks that support emerging applications across telecommunications, energy, and smart infrastructure domains.
