The INFN-LNS Fibre optic infrastructure

The INFN-LNS (Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali del Sud) operates two deep-sea cabled infrastructures in Eastern Sicily.The first infrastructure connects a shore laboratory in the port of Catania to two underwater sites in the Gulf of Catania. This connection is made through an electro-optical submarine cable, approximately 25 km long, which hosts 10 optical fibers. At a distance of 20 km from the shore laboratory, the cable splits into two branches via a Y-junction to reach two different cable termination frames: TSN (Test Site North) and TSS (Test Site South), both located at a depth of 2100 m.The second infrastructure is situated 100 km southeast of Portopalo di Capo Passero at a depth of 3500m. The underwater site is connected to the shore laboratory in the harbor of Portopalo via two underwater electro-optical cables. These cables carry 20 and 48 optical fibers, respectively. The second cable, funded by the IDMAR PO-FESR project, was deployed between November 2020 and November 2022. Thanks to a Y-branching unit, the cable is split underwater into two different branches.These two LNS fiber optic infrastructures have hosted several Italian and European projects, including Geoinquire, EMSO-ERIC, IPANEMA/ECCSEL-ERIC, and FOCUS-ERC in Catania; KM3NeT and EMSO in Portopalo di Capo Passero.Specifically, within the FOCUS-ERC and Geoinquire projects, DAS (Distributed Acoustic Sensing) and BOTDR (Brillouin Optical Time Domain Reflectometer) measurements were acquired over a long period.The optical network of the two deep-sea infrastructures and the available assets for geoscience will be described.