Gasket with long term sealing capacity

Gasket (G) for sealing an assembly of two tubes (11, 12) each comprising an extremity with a seating surface, the gasket (G) comprising a sealing portion with two opposite faces (21 A, 21 B), each being arranged to contact a respective seating surface, the sealing portion comprising at least a compressible portion (21), characterized in that the gasket (G) comprises an optical fiber (22) comprising a sensing portion at least partially enclosed in the compressible portion (21) and arranged to detect a compression force applied by the tube assembly to the compressible portion (21) via the opposite faces (21 A, 21 B),