The invention relates to a segment of pipe-in-pipe pipeline comprising an annulus under reduced pressure sealed and delimited by a metallic internal pipe inserted into a metallic external pipe and provided with a measurement system to determine in a non-intrusive manner the state of the annulus, the measurement system being composed of a first internal emitter/receiver assembly placed inside the annulus and cooperating with means to measure a first physical quantity such as pressure, hygrometry or temperature inside the reduced pressure annulus and a second external emitter/receiver assembly arranged to the exterior of the segment and facing said first assembly.