The device (1) for optical measurement, particularly for extracorporeal blood circuits, comprises a tubular element (2) having a first end connector (3) and a second end connector (4) connectable, respectively, to a first tube (5) and to a second tube (6) for subjecting a work fluid through the tubular element itself, and an intermediate portion (7) extending between the first end connector (3) and the second end connector (4) and suitable for subjecting the fluid to a non- invasive measurement of one or more parameters, where the tubular element (2) 10 comprises two pieces distinct to one another, of which a first tubular portion (2a) and a second portion (2b) bearing a protruding element (8) suitable to be inserted into a corresponding mating recess provided on a medical apparatus for activating the optical measurement, where the second portion (2b) is suitable to cooperate with the first tubular portion (2a) for fixing the position of the protruding element (8) with respect to the first tubular portion itself, wherein the first tubular portion (2a) defines both the first and second end connectors (3, 4) and the second portion (2b) is movable with respect to the first tubular portion itself and is applied over both the first tubular portion (2a) and the second tube (6) fitted on it； or wherein the first tubular portion (2a) is of the rigid type and the protruding element (8) is realized with soft material.Le dispositif (1) de mesure optique, en particulier pour circuits sanguins extracorporels, comprend un élément tubulaire (2) ayant un premier raccord d'extrémité (3) et un second raccord d'extrémité (4) pouvant être raccordés, respectivement, à un premier tube (5) et à un second tube (6) pour soumettre un fluide de travail à travers l'élément tubulaire lui-même, et une partie intermédiaire (7) s'étendant entre le premier raccord d'extrémité (3) et le second raccord d'extrémité (4) et approprié pour soumettre le fluide à une mesure non invasive d'un ou de plusieur
