Abstract: A referenced optical chain for measuring angle or position, using transmission by optical fibers. The device comprises a measuring head (29) receiving two light waves transported by a supply optical fiber (28); at the measuring head (29), the incident light beams are collimated (33) then intercepted by an assembly comprising a fixed diaphragm (34) and a movable filter (35) intercepting one of the two light waves; this assembly constitutes the measuring system itself; the resultant light signals are then refocussed and coupled to an optical return fiber which transports the signals toward a photodetector. The measurement is linear and the measuring chain is referenced in all of the embodiments of the invention. The device may be used in any application which requires a measurement of angle or position.