The device (1') of the invention comprises a clamp (10') and a ring (11) adapted to be screwed to a connector (2) to form a stress relief removably attached to the rear of the connector. In accordance with the invention, the clamp (11') has two parts: a rear part (102") forming a receptacle and a front part (102') which is open, having a "C" shape. The material of the clamp (10') is a composite material having elastic properties. By compressing it, the branches of the "C" can be moved closer together and the clamp (10') inserted in or removed from the ring (11). The clamp (11') also includes pegs (105) providing insertion abutments, preventing withdrawal of the ring (11). The clamp (10') can be straight or angled.