An optical fiber mode scrambler adapted to give a determined bending to an optical fiber inserted in the mode scrambler, the mode scrambler having a general extension direction X, the mode scrambler having a morphology adapted to give the optical fiber a direction along X at the entry of the scrambler, and then to bend the fiber to bring the fiber substantially in the X, Y plan in the −X and Y directions, before bringing the fiber in a rotation around the X axis substantially in the Y, Z plan in the anti clockwise direction for one full rotation, and then bending the fiber to bring the fiber substantially in the X, Y plan in the −X and −Y directions, and then bending the fiber to give the optical fiber a direction along X at the exit of the scrambler.