Abstract: The variable optical attenuator varies the angle and distance of coupling between two fiber ends by moving the end of one of the fibers along a circular arc passing through the end of the other fiber. It comprises a rectangular block 3 to support said fibers 1 and 2, having a slit 6 through its end, running parallel to its broad surfaces and dividing the block into two branches 7, 8, a cylindrical through hole 9 traversing one of the branches 7 substantially in line with the inside end of the slit and opened on the side of the supporting surface 4 of the block to establish the coupling zone between the fibers afixed to said surface, and driving and control means 20, 25 for swivelling the branch 7 carrying one of the fibers, which means act substantially on the free end of said branch 7.