A tamper seal includes an optical waveguide arranged to guide a propagating light-beam along a propagation direction. First and second portions of the tamper seal are configured to be arranged on first and second parts, respectively, which are movable relative to each other. The first portion has an input coupler arranged to couple incident light into the optical waveguide, and the second portion has at least one output coupler arranged to couple out of the optical waveguide at least partially light guided in the optical waveguide. The input coupler, the optical waveguide, and the output coupler are configured to transmit light from the input coupler to the output coupler. The waveguide is configured to be disruptable and includes a layer having a distinctive appearance that is changed in response to an at least partial disruption of said optical waveguide.