An improved photopolymer coversheet film including no microindentations or micropitting is disclosed. So that the cabinet door can be opened in a simple way from the inside of the switchgear cabinet, the actuating unit of this invention is designed as a Bowden cable, with one end connected to the triggering device via a connecting element and an other end connected with the lock element or the counter-lock element. The optical fiber is poled lengthwise with a non-linearity profile having a period that satisfies a quasi phase matching condition including the first and second frequencies.