The invention relates to an optically controllable switching device having a first and second line section, between which an optically controllable switch (T2) is inserted, and having a sensor element (SE). The optically controllable switch (T2) disconnects or connects depending on an optical
switching signal (SB), whether the switch is "on" or "off". The sensor element (SE) comprises a
carrier material (TM) with crystals comprising one or more paramagnetic centers (NV). When irradiated with pump
radiation (LB), the sensor element (SE) emits
fluorescent radiation (FL) which depends on the
magnetic flux density B at the location of the sensor element (SE). A
line current (I LTG) in the first line section of the line (LTG) generates a
magnetic field with a flux density B which, with sufficient
current strength, influences the
fluorescent radiation (FL) from one or more paramagnetic centers (NV). The optically controllable switching device has first means (LWL1, PL1, LIV) for irradiating the one or more paramagnetic centers (NV) with pump
radiation (LB) and second means (LWL2, F1, PD, LIV) for detecting and separating the
fluorescent radiation (FL) and for detecting a measured value
signal which depends on the intensity of the fluorescent
radiation (FL) and / or on the phase shift of the modulation
signal of the temporal profile of the intensity of the fluorescent radiation (FL). The optically controllable switching device has third means (LIV) for generating an optical
switching signal (SB) and for controlling the state of the optically controllable switch (T2) using this optical
switching signal (SB).The optical switching
signal (SB) depends on the intensity of the
fluorescence radiation (FL) and / or on the phase shift of the modulation signal of the temporal course of the intensity of the
fluorescence radiation (FL).