A sensor suitable for optical turbidity measurements is described. The sensor is suitable for use in a water-bearing domestic electrical appliance (e.g. washing machine or dishwasher) and allows the temperature dependence of the turbidity measurements obtained by means of a first light detector to be compensated for. To this end, the sensor implements, in addition to a turbidity-measuring path along which a measuring-light beam is sent through a measuring space containing the turbid medium to a first light detector, a reference measuring path along which a reference light beam is transported to a second light detector which is thermally coupled with the first light detector. A heat-equalizing element can ensure that any temperature differences between the two light detectors are minimized. Both light-measuring paths can run in some regions inside the same solid-material light-conducting structure.