Method and apparatus for combined analogue and digital transmission of an analogue AC measurement signal by means of optical conductor

The invention relates to a method for combined analogue and digital transmission of an analogue AC measuring signal (Sa) by means of an optical fibre, and to a device to carry out this method. According to the invention the analogue AC measuring signal (Sa) is both digitized and combined with a constant direct voltage signal (SR), the digitized AC measuring signal (Sd) and the analog summated signal (SRa) are combined to form a modulation signal and converted to an optical transmission signal (SL), the optical transmission signal is reconverted into a modulation signal in the receiver (6), where the signals (Sa, Sd,SR) are filtered out and the recovered AC measuring signal (Sa) is normalized by the filtered out direct voltage signal (SR). This enables a method for combined analog and digital transmission to be obtained, whereby ageing phenomena of the optical fibre system (2,4,6) can be compensated.