SIGNALANORDNING FOER FELLOKALISERING I ETT DIGITALOPTISKT OEVERFOERINGSSYSTEM

摘要

A fault location arrangement for a digital optical transmission system employing repeaters (2) has at each repeater an opto-electrical converter (55) and an electro-optical converter (5). The output of the opto-electrical converter (55) is fed via an AGC amplifier (57) and a regenerator (63) to a modulator (200) which comprises a two pole two way switch (40), a single pole two way switch (41) and two current sources (51,52). The two pole switch (40) is controlled by the regenerated data while the single pole switch (41) is controlled by a fault location signal (F2). The arrangement is such that fault information is transmitted by amplitude modulation of the digital signal but that the average power applied to the electro-optical converter (5) remains constant. Hence the amplitude modulation does not cause a varying dissipation in the converter (5) and hence reduces the possibility of variation of the wavelength emitted by the converter (5).