Galvanically isolated and linear transmission of analog current-signals using the optically coupled current–mirror architecture

We describe a novel circuit architecture, the optically coupled current-mirror (OCCM), that allows linear transmission of analog current signals over optical fibers. The OCCM ensures Galvanic isolation between the detector where the current-signals flow, and ground. A remarkable difference compared to other methods used so far for the analog transmission of signals via optical means, is that the input stage of the OCCM, the only one that remains at the detector side, is passive; therefore, it does not require to be powered. This is the most distinctive feature of the OCCM, which opens new opportunities for the realization of multichannel analog links for particle physics experiments and other applications requiring Galvanic isolation and linear transmission with a dynamic range of at least two orders of magnitude. In addition, operation at LAr or LXe temperatures improves the loop-gain by a factor 2: The signal bandwidth, at present about 5 MHz; is expected to increase by at least the same factor by optimizing the gain-bandwidth product of the open-loop amplifier.