I've been looking into these fiber isolated probes that Lecroy makes (http://teledynelecroy.com/probes/probeseries.aspx?mseries=537), and I'm curious how they're sending the signal over the optical fiber. I was thinking maybe you could make a probe with a sigma-delta converter in it and then send this 1-bit ADC digital signal optically. The manual/datasheet claims however that the signal is carried as FM (note "frequency modulating optical transmitter"). I'm curious how you might design a voltage to frequency converter with high linearity and 60 MHz of modulation bandwidth, if this is how it indeed works.

  • \$\begingroup\$ Speculation, so comment rather than answer: it could be a 1-bit sigma-delta ADC as you suggest, with the output frequency-shift-keying a high frequency (>100 MHz) carrier, or perhaps Manchester encoded. Optical receivers don't deal well with DC and nearly always have a built-in high pass filter. \$\endgroup\$ – pericynthion Sep 9 '17 at 6:56

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