500 MHz SFP-board (v4)

This is the fourth version of an interface board to Small Form Factor Pluggable optical transcievers (SFPs) with a bandwidth of >500 MHz. These are useful for various time/frequency experiments, with a measured frequency stability of <1e-13 @ 1s (in 0.5 or 5 Hz bandwidth) - perhaps slightly depending on what SFP is used. The SFP allows sending the signal along a single-mode fiber for 1-100 km easily.

ADT2-1T converts to and from differential signals while LMH6702 op-amps provide 3 dB gain. There are parallel outputs on the RX pins. The current-draw on +3V3 by the SFP is quite high - usually requiring heat-sinking on the voltage-regulator

KiCad files available on request.

3 thoughts on “500 MHz SFP-board (v4)”

  1. Hi Anders - this is great thanks! Just wondering, in your experience can I modulate the SFP's with analog? I'm wondering if the (possibly) built in limiting amplifiers will mess with that.

    1. Hi, you can drive the TX+/TX- pins (or just the TX+ and ground TX-) with an analog sine-wave, but the SFP will internally run this through a comparator and produce either '1' or '0' as optical output. I think the 1 Gbit spec has 'raw' bits at 1.25 Gbps (so one bit is 800ps) and allows for 5 consecutive '0's or '1's so the lower frequency limit in theory is 125MHz. In practice SFPs work at much lower frequencies like 1-10 MHz also - the real lower limit might be some 100s of kHz.

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