Update: first production batch being tested in the lab 2020-12-17:
By popular demand, I've worked with Aivon to put my simple 'SFP2SMA' board (https://github.com/aewallin/SFP2SMA_2018.03) in a box, using an external Meanwell (+12V, -12V, +5V) PSU with a 5-pin DIN8 plug (model GP25A13D-R1B, Digikey 1866-1826-ND). The board can be used for simple frequency-transfer experiments together with almost any SFP-transciever. The TX SMA-connector is an input, and applies the waveform to the TX-pins of the SPF, producing modulated optical output. The dual RX SMA-connectors are driven by the SFP RX-pins, with some gain applied to produce around +10 dBm square-wave into a 50R load.
The front panel has three SFP status-LEDs: TX-fault (I've never seen this, but apparently the SFP should report if the TX-laser fails), RX LOS (loss of signal, active if you unplug the fiber), and mod_abs (module absent, active if no SFP is plugged)
After some adjustments to gains and component values the frequency-response is flat within 3 dB out to ca 400 MHz, and the ADEV looks reasonable at ca 1e-13/tau(s) (red datapoints in the plot below). These measurements were done with a CWDM SFP and a 2m single-mode loopback-fiber.
The box is a Hammond 1455L1201(120 mm x 103 mm x 31 mm), with custom front and back panels.
A simple SFP loopback board that loops back any received signal on the SFP RX-pins to the TX-pins. There's a voltage divider probing the signals, and an ONET1191P limiting amplifier provides amplified differential outputs, for probing the signal going through the SFP.
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