SFP-board in a box

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.

400+ MHz photodetector with OPA818

One-Inch-Photodetecor in Thorlabs 1" mount. LT3093 negative-rail voltage regulator at the top, and LT3042 positive rail voltage regulator bottom right. OPA818 op-amp bottom center, with BUF602 output-driver bottom left.

After a number of failed attempts (with HMC799, OPA859), here is a reasonably fast One Inch Photodetector using OPA818, a FDS015 photodiode, and 1.2 kOhm transimpedance. Bandwidth is above 400 MHz, with the dark-noise and frequency-response in reasonable agreement with TIASim predictions.

With the detector blocked there's quite a lot of electrical feed-through with just the spectrum-analyzer TG-output on (see blue data points, especially above 1 GHz). I tried to correct for this roughly, shown as the orange data points.