This project demonstrates how to interface with SFP modules for fiber optic communications using an esp32-s2 microcontroller board (Wemos S2 mini). The program reads module info and sends a simple test bitstream.
WARNING: Do not use the 3.3V supply from the MCU board if it cant supply at least 500mA current (Wemos S2 mini can not!). Also use Caps to filter 3.3V supply for SFP module.
WARNING: Tx+/Tx- pins are a differential pair. Most SFP modules require a differential voltage of 0.2V-0.5V on these pins (see Datasheet of your SFP module). For low speeds (up to about 20kHz) you can use a voltage divider. The correct way is to use a single ended to differntial converter. Do not use 3.3V from IO pins directly !
| Function | SFP Module Pin | Esp32-S2 Pin |
|---|---|---|
| Tx Disable | 3 | 2 |
| MOD-DEF (SDA) | 4 | 7 |
| MOD-DEF (SCL) | 5 | 6 |
| Signal Loss | 8 | 3 |
| Tx+ | 18 w. divider | 16 |
| Tx- | 19 w. divider | 17 |
| VeeT | 1/20/17 | GND |
| VeeR | 9/10/11/14 | GND |
| VccT | 16 | (+3.3V) |
| VccR | 17 | (+3.3V) |