Sending UART Serial Data over Plastic Optical Fiber (POF)
Using plastic optical fiber (POF) to transmit UART serial data provides EMI resistance and electrical isolation. Here's how to do it:
🧰 What You Need
- Plastic Optical Fiber (POF) – typically 1mm core, 650nm red LED compatible.
- Optical Transceivers – e.g., Avago HFBR-1521 (TX) and HFBR-2521 (RX)
- Microcontrollers or USB-to-UART adapters
- Resistors and capacitors – per the transceiver datasheet
- Logic level shifters – if voltage levels don't match
🔌 Basic Wiring Overview
TX Side (UART → Optical)
- Microcontroller UART TX → Optical Transmitter (e.g., HFBR-1521)
- Power (3.3V or 5V)
- Current-limiting resistor for LED (per datasheet)
RX Side (Optical → UART)
- Optical Receiver (e.g., HFBR-2521) → UART RX
- Power supply
- Pull-up resistor on RX output (if open collector)
🛠️ Wiring Example with HFBR-15X1 / 25X1
-
TX Module (HFBR-1521):
- Anode → Vcc through resistor
- Cathode → UART TX (possibly via transistor)
-
RX Module (HFBR-2521):
- Output → UART RX with pull-up resistor to Vcc
⚠️ Note: These modules output non-inverted logic compatible with UART.
⚙️ UART Settings
- Baud Rate: up to 250 kbps recommended for stable operation
- Settings: Standard 8N1 (e.g., 9600 8N1)
📏 Max Transmission Distance
- Up to 20 meters for typical POF setups
🧪 Testing
- Connect USB-to-UART adapter to one side, microcontroller or another adapter to the other
- Use serial terminal (PuTTY, Arduino IDE, etc.) to send test messages
- Perform loopback or echo tests