Red Seal Electrician Practice
Signalling and communicationQuestion 51 of 1506

Which devices convert electrical digital signals to light and back in a fibre link?

  1. LEDs or lasers send; photodiodes receive the light
  2. Photodiodes at the sender, and LEDs or lasers at the receiver end
  3. Transformers at both ends, with a coil wound around each fibre
  4. Thermocouples at both ends, which measure the heat in the light
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Correct answer: LEDs or lasers send; photodiodes receive the light

The sender makes light pulses and the receiver turns them back into voltage.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 14.5: Optical Data Communication

Practice signalling and communication

Questions last reviewed: 18 October 2026