The light sources used in fibre optics communication are . . . . . . . .

LED's and Lasers
Phototransistors
Xenon lights
Incandescent

The correct answer is A. LED’s and Lasers.

LEDs (Light Emitting Diodes) and lasers are the two main types of light sources used in fiber optic communication. LEDs are used for short-distance communication, while lasers are used for long-distance communication.

LEDs are small, inexpensive, and easy to use. They are also very reliable and have a long lifespan. However, LEDs have a relatively low output power, which limits their use for long-distance communication.

Lasers are more powerful than LEDs and can be used for long-distance communication. They also have a narrower beam than LEDs, which makes them more efficient. However, lasers are more expensive than LEDs and require more complex equipment to operate.

Xenon lights and incandescent lights are not used in fiber optic communication. Xenon lights are used in high-intensity discharge lamps, while incandescent lights are used in traditional light bulbs. Both of these types of light sources emit too much heat and are not suitable for use in fiber optic communication.

In conclusion, the light sources used in fiber optic communication are LEDs and lasers. LEDs are used for short-distance communication, while lasers are used for long-distance communication.