Question 20 from UPSC CSE 2020 - S&T

Question

With reference to Visible Light Communication (VLC) technology, which of the following statements are correct?
1. VLC uses electromagnetic spectrum wavelengths 375 to 780 nm.
2. VLC is known as long-range optical wireless communication.
3. VLC can transmit large amounts of data faster than Bluetooth.
4. VLC has no electromagnetic interference.
Select the correct answer using the code given below:

Accepted Answer

Correct Option: C. 1, 3, and 4 only

Strategy: - Focus on the wavelength range of 375-780 nm, which falls within the visible spectrum, confirming statement 1.
- Flag statement 2: VLC is typically short-range as visible light cannot penetrate walls.
- Evaluate statement 3 using relative data rates: VLC (LEDs, Li-Fi) achieves much higher speeds than Bluetooth.
- Support statement 4: Light-based signals do not cause electromagnetic interference, a key advantage of VLC.

Key Info: Visible Light Communication (VLC) is a data transmission technology that uses visible light between 375 nm and 780 nm in the electromagnetic spectrum.

Key Characteristics:
- **Wavelength Range**: Uses visible light between 375 nm and 780 nm.
- **Sources**: Common sources include LED lamps, which can be modulated at very high frequencies for dual use in illumination and communications.
- **Range**: Limited to short-range communications since visible light cannot penetrate opaque objects such as walls, differentiating it from radio-based technologies.
- **Data Transfer Rates**: Can reach megabits to gigabits per second--vastly higher than typical Bluetooth (max 3 Mbps for Bluetooth 5), with advanced VLC/Li-Fi systems exceeding 1 Gbps.
- **EMI Immunity**: Immune to electromagnetic interference (EMI) as it does not use radio frequencies; this advantage makes it suitable in electromagnetic-sensitive environments such as hospitals and aircraft cabins.

VLC technology is a basis for Li-Fi, a bidirectional, high-speed wireless system. Applications include secure indoor networking, vehicular communication, and underwater data transmission, where radio signals are unsuitable.

Answer

Option A: 1, 2, and 3 only

Answer

Option B: 1, 2, and 4 only

Answer

Option D: 2, 3, and 4 only