---
title: "Advantages of optical fiber over copper"
subject: "Instrumentation II"
chapter: 5
key: "semester_5/instrumentation_ii:optical-fiber-advantages"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/optical-fiber-advantages
site: BCT Engineering
---

# Advantages of optical fiber over copper

Instrumentation II · Chapter 5: Data Acquisition And Transmission

- Asked in: 2074 Chaitra, 2 marks; 2070 Chaitra, 3 marks; 2075 Chaitra, 2 marks (asked 3 times)
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/optical-fiber-advantages
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-5

## Question

Explain the advantages of optical fiber over copper wire.

## Short answer

Optical fiber offers much higher bandwidth, lower attenuation (repeaters every 50–100 km), immunity to electromagnetic interference, electrical isolation, and greater security. It is also lighter, smaller, and resistant to corrosion.

## Answer

Optical fibre carries data as light pulses through a glass or plastic core, instead of electrons in copper wire. Its advantages over copper:

1. **Very high bandwidth:** terahertz range, so the data rate (Gbps to Tbps) is far higher than copper.
2. **Low attenuation:** about 0.2-0.5 dB/km, so repeaters are needed only every 50-100 km, whereas copper needs them every 1-2 km.
3. **Immunity to electromagnetic interference:** no pick-up from motors, power lines or lightning; no crosstalk.
4. **Electrical isolation:** no ground loops, safe in explosive or high-voltage areas (no sparks).
5. **Security:** difficult to tap without detection.
6. **Light weight and small size:** thin, light cable, easier to install in ducts.
7. **Non-corrosive material** and long life; resistant to many chemicals and weather.
8. **Plentiful raw material** (silica), cost per bit is lower on long links.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why can optical fibre carry much higher data rates than copper?
   A. Its bandwidth is in the terahertz range
   B. It uses higher voltages
   C. It has more repeaters per km
   D. It carries electrons faster
   Answer: A. Light carriers give terahertz bandwidth, so Gbps to Tbps rates are possible. (Key point: Bandwidth)

2. How does the repeater spacing of fibre compare with copper?
   A. Fibre every 1-2 km, copper every 50-100 km
   B. Fibre needs repeaters every 50-100 km, copper every 1-2 km
   C. Both need repeaters every 10 km
   D. Fibre needs no repeaters ever, copper every 100 km
   Answer: B. Fibre attenuation is only about 0.2-0.5 dB/km, so repeaters are far apart. (Key point: Low attenuation)

3. Why is fibre safe in explosive or high-voltage areas and free of ground loops?
   A. It uses very low voltage signals
   B. Its glass core is grounded at both ends
   C. It carries light, not current, so there are no sparks and it is electrically isolating
   D. It is shielded by a thick copper braid
   Answer: C. Being a dielectric carrying light, it is immune to EMI and cannot spark or create ground loops. (Key point: EMI immunity and isolation)

## Related in Instrumentation II

- [Optical fiber advantages and disadvantages](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aoptical-fiber-pros-cons) — Instrumentation II, chapter 5
- [Data logging system for optical, satellite, Bluetooth](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Adata-logging-three-schemes) — Instrumentation II, chapter 5

## Related in other subjects

- [Optical fiber advantages over coax and twisted pair](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Afiber-advantages) — Data Communication, chapter 4, asked 3×
- [Optical fiber and its advantages](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Aoptical-fiber-advantages) — Basic Electronics Engineering, chapter 5, asked 5×
- [Communication system; optical fiber merits](https://www.bctengineer.com/question.md?key=semester_2%2Fbasic_electronics_engineering%3Adefine-comm-optical-merits) — Basic Electronics Engineering, chapter 5
- [Optical fiber advantages and wireless media](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aoptical-fiber-wireless-media) — Telecommunications, chapter 2