--- title: "Optical fiber advantages and wireless media" subject: "Telecommunications" chapter: 2 key: "semester_8/telecommunications:optical-fiber-wireless-media" source: https://www.bctengineer.com/q/semester_8/telecommunications/optical-fiber-wireless-media site: BCT Engineering --- # Optical fiber advantages and wireless media Telecommunications · Chapter 2: Transmission Media - Asked in: 2076 Chaitra, 2+5 marks - Video: [Communication Channels](https://www.youtube.com/watch?v=doAVuehH-L4) — Simply Coding - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/telecommunications/optical-fiber-wireless-media - Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-2 ## Question List out the advantages of optical fiber transmission media over twisted pair and co-axial cable. Also, explain different wireless transmission media in brief. ## Short answer Optical fibre offers larger bandwidth, lower attenuation (~0.2 dB/km), immunity to electromagnetic interference, high security, small size and electrical isolation. Wireless media include radio waves (omnidirectional, broadcasting/mobile), terrestrial microwave (line-of-sight, high capacity), satellite microwave (geostationary, ~250 ms delay), infrared (short-range), and free-space optics. ## Answer #### Advantages of optical fibre over twisted pair and coaxial cable - **Very large bandwidth** (THz range) – Gbps to Tbps with WDM. - **Very low attenuation** (~0.2 dB/km at 1550 nm), so repeater spacing of 50–100 km or more. - **Immune to electromagnetic interference** and lightning; no crosstalk between fibres. - **High security** – very hard to tap without detection. - **Small size and light weight**; easy to lay in ducts. - **Electrical isolation** – no ground loops, no sparks (safe in hazardous areas). - Made from silica (sand), long life, no corrosion. #### Wireless transmission media 1. **Radio waves (3 kHz–1 GHz, mainly HF, VHF, UHF):** omnidirectional; ground wave and sky wave (HF reflected by ionosphere gives long range); used for AM/FM broadcasting, mobile radio, cellular phones. Prone to fading and interference. 2. **Terrestrial microwave (1–40 GHz):** directional parabolic dishes on towers, line of sight, repeater every 40–60 km; high capacity trunks and mobile backhaul; affected by rain and obstruction. 3. **Satellite microwave:** a geostationary satellite (about 36,000 km) receives the uplink and retransmits the downlink; very wide coverage, ideal for remote and international links (VSAT); one-way delay about 250 ms. 4. **Infrared:** short-range (few metres), line of sight, cannot pass walls; TV remotes, IrDA. 5. **Free-space optics / light wave:** laser links between buildings; high rate but affected by fog. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is NOT an advantage of optical fibre over twisted pair and coax? A. Immunity to EMI and crosstalk B. Very large bandwidth C. Higher attenuation, requiring closer repeaters D. Electrical isolation with no sparks Answer: C. Fibre has very low attenuation (~0.2 dB/km), so repeater spacing is 50-100 km or more. (Key point: Fibre advantages) 2. A geostationary satellite at about 36,000 km gives approximately what one-way delay? A. 250 ms B. 25 ms C. 2.5 ms D. 2.5 s Answer: A. About 36,000 km up and down gives about 250 ms one-way delay. (Key point: Satellite delay) 3. Which describes infrared as a wireless medium? A. Long-range, passes through walls B. Short range, line of sight, cannot pass walls C. Uses the ionosphere to reach far D. Omnidirectional radio for broadcasting Answer: B. Infrared is a few metres, line of sight, used in remotes and IrDA. (Key point: Infrared media) 4. Which describes the radio wave medium (HF, VHF, UHF)? A. Narrow directional beam between dishes B. Laser link between buildings C. Omnidirectional, with ground and sky wave propagation D. Confined in a glass core Answer: C. Radio waves are omnidirectional and used for broadcast and mobile; HF sky waves give long range. (Key point: Radio waves) ## Related in Telecommunications - [Radio signal in twisted pair and coaxial cable](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aradio-signal-twisted-coaxial) — Telecommunications, chapter 2 - [Full duplex on a single twisted pair](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atwisted-pair-full-duplex-converter) — Telecommunications, chapter 2 - [Fiber optic vs copper cable](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Afiber-vs-copper-applications) — Telecommunications, chapter 2 - [Wired vs wireless media; four-wire and hybrid](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Awired-wireless-four-wire-hybrid) — Telecommunications, chapter 2, asked 2× - [Evolution from telegraphy to fiber and wireless](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aevolution-telegraphy-to-fiber) — Telecommunications, chapter 1 - [Guided and unguided transmission media](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atransmission-media-explain) — Telecommunications, chapter 2, asked 2× ## 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× - [Compare twisted pair, coaxial, fiber](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Acompare-twisted-coax-fiber) — Computer Networks and Security, chapter 2 - [Optical fiber vs satellite transmission](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aoptical-fiber-vs-satellite) — Data Communication, chapter 4 - [Coaxial cable vs optical fiber](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Acoax-vs-fiber) — Data Communication, chapter 4