--- title: "Communication system; optical fiber merits" subject: "Basic Electronics Engineering" chapter: 5 key: "semester_2/basic_electronics_engineering:define-comm-optical-merits" source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/define-comm-optical-merits site: BCT Engineering --- # Communication system; optical fiber merits Basic Electronics Engineering · Chapter 5: Communication System - Asked in: 2069 Poush, 2+4 marks - Video: [How Does LIGHT Carry Data? - Fiber Optics Explained](https://www.youtube.com/watch?v=G1Ke-H8I1uk) — Techquickie - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/define-comm-optical-merits - Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-5 ## Question Define communication system. Discuss about the merits of optical fiber communication over the other transmission media. ## Short answer A communication system sends information from source to destination via a channel using electrical, radio, or optical signals. Optical fiber offers extremely large bandwidth, very low attenuation, immunity to EMI, high security, small size, and safety compared to copper or radio. ## Answer A **communication system** is a system that sends information (voice, data, video) from a source to a destination through a channel using electrical, radio or optical signals. Its main parts are the information source, transmitter, channel, receiver and destination. #### Merits of optical fiber communication Optical fiber carries information as light through a glass core, using total internal reflection. Compared with copper cable, coaxial cable and radio links: | Point | Optical fiber | Copper / coaxial / radio | |---|---|---| | Bandwidth | Extremely large (THz) | Limited (MHz to GHz) | | Attenuation | Very low (0.2 to 0.5 dB/km) | High, needs frequent repeaters | | Interference | Immune to EMI, RFI and crosstalk | Affected by noise and lightning | | Security | Hard to tap | Easy to tap or intercept | | Size and weight | Thin and light | Thick and heavy | | Safety | No electrical hazard, no sparks | Risk of shock and sparks | | Cost of material | Silica is abundant and cheap | Copper is costlier | Other merits: - The high data rate allows thousands of telephone channels, or high-definition video, in one fiber. - Signal quality stays high over long distances, with a low bit-error rate. - The cable can easily be laid underground or undersea because it is non-conductive and corrosion-resistant. - It is future-proof: capacity can be raised by changing only the terminal equipment. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which list gives the main parts of a communication system? A. Information source, transmitter, channel, receiver, destination B. Source, amplifier, antenna, filter, load C. Transmitter, modulator, oscillator, detector, speaker D. Source, channel, repeater, switch, destination Answer: A. A communication system carries information from a source to a destination, and its main parts are source, transmitter, channel, receiver and destination. (Key point: Parts of a communication system) 2. Why can an optical fiber link run long distances with few repeaters? A. Its attenuation is high but it is amplified inside the glass B. Its attenuation is very low (about 0.2 to 0.5 dB/km) C. It carries signals at a much lower frequency than copper D. It has a narrow bandwidth that avoids loss Answer: B. The answer states this: Its attenuation is very low (about 0.2 to 0.5 dB/km). (Key point: Fiber attenuation) 3. Why is optical fiber immune to EMI, RFI and crosstalk? A. Its glass core is thicker than copper wire B. It uses very low-frequency signals C. It carries information as light, not as electrical current D. It is always buried underground Answer: C. The answer states this: It carries information as light, not as electrical current. (Key point: Immunity to interference) 4. Compared with copper, coaxial cable and radio, optical fiber has: A. Limited bandwidth but is easy to tap B. Large bandwidth but is easy to tap C. Limited bandwidth but is hard to tap D. Extremely large (THz) bandwidth and is hard to tap Answer: D. The answer states this: Extremely large (THz) bandwidth and is hard to tap. 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