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HSC Module: Telecommunications Engineering
Quick questions on Transmission media (copper, fibre, radio): HSC Engineering Studies Telecommunications Engineering
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is twisted-pair copper?Show answer
Two insulated copper conductors twisted together (the twist cancels external interference and crosstalk between adjacent pairs).
What is optical fibre?Show answer
A glass or polymer fibre carrying light by total internal reflection. A core (high refractive index) surrounded by cladding (lower refractive index); the core-cladding boundary reflects the light internally if the angle of incidence exceeds the critical angle.
What is option 1: Copper twisted pair?Show answer
Eliminated. Attenuation makes a 50 km direct link impossible; would need repeaters every few hundred metres.
What is option 2: Coaxial copper?Show answer
Eliminated. Attenuation at 100 Gbps frequencies is severe; repeaters every km or two.
What is option 3: Microwave point-to-point?Show answer
Possible. 50 km microwave links at e.g. 11 GHz can carry 1 Gbps to several Gbps per channel, multiplied by carrier frequencies.
What is option 4: Single-mode optical fibre?Show answer
The right choice. One fibre pair carries 100 Gbps comfortably (or much more with WDM). At 1550 nm, attenuation around 0.2 dB / km means 50 km loses 10 dB; well within the link budget of a standard 100 Gbps transceiver.
What is free-space radio is "free"?Show answer
The medium has no per-metre cost, but spectrum is regulated and licences cost money. Reserved spectrum (cellular, broadcast) is allocated by government auction.
What is q1?Show answer
Compare twisted-pair copper, optical fibre and free-space radio on EMI immunity and explain why fibre is preferred for installations near high-voltage cabling. [4 marks]
What is q2?Show answer
Justify the choice of single-mode rather than multi-mode optical fibre for a 50 km link between two exchanges. [4 marks]
What is q3?Show answer
Explain why high-frequency radio (5G mmWave at 28 GHz, for example) needs cells with shorter range than lower-frequency cellular bands. [5 marks]