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Optical fibre system vs wireless

Short answer

In an optical fibre system, electrical signals modulate an optical source (LED/laser); light propagates by total internal reflection in the core and is detected by a photodiode. Fibre offers higher bandwidth (Tb/s), immunity to interference, security, and no spectrum licence; disadvantages include lack of mobility, higher installation cost, and vulnerability to cuts.

Explain the working principle of optical fiber communication system. What are the advantages and disadvantages of optical fiber over wireless communication system?

Working principle

An optical fibre communication system transmits information as modulated light through a glass fibre. The electrical message signal is converted to light by a source, guided along the fibre by total internal reflection, and converted back to an electrical signal at the receiver.

 Message -> Driver/   -> LED or
 (input)    modulator    laser
                           |
           ====== fibre (TIR, repeaters) ======
                           |
 Output  <- Amplifier, <- PIN/APD
            decision      detector
  1. The information signal (usually digital) drives the optical source (LED or laser diode), which varies its light intensity with the data.
  2. The light is coupled into the fibre within its acceptance angle and travels by TIR. Splices, connectors and repeaters/optical amplifiers (EDFA) along the route maintain the signal.
  3. At the far end a photodetector (PIN or APD) converts the light into current.
  4. The receiver amplifies, equalises and regenerates the signal and passes it to the user.

Advantages of optical fibre over wireless

PointOptical fibreWireless
BandwidthTb/s per fibreLimited by allocated spectrum
InterferenceImmune to EMI and RF interferenceSuffers interference, noise
Fading/weatherNo fading, rain or multipath effectsMultipath fading, rain attenuation
SecurityVery hard to tapSignal open to interception
Spectrum licenceNot requiredRequired, and costly
ReliabilityStable, predictable lossVaries with path and weather
LatencyLow, constantCan vary

Disadvantages of optical fibre compared to wireless

  • No mobility: users must be at a fixed point; wireless supports mobile and roaming users.
  • High installation cost and time: trenching, ducts, poles and right-of-way, especially over mountains and rivers (a real problem in hilly Nepal); wireless can be set up quickly.
  • Vulnerable to cuts: road construction and landslides often break cables; wireless has no cable to cut along the path.
  • Hard to reach remote or scattered users: satellite or microwave is cheaper for sparse rural areas.
  • Repair needs splicing equipment and trained staff.
  • Broadcasting to many receivers is easy over radio but needs a separate fibre path to each user.

✓ Answer checked by Claude Opus 5.5 (high effort)

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