OFC pros and cons over metallic wire

Optical fibre communication (OFC) sends information as modulated light through a thin glass or plastic fibre by total internal reflection. Metallic wire systems (twisted pair, coaxial cable) send it as electrical current. OFC has replaced copper in most long-distance and high-capacity links, but it also has some drawbacks.

 Data -> Driver -> LED/Laser ~~~fibre~~~ Photodiode -> Amp -> Data
 Data -> Line driver ======copper wire====== Receiver -> Data

Advantages of OFC over metallic wire

1. Enormous bandwidth: optical carriers are at about $2\times10^{14}$ Hz. A single mode fibre with WDM carries many Tb/s, while a coaxial cable carries only up to a few GHz.
2. Low transmission loss: modern silica fibre has a loss of about 0.2 dB/km at 1550 nm and 0.35 dB/km at 1310 nm. Repeater spacing of 100–200 km is possible, compared with 1–5 km for coaxial cable. Fewer repeaters reduce cost and failures.
3. Immunity to interference: glass is a dielectric, so the signal is not affected by EMI, RFI, lightning or nearby power lines. Fibre can even run along high-voltage lines inside the overhead earth wire (OPGW, optical ground wire).
4. No crosstalk: light stays inside its own fibre, so many fibres can be packed in one cable without coupling.
5. Electrical isolation: there is no current, so no ground loops, short circuits, sparking or shock hazard. Safe in fuel stations, mines and chemical plants.
6. Signal security: fibre does not radiate, and tapping it causes a measurable loss, so it is hard to eavesdrop.
7. Small size and light weight: a fibre is about 125 µm in diameter. A fibre cable is much lighter and thinner than a copper cable of equal capacity, saving duct space and installation cost.
8. Flexibility and strength: fibre cables can be bent (within limits) and are strong in tension with Kevlar strength members.
9. Low cost raw material: silica is abundant; copper is expensive and often stolen.
10. Resistance to corrosion and temperature: glass does not rust and works over a wide temperature range.
11. Easy upgrade: capacity is increased by changing terminal equipment (higher bit rate, more wavelengths) without replacing the cable.

Disadvantages of OFC

1. Difficult joining: splicing and connecting need precise alignment, fusion splicers and trained technicians. Poor joints cause high loss.
2. Fragility: bare fibre breaks easily and has a minimum bending radius; tight bends cause macrobending loss.
3. Costly terminal equipment: lasers, photodetectors, optical amplifiers and test instruments (OTDR, power meters) are expensive.
4. No power transmission: repeaters and remote terminals need a separate power supply, while copper can carry power with the signal.
5. Electro-optic conversion: signals must be converted from electrical to optical and back at each end, adding complexity.
6. Repair and maintenance: locating and repairing a break needs special equipment and skill.
7. Not economical for very short or low-rate links where cheap copper is adequate.
8. Fibre fuse and radiation effects: high optical power and nuclear radiation can damage fibre.

Summary comparison

Because its advantages in capacity, distance and noise immunity far outweigh its handling difficulties, OFC is used for backbone networks, undersea cables, FTTH and LANs, while copper remains for short, low-cost connections.