- 2078 Chaitra · 3+4 marks
OFC block diagram vs microwave link
Short answer
An optical communication system consists of electrical Tx, optical source (LED/laser), fibre channel (TIR), optical detector (PIN/APD), and electrical Rx. Compared to microwave, fibre offers Tb/s bandwidth, immunity to rain and interference, no licence, and high security. Applications include backbone networks, FTTH, and data centres.
Explain the block diagram of optical communication system. State advantages and applications of optical fiber compared to microwave communication link.
Block diagram of an optical communication system
+--------+ +----------+ +---------+
| Info |-->| Electr. |-->| Optical |
| source | | Tx/driver| | source |
+--------+ +----------+ +----+----+
| coupler
==== optical fibre, splices, ====
==== repeaters / EDFA ====
|
+--------+ +----------+ +----v----+
| Dest. |<--| Electr. |<--| Optical |
| | | Rx/decode| | detector|
+--------+ +----------+ +---------+
- Electrical transmitter: encodes the message and drives the source (intensity modulation).
- Optical source: LED or laser diode converts current to light at 850/1310/1550 nm.
- Fibre channel: guides light by TIR; connectors, splices and repeaters/optical amplifiers along the route.
- Optical detector: PIN or avalanche photodiode converts light to current.
- Electrical receiver: amplifies, equalises and regenerates the signal for the user.
Advantages of optical fibre over a microwave link
| Point | Optical fibre | Microwave link |
|---|---|---|
| Bandwidth | Tb/s | Hundreds of Mb/s to a few Gb/s |
| Repeater spacing | 80–100 km (more with EDFA) | 40–60 km, needs LOS towers |
| Weather | Unaffected | Rain fade, multipath, ducting |
| Interference | None | Co-channel interference |
| Spectrum licence | Not needed | Needed |
| Security | High | Lower (open air) |
Applications
- Long-haul trunks, national backbones and submarine cables
- Mobile (3G/4G/5G) tower backhaul and FTTH broadband
- LANs and data centres
- Cable TV distribution
- Power utilities (OPGW on transmission lines), railways, military and sensing
✓ Answer checked by Claude Opus 5.5 (high effort)
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