Wave Division Multiplexing (WDM)
Multiplying Fiber Capacity through Light
The Prism Principle
WDM works exactly like a prism. It takes a composite beam of light containing many different wavelengths and splits them into individual channels using specialized filters or diffraction gratings.
Optical Mux/Demux Visualizer
Multi-Terabit Passive Infrastructure
Optical Engineering Note:In DWDM mode, channels are spaced 0.8nm (100GHz) apart. By combining multiple "colors" of light, we can achieve Enhanced capacity without adding physical fiber pairs.
WDM Varieties: CWDM vs. DWDM
The primary difference between standard WDM technologies is the "spacing" between channels.
- CWDM (Coarse WDM): Typically 20 nm spacing. Harder to interfere, cheaper lasers, but limited to 18 channels and shorter distances (no amplification possible).
- DWDM (Dense WDM): Typically 0.8 nm or 0.4 nm spacing. Supports 80+ channels. Uses EDFA (Erbium-Doped Fiber Amplifiers) to travel thousands of kilometers without converting back to electrical signals.
The Mux/Demux Anatomy
At the heart of a WDM link is the Multiplexer (Mux) and De-multiplexer (Demux).
- Individual lasers transmit at specific, stabilized wavelengths.
- The Mux combines them into one fiber.
- The Demux separates them at the receiver.
Conclusion
WDM is what makes the modern internet possible. Without the ability to send terabits of data over a single hair-thin strand of glass, the cost per megabit would remain prohibitively high.