Networks - Wavelength Multiplexing (WDM)

Combine multiple signals for transmission along fibre optics

Wavelength division multiplexing (WDM) is a technology that allows multiple wavelengths to propagate along the same length of optical fibre. As independent wavelength channels can be used to transmit data, the network capacity is increased compared to using one fibre per wavelength.

There are several technologies for wavelength division multiplexing including

  • Fused Biconical Taper (FBT) couplers
  • Thin Film Filters (TFF)
  • Arrayed Waveguide Gratings (AWG)

Coarse Wavelength Division Multiplexing (CWDM)

CWDM typically supports up to 16 wavelengths with 20 nm spacing in the 1270-1610 nm region. CWDM can also refer to less complex systems, such as a 1310/1550 nm mux.

Uncooled laser diodes may be employed for CWDM as the wide channel spacing allows for some wavelength variation due to temperature fluctuations.

Dense Wavelength Division Multiplexing (DWDM)

DWDM supports around 160 wavelengths with approximately 0.2 nm spacing between each wavelength. DWDM typically operates in a much smaller portion of the spectrum in the C-band (1525 – 1565 nm) where attenuation in standard optical fibre is at a minimum.

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