DWDM Dense Wavelength Division Multiplexing



Wavelength division Multiplexing (WDM) technique increase the capacity of signal carrying medium. WDM technique assign different frequency / wavelength value to every incoming signal. These signals are multiplexed on a single sharing medium. SONET/SDH use TDM technique and transmit data in the form of a single wavelength but DWDM transmit different wavelength for every signal.  


Multiplexing is a process in which multiple signals are combined for transmission over a single medium.

Fiber Optic

  • Lightweight
  • High data rate
  • Secure communication
  • No interference
  • Less Expensive (Lower attenuation mean few repeaters)

Result : Fiber Optic Everywhere

Why not SDH/SONET ???

  • Due to some Electronic issues.
  • Due to Dispersion problem.
  • Do to Optical detection circuitry.
  • Transmission over 10 G is more affected by Dispersion.
  • High transmission power required for high bit rate transmission.
  • Polarization Mode dispersion affects the limits of a light pulse travel without degradation.

DWDM Characteristics

  • Cost effectiveness.
  • Multi protocol support / Transparency : It is physical layer protocol, It supports all types of data packets.
  • Scalability.
  • Reliability.


It is the broadening of light pulses. It is a very critical factor limiting the signal transmission. Excessive spreading/broadening  cause bits to “overflow” their  time slots and overlap adjacent bits. It causes inter symbol interference.

  • CD = Chromatic Dispersion.
  • PMD = Polarization Mode Dispersion.


WDM is the technique of data transmission by splitting and combining the multiple wavelengths of light.

  • Coarse WDM.
  • Dense WDM.

are two products of WDM but with different characteristics.They are differ in

  • Number of Channels.
  • Channel Spacing( 20 nm in CWDM and less than 1 nm in DWDM).
  • Power. (DWDM require more power than CWDM).
  • Cost. (DWDM 4 to 5 time expensive).
  • Signal Amplification.
  • Data Transmission. (DWDM can transmit longer distance).

EDFA – Erbium Doped Fiber Amplifier

  • It is a fiber amplifier or Light amplifier.
  • They preserve the wavelength of optical signal.
  • Can amplify multiple channels simultaneously.
  • Fiber Amplifier are 50% cheaper than regenerator.
  • No need of optoelectronic conversion process.

A process in which re generators are used to amplify the single optical signal at one time. A photo detector is used to convert light signal into electrical signal for amplification.

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4 Responses to "DWDM Dense Wavelength Division Multiplexing"

  1. I am gaurav from india and i have seen your WDM vedio and its very helpfull to know the basics about WDM.
    Pls post something about installation for WDM
    Good work thanks for ur vedio


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