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Difference between WDM and CWDM

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In this article, we are going to discuss the difference between Wavelength Division Multiplexing (WDM) and Coarse wavelength division multiplexers (CWDM). Let’s discuss them one by one. 

1. Wavelength Division Multiplexing (WDM): 
WDM stands for Wavelength Division Multiplexing. This is a fiber-optic transmission technique that facilitates the use of multiple light wavelengths (or colors) to send data over the same medium. On one fiber, two or more colors of light can travel and several signals can be transmitted in an optical waveguide at differing wavelengths or different frequencies on the optical spectrum. 

2. Coarse wavelength division multiplexers (CWDM): 
CWDM stands for Coarse wavelength division multiplexers. These were the modules that increase the amount of bandwidth the fiber optic system will carry by transmitting multiple signals at various wavelengths along the fiber optic cables. Generally, It is used for lower cost, lower capacity, wider range frequencies, and shorter distance applications where cost is an important factor. 

Difference between WDM and CWDM :

1. WDM uses a number of light sources, each emitting the light of different wavelengths. CWDM systems having less than 8 active wavelengths per optical fiber.
2. All the signals arrive at the same time, rather of being distributed across time slots. It uses wide range frequencies.
3. It improve the capability of optical cable in carrying data by multiplexing many channel of wavelengths. Its components use less space on PCBs.
4. The channel spacing is reduces to 1.6 nm or less. The channel spacing is large from 1.6 nm to 25 nm.
5. The band used are O and C. The band used are O, E, S, L and C.
6. It cost per channel is low. It has low cost.
7. The number of channels delivered are 2. The number of channels delivered are 17 – 18.
8. The best application is PON. The best application is short haul, metro.


  • There is possibility of transmission in full duplex mode.
  • A simpler reconfiguration
  • Extreme security
  • It offers more bandwidth.
  • This strategy might work best because it is straightforward to implement.


  • More compact space requirements
  • Cheaper and more compact wave filters
  • Able to use MMF cable or SMF fibre
  • Less power consumption because of electronic tuning.
  • Savings on startup and growth costs
    Can be powered by LEDs or lasers
    Increased payload sizes per channel


  • The system becomes more expensive as optical components are added.
  • When using WDM, lightwave transmission is only possible in a two-point circuit.
  • Bandwidth is not efficiently utilized.
  • Tuning of wavelengths is difficult
  • Problems with a cascaded topology
  • The OLT (Optical Line Termination) must have a transmitter array with one transmitter for each ONU (Optical Network Unit), so scalability is an issue. A problem could arise if a new ONU is added unless the transmitter has been provisioned beforehand. Each ONU needs to have a laser with a certain wavelength.


  • Lower range
  • Amplification versus regeneration
  • Not as much capacity as DWDM
  • The functions O, A, and M are not carrier-class.
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Last Updated : 10 Oct, 2022
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