Difference between CWDM and DWDM

1. Coarse wavelength division multiplexers (CWDM):
CWDM stands for Coarse wavelength division multiplexers. These are 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, CWDM is used for lower cost, wider range frequencies, lower capacity (sub-10G), and shorter distance applications where cost is an important factor. 

2. Dense wavelength division multiplexers (DWDM):
DWDM stands for Dense wavelength division multiplexers. These are modules that put data from different sources together on a fiber optic cable. These modules further increase system bandwidth and capacity by using closely spaced wavelengths to carry multiple signals on the same cable. In DWDM systems, the number of multiplexed channels is much denser as compared to CWDM because DWDM uses tighter wavelength spacing to fit more channels onto a single fiber. 

Difference between CWDM and DWDM :

S. No.	CWDM	DWDM
1.	CWDM system having less than 8 active wavelengths per optical fiber.	DWDM system having more than 8 active wavelengths per optical fiber.
2.	It is defined by wavelengths.	It is defined by frequencies.
3.	It has lower capacity as compared.	It has higher capacity as compared.
4.	It has low cost.	It has high cost.
5.	It has short range communication distance.	It has long range communication distance.
6.	It uses wide range frequencies.	It uses narrow range frequencies.
7.	Its light signal is not amplified here.	Its light signal amplification can be used here.
8.	Its no. of active wavelengths per fiber fewer than 8.	Its no. of active wavelengths per fiber more than 8.
9.	It breaks the spectrum into big chunks.	It dices the spectrum into small pieces.
10.	It has more wavelength spacing.	It has less wavelength spacing as compared.
11.	It does not use cooling laser.	It uses cooling laser that upholds temperature tuning and thus, provides better performance, increased safety and extend the lifespan of DWDM system.
12.	Advantages- Less power consumption because of electronic tuning. More compact space requirements Able to use MMF cable or SMF fibre Cheaper and more compact wave filters Savings on startup and growth costs Can be powered by LEDs or lasers Increased payload sizes per channel	Advantages- Reducing the number of repeater “amp” sites Growth that you pay for The largest capacity system obtainable. Maximum range possible with EDFA’s O, A, and M systems are developed to maturity.
13.	Disadvantages- Lower range Amplification versus regeneration Not as much capacity as DWDM The functions O, A, and M are not carrier-class.	Disadvantages- More power consumption Require large space High EDFA costs for amplifiers Start-up costs are higher than for a CWDM system of equal value. High-precision lasers and wave filters are required.