Difference between WDM and DWDM

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

1. WDM: WDM stands for Wavelength Division Multiplexing. It is a fiber-optic transmission technique that enables the use of multiple light wavelengths (or colors) to send data over the same medium. There can travel two or more colors of light on one fiber, and several signals can be transmitted in an optical waveguide at differing wavelengths or frequencies on the optical spectrum.
2. DWDM: DWDM stands for Dense wavelength division multiplexers. These modules 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. The channel spacing is reduced to 1.6 nm and less. The cost-effective way of increasing capacity without replacing fiber. There are commercial systems available with capacities of 32 channels and upwards.

Difference between WDM and DWDM :

Sr.No.	WDM	DWDM
1.	WDM uses a number of light sources, each emits the light of different wavelength.	DWDM is WDM utilizing closely spaced channels.
2.	In this, Optical multiplexer is used at the input side to multiplex these signals.	In this, DWDM assigns the incoming optical signals to specific frequencies multiplexes them for transport over a single fiber.
3.	All the signals arrive at the same time, instead of being distributed across time slots.	In this, multiple channels of information carried over the same fiber, each using an individual wavelength.
4.	It improve the capability of optical cable in carrying data by multiplexing many channel of wavelengths.	It increases the bandwidth of systems, without using repeaters.
5.	The channel spacing is reduced to 1.6 nm or less.	The channel spacing is small 200GHZ.
6.	The band used are O (Original) and C (Conventional).	The band used are C (Conventional) and L (Long).
7.	It cost per channel is low.	It cost per channel is high.
8.	The number of channels delivered are 2.	There is hundreds of channels is possible.
9.	The best application is PON.	The best application is Long-haul.
10.	In WDM, 1310nm laser used which is combined with 1550nm lasers.	Only system Z is qualified to be used in DWDM.
11.	Advantages- Extreme security It offers more bandwidth. There is possibility of transmission in full duplex mode. A simpler reconfiguration This strategy might work best because it is straightforward to implement.	Advantages- Increasing scalability Allows multiple logical topologies to be used instead of a single physical MAN DWDM system with higher fibre capacity and longer span length Amplify your resilience New services will be offered Easier network growth System with the highest capacity possible is able to conserve switched bandwidth
12.	Disadvantages- Tuning of wavelengths is difficult Bandwidth is not efficiently utilized. The system becomes more expensive as optical components are added. When using WDM, lightwave transmission is only possible in a two-point circuit. 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. Problems with a cascaded topology	Disadvantages- Complex technology High precision wave filters and lasers  Not economical given the small channel numbers Requires more space and power