DWDM dense wavelength division multiplexing equipment has long-distance, high bandwidth transmission capacity; CWDM coarse wavelength division multiplexing equipment has low cost. So what if we choose the right wavelength division multiplexing equipment to build a cost-effective optical transmission system?
What is the difference between CWDM and DWDM?
At present, the effective way to solve the problem of increasing information transmission bandwidth is to use CWDM and DWDM devices, but they are different in many aspects.
(1) Channel spacing between CWDM WDM equipment and DWDM WDM equipment
Channel spacing is defined as the difference of nominal carrier frequency between two adjacent optical channels, which is generally used to prevent inter channel interference. CWDM wavelength division multiplexing equipment has a wider spacing than DWDM wavelength division multiplexing equipment. It can transmit 18 wavelengths in the spectral grid from 1271 nm to 1611 nm, and the channel spacing is 20 nm. DWDM can transmit 40, 80 or 160 wavelengths with channel spacing of 0.8 nm.
(2) Transmission distance between CWDM and DWDM
Because the wavelength of DWDM is highly integrated in the process of optical fiber transmission, DWDM can transmit longer distance than CWDM. At present, CWDM WDM equipment can't realize infinite distance transmission, its maximum transmission distance is only 160 km, and the transmission distance of DWDM equipment is far more than CWDM equipment.
(3) Modulated laser of CWDM and DWDM
The system of CWDM wavelength division multiplexing equipment has lower requirements on the technical index of laser, generally using uncooled laser; the system of DWDM wavelength division multiplexing equipment needs to use cooling laser, and the cooling laser adopts temperature regulation mode, which ensures that DWDM system has better performance, higher security and longer service life, so DWDM wavelength division multiplexer is better than uncooled laser The CWDM device of laser consumes more energy.
(4) Cost of CWDM WDM equipment and DWDM WDM equipment
Because the temperature distribution of DWDM system is not uniform in a wide wavelength range, the cost of DWDM system is increased when the cooling laser technology is used to adjust the temperature. In addition, DWDM systems are usually four to five times more expensive than CWDM systems. However, with the increasing popularity of DWDM, the price of DWDM optical module is about 20% - 25% lower than that of CWDM optical module.
Which CWDM / DWDM WDM equipment is better?
Usage of CWDM / DWDM WDM equipment
Due to the increasing demand for bandwidth, DWDM has made great progress in cost reduction, so it is more and more popular in the market. However, CWDM still has a high price advantage in the scenario of connection rate lower than 10g and short distance transmission. In the low data rate network construction, it is still the most feasible equipment.
Hybrid transmission of CWDM / DWDM WDM equipment
CWDM WDM equipment and DWDM WDM equipment have their own advantages in OTN network. The advantage of CWDM WDM equipment is that it can use low-cost distributed feedback laser without cooling and low-cost passive filter. Therefore, the system of CWDM WDM equipment is widely used in the system of DWDM WDM equipment. Although using CWDM Technology in DWDM system can also use cheaper optical modules, due to the large channel spacing of CWDM, the number of wavelengths available in the system will be reduced, which limits the transmission capacity of the system. Therefore, to some extent, it can not catch up with the non hybrid DWDM WDM equipment.
How to set up CWDM / DWDM WDM equipment network case analysis？
1. User needs
(1) Expansion and upgrade: connect 40ch DWDM WDM equipment to 1550nm channel of 8CH CWDM WDM equipment to realize channel combination.
(2) Node requirements: the link length is 65km, and two nodes need to be added at 15km and 50km.
2. Scheme design
(1) Due to the limitation of bandwidth, it is impossible to expand 40 DWDM channels, so FS engineers use 8CH c27-c34 DWDM WDM equipment to meet the application requirements of customers.
(2) Because the loss of WDM equipment, OADM and total fiber is less than 23dB, the output of single channel can be amplified to 8dB by using amplifier, so as to optimize the signal quality of link and reduce the error.
(3) Add 1ch OADM to each node to download and upload signals.
So far, if the user's WDM network needs more channels, they must convert to DWDM devices. Because the wavelength spacing of DWDM is small, the number of channels is allowed to be greatly increased, but the cost of each channel is also significantly increased. Therefore, users need to evaluate the future development of their business volume, so as to decide whether to install CWDM WDM equipment with poor flexibility at a lower initial cost or DWDM equipment with good flexibility at a higher initial cost.
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