Both Passive CWDM and DWDM have been viable solutions in the telecommunications industry, but now, 10G Ethernet is appearing to be the most preferred solution over CWDM, everyone is migrating to the use of 10G Ethernet. This encourages many engineers to figure out how they ought to adjust their new designs to support the transition from 10G to CWDM. If you're one of these designers who's attempting to navigate the transition, the following is what you need to know.
Bandwidth Exts are Easier
In past years, designers who want to increase or improve their bandwidth could achieve this easily over a single or duplex mode fiber. During this period, the 1G Ethernet and CWDM solutions were sufficient, and the only limiting element was the power budget of the optical transceiver or the attenuation of your fiber. That it was possible to transmit up to 200 kilometers and utilize just a 1G Ethernet when designers preferred cheap CWDM.
Now, many people are considering the 10G Ethernet solutions, and that's why it's necessary to understand how everything will differ when using 10G over CWDM. When intending to migrate to 10G, you need to know the fiber type. For the dispersion and attenuation calculation, every designer need to know the recommended parameters from ITU-T and understanding the vendor and product kind of the fiber could also help. Remember that the physical fiber will work better than the standards claim most of the time.
Chromatic dispersion is referred to as the time variance of a single pulse of a signal. To summarize, chromatic dispersion is "the spreading of a light pulse per unit source spectrum width in an optical fibre due to the various group velocities of the different wavelengths composing the source spectrum" or in layman's terms, "the signal is stretched on the fiber transmission path due the dispersion characteristics of the transporting fiber."
Chromatic dispersion always exists, but the higher the link speed is, the greater important it becomes. For instance, a wavelength of 1310nm have a 0 ps/nm chromatic dispersion and 5, 25 dB fiber attenuation. In comparison, a wavelength of 1610 nm have a 330 ps/nm chromatic dispersion and a 3,45 dB fiber attenuation.
CWDM Over DWDM 10G is Cost-Effective
Designers should bear it in mind that CWDM implementation is more cost effective than passive DWDM infrastructure. These solutions will be more expensive because DWDM lasers cost more. DWDM lasers are essentially DFB lasers which are cooled, however, they are recommended as they contain the longevity that are required in these solutions. If you would like transmit a signal over a large distance, you should think about large metro ring topologies.
Though 10GBASE DWDM is more expensive, it's become the first choice because users have started to consider the costs after dividing it over the quantity of customers served. Some customers are more cost-conscious and have lower bandwidth capacity requirements; so, the cheap CWDM infrastructure will make more sense.
Remember that the new 10GBASE DWDM services is usually added over the same fiber. This will enhance the support of the initial CWDM infrastructure capacity by 4 times. This is irresistible to many designers.