CWDM vs DWDM: SFP+ Transceivers Buying Guide

Introduction to CWDM and DWDM: Why We Need Them

Since the 1980s, with the increasing demand for communication bandwidth, the transmission capacity of early optical fiber communication networks has been limited. How to expand the network capacity has become an urgent problem.

The easiest way may be to install more optical fibers. Although the cost of the optical fiber itself is not too high today, the cost of digging trenches and burying pipelines in the process of optical fiber installation is high and it takes a long construction time. Therefore, simply extending optical fiber is not future-proof. Here comes WDM (Wavelength Division Multiplexing) technology in this context, and it has been widely used in high-capacity optical transmission applications. 

Based on different channel spacing, WDM technology is divided into CWDM and DWDM. CWDM stands for Coarse Wavelength Division Multiplexer, and DWDM stands for Dense Wavelength Division Multiplexing. As the name implies, DWDM has a denser channel spacing than CWDM.

CWDM vs DWDM: What Are the Differences between Them

CWDM vs DWDM: Channel Spacing

The top difference between CWDM and DWDM lies in channel spacing. The channel spacing of DWDM is generally 0.2nm~1.2nm. Compared to DWDM, CWDM has a wider channel spacing, 20nm is the industry-recognized CWDM channel. The different channel spacing and the different number of transmission channels lead to CWDM and DWDM systems differ in the equipment technology solutions, components selection, and system costs.

CWDM vs DWDM: Cost

The cost difference between CWDM and DWDM systems is mainly caused by hardware cost. 

Firstly, for the laser device, the cost of a CWDM laser is much lower than DWDM since the DWDM has higher requirements of reliability and high dispersion tolerance to laser while CWDM doesn't.

Secondly, for optical multiplexing/demultiplexing devices, due to a larger number of multiplexed channels and smaller channel spacing of the DWDM system, the precision of multiplexed devices used in the DWDM system must be high, thus the multiplexing/demultiplexing devices cost is relatively higher. In CWDM systems, since the number of multiplexed channels is less and the spacing of adjacent wavelength channels is relaxed to 20nm, the fault tolerance of CWDM components is enlarged,  therefore, cheaper multiplexer/demultiplexer devices can be used.

Moreover, The laser used in the CWDM system is without a cooler, so the system power consumption is much lower, which is conducive to saving costs in the running processes.

CWDM vs DWDM: Power Consumption

The power consumption of the CWDM system is much lower than DWDM. The cooler and control circuit used in the DWDM laser consumes about 4W power per wavelength, whereas the CWDM laser without a cooler consumes only 0.5W power. For example, a 4-wavelength CWDM optical transmission system consumes about 10~15W while the power consumption of the similar DWDM system reaches up to 30W. In the DWDM system, power consumption and temperature management have become the key problems of circuit board design with the increase in the total number of multiplexed wavelengths and single-channel transmission speed.

CWDM vs DWDM: Distance

Compared to DWDM transport, transmission distance is a weakness of CWDM transport. DWDM transport supports long-distance transmission due to the use of a high-stable wavelength and advanced dispersion tolerance light source and optical amplifier. The longest haul transmission with no electrical relay at 4000km in a DWDM system.

The CWDM system only supports short-distance signal transmission. Due to the performance limitation of the low-cost laser and the inability to use the amplifier in CWDM, the CWDM transmission distance is generally no more than 80km at 2.5Gbit/s. If the transmission distance exceeds 80km, an electrical relay must be used. Therefore, the CWDM system is only applicable to metropolitan area networks (MANs) and edge access networks.

CWDM vs DWDM: Fiber Differences

G.652 and G.655 fiber can be used as DWDM fibers. When the transmission data rate is over 10Gbit/s. To get a system performance, G.655 fiber is more recommended in the DWDM system. When the DWDM system is running on L-wavelength, G.653 fiber can also be used. For the 8-wavelength CWDM system, since it has no special requirements for the fiber, G.652, G.653, and G.655 fiber are all adoptable.

CWDM/DWDM SFP+ Transceivers Buying Guide

When building a CWDM/DWDM system, CWDM and DWDM SFP transceivers are usually in high demand, since the OEM SFP optical transceivers are costly, choosing a reliable third-party CWDM/DWDM SFP+ supplier is vital. 

Performance and price are always the most important considerations. QSFPTEK 10G CWDM/DWDM SFP+ transceivers adopt industry-leading laser components. In QSFPTEK factory, all CWDM/DWDM SFP+ transceivers must be rigorously tested on performance before they are put into service. To ensure compatibility, the SFPs also need to be tested on the target vendors’ switches. QSFPTEK 10G CWDM/DWDM SFP+ transceivers are tested and promised to be compatible with most mainstream vendors, including Cisco, Juniper, Arista, etc.

With the guarantee of advanced technology, the price of QSFPTEK CWDM/DWDM SFPs is also competitive. The following forms list the prices of CWDM and DWDM SFP+ transceivers of FS.COM and QSFPTEK.COM. It can be found that the QSFPTEK has obvious superiority in price. For bulk orders, more attractive prices are available, welcome to consult via sales@qsfptek.com.

Reference: QSFPTEK 10G SFP+ DWDM Channel Plan: