Coarse wavelength division multiplexing (CWDM) and dense wavelength division multiplexing (DWDM) solve a big challenge faced by companies in the telecom and datacom industries. The two technologies allow them to get the most use out of an existing fiber optic cable. If they need more bandwidth on a main transmission line, CWDM or DWDM often beats the costlier alternative of installing more fibers.
This blog post explains how CWDM and DWDM function, the benefits of each and their applications.
Coarse Wavelength Division Multiplexing (CWDM)
Passive CWDM is a method of multiplexing and demultiplexing (mux-demux) optical signals over fiber optic transmission cables. It is a cost-effective way to scale connections over existing fiber infrastructure for point-to-point (P2P) or point-to-multipoint (P2M) connections for add/drop or fiber ring applications. Both passive CWDM cassettes and barrel filters are useful in a wide range of applications that benefit from the aggregation and separation of fiber channels. These applications include telecommunications, R&D test labs, research and mil/aero installations, among others.
Passive CWDM cassettes are commonly available for mux-demux of 4, 8, and 16 channels, with single-channel barrel OADM (optical add-drop multiplexer) filters that can add or drop a single channel to the composite signal. These cassettes and barrel filters can be made for inside plant (ISP) or outside plant (OSP) applications.
Dense Wavelength Division Multiplexing (DWDM)
DWDM is a method of creating several virtual fiber optic lines to multiply the capacity of the physical fiber optic line. WDM uses optical multiplexing that results in increasing bandwidth over existing fiber optic cabling without needing to add cabling. Optical multiplexing involves simultaneously combining several transmitted and received signals of different wavelengths. The term “dense” in DWDM implies that it uses more densely packed frequency channels than “coarse” WDM.
Optical transponders with DWDM capability are needed to deploy DWDM technology, though previously installed fiber optic cabling may be reused. This often results in a much lower cost per bit for data traffic, as new cable may not be required to increase the bandwidth of a fiber optic network. The latest DWDM technologies support a maximum of 96 frequencies (wavelengths) on a single pair of fiber optic lines, and with proper optical transceivers, each DWDM frequency can readily support 100 gigabits per second, with future potential for ever greater throughput per pair.
DWDM wavelengths are within a band of wavelengths that allow the signal to be amplified with an erbium-doped fiber amplifier (EDFA). This capability gives DWDM support for longer distance links, which is an additional advantage over CWDM besides the channel count.
DWDM vs. CWDM
Passive CWDM has the same footprint and power consumption as passive DWDM. However, CWDM is less expensive than DWDM due to the technology used in both the active and passive components.
CWDM channels are spaced 20 nm apart, which means that the transmitting lasers do not have the same wavelength tolerance requirements of a DWDM laser. This softer tolerance means that the cost of producing the CWDM transmitting lasers is lower. As expected, the passive channel filters also have a wider tolerance, and this also reduces cost to produce.
Conversely, DWDM channels with their typical 0.8 nm spacing, cost more. This is because they must maintain a narrow wavelength range, which requires additional controls in the transceiver. As expected, a DWDM channel filter also has a more narrow wavelength window, which increases the costs of those components.
Thus, DWDM has the advantage over CWDM in terms of channel count, but at a cost premium. The other main differentiator is that CWDM cannot be amplified. The range of CWDM technology is limited to 100 kilometers, as opposed to the much longer distances achievable by DWDM (when amplified). For many applications that are not as range-sensitive, the cost savings of CWDM compared to DWDM are appealing.
Both CWDM and DWDM are used to extend the life of legacy fiber optic network equipment and to delay expensive upgrades to the infrastructure while still providing enhanced throughput.
Applications
These passive WDM technologies are particularly useful in the fields of telecommunications and data communications. Telecom companies might include mobile/cellular providers, internet service providers, wireless service providers and cable TV (MSO). Datacom applications include enterprise networks, data centers, cloud storage/hosting and IT departments.
Big Fiber Selection, Same-Day Shipping
Among L-com’s wide selection of fiber optic components, we carry hundreds of CWDM and DWDM products, which include many connector types and mounting/packaging options for inside and outside plant use. Many have the popular single LGX mux and demux interface. We also offer optical add-drop multiplexers (ring OADMs), which multiplex and route different channels of light into or out of single-mode fiber.
We combine this vast inventory with same-day shipping. Even in this time of supply-chain challenges, our facilities are fully stocked and ready to support your business. Questions? Call us toll-free at 1-866-506-2818, chat with us live, or email us at sales@l-com.com.
