How to choose: CWDM or DWDM Optical Module?

1. What are CWDM and DWDM?

Wavelength division multiplexing (WDM) is a communications technology that combines a series of information-carrying optical signals at different wavelengths into a single optical fiber for transmission. At the receiving end, the different wavelengths are then separated using some method. This technology allows multiple signals to be transmitted simultaneously on a single optical fiber, with each signal being carried by a specific wavelength, known as a wavelength channel. The application of WDM technology has revolutionized data transmission. WDM significantly enhances data carrying capacity, maximizes fiber utilization, minimizes the need for extensive cabling, and effectively reduces costs, making it a key technology for those seeking high-capacity, cost-effective data transmission infrastructure.

2. What is the difference between CWDM and DWDM?

Both CWDM and DWDM are derived from wavelength division multiplexing technology, but they differ in wavelength modes and application scenarios. CWDM is a low-cost WDM transmission technology for the access layer of metropolitan area networks. Its most important advantage is its low equipment cost. DWDM enables high-capacity data transmission over existing fiber optic infrastructure, avoiding the cost and complexity of laying new fiber. It is widely used in optical communications, such as fiber backbone networks, fiber access networks, and data centers.

3. What are the frequencies of DWDM and CWDM?

CWDM, or Coarse Wavelength Division Multiplexer, is also known as coarse wavelength division multiplexing. CWDM uses wavelengths between 1270nm and 1610nm and has 18 different wavelength channels, each separated by 20nm. DWDM, or Dense Wavelength Division Multiplexer, is also known as fine wavelength division multiplexing. DWDM wavelength spacing can be 1.6nm, 0.8nm, 0.4nm, or 0.2nm, accommodating 40, 80, or 160 wavelengths. DWDM's wavelength range is 1525nm to 1565nm (C-band) and 1570nm to 1610nm (L-band). DMDM commonly uses the C band (C17-C61), with a wavelength spacing of 0.4nm.

4. What are the transmission distances of CWDM and DWDM?

DWDM uses dense wavelength division multiplexing (DWDM) where wavelengths are highly integrated during optical fiber transmission. Therefore, devices using DWDM technology generally have longer transmission distances than CWDM. The maximum transmission distance for CWDM is 160km, while DWDM can reach even greater distances, reaching hundreds or even thousands of kilometers.

5. Lasers for CWDM and DWDM

Wavelength division multiplexing (WDM) in optical modules requires lasers. During operation, DWDM optical modules require cooled lasers for temperature regulation to prevent temperature fluctuations from causing wavelength drift outside the filter channels of the multiplexer and demultiplexer. CWDM optical modules, on the other hand, use uncooled lasers.

6. What is the difference between SWDM and CWDM?

SWDM stands for short-band wavelength division multiplexing (CWDM). While its principle is similar to CWDM on single-mode fiber, SWDM marks the first application of this technology to the short-wavelength bands of multimode fiber. Using a multiplexing/demultiplexing (MUX/DMUX) technique, optical signals in four wavelength bands are transmitted on a single multimode fiber. The four wavelength windows are 850nm, 880nm, 910nm, and 940nm.

The YXFiber 100G QSFP28 SWDM4 optical module utilizes a multimode duplex LC connector and requires only two fiber cores. It can be used with traditional OM3 and OM4 infrastructure, achieving transmission distances of up to 70 meters with OM3 fiber optic patch cables, 100 meters with OM4 fiber optic patch cables, and 150 meters with OM5 fiber optic patch cables, providing users with a high-speed and cost-effective cabling solution.

7.Questions & Answers

7.1 What is the main difference between the 10G DWDM Tunable SFP+ module and the conventional DWDM optical module?

The 10G DWDM Tunable represents a distinctive optical module enabling you to designate the channel or "colour" of laser emission. In essence, conventional DWDM systems employ fixed-wavelength optical modules, while Tunable optical modules possess the capability to modify the wavelength as required for diverse applications. It's important to underline that the wavelength adjustment feature of the tunable SFP+ DWDM is exclusive to DWDM systems.

7.2 What cable type is needed for the 25G CWDM modules?

Duplex single-mode cables with LC/UPC connectors. I bought some single-mode cables along with the modules and they match perfectly.

7.3 Can the 1G CWDM-SFP1G-ZX operate at a 100Mbps Ethernet speed?

Yes, it can support 100M.