How to choose: CWDM, DWDM or CCWDM?

How does WDM work?
Wavelength division multiplex is referred to as WDM, which combines multiple signals at various wavelengths for simultaneous transmission over a single fiber optic cable. It usually has Multiplexer and Demultiplexer. Multiplexer (MUX) combines wavelengths at the transmitter, and the Demultiplexer(DEMUX) at the receiver separates the individual wavelengths. The main purpose of WDM is to increase the available bandwidth of fiber-optic cable. The capacity of a fiber can be increased tremendously simply by upgrading the multiplexer and demultiplexer on any given link. So WDM systems are popular with telecommunications companies because they allow them to expand the capacity of the network without laying more fiber.

Two types: CWDM and DWDM
There are two types of WDM standards: CWDM – coarse wavelength division multiplexing, and DWDM – dense wavelength division multiplexing.

One of the biggest differences between CWDM and DWDM is the Channel Spacing. Channel spacing refers to the difference between the nominal carrier frequencies of two adjacent channels and can be used to prevent inter-channel interference. The CWDM wavelength set consists of a series of 18 wavelengths spaced 20nm apart, from 1270nm to 1610nm. DWDM technology packs many more wavelengths in a much narrower band of the spectrum than CWDM. DWDM can carry 40, 80 or up to 160 wavelengths with a narrower spacing of 1.6/0.8/0.4nm (200/100/50GHz). Different channel spacing also results in different bandwidth and capacity that CWDM and DWDM can carry. The DWDM module further increases the system bandwidth and capacity by using tightly spaced wavelengths to carry more signals on the same fiber.

The biggest advantage of CWDM systems is the low cost, and the component cost is mainly reflected in filters and lasers. The wide wavelength spacing of 20 nm also gives CWDM the advantage of low specification of the laser and simplified structure of the optical multiplexer/demultiplexer. The structure is simplified, the yield is improved, so the cost is reduced. DWDM is mainly due to the high cost of laser diodes and the cooling laser technology used to maintain wavelength stability.

What is CCWDM?
CCWDM is a mini-wavelength division multiplexer, which is a mini version of CWDM. CCWDM has a much smaller package size, which is 10 times smaller than the standard CWDM package. CCWDM is cheaper than CWDM and DWDM. It can replace CWDM products in telecommunications, enterprise networks, PON network, cable television and other fields.

How to choose CWDM / DWDM / CCWDM solutions should be based on their respective characteristics and differences, comprehensive consideration of the needs and budget of the application scenario to make the optimal solution.

HYC can provide customers with a one-stop optical network device and low-cost optical communication products, supplying a range of WDM products. HYC Co.,Ltd（HYC）is a national Hi-tech optoelectronics company engaged in R&D, manufacture and marketing of fiber optical products. Providing professional products and services for fiber connectivity, WDM, PLC splitter, and high-density datacom cabling. HYC products and solutions widely applied in 4G/5G, Data Center and Cloud Computing industry, etc.
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The advantages of CCWDM

CCWDM is a compact CWDM, Compact Coarse Wavelength Division Multiplexer. The CCWDM modules is the perfect means for adding capacity to your fiber optic network without installing additional fiber.

The main difference between CWDM and CCWDM is that the CWDM system uses a low-cost, no-refrigerated distributed feedback (DFB) laser, while the CCWDM collimator and filter are soldered on a common substrate, and the cascade structure is different.

A three-port filter for a particular CWDM wavelength channel consists of two lenses and a TFF of that wavelength channel to pass or reflect the beam based on its wavelength contents. Each filter’s reflection port is connected to the subsequent filter’s common port. The filters are connected by a fiber connector, which is a CWDM multiplexer.

CCWDM is more compact. Adjacent channels are cascaded, not through a bulky fiber cascade solution but rather in free-space, under collimated beam conditions.

The principle is to use an input lens to focus the optical signals of the wavelengths λ1, λ2…λn on the first filter; the optical signal with the wavelength λ1 passes through the first filter and is coupled to the first output lens. In the first output fiber, the optical signal of wavelength λ1 is separated; the remaining optical signals are reflected by the first slide to the next slide for optical signal separation; and so on, until all signals are separated. The coupling between the wavelength channels is achieved in the form of zigzag lines of light.

Based on the above principles, CCWDM has the following advantages:

1. Small package size

Due to the limitations from the minimum bend radius of a fiber circuit, the dimensions of the packaging cassette cannot be reduced significantly.In fact, most of the space in the box is unused. CCWDM’s adjacent channels use parallel beams to cascade in free space instead of using optical fibers. Without the fiber used for cascading, the size of the CCWDM package can be greatly reduced. The standard 4CH CWDM has a size of 80×60×12 mm, and the CCWDM module of HYC Company has a size of 50×27×7.7 mm, which is about 1/4 of the standard CWDM package size. It can be widely used in high density environments.

2. Low insertion loss

Because CWDM and CCWDM adopt different packaging methods, the factors that cause loss is also different. The main factor affecting CWDM insertion loss is the coupling loss and filter loss between the collimator and the collimator. Due to different cascading modes, CWDM uses twice as many collimators as CCWDM, which inevitably leads to a large loss of CWDM, especially when the number of signals is large.

3. Good stability

Compact CWDM devices are less temperature sensitive than CWDM. The main reason is that the construct of CCWDM reduce the tilt of the reflected beam.CCWDM is connected with a rough filter side, the bonding force is much larger than that of CWDM, which effectively reduces the tilt of the reflected beam. The reflected beam tilt is the most important factor in the TDL of the device. For example, HYC Company 4CH CCWDM module has an operating temperature range of -40℃ to 85℃ and can be adapted to various environments.

4. High expandability

The CCWDM is available in 4/8/10 channels with an extended port channels, and can be expanded for more channels.

In addition, CCWDM has the characteristics of good temperature stability and high reliability compared with traditional CWDM. Due to its small package size, ultra-low optical path loss and temperature, CCWDM modules are widely used in wavelength division multiplexing systems, passive optical networks, and broadcast cable TV networks.