2. For a better signal transmission in fiber-optic communication, different kinds of
technologies are applied to the industry. Wavelength-division multiplexing (WDM) is
one of the commonly used technologies which multiplexes a number of optical
carrier signals onto a single optic fiber by using different wavelengths of laser light.
That is to say, WDM enables two or more than two wavelength signals to transmit
through different optical channels in the same optical fiber at the same time.
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3. • There are two types of divisions WDM system-
• CWDM (coarse wavelength division multiplexing)
• DWDM (dense wavelength division multiplexing).
• They are both using multiple wavelengths of laser light for signal transmission on a single
fiber. However, from the below aspects
• Channel spacing,
• Transmission reach,
• Modulation laser
• Cost,
• CWDM and DWDM still have a lot of differences. This document will focus on these
distinctions and hope you can have a general understanding about CWDM and DWDM
technology.
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4. Channel Spacing
• As their names suggest, the words “coarse” and “dense” reveal the difference in
channel spacing. CWDM has a wider spacing than DWDM. It is able to transport up
to 16 wavelengths with a channel spacing of 20 nm in the spectrum grid from
1270 nm to 1610 nm. But DWDM can carry 40, 80 or up to 160 wavelengths with a
narrower spacing of 0.8 nm, 0.4 nm or 0.2 nm from the wavelengths of 1525 nm
to 1565 nm (C band) or 1570 nm to 1610 nm (L band). It is no doubt that DWDM
has a higher performance for transmitting a greater number of multiple
wavelengths on a single fiber.
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6. Transmission Reach
• Since the wavelengths are highly integrated in the fiber during light transmission,
DWDM is able to reach a longer distance than CWDM. The amplified wavelengths
provide DWDM with the ability of suffering less interference over long-haul cables.
Unlike DWDM system, CWDM is unable to travel unlimited distance. The maximum
reach of CWDM is about 160 kilometers but an amplified DWDM system can go
much further as the signal strength is boosted periodically throughout the run.
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7. Modulation Laser
• CWDM system uses the uncooled laser while DWDM system uses the cooling laser.
Laser cooling refers to a number of techniques in which atomic and molecular
samples are cooled down to near absolute zero through the interaction with one
or more laser fields. Cooling laser adopts temperature tuning which ensures better
performance, higher safety and longer life span of DWDM system. But it also
consumes more power than the electronic tuning uncooled laser used by CWDM
system.
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8. Cost
• Because the range of temperature distribution is nonuniform in a very wide
wavelength, so the temperature tuning is very difficult to realize, thus using the
cooling laser technique increases the cost of DWDM system. Typically, DWDM
equipment is four or five times more expensive than CWDM equipment.
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9. Conclusion
• CWDM and DWDM are both coming from the WDM technology that is capable of
conveying multiple wavelengths in a single fiber. But with different characteristics,
people should think twice before choosing the CWDM or DWDM system. CWDM
usually costs less but its performance is far behind DWDM. Both your
requirements and budget need to be taken into consideration. Moreover, the
WDM products including CWDM mux/demux module, DWDM mux/demux
module and optical splitter are highly welcome in the market.
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