Dense WDM (DWDM): DWDM is defined in terms of frequencies.

DWDM’s tighter wavelength spacing fits more channels onto a single fiber, but costs more to implement and operate.

DWDM is for systems with more than eight active wavelengths per fiber.

DWDM dices spectrum finely, fitting 40-plus channels into the C-band frequency range.

A separate light wavelength carries each signal, and the dense in DWDM refers to its ability to accommodate up to 80 different wavelengths. Each wavelength is about 0.8 nanometer wide and shares a single optical fiber.

With DWDM, vendors have found various techniques for cramming 40, 88, or 96 wavelengths of fixed spacing into the C-band spectrum of a fiber.

In a passive systems, unpowered solution the xWDM transceiver resides directly in the data switch. The output from the xWDM transceiver connects to an unpowered multiplexer that combines and redistributes, multiplexes and demultiplexes, the various signals. As the xWDM transceiver resides in the data switch, it means that all xWDM functionality is embedded in the data switch.

Active CWDM/DWDM solutions are stand-alone AC or DC powered systems separated from the switch. The task of the stand-alone system is to take the short-range optical output signal of the fiber or IP switch and convert it to a long-range xWDM signal. This OEO, (optical to electrical to optical), conversion is handled by a transponder. The converted xWDM signal is then transmitted with the help of transceivers and multiplexers. Due to the separation of the xWDM transport solution from the actual switch, active systems also tend to be more complex than passive, embedded solutions.

• One of the best features of deploying DWDM over a flexible grid photonic line system is signal independence—the ability to support multiple generations of transponders independent of format, bit rate, symbol rate, etc.
• Many networks designed for 10 and 40 Gb/s are now carrying 200 Gb/s channels, and many that were deployed with flexible grid capability are now carrying 400 Gb/s and even 800 Gb/s signals!
• With DWDM, vendors have found various techniques for cramming 40, 88, or 96 wavelengths of fixed spacing into the C-band spectrum of a fiber.

• 100GHz ITU Channel Spacing (100GHz ITU)
• Low insertion loss
• Broadband transmission
• High channel isolation
• High stability and reliability
• Epoxy-free optical path

• DWDM System
• CATV networks
• PON Systems
• FTTx Systems