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DWDM Active Systems With EDFAs & DCMs
Published: 2016-12-02 16:24:33
DWDM Active Systems With EDFAs & DCMs

DWDM is an ideal solution to build long-hual backbone networks and metro networks. In many cases, some components such as EDFA  and DCM are required to ensure high signal performance during the long-hual transmission. Today, the DWDM active system with EDFAs and DCMs will be presented.

Attenuation & Dispersion

A number of key parameters impact how optical fibers perform in transmission systems. The specifications for each parameter will vary by fiber type, depending upon the intended application. Attenuation and dispersion are two more important fiber parameters that affect the transmission performance.

Signal attenuation is caused by light loss in fiber. And light loss is caused by absorption by the fiber material and scattering of the light from the fiber. In addition, other causes such as microbends, macrobends, back reflections, fiber splices and mechanical connections can lead to signal attenuation. High attenuation limits the distance a signal can be sent through a network without adding costly electronics to the system. Attenuation is generally expressed in decibels (dB) for a given length of fiber, or per unit length (dB/km) at a specific transmission wavelength.


Dispersion limits the bandwidth or information carrying capacity of a fiber. According to different causes, dispersion can be divided into two basic types including chromatic dispersion and polarization mode dispersion. Chromatic dispersion in single-mode fiber links causes pulse spreading because of different wavelengths travelling at different speeds, causing a transmitted pulse to spread as it travels down the fiber. Polarization mode dispersion occurs in multimode fibers and other waveguides when different planes of light inside a fiber travel at slightly different speeds. The fast and slow axes with different group velocities cause spreading of the light pulse, making it impossible to transmit data reliably at high speeds.


DWDM Active Systems With EDFAs & DCMs

It is precisely because attenuation and dispersion limit the transmission performance. Thus, compensation is required for both attenuation and dispersion. EDFAs and DCMs are the devices respectively used to achieve attenuation and dispersion compensation.

EDFA, a commonly used optical amplifier, can ensure recovery of the light signal weakened by the optical fiber by amplifying the signal of any format and restoring large number of independent WDM channels at athe same time. Usually installed at specified distances of the long fiber line. However, every coin has two sides. Distortions that are accumulated during power amplification of the transmitted optical signal will lead to the lower OSNR (Optical Signal to Noise Ratio) at the receiving side of the DWDM system. Thus, when creating long-haul DWDM networks, several EDFA amplifiers are installed sequentially in the line. The number of amplifiers in one section is limited and depends on the optical cable type, channel count, data transmission rate of each channel, and permissible OSNR value.

In addition to installed optical amplifiers and the OSNR value, the possible length of lines when using active DWDM system is also determined by chromatic dispersion on transmitted signals. Thus, permissible values of chromatic dispersion for the transceivers should be taken into account at the design stage of the DWDM active system. In general, DCMs are applied in the line to compensate the chromatic dispersion. But, it is noted that DCM may introduce additional attenuation into the line, which reduces length of installed amplifiers.


3C-LINK Solutions for EDFAs & DCMs

3C-LINK offers a wide range solutions for WDM optical network. For DWDM active systems, we offer EDFAs and DCMs to meet the demands on attenuation and dispersion compensation. 3C-LINK EDFAs including various configuration type, housing type, wavelength and gain options are an essential component in metro, regional and long haul optical networks, offering high performance in signal amplification. 3C-LINK DCMs provide a flexible solution for accumulated chromatic dispersion without dropping and regenerating the wavelengths on the link. They serve at optical communication nodes to correct the pulse chromatic dispersion that reduces the maximal transmission distance of data in optical fibers.