Solution:

Active DWDM systems commonly refer to as transponder-based systems. They offer a way to transport large amounts of data between sites in a data center interconnect setting.

The transponder takes the outputs of the SAN or IP switch format, usually in a short wave 850nm or long wave 1310nm format, and converts them through an optical-electrical-optical (OEO) DWDM conversion.

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.

The possible length of lines when using an active DWDM system is determined not only with installed optical amplifiers and the OSNR value but also with the influence of chromatic dispersion the distortion of transmitted signal impulses, on transmitted signals.

At the design stage of the DWDM network project, permissible values of chromatic dispersion for the transceivers are taken into account, and, if necessary, chromatic dispersion compensation modules (DCM) are included in the line.

DCM introduces additional attenuation into the line, which leads to a reduction of the amplified section length.