The #DWDM network designer should properly scale his design according to the following main aspects.

1. Attenuation and power budget (Output and Input of Transponders, Insertion loss of passive components, Fiber attenuation, Amplifier input range/gain/output )

2. OSNR calculation (Calculation Tool and Transponders Receiving Tolerance)

3. Chromatic dispersion (Dispersion compensation fiber/module- #DCM)

4. PMD : Polarization Mode Dispersion (Use of PMD compensator)

5. Nonlinearity (Choice of transponder type, Low down input power to fiber, Widen channel spacing, Using a regenerator station)

Then keep in mind the following information required for DWDM design:

1 System Capacity

One of the mandatory information for the network design is: the initial and finalrequired capacity, as well as the maximum capacity that can be achieved withouttraffic interruption in case of future expansion. The customer usually providesdocumentation that specifies its needs for each span of each coverage area.

2 Service requirement

This requirement depends mainly on the capacity of the network, (i.e.: Whether itis a 10Gbit/s network or 2.5Gbits one).The traffic matrix will make it easier to track the traffics of different types andcapacities between the nodes of the network. Even that services may differ fromlink to another, the requirements may include data types which aim to be usedlater for future extension of the network.

3 Fiber Type

This point is often specified by the target customer, according to its existinginfrastructure and requirements. (i.e.: G.652, G.655, G.653…)In our projected network, all the fiber is G.655, but we found an elementary spanof G.654 which has been used for a small submarine part of the network.

4 Fiber length for each span and attenuation principle

Same as the previous point, we should study in details the operator requirementsto be well aware about the node sites, and thus about the fiber span length andsignal attenuation within the optical network. In fact, the optical Attenuators will be set according to several parameters that aremainly related to the span length, fiber attenuation, as well as the fiber type itself.

5 Site type (OTM, #OADM, OLA)

Deciding about the site type is strongly linked to the site accuracy and importancewith respect to the network use, user population at this site, etc. OTM sites generally stand for main sites that will deal with a high number ofwavelengths; you can refer to the network diagram to know the site assignmentaccording the site type.