Wave Division Multiplexing: WDM Distances

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WDM Distances

Optical Budget
With most WDM systems, the key to distance is calculating optical budget (the amount of light on the fiber). There are several key parameters that affect the optical budget:

Transmit Power: how much power is transmited by the laser
Receive Sensitivity: how much power the receiver needs in order to have valid signal
Transit Loss: loss along the fiber-optic cable (per km)
Insertion Loss: loss across a multiplexer when inserting the channel into a trunk
Passthru Loss: loss accross an add-drop multiplexer for a trunk signal passing through
Removal Loss: loss accross a demultiplexer when removing the channel from the trunk

Dispersion
Even when the optical budget is within the parameters of the optical power, there is another issue to consider, which is dispersion (the spreading out of light along a fiber). CWDM systems are typically limited by optical budget to around 100km. DWDM systems, due to higher power and better sensitivity, can operate to 200km typically, and are limited by dispersion. MRV provides low dispersion DWDM modules with the Fiber Driver-LD product over 600km.