How Compensating Gain Flattening Filters Improve PPEF Performance

By Hongbai Lao, Account Manager, and Michelle Briere, Application Engineer Manager, Iridian Spectral Technologies

One of the key parameters for the module and repeater performance on a gain flattening filter (GFF) is peak-to-peak error function (PPEF) — calculated by comparing the spectral performance of the manufactured filter to a device designer’s target gain curve specification.

Depending on the application, tight PPEF may need to be combined with other precise specifications, including modulation depth, insertion loss and error function slope. As the number of repeat units increases, the accumulated error function will increase. For long-haul fiber optic EDFA networks and long-distance submarine cable network applications, this is particularly problematic, as the accumulated error function increases significantly over long-distance transportation of the signal.

Using Iridian Spectral Technologies’ compensating GFFs, a primary filter with a precise error function can be implemented into the system and subsequent sets of filters can compensate for that primary filter’s error function.