By Xiaolun Zeng and Michelle Derouin, Iridian Spectral Technologies
Gain flattening filters (GFFs), used to smooth out (i.e., “flatten”) unequal signal intensities over a specified wavelength range, have evolved significantly over the past 20 years. While the packaging and materials utilized to construct these components have remained almost unchanged, advances including improved coating processes and optimized manufacturing uniformity have pushed GFF performance to new heights.
More advanced, modern GFFs take advantage of designers’ ability to exert greater control over peak-to-peak error function (PPEF) — calculated by comparing the spectral performance of the manufactured filter to a client’s target gain curve specification — and can be promoted with higher level performance and imbued with additional functionality.
The slightest advantage in GFF performance or functionality can have huge implications for designers of erbium-doped fiber amplifier (EDFA) modules. If the filters they use do not facilitate an error function (EF) spec within the customer’s range, the EDFA designer is challenged to tighten parameter tolerance control in their packaging to correct the signal intensity variation.
Iridian’s premium GFFs deliver higher-level performance than traditional GFFs to meet these stringent PPEF specifications, as well as provide additional functionality. Whether an EDFA module designer wants to take on combined error function in-house — building an EDFA, calculating its EF, and then implementing GFFs — or they want to collaborate, building an EDFA with our filters implemented up-front, Iridian can help.