Patent ID: 7104700

Claim:
A gain flattened, erbium-doped optical fiber amplifier comprising: a first erbium-doped optical fiber amplifying and outputting an inputted optical signal; a second erbium-doped optical fiber re-amplifying and outputting the optical signal having been amplified; a pumping light source outputting a pumping light; a first wavelength selective coupler providing the pumping light to the first erbium-doped optical fiber; a second wavelength selective coupler separating the remnant pumping light and the optical signal received from the first erbium-doped optical fiber; a third wavelength selective coupler providing the remnant pumping light received from the second wavelength selective coupler and the optical signal received from a gain flattening filter to the second erbium-doped fiber; and the gain flattening filter disposed between the second and third wavelength selective couplers receiving the optical signal from the second wavelength selective coupler, comprising: a housing having a first opening and a second opening; a first ferrule disposed at one end of the housing, having a first inclined surface, and having an opening through which an input of an optical fiber is packaged; a second ferrule disposed at the other end of the housing, having a second inclined surface, and having an opening through which an output of the optical fiber is packaged, wherein the first and second inclined surfaces are in a substantially non-parallel relationship; and, a plurality of thin film filters spaced a-part from each other and disposed in sequence between the first and second ferrules for flattening gain of optical signals passing therethrough, wherein the thin film filters has a peak loss of at least 7 dB.