Optical fiber filter for suppression of amplified spontaneous emission

An optical fiber filter for removing light of at least one predetermined noise wavelength from a fiber core, the fiber filter comprising

• a length of optical fiber comprising a core region having a first refractive index value denoted ncore;
• a cladding region surrounding the core region, said cladding region having a second refractive index value denoted nclad, where nclad<ncore;
• and
• a plurality of high refractive index cladding features disposed within the cladding region having a third refractive index value denoted nhi, where nhi>nclad, where the value of nhi and the physical properties of the plurality of high refractive index cladding features are selected such that the at least one predetermined noise wavelength is coupled from the core region to the cladding region while maintaining at least one optical signal propagating along the core region, where a coupling length between the core region and a nearest high index cladding feature of said plurality of high refractive index cladding features, and a coupling length between adjacent high index cladding features is essentially the same.