Dual core photonic crystal fibers (PCF) with special dispersion properties

An optical fiber for transmitting light, said optical fiber having an axial direction and a cross section perpendicular to said axial direction, said optical fiber comprising:

• (1) a first core region comprising a first core material having a refractive index Nco,1 and at least one first core feature having a refractive being lower than Nco,1, whereby a resultant geometrical index Nge,co,1 of the first core region is lowered compared to Nco,1,
• (2) a micro-structured first cladding region, said first cladding region surrounding the first core region, and said first cladding region comprising a first cladding material and a plurality of spaced apart first cladding features that are elongated in the fiber axial direction and disposed in the first cladding material, said first cladding material having a refractive index Ncl,1 and each said first cladding feature having a refractive index being lower than Ncl,1whereby a resultant geometrical index Nge,cl,1 of the first cladding region is lowered compared to Ncl,1.
• (3) a second core region, said second core region surrounding said first cladding region, and said second core region comprising a second core material having a refractive index Nco,2, and
• (4) a micro-structured second cladding region, said second cladding region surrounding the second core region, and said second cladding region comprising a second cladding material and a plurality of spaced apart second cladding features that are elongated in the fiber axial direction and disposed in the second cladding material, said second cladding material having a refractive index Ncl,2 and each said second cladding feature having an refractive index being lower than Ncl,2, whereby a resultant geometrical index Nge,cl,2 of the second cladding region is lowered compared to Ncl,2, wherein
• the first core material, the first cladding material and the first cladding features, the second core material, and the second cladding material and the second cladding features are selected and arranged so that
• Nco,1>Nge,cl,1, Nco,2>Nge,cl,2, Nge,cl,1<Nge,cl,2, and
• the second cladding features are placed in a substantially two dimensionally periodic structure, whereby the second cladding region exhibits photonic band gap effect.

An optical fiber f or transmitting or guiding light, said optical fiber having an axial direction and a cross section perpendicular to said axial direction, said optical fiber comprising:

• (1) a first core region comprising a first core material having a refractive index Nco,1,
• (2) a microstructured first cladding region surrounding the first core region, said first cladding region comprising a first cladding material and a plurality of spaced apart first cladding features or elements that are elongated in the fiber axial direction and disposed in the first cladding material, said first cladding material having a refractive index Ncl,1 and each said first cladding feature or element having a refractive index being lower than Ncl,1, whereby a resultant geometrical index Nge,cl,1 of the first cladding region is lowered compared to Ncl,1,
• (3) a second core region surrounding said first cladding region, said second core region comprising a second core material having a refractive index Nco,2, and
• (4) a micro-structured second cladding region surrounding the second core region, said second cladding region comprising a second cladding material and a plurality of spaced apart second cladding features or elements that are elongated in the fiber axial direction and disposed in the second cladding material, said second cladding material having a refractive index Ncl,2 and each said second cladding feature or element having an refractive index being lower than Ncl,2 whereby a resultant geometrical index Nge,cl,2 of the second cladding region is lowered compared to Ncl,2, wherein
• the first core material, the first cladding material and the first cladding features or elements, the second core material, and the second cladding material and the second cladding features or elements are selected and arranged so that
• Nco,1>Nge,cl,1, Nco,2>Nge,cl,1, and Nco,2>Nge,cl,2.

An optical fiber for transmitting light, said optical fiber having an axial direction and a cross section perpendicular to said axial direction, said optical fiber comprising:

• (1) a first core region comprising a first core material having a refractive index Nco,1 and at least one first core feature having a refractive being lower than Nco,1, whereby a resultant geometrical index Nge,co,1 of the first core region is lowered compared to Nco,1,
• (2) a micro-structured first cladding region, said first cladding region surrounding the first core region, and said first cladding region comprising a first cladding material and a plurality of spaced apart first cladding features that are elongated in the fiber axial direction and disposed in the first cladding material, said first cladding material having a refractive index Ncl,1 and each said first cladding feature having a refractive index being lower than Ncl,1, whereby a resultant geometrical index Nge,cl,1 of the first cladding region is lowered compared to Ncl,1,
• (3) a second core region, said second core region surrounding said first cladding region, and said second core region comprising a second core material having a refractive index Nco,2, and
• (4) a micro-structured second cladding region, said second cladding region surrounding the second core region, and said second cladding region comprising a second cladding material and a plurality of spaced apart second cladding features that are elongated in the fiber axial direction and disposed in the second cladding material said second cladding material having a refractive index Ncl,2 and each said second cladding feature having an refractive index being lower than Ncl,2, whereby a resultant geometrical index Nge,cl,2 of the second cladding region is lowered compared to Ncl,2, wherein
• the first core material, the first cladding material and the first cladding features, the second core material, and the second cladding material and the second cladding features are selected and arranged so that
• Nco,1>Nge,cl,1, Nco,2>Nge,cl,1, Nco,2>Nge,cl,2, Nge,co,1<Nge,cl,2, and
• the second cladding features are placed so that the second cladding region exhibits photonic band gap effect.