Patent ID: 7209620

Claim:
A dispersion optimized fiber having higher spot area comprising a center core region ( 1 ), a cladding region ( 2 ), a ring core region ( 3 ) and an outer glass region ( 4 ), wherein the said center core ( 1 ) and the said ring core ( 3 ) have refractive indices higher than the said outer glass region ( 4 ) and the said cladding region ( 2 ) has a lower refractive index than the said outer glass region ( 4 ), wherein n 1 , n 2 , n 3 and n 4 represent the refractive index of the said center core region ( 1 ) said cladding region ( 2 ) said ring core region ( 3 ) and said outer glass region ( 4 ) respectively and the said refractive indices are constrained by the following equations (1–4) to make the fiber have low dispersion and higher effective area during C and L band transmissions: n 1 >n 3 >n 4 >n 2 (1) 0.008>( n 1 −n 4 )>0.007 (2) 0.0018>( n 3 −n 4 )>0.0014 (3) −0.0005>( n 2 −n 4 )>−0.0007 (4) wherein the dispersion slope is 0.07 ps/nm 2 km, polarization mode dispersion is <0.1 ps/km 0.5 and the mode field diameter is 9.6 +0.4 μm.