An optical fiber, comprising: a central core having an outer radius r 1 and a maximum refractive index difference Dn 1 with respect to an outer cladding; a first intermediate cladding positioned between said central core and said outer cladding, said first intermediate cladding having an outer radius r 2 and a refractive index difference Dn 2 with respect to said outer cladding; and a buried trench positioned between said first intermediate cladding and said outer cladding, said buried trench having an outer radius r 3, a width w 3, and a negative refractive index difference Dn 3 with respect to said outer cladding; a second intermediate cladding positioned between said buried trench and said outer cladding, said second intermediate cladding having an outer radius r 4 and a refractive index difference Dn 4 with respect to said outer cladding; wherein said second intermediate cladding's outer radius r 4 is about 41 microns or less; characterised in that the optical fiber is a non-zero dispersion shifted optical fiber; in that said second intermediate cladding's refractive index difference Dn 4 is between about -9×10 -3; and -6×10 -3; in that, for a radius of curvature of 30 millimeters at a wavelength of 1625 nanometers, the optical fiber exhibits bending losses of less than 0.5 dB/100 turns; in that the optical fiber's 22-meter cable cutoff wavelength (22m-λ cc) is about 1150 nanometers or less; in that the optical fiber's effective two-meter fiber cutoff wavelength (2m-λ ceff) is about 1150 nanometers or less; and in that the ratio r 2:r 1 of said first intermediate cladding's outer radius r 2 to said central core's outer radius r 1 is between about 4.5 and 7.5. a central core having an outer radius r 1 and a maximum refractive index difference Dn 1 with respect to an outer cladding; a first intermediate cladding positioned between said central core and said outer cladding, said first intermediate cladding having an outer radius r 2 and a refractive index difference Dn 2 with respect to said outer cladding; and a buried trench positioned between said first intermediate cladding and said outer cladding, said buried trench having an outer radius r 3, a width w 3, and a negative refractive index difference Dn 3 with respect to said outer cladding; a second intermediate cladding positioned between said buried trench and said outer cladding, said second intermediate cladding having an outer radius r 4 and a refractive index difference Dn 4 with respect to said outer cladding; wherein said second intermediate cladding's outer radius r 4 is about 41 microns or less; characterised in that the optical fiber is a non-zero dispersion shifted optical fiber; in that said second intermediate cladding's refractive index difference Dn 4 is between about -9×10 -3; and -6×10 -3; in that, for a radius of curvature of 30 millimeters at a wavelength of 1625 nanometers, the optical fiber exhibits bending losses of less than 0.5 dB/100 turns; in that the optical fiber's 22-meter cable cutoff wavelength (22m-λ cc) is about 1150 nanometers or less; in that the optical fiber's effective two-meter fiber cutoff wavelength (2m-λ ceff) is about 1150 nanometers or less; and in that the ratio r 2:r 1 of said first intermediate cladding's outer radius r 2 to said central core's outer radius r 1 is between about 4.5 and 7.5.