A microstructured optical fiber for generating supercontinuum light upon feeding of light having a first wavelength λ 1, the optical fiber having a length and a longitudinal axis along its length and comprising a core region for guiding light along the length of said optical fiber, and a first cladding region surrounding said core region, wherein: - said optical fiber, along its length, comprises a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections, - said first fiber length section has a core region with a first characteristic core diameter W 1 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, wherein said first characteristic core diameter is larger than about 7 μm, - said second fiber length section has a core region with a second characteristic core diameter W 2 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, where said second characteristic core diameter W 2 is smaller than said first characteristic core diameter W1, - said intermediate length section of the optical fiber comprises a core region which is tapered from said first characteristic core diameter W 1 to said second characteristic core diameter W 2 over a tapered length L i, - said first fiber length section has normal dispersion at said first wavelength λ 1, wherein the first fiber length section has zero dispersion at a wavelength ZDW 1, wherein ZDW 1 is larger than about λ 1 + 20 nm, and said second fiber length section has zero dispersion at a second wavelength ZDW 2, where ZDW 2 is in the range from about λ 1 - 150 nm to about λ 1 + 50 nm and said second fiber length section has anomalous dispersion at wavelengths above said second wavelength ZDW 2. - said optical fiber, along its length, comprises a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections, - said first fiber length section has a core region with a first characteristic core diameter W 1 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, wherein said first characteristic core diameter is larger than about 7 μm, - said second fiber length section has a core region with a second characteristic core diameter W 2 in a cross-section through the microstructured optical fiber perpendicularly to the longitudinal axis, where said second characteristic core diameter W 2 is smaller than said first characteristic core diameter W1, - said intermediate length section of the optical fiber comprises a core region which is tapered from said first characteristic core diameter W 1 to said second characteristic core diameter W 2 over a tapered length L i, - said first fiber length section has normal dispersion at said first wavelength λ 1, wherein the first fiber length section has zero dispersion at a wavelength ZDW 1, wherein ZDW 1 is larger than about λ 1 + 20 nm, and said second fiber length section has zero dispersion at a second wavelength ZDW 2, where ZDW 2 is in the range from about λ 1 - 150 nm to about λ 1 + 50 nm and said second fiber length section has anomalous dispersion at wavelengths above said second wavelength ZDW 2.