Optical fiber apparatus with suppression of higher order modes

Optical fiber apparatus having a wavelength of operation, comprising:

• an optical fiber, said optical fiber including
• a core;
• a cladding disposed about said core;
• at least one region spaced from said core;
• said optical fiber being configured and arranged such that at the wavelength of operation said optical fiber comprises a first mode that is primarily a mode of one of said core and said at least one region and a second mode that is a mixed mode of a selected mode of said core and of a selected mode of said at least one region;
• and
• wherein said selected mode of said core and said selected mode of said at least one region are of the same azimuthal order.

Optical fiber apparatus having a wavelength of operation at which said optical apparatus is configured to propagate optical energy, comprising:

• an optical fiber comprising
• a core;
• a cladding disposed about said core;
• at least one region spaced from said core;
• said optical fiber being configured and arranged such that at said wavelength of operation said fiber supports a plurality of modes wherein the fundamental mode is primarily a mode of said core, at least one higher order mode (HOM) is a mixed mode of a selected mode of said core and a selected mode of said at least one region, and wherein at least another HOM having a lower mode order than said at least one HOM is not a mixed mode and is primarily a mode of said or said at least one region;
• and
• wherein “lower mode order” means that the at least another mode is nearer in terms of effective index to the fundamental mode than the at least a first HOM.