Hollow core optical fibre transmission link

A method for producing an optical fibre transmission link comprising:

• identifying (S1) a plurality of portions of optical fibre to be arranged sequentially to define an optical fibre transmission link for propagating optical signals at a selected wavelength or wavelength range to and/or from an optical transceiver;
• from the plurality of portions of optical fibre, identifying (S2) at least two portions to comprise portions of hollow core optical fibre, the at least two portions including at least one short portion of hollow core optical fibre having a length of 100 m or less and at least one long portion of hollow core optical fibre having a length of 500 m or more;
• selecting (S3), for the at least one short portion, a hollow core optical fibre with a first higher order mode attenuation at the wavelength or wavelengths;
• and
• selecting (S4), for the least one long portion, a hollow core optical fibre with a second higher order mode attenuation at the wavelength or wavelengths which is smaller than the first higher order mode attenuation.