An optical rotating joint installation; comprising: a drive shaft for a rotating interface, the drive shaft comprising a hollow central bore; and an optical rotating joint located in the hollow central bore. The proportion of the cross-sectional area of the material retained in the annular section of the drive shaft is preferably greater than or equal to 50%, more preferably 60%, yet more preferably 75%. The diameter of the hollow central bore is preferably less than or equal to 20 mm, more preferably 16 mm. The optical rotating joint installation may be provided as a retro-fit to replace an existing solid drive shaft that does not have an optical rotating joint, for example by hollowing out the existing solid drive shaft or by replacing the existing solid drive shaft with a drive shaft with a hollow central bore.