Katanga is the Bajoran first officer of the USS Vortex in the Doctor's holonovel Photons Be Free, a thinly disguised and unflattering version of Chakotay seen in Author, Author.
Katanga is a holographic character in the seventh-season Voyager episode Author, Author. He belongs to Photons Be Free, the holonovel the Doctor writes about an Emergency Medical Hologram mistreated by the organic crew of a lost starship.
The Doctor insists the story is fiction, but each officer of the USS Vortex is plainly modelled on a colleague. Katanga stands in for Chakotay: he has the commander's face, but is a Bajoran with an earring and a different hairstyle, and he backs the tyrannical Captain Jenkins in treating the hologram as a piece of equipment.
The real crew are dismayed when they play the programme, and their reaction leads the Doctor to revise the work before it is published.