Jason Hayek

From Memory Alpha, the free Star Trek reference.

Commander Jason Hayek was the persona assumed by Commander Chakotay of the USS Voyager when he infiltrated a simulation of Starfleet Headquarters created by Species 8472 in 2375. In this year, Hayek was in his third year aboard the USS Intrepid. (VOY: "In the Flesh")

Commander Jason Hayek is probably a real officer in Starfleet based on the circumstances of the scenario.