Legends
Enligt Wookieepedia - 15 500 BBY om man bara funderar på de tekniska aspekterna om det inte är totalt praktiskt.
By the time of the Duinuogwuin Contention around 15,500 BBY, Jedi studies and researches with "frozen blaster" technology yielded success; they developed a method to generate a focused beam of energy that arced in a circumferential path back to its source, creating a controlled energy circuit and leading to the first portable high-energy blades. However, these preliminary lightsabers were highly unstable and inefficiently guzzled energy from a belt-mounted power supply; they could only be used for a brief duration before overheating. As a consequence of these flaws, the first lightsabers were little more than ceremonial objects, seldom worn, and much less utilized.
Källa: New Essential Chronology (2005)