I'll assume you are in the same room as the saber.
There is a raised round block on a ledge near one wall. It's above a tunnel and ramp that lead to the cage with the saber. Jump up to the block and it will lower from your weight. Use force speed about halfway down. Select pull and run to the cage when the block gets close to the bottom. As you approach the cage, aim at the saber and pull. You can also just jump up to the saber, and then cut your way out of the cage if you get trapped.
Highlight the box above by dragging the mouse across it if you want to see the answer. If you're not in that room and don't want spoilers, provide more information as to exactly where you are.