I recently taught a class in using the Jo to defend against a sword attack. There are stories which say that the jo was developed as a weapon to be used against the sword. Only certain people in old Japan were allowed to carry swords, but anyone could use a stick.
The Jo has certain qualities which make it well suited for defense against a sword. First, the Jo is made from Japanese Red Oak, which is strong, supple, and can hold a blade which cuts into it. The length is a compromise between reach, and weight. It is light enough to be very fast, yet longer than a sword. Used with skill, the Jo can be used to defend against a sword attack.
Three basic concepts should be considered in Jo defence against the sword: evasion and strike, catch and counter, and block and throw. In the first of these, the trick is to evade the sword strike. Step to one side and let the sword go by, the strike as as the attacker becomes open. Alternatively, the jo can be used to catch the sword, and then counter with either a strike or a throw. Finally, the jo can be used to block a strike, and then throw with the other hand.
Here are some techniques to consider: