If you're looking for out-of-universe evidence, I recall George Takei saying in an interview that Sulu was supposed to have a Katana in "[The Naked Time][1]." But Takei requested it be changed to a European sword as he was "Japanese-*American*" and didn't want to portray himself as traditional Japanese. 

Of course, it could just be that "Katana" was the only type of East-Asian weapon known to Roddenberry or the production crew. But I believe it is uniquely Japanese.

I think it was from the special features of the first Abrams movie when they're discussing new Sulu's ridiculous folding sword and it's continuity (or lack thereof) with Sulu's European fencing sword from The Naked Time. 

I'm trying to find a source.


EDIT: found a source, although it's not the one I remember this from. 

> John D.F. Black came up with Sulu's "berserk" scenes without specifying the weapon to be used. Unable to decide between a **samurai sword** or a fencing foil, he left the choice to George Takei, who picked the latter with the thought that by the 23rd century Humanity would have developed to a point where, in terms of culture, people have moved beyond simply adhering to ways of their **ethnic background**.

From [Memory Alpha][2], quoted very closely from [this video][3]. The fact that Sulu argues that culture shouldn't just depend on ethnicity leads me to believe that the actor's ethnicity was taken into consideration when conceiving the character.

I still recall a different video in which Takei explicitly draws a line between being "Japanese" and being "Japanese-*American*" which I think makes my case more convincingly, but I can't seem to find it.


  [1]: http://memory-alpha.wikia.com/wiki/The_Naked_Time_(episode)
  [2]: http://memory-alpha.wikia.com/wiki/The_Naked_Time_(episode)#Sets_and_props
  [3]: https://www.youtube.com/watch?v=QpQidddBIa4