Like Ard says you need to use a piece of fiberglass on the inside of the break. I've used graphite as well , but it's not as strong
It needs to be fitted carefully from the fat end of the blank section so that it fits tightly resembling a spigot ferrule.
You glue it all together at this point with epoxy and then wrap it over with white rod building thread ( or some other synthetic thread) and then cover the wraps with rod finish. The white thread will become transparent under the rod finish and you'll barely know it's there
I save broke fishing poles just for this, but finding a piece with the proper diameter is key.