Does one fennel plant produce a bulb year after year

First of all, it's not a good idea to buy plants or grow them in modules, as they hate any root disturbance, and when planted out may go straight to seed instead of producing a decent bulb. (You can always use the foliage and seed though as flavouring).
Get seed and sow it directly. (About this time of year, and not before the end of May) It takes a little while to come up but should go on to produce a good bulb. Keep it reasonably well watered. The best bulbs I've ever had came from self-seeding plants. The plants are biennial so produce the bulb and then the seed later. If you harvest the bulb of course you don't get any seed, so leave at least one in place to self-seed or from which to collect the seed for future crops.

Are they bulb fennel or the normal herb fennel?!

Erm....its the bronze fennel, and on the plant label it says the bulb can be used...so I guess its bulb fennel....seems logical I suppose.
I did mention that I am a novice didn't I? :o)

I never knew of a bronze bulb fennel! live and learn. If it says bulb then it must be!