In some cases, your DP will move you up when he/she gets the opportunity to direct an episode. Either way, it's about the relationships you have. If you're ready to make the move up, you have to start talking to the contacts you've made through the years.
In some cases, you may be asked for a reel. If the only reel you have is an operator reel, you're going to have to create a reel as a DP. As all the name talents will tell you (and I'm sure you know already), lighting is crucial to a show. Directors may change around every episode, but the DP creates the look that sets up the show. In some cases, the lighting is literally a "character" in the series.
So, before network execs take a chance on you lighting a show that hasn't been "set" by another DP, you're going to need a reel, that proves you can do the job.
For more tips and articles by top entertainment industry career coach, The Greenlight Coach, visit www.thegreenlightcoachblog.com