Last month, it emerged that ITV had given the green light to the show. The programme will air on ABC in the US and on Channel Seven in Australia.
Fellowes, who also writes Downton Abbey, has now said that he has a lot of "excitement" about the project.
"Of course it's terrifying going up against the [James Cameron] film," he added. "We can't hope to compete with those special effects."
Fellowes explained that the show will include a mixture of real and fictional characters, saying: "The producer and I would have battles to swap characters and keep our favourites!"
Filming for Titanic is scheduled to begin in May and it will air in April 2012 to mark the centenary of the ship's sinking.
> Helen Mirren, Romola Garai for 'Titanic'?