Kirkland-based WaveDivision Holdings said Thursday that it has completed its $50M acquisition of Black Rock Cable, of Bellingham, Wash. Black Rock is ap rovider of high capacity fiber optic connectivity in Washington State, connecting large public and private customers in Whatcom, Skagit and Snohomish counties. Wave is a provider of broadband video, Internet, and phone to both residential and commercial customers. The firm raised a huge, billion dollar funding round in November.