Canada's Nortel Networks said on Wednesday it plans to sell its optical networking and carrier ethernet businesses to U.S.-based Ciena in a stalking horse agreement worth $521 million.

The cash and stock offer includes all assets of the optical networking and carrier ethernet businesses globally as well as patents and other intellectual property.

Under the terms of the deal, Ciena will pay $390 million in cash and another 10 million common shares. Ciena shares last traded at $13.05 on Nasdaq on Tuesday.

A stalking horse bid, reached in agreement with the company being bought, sets a floor under the value of the assets against which all other prospective bids will be measured.

($1=$1.06 Canadian)

(Reporting by Scott Anderson; Editing by Derek Caney)