LONDON, Dec. 17 -- Bookham Technology Plc said it has agreed to buy Marconi Optical Components Ltd, a subsidiary of Marconi Plc, in a share transaction worth an estimated £ 19.7. Bookham said the deal was conditional on the approval of its shareholders. As part of the deal, Marconi has agreed to buy a minimum of £30 mllion of components from Bookham over the next 18 months.