SDL Inc. of San Jose, Calif., announced a $210 million agreement under which it will purchase Queensgate Instruments Ltd. of Bracknell, UK. SDL will offer the company $3 million in cash and $57 million in stock, with the additional payments contingent on Queensgate's pretax profits in 2000 and 2001. Queensgate will function as a wholly owned subsidiary of SDL. Queensgate produces optical network monitoring modules for terrestrial long-haul fiber optic telecommunications. The company posted revenues of approximately $9 million in 1999 and more than 70 percent growth in its optical network monitoring business. SDL manufactures optical products for telecommunications, including dense wavelength division multiplexing applications.