SAN JOSE, Calif., June 2 -- SDL Inc. and JDS Uniphase have agreed to continue their existing contract until 2001; more than doubling the magnitude of the original contract. JDS Uniphase will continue to utilize SDL's grating-stabilized 980-nm pump lasers for the production of its high-performance erbium-doped fiber amplifiers (EDFAs).   Because of the on-going demand for more bandwidth, hence the increase in dense wavelength division multiplexing (DWDM) counts, JDS foresees the need for SDL's 980-nm pump laser to provide the power and reliability needed for EDFA designs.   This agreement demonstrates the significant value that SDL pumps deliver to leading manufacturers of EDFAs, commented Donald R. Scifres, CEO and chairman of SDL, Inc. We are ramping to meet the expected demand for pumps in both terrestrial and undersea telecommunications systems.