TOKYO, Sept. 3 -- Pacific Gateway Exchange Inc. and KDD Submarine Cable Systems Inc., part of Japan's KDD Corp., plan to create a joint venture to build an undersea fiber optic network to connect various parts of Japan. The cable network will link metropolitan Tokyo with existing international fiber optic cable landing points in Chiba and Kanagawa prefectures.The new network is designed to offer telecommunications carriers a high-capacity, low-cost route from the landing points on Japan's coast to operations centers in central Tokyo. At present carriers must purchase conventional domestic leased lines to connect landing points to the centers. The first stage of the network will link Tokyo to the Chikura/Maruyama submarine cable stations, and is scheduled to be completed by mid-2000.