It is not generally realized that Japanese Prime Minister Yasuhiro Nakasone has achieved a breakthrough regarding the transfer of Japanese technology to the US Department of Defense for military purposes. Like opening Pandora's box, this action may have long-range implications in the current US-dominated noncommunist arms market.
Key areas for technology transfer include:
* Fiber optics. Fujitsu, Japan's computer industry leader, has been the leader in these ultra-high-speed communication links, utilizing light waves, that the Soviets cannot eavesdrop or jam. This would be extremely attractive to Pentagon planners in information security.
* Ferrite paint. Long the top manufacturer in consumer magnetic recording tape, the TDK firm has been developing ferrite materials that can be used to coat the exotic radar-proof ''stealth bomber.''
* Microchips. The Pentagon wants access to the latest Hitachi and Mitsubishi random-access memory chips for increased efficiency in their electronics gear.
The Pentagon had long complained of a one-way technology transfer and had pressured the Japanese government bound by the umbilical cord of the US-Japan Security Treaty for access to high-technology information. During the 18 -month-long negotiations, the main obstacle has been the previous prime minister's opposition to any change in the Japanese weapons export ban to all nations. Also, there exists Article 9 of the US-written Japanese Constitution that renounces war as a sovereign right.
Prime Minister Nakasone has made his political views quite evident. A man close to President Reagan's heart, he blames the Soviets for increasing tensions throughout Asia, including expanding naval facilities on the Vietnamese coast and a garrison build-up on the disputed Kurile Islands.
Mr. Nakasone wants a 6.5 percent rise in the defense budget - this in the face of spiraling Japanese government deficits and the slowing of the steel and other ''smokestack'' sectors of the economy. He envisions taking over surveillance of an area 1,000 miles south of Japan, meaning outlays in aircraft, destroyers, communications. Whether he will even contemplate extending Japanese patrols north of Hokkaido around the fringes of the Soviet Far East remains to be seen.
The powerful Japanese business group, Keidanren, and the three major defense contractors (Mitsubishi, Kawasaki, and Ishikawajima-Harima) all favor lifting the weapons export ban. So far most of Japanese arms production - according to Keidanren, less than .5 percent of overall industrial output is defense-related - has been in the way of building under license from US firms. Ironically, the experience in producing F-4 Phantoms and F-15 Eagles (more than half of the nascent aircraft industry is tied to defense) has laid the foundation for Mitsubishi's entry into the computer civilian market with their Diamond I.
Because of the longstanding weapons export ban, Japanese companies had no incentive to plow profits into research and development. Less than 1 percent of the Japanese defense budget is earmarked for R&D, as opposed to nearly 10 percent of the US. Keidanren favors doubling this to 2 percent. Indigenous Japanese arms, such as the Type-74 tank and F-1 support fighter, impressed Western experts, but are no comparison to US/NATO equivalents. While it is true that the Japanese have benefited from one-way technology transfer from the US, much of the technology is around a decade old. Except for the state-of-the-art F-15 Eagle, required to chase MIG-25 Foxbats prowling in Japanese airspace, much of the Japanese arsenal remains obsolescent by US/NATO standards.
According to the Pentagon, it is in advanced integrated circuits and materials research that Japanese firms have excelled. Instead of heavy, expensive arms like tanks and artillery, the Japanese could become a major factor in light, cheap weapons packed with electronic circuitry, like Exocet-type air-to-surface missiles. Also, they could make add-on peripherals to US-made arms, such as battlefield communication gear. Their extensive robotics research could be channeled into military uses in unmanned ''intelligent'' submarines and surveillance aircraft.
Most significantly, what has been overlooked is the awarding of a US Air Force contract late last year to Kikusui Electronics Corporation - the first direct deal between a Japanese firm and the US military. For an order of 8,000 oscilloscopes, Kikusui beat out Tektronix, the Oregon-based world leader in oscilloscope technology. Although used in military electronics, oscilloscopes were not considered weapons by the Japanese government and so were exempt from the arms export ban.
The question remains: Where does the military application begin and the civilian use end? And how much can the arms export ban be stretched without a change in Article 9?
If Nakasone transforms his blunt hawkish defense views into reality, and if the world's ''mini-Japans'' (South Korea, Taiwan, Singapore) continue to make inroads in markets where Japanese industry now dominates, some Japanese manufacturers may find themselves irresistibly lured into the international arms bazaar, thus injecting an unpredictable new factor into the intertwined defense and economic links across the Pacific.