The JTEC panel visited three Japanese optical sensor manufacturers: Hitachi Cable, Hoya Glass, and Furukawa Cable. One of the panel's most instructive site visits on the subject of optical sensing was to Hitachi Cable (see site report in Appendix D). There, Hitachi representatives told the panel that the company has both distributed temperature sensors and fiber-optic gyroscopes as commercial products; Hitachi is probably the largest FOG producer in the world, with production capability for intermediate grade FOGs (1deg. to 10 deg./hr, 100 deg./sec) of 2,500 units/month/shift; the Hitachi representatives indicated that they normally run two 12-hour shifts a day. Hitachi Cable's distributed temperature sensor is used to detect hot-spots in motor windings and infrastructure ducts.

During the Hoya Glass site visit (see site report in Appendix D), panelists were told that the company is making fluoride fibers for IR transmission, with applications in laser surgery and temperature sensing. Hoya Glass is also producing a special flint glass fiber for magnetic field sensing. Company officials at Furukawa Cable (see site report in Appendix D) indicated that the company is producing a fiber with an offset core for methane sensing. With the core offset, the evanescent wave can interrogate the region surrounding the fiber. For a 20 cm fiber length, the panel's hosts reported obtaining 1- and 2-dB signal changes for, respectively, 50% and 100% methane surrounding the fiber.

To obtain a more complete evaluation of the Japanese optical sensing capability, JTEC performed an extensive literature search. As noted earlier, the United States leads all other nations by a wide margin in number of optical sensor publications. Of those listed in the INSPEC Database, approximately 6,000 articles published during the past decade, about 50% originated in the United States. Considering the number of times a U.S.-based organization holds the world record for performance, as Table 6.5 shows, one must conclude that most of the leading research is being done in the United States; however, as noted in Figure 6.4 and discussed above, Japanese scientists do produce more patents than U.S. scientists.

Analysis of the publication record can be taken deeper. Figures 6.9 and 6.10 show separately a breakdown into the 12 different categories of the optical sensor publications shown earlier in Figure 6.5, for the United States and Asia (where most publications are Japanese).

Comparison of Sensor Technology Activities

To more clearly compare the activity levels of U.S. and Japanese R&D in optical sensors, Figures 6.11 to 6.19 present the publication chronology separately for each of the twelve categories in the United States, Asia (dominated by Japan), and Europe (presented but not analyzed).

The category enabling science and components is the largest area for both the United States and Asia and has shown steady growth over the last ten years. Networks and instrumentation is the second largest area; there has been a sharper increase in publications in the United States than in Japan, due to the large increase in U.S. defense R&D on network and cascade sensors, focused on providing more cost-effective systems. Ignoring the category other, which incorporates pressure, flow, displacement, and vibration sensors, the third largest category is chemical sensing. Here again, the U.S. activity has increased sharply, driven by concerns for the environment and the need to be able to "measure" in order to "change." The Japanese effort has not grown as rapidly.

Fig. 6.9. U.S. publication chronology by sensor type.

Fig. 6.10. Asian publication chronology by sensor type.

Fig. 6.11. U.S./Europe/Asia publication comparison by sensor category: enabling science/components.

Fig. 6.12. U.S./Europe/Asia publication comparison by sensor category: networks & instrumentation.

Fig. 6.13. U.S./Europe/Asia publication comparison by sensor category: chemical sensors. Temperature sensing in both geographic regions has grown modestly and steadily with no apparent differences in relative output. Strain sensing is clearly dominated by U.S. organizations and is growing rapidly, likely as a result of "smart structure" efforts started in military laboratories in the late '80s that have gradually shifted to the civilian infrastructure over the past few years. Biomedical sensing shows modest growth in both geographic areas, and the ratio of publications appears to be that of the relative populations of the two countries. This ratio is not maintained for electric and magnetic field sensing; here, Japan produces approximately the same number of publications as U.S. researchers, and there is a hint of an increase in Japanese work and a decrease in U.S. work. This may well reflect the greater use in Japan of electric power for trains and subways and the corresponding need to provide sensors to monitor this infrastructure. Rotation sensing also appears to have slightly higher relative effort in Japan. Overall, however, with the exception of electric and magnetic sensing, it appears the United States has a larger R&D effort in all sensing areas.

Fig. 6.14. U.S./Europe/Asia publication comparison by sensor category: temperature sensors.

Fig. 6.15. U.S./Europe/Asia publication comparison by sensor category: strain sensors.

Fig. 6.16. U.S./Europe/Asia publication comparison by sensor category: biomedical sensors.

Fig. 6.17. U.S./Europe/Asia publication comparison by sensor category: electric/magnetic sensors.

Fig. 6.18. U.S./Europe/Asia publication comparison by sensor category: rotation sensors.

Fig. 6.19. U.S./Europe/Asia publication comparison by sensor category: other sensors.

Comparison of Commercial Activities

Figure 6.20 shows data regarding the geographic distribution of companies selling optical sensors. Approximately 100 sensor companies were identified, nearly 50% being in the United States and less than 10% in Japan. This probably reflects the facts that this technology and market are very fragmented and that many small entrepreneurial companies are active, particularly in the United States. The active companies in Japan tend to be large, such as Hitachi, Hoya, Tokyo Electric, and Sumitomo, to name a few.

Fig. 6.20. Geographic distribution of companies producing optical sensors (UK Optical Sensors Collaborative Association 1994).

It is interesting to speculate regarding the observation that Hitachi is commercially pursuing the intermediate gyroscope market by concentrating on manufacturing for the large-volume automotive market. The U.S. companies attempting to reduce gyroscope costs under the U.S. Air Force Man-Tech programs, notably Honeywell and Litton, are working toward navigational grade (higher performance) units for markets with much smaller potential volume. Over the next three years these programs should generate about 30,000 units (Elwood 1995); Hitachi can currently produce that number of units in a single year. Like Japan's application of optoelectronic data storage technology to compact disk and archival mass storage products, this appears to be another example of Japan's market strategy of targeting consumer goods for high-volume, medium-grade, low-cost applications of cutting-edge electronics and optoelectronics technologies.

Published: February 1996; WTEC Hyper-Librarian