Optical sensing R&D can be broken into twelve topical categories: ten sensor types (chemical, temperature, strain, biomedical, electrical and magnetic, rotation, vibration, displacement, pressure, and flow) and two general categories (enabling science and components, and networks and instrumentation). The status of the optical fibers used in sensors is a distinct, but related, topic of interest to this study.
In both Japan and the United States there is a growing interest in optical sensing. Japan's Optoelectronics Industry and Technology Development Association (OITDA) indicates the sensor market is currently worth approximately $920 million a year (OITDA 1994). The North American Optoelectronics Industry Development Association (OIDA, private communication with the author) predicts a growth potential reaching approximately $5 billion by the first decade of the next century. Currently, the largest activities in the sensor market are chemical gas sensing, medical pressure sensing, automotive rotation and direction sensing, and temperature sensing. The main growth areas are expected to be chemical sensing, mostly related to environmental sensing, and biomedical sensing, oriented at first toward point-of-care sensing, but evolving to home sensing. Strain sensing associated with "smart structures" is also expected to be an area of considerable growth.
Optical sensor researchers have already demonstrated and/or delivered a technique for sensing virtually every measurand of interest. For the most part, they have based their work on optical fiber components and techniques resulting from the optical fiber communications revolution. Sensitivity levels of optical sensors generally exceed the values required by present applications. In addition to sensitivity, optical sensors also offer freedom from electrical and magnetic interference. As with most sensitive measurement techniques, however, interference from other competing effects can often be a problem -- for example, a strain sensor may be temperature-dependent. Much work has been done to mitigate these competing effects, and many of these interferences have been overcome. Research trends indicate that the most promising sensors are interferometric types of sensors, fiber Bragg grating sensors, and evanescent wave sensors, including two-photon types.
A study of the published data and a review of the JTEC panel's site visits leads to several conclusions of national interest regarding this technology. Leading research is being done primarily in the United States. The U.S. "national laboratories" such as the Naval Research Laboratory (NRL) and the National Institute of Standards and Technology (NIST) have done much of the leading work.
In the commercial arena, the relative national standings are mixed. The United States has commercial leadership in chemical, strain, biomedical, and pressure sensing, while Japanese companies lead in commercial rotation and electric and magnetic sensing. The U.S. commercial arena is populated with many small companies, a number of which have recently been purchased by foreign national companies; for example, the French company Photonetics purchased Metricor, and the Swedish company ABB purchased the Westinghouse optical sensor group. In Japan, the optical sensor effort comes mostly from divisions of large companies such as Hitachi Cable and Sumitomo Electric. These companies have focused on potentially high-volume applications with lower performance requirements; a notable example is Hitachi's fiber-optic gyroscope (FOG), designed for high-volume automotive applications.