Fault analysis: optical performance investigation of fiber connections with imperfect physical contact.
We investigated the insertion and return losses of optical fiber connections with various air-filled gaps. Such gaps might occur when a fiber connection using physical contact unexpectedly fails, resulting in imperfect physical contact. The optical performance of these fiber connections depends on wavelength and gap size. We revealed that the measured optical performance of fiber connections with an imperfect physical contact, i.e., with an air-filled gap, might deteriorate to ~18 dB for insertion loss and 9.4 dB for return loss at worst.
Optical Fiber Connectors, Splices, and Jointing Technology
In recent years the state of the art of optical fiber technology has progressed to where the achievable attenuation levels for the fibers are very near the limitations due to Rayleigh scattering. As a result, optical fibers, and particularly single-mode fibers, can be routinely fabricated with attenuation levels of about 0.5 dB/km at 1300 nm and 0.25 dB/km at 1550 nm. Employing these fibers in lightwave systems requires precise jointing devices such as connectors and splices. Considering the small size of the fiber cores, less than 10 μm in diameter for single-mode fibers and less than 100 μm for multimode fibers, it is not surprising that these components can easily introduce high optical losses. Furthermore, since single-mode fibers have practically unlimited bandwidth, they have recently become the favorite choice for most of the lightwave systems presently being designed for telecommunication networks and in the future may be used in local area networks as well. To provide low-loss connectors and splices for these single-mode fibers, alignment accuracies in the submicrometer range are required, and these sub- micrometer alignments must be both reliable and cost-effective. Achieving these goals is presently the challenge facing the jointing technologist.
The Prevalence of Dietary Supplement Use among College Students: A Nationwide Survey in Japan
To clarify the prevalence of dietary supplement use among college students, we conducted Internet-based nationwide questionnaire surveys with 157,595 Japanese college students aged between 18 to 24 years old who were registrants of Macromill Inc. (Tokyo, Japan). Among the 9066 respondents (response rate 5.8%), 16.8% were currently using dietary supplements. The prevalence of dietary supplement use did not differ significantly between males (17.1%) and females (16.7%). However, it increased according to their grade (13.1% to 20.5%), and it was higher in medical and pharmaceutical college students (22.0%) compared to others (16.7%). The main purpose of dietary supplement use was for the health benefits in both males and females. Other reasons were to build muscle in males, and as a beauty supplement and for weight loss in females. According to the purpose of dietary supplement use, the most commonly-used dietary supplements were vitamin/mineral supplements in both males and females, then protein and weight loss supplements in males and females, respectively. Although most students obtained information about dietary supplements via the Internet, they typically purchased the supplements from drug stores. Of the students surveyed, 7.5% who were currently using or used to use dietary supplements experienced adverse effects, with no significant difference between genders (8.8% in male, 7.0% in female). In conclusion, the prevalence of dietary supplement use increased with grade among college students in Japan. Some of them experienced adverse effects. Education may be important to prevent adverse effects resulting from supplement use in college.