Temperature sensing to as low as 80 K was demonstrated with 1.55-μm fiber Bragg gratings. The gratings were bonded on substrates to increase sensitivity, and a shift of the reflection wavelength was measured. The temperature sensitivity was 0.02 nm/K at 100 K when an aluminum substrate was used and 0.04 nm/K at 100 K when a poly(methyl methacrylate) substrate was used. These values are smaller than those at room temperature because of the nonlinearity of both the thermal expansion and the thermo-optic effect. Extension to the liquid helium temperature is also discussed.

We propose a method for optimizing the process of iteratively binarizing digital amplitude holograms by utilizing the effect of adding energy to the reconstructed signal window from the hologram. For this purpose, we introduce a parameter called the energy factor and show that the performance of the iterative binarization process can be greatly enhanced if the value of the energy factor is properly chosen. Finally, we show that the optimal values of this energy factor can be estimated with an analytical function for different computational costs.

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The effectiveness of artificial life is investigated from an engineering point of view. A system (named S-system) of function-discovery using a bug type of artificial life is proposed in this study. Some functions are extracted by the system. The chromosome of a bug consists of functions, constants and variables. A tree structure is used for the expression of the chromosome. Some observation data are provided for the bugs. After obtaining the data, they reproduce. The concept of sexual / asexual reproduction is introduced in this study. The number of homogeneous bugs is limited for a variety of species. These ideas are very effective for a function-search. A part of the chromosome changes by mutation. As the generation proceeds, the bugs with the function in agreement with the observation data survive selectively, and finally determine the true function. For the validity of this system, some data which obey the known laws have been given for the bugs. The bugs have evolved and discovered some functions in agreement with the laws. As for an unknown function, observation data on glossiness have been provided. They have also discovered the function. In addition, they have determined the multiple curves included in the image data. The S-system has the characteristics that the solution tends to converge and stabilizes in comparison with Genetic Programming. Moreover, the form of the function is relatively simple.

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