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This paper investigates experimentally the change of the refractive index, due to forces such as pulling and pure bending, in an optical fiber fabricated by the CVD technique. It is found that this phenomenon can be interpreted in terms of a simple model of the fiber, that is, a mechanically homogeneous circular rod. We compare the effect of the refractive-index change and that of a geometrical deformation of the fiber on transmission characteristics. A new method based on photoelasticity is also proposed to measure the curvature distribution of a fiber whose axis is deformed by external forces.

Pulse spreading in a single-mode optical fiber is discussed taking into account the third-order dispersion term of the waveguide when the light source is modulated by a Gaussian pulse. A general expression for the pulse shape is analytically obtained, and an asymptotic approximation is used when the third-order dispersion term is small. It is also shown that the pulse width is no longer proportional to the guide length when the third-order dispersion term becomes large.

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Lauroylamidopropylbetaine (LPB) has good cleaning and foaming performance with excellent low skin irritation. We have investigated the relationship between cleaning performance and foaming properties of aqueous solutions containing binary and ternary LPB/nonionic surfactant systems. Foaming properties were evaluated by observing dynamic surface tension and aqueous core thickness of a vertical foam film measured by Fourier transform infrared spectroscopy. The LPB/lauroyldiethanolamide (LDE) system has a positive synergistic effect on cleaning performance and foam stability, estimated from the grease removal test and dishwashing test for a light-duty detergent. However, this system shows very poor initial foam performance in both the sponge test and Ross-Miles foam test. This disadvantage of the LPB/LDE system was improved using C12En (polyoxyethylene dodecyl ethers). Addition of C12En promoted dynamic surface tension lowering, indicating an improvement in the initial foaming performance, while maintaining cleaning performance and foam durability. Thus, the LPB/LDE/C12En ternary system has an excellent cleaning and foam performance as a light-duty liquid detergent.Lauroylamidopropylbetaine (LPB) is an amphoteric surfactant obtained from natural resources such as fatty methyl esters or fatty acids (1). Since LPB has good cleaning and foaming performance with low skin irritation, it has been widely used in shampoos and light-duty detergents along with anionic surfactants (2,3). Many studies of anionic/amphoteric surfactant mixed systems have been reported (4-8). Lauroyldiethanolamide (LDE) has also been widely used in many detergents as a nonionic surfactant for increasing foaming performance (9). We have studied the relationship between cleaning performance and foam film properties of LPB/nonionic surfactant binary mixed systems and compared properties against LPB and alkyl ether sulfate (AES) as the anionic surfactant. Superior cleaning performance and foaming properties as a light-duty liquid detergent were observed, particularly for a LPB/LDE/nonionic surfactant ternary system. This paper discusses the synergistic effect of the mixed system using foam formation and foam stability methods. Foam formation was estimated by dynamic surface tension based on the maximal bubble pressure method, and foam stability was estimated by evaluating the aqueous core thickness of vertical foam films measured by Fourier transform infrared (FT-IR) spectroscopy. EXPERIMENTAL PROCEDURESMaterials. Surfactants were commercial products from Lion Co., Ltd. (Tokyo, Japan). LPB [C 11 H 23 CONHC 3 H 6 N + -(CH 3 ) 2 CH 2 COO − , ENAGICOL L30-B, >95%], LDE [C 11 H 23 CON(C 2 H 4 OH) 2 , >95%], polyoxyethylene dodecyl ethers C12E5, C12E9, C12E15 [C 12 H 25 O(C 2 H 4 O) n H, where n = 5, 9, or 15, >95%) and trioxyethylene dodecyl sulfate AE3S [C 12 H 25 O(C 2 H 4 O) 3 SO 3 Na, >95%] were used without further purification.Grease removal test. This grease removal test, also known as the cup test, determines the ability to remove greasy soils fro...