Fiber-optic bend sensor using LP21 mode operation.

A novel fiber-optic bending sensor based upon the propagation of LP21 mode is demonstrated. The sensor, comprised of an S-bend fiber on an elastic film, measures LP21 mode specklegram rotation, which increments linearly with bending angle by the stress-optic effect. The sensor is capable of experimentally achieving a sensitivity as high as 4.13 rad/m(-1). The theoretical analysis of the sensor, which is a combination of fiber coupled-mode theory and elastic-optic theory, validates the accuracy of the sensor. The sensor is also shown to be temperature-immune, and can detect both bending direction and bending angle with a large dynamic range. Furthermore, the sensor implementation incorporates inexpensive single-mode fiber at 650 nm for few-mode operation, enabling low-loss transmission and compatibility with existing interfaces.

Effects of twisting and bending on LP21 mode propagation in optical fiber.

Twisting and bending characteristics of low-multimode LP21 mode propagation in optical fibers is presented for the first time. Theoretical fiber mode modeling, combining geometrical rotation with opto-elastic effects, demonstrates that the propagation of the LP21 mode is bending-effect-immune. Experimental testing verifies that the LP21 mode specklegram rotates 0.9112 of the fiber twist angle in a fused silica fiber, independent of any fiber bending. This characteristic allows for the LP21 mode to be highly applicable in fiber specklegram sensors.

[Studies on the GS impregnated calcium sulfate implants].

The gentamicin sulfate carried calcium sulfate (GSCS) implants were fabricated by the coagulating method, and the release rate of the gentamicin tested by UV-spectrometer and the absorbing rate of the calcium sulfate carrier in vitro were studied. The release patterns of two types of GSCS were compared. The trend of daily weight loss of GSCS was found being similar to that of pure calcium sulfate, which suggested that the gentamicin part has little effect on the absorbing pattern of calcium sulfate. The release rate of gentamicin is controlled by the erosion rate of calcium sulfate, so GSCS with different amount of gentamicin has the same release patterns. The DRP value of ED is higher than that of CO during the early stage, while the DRP value of ED is lower than that of CO during the late stage. The GSCS samples were implanted into the defect mold on the radii of the rabbits to investigate the potential for the use of GSCS implants as bone fillers, and the results revealed that new bone had been induced in a great part of the defect at 14 weeks after operation.