Research Of Off-axis Fiber Optic Rotary Joint

In this paper, a model of new off-axis fiber optic rotary joint (FORJ) is established. It includes input device, annular substrate and output device. The input device includes a fiber collimator and a deflecting grating, which can outputs parallel beams. There is a hollow core in the center of annular substrate. With tapered reflective surface and reflective plane, the annular substrate is applied to control the beams transmitting along the circumferential direction. An outputting window is placed in the tapered surface and parallel to the reflective plane, and beams in the substrate can be output through the window. The output device includes an optical deflecting element, a telescope system and a collimator. The optical deflecting element is applied to deflect beams perpendicular to the rotary axis of the joint. The telescope system is used to decrease the beam diameter, and maintain the beams as parallel rays. The beams in the substrate have been simulated by FRED optical software , and the results show that optical signal can be transmitted into the substrate from continuous changing incident position and output in a fixed area. The transfer efficiency of the off-axis FORJ is more than 10%.The major achievements in this dissertation are as follows:(1) A model of the substrate with tapered reflective surface and reflective plane was designed. The off-axis optical transmitting path in the substrate has been calculated, and the formula was calculated to get a constraint condition of the parameters in the substrate. The optical deflecting element has been analyzed as well as the diameter and the separation of output window. The result shows that multi-channel signal can be transmitted in one substrate.(2) The beam deflection principle of transmission-tape radial blazed grating was analyzed. The transmission function of radial grating indicates that a common blazed grating could replace the radial grating under a small angle. Meanwhile the diffraction deviation of common grating compared to the radial grating has been calculated.(3) Both of the single channel rotary joint model and the double-direction multi-channel rotary joint have been structured. Three methods have been analyzed to control the outputting optical beams. (4) Two schemes of double-grating unit and grating-prism combined unit have been simulated by the optical software of FRED. The propagation path and tilted angles in these schemes have been recorded, and the data show that the beam can transmit dynamically in the annular substrate into a fixed area. At the same time the effects of source deviation have been recorded, and the results show that the effects of incidence angle and radial shift are bigger than others errors. Finally, the feasibility of multi-channel off-axis FORJ in one substrate has been verified.