Micromachining of optical fiber using reactive ion etching and its application

Reactive ion etching (RIE) experiments were performed on an optical fiber which was loaded onto an rf cathode and exposed to a low-pressure discharge of CF₄ gas. This method enables the fabrication of slender optical fibers with almost uniform diameter in specified regions, but has no significant effect on the core of the fiber which is the propagation path of the signal. An optic variable attenuator was demonstrated using glycerine as an additional cladding on a thinned optical fiber of diameter 22 μm. The glycerine temperature change of 40°C caused an attenuation of 12 dB at 1550 nm. The application of a micromachined single-mode grating fiber (10/125 μm, grating wavelength: 1550 nm) to an optical fiber sensor for detecting the refractive indices of surrounding materials was examined.