Diaphragm Type Ultra Miniature Optical Fiber Pressure Sensor with Sleeve

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(1) Polycrystalline silicon spacer which keeps the gap between a fiber and a diaphragm at few um is formed in the grave formed on the silicon substrate and polished out besides the spacer by CMP (Chemical Mechanical Polishing). This method can make the diaphragm surface be a mirror state. CCP (Capacitive Coupling Plasma) etching is used in order to form the sleeve with a vertical wall.(2) The method of mounting the diaphragm on the end side of the optical fiber has been developed. The concrete way is that the 125 μm multi mode optical fiber with an half mirror is set on the vertical micro moving mechanical system and inserted in the sleeve of the diaphragm under the microscope. In the next step, the sleeve is fixed by the violet adhesion resin which is supplied by the glass micro capillary.(3) 1.3 μm laser light through the 1 x 2 photo coupler is injected into the fiber and the reflected light from the diaphragm is inputted into the photo detector. The sensor of the diaphragm applied the pressure from 0 to 150 mmHg represented a sinusoidal response caused by optical interference. From this result, it is proved that the fabricated pressure sensor satisfies the performance to measure blood pressure for medical applications.