Micro-opto-electro-mechanical (MOEM) accelerometers using principle of optical coupling between two waveguide structures is proposed. It consists of an antiresonant reflecting optical waveguide structure combined with a cantilever beam. Under acceleration, the output waveguide optical power changes, which is a function of acceleration. The mathematical model of the mechanical sensing element in terms of proof mass, damping, and spring constant is formulated. Here, different aspects such as beam deflection, bending stress, and breakdown acceleration are incorporated into the formulation. Based on the analysis, the optimum mechanical structure for intensity modulated MOEM accelerometers are designed. We report for a typical uniform cantiliver beam of type I (3 mm×3 mm×0.38 µm) accelerometer, mechanical sensitivity of 0.15 µm/g, minimum detectable acceleration of 4.7 µg/ at an optimum power of 500 µW, range of ±25 g, a bandwidth of 1.59 kHz, breakdown acceleration of 5.1×104 g and cross-axis sensitivity of 0.001%. The results in the case of nonuinform beam cantiliver accelerations are sensitivity of 2.15 µm/g, minimum detectable acceleration of 0.27 µg/ range of ±1.8 g, bandwidth of 0.411 kHz, breakdown acceleration of 2987 g and cross-axis sensitivity of 0.001%.
In this paper, we propose a closed loop Micro-Opto-Electro-Mechanical (MOEM) accelerometer employing a nonuniform cantilever beam and an Anti Resonant Reflecting Optical Waveguide (ARROW) on silicon. The MOEM acelerometer consists of a Mach Zehnder Intereferometer (MZI) and an electro-elasto-optic phase modulator to nullify the acceleration induced phase change so as to make the device work in closed loop form. It is shown that MOEM accelerometers with noise equivalent acceleration of 0.255 μg/√Hz, a dynamic range of 160g, scale factor stability of 1.57 ppm/°C and shock survivability of more than 1000 g is feasible.
Micro-Opto-Electro-Mechanical (MOEM) accelerometers employing a cantilever beam and anti resonant reflecting optical waveguide (ARROW) on a silicon is analyzed. Two types of MOEM accelerometers and a closed loop operation that can enhance the performance significantly compared to MEMS accelerometer is presented. As a typical example our study shows a MOEM accelerometer with a minimum detectable acceleration of 0.255 μ g/√Hz, a dynamic range of 160g, scale factor stability of 1.57 ppm/°c and shock survivability of more than 1000 g.
Integrated optics combined with micro-electro mechanical system (MEMS) technology offer enormous potential to improve sensitivity and performance capabilities of new sensors. In this paper, an analysis is carried out to find the feasibility and design concept of a Micro-Opto-Electro-Mechanical (MOEM) accelerometer consisting of integrated optic Mach-Zehnder interferometer, whose sensing arm is attached to a micromachined vibrating cantilever or a bridge. The analysis consists of determining changes in phase shift due to acceleration-induced refractive index and optical path length variation of MachZehender interferometer. A noise analysis is carried out to find the fundamental performance limit of different sensor configurations.
An ideal fiber optic rotation rate sensor is shot noise limited. In present day technology, the maximum power that can be received at the detector end of the sensor is of the order of 1 to 10 µw. This corresponds to a minimum detectable rotation rate of 0.1 deg/hr to 0.035 deg/hr for a sensing coil length of 500 meters and radius 10 cm, operated at 1.3 µm wavelength. However a practical rotation sensor is limited by thermal noise of the load resistance, back scattering noise in optical fiber, polarization induced noise, source intensity noise and noise in processing electronics. These noise sources cause long term offset at sensor output resulting in drift. We have analyzed and estimated the various noise sources with an objective to achieve optimum performance of a fiber optic rotation sensor. The noise equivalent rotation rate due to various sources has been calculated for different values of optical power, wavelength of operation, length of the fiber and detection bandwidth. Polarization filtering, coherence length of the optical sources, phase modulator amplitude and frequency stability were analyzed to yield optimal system performance. Other effects which cause drift in rotation sensor such as Faraday effect and Kerr effect have also been considered.
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