In dual Mach-Zehnder interferometer (DMZI) system, polarization induced phase shift (PIPS) leads to a big location error. Traditional approaches adopt polarization controller (PC) to eliminate PIPS by controlling polarization state (PS) of light source. Through establishing the influence model of input light PS and equivalent polarization parameters of sensing cable on interference signals, an approach using a simplified polarization controller (PC) to obtain high location accuracy is proposed. The simplified PC is composed of a polarizer and a fiber-fused half-wave plate and can provide a linearly polarized light with azimuth angle controlled. Simulation and experiment indicate that the proposed method and PC design not only has capability of eliminating PIPS, but also has the benefits of low cost and easy control.
A micro acoustic sensor with inclined fibers was proposed to improve its sensitivity. In order to get the highest
sensitivity within the micro structure, the relative positions of elements in sensor should be exactly located; especially
the distance between fibers and membrane should be optimum. A packaging technology for this micro sensor
assemblage and test is introduced. It is based on a packaging system composed of three parts: distance adjusting,
intensity collection and data analysis. The distance adjusting part increases the operating distance with a step of 2μm.
Meanwhile the received power is recorded by intensity collection part on line to get the intensity characteristic curve.
Through the data analysis part, sensitivity curve, optimum operating distance, the highest sensitivity and optimum
received power of the proposed acoustic sensor are got. An experiment was implemented to assemble and test a sensor
whose angle between two fibers was 60° by the proposed packaging system. Its optimum operating distance and highest
sensitivity were analyzed to be 30μm and 2.49μW/μm. The sensitivity of packaged sensor to standard acoustic signal is
16mV/Pa and SNR is tested to be 54dB.
To measure the vibration of micro-structure, a scheme of sensor based on MOEMS (Micro-Optic-Electro-Mechanical
System) with fiber-optic readout was proposed, and its mathematical model was deduced. Single-fiber readout structure
and a micro-structure fixed in the front of the sensor were used. The micro-structure vibrated as the measured object
moved, and its vibration caused the change of light intensity. The sensor detected vibration displacement by receiving
the light intensity. As a result of single-fiber structure and parameters optimization of micro-structure, compared with
other fiber readout structures, this system has the advantages of high sensitivity and miniaturization which is easier to
match with fiber system because of single-fiber structure and parameters optimization of micro-structure. The response
behaviors of the system to the piezoelectric ceramics excitation were studied through the experiments. And it could
detect the vibration displacement of 0.18nm.
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