This paper presents a review of silicon micromachined accelerometers and gyroscopes. Following a brief introduction to their operating principles and specifications, various device structures, fabrication, technologies, device designs, packaging, and interface electronics issues, along with the present status in the commercialization of micromachined inertial sensors, are discussed. Inertial sensors have seen a steady improvement in their performance, and today, microaccelerometers can resolve accelerations in the micro-g range, while the performance of gyroscopes has improved by a factor of 10/spl times/ every two years during the past eight years. This impressive drive to higher performance, lower cost, greater functionality, higher levels of integration, and higher volume will continue as new fabrication, circuit, and packaging techniques are developed to meet the ever increasing demand for inertial sensors.

/pdf/micromachined-inertial-sensors-esf6197vdc.pdf

Micromachined inertial sensors

Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

http://ieeexplore.ieee.org/iel5/3/23094/01073023.pdf

Statistical optics

A method and apparatus for performing optical imaging on a sample wherein longitudinal scanning or positioning in the sample is provided by either varying relative optical path lengths for an optical path leading to the sample and to a reference reflector, or by varying an optical characteristic of the output from an optical source applied to the apparatus. Transverse scanning in one or two dimensions is provided on the sample by providing controlled relative movement between the sample and a probe module in such direction and/or by steering optical radiation in the probe module to a selected transverse position. The probe module may be an external module or may be an endoscope or angioscope utilized for scanning internal channels. Multiple optical paths may be provided for parallel scanning and focus may be enhanced by varying the focal point in the sample in synchronism with longitudinal scanning of the sample.

Method and apparatus for optical imaging with means for controlling the longitudinal range of the sample

This work presents an overview of progress and developments in the field of fiber optic sensor technology, highlighting the major issues underpinning recent research and illustrating a number of important applications and key areas of effective fiber optic sensor development.

http://snake.persiangig.com/document/sensor1.pdf

Fiber optic sensor technology: an overview

The current state of the art of optical fiber sensors is reviewed. The principles of operation are detailed and the various types of fiber sensors are outlined. Achievable performance and limitations are discussed and a description of technology used to fabricate the sensor is presented. The characteristics of acoustic, magnetic, gyro, laser diode, and other sensors are described. Trends in the development of this sensor technology and expected application areas are briefly outlined.

Optical fiber sensor technology

Principle of the fibre-optic gyro reciprocity of a fibre ring interferometer backreflection and backscattering analysis of polarization non-reciprocities with broadband source and high-birefringence fibre transient related drift and noise truly non-reciprocal effects scale factor accuracy alternative approaches for the I-FOG applications and trends.

The fiber-optic gyroscope

A new all-fiber gyroscope is described. All components are constructed directly on a single continuous optical fiber, removing localized sources of reflection. A laser-diode source is used to reduce coherent scattering effects. Proper choice of modulation frequency is shown to reduce instabilities further. Long-term stability at rest of better than 0.2 masculine/h is observed with 30-sec integration time.

All-single-mode fiber-optic gyroscope with long-term stability

We present an optical fiber gyroscope that, for the first time, is composed completely of single-mode fiber-optic components. This system has increased simplicity and stability over previous bulk-optic designs and has the potential for very high rotation sensitivity.

All-single-mode fiber-optic gyroscope.

Apparatus and method of manufacture for coupling optical power between two strands of fiber optic material in a given direction of propagation. The coupler employs generally parallel, intersecting strands of fiber optic material having the cladding removed on one side thereof to within a few microns of the fiber cores in the region of intersection to permit light transfer between the strands.

Fiber optic directional coupler

A multiple-point temperature sensor, with optic fibers, uses the effect of variation in the birefringence in a birefringent optic fiber as a function of temperature. This sensor has a plane polarized, wide spectrum source coupled to a monomode optic fiber for preservation of polarization, along one of the neutral axes, with weak coupling points distributed along this fiber. A polarizer at 45° to the neutral axes of the fiber is placed at the output of this sensing fiber. The output radiation is analyzed by spectroscopy, for example in a Michelson interferometer, capable of being swept, associated with a detector. The interferometer shifts needed to detect the extreme values of the transmission function are measurements of temperature deviations.

Herve Lefevre

Papers

The fiber-optic gyroscope

All-single-mode fiber-optic gyroscope with long-term stability

All-single-mode fiber-optic gyroscope.

Fiber optic directional coupler

Multiple-point temperature sensor using optic fibers