In this article, we review optical MEMS accelerometers with a particular focus on sensing techniques and interrogation methods. Optical accelerometers find use in various application domains ranging from microgravity to inertial navigation to vibration sensing. The performance of an accelerometer is quantified in terms of its range, bandwidth, sensitivity, and resolution. The combination of sensing technique and interrogation method determines the optical accelerometer’s performance. This article presents a classification in terms of guided-wave and free-space based optical sensing techniques used in acceleration measurement and their review. In free-space based sensing techniques, light propagating in free-space interacts with the mechanical structure resulting in modification of light properties at the receiver. In guided-wave based sensing techniques, light interaction with the mechanical structure is confined to the waveguide. Also, the different interrogation methods used in optical MEMS accelerometers are reviewed. The interrogation methods are classified as based on intensity modulation or frequency modulation of the optical signal received from sensor. In intensity-modulation based interrogation, light intensity at output is the measurand and, the cost and complexity of this class of methods is lower. In frequency-modulation based interrogation, the frequency or phase of the optical signal at the output is the measurand. Further, a high-resolution optical MEMS accelerometer based on waveguide Bragg gratings is described. A combination of free-space based sensing and intensity-modulation based interrogation methods will be suitable for consumer-grade accelerometer applications. For high-resolution applications like tactical and navigation grades, a combination of guided-wave sensing and frequency-modulation based interrogation methods would be appropriate.

In this competitive world, websites are considered to be a key aspect of any organization’s competitiveness. In addition to visual esthetics, usability of a website is a strong determinant for user’s satisfaction and pleasure. However, lack of appropriate techniques and attributes for measuring usability may constrain the usefulness of a website. To address this issue, we conduct a statistical study to evaluate the usability and accessibility levels of three popular academic websites based on human (user) perception. Two types of usability evaluation techniques were employed in this study. First one is Questionnaire-based evaluation and second one is performance-based evaluation. Usability assessment was performed by analyzing the results from the observed task success rates, task completion times, post-task satisfaction ratings and feedback. We also investigate the possibility of there being any impact of task completion times on participant’s satisfaction levels. The results of the questionnaire based evaluation were observed to be consistent with the results of performance-based evaluation. Accessibility evaluation was carried out by testing the degree of compliance of the web pages as per WCAG 2.0 guidelines