Papers by Author: Niveen Farid

Abstract: The present work discusses the optical fiber strain induced by the thermal and the mechanical effects. Two different optical fibers of different core diameters were used in the study. The thermal effect was induced by temperature control system in order to raise optical fibers temperatures to controlled values. The mechanical stress was induced on the optical fibers by a micro mechanical stage. The sensitivity of the optical fibers to both effects was studied by speckle pattern correlation in which the speckles are recorded at each disturbance and analyzed. By tracing the recorded speckles , x and y displacements could be measured and the strain could be determined in two dimensions. Power attenuation in each fiber was studied in each case as well. Both speckle correlation and power attenuation techniques used in the study showed similar indication on the sensitivity of the optical fibers to the external disturbers.

Abstract: Metrologists at the National Institute for Standards-NIS (Egypt) develop length measuring devices to provide reliable and less expensive metrological systems for accurate measurement. Length Laboratory Group investigates the sources of errors in the absolute measurement of length using the improved Abbe vertical metroscope. The investigation includes analyzing of errors induced by optical alignment, environment, and instrument. Errors due to environment and vibration are reduced by controlling the area in which the technique is placed. The instability in the readings caused by temperature fluctuations is handled by averaging 1000 points/sec. To ensure ideal contact between the probe of the comparator and the surface of the artifact, holographic technique is used in testing the uniformity of the probe at the area of contact. Other factors influencing the measurements such as material expansion of the artifact and optical source used in the measurement are considered in the uncertainty evaluation. The uncertainty in the absolute measurement of gauge block length of 80mm is found to be ±0.2µm. The results of measuring some pieces using the absolute method are in good agreement with the corresponding reference values given in their calibration certificate.

Abstract: In this paper, Monte Carlo method (MCM) is used to analyze the uncertainty of optical calibration of end standards using both contact and non-contact techniques to validate the uncertainty values obtained by the conventional method, Guide to the expression of Uncertainty in Measurement (GUM). Number of trials (M=10⁴) is simulated with the probability density function (pdf) for each quantity, and the comparison between the results of the MCM and the GUM shows good agreement which in turn validates the uncertainty values obtained by the conventional method. The statistical analysis, variables' distributions, and the output of each technique are discussed in detail.