Vibrations and their parameters can be measured through monitoring the speckle pattern of multimode optical fiber. In this paper a modified approach to realization of a specklegram based vibration sensor system is discussed. Replacing the (standard) camera detector with an array of several detector diodes improves the size and frequency range of the system. Different statistical methods for processing the signals from the diode array are presented, compared experimentally and discussed. The principal advantages of the specklegram vibration detection approach, low cost and distributed detection possibility, have been retained.

Professional undergraduate study of Communication and computer technology at Zagreb University of Applied Sciences is performed by using blended learning, combining the advantages of both face-to-face teaching and computer-assisted learning. For fundamental telecommunication courses such as “Digital circuits”, “Signals theory and processing” and “Information theory and coding”, teaching includes lectures, exercises and laboratory exercises. Lectures and exercises are held by face-to-face teaching, while laboratory exercises are hardware or software oriented and are performed in a standard laboratory environment. All teaching types are supported by a Learning management system for group as well as individual student preparation and learning. In this paper, the results of research about the correlation of students' success on the exam and their attendance of lectures and exercises, are presented. Modeling of data was performed by linear and piecewise linear regression (“hockey stick” shaped). The analysis of the results showed a strong positive correlation between the student success at exam and their attendance of lectures and exercises. Abovementioned confirms the importance of face-to-face teaching alongside of all technology mediated ways of learning in case of fundamental telecommunication courses.

This paper gives a closer insight to novel optical fibers by applying specialized numerical analysis approaches. First we have described a newly developed algorithm based on the spectral domain approach, which is employed in the analysis of multilayer optical fibers with circular symmetry. It computes the Green's functions of the considered fiber and locates the appropriate poles, which correspond to the actual propagating modes of the fiber. Through further analysis of the poles it is possible to obtain information about modal fields, attenuation, bending losses and dispersion properties for all modes present in fibers with very complicated refractive index profile. Furthermore, an approach for the analysis of novel types of fibers belonging to the so-called Photonic Crystal Fibers family is presented. Since the considered fibers can contain various inclusions in the core or the cladding structure, the analysis is in this case based on the modal decomposition of the electric field in spatial domain. In both analysis cases the obtained results were compared to the previously published or where possible measured results, showing very good agreement.

Telemetry system based on embedded Linux single board computer (SBC) is presented. The basis of the system is an optical sensor for measuring amplitude and frequency of structural vibrations. Detection of vibrations and their parameters is possible through observation of the output speckle pattern from the multimode optical fiber. Optical sensor is connected to the embedded SBC, which analyzes the data from the sensor and allows reasonably accurate monitoring of the vibration frequencies and amplitudes on a certain location. As a solution for acquiring the data remotely, it is possible to connect the SBC to a remote location using telecommunication networks (cellular networks, Wlan, etc...) or dedicated networks (ZigBee, radio links, etc...). Components used in this system are cheap and available: CCD array, laser light source, multimode optical fiber and a SBC with Linux operating system. Measurements have been made which show good agreement with actual vibration frequencies, and also good results have been obtained in measuring relative amplitude.

The purpose of this paper is to present a fiberoptic vibration sensor based on the monitoring of the mode distribution in a multimode optical fiber. Detection of vibrations and their parameters is possible through observation of the output speckle pattern from the multimode optical fiber. A working experimental model has been built in which all used components are widely available and cheap: a CCD camera (a simple web-cam), a multimode laser in visible range as a light source, a length of multimode optical fiber, and a computer for signal processing. Measurements have shown good agreement with the actual frequency of vibrations, and promising results were achieved with the amplitude measurements although they require some adaptation of the experimental model. Proposed sensor is cheap and lightweight and therefore presents an interesting alternative for monitoring large smart structures.

The possibility of measuring amplitude and frequency of structural vibrations using a multimode optical fiber is demonstrated. By detecting and analyzing the variations in the output signal speckle pattern it is possible to detect vibrations and their parameters. A working experimental model has been built and tested. Components used for this system are cheap and widely available: a CCD array (a simple web-cam), a common laser as a light source, a length of multimode optical fiber, and a computer where the data analysis is performed. Measurements have been made which show good agreement with actual values for the frequency parameter, and promising results were achieved with the amplitude measurements although they require some adaptation of the experimental model. This type of sensor system could find use in all areas of vibration sensing. It is a low cost and lightweight system and therefore extremely interesting for integration in smart structures.