International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The paper focuses on the security of fiber optic infrastructures. The main purpose of the paper is present the vibration detection system for unauthorized access to the fiber optic infrastructure detection. For this purpose, measurement of vibrations using the interferometric method and the measurement based on state of polarization changes evaluation is presented. For the measurement own designed systems were used. Both systems are theoretically described and the principles of use are explained. The measurement was performed at an experimental workplace in a laboratory at the university Based on evaluation measurement both systems are compared in term of sensitivity.

Distributed fibre optic sensing is well known in defence or oil industry in use as acoustic sensing. Telecommunication networks are threatened by fibre cuts mainly caused by digging activity or theft. Many network operators seeking appropriate solution for selfprotecting infrastructure system. Most commercially available solutions of distributed sensing systems allow sensing only on dedicated fibres. Sharing the same infrastructure for data transmission and sensing is, however, more advantageous. On the other hand, it is necessary to solve the possible interaction of both services and thus the interference. We have developed our own sensing systems and we have made several measurements to evaluate the suitability of the most widely used distributed sensing techniques – interferometric, reflectometry and polarization for using in existing data infrastructures on optical fibres with active data traffic.

The paper provides a comprehensive description of theoretical and practical aspects of electronic speckle pattern interferometry for technological residual stress measurement in various machine elements. Any results obtained by investigation of residual stress in a welded joint are presented.