A sensing system utilizing a standard optical fiber as a distributed sensor for the detection and localization of mechanical vibrations is presented. Vibrations can be caused by various external factors, like moving people, cars, trains, and other objects producing mechanical vibrations that are sensed by a fiber. In our laboratory we have designed a sensing system based on the Φ-OTDR (phase sensitive Optical Time Domain Reflectometry) using an extremely narrow laser and EDFAs.Keywords: optical fiber sensor, acoustic vibrations, detection, localization, Φ-OTDR.© 2015 Polish Academy of Sciences. All rights reserved IntroductionOptical fibers have been used in a wide range of applications during several last decades. The most visible and known utilization is in the area of telecommunications as the optical fiber technologies can offer bit rates in the range of terabits per second [1]. Fibers have been deployed not only in the area of optical networks but they are also more and more common in the fiber sensor technologies.Sensor applications are an attractive area of the optical fiber usage. The fiber construction, the principle of operation (the total reflection) and the signal form (radiation) make the transmission of data very safe and resistant to many sources of disturbances. At the same time transmitted signals are sensitive to ambient conditions, like the temperature, strain, vibrations or strong ambient electromagnetic field, which make them suitable for sensing purposes. Fiber sensors can be divided into two groups -extrinsic (hybrid) fiber optic sensors and intrinsic fiber optic sensors [2].

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Abstract-Passive optical networks are currently the most promising solution for access networks. Increasing bandwidth requirements and big data applications need a huge bandwidth. Nowadays, gigabit passive optical networks do not seem to be suitable for these purposes. This paper is focused on describing the development, parameters and needs for High Speed Access Networks (such as 100G EPON). The simulations with current wavelengths plans are presented. For simulations we used VPITransmissionMaker TM 9.7. Our goal was to create a rudimentary bidirectional PON system with one ONU and do several simulation scenarios by artificially increasing loss in a splitter for simulating more ONUs. Our following results consist of BER values and eye diagrams for each simulation scenario and proof that 100G EPON networks are most promising networks for the future. We proved that the 100G-EPON networks fully support the basic and currently used split ratios. We also created a two-way communication model and evaluated the obtained data from the bit error-rate and system reach point of view. The entire model was compared with the final version of NG-PON2.

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