Hollow-core fibers (HCF) are increasingly being studied and evaluated for telecommunication, as well as sensing application. They seem to have many advantages compare to standard single-mode fibers (SMF), especially in the area of the cyber-security of optical fiber infrastructures and also information they carrying. In our research we mainly focus on cyber-security issues, especially acoustic sensing. In the paper we evaluate sensitivity of negative curve HCF using a Mach–Zehnder interferometry (MZI). Results are compared with SMF (G.657 in this case). Both fibers were in primary coating with similar length. Sensitivity measurements were conducted within the controlled environment of an anechoic chamber. Results show that both fibers are sensitive to acoustic vibration and with post-processing method based on de-noising of the measured signal, the sensitivity can be improved. The clarity of the captured speech signal was assessed using the Speech Transmission Index for Public Address (STIPA).
Passive optical networks play an important role in access networks and in current 5G networks. Passive optical network (PON) recommendations are published for two sectors by the Institute of Electrical and Electronics Engineers (IEEE) and the International Telecommunication Union (ITU), covering transmission speeds from 1 to 100 Gbit with wavelength division multiplex (WDM). The recommendations of the ITU define different encapsulation methods for the Ethernet frame, and meeting these recommendations necessitates new tools for control and data transmission. We present a downstream frame bandwidth field analysis for the simple topology of an XG-PON with 2 ONUs. The main purpose is to prove that the current access networks do not rely only on Ethernet frame transmission.
The main topic of this paper is the detection state of polarization changes to enhance data security in fiber cable paths. The changes are generated by fiber manipulation or movements, which suggest potential security threats. Our designed system detects these changes using a polarization beam splitter and a pair of photodetectors. The values are subtracted from each other, sampled, and sent for analysis. The software detector applies FFT onto the signal and normalizes the output. The last step compares the sum of the bottom eighth of the spectrum against the threshold.
KEYWORDS: Sensors, Polarization, Data acquisition, Fiber optics sensors, Optical fibers, Time division multiplexing, Telecommunications, Photodetectors, Single mode fibers, Signal attenuation
The paper describes the possibilities of using the detection of fast and slow changes in the state of polarization for the detection of vibrations by an optical single-mode (SM) fiber. The system consists of a polarization beam splitter and a balanced photodetector. This sensing system is cost-effective, which contributes to its use in real operation. On the basis of an experiment with buried fiber near the railroad, the possibility of detecting vibrations with this system was proved. It is possible with simple analyzes to recognize the types of trains and their speed.
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