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Early detection of potentially unreliable areas in optical fibers makes it possible to detect degradation of optical fibers of fiber-optic communication lines at an early stage. Early diagnostics of the physical state of optical fibers located in the laid optical cables of telecommunication systems is an important topical task. The paper presents adaptive algorithms that allow one to determine the maximum of the Mandelstam–Brillouin scattering spectrum (Brillouin frequency shift), and then the degree of tension of optical fibers. The process of determining the Brillouin frequency shift, whose values at wavelengths of laser radiation used in telecommunication systems belong to the microwave range, can be significantly accelerated if adaptive algorithms for obtaining and processing data are implemented due to a special choice of the step for the scanning frequency and the time of accumulation of measurement results. The adaptive algorithms considered in this paper make it possible to speed up the process of obtaining output results in Brillouin reflectometers by ignoring readings that do not significantly affect the final characteristics. The construction of approximate graphs of the distribution of the spectrum and tension along the length of the fiber allows the trained user of the Brillouin reflectometer to stop the analysis process in order to make corrections to the measuring process (selection of the scanning range in frequency, change in the scanning step in frequency, choice of the accuracy of the presentation of output results, change in spatial resolution, etc.), which also speeds up the testing of the selected fiber. The measurement process can also be accelerated by adaptively changing the number of averages. With a database of measured Mandelstam–Brillouin scattering characteristics of optical fibers of various types and manufacturers, the speed of obtaining tension plots can also be increased. Since the approximate value of the Brillouin frequency shift is calculated already at the initial steps of the measurement process, preliminary dependences of the tension distribution along the length of the fiber will be constructed rather quickly. [ABSTRACT FROM AUTHOR]

This paper reports the effect of core diameter of optical fiber cables on stimulated Brillouin scattering loss, which is one of the major loss characteristics of an optical fiber communication system. Analysis of this loss characteristic at three windows of the operating wavelength of a laser has been carried out through a numerical approach. Among different types of optical fiber cables, multi-mode step index silica fiber, multimode graded index silica fiber and plastic fibers have been considered for the numerical analysis. The numerical analysis has been performed using MATLAB in this research work. Through the comparative analysis, it has been ascertained that the Brillouin scattering loss is not only affected by the operating wavelength, but also by the core diameter of the different type of the cable. From the investigation of the comparative analysis, it is revealed that Brillouin scattering loss declines with the application of multimode graded index silica fiber. However, in the plastic fiber category, plastic step index fiber offers better performance. [ABSTRACT FROM AUTHOR]

Problems requiring high-precision comparisons and synchronization of time scales (TS) of remote time and frequency standards are analyzed. The prospects of using fiber-optic communication lines to solve these problems are considered. Data on maximum operating distances and accuracy characteristics of TS comparison systems using fiber-optic communication lines are given. It is shown that the range of existing systems is not sufficient for solving a number of relevant problems. A method for amplifying optical signals in an optical fiber using the stimulated Raman scattering (SRS) effect is proposed. The application of the Raman amplifier in telecommunication systems is considered. A method is suggested for using SRS to amplify the optical signals of TS comparison systems. A scheme is proposed for a system of one- and two-way TS comparisons of distant objects using signal amplification based on the SRS effect realized using two-way counter-pumping. The operational principle of the system is described along with the procedure for determining the divergence in the TS of remote objects. The results of estimating the error and range of systems of one- and two-way comparisons of time scales using the Raman amplifier are presented. It is shown that the implementation of Raman amplification in the equipment of such systems will allow their range to be increased by more than three times without reducing system accuracy. [ABSTRACT FROM AUTHOR]

• Distributed optical fiber Brillouin optical time-domain reflection sensing system is used as passive railway monitoring system, which has advantages of anti-electromagnetic interference, high sensitivity, strong stability and low maintenance cost. • Monitoring Brillouin scattering signal of whole optical cable can be completed by using a redundant cable of railway communication optical fiber, which greatly saves construction cost and capital cost. • The railway communication optical fiber Brillouin scattering signal is used to complete position determination of track area/slopes/tunnels, and complex manual calibration work is completed by technological ways, which reduces time cost and capital cost of calibration and fault resolution. • Accumulated Brillouin scattering signal data of railway communication optical fiber for a long time has potential to assist in the analysis and judgment of problems such as abnormal structural state of railway track area/slopes/tunnels. Wide coverage and complex environment along the railway make a huge demand for calibration in critical areas such as tunnels or slopes. In this paper, an on-line identification method of railway tunnels and slopes based on Brillouin scattering signal is proposed. By monitoring Brillouin scattering signal of a redundant communication optical fiber, tunnels and slopes can be recognized by feature analysis. Experimental results indicate that the on-line identification method of railway tunnels and slopes based on Brillouin scattering signal is effective, invulnerable and accurate. [ABSTRACT FROM AUTHOR]

We proposed and experimentally demonstrated a compact fiber-based fast light generator based on Brillouin lasing oscillation. A four-port optical circulator and a piece of polarization-maintained fiber (PMF) are properly connected to establish a fiber ring for Brillouin-based loss resonance generation with non-resonance pump scheme. Transmitting pump light signals can be temporally self-boosted as its input power surpasses the Brillouin threshold. A power-dependent tunable temporal advancement is implemented over a wide-band working wavelength ranging from 1535 nm to 1565 nm. The feasibility of the proposed scheme is beneficial to bring potential applications in sensing and temporal cloak. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin scattering (SBS) is one of the most important nonlinear phenomena because it limits the maximum transmission power in modern optical communication systems. Unfortunately, the simulation of SBS is time-consuming, since it requires estimating the solutions for a set of complex differential equations that describe this phenomenon. In this paper, a novel high-performance computing model intended to analyze the main dispersive effects present in modern fiber communication systems is proposed. A full optical characterization of the simulation results is included and compared with the efficiency and improved speed of our parallel implementation versus a previous sequential model for SBS. Also, an evaluation of the throughput of our parallel implementation using both central processing unit multi-core and graphics processing unit is presented. Results show that parallelism increases the performance of the simulation tenfold. [ABSTRACT FROM AUTHOR]

The modeling of the simultaneous propagation of high-power and bidirectional data along the same 10-km-long single-mode fiber is discussed. The intense signal carries the energy needed to supply an instrument in the context of cabled submarine observatories. The considered mathematical description takes into account the fiber’s nonlinear behavior in terms of Raman and Brillouin scattering to describe spectral propagation in the static regime. By testing our model against measurements, its validity is evaluated. Preliminary results are promising and reveal the path to follow for its improvement. [ABSTRACT FROM AUTHOR]

Multi-wavelength wavelength convertor (MWC) has many important applications in the fields of optical communications and optical fiber sensing. In this paper, a brand-new MWC driven by forward Brillouin scattering (FBS) in a large effective area fiber (LEAF) is proposed and demonstrated. In the MWC, the incident multi-wavelength light waves excite acoustic vibration in fiber by optomechanical interactions, and causes a change in the refractive index of the fiber through electrostriction effect. The changed refractive index causes phase modulation which applied on a single-wavelength light wave with target wavelength, and the single-wavelength light wave is modulated into multi-wavelength light waves while keeping the target wavelength as the central frequency. In a proof-of-concept experiment, a 2-km long LEAF is used as wavelength conversion medium, and the obtained MWC features very low deteriorations in side-mode suppression ratio (SMSR), multi-wavelength output power flatness and signal to noise ratio (SNR). The demonstrated MWC also has a wide tunable target wavelength ranges up to 23.6 nm, discretely tunable frequency interval up to over 1 GHz, low total output power fluctuation of 4.68%, and a conversion efficiency improvement of 2.55 dB. Its good performance may provide a promising way to design high-performance multi-wavelength convertor. • Novel multi-wavelength convertor based on forward Brillouin scattering. • Multi-wavelength convertor performs perfect in proof-of-concept experiment. • Wide tunable wavelength ranges up to 23.6 nm. • Conversion efficiency higher than that of convertors based on four-wave mixing. • Provide a new idea for designing wavelength convertor. [ABSTRACT FROM AUTHOR]