Comparison of reservation protocols for SOA and MEMS technology

The data transmission by high-speed optical networks has an upward trend. The most effective data transmission can be achieved by powerful reservation protocols, which are together with optical switches very important parts of high-speed optical networks. This paper deals with new reservation protocol called Search & Compare, which is designed according to the well-known Segment-based Robust Fast Optical Reservation Protocol. In this paper, we present time analyses of both reservation protocols. We focused mainly on intra-segment time analyses. During the reservation of network resources, we used the optical cross-connect as the core node, which is based on microelectromechanical system and semiconductor optical amplifier. These two technologies are becoming the dominant technologies in optical switching

Comparison of numerical modelling of degradation sechanisms in single mode optical fibre using MATLAB and VPIphotonics

Mathematical models for description of physical phenomena often use the statistical description of the individual phenomena and solve those using suitable methods. If we want to develop numerical model of optical communication system based on transmission through single mode optical fibres, we need to consider whole series of phenomena that affect various parts of the system. In the single-mode optical fibre we often encounter influence of chromatic dispersion and nonlinear Kerr effects. By observing various different degradation mechanisms, every numerical model should have its own limits, which fulfil more detailed specification. It is inevitable to consider them in evaluation. In this paper, we focus on numerical modelling of degradation mechanisms in single-mode optical fibre. Numerical solution of non-linear Schroedinger equation is performed by finite difference method applied in MATLAB environment and split-step Fourier method, which is implemented by VPIphotonics software

Investigation of 2D-WH/TS OCDMA system performance under the influence of PMD

The impact of a differential group delay (DGD) and polarization mode dispersion (PMD) on multi-wavelength picosecond code carriers used by two-dimensional wavelength-hopping time-spreading coding schemes in optical code division multiple access (2D-WH/TS OCDMA systems is investigated. Based on experimental data collected over ten days on a 111 km long commercially used fiber link PMD and DGD parameters are determined and used to find the code carriers temporal broadening. This information is then used to calculate the 2D-WH/TS OCDMA system performance degradation as a function of varying number of simultaneous users for different DGD

Design, optimization and experimental evaluation of slow light generating π-Phase Shifted Fiber Bragg Grating for use in sensing applications

This paper describes design, theoretical analysis, and experimental evaluation of a π-Phase-Shifted Fiber Bragg Grating (π-PSFBG) inscribed in the standard telecom fiber for slow light generation. At first, the grating was designed for its use in the reflection mode with a central wavelength of 1552 nm and a pass band width of less than 100 pm. The impact of fabrication imperfections was experimentally investigated and compared to model predictions. The optical spectra obtained experimentally show that the spectral region used for slow light generation is narrower (less than 10 pm), thus allowing for too-low levels of slow light optical-output power. In the next step, the optimization of the grating design was conducted to account for fabrication errors, to improve the grating’s spectral behavior and its temporal performance, and to widen the spectral interval for slow light generation in the grating’s transmission mode. The targeted central wavelength was 1553 nm. The π-PSFBG was then commercially fabricated, and the achieved parameters were experimentally investigated. For the region of (1551–1554) nm, a 15-fold increase in the grating’s pass band width was achieved. We have shown that a pair of retarded optical pulses were generated. The measured group delay was found to be ~10.5 ps (compared to 19 ps predicted by the model). The π-PSFBG operating in its transmission mode has the potential to operate as tunable delay line for applications in RF photonics, ultra-fast signal processing, and optical communications, where tunable high precision delay lines are highly desirable. The π-PSFBG can be designed and used for the generation of variable group delays from tens to hundreds of ps, depending on application needs

Numerical Estimation of Spectral Properties of Laser Based on Rate Equations

Laser spectral properties are essential to evaluate the performance of optical communication systems. In general, the power spectral density of the phase noise has a crucial impact on spectral properties of the unmodulated laser signal. Here the white Gaussian noise and 1/f-noise are taken into the consideration. By utilizing the time-dependent realizations of the instantaneous optical power and the phase simultaneously, it is possible to estimate the power spectral density or alternatively the power spectrum of an unmodulated laser signal shifted to the baseband and thus estimate the laser linewidth. In this work, we report on the theoretical approach to analyse unmodulated real-valued high-frequency stationary random passband signal of laser, followed by presenting the numerical model of the distributed feedback laser to emulate the time-dependent optical power and the instantaneous phase, as two important time domain laser attributes. The laser model is based on numerical solving the rate equations using fourth-order Runge-Kutta method. This way, we show the direct estimation of the power spectral density and the laser linewidth, when time-dependent laser characteristics are known

Monitoring of polarization-based effects in fiber-optic transmission link caused by environmental variations

The fast transmission of signals around the globe is fundamental to the flow of information for our society. A long-haul transmission certainly represents one of the key advancements that shaped modern ways of communicating and offers a nearly instant access to any available data or a latest information. However, fiber-optic transmission typically suffers from a variety of physical impairments that degrade the signal quality, thus imposing limits on both, the achievable transmission capacity and data reach. Of particular concerns are stochastic fiber impairments, primarily represented by polarization mode dispersion (PMD). The PMD originates from a random birefringence caused by imperfect fiber circularity and other, both internal and external, effects, basically completely re-defining the light polarization state of output signal compared to its initial counterpart. The PMD is particularly critical as it restricts operation of fiber-optic links running at speeds higher than 10 Gbps. This, in turn, hinders fiber link re-adaption towards higher transmission bit rates in future, however. In this context, both in-line link monitoring and testing of PMD-based effects is of great importance within the recently used optical fiber links. However, polarization-based effects are also very sensitive to the environmental changes, substantially degrading transmitted optical signals and reducing link quality. In this work, we provide experimental characterization for PMD-based propagation effects in optical fibers influenced by wind gusts. The investigation was performed on commercially used fiber-optic link that runs through optical power ground wire cables. The 111-km-long optical link under study comprised installed optical fibers with available 88 channels. Here, we monitored environmental changes caused by wind conditions over several consecutive days with a 60 second time frame and sensed PMD impact on the link performance. Here, differential group delay (DGD) was chosen to be a key parameter, enabling for sensitive characterization of wind related link changes. Measured maximum DGD’s were 4 and 10 ps for wind speeds up to 5 and 20 m/s, respectively. In addition, experimentally measured data were used in numerical model to assess the optical link quality. For a low wind condition, we observed negligible quality degradation in the optical link, considering transmission bit rates of 10, 40, and 100 Gbps. Conversely, in case of strong wind condition, the optical link maintained a reliable operation only for established 10 Gbps, while significant link degradation was observed for bit rates of 40 and 100 Gbps. Our work shows promising way to effectively sense and monitor undesired environmental variations and their impact on polarization-based fiber link propagation effects, which in turn, can allow an instant link quality evaluation

High-speed operation of fiber-optic link impaired by wind gusts

The fast signal transmission is critical long-haul communication systems. They represent the key advancements, shaping information-communication technologies. Fiber-optic transmission suffers from many degradation effects, and of particular concern are stochastic fiber impairments represented by polarization mode dispersion (PMD). The PMD is critical as it limits link operation at data rates higher than 10 Gbps. In this work, we report on experimental measurements and theoretical analysis characterization for PMD-based propagation effects in optical fibers influenced by wind gusts. The study was performed on fiber-optic link that runs through 111-km-long optical power ground wire cables. Measured maximum of DGD was up to 10 ps for a wind speed of 20 m/s. This wind condition, the optical link maintained a reliable operation only for established 10 Gbps, while considerable link degradation was seen for data rates of between 40 and 100 Gbps

Location based services in GSM networks and new possibilities for their application in transport

An enormous growth of mobile communication gives new challenges for new services creation. One of the possibilities is to focus attention on the localisation and localisation based services. It gives for mobile networks customers new information about position of another customers or subjects. This paper deals with utilisation possibilities of the localisation technology “Cell ID” and improvement of its accuracy