Pulse width shortening combinations (PWSC) for ultra-dense WDM systems and calculation of PWSE

Optical communication systems introduced paradigm shift in the forte of data transmission at higher speeds and over longer distances where, on contrary electrical transmission systems failed due to higher amplitude degradation, interferences and lower bandwidths. However, pulse width increase (PWI) in the optical fiber limits the overall distance reach and also introduces more bit errors which needs to addressed. So far, pulse width shortening fibers (PFs) and fiber Bragg grating (FG) used individually in most of the reported studies, however pulse width shortening (PWS) took either high cost (in PFs) or lower PWS efficiency (PWSE) (in FG). Therefore, in this research manuscript, we made emphasis on the combined PWS effects of diverse techniques such as optical phase conjugation (OC), FG and PFs in ultra-dense wavelength division multiplexing (WDM) system. Total link length of 400 km has been covered in 128 channels ultra dense wavelength division multiplexing (UDWDM) system at 10 Gbps by incorporating diverse combined organized placements of FG, OC and PFs such as FG-PF, OC-PF and FG-PF-OC. Results revealed that economical and maximum PWSE arrangement for proposed system is FG-PF-OC.

State of research and development of small spacecraft with optical communication

The current state of scientific and technical research and development of small space vehicles using optical communication systems is considered. The problems standing in the way of creating intersatellite optical communication are discussed as well as the mutual position of satellites determination and it tracking. Scientific tasks for the implementation of the development of an optimal reliable control system for satellite communication are defined.

Simulation Study of In-Phase and Out-Phase Enhanced Absorption of Graphene Based on Parity–Time Symmetry One-Dimensional Photonic Crystal Structure

In the field of modern optical communication systems and photoelectric detection, new components with complex functions and excellent performance are urgently needed. In this paper, a graphene-based parity–time (PT) symmetry structure is proposed, which is achieved by preparing the graphene layer on the top of a PT-symmetry photonic crystal. The transfer matrix method was used to calculate the absorptance of graphene, and a unique amplified absorption effect was found. Meanwhile, the peak value and wavelength position of the absorption can be modulated via the applied electric field. The results show that by adjusting the negative square-wave electric field from −3.5 × 10−5 to −13.5 × 10−5 V/nm (or the positive square-wave electric field from 2 × 10−5 to 11 × 10−5 V/nm), the proposed structure can achieve in-phase (or out-phase) enhanced absorption for the communication wavelength 1550 nm, with the absorption of graphene from 17 to 28 dB (or 30 to 15 dB) corresponding to the square-wave modulation electric field change. The modulable absorption properties of graphene in the structure have potential in optoelectronic devices and optical communication systems.

Traffic interception in fiber optical video-systems

In fiber-optic video systems, as well as in optical communication systems, standard single mode optical fibers (SSMF, standard G.652) are usually used. One of the advantages of these fibers is the ability to use CWDM in a wide spectrum. At the same time, more optimal near the wave-length of 1550 nm are provided by non-zero dispersion fiber (NZDSF, standard G.655) fibers. However, as studies have shown, these optical fibers have an increased sensitivity to bending. This fact can be used to traffic interception. It is shown that fiber-optics systems with SSMF have more protection from traffic interception than systems with NZDSF. To transmit a high-confidentiality video signal, special techniques, such as frequency modulation, can be used, or additional noise signals can be added.

Simulation of optical triode based on PT symmetric structure under electro-optic modulation

In modern microwave and optical communication systems, it is urgent to develop optical components with the same performance as electronic components. In this paper, a PT-symmetric structure including electro-optical medium is designed to construct optical triode. It is found that the structure has a pole effect of amplification under certain parameters. The frequency of the incident wave at the pole is taken as the carrier frequency, and the electrical signal is modulated into an optical signal. By setting the bias electric field, the modulated optical signal can be amplified in phase and out phase, and even by doubling frequency, and a new optical triode model is obtained. The designed model will play an important role in the design of optical integrated devices.

A tutorial on fiber Kerr nonlinearity effect and its compensation in optical communication systems

The advent of silica-based low-cost standard single-mode fibers revolutionized the whole communication industry. The deployment of optical fibers in the networks induces a paradigm shift in the communication technologies used for long-haul information transfer. However, the communication using the optical fibers is affected by several linear and nonlinear effects. The most common linear effects are attenuation and chromatic dispersion, whereas the dominant nonlinear effect is the Kerr effect. The Kerr effect induces a power-dependent nonlinear distortion for the signal propagating in the optical fiber. The detrimental effects of the Kerr nonlinearity limit the capacity of long-haul optical communication systems. Fiber Kerr nonlinearity compensation using digital signal processing (DSP) techniques has been well investigated over several years. In this paper, we provide a comprehensive tutorial, including the fundamental mathematical analysis, on the characteristics of the optical fiber channel, the origin of the Kerr nonlinearity effect, the theory of the pulse propagation in the optical fiber, and the numerical and analytical tools for solving the pulse propagation equation. In addition, we provide a concise review of various DSP techniques for fiber nonlinearity compensation, such as digital back-propagation, Volterra series-based nonlinearity equalization, perturbation theory-based nonlinearity compensation, and phase conjugation. We also carry out numerical simulation and the complexity evaluation of the selected nonlinearity compensation techniques.