Enhanced Spectrum Slicing--Wavelength Division Multiplexing Approach for Mitigating Atmospheric Attenuation in Optical Communication

Over the last decades, free-space optics (FSO) emerged as a prominent way of communication over radio frequency communication and microwave communication. Working of FSO in comparison with optical fiber cable (OFC) network is the same. The only difference between FSO & OFC is the transmission of an optical beam. The optical beam is transmitted through the free space in the case of FSO. Whereas the transmission of optical beam takes place using OFC core, i.e. glass fiber in the case of OFC. Fog, haze, rain, and clouds in the atmosphere directly affect FSO performance and the power of signal propagation. Further added, the wavelength of propagating beam is based on the size of fog particles which leads to atmospheric attenuation. To mitigate the impact of atmospheric attenuation on signals, the proposed study is based on a spectrum slicing (SS) - wavelength division multiplexing (WDM) system with Pre and Post Amplification. The analysis of SS-WDM-Pre and SS-WDM-Post has been done over various values of attenuation. The comparison analysis proves that the SS-WDM-Post is more efficient than both SS-WDM-Pre and traditional SS-WDM in terms of Q-factor.

Entanglement of a System of an Indirectly Linked Two-Coupled-Cavity through an Optical Fiber Cable for Single Excitation Atomic States in the Presence of an External Field

The dynamics of the quantum entropies of a system of two cavities coupled by an optical fiber cable, each cavity contains a two-level atom interacting with a single electromagnetic field in addition to an external classical field, is investigated. Under canonical transformations, the considered Hamiltonian is diagonalized. Effective Hamiltonians in three different limiting regimes: namely large optical fiber cable coupling bstrength, large detunig, and comparable detuning and optical fiber cable coupling strength, are derived. The ith ¯ -tom are respectively prepared in the superposition coherent and the ground states while the fields are prepared in the vacuum states. An analytical expression for the solution of the Schr¨odinger equation for each dispersive is derived. The degree of entanglement (DEM) is studied by using von Neumann atomic entropies. The influences of both the optical fiber cable coupling strength and the detuning on the evolution of the DEM ”their values are closely chosen to be compatible with the imposed restrictions for the applications of the different regimes” are analyzed. General conclusions reached are illustrated by numerical results.

Vulnerability of Submarine Cable Network of Mainland China: Comparison of Vulnerability between before and after Construction of Trans-Arctic Cable System

The submarine optical-fiber cable (submarine cable) is a large connectivity infrastructure, which plays an important role in international communication, cyber-physical systems, and even national security. Although submarine cable network interruption may cause serious consequences, researching its vulnerability has not attracted much attention. This paper proposes a quantitative method to measure the vulnerability of the submarine cable network and evaluates the influence of the upcoming trans-Arctic cable (TAC) system on the submarine cable network of mainland China. To address this issue, first, the submarine cable network of mainland China is constructed. Further, methodology based on complex network and geospatial perspective is proposed to simulate the changes of network eigenvalues under different attacks and to quantitatively analyze the variation degree of network vulnerability. With the proposed method, the vulnerability of the submarine cable network of mainland China before and after construction of the trans-Arctic cable system is compared. The results reveal the key node countries and sea channels of the submarine cable network of mainland China and show the significance of the TAC system.

SPECIFIC FEATURES OF OPTICAL FIBER CABLE OPERATION DURING TENSION AND CHANGE OF AMBIENT TEMPERATURE

This article examines the effect of longitudinal and thermoelastic deformation of an optical module on the technological reserve of an optical fiber. Analytical expressions are given for determining the lower limit of the technological margin of an optical fiber for various types of fiber-optic cable section along the axis.

Seven-Point Solar Tracking Control for a Fiber-Optic Daylighting System

A strategy for precise solar tracking has been developed using feedback signals from seven photosensors in conjunction with the operation of an active daylighting system. The tracking system was composed of a microcontroller, two stepper motors, photosensors, a grooves-in Fresnel lens concentrator, and a glass optical fiber cable. A robust control was implemented using cadmium sulfide (CdS) sensors to track the sun’s path precisely from sunrise to sunset. To avoid the cloud effect, two separate sensors were installed apart from the main tracking sensors. The control system was allowed to track the sun’s position if clouds covered the sky continuously for less than approximately 70 min. To analyze the performance of the solar tracker for daylighting applications, a series of experiments were performed in different weather conditions where the accuracy and effectiveness of the present solar tracking control were confirmed.

Precise Distributed Acoustic Sensing measurements by using seafloor optical fiber cable system for seismic monitoring

<p>Distributed Acoustic Sensing (DAS) measurements which utilize an optical fiber itself as a sensor can be applied for various purposes. An observation of earthquakes using an optical fiber deployed on the seafloor with DAS technology is attractive because DAS measurements enable a dense seismic observation as a long linear array. Spatial resolution of the observation reaches a few meters. The length of the array is determined by the measurement range of the DAS interrogator deployed on the optical fiber, and a fine spatial sensor interval can be configured. DAS measurements have become increasingly accurate and the current state of technology exhibit high signal quality. Because DAS measurement is useful for earthquake observation, there were some trials for an observation of earthquakes using an optical fiber deployed on the land or the seafloor. However, There are few observations using DAS technology on seafloor until the present.</p><p>In 1996, a seafloor seismic tsunami observation system using an optical fiber cable was deployed off the coast of Sanriku by Earthquake Research Institute, the University of Tokyo. The system has three seismic stations and two tsunami-meters, and a length of the cable is approximately 115 km. The system has six spare (dark) optical fibers which are dispersion shifted single mode type, and have been incorporated for future extension of the observation system. We have started development of a seafloor seismic observation system utilizing DAS technology on the Sanriku cable observation system as a next generation of marine seismic observation system. In 2019, we performed DAS measurements using a dark fiber from Sanriku seafloor observation system three times. An interrogator was installed in the cable landing station temporarily. Data were recorded with various values of parameters, such as length of data collection (array aperture), gauge length, ping rate, acquisition offset, for evaluation of data quality and signal to noise ratios. The total recording period for three measurements was approximately three weeks. As a result, many earthquakes including micro-earthquakes were recorded. The obtained data will be used to develop data processing techniques for seismic observations utilizing DAS measurements.</p><p> </p>