Papers by Keyword: Optical Communication

Abstract: This present work is about simulating and analysing a Vertical Cavity Surface Emitting Laser (VCSEL) structure used in optical fibre communication systems. In this paper a VCSEL structure made of seven Quantum Wells of Indium Gallium Arsenide Phosphide (InGaAsP) emitting at 1550 nm is simulated. The device is analysed looking at the following characteristics: Direct current current and voltage (IV) characteristics, light power against electrical bias, optical gain against electrical bias, light distribution over the structure, output power and threshold current. Specification of material characteristics, ordinary physical models settings, initial VCSEL biasing, mesh declarations, declaration of laser physical models, their optical and electrical parameters were defined using Atlas syntax. Mirror ratings and quantum wells are the two main parameters that were studied and analysed to come up with structure trends. By determining important device parameters such as proper selection of the emission wavelength and choice of material; a VCSEL with an output power of 9.5 mW was simulated and compared with other structures.

Abstract: With the sub-module number and scale growing on, the whole control system of MMC (Modular Multilevel Converter) tends to be much more complicated because of the cascade structure, which also intensifies the pressure of the converter main controller. To distribute the converter main controller’s task, the design of sub-module tenders itself extremely important. However, there is no explicit and comprehensive study on how to design the sub-module. This study, according to the characters of MMC, introduces a feasible architecture of hardware and software for the sub-module with optical communication. Each sub-module has its own independent controller and control system. That is to say, every sub-module is a complete system, which can do calculation and communication with outside. Sub-modules connect with the main controller of converter through communication using optical fibers. By adopting the optical communication, sub-modules not only can receive the control references data from the main controller, but also can send its own condition information back, which creates an interactive communication between the two sides. Additionally, through detailed experiments, the validity and feasibility of the design are demonstrated under two different control strategies.

Abstract: Visible light communication (VLC) is an optical wireless communication technology that uses visible light emitting diodes (LEDs) as a communication source. Since the LEDs are also used for illumination, the cross-section emission effects of the LEDs need to be analyzed as they apply to indoor VLC channels. In order to evaluate the illumination and communication performance according to the emission cross-section pattern, a simple LED model with a quasi-elliptic emission cross-section is proposed and compared to a circular LED model. The LEDs with a quasi-elliptic emission cross-section provide less fluctuation in the illumination and optical power distribution at the receiving plane. The four-transmitter VLC system is found to support at least at 30 and 33 Mb/s for circular and quasi-elliptic emission cross-section LEDs for the entire receiving plane, respectively.

Abstract: Propose the simulation of THz carrier frequencies using the small device and a Gaussian beam propagating within the device system. We found that the generated output power with the high frequency can be achieved. This consisted of a serial nonlinear micro ring resonator system for generating pulse and signal filter by Add/Drop filter, a technology optical communication by the micro ring resonator which generates the THz frequency multiple, whereas channel capacity in term of multi frequency bands can be provided by optical Add/Drop multiplexing. The increase in the number of channel capacity can be obtained by the increase in frequency density, while the security was introduced by the specific frequency filter, which was operated by the central operator. The optical micro ring resonators for THz frequency generation and enhancement are reviewed. The advantage of proposed system can be implemented by using the simultaneous optical communication system.

Abstract: The development of optical fiber transmission technology provides a broad application prospect for the communication of real-time battlefield information. The information could be communicated between the front and headquarters through the cable by using tactical optical fiber communication system, which ensures the missions of military intelligence communicated and tactical real-time arrangement are completed successfully. According to the requirements of multiplexer for military tactical optical fiber communication system, the filters with low-loss have been developed. Filters are prepared by the depositing method of dual ion beam sputtering, Nb2O5 and SiO2 have been chosen as deposition materials, and the filter film is designed and optimized with the help of TFCalc software. In order to broaden the shortwave cutoff region of the filter, the long-wave pass film have been added behind the initial film, and the thickness of the matching layers have been optimized, which based on the concept of equivalent refractive index, the insertion loss of the pass-band of the filter has been reduced. The optical extreme value method and average time method have been used to control layers thickness, and the problem of the layers thickness accuracy controlling have been solved by using the method of real-time calibration of the deposition rate and the repeatability of parameters accurately control. The transmission spectrum of the filter has been tested, which demonstration that the center wavelength of the filter is 1511.2nm, the width of the filters pass band is 17.1nm and 23.5nm in the region of-0.5dB and-35dB respectively, the worst insertion loss within pass band region is-0.1dB, the ripple of the pass band is 0.06dB. The results show that the preparation of the filter meets the using requirements of military tactical fiber optic communication system well.

Abstract: This paper gives a theoretical basis principle and structure of OFDM. The O-OFDM has three parts including transmitter, receiver and fiber. The main and key component is IFFT and FFT block. And then a basic direct detection optical-OFDM system (DO-OFDM) is designed and simulated by the software Optisystem. The performance of the system is viewed by the visualizer of the software compared to the RZ, OFDM and QAM modulation system. The result shows that the OFDM system is better than conventional serial modulation schemes like RZ, QAM.

Abstract: In this paper, a novel CO-OFDM system using phase diversity receiver and phase estimating is proposed, theoretically analyzed, and demonstrated by simulation results. 10Gb/s C0-OFDM signals can travel in this system for at least 320km.

Abstract: A novel self-mixing homodyne detection 60GHz radio over fiber (RoF) scheme with 5Gb/s 32QAM-OFDM downlink signals using discrete multitone (DMT) modulation is proposed and demonstrated by experiment. 5Gb/s 32QAM-OFDM downstream signals are transmitted over 42km SMF-28. The peak-to average power ratio (PAPR) characteristic, and the BER performance of 5Gb/s 32QAM-OFDM signals with different subcarriers generated DMT modulation and self-mixing homodyne detection are analyzed. The experimental results show the transmission performance of 5Gb/s 32QAM-OFDM signals with different subcarriers, and this RoF scheme is a suitable method for future 60GHz access system applications.

Abstract: In this paper, a long-distance optical communication system based on Embedded ARM platform is presented and demonstrated. The system is composed of two parts: LED/PD application terminal and its drive circuit. Terminal has a 4-inch touch screen with interactive interface based on Android system. The performance of data transfer in our prototype shows up to 50 m range at the transmission rate of 50kbps. This system is supposed to reach the distance of 2km or higher in the coming months.

Abstract: A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a laptop running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization.