Performance Analysis of Optical Communication Systems using OFDM by Employing QPSK Modulation

The high data rate along with good Quality of Service (QoS) requirements of Next Generation Network (NGN) can be fulfilled by using the optical fiber communication networks. At high data rate, dispersion will be the limiting factor which needs to be suitably compensated. Many efforts have been drawn to the development of dispersion compensating devices / techniques to recover or prevent the broadening signal pulse. The Orthogonal Frequency Division Multiplexing (OFDM) is very attractive because of its capacity to handle the dispersion causing pulse broadening at the receiver without changing the internal architecture of the system. Thus Integration of Optical Communication Systems with OFDM system appears to be the most suitable technology for the NGN. The work presented here consist of the design, simulation and performance evaluation for the dispersion compensation in optical fiber communication systems using OFDM for high data rate transmission by utilizing the capacity of the optical fiber channel efficiently. The system performance has been analyzed and compared it with the single carrier optical communication systems. Various simulation results show that systems using OFDM can give dynamically tunable compensation of the dispersion by changing the various parameters of the OFDM systems. The work presented here reveals that the use of OFDM can be used to construct cost effective, high data capacity optical communication systems with extended transmission distance by employing dispersion compensation. These systems have the ability of supporting data rate up to 40 Gbps per optical channel and are appropriate for implementation as upgraded long haul high data rate optical Communication systems. DOI: 10.17762/ijritcc2321-8169.15014

Advanced optical modulation and fast reconfigurable en/decoding techniques for OCDMA application

With the explosive growth of bandwidth requirement in optical fiber communication networks, optical code division multiple access (OCDMA) has witnessed tremendous achievements as one of the promising technologies for optical access networks over the past decades. In an OCDMA system, optical code processing is one of the key techniques. Rapid optical code reconfiguration can improve flexibility and security of the OCDMA system. This thesis focuses on advanced optical modulations and en/decoding techniques for applications in fast reconfigurable OCDMA systems and secure optical communications. A novel time domain spectral phase encoding (SPE) scheme which can rapidly reconfigure the optical code and is compatible with conventional spectral domain phase en/decoding by using a pair of dispersive devices and a high speed phase modulator is proposed. Based on this scheme, a novel advanced modulation technique that can simultaneously generate both the optical code and the differential-phase-shift-keying (DPSK) data using a single phase modulator is experimentally demonstrated. A symmetric time domain spectral phase encoding and decoding (SPE/SPD) scheme using a similar setup for both the transmitter and receiver is further proposed, based on which a bit-by-bit optical code scrambling and DPSK data modulation technique for secure optical communications has been successfully demonstrated. By combining optical encoding and optical steganography, a novel approach for secure transmission of time domain spectral phase encoded on-off-keying (OOK)/DPSK-OCDMA signal over public wavelength-division multiplexing (WDM) network has also been proposed and demonstrated. To enable high speed operation of the time domain SPE/SPD scheme and enhance the system security, a rapid programmable, code-length variable bit-by-bit optical code shifting technique is proposed. Based on this technique, security improvements for OOK/DPSK OCDMA systems at data rates of 10Gb/s and 40Gb/s using reconfigurable optical codes of up to 1024-chip have been achieved. Finally, a novel tunable two-dimensional coherent optical en/decoder which can simultaneously perform wavelength hopping and spectral phase encoding based on coupled micro-ring resonator is proposed and theoretically investigated. The techniques included in this thesis could be potentially used for future fast reconfigurable and secure optical code based communication systems

Air Traffic Management Abbreviation Compendium

As in all fields of work, an unmanageable number of abbreviations are used today in aviation for terms, definitions, commands, standards and technical descriptions. This applies in general to the areas of aeronautical communication, navigation and surveillance, cockpit and air traffic control working positions, passenger and cargo transport, and all other areas of flight planning, organization and guidance. In addition, many abbreviations are used more than once or have different meanings in different languages. In order to obtain an overview of the most common abbreviations used in air traffic management, organizations like EUROCONTROL, FAA, DWD and DLR have published lists of abbreviations in the past, which have also been enclosed in this document. In addition, abbreviations from some larger international projects related to aviation have been included to provide users with a directory as complete as possible. This means that the second edition of the Air Traffic Management Abbreviation Compendium includes now around 16,500 abbreviations and acronyms from the field of aviation