Comparative Analysis of Dispersion Compensating Fiber (DCF) and Multiple Optical Phase Conjugation (OPC) modules used for Dispersion Compensation and Nonlinearity Mitigation

Optical communication when used for long haul communication is characterized by dispersion and nonlinearities. Different techniques are used for the dispersion compensation and nonlinearity mitigation. Two of these techniques are Dispersion Compensating Fiber (DCF) and Optical Phase Conjugation (OPC). In this paper the performance of the system is analyzed by comparing various results at the receiver. A 10Gb/s NRZ signal is launched into a long Single Mode Fiber (SMF). Results in the terms of Q-factor (linear) and BER are observed by varying fiber length. Optical system consisting of one OPC and two OPC is also analyzed for different transmission distance. Simulation results show that, when compared with optical system consisting of one OPC, Q-factor improvement of 3.51 is achieved for the optical system consisting of two OPC. Nonlinearities are mitigated using DCF and OPC and on comparing with DCF, Q-factor improvement of 11.3 is achieved for OPC

Comparative performance study in multiplexed RZDPSK for SMF's with FBG

The Fiber Bragg gratings have emerged as important components in several of light wave applications in the FBG becoming a ubiquitous and necessary element in equipment located throughout the network from the central office to the home. This paper explores comparative performance study with and without using FBG as an external dispersion compensator for sixteen channel return to zero differential phase shift keying modulation operating at 45Gbps per channel with channel spacing of 0.15nm. Simulations are done with various single mode fibers with and without external FBG.Better performance (Q, BER) for dispersion values used in simulation are -58ps/nm, 23ps/nm, and 100ps/nm for FBG's used at receiver channels. It is observed that FBG used with receiver channels support larger communication fiber length, also G655 (NZDSF) fiber shows much better performance as compared with other SMF's tested. Key Words: FBG, WDM, DCG, DCF, FOM, RZ

Coexistence of optical systems on a physical layer

Tato diplomová práce se zabývá koexistencí optických systémů na společné fyzické vrstvě. Cílem této práce je analýza interakcí mezi různými optickými systémy na fyzické vrstvě, přičemž dílčím cílem je porovnání integrace těchto systémů za různých provozních podmínek. Data pro tuto práci byla získána pomocí simulačního prostředí Optsim. Na základě výsledků koexistence různých systémů za různých provozních podmínek lze vyvodit závěr, zda je možné systémy sloučit či se tato varianta nasazení nedoporučuje.This thesis deals with coexistence of optical systems on a physical layer. The main objective of this thesis is to analyse interactions between multiple optical systems at the physical layer, while partial goal is to compare the integration of these systems under different system conditions. Data for this study were obtained by computer simulation in Optsim environment. On the basis of the resulting models of coexistence of different transmission systems under various system conditions it can be concluded, whether it is recommended to combine certain systems or not

Omega network hash construction

Cryptographic hash functions are very common and important cryptographic primitives. They are commonly used for data integrity checking and data authentication. Their architecture is based on the Merkle-Damgard construction, which takes in a variablelength input and produces a fixed-length hash value. The basic Merkle-Damgard construction runs over the input sequentially, which can lead to problems when the input size is large since the computation time increases linearly. Therefore, an alternative architecture which can reduce the computation time is needed, especially in today's world where multi-core processors and multithreaded programming are common. An Omega Network Hash Construction that can run parallel on multi-core machine has been proposed as alternative hash function's construction. The Omega Network Hash Construction performs better than the Merkle-Damgard construction, and its permutation architecture shows that its security level in term of producing randomness digest value is better than Merkle-Damgard construction

Reformation of offenders in Nigerian correctional institutions

This study examined the correlations between rehabilitation and reformation programmes such as moral instruction and counselling and medical services in Nigerian correctional institutions. A survey design was adopted. The participants were 224 offenders selected from seven correctional institutions in Nigeria. Questionnaire items were administered. Pearson correlation was used to examine the relationships between the variables. The findings reveal a moderate positive significant relationship between moral instruction and rehabilitation; there is a strong positive significant relationship between counselling services and rehabilitation and there is a strong positive relationship between medical care and rehabilitation. It is therefore recommended that Nigerian correctional institutions be in compliance with international best practice. More effort should also be given towards the teaching of moral instruction that has been identified as moderate because the higher the moral instruction given to offenders the higher the offender rehabilitation

Novel high-speed optical transmitters for optical frequency shift keying and inverse-return-to-zero signals.

Pun Siu Sun.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 55-58).Abstract in English and Chinese.ABSTRACT --- p.ii摘要 --- p.ivChapter 1 --- BLACKGROUND AND INTRODUCTION --- p.1Chapter 1.1 --- OPTICAL FREQUENCY SHIFT KEYING (FSK) --- p.1Chapter 1.1.1 --- Basic concepts --- p.1Chapter 1.1.2 --- Applications --- p.3Chapter 1.2 --- MODULATION FORMATS --- p.6Chapter 1.3 --- ORTHOGONAL MODULATION --- p.9Chapter 1.4 --- THESIS ORGANIZATION --- p.11Chapter 2 --- A NOVEL OPTICAL FREQUENCY SHIFT KEYING TRANSMITTER BASED ON POLARIZATION MODULATION --- p.12Chapter 2.1 --- EXISTING OPTICAL FSK TRANSMITTER DESIGNS --- p.12Chapter 2.1.1 --- Optical FSK transmitter based on complementary intensity modulation --- p.12Chapter 2.1.2 --- Optical FSK transmitter based on direct modulation in a DFB laser --- p.13Chapter 2.1.3 --- Optical FSK transmitter based on single side-band (SSB) modulation technique --- p.15Chapter 2.1.4 --- Optical Continuous-Phase FSK (CPFSK) transmitter based on asymmetric Mach-Zehnder modulator --- p.17Chapter 2.1.5 --- Optical FSK transmitter based on phase modulation --- p.18Chapter 2.1.6 --- Summary --- p.20Chapter 2.2 --- PROPOSED OPTICAL FSK TRANSMITTER BASED ON POLARIZATION MODULATION --- p.21Chapter 2.3 --- EXPERIMENTAL DEMONSTARTION --- p.23Chapter 2.4 --- SYSTEM PERFORMANCE --- p.25Chapter 2.5 --- SUMMARY --- p.27Chapter 3 --- OPTICAL RETURN-TO-ZERO FREQUENCY SHIFT KEYING (RZ-FSK) (RZ-FSK) --- p.28Chapter 3.1 --- INTRODUCTION AND MOTIVATION --- p.28Chapter 3.2 --- PREVIOUS NRZ vs. RZ COMPARISON --- p.30Chapter 3.3 --- RZ-FSK TRANSMITTER DESIGN --- p.32Chapter 3.4 --- PERFROMANCE COMPARISON --- p.33Chapter 3.4.1 --- Back-to-back performance --- p.34Chapter 3.4.2 --- Chromatic dispersion tolerance --- p.35Chapter 3.4.3 --- Fiber nonlinearity tolerance --- p.38Chapter 3.5 --- SUMMARY --- p.41Chapter 4 --- A NOVEL OPTICAL TRANSMITTER FOR HIGH-SPEED DIFFERENTIAL PHASE SHIFT KEYING/INVERSE RETURN-TO-ZERO (DPSK/INV-RZ) ORTHOGONALLY MODULATED SIGNALS --- p.42Chapter 4.1 --- INTRODUCTION --- p.42Chapter 4.2 --- PREVIOUS SCHEME --- p.43Chapter 4.3 --- PROPOSED TRANSMITTER DESIGN --- p.45Chapter 4.4 --- EXPERIMENT AND RESULTS --- p.47Chapter 4.5 --- CONCLUSION --- p.51Chapter 5 --- SUMMARY --- p.52Chapter 5.1 --- THESIS SUMMARY --- p.52Chapter 5.2 --- FUTURE WORK --- p.53LIST OF PUBLICATIONS --- p.54REFERENCES --- p.5

Evaluation of Parametric and Hybrid Amplifier Applications in WDM Transmission Systems

Over the past two decades, a rapid expansion of the amount of information to be transferred has been observed. This tendency is explained by the rapid increase of Internet and other service users, as well as with the increasing availability of these services. This rapid growth in the amount of globally transmitted data is also associated with the expansion of the range of services offered, including such resource-consuming services as high-resolution video transmission, videoconferencing, and cloud computing, as well as with increasing popularity of such services. To satisfy this constantly increasing demand for higher network capacity, fiber optical transmission systems have been studied and applied with a growing intensity. Currently, optical transmission systems with wavelength-division multiplexing (WDM) have attracted much attention, as this technology allows using the available optical fiber resources more effectively than alternative technologies

Digital electronic predistortion for optical communications

The distortion of optical signals has long been an issue limiting the performance of communication systems. With the increase of transmission speeds the effects of distortion are becoming more prominent. Because of this, the use of methods known from digital signal processing (DSP) are being introduced to compensate for them. Applying DSP to improve optical signals has been limited by a discrepancy in digital signal processing speeds and optical transmission speeds. However high speed Field Programmable Gate Arrays (FPGA) which are sufficiently fast have now become available making DSP experiments without costly ASIC implementation possible for optical transmission experiments. This thesis focuses on Look Up Table (LUT) based digital Electronic Predistortion (EPD) for optical transmission. Because it is only one out of many possible implementations of EPD, it has to be placed in context with other EPD techniques and other distortion combating techniques in general, especially since it is possible to combine the different techniques. Building an actual transmitter means that compromises and decisions have to be made in the design and implementation of an EPD based system. These are based on balancing the desire to achieve optimal performance with technological and economic limitations. This is partly done using optical simulations to asses the performance. This thesis describes a novel experimental transmitter that has been built as part of this research applying LUT based EPD to an optical signal. The experimental transmitter consists of a digital design (using a hardware description language) for a pair of FPGAs and an analogue optical/electronic setup including two standard DAC integrated circuits. The DSP in the transmitter compensated for both chromatic dispersion and self phase modulation. We achieved transmission of 10.7 Gb/s non-return-to-zero (NRZ) signals with a +4 dBm launch power over 450 km keeping the required optical-signal-to-noise-ratio (OSNR) for a bit-error-rate of 2x10^{-3} below 11 dB. In doing so we showed experimentally, for the first time, that nonlinear effects can be compensated with this approach and that the combination of FPGA-DAC is a viable approach for an experimental setup