Computation of Dispersion Penalty for the Analysis of WDM Link Quality

The provisioning of light path over WDM/DWDM network is a challenging factor, which depends on various physical layer impairments such as dispersion in fiber. We proposed a light path provisioning mechanism by considering the effect of dispersion in fiber termed as dispersion penalty, which is the prominent effect at high speed WDM network. In the case of non-ideal filter, light path provisioning without considering the physical layer impairments does not satisfy the signal quality guaranteed transmission. In this algorithm, Quality of Service is described in terms of dispersion penalty values with an assumption that the entire client has a requirement of penalty less than 2 Db. Here we have analyzed the degradation in bit rate due to the effect of dispersion. The maximum possible length of fiber is also reduced due to high dispersion in fiber. Dispersion penalty is the increment in the received power to eliminate the effect of some undesirable distortion in optical fiber. Dispersion penalty is calculated in terms of bit rate and band width for each data path. The proposal of dispersion penalty budgeting is to ensure that the optical power reaching the receiver is adequate under all circumstances. The proposed algorithm defines a mechanism for effective light path provisioning by comparing the requirement of client and the available resources of the network

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

Polarization modulation instability in a Manakov fiber system

The Manakov model is the simplest multicomponent model of nonlinear wave theory: It describes elementary stable soliton propagation and multisoliton solutions, and it applies to nonlinear optics, hydrodynamics, and Bose-Einstein condensates. It is also of fundamental interest as an asymptotic model in the context of the widely used wavelength-division-multiplexed optical fiber transmission systems. However, although its physical relevance was confirmed by the experimental observation of Manakov (vector) solitons in a planar waveguide in 1996, there have in fact been no quantitative experiments confirming its validity for nonlinear dynamics other than soliton formation. Here, we report experiments in optical fiber that provide evidence of passband and baseband polarization modulation instabilities in a defocusing Manakov system. In the spontaneous regime, we also reveal a unique saturation effect as the pump power increases. We anticipate that such observations may impact the application of this minimal model to describe and understand more complicated phenomena in nature, such as the formation of extreme waves in multicomponent systems

Electronic impairment mitigation in optically multiplexed multicarrier systems

In order to improve the performance of optically multiplexed multicarrier systems with channel spacing equal to the symbol rate per carrier, we propose and systematically investigate an electronic signal processing technique to achieve near-interchannel crosstalk free and intersymbol-interference (ISI) free operation. We theoretically show that achieving perfect orthogonality between channels in these systems, together with ISI free operation as needed in generic communication systems, requires the shaping of the spectral profiles of not only the demultiplexing filter, but also the signal of each channel before demultiplexing. We develop a novel semianalytical method to quantitatively analyze the levels of residual crosstalk and ISI arising from nonideal system response in these systems. We show that by prefiltering the signal to ensure that the system impulse response before channel demultiplexing approaches the targeted condition, the residual crosstalk due to imperfect orthogonality can be significantly mitigated and the necessity for carrier phase control in single-quadrature format-based system can be relaxed. Further combining prefiltering and receiver-side postfiltering to adaptively trim the demultiplexing filter enhances the performance. The use of the combined digital signal processing (DSP) in coherent-detection quadrature phase-shifted keying (QPSK)-based optically multiplexed multicarrier system shows that this method outperforms conventional QPSK-based multicarrier system without DSP or with only receiver-side DSP, especially when the responses of the transmitter and the demultiplexing filter are not precisely designed and the sampling rate of the analogue-to-digital converter is not sufficiently high. In addition, the inclusion of ISI free operation, with this aspect similar to the reshaping method in conventional wavelength-division-multiplexing systems, allows the relaxation of the modulation bandwidth and chromatic dispersion compensation

Advanced DSP Techniques for High-Capacity and Energy-Efficient Optical Fiber Communications

The rapid proliferation of the Internet has been driving communication networks closer and closer to their limits, while available bandwidth is disappearing due to an ever-increasing network load. Over the past decade, optical fiber communication technology has increased per fiber data rate from 10 Tb/s to exceeding 10 Pb/s. The major explosion came after the maturity of coherent detection and advanced digital signal processing (DSP). DSP has played a critical role in accommodating channel impairments mitigation, enabling advanced modulation formats for spectral efficiency transmission and realizing flexible bandwidth. This book aims to explore novel, advanced DSP techniques to enable multi-Tb/s/channel optical transmission to address pressing bandwidth and power-efficiency demands. It provides state-of-the-art advances and future perspectives of DSP as well

Optical Transmission Systems based on the Nonlinear Fourier Transformation

Solitons are stable pulse shapes, which propagate linearly and maintain their shape despite the highly nonlinear fiber optical channel. A challenge in the use of these signal pulses in optical data transmission is to multiplex them with high efficiency. One way to multiplex many solitons is the nonlinear Fourier transform (NFT). With the help of the NFT, signal spectra can be calculated which propagate linearly through a nonlinear channel. Thus, in perspective, it is possible to perform linear transmissions even in highly nonlinear regions with high signal power levels. The NFT decomposes a signal into a dispersive and a solitonic part. The dispersive part is similar to spectra of the conventional linear Fourier transform and dominates especially at low signal powers. As soon as the total power of a signal exceeds a certain limit, solitons arise. A disadvantage of solitons generated digitally by the NFT is their complex shape due to, for example, high electrical bandwidths or a poor peak-to-average power ratio. In the course of this work, a scalable system architecture of a photonic integrated circuit based on a silicon chip was designed, which allows to multiplex several simple solitons tightly together to push the complex electrical generation of higher order solitons into the optical domain. This photonic integrated circuit was subsequently designed and fabricated by the Institute of Integrated Photonics at RWTH Aachen University. Using this novel system architecture and additional equalization concepts designed in this work, soliton transmissions with up to four channels could be successfully realized over more than 5000 km with a very high spectral efficiency of 0.5 b/s/Hz in the soliton range