The aim of this master thesis is comparation of simulation tools OptSim™ and PHOTOSS which are used to create simulations of data traffi cs in access and metropolitan networks. The outcome of this thesis is three laboratory exercises and their theoretical bases which should explain the way of working in diff erent simulation environments to students.

In this work an optical wireless test link for studying of atmospheric phenomena in the optical bands of 830 nm and 1550 nm is described. The WDM technology involving technology of optical fibers is included into transmitter of the link. The measuring devices for measuring power, spectrum and polarization control are included into receiver of the link. The outcomes of this work are both measuring chain design and verification of its functionality.

The aim of this thesis was introducing the options of conversion between OTDM and WDM technologies. Since this issue is rather extensive, first of all the principle of optical transmission system is described. One chapter presents the effects influencing the optical transmissions. Material absorption, linear and nonlinear scattering and bending losses are mentioned in terms of fiber losses, followed by description of waveguide, chromatic and polarization-mode dispersion of optical fibers. Last part of the chapter presents nonlinear effects, including self-phase modulation, cross-phase modulation and four-wave mixing. The practical part of the thesis deals with multichannel systems. The principles of frequency, space a hybrid multiplexing are explained. Multichannel systems with optical time domain multiplexing and waveguide multiplexing are described in detail and compared. The elements of the transmission chain of multiplex, such as different types of lasers, detectors, modulators, optical amplifiers, splitters, couplers, MUX and DEMUX are discussed. The next part of the thesis was aimed at suggesting the model of mutual conversion between OTDM and WDM systems. First of all, the previously performed experiments concerning the conversion between OTDM and WTM were evaluated. Then the model of OTDM/WDM/OTDM conversion was designed, with explanation of its parts and their function. The general recommendations for practical implementation were are also included. Due to the limited amount of time reserved for access to the simulation program Optsim, the simulations were performed only for certain parts of the proposed conversion model. At the end of the thesis, the proposed model is evaluated.

The aim of this thesis is to explain the problems of optical access networks with wavelength division multiplexers, main purpose is to demonstrate the difference between theoretical and real measurement. The work is divided into several thematic areas. The introduction outlines the basic of telecommunications, fiber optics lasers, single mode, multimode, lasers fibers cables & cores, splitters division multiplexing system, there are known solutions discussed fundamental wavelength multiplexes and their possible combinations. The following chapter deals with the active elements such as AON, PON, which are essential part xWDM systems such as optical lasers, detectors and amplifiers. Another chapter focuses on passive elements, which form a key part of the wavelength multiplex. Methods of measurement of WDM/PON networks are discussed in the following part. The next section describes the topology used active and passive optical networks. The penultimate part of the work consists of architecture & technology of xWDM such as GPON and WDM-PON networks and comparing their transmission parameters. The final part of the paper presents the results of practical experimental measurements of optical access networks with wavelengths division multiplex while these results are compared with the theoretical output & methods of Optical lost test, OTDR & LSPM, with advantage & disadvantage of every methods. The second part of practical is the draft to the connection resident housing units of 30 houses, boarding-house (10 rooms) and 2 shops, 20 km distant from exchange. With comparing the possibilities of two options- passive and active optical network- PON system – WDM- Wave multiplex. Suggest the possibility of measuring and monitoring the created network.

The main goal of the diploma thesis is DWDM simulation of optical network, defined by recommandation ITU-T. Optical network includes 16 communication channels with length of fiber 50 km. Each channel have to be set with bandwith 50GHz and Bit rate with minimal value 10Gbit/s. The final simulation model includes 8 types of modulation techniques. The result of the thesis is comparison modulation techniques in terms of usability of bandwith and comparison of the quality of transfer

As WDM results in an ever-increasing trend of traffic concentration, any failure on a single fiber-link or a single switching node will be catastrophic. Rapid restoration can recover the affected traffic so as to make the network more robust and reliable. The conventional restoration methods are designed mostly for reconfiguring the network topology; they are not immune from service interruption. In this thesis, an effective algorithm called backup-path-wavelength rearrangement scheme is proposed to reduce the connection blocking probability in an all-optical network. The proposed scheme performs wavelength retuning on the backup paths to improve the acceptance probability for new connection requests and introduce zero service interruption to the traffic in the network. The performance evaluation indicates that the connection blocking probability can be decreased greatly by the proposed scheme. The combination of BPWR and traffic grooming can efficiently alleviate the wavelength continuity constraint.

No description available.

<p>Reflective semiconductor optical amplifiers (RSOA) are widely used in wavelength-division-multiplexed passive optical networks (WDM-PON). RSOAs in optical network units (ONUs) are operated in the gain saturation region so that the amplitude squeezing effect can be used to erase the information on downstream signals, however, the upstream signals go through the same RSOA need to be amplified.</p> <p>In order to use one RSOA to satisfy the need of erasing the information on downstream signal by using amplitude squeezing effect and amplifying the upstream signal at the same time, an asymmetric RSOA design is proposed and demonstrated in this thesis. The ridge width becomes narrower along the traveling direction of the downstream signal so that the downstream signal can be amplified in the saturation region of the RSOA. At the same time, the ridge width increases in the traveling direction of the upstream signal, so that the modulated upstream signal can be amplified by the asymmetric RSOA. In this thesis, I mainly focus on the designing of the structure of the RSOA to enlarge the gain difference between upstream and downstream gain. Difference between wide end and narrow end effective indices, cavity length, the way that effective index changes from the wide end to the narrow end and bias current are factors that can affect the gain difference. How the device performance is affected by the factors were analyzed. An optimized structure of asymmetric RSOA is then proposed according to the effects of the factors. The performance of the asymmetric RSOA, including gain dynamic performance, saturation output power, and upstream output power, is compared with symmetric RSOA. The asymmetric RSOA shows better performance in erasing the downstream signal information as well as amplifying upstream signal.</p> / Master of Applied Science (MASc)

This dissertation investigates the design and performance issues of a recently demonstrated technique, termed as spectrum-slicing, for implementing wavelength-division-multiplexing (WDM) in optical fiber systems. Conventional WDM systems employ laser diodes operating at discrete wavelengths as carriers for the different data channels that are to be multiplexed. Spectrum-slicing provides an attractive low-cost alternative to the use of multiple coherent lasers for such WDM applications by utilizing spectral slices of a broadband noise source for the different data channels. The principal broadband noise source considered is the amplified spontaneous emission (ASE) noise from an optical amplifier. Each slice of the spectrum is actually a burst of noise that is modulated individually for a high capacity WDM system. The stochastic nature of the broadband source gives rise to excess intensity noise which results in a power penalty at the receiver. One way to minimize this penalty, as proposed and analyzed for the first time in this work, is to use an optical preamplifier receiver. It is shown that when an optical preamplifier receiver is used, there exists an optimum filter bandwidth which optimizes the detection sensitivity (minimizes the average number of photons/bit) for a given error probability. Moreover the evaluated detection sensitivity represents an order of magnitude ( > 10 dB) improvement over conventional PIN receiver-based detection techniques for such spectrum-sliced communication systems. The optimum is a consequence of signal energy fluctuations dominating at low values of the signal time bandwidth product (m), and the preamplifier ASE noise dominating at high values of m. Operation at the optimum bandwidth renders the channel error probability to be a strong function of the optical bandwidth, thus providing motivation for the use of forward error correction coding (FEC). System capacity (for BER = ) is shown to be 23 Gb/s without coding, and 75 Gb/s with a (255,239) Reed Solomon code. The effect of non-rectangular spectra on receiver sensitivity is investigated for both OOK and FSK transmission, assuming the system (de)multiplexer filters to be N'th order Butterworth bandpass. Although narrower filters are recommended for improving power budget, it is shown that system penalty due to filter shape may be kept < 1 dB by employing filters with N > 2. Moreover spectrum-sliced FSK systems using optical preamplifier receivers are shown, for the first time, to perform better in a peak optical power limited environment. Performance-optimized spectrum-sliced WDM systems have potential use in both local loop and long-distance fiber communication systems which require low-cost WDM equipment for high data rate applications. / Ph. D.

In this dissertation the performance of a novel variant of a return-to-zero (RZ) modulation format, based on square-wave phase modulation and filtering of a continuous-wave (CW) signal, is investigated and compared with various modulation formats considered in the literature. We call this modulation format continuous-wave square-wave (CWSW). With CWSW an RZ pulse train is generated by phase modulating the CW signal by a periodic square-wave phase function having an amplitude of and frequency of half the bit rate, and then filtering the signal. The filter performs phase-to-amplitude conversion, resulting in an alternate-sign RZ pulse train, which is shown to be resistant to fiber dispersion. The alternate-sign RZ pulse train is then amplitude modulated with the data before the transmission. Alternate signs between adjacent pulses makes this signal format robust to impairments caused by the optical fiber, similar to a conventional alternate-sign RZ signal format. However, the unique property of the CWSW signal format is that individual pulses can induce peak intensity enhancement (PIE), a phenomenon by which the peak of a pulse increases during the initial propagation in the presence of dispersion. The PIE in effect delays the decrease in the pulse peak, which represents the signal level for bit 1. Thus, the eye opening at the receiver is improved. An analytically tractable model is developed to explain the occurrence of the PIE, which cannot be achieved with a conventional pulse shape. The sources of performance degradations for different modulation formats in single-channel 40 Gb/s systems are also discussed in this dissertation. Various transmission system configurations of practical interest are considered and the performance of CWSW is compared with alternative modulation formats. It is found that the CWSW signal format performs significantly better than the other considered modulation formats in systems not employing dispersion compensation and is comparable to the others in dispersion-managed systems. Furthermore, the transmitter configuration of the CWSW signal format is simpler than the other approaches. / Ph. D.