Some applications of optical fibre sensor.

by Poon Wing-chak.Thesis (M.Phil.)--Chinese University of Hong Kong, 1989.Includes bibliographies

US long distance fiber optic networks: Technology, evolution and advanced concepts. Volume 2: Fiber optic technology and long distance networks

The study projects until 2000 the evolution of long distance fiber optic networks in the U.S. Volume 1 is the Executive Summary. Volume 2 focuses on fiber optic components and systems that are directly related to the operation of long-haul networks. Optimistic, pessimistic and most likely scenarios of technology development are presented. The activities of national and regional companies implementing fiber long haul networks are also highlighted, along with an analysis of the market and regulatory forces affecting network evolution. Volume 3 presents advanced fiber optic network concept definitions. Inter-LATA traffic is quantified and forms the basis for the construction of 11-, 15-, 17-, and 23-node networks. Using the technology projections from Volume 2, a financial model identifies cost drivers and determines circuit mile costs between any two LATAs. A comparison of fiber optics with alternative transmission concludes the report

Carrier Phase Recovery for Coherent Optical Transmission Systems

This thesis presents studies concerned with the evaluation of the suitablility of an optical-phase-locked-loop (OPLL) as a component in a coherent optical transmission network. The performance of various binary optical transmission schemes, measured by the probability of error (Bit Error Rate), is presented. The linewidths of semiconductor diode lasers are, in general, not optimally suited to coherent transmission formats and therefore an additional power penalty must be paid if such sources are to be used. This power penalty is included in the analysis of a binary PSK transmission. The performance analysis of coherent transmission schemes is extended to encompass multi-level signalling formats. It is shown that, with the use of a sufficient number of signalling levels, these schemes can provide a receiver sensitivity which is better than a shot noise limited binary PSK transmission even when subject to the effects of high laser line width. A discussion on the properties of the laser diode, which are of interest in the design of a coherent optical transmission scheme (the source linewidth, modulation charateristics, wavelength tunablity and frequency and power stability), is provided. Measurements of these properties is given along with documentation of experimental attempts to reduce the linewidth of the laser emission. Linewidth reductions from between five and ten Megahertz down to tens of kilohertz were obtained. An analysis of the performance of an OPLL, taking into consideration the effect of phase instability of the laser diode source, is given. This analysis predicts that present day laser diodes can be used in the construction of the OPLL provided that the loop bandwidth is sufficiently large to account for the laser instability, while not being excessively large such that the performance is impaired by the influence of shot noise. This analysis is extended to describe the effect which the loop transport delay will have on such a loop, as the required loop bandwidth is extended. Similar calculations are performed to evaluate the effect of the loop receiver amplifier bandwidth. An evaluation of the OPLL response in the time domain, with the use of the Root Locus construction technique and a digital simulation, is presented. This analysis supports the findings of the analysis described above. The simulation of the loop dynamic response is found to be in reasonable agreement with the experimental findings of a previous worker. The components for the construction of an optical heterodyne-phase-locked-loop were assembled and attempts were made to lock both free running laser diodes and external cavity line-narrowed diodes. Reliable aquisition of lock was never achieved in any of the experiments performed despite the fact that beat notes of less than 50 kHz were achieved on a regular basis. The main factor which frustrated the succesful implenentation of the OPLL was deduced to have been mechanical disturbances, of the order of nanometers in magnitude, in the reflecting mirror of the external cavity sources. Hysteresis in the mechanical positioning equipment used to control the external reflector positioning was responsible for limiting the effectiveness of the frequency control loop. Experimentation was terminated by the deterioration of the laser sources, the suspected cause of which was the clustering of material defects within the active region of the device

Cognitive and Autonomous Software-Defined Open Optical Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen

Coherent wavelength division multiplexing: a novel transmission format for high spectral density optical communication networks

In this thesis a novel transmission format, named Coherent Wavelength Division Multiplexing (CoWDM) for use in high information spectral density optical communication networks is proposed and studied. In chapter I a historical view of fibre optic communication systems as well as an overview of state of the art technology is presented to provide an introduction to the subject area. We see that, in general the aim of modern optical communication system designers is to provide high bandwidth services while reducing the overall cost per transmitted bit of information. In the remainder of the thesis a range of investigations, both of a theoretical and experimental nature are carried out using the CoWDM transmission format. These investigations are designed to consider features of CoWDM such as its dispersion tolerance, compatibility with forward error correction and suitability for use in currently installed long haul networks amongst others. A high bit rate optical test bed constructed at the Tyndall National Institute facilitated most of the experimental work outlined in this thesis and a collaboration with France Telecom enabled long haul transmission experiments using the CoWDM format to be carried out. An amount of research was also carried out on ancillary topics such as optical comb generation, forward error correction and phase stabilisation techniques. The aim of these investigations is to verify the suitability of CoWDM as a cost effective solution for use in both current and future high bit rate optical communication network

Advanced digital signal processing for coherent optical OFDM transmissions

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) has been actively considered as a potential candidate for long-haul transmission and 400 Gb/s to 1 Tb/s Ethernet transport because of its high spectral efficiency, efficient implementation, flexibility and robustness against linear impairments such as chromatic dispersion and polarization mode dispersion. However, due to the long symbol duration and narrow subcarrier spacing, CO-OFDM systems are sensitive to laser phase noise and fibre nonlinearity induced penalties. As a result, the development of CO-OFDM transmission technology crucially relies on efficient techniques to compensate for the laser phase noise and fibre nonlinearity impairments. In this thesis, high performance and low complexity digital signal processing techniques for laser phase noise and fibre nonlinearity compensation in CO-OFDM transmissions are demonstrated. For laser phase noise compensation, three novel techniques, namely quasipilot-aided, decision-directed-free blind and multiplier-free blind are introduced. For fibre nonlinear compensation, two novel techniques which are referred to as phase conjugated pilots and phase conjugated subcarrier coding, are proposed. All these abovementioned digital signal processing techniques offer high performances and flexibilities while requiring relatively low complexities in comparison with other existing phase noise and nonlinear compensation techniques. As a result of the developments of these digital signal processing techniques, CO-OFDM technology is expected to play a significant role in future ultra-high capacity optical network. In addition, this thesis also presents preliminary study on nonlinear Fourier transform based transmission schemes in which OFDM is a highly suitable modulation format. The obtained result paves the way towards a truly flexible nonlinear wave-division multiplexing system that allows the current nonlinear transmission limitations to be exceeded

A system model for the effect of Polarization Mode Dispersion on digital modulated optical signals in single mode fibers

A comprehensive systems model that retains the discrete nature of the output delay distribution in order to accurately characterize the pulse broadening due to Polarization Mode Dispersion (PMD) is developed in this thesis. PMD in optical channels has been a critical factor limiting high-speed data transmission over long distances in optical networks. PMD is a source of Inter Symbol Interference (ISI) and its impact increases with the transmission data rate. Since economical adaptive compensation schemes are currently unavailable, it is essential to characterize this impairment to completely understand its impact and develop effective countermeasures. An incremental approach has been developed to methodically grow the output DGD distribution of single mode optical fibers. It provides the flexibility to change individual beat segment delays and enables the simulation and characterization of the distributed and the deterministic effects of PMD. The model also accurately evaluates the impact of the PMD impairment on the performance of optical networks in terms of Q. Results from comparing performance penalties at 10G bus, 40G bps and 100 Gbps data rates of transmission are in agreement with published trends