Stable Optical Frequency Comb Generation And Applications In Arbitrary Waveform Generation Signal Processing And Optical Data Mining
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| Author | : Sarper Ozharar |
| Publisher | : |
| Total Pages | : 130 |
| Release | : 2008 |
| Genre | : Data mining |
| ISBN | : |
This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was "1 MHz, limited by the electronic waveform generator, and the RF carrier frequency is limited by the bandwidth of the photodetector. Similarly, using parabolic phase modulation together with time division multiplexing, RF chirp extension has been realized. Another application of the optical frequency combs studied in this thesis is real time data mining in a bit stream. A novel optoelectronic logic gate has been developed for this application and used to detect an 8 bit long target pattern. Also another approach based on orthogonal Hadamard codes have been proposed and explained in detail. Also novel intracavity modulation schemes have been investigated and applied for various applications such as a) improving rational harmonic modelocking for repetition rate multiplication and pulse to pulse amplitude equalization, b) frequency skewed pulse generation for ranging and c) intracavity active phase modulation in amplitude modulated modelocked lasers for supermode noise spur suppression and integrated jitter reduction. The thesis concludes with comments on the future work and next steps to improve some of the results presented in this work.
| Author | : Youzhong Sun |
| Publisher | : Springer Nature |
| Total Pages | : 280 |
| Release | : 2020-05-20 |
| Genre | : Education |
| ISBN | : 9811510377 |
English for Specific Purposes (ESP), addressing the communicative needs and practices of particular professional or occupational groups, has developed rapidly in the past fifty years and is now a major force in English language teaching and research. This critical volume helps innovate the theory, practice, and methodology for ESP teaching and research in Asian countries and areas. Promoting communication and enhancing cooperation on ESP research and pedagogy across cultures, it provides ESP scholars, educators and practitioners with an opportunity to benefit from each other’s research and expertise in an age of globalization and digitalization. The volume provides an in-depth analysis of the latest scholarship on English teaching and research for general and specific academic and occupational purposes; the intercultural communication in ESP contexts; corpus linguistics and data-driven instruction for ESP; computer-assisted language learning and mobile-assisted language learning; evaluation of English writing courses; and ESP translation strategies.
| Author | : Nicolas Keith Fontaine |
| Publisher | : |
| Total Pages | : |
| Release | : 2010 |
| Genre | : |
| ISBN | : 9781124025285 |
A technology for accurate generation and characterization of arbitrary optical waveforms scaling to terahertz bandwidth can fundamentally transform modern applications including optical spectroscopy, communications, imaging, and many others. Generation of terahertz bandwidth optical waveforms is challenging because direct electrical-to-optical modulation schemes have bandwidths below 100 GHz due to limitations in current electronic technologies. Similarly, continuous, real-time amplitude and phase characterization of optical waveforms is currently limited to tens of gigahertz. Novel methods which take advantage of frequency multiplexing or temporal multiplexing techniques are necessary to extend the generation and measurement bandwidths. This dissertation focuses on bandwidth-scalable optical arbitrary waveform generation based on a frequency-multiplexed technique using optical frequency combs. Three components are necessary for waveform generation: an optical frequency comb which provides a set of evenly and precisely spaced optical frequencies spanning several terahertz, an optical multiplexer and demultiplexer pair to isolate and combine individual spectral lines, and an array of modulators. Frequency-parallel modulation on each comb line broadens the spectrum of each line to fill the spectral gaps between the lines. Defining the signals applied to each modulator enables synthesis of a continuous and fully specified optical spectrum spanning the entire frequency comb's bandwidth. Full control over the spectrum allows complete specification of the temporal domain waveform via the Fourier transform. Optical arbitrary waveform measurement is a symmetric technique where the signal spectrum is demultiplexed into spectral slices and then each spectral slice is coherently detected with respect to a reference comb line. This dissertation introduces a theory for, and shows demonstrations of, the generation and measurement of optical arbitrary waveforms that are scalable to terahertz bandwidths. Results include high-fidelity generation and measurement of arbitrary shaped optical frequency combs with 10, 20, and 40 GHz comb line spacing using integrated waveform shapers. Single-shot waveform measurements show near quantum-limited characterization across a 200-ps wide optical window with 500 GHz bandwidth. Additionally, an integrated real-time implementation of optical arbitrary waveform measurement demonstrates continuous characterization of 160 GHz bandwidth optical waveforms with a 2 s duration. Terahertz-bandwidth, continuous arbitrary optical waveform generation and measurement provide a unique functionality, which will fundamentally impact many fields of science.
| Author | : |
| Publisher | : |
| Total Pages | : 37 |
| Release | : 2006 |
| Genre | : |
| ISBN | : |
Modelocked semiconductor lasers emit short (1 picosecond) optical pulses at high pulse repetition frequencies (1 GHz) and can be utilized for a wide variety of applications, but are typically geared towards time domain applications, e.g., optical time division multiplexed optical links, optical sampling, etc. Additionally, the periodic nature of optical pulse generation from modelocked semi conductor diode lasers also makes these devices ideal candidates for the generation of high quality optical frequency combs, or multiple wavelengths, in addition to the ultra short temporally stable, high peak intensity optical pulses that one is accustomed to. Modelocked semiconductor lasers are used to generate a set of phase locked optical frequencies on a periodic grid. The periodic and phase coherent nature of the optical frequency combs make it possible for the realization of high performance optical and RF arbitrary waveform synthesis. The resulting optical frequency components can be used for communication applications relying on direct detection, dense WDM, coherent detection WDM, OTDM, and OCDMA. This report highlights recent results in the use of optical frequency combs generated from semiconductors for optical and RF arbitrary waveform generation.
| Author | : Ibrahim Tuna Ozdur |
| Publisher | : |
| Total Pages | : 106 |
| Release | : 2011 |
| Genre | : Mode-locked lasers |
| ISBN | : |
Recently optical frequency combs and low noise RF tones are drawing increased attention due to applications in spectroscopy, metrology, arbitrary waveform generation, optical signal processing etc. This thesis focuses on the generation of low noise RF tones and stabilized optical frequency combs. The optical frequency combs are generated by a semiconductor based external cavity mode-locked laser with a high finesse intracavity etalon. In order to get the lowest noise and broadest bandwidth from the mode-locked laser, it is critical to know the free spectral range (FSR) of the etalon precisely. First the etalon FSR is measured by using the modified Pound-Drever-Hall (PDH) based method and obtained a resolution of 1 part in 106, which is 2 order of magnitude better than the standard PDH based method. After optimizing the cavity length, RF driving frequency and PDH cavity locking point, the mode-locked laser had an integrated timing jitter of 3 fs (1 Hz- 100 MHz) which is, to the best of our knowledge, the lowest jitter ever reported from a semiconductor based multigigahertz comb source. The mode-locked laser produces ~ 100 comb lines with 10 GHz spacing, a linewidth of ~500 Hz and 75 dB optical signal-to-noise ratio. The same system can also be driven as a regeneratively mode-locked laser with greatly improved noise performance. Another way of generating a low noise RF tone is using an opto-electronic oscillator which uses an optical cavity as a high Q element. Due to the harmonic nature of OEOs, a mode selection element is necessary. Standard OEOs use an RF filter having drawbacks such as broad pass band, high loss, and high thermal noise. In our work, a novel optoelectronic scheme which uses an optical filter (Fabry-Perot etalon) as the mode filter instead of an RF filter is demonstrated. This method has the advantage of having ultra-narrow filtering bandwidths (~ 10 kHz for a 10 GHz FSR and 106 finesse) and an extremely low noise RF signal. Experimental demonstration of the proposed method resulted in a 5-10 dB decrease of the OEO noise compared to the conventional OEO setup. Also, by modifying the etalon-based OEO, and using single side band modulation, an optically tunable optoelectronic oscillator is achieved with 10-20 dB lower noise than dual side band modulation. Noise properties of the OEO as a function of optical frequency detuning is also analyzed theoretically and the results are in agreement with experimental results. The thesis concludes with comments on future work and directions.
| Author | : |
| Publisher | : |
| Total Pages | : 14 |
| Release | : 2007 |
| Genre | : |
| ISBN | : |
Optical arbitrary waveform generation using the line-by-line pulse shaping technique has been shown to be sensitive to variations in the offset frequency of the input frequency comb due to time-domain waveform interference. Here we present a frequency-domain model that is able to predict waveform changes arising from offset frequency variations. In experiments we controllably shift the frequency of a comb derived from a phase-modulated CW laser, which allows us to quantitatively investigate waveforms generated by pulse shaping as a function of offset frequency. Experimental data are in excellent agreement with the predictions of our frequency-domain model. In addition, we propose and analyze new waveforms designed for monitoring of offset frequency variations by pulse shaping.
| Author | : Jun Ye |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 373 |
| Release | : 2006-06-15 |
| Genre | : Science |
| ISBN | : 0387237917 |
Over the last few years, there has been a convergence between the fields of ultrafast science, nonlinear optics, optical frequency metrology, and precision laser spectroscopy. These fields have been developing largely independently since the birth of the laser, reaching remarkable levels of performance. On the ultrafast frontier, pulses of only a few cycles long have been produced, while in optical spectroscopy, the precision and resolution have reached one part in Although these two achievements appear to be completely disconnected, advances in nonlinear optics provided the essential link between them. The resulting convergence has enabled unprecedented advances in the control of the electric field of the pulses produced by femtosecond mode-locked lasers. The corresponding spectrum consists of a comb of sharp spectral lines with well-defined frequencies. These new techniques and capabilities are generally known as “femtosecond comb technology. ” They have had dramatic impact on the diverse fields of precision measurement and extreme nonlinear optical physics. The historical background for these developments is provided in the Foreword by two of the pioneers of laser spectroscopy, John Hall and Theodor Hänsch. Indeed the developments described in this book were foreshadowed by Hänsch’s early work in the 1970s when he used picosecond pulses to demonstrate the connection between the time and frequency domains in laser spectroscopy. This work complemented the advances in precision laser stabilization developed by Hall.
| Author | : Pfeifle, Joerg |
| Publisher | : KIT Scientific Publishing |
| Total Pages | : 204 |
| Release | : 2017-05-16 |
| Genre | : Technology (General) |
| ISBN | : 3731506408 |
Energy-efficient Tbit/s optical interconnects are key elements for future communication systems. Three novel optical frequency comb sources are investigated, which have the potential of being integrated in chip-scale Tbit/s transmitters. Such frequency combs provide a large number of carriers. The equidistance of the comb lines helps to minimize spectral guard bands. For each type of comb source, coherent data transmission experiments show the potential for Tbit/s data transmission rates.
| Author | : Mostafa Khalil |
| Publisher | : |
| Total Pages | : |
| Release | : 2020 |
| Genre | : |
| ISBN | : |
"Silicon photonics is the most promising candidate to achieve the high data transmission rates required for future telecommunications bandwidth demands, which require upgraded optical interconnects. Optical modulators, such as Mach-Zehnder modulators, are one of the most important sub-components in any optical communication system. Leveraging the complementary metal-oxide semiconductor (CMOS) fabrication processes, the integration of optical devices become more cost effective and energy efficient. Optical frequency comb has widespread applications in microwave photonics and optical communications as a multi-wavelength source for wavelength division multiplexing and orthogonal frequency division multiplexing systems. The most common approach to generate optical frequency comb is based on the use of optical modulators. On-chip optical frequency comb generation has great flexibility to tune the center frequency based on the frequency of the continuous wave laser, comb spacing, and the number of comb lines based on adjusting the RF signal frequency, power, and phase that is applied to the electro-optic modulator. The limitation of this technique lies in the high insertion loss, especially in cascaded modulators. In this thesis, we investigate two integrated cascaded electro-optic modulators in CMOS-compatible silicon-on-insulator for optical frequency comb generation. The first comprises cascaded push-pull traveling wave Mach-Zehnder modulators (MZM) while the second involves cascaded microring modulators (MRM). The 9 comb lines with a spacing up to 10 GHz and bandwidth of 90 GHz for the cascaded MZM, and 5 comb lines with a spacing up to 10 GHz and a bandwidth of 50 GHz for the cascaded MRM. The measured temporal waveforms corresponding to the generated quasi-rectangular combs match with the sinc-shaped Nyquist pulses which are well-known for its high spectral efficiency and have zero inter-symbol interference. Lastly, we summarize and compare the performance of both modulators"--
| Author | : Auro Michele Perego |
| Publisher | : CRC Press |
| Total Pages | : 0 |
| Release | : 2024-07-31 |
| Genre | : Science |
| ISBN | : 9781032548081 |
"In this book we will discuss both the operating principles and performance limits of a wide range of device technologies, and the technological requirements of applications. We will identify close synergies where technology capabilities and application requirements are closely aligned, and opportunities for generic optical frequency combs where multiple solutions and applications exist simultaneously. The main topics to be covered will include:(i) Different sources and methods of optical frequency combs generation including mode-locked lasers, optical resonators, opto-electronics, and nonlinear fibres. (ii) Applications of optical frequency combs in different technologies including sensing, spectroscopy, metrology, distance ranging and optical communications. (iii) Blue-sky novel physical concepts and promising future research directions for the field. With this book we aim at showcasing top level advances by key players in a multifaceted research ecosystem, and at the same time at providing a valuable service to our research community, by offering a comprehensive review which, at the same time, highlights challenges to be solved and promising future directions. This book will be a valuable resource for academics and researchers working in optical frequency combs, and more broadly in photonics and laser physics. It will also be of interest to postgraduate and graduate students of photonics and laser physics"
