254 research outputs found

    Adaptive High Linearity Intensity Modulator for Advanced Microwave Photonic Links

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    This chapter, first, presents the motivation behind the need for adaptive, highly linear electro-optic modulators and an overview of the different optical linearization approaches of electro-optic modulators. Then, the figures of merits in terms of linearity performance are described and analyzed. Next, the chapter focuses on one excellent linearization approach called interferometric modulator with phase-modulating and cavity-modulating components (IMPACC). Here, we model IMPACC by simulating each of the key building blocks separately before putting them together as IMPACC modulator. This adaptive IMPACC design is compared to typical Mach-Zehnder interferometer (MZI) based modulators, and ring-assisted Mach-Zenhder interferometer (RAMZI) modulators. Theoretical analysis and results show that the IMPACC provides both superior linearity performance and unique adaptive feature that can be used to compensate for manufacturing tolerances, thus, providing extra flexibility in terms of device manufacturability as well as system integration

    Silicon photonics devices for integrated analog signal processing and sampling

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    Silicon photonics offers the possibility of a reduction in size weight and power for many optical systems, and could open up the ability to build optical systems with complexities that would otherwise be impossible to achieve. Silicon photonics is an emerging technology that has already been inserted into commercial communication products. This technology has also been applied to analog signal processing applications. MIT Lincoln Laboratory in collaboration with groups at MIT has developed a toolkit of silicon photonic devices with a focus on the needs of analog systems. This toolkit includes low-loss waveguides, a high-speed modulator, ring resonator based filter bank, and all-silicon photodiodes. The components are integrated together for a hybrid photonic and electronic analog-to-digital converter. The development and performance of these devices will be discussed. Additionally, the linear performance of these devices, which is important for analog systems, is also investigated

    LINEAR RING RESONATOR MODULATOR FOR MICROWAVE PHOTONIC LINKS

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    Modulators within Microwave photonic links (MPLs) encode Radio Frequency (RF) signal information to the optical domain for transmission in applications such as wireless access networks and antenna remoting exploiting advantages optical fiber offers over RF coaxial cables including bandwidth, loss, size, weight, and immunity to electromagnetic interference. A critical figure-of-merit in MPLs is spur-free-dynamic-range (SFDR) defining the range of RF signal power a MPL transmits without distortion. Current Mach-Zehnder Interference (MZI) modulators used in MPLs limit the SFDR because of the associated nonlinear sinusoidal transfer function. A rigorous theoretical method is developed followed by design, fabrication, and testing to investigate a linear ring resonator modulator (RRM) modulator for MPLs. The linear nature of the Lorentzian transfer function for the RRM is utilized over the sinusoidal transfer function within MZI modulators offering significant improvement in MPL SFDR. A novel bias voltage adjustment method is developed for practical implementations improving SFDR of 6 dB versus MZI at 500 MHz noise bandwidth. RRM is shown to be applicable for applications requiring high operational frequencies while in a limited operational bandwidth such as millimeter-wave wireless networks. To improve RRM SFDR in wide operational bandwidths a novel dual ring resonator modulator (DRRM) design is demonstrated. DRRM suppresses the third order intermodulation distortion in a frequency independent process removing SFDR limits of RRM

    Modulation Linearity Characterization of Si Ring Modulators

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    Modulation linearity of Si ring modulators (RMs) is investigated through the numerical simulation based on the coupled-mode theory and experimental verification. Numerical values of the key parameters needed for the simulation are experimentally extracted. Simulation and measurement results agree well. With these, the influence of input optical wavelength and power on the Si RM linearity are characterized

    Analytical model for calculating the nonlinear distortion in silicon-based electro-optic Mach-Zehnder modulators

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    [EN] In this study, an analytical model for calculating the nonlinear harmonic/intermodulation distortion for RF signals in silicon-based electro-optic modulators is investigated by considering the nonlinearity on the effective index change curve with the operation point and the device structure simultaneously. Distortion expressions are obtained and theoretical results are presented showing that optimal modulator parameters can be found to linearize it. Moreover, the harmonic distortion of a 1 mm silicon-based asymmetric MZI is RF characterized and used to corroborate the theoretical results. Based on the present model, the nonlinear distortion in terms of bias voltage or operating wavelength is calculated and validated by comparing with the experimental data, showing a good agreement between measurements and theory. Analog photonic link quality parameter like carrier-todistortion is one of the parameters that can be found with that model. Finally, the modulation depth is measured to assure that no over-modulation is produced.This work was supported by the funding from the European Commission under project HELIOS (pHotonics Electronics functional Integration on CMOS), FP7-224312. The work of P. Sanchis and J.-M. Fedeli was supported by the funding funding from TEC2012-38540 LEOMIS, TEC2008-06333 SINADEC, and PROMETEO-2010-087. The work of F. Y. Gardes, D. J. Thomson and G. T. Reed was supported by funding received from the UK EPSRC funding body under the grant "UK Silicon Photonics."Gutiérrez Campo, AM.; Brimont, ACJ.; Herrera Llorente, J.; Aamer, M.; Thomson, DJ.; Gardes, FY.; Reed, GT.... (2013). Analytical model for calculating the nonlinear distortion in silicon-based electro-optic Mach-Zehnder modulators. Journal of Lightwave Technology. 31(23):3603-3612. https://doi.org/10.1109/JLT.2013.2286838S36033612312

    Integrated photonic analog-to-digital converters

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 161-172).Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits and 52 dBc spur-free dynamic range (SFDR) using a discrete-component photonic ADC. This corresponds to 15 fs jitter, a 4-5 times improvement over the jitter of the best electronic ADCs, and an order of magnitude improvement over the jitter of electronic ADCs operating above 10 GHz. The feasibility of a practical photonic ADC is demonstrated by creating an integrated ADC with a modulator, filters, and photodetectors fabricated on a single silicon chip and using it to sample a 10 GHz signal with 3.5 effective bits and 39 dBc SFDR. In both experiments, a sample rate of 2.1 GSa/s was obtained by interleaving two 1.05 GSa/s channels; higher sample rates can be achieved by increasing the channel count. A key component of a multi-channel ADC - a dual multi-channel high-performance filter bank - is successfully implemented. A concept for broadband linearization of the silicon modulator, which is another critical component of the photonic ADC, is proposed. Nonlinear phenomena in silicon microring filters and their impact on ADC performance are analyzed, and methods to reduce this impact are proposed. The results presented in the thesis suggest that a practical integrated photonic ADC, which successfully overcomes the electronic jitter bottleneck, is possible today.by Anatol Khilo.Ph.D

    High-efficiency silicon photonic modulator using coupled Bragg grating resonators

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    We propose a novel design of a silicon photonic modulator that has a high modulation efficiency and that is tolerant to temperature variations. A series of phase-shifted Bragg gratings are placed in each arm of a Mach-Zehnder interferometer in order to provide enhanced phase modulation. The slow light effect in these ultra-compact coupled resonators improves phase modulation efficiency compared to conventional silicon phase shifters. These Bragg grating cavities are designed such that the optical bandwidth is increased compared to other coupled resonators such as micro-rings. This improved bandwidth reduces the temperature sensitivity of the devices. We present in detail how to optimize these modulators considering properties such as modulation efficiency (Vπ×L), optical modulation amplitude (OMA), and optical bandwidth (λBW); the latter property determining the operating temperature range (T). As examples, we present two designs that meet different target specifications for short-reach or long-haul applications. We further provide a model, based on coupled mode theory, to investigate the dynamic response of the proposed modulators. A large signal analysis is performed using finite difference time domain (FDTD) in order to simulate on/off keying (OOK) modulation and eye diagrams up to 110 Gb/s

    Design and optimization of high-speed silicon linear optical modulators.

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    Lo, Ming Gai Stanley.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.Includes bibliographical references (leaves 131-135).Abstracts in English and Chinese.Title Page --- p.iAbstract --- p.iiAcknowledgements --- p.vTable of Contents --- p.viiList of Figures --- p.ixList of Tabic --- p.xivChapter Chapter 1: --- Introduction --- p.1Chapter 1.1 --- Photonic Integrated Circuits --- p.1Chapter 1.2 --- Silicon Photonics --- p.7Chapter 1.3 --- Optical Modulators --- p.15Chapter 1.4 --- Modulation Mechanisms in Silicon --- p.19Chapter 1.5 --- Motivation --- p.27Chapter 1.6 --- Thesis Outline --- p.28Chapter Chapter 2: --- Use of Silicon-bascd Modulators in Radio-over-fiber Optical Links --- p.29Chapter 2.1 --- Modeling of Linearity of Silicon Carrier Depletion-based Modulators --- p.31Chapter 2.2 --- Modeling of Dependence of Linearity on Various Diode Structures --- p.45Chapter 2.3 --- Experiment of Radio-over-Fiber Signal Transmission by a Carrier-Injection Silicon Microring Modulator --- p.52Chapter 2.3.1 --- Device Fabrication --- p.53Chapter 2.3.2 --- Experimental Setups --- p.59Chapter 2.3.3 --- Experimental Results --- p.61Chapter 2.4 --- Summary --- p.66Chapter Chapter 3: --- Novel Diode Structures and T-Rail Travelling-Wave Electrodes to Enhance the Performance of Depletion-based Modulators --- p.67Chapter 3.1 --- Requirements of Diode Design for Depletion-based Optical Modulators --- p.70Chapter 3.2 --- Diode Design Principle --- p.72Chapter 3.3 --- Modeling Results of Vertical-Junction p-n Diodes --- p.79Chapter 3.4 --- Fabrication Process of the Silicon Modulator --- p.88Chapter 3.5 --- Experimental Results of the Fabricated Devices --- p.92Chapter 3.6 --- T-Rail Travelling-Wave Electrodes --- p.102Chapter 3.6.1 --- The Limiting Factors to the Speed of Depletion-based Modulators --- p.102Chapter 3.6.2 --- The Design Principle of T-Rail Travelling-Wave Electrodes --- p.104Chapter 3.6.3 --- The Fabricated Devices --- p.111Chapter 3.7 --- Summary --- p.112Chapter Chapter 4: --- Conclusion and Future Work --- p.113Chapter 4.1 --- Conclusion --- p.113Chapter 4.1.1 --- Use of Silicon-based Modulators in Radio-over-fiber Optical Links --- p.113Chapter 4.1.2 --- Novel Diode Structures and T-Rail Travelling-Wave Electrodes to Enhance the Performance of Depletion-based Modulators --- p.114Chapter 4.2 --- Future Work --- p.116Chapter Appcndix-A --- List of Symbols --- p.118Chapter Appcndix-B --- List of Abbreviations --- p.120Chapter Appcndix-C --- Principles of Various Optical Structures of Modulators --- p.123Chapter Appcndix-D --- Modeling of Refractive Index Change by Free-Carrier Plasma Dispersion Effcct --- p.127Reference --- p.131Publication List --- p.13
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