Fabrication of thermo-optic switch in silicon-on-insulator

Silicon-on-insulator technology has been used to fabricate 2 x 2 thermo-optic switches. The switch shows crosstalk of -23.4 dB and extinction ratio of 18.1 dB in the bar-state. The switching speed is less than 30 mus and the power consumption is about 420 mW The measured excess loss is 1.8 dB. These merits make the switch more attractive for applications in wavelength division multiplexing.

SiGe/Si resonant-cavity-enhanced photodetectors for 1.3 mu m operation fabricated using wafer bonding techniques

A SiGe/Si multiple-quantum-well resonant-cavity-enhanced (RCE) photodetector for 1.3 mum operation was fabricated using bonding reflector process. A full width at half maximum (FWHM) of 6 nm and a quantum efficiency of 4.2% at 1314 nm were obtained. Compared to our previously reported SiGe RCE photodetectors fabricated on separation-by-implanted-oxygen wafer, the mirrors in the device can be more easily fabricated and the device can be further optimized. The FWHM is expected to be less than 1 nm and the detector is fit for density wavelength division multiplexing applications. (C) 2002 American Institute of Physics.

Wavelength tunable distributed Bragg reflector laser integrated with electro-absorption modulator by a combined method of selective area growth and quantum well intermixing - art. no. 68240N

Wavelength tunable electro-absorption modulated distributed Bragg reflector lasers (TEMLs) are promising light source in dense wavelength division multiplexing (DWDM) optical fiber communication system due to high modulation speed, small chirp, low drive voltage, compactness and fast wavelength tuning ability. Thus, increased the transmission capacity, the functionality and the flexibility are provided. Materials with bandgap difference as large as 250nm have been integrated on the same wafer by a combined technique of selective area growth (SAG) and quantum well intermixing (QWI), which supplies a flexible and controllable platform for the need of photonic integrated circuits (PIC). A TEML has been fabricated by this technique for the first time. The component has superior characteristics as following: threshold current of 37mA, output power of 3.5mW at 100mA injection and 0V modulator bias voltage, extinction ratio of more than 20 dB with modulator reverse voltage from 0V to 2V when coupled into a single mode fiber, and wavelength tuning range of 4.4nm covering 6 100-GHz WDM channels. A clearly open eye diagram is observed when the integrated EAM is driven with a 10-Gb/s electrical NRZ signal. A good transmission characteristic is exhibited with power penalties less than 2.2 dB at a bit error ratio (BER) of 10(-10) after 44.4 km standard fiber transmission.

Fabrication of a novel silica PLC hybrid integrated triplexer

A new-style silica planar lightwave circuit (PLC) hybrid integrated triplexer, which can demultiplex 1490-nm download data and 1550-nm download analog signals, as well as transmit 1310-nm upload data, is presented. It combines SiO2 arrayed waveguide gratings (AWGs) with integrated photodetectors (PDs) and a high performance laser diode (LD). The SiO2 AWGs realize the three-wavelength coarse wavelength-division multiplexing (CWDM). The crosstalk is less than 40 dB between the 1490- and 1550-nm channels, and less than 45 dB between 1310- and 1490- or 1550-nm channels. For the static performances of the integrated triplexer, its upload output power is 0.4 mW, and the download output photo-generated current is 76 A. In the small-signal measurement, the upstream 3-dB bandwidth of the triplexer is 4 GHz, while the downstream 3-dB bandwidths of both the analog and digital sections reach 1.9 GHz.

Fast and effective analysis methods for fiber Raman amplifiers

A series of new single-step methods and their corresponding algorithms with automatic step size adjustment for model equations of fiber Raman amplifiers are proposed and compared in this paper. On the basis of the Newton-Raphson method, multiple shooting algorithms for the two-point boundary value problems involved in solving Raman amplifier propagation equations are constructed. A verified example shows that, compared with the traditional Runge-Kutta methods, the proposed methods can increase the accuracy by more than two orders of magnitude under the same conditions. The simulations for Raman amplifier propagation equations demonstrate that our methods can increase the computing speed by more than 5 times, extend the step size significantly, and improve the stability in comparison with the Dormand-Prince method. The numerical results show that the combination of the multiple shooting algorithms and the proposed methods has the capacity to rapidly and effectively solve the model equations of multipump Raman amplifiers under various conditions such as co-, counter- and bi-directionally pumped schemes, as well as dual-order pumped schemes.

Influence of a tilted cavity on quantum-dot optoelectronic active devices

Quantum-dot laser diodes (QD-LDs) with a Fabry-Perot cavity and quantum-dot semiconductor optical amplifiers (QD-SOAs) with 7° tilted cavity were fabricated. The influence of a tilted cavity on optoelectronic active devices was also investigated. For the QD-LD, high performance was observed at room temperature. The threshold current was below 30 mA and the slope efficiency was 0.36 W/A. In contrast, the threshold current of the QD-SOA approached 1000 mA, which indicated that low facet reflectivity was obtained due to the tilted cavity design.A much more inverted carrier population was found in the QD-SOA active region at high operating current, thus offering a large optical gain and preserving the advantages of quantum dots in optical amplification and processing applications. Due to the inhomogeneity and excited state transition of quantum dots, the full width at half maximum of the electroluminescence spectrum of the QD-SOA was 81.6 nm at the injection current of 120 mA, which was ideal for broad bandwidth application in a wavelength division multiplexing system. In addition, there was more than one lasing peak in the lasing spectra of both devices and the separation of these peak positions was 6-8 nm,which is approximately equal to the homogeneous broadening of quantum dots.

Wide-Band Polarization-Independent Semiconductor Optical Amplifier Gate with Tensile-Strained Quasi-Bulk InGaAs

A semiconductor optical amplifier gate based on tensile-strained quasi-bulk InGaAs is developed. At injection current of 80mA,a 3dB optical bandwidth of more than 85nm is achieved due to dominant band-filling effect.Moreover, the most important is that very low polarization dependence of gain (＜0. 7dB),fiber-to-fiber lossless operation current (70～90mA) and a high extinction ratio (＞50dB) are simultaneously obtained over this wide 3dB optical bandwidth (1520～1609nm) which nearly covers the spectral region of the whole C band (1525～1565nm)and the whole L band (1570～ 1610nm). The gating time is also improved by decreasing carrier lifetime. The wideband polarization-insensitive SOA-gate is promising for use in future dense wavelength division multiplexing (DWDM) communication systems.

1.3μm Si-Based MOEMS Optical Tunable Filter with a Tuning Range of 90nm

Optical filters capable of single control parameter-based wide tuning are implemented and studied. A prototype surface micromachined 1.3μm Si-based MOEMS (micro-opto-electro-mechanical-systems) tunable filter exhibits a continuous and large tuning range of 90 nm at 50 V tuning voltage. The filter can be integrated with Si-based photodetector in a low-cost component for coarse wavelength division multiplexing systems operating in the 1.3μm band.

Tolerance analysis for incident angle of volume phase holographic grating used in optical channel performance monitor

Transmission Volume Phase Holographic Grating (VPHG) is adopted as spectral element in the real-time Optical Channel Performance Monitor (OCPM), which is in dire need in the Dense Wavelength -division-multiplexing(DATDM) system. And the tolerance of incident angle, which can be fully determined by two angles: 6 and (p, is finally inferred in this paper. Commonly, the default setting is that the incident plane is perpendicular to the fringes when the incident angle is mentioned. Now the situation out of the vertical is discussed. By combining the theoretic analysis of VPHG with its use in OCPM and changing 6 and (0 precisely in the computation and experiment, the two physical quantities which can fully specify the performance of VPHG the diffraction efficiency and the resolution, are analyzed. The results show that the diffraction efficiency varies greatly with the change of 6 or (p. But from the view of the whole C-band, only the peak diffraction efficiency drifts to another wavelength. As for the resolution, it deteriorates more rapidly than diffraction efficiency with the change of (p, while more slowly with the change of theta. Only if \phi\less than or equal to+/-1degrees and alpha(B) -0.5 less than or equal to theta less than or equal to alpha(B) + 0.5, the performance of the VPHG would be good enough to be used in OCPM system.

高性能硅基锗光电探测器的研制

在信息产业、生物医学等科技领域越来越受关注的今天，新型光电子、光通信科技必将以更快的速度发展。Si基光电子集成采用成熟价廉的微电子加工工艺，将光学器件与多种功能的微电子电路集成，是实现光通信普及发展和光互连的有效途径。Si基光电探测器是Si基光通信系统的关键器件之一。随着近年来Si基Ge材料外延技术的突破性进展，Si基Ge光电探测器因为兼顾了Si基光电子集成和对光通讯波段(1.31和1.55μm)的高效探测，成为了当今研究的一大热点。
    半导体光电探测器的性能与其结构密切相关。PIN型光电探测器是最常见的探测器，可以普遍应用于光通讯光互连系统；雪崩光电二极管(APD)因为具有较高的响应度和内部增益，在实现单光子探测方面具备很大的优越性，适用于当今迅猛发展的生物光子学和量子信息学；共振腔增强型的光电探测器(RCE-PD)，集波长选择器、高速光信号接收器于一体，而且具备共振增强作用、高饱和功率输出等特点，是局域网、光纤入户和现代波分复用(Wavelength-Division Multiplexing,WDM)系统光通信网络的一种优选方案；波导结构探测器(Waveguide-PD)可以解除探测器的响应带宽和量子效率之间的矛盾，而且其结构特点更易于实现与调制器等光波导器件的集成，是片上光互连的首选探测器。
    本论文围绕高性能Si基Ge光电探测器这一研究目标，开展了多种结构的光电探测器的研制，包括PIN型PD的研制及其优化、吸收区与倍增区分离结构(SACM)的Ge-on-Si APD、RCE-PD和Waveguide-PD，主要研究结果如下：

1.                成功研制了PIN型Ge-on-Si光电探测器，器件在-1V外加偏压下暗电流密度为46.6mA/cm2，在1.31μm和1.55μm波长下器件的量子效率分别为40%和17%；然后改进了实验方法，在制作器件之前将Ge-on-Si材料在850℃条件下快速退火1分钟，从而改善材料质量，器件的暗电流密度降低至4mA/cm2，这是目前国际上报道的最好结果之一。

2.                研制出了PIN型Ge-on-SOI光电探测器，在1.31μm和1.55μm波长的量子效率分别为62%和25%。在-3V外加偏压下，器件的3dB带宽为12.6GHz。25μm直径器件，3dB带宽更是达到了13.4GHz。同时，制作了均匀性很好的1×4探测器阵列，单个器件的3dB带宽达13.3GHz。

3.                在国际上首次研究了硅基锗光电探测器的高饱和特性。在-1V和-2V外加偏压下，探测器的1-dB小信号压缩电流分别为22mA和40mA,相应的光功率分别为67.5mW和110.5mW。

4.                成功研制了吸收区和倍增区分离的Si基Ge雪崩光电二极管，器件的穿通电压Vpt约为29V，击穿电压Vbd(暗电流等于100μA时的电压)为39.5V。在击穿电压附近，如39V时，SACM-Ge-on-Si APD的增益为40。

5.                解决了背面ICP深刻蚀工艺难题，成功制备了中心波长在1.55μm，量子效应高达62%的共振腔增强型Si基Ge光电探测器。

小波域地震资料的处理方法（WSSP）研究

The modeling formula based on seismic wavelet can well simulate zero - phase wavelet and hybrid-phase wavelet, and approximate maximal - phase and minimal - phase wavelet in a certain sense. The modeling wavelet can be used as wavelet function after suitable modification item added to meet some conditions. On the basis of the modified Morlet wavelet, the derivative wavelet function has been derived. As a basic wavelet, it can be sued for high resolution frequency - division processing and instantaneous feature extraction, in acoordance with the signal expanding characters in time and scale domains by each wavelet structured. Finally, an application example proves the effectiveness and reasonability of the method. Based on the analysis of SVD (Singular Value Decomposition) filter, by taking wavelet as basic wavelet and combining SVD filter and wavelet transform, a new de - noising method, which is Based on multi - dimension and multi-space de - noising method, is proposed. The implementation of this method is discussed the detail. Theoretical analysis and modeling show that the method has strong capacity of de - noising and keeping attributes of effective wave. It is a good tool for de - noising when the S/N ratio is poor. To give prominence to high frequency information of reflection event of important layer and to take account of other frequency information under processing seismic data, it is difficult for deconvolution filter to realize this goal. A filter from Fourier Transform has some problems for realizing the goal. In this paper, a new method is put forward, that is a method of processing seismic data in frequency division from wavelet transform and reconstruction. In ordinary seismic processing methods for resolution improvement, deconvolution operator has poor part characteristics, thus influencing the operator frequency. In wavelet transform, wavelet function has very good part characteristics. Frequency - division data processing in wavelet transform also brings quite good high resolution data, but it needs more time than deconvolution method does. On the basis of frequency - division processing method in wavelet domain, a new technique is put forward, which involves 1) designing filter operators equivalent to deconvolution operator in time and frequency domains in wavelet transform, 2) obtaining derivative wavelet function that is suitable to high - resolution seismic data processing, and 3) processing high resolution seismic data by deconvolution method in time domain. In the method of producing some instantaneous characteristic signals by using Hilbert transform, Hilbert transform is very sensitive to high - frequency random noise. As a result, even though there exist weak high - frequency noises in seismic signals, the obtained instantaneous characteristics of seismic signals may be still submerged by the noises. One method for having instantaneous characteristics of seismic signals in wavelet domain is put forward, which obtains directly the instantaneous characteristics of seismic signals by taking the characteristics of both the real part (real signals, namely seismic signals) and the imaginary part (the Hilbert transfom of real signals) of wavelet transform. The method has the functions of frequency division and noise removal. What is more, the weak wave whose frequency is lower than that of high - frequency random noise is retained in the obtained instantaneous characteristics of seismic signals, and the weak wave may be seen in instantaneous characteristic sections (such as instantaneous frequency, instantaneous phase and instantaneous amplitude). Impedance inversion is one of tools in the description of oil reservoir. one of methods in impedance inversion is Generalized Linear Inversion. This method has higher precision of inversion. But, this method is sensitive to noise of seismic data, so that error results are got. The description of oil reservoir in researching important geological layer, in order to give prominence to geological characteristics of the important layer, not only high frequency impedance to research thin sand layer, but other frequency impedance are needed. It is difficult for some impedance inversion method to realize the goal. Wavelet transform is very good in denoising and processing in frequency division. Therefore, in the paper, a method of impedance inversion is put forward based on wavelet transform, that is impedance inversion in frequency division from wavelet transform and reconstruction. in this paper, based on wavelet transform, methods of time - frequency analysis is given. Fanally, methods above are in application on real oil field - Sansan oil field.

利用分频与反演提高地震资料信噪比与分辨率方法研究

This thesis mainly talks about the wavelet transfrom and the frequency division method. It describes the frequency division processing on prestack or post-stack seismic data and application of inversion noise attenuation, frequency division residual static correction and high resolution data in reservoir inversion. This thesis not only describes the frequency division and inversion in theory, but also proves it by model calculation. All the methods are integrated together. The actual data processing demonstrates the applying results. This thesis analyzes the differences and limitation between t-x prediction filter and f-x prediction filter noise attenuation from wavelet transform theory. It considers that we can do the frequency division attenuation process of noise and signal by wavelet frequency division theory according to the differences of noise and signal in phase, amplitude and frequency. By comparison with the f-x coherence noise, removal method, it approves the effects and practicability of frequency division in coherence and random noise isolation. In order to solve the side effects in non-noise area, we: take the area constraint method and only apply the frequency division processing in the noise area. So it can solve the problem of low frequency loss in non-noise area. The residual moveout differences in seismic data processing have a great effect on stack image and resolutions. Different frequency components have different residual moveout differences. The frequency division residual static correction realizes the frequency division and the calculation of residual correction magnitude. It also solves the problems of different residual correction magnitude in different frequency and protects the high frequency information in data. By actual data processing, we can get good results in phase residual moveout differences elimination of pre-stack data, stack image quality and improvement of data resolution. This thesis analyses the characters of the random noises and its descriptions in time domain and frequency domain. Furthermore it gives the inversion prediction solution methods and realizes the frequency division inversion attenuation of the random noise. By the analysis of results of the actual data processing, we show that the noise removed by inversion has its own advantages. By analyzing parameter's about resolution and technology of high resolution data processing, this thesis describes the relations between frequency domain and resolution, parameters about resolution and methods to increase resolution. It also gives the processing flows of the high resolution data; the effect and influence of reservoir inversion caused by high resolution data. Finally it proves the accuracy and precision of the reservoir inversion results. The research results of this thesis reveal that frequency division noise attenuation, frequency residual correction and inversion noise attenuation are effective methods to increase the SNR and resolution of seismic data.

Research and design of high-speed advanced analogue front-ends for fibre-optic transmission systems

In the last decade, we have witnessed the emergence of large, warehouse-scale data centres which have enabled new internet-based software applications such as cloud computing, search engines, social media, e-government etc. Such data centres consist of large collections of servers interconnected using short-reach (reach up to a few hundred meters) optical interconnect. Today, transceivers for these applications achieve up to 100Gb/s by multiplexing 10x 10Gb/s or 4x 25Gb/s channels. In the near future however, data centre operators have expressed a need for optical links which can support 400Gb/s up to 1Tb/s. The crucial challenge is to achieve this in the same footprint (same transceiver module) and with similar power consumption as today’s technology. Straightforward scaling of the currently used space or wavelength division multiplexing may be difficult to achieve: indeed a 1Tb/s transceiver would require integration of 40 VCSELs (vertical cavity surface emitting laser diode, widely used for short‐reach optical interconnect), 40 photodiodes and the electronics operating at 25Gb/s in the same module as today’s 100Gb/s transceiver. Pushing the bit rate on such links beyond today’s commercially available 100Gb/s/fibre will require new generations of VCSELs and their driver and receiver electronics. This work looks into a number of state‐of-the-art technologies and investigates their performance restraints and recommends different set of designs, specifically targeting multilevel modulation formats. Several methods to extend the bandwidth using deep submicron (65nm and 28nm) CMOS technology are explored in this work, while also maintaining a focus upon reducing power consumption and chip area. The techniques used were pre-emphasis in rising and falling edges of the signal and bandwidth extensions by inductive peaking and different local feedback techniques. These techniques have been applied to a transmitter and receiver developed for advanced modulation formats such as PAM-4 (4 level pulse amplitude modulation). Such modulation format can increase the throughput per individual channel, which helps to overcome the challenges mentioned above to realize 400Gb/s to 1Tb/s transceivers.

High speed optical communication systems: From modulation formats to radically new fibres

High volumes of data traffic along with bandwidth hungry applications, such as cloud computing and video on demand, is driving the core optical communication links closer and closer to their maximum capacity. The research community has clearly identifying the coming approach of the nonlinear Shannon limit for standard single mode fibre [1,2]. It is in this context that the work on modulation formats, contained in Chapter 3 of this thesis, was undertaken. The work investigates the proposed energy-efficient four-dimensional modulation formats. The work begins by studying a new visualisation technique for four dimensional modulation formats, akin to constellation diagrams. The work then carries out one of the first implementations of one such modulation format, polarisation-switched quadrature phase-shift keying (PS-QPSK). This thesis also studies two potential next-generation fibres, few-mode and hollow-core photonic band-gap fibre. Chapter 4 studies ways to experimentally quantify the nonlinearities in few-mode fibre and assess the potential benefits and limitations of such fibres. It carries out detailed experiments to measure the effects of stimulated Brillouin scattering, self-phase modulation and four-wave mixing and compares the results to numerical models, along with capacity limit calculations. Chapter 5 investigates hollow-core photonic band-gap fibre, where such fibres are predicted to have a low-loss minima at a wavelength of 2μm. To benefit from this potential low loss window requires the development of telecoms grade subsystems and components. The chapter will outline some of the development and characterisation of these components. The world's first wavelength division multiplexed (WDM) subsystem directly implemented at 2μm is presented along with WDM transmission over hollow-core photonic band-gap fibre at 2μm. References: [1]P. P. Mitra, J. B. Stark, Nature, 411, 1027-1030, 2001 [2] A. D. Ellis et al., JLT, 28, 423-433, 2010.

Analysis of Receiver Algorithms for LTE SC-FDMA Based Uplink MIMO Systems

This letter derives mathematical expressions for the received signal-to-interference-plus-noise ratio (SINR) of uplink Single Carrier (SC) Frequency Division Multiple Access (FDMA) multiuser MIMO systems. An improved frequency domain receiver algorithm is derived for the studied systems, and is shown to be significantly superior to the conventional linear MMSE based receiver in terms of SINR and bit error rate (BER) performance.