E O Optical Enectronical Optical Biến đổi quang điện quang

OPTICAL NETWORKS A PRACTICAL PERSPECTIVE PART 46 PPT

Figure 7.12 shows a wavelength plane OXC. The signals coming in over different fiber pairs are first demultiplexed by the OLTs. All the signals at a given wavelength are sent to a switch dedicated to that wavelength, and the signals from the outputs of the switches are multiplexed back together by the OLTs. In a node with F W D M fiber pairs and W wavelengths on each fiber pair, this arrangement uses F OLTs and W 2F x 2F switches. This allows any or all signals on any input wavelength to be dropped locally. In contrast, the configuration of Figure 7.11 uses F OLTs and a 2 W F x 2 W F switch to provide the same capabilities. Consider, for example, F = 4, W = 32, which are realistic numbers today. In this case, the configuration of Figure 7.12 uses four OLTs and 32 8 x 8 switches. In contrast, Figure 7.9(b) requires four OLTs and a 256 x 256 switch. As we saw in Section 3.7, larger optical switches are significantly harder to build than small ones and will need to use technologies like analog beam-steering micromirrors, whereas small optical switches can be realized using a variety of different technologies.

CÁC PHÂN TỬ TRUYỀN ĐỘNG VÀ ĐIỀU KHIỂN KHÍ NÉN

V ớ i c ả m bi ế n ti ệ m c ậ n có các lo ạ i sau: c ả m bi ế n ti ệ m c ậ n c ả m ứ ng t ừ , c ả m bi ế n ti ệ m c ậ n đ i ệ n dung và c ả m bi ế n ti ệ m c ậ n quang. + C ả m bi ế n ti ệ m c ậ n c ả m ứ ng t ừ (Inductive proximity sensor): trên hình 1.62 là nguyên lý ho ạ t độ ng, s ơ đồ nguyên lý và ký hi ệ u c ủ a c ả m bi ế n ti ệ m c ậ n c ả m ứ ng t ừ .

BÁO CÁO HÓA HỌC MONITORING CHARGE EXCHANGE IN P3HT NANOTUBE COMPOSITES USING OPTICAL AND ELECTRICAL CHARACTERISATION DOCX

In summary, we have presented a combination of elec- trical and optical methods for studying the charge exchange at bulk P3HT–SWNT heterojunctions. The optical methods show that at high SWNT concentrations the structure of the polymer is altered as the polymer chains movement is restricted. The change in structure is obvious from the optical absorption spectra. Ultrafast transient absorption measurements have been used here to monitor the popu- lation of states at the bottom of P3HT’s LUMO with a temporal resolution of 150 fs. The existence of SWNTs in the composite accelerated exciton dissociation up to SWNT concentrations of 65 wt%. However, the optical methodologies explored could not provide detailed infor- mation for very low SWNT loadings near the percolation threshold (0.75 wt%). However, this is an extremely interesting range of SWNT concentrations because, elec- trically, the composites change from semiconducting to almost metallic very rapidly for SWNTs concentrations above the percolation threshold. Here we show that low frequency C–V characterization is a methodology which can be used to complement optical characterization and detect charge exchange at P3HT–SWNT heterojunctions. The signature of this interaction is the value of the accu- mulation capacitance being higher than C ox at low frequencies. In analogy to MOS devices with leaky dielectrics, the higher than C ox value of accumulation capacitance is a measure of the charges trapped by the SWNTs at bulk junctions near the interface.

Micromechanical Photonics - H. Ukita Part 1 ppt

1.1 Micromechanical Photonics – An Emerging Technology We have made substantial progress in individual areas of optics, mechan- ics, electronics and physical/chemical sciences, but it is insuﬃcient to apply individual technologies and sciences to solve today’s complicated technical problems. The start of semiconductor LD room temperature continuous oscil- lation in 1970 and micromachiningtechnology [1.1, 1.2] based on photolitho- graphy and selective etching in the late 1980s resulted in the birth of optical MEMS [1.3]/micromechanical photonics [1.4] that combines/integrates electri- cal, mechanical, thermal, and sometimes chemical components through optics in the early 1990s.

Nanostructured zinc aluminates: A promising material for cool roof coating

Zhang, Optical properties across the solar spectrum and indoor ther- mal performance of cool white coatings for building energy efﬁciency, Energ. Akbari, Solar spectral optical propertie[r]

TTQUANG... PPSX

2.2 Kiến trúc chuyển mạch gói quang Hình 15. Kiến trúc một chuyển mạch gói quang Một hệ thống OPS điển hình sử dụng một trường điều khiển điện và trường dữ liệu toàn quang để tìm kiếm nội dung của header, thực hiện các quyết định chuyển đổi và chuyển đổi các khung chuyển mạch toàn quang để chuyển đi dữ liệu quang.

Synthesis of branched conjugated copolymers based on triphenylamine and 3-hexylthiophene units

The optical and the nanostructures of the obtained hyperbranched con- jugated polymers were characterized, and the effect of polymer aggregation on the optical properties was[r]

ÔN TẬP VẬT LÍ 12 PHẦN LƯỢNG TỬ ÁNH SÁNG PPTX

Bài19 :Chiếu một chùm ánh sáng đơn sắc vào K của TBQĐ.Để triệt tiêu dòng quang điện thì hiệu điện thế hãm có giá trị là 1,9V.Vận tốc ban đầu cực đại của quang (e) là bào nhiêu? A. 5,2.10 5 m/s B. 6,2.10 5 m/s C. 7,2.10 5 m/s D. 8,2.10 5 m/s Bài20 : Chiếu một chùm ánh sáng đơn sắc có bước sóng 400nm vào K của TBQĐ làm bằng Na.Giới hạn quang điện của Na là 0,5m.Vận tốc ban đầu cực đại của (e) quang điện là:

THE COMPLETE IS-IS ROUTING PROTOCOL- P18 PPTX

layer that is necessary for provisioning ﬁxed pipes for the ATM trunks. Finally the SONET/SDH frame needs DWDM and Optical Cross Connect (OCX) technologies to get transported over the ﬁbre. Compare this relatively massive layering to today’s networking layers. ATM got elim- inated due to the rise of MPLS. SONET/SDH is no longer used for provisioning circuits. The only remnants of SONET/SDH technology is the frame format. Today, IP is trans- ported almost natively over a DWDM infrastructure. There has been a massive consolida- tion of transport technologies. The rise of IP technology set a trend here: either a networking layer gets eliminated or its functions are ported into an IP routing or signalling protocol. MPLS is a good example here: a lot of ATM functions, such as the idea of source rout- ing, CSPF and label swapping, made their way into a set of IP protocols. If you continue that trend, then IP will again likely control the next layer of networking beneath. This is the optical layer.

HEAT TRANSFER THEORETICAL ANALYSIS EXPERIMENTAL INVESTIGATIONS AND INDUSTRIAL SYSTEMS PART 10 POTX

2.2 Visualization of temperature fields: infinite and finite fringe field arrangements HI allows the visualization and analysis of high-speed, transient phenomena by using the real-time method, which is a single exposure technique. The visualization is carried out in two steps. First, the reference state (usually with the fluid in the measurement volume at ambient temperature) is recorded on the holographic plate. Next, the holographic plate is developed, bleached, dried and exactly repositioned into a precision plate holder. In the second step, the reference state of the object under investigation is reconstructed by illuminating the holographic plate with the reference beam. At the same time, the investigated physical process is initiated (in our experiment the blocks in the wind tunnel are heated or the thermoacoustic refrigerator is activated). The heating causes the refractive index of the fluid in the measurement volume to change, and, consequently, this causes the object wave to experience a phase shift on its way through the test section. The difference between the reference state recorded earlier and the new state of the fluid in the measurement volume, i.e. the phase shift between reference and measurement beams, is visualized in the form of a macroscopic interference fringe pattern. This fringe pattern can be recorded with a photographic camera or a high-speed camera (when the process is unsteady).

BÁO CÁO VẬT LÝ EFFECTS OF SI AL2O3 AND SIC SUBSTRATES ON THE CHARACTERISTICS OF DBRS STRUCTURE FOR GAN BASED LASER PPSX

thickness λ /4n 2 Figure 1: Diagram of DBR two alternating materials of optical thickness ( λ /4) are used to form a DBR From Fresnel's equations [8] due to matching of the tangential electric fields for a propagating electromagnetic wave at normal incidence, the reflectivity from a single optical interface is given by

EXPERIMENT INVESTIGATION OF PAPR REDUCTION SCHEMES IN THE INTENSITY MODULATION DIRECT DETECTION OPTICAL OFDM SYSTEM

48 TRANG 18 TRANG 19 _Experiment investigation of PAPR reduction schemes in the IM/DD Optical OFDM system _ 1 CHAPTER 1: INTRODUCTION 1.1 OPTICAL OFDM Orthogonal frequency division multi[r]

Solar Collectors and Panels, Theory and Applications_1 ppsx

2.2.2 Luminescent concentrators The aforementioned solutions and methods to concentrate the light are not the only developed for photovoltaic applications. One important limitation of these designs is the necessity to use tracking structure to follow the sun. This constrain must not be considered always a limitation; indeed, especially for utility scale installations, tracking structure are used for standard flat plate modules too, in order to improve the energy harvesting, being always on the plane perpendicular to the sunrays. However, the possibility to use static photovoltaic concentrator able to capture also the diffuse radiation has been developed, using a different optical approach, not just the geometrical optics, but involving also some physical properties of particular material like the luminescence; these concentrators, named luminescent concentrators, are usually made of a flat plate of transparent material, with solar cells connected to the sides of the plate; inside the transparent material, luminescent particles like organic dyes or quantum dots are dispersed, absorbing part of the light spectrum and re-emitting light with shifted wavelengths, matching the spectral response of the cells. The re-emitted light is than guided toward the solar cells through the transparent mean, using the total internal reflection at the surface. The limiting point of this technology is the low efficiency achieved due to the losses in the different physical processes involved; it is currently in the order of 6-7% for record prototypes; moreover, the usual concentration for this kind of modules is in the order of 10-40 and the overall size of each luminescent concentrator, to avoid significant losses for light absorption from the transparent material, must be limited.

COMPOSITE 2012 PART 7 PPTX

In this book chapter, we introduce a polarizer-free LCD using dye-doped LC gels whose the physical mechanism is mainly the combination of both light scattering and absorption. In the beginning, we introduce the structure and mechanism of our dye-doped liquid crystal gels. Second, the experimental setups, results (morphologies, electro-optical properties, response time) and mathematical model are also discussed. Third, the performance of such a polarizer-free liquid crystal display is shown. Finally, we will introduce multiple step switches using distinct dye-doped LC gels for the application of decorative displays. The potential applications are flexible displays, electrically tunable light shutters, and decorative displays.

OPTOELECTRONICS DEVICES AND APPLICATIONS PART 8 POT

4. Conclusion Summarizing, we note that the optical properties of the In 0.18 Ga 0.82 As/GaAs differently shaped near-surface quantum wells under intense laser fields could be tuned by proper tailoring of the heterostructure parameters (well shape and width, cap layer thickness, barrier asymmetry) and/or by varying the laser field intensity. This characteristics holds for both intersubband and interband absorptions. For example, in the exciton spectra of narrow In 0.18 Ga 0.82 As/GaAs n-sQWs, our calculations show that the red-shift of the absorption peaks induced by the rising cap layer thickness or by barrier asymmetry diminution can be effectively compensated using the blue-shift caused by enhancing laser parameter. These phenomena could be exploited for particular applications. Also, for both intersubband and interband transitions, the switch between the strong absorption and induced laser transparency regimes can be suitable for good performance optical modulators.

IP OVER WDM NETWORK POTX

 REQUIRES INTELLIGENCE IN THE OPTICAL LAYER  NEED TO STORE PACKET DURING HEADER PROCESSING  OPTICAL BUFFERS ARE EXTREMELY HARD TO IMPLEMENT  1 pkt = 12 kbits @ 10 Gbps requires 1.2 µ[r]

IP OVER WDM NETWORK DOCX

 REQUIRES INTELLIGENCE IN THE OPTICAL LAYER  NEED TO STORE PACKET DURING HEADER PROCESSING  OPTICAL BUFFERS ARE EXTREMELY HARD TO IMPLEMENT  1 pkt = 12 kbits @ 10 Gbps requires 1.2 µ[r]

Advanced Microwave and Millimeter Wave technologies devices circuits and systems Part 2 pot

L GD is typically set to 1 μ m in Fig.1(a) and 1.5 μ m in Fig.1(b). Note that in Fig.1(b), the gate electrode extends on to SiN passivation layer. This is called field plate. The field-plate length L FP is typically set to 1 μ m. The thickness of SiN layer d is varied as a parameter between 0 and 0.1 μ m. Polarization charges of 10 13 cm -2 are set at the heterojunction interface, and the surface polarization charges are assumed to be compensated by surface-state charges, as in (Karmalkar & Mishra, 2001). As a model for the buffer layer, we use a three level compensation model which includes a shallow donor, a deep donor and a deep acceptor (Horio et al., 2005). Some representative experiments show that two levels ( E C – 1.8 eV, E C – 2.85 eV) are associated with current collapse in GaN-based FETs with a semi-insulating buffer layer (Klein et al., 1999; Binari et al., 2002). Therefore, we use an energy level of E C – 2.85 eV ( E V + 0.6 eV) for the deep acceptor, and for convergence problem, we use E C – 1.7 eV for the deep donor. (Note that the origin of these deep levels is not well known and our treatment is only an assumption.) Other experiments show shallower energy levels for deep

PHÂN TÍCH MÔ HÌNH NÚT SPIL VỚI KHẢ NĂNG CHUYỂN ĐỔI BƯỚC SÓNG GIỚI HẠN TRÊN MẠNG CHUYỂN MẠCH CHÙM QUANG

Chuyển mạch chùm quang OBS (Optical Burst Switching) trên mạng WDM (Wavelenght Division Multiplexing) đã được xem như là một công nghệ đầy triển vọng đối với mạng Internet thế hệ tiếp theo, bởi vì nó có nhiều lợi thế hấp dẫn như tốc độ nhanh và hiệu suất khai thác băng thông cao hơn nhiều so với những mô hình chuyển mạch kênh quang khác.

BÁO CÁO HÓA HỌC BIOLOGICAL SYNTHESIS OF SIZE CONTROLLED CADMIUM SULFIDE NANOPARTICLES USING IMMOBILIZED RHODOBACTER SPHAEROIDES PPT

culture medium in the absence or in the presence of 1 mM Cd 2 ? (circled in red, Fig. 3 a, d). The strong signals in Fig. 5 b indicate the presence of Cd and S, and the ratio of Cd:S is 0.97:1.00. The result shows that the deposit of CdS has been synthesized in cells. However, there are not the signals of Cd and S in Fig. 5 a. The presence of C and O in Fig. 5 suggests the biomolecules in the R. sphaeroides cells.

Nonlinear optical tweezers as an optical method for controlling particles with high trap efficiency

Optical tweezers have been seen as an essential tool for manipulating dielectric microparticles and nanoparticles thanks to its non-contact action and high resolution of optical force. Up to now, there has been a lot of optical tweezers applications in the fields of biophysics, chemistry, medical science and nanoscience. Recently, optical tweezers have been theoretically and experimentally developed for the nano mechanical characterization of various kinds of biological cells.

The dependence of the parametric transformation coefficient of acoustic and optical phonons in doped superlattices on concentration of impurities

Especially, when concentration o f impurities tend toward zero, value o f the parametric transformation coefficient o f acoustic and optical phonons in doped superlattices [r]

Tóm tắt Lý thuyết và Công thức giải nhanh vật lý 12

+ Ứng dụng của các hiện tượng quang điện trong các tế bào quang điện, trong các dụng cụ để biến đổi các tín hiệu ánh sáng thành tín hiệu điện, trong các quang điện trở, pin quang điện..[r]

BÁO CÁO VẬT LÝ: "MODELLING AND SIMULATION STUDY OF VISIBLE EMISSION TRANSMISSIVITY OF SILICON RELATED TO SINGLE AND MULTILAYER ANTIREFLECTION COATINGS" POTX

= ⎜ ⎝ + ⎠ ⎟ (1) In our optical model for increasing the transmissivity of visible emission of Si related to Figure 2, the contribution of the single and multilayer antireflection coatings are calculated using the transfer matrix method at the central wavelength 720 nm (where incident angle of emitted light at Si/air interface is θ = 0). In the calculation, we use theoretically determined optical

HỆ THỐNG THÔNG TIN QUANG TỚI HỘ GIA ÐÌNH (FTTH)

CHƯƠNG 2. KIẾN TRÚC MẠNG QUANG FTTH 2.1 Sơ đồ tổng quát kiến trúc mạng FTTH Hình 3. Sơ đồ tổng quát mạng quang FTTH (Nguồn: Internet) Trong hệ thống FTTH, thiết bị kết cuối đường truyền quang là OLT (Optical Line Terminal) đặt tại tổng đài trung tâm CO (Center Office) được thiết kế để giao tiếp với các nhà cung cấp dịch vụ (ví dụ: giao tiếp với mạng chuyển mạch điện thoại công cộng, với chuyển mạch ATM, router IP, giao tiếp với mạng lõi video qua thiết bị đầu cuối cáp TV hoặc từ một vệ tinh chảo). Về mặt truyền dẫn, OLT cho phép hỗ trợ các loại giao diện khác nhau của lớp liên kết dữ liệu như: SPNET, ATM, Gigabit Ethernet,…

OPTICAL NETWORKS: A PRACTICAL PERSPECTIVE - PART 27 PPSX

Modulation and Demodulation O UR G O A L IN T H I S C H A P T E R is to understand the processes of modulation and demodulation of digital signals. We start by discussing modulation, which is the process of converting digital data in electronic form to an optical signal that can be transmitted over the fiber. We then study the demodulation process, which is the process of converting the optical signal back into electronic form and extracting the data that was transmitted.

MÔ HÌNH FTTH TRÊN NỀN CÔNG NGHỆ GPON

Hình 1.1: Cấu trúc AON Một nhƣợc điểm rất lớn của mạng quang chủ động chính là ở thiết bị chuyển mạch. Với công nghệ hiện tại, thiết bị chuyển mạch bắt buộc phải chuyển tín hiệu quang thành tín hiệu điện để phân tích thông tin rồi tiếp tục chuyển ngƣợc lại để truyền đi, điều này sẽ làm giảm tốc độ truyền dẫn tối đa có thể trong hệ thống FTTX. Ngoài ra do đây là những chuyển mạch có tốc độ cao nên các thiết bị này có chi phí đầu tƣ lớn, không phù hợp với việc triển khai đại trà cho mạng truy cập.

B04 THONG TIN QUANG KTTD KTVT 2009 PTITBMM

TRANG 1 BÀI SỐ4: KỸTHUẬT THỤNG TIN QUANG BÀI GIẢNG CHO ĐH PTIT THS.. KEISER, OPTICAL FIBER COMMUNICATIONS, 2001.[r]

OPTICAL NETWORKS: A PRACTICAL PERSPECTIVE - PART 5 POTX

14 INTRODUCTION TO OPTICAL NETWORKS 1.3.2 the context of optical communication, perhaps because FDM was studied first by communications engineers and WDM by physicists. The idea is to transmit data si- multaneously at multiple carrier wavelengths (or, equivalently, frequencies or colors) over a fiber. To first order, these wavelengths do not interfere with each other pro- vided they are kept sufficiently far apart. (There are some undesirable second-order effects where wavelengths do interfere with each other, and we will study these in Chapters 2 and 5.) Thus WDM provides virtual fibers, in that it makes a single fiber look like multiple "virtual" fibers, with each virtual fiber carrying a single data stream. WDM systems are widely deployed today in long-haul and undersea networks and are being deployed in metro networks as well.

ADVANCES IN CHEMICAL SENSORS pdf

95 N Fig. 12. Structures of coumarin-derived chemosensors for detection of thiols Generally detection of thiols by optical probes is based on two features of thiols, their strong nucleophilicity and high binding affinity toward metal ions. Accordingly, most of the fluorescent probes for thiols are in fact chemodosimeters, which involve specific reactions between probes and thiols, such as Michael addition, cyclization with aldehyde (or ketone), cleavage of disulfide by thiols, metal complexes-displace coordination, demetalization from Cu-complex, thiolysis of dinitrophenyl ether, and Staudinger ligation. For instance, detection of thiols by chemosensors 87 - 91 and 93 involves Michael addition between the probes and thiols. For sensors 67 (Fig. 8), 86 and 98 , cyclization reactions occur between the sensors and thiols in the detection process. Coumarin 86 is a ratiometric fluorescent probe for specific detection of Cys over Hcy and GSH based on the drstic distinction in the kinetic profiles (Yuan et al., 2011). Nonfluorescent coumarin-malonitrile conjugate 87 can be transformed into a strongly fluorescent molecule through the Michael addition and thus exhibits a highly selective fluorescence response toward biothiols including Cys, Hcy and GSH with micromolar sensitivity (Kwon et al., 2011). Similarly, nonfluorescent 88 displays a highly selective fluorescence enhancement with thiols and has been successfully applied to thiols determination in intracellular, in human urine and blood samples (Zuo et al., 2010). Coumarin 89 has been developed as a water-soluble, fast-response, highly sensitive and selective fluorescence thiol quantification probe (Yi et al., 2009). Compound 90 (G.-J. Kim et al., 2011) and 91 (S. Y. Lim et al., 2011) with a hydrogen bond act as highly selective ratiometric fluorescence turn-on probes for GSH. Structure 92 has been judiciously designed and synthesized as a new type of selective benzenethiol fluorescent probe based on the thiolysis of dinitrophenyl ether (Lin et al., 2010a). Coumarin-based chemodosimeter 93

ADVANCES IN OPTICAL AMPLIFIERS PART 4 POTX

2. Cross gain and cross phase modulation based convertors When biased above their transparency current, SOAs may deliver considerable optical gain with a typical operational bandwidth of several tens of nanometers. However, since the gain mechanism is based on injection of carriers, the introduction of modulated optical carriers, and especially of short high peak power pulses such as those used for Opitcal Time Domain Multiplexing systems (OTDM), result in severe modulation of gain bearing majority carriers leading to undesirable cross talk in case multiple channels are introduced into the SOA (Inoue, 1989). The gain of an SOA recovers on three different timescales. Ultrafast gain recovery, driven by carrier–carrier scattering takes place at sub-picoseconds timescale (Mark & Mork, 1992). Furthermore, carrier–phonon interactions contribute to the recovery of the amplifier on a timescale of a few picoseconds (Mark & Mork, 1992). Finally, on a tens of picoseconds to nanosecond timescale, there is a contribution driven by electron–hole interactions. This last recovery mechanism dominates the eventual SOA recovery. Careful design of the active layer in the amplifier, injection efficiency and carrier confinement plays a role in the final recovery time which can vary between several hundreds of picoseconds to as low as 25 pico seconds for specially designed Quantum Well structures (CIP white paper , 2008). During the recovery of gain and carriers from the introduction of an optical pulse, the refractive index of the SOA wave guiding layer is also altered, so that not only the gain but also the phase of the CW signals travelling through the device is modulated. These two phenomena, termed Cross Gain Modulation (XGM) and Cross Phase Modulation (XPM), severely limit the use of SOAs for amplification of optical signals in Wavelength Division Multiplexed (WDM) networks. Yet, the coupling of amplitude modulation of one optical channel into the amplitude and phase of other optical carriers travelling in the same SOAs has caught the attention of researchers working on all optical networks as a simple manner of duplicating data from one wavelength to another, a process also known as wavelength conversion.

Tài liệu Nguyên tắc cơ bản của lượng tử ánh sáng P21 pdf

Outlook A large stock of discrete and continuous mathematical operations on arrays of variables and on two-dimensional functions may be implemented optically. Numerous other operations may be realized by serial and parallel combinations and cascades of these operations. The power of optical analog processors lies in the high degree of parallelism and the large size of the interconnection maps. However, analog computing has limited accuracy and dynamic range and is therefore suitable principally for computational tasks that are insensitive to error. A good example is the implementa- tion of neural networks. These are networks with a high degree of global interconnec- tion, involving simple operations of weighted superpositions and thresholding, that are cascaded and connected in a variety of forms. They implement algorithms which have an underlying redundancy, so that the limited accuracy of analog computing is tolera- ble.

KỸ THUẬT THÔNG TIN QUANG 1 PHẦN 7 DOC

Chương 3 Bộ phát quang 3.6.3. B ộ đ i ề u ch ế ngồi S ơ đồ kh ố i c ủ a k ỹ thu ậ t đ i ề u ch ế ngịai đượ c bi ể u di ễ n trên hình 3.40. Theo đ ĩ, đ i ề u ch ế tín hi ệ u quang khơng th ự c hi ệ n bên trong laser mà đượ c th ự c hi ệ n b ở i m ộ t linh ki ệ n quang bên ngịai g ọ i là b ộ đ i ề u ch ế ngịai (external modulator). Ánh sáng do laser phát ra d ướ i d ạ ng sĩng liên t ụ c CW (continuous wave). V ớ i c ấ u trúc nh ư v ậ y, k ỹ thu ậ t đ i ề u ch ế ngịai đ ã kh ắ c ph ụ c đượ c các nh ượ c đ i ể m c ủ a k ỹ thu ậ t đ i ề u ch ế tr ự c ti ế p:

THÔNG TIN QUANG / C_1__ GIỚI THIỆU VỀ THÔNG TIN QUANG POT

Thông tin cáp s ợ i quang T ừ 1995: s ử d ụ ng k ỹ thu ậ t ghép kênh theo b ướ c sóng (WDM), khuy ế ch đạ i quang (Optical Amplifier) để t ă ng dung l ượ ng và c ự ly truy ề n d ẫ n Hi ệ n nay, diode laser có th ể truy ề n t ố c độ 10Gbit/s trên 1 b ướ c sóng => ghép 4 b ướ c sóng = 40Gbit/s

ADVANCED TRENDS IN WIRELESS COMMUNICATIONS PART 10 DOCX

3.1 Optical sources for transmitters In modern optical wireless communications, there are a variety of light sources for use in the transmitter. One of the most used is the semiconductor laser which is also widely used in fiber optic systems. For indoor environment applications, where the safety is imperative, the Light Emitter Diode (LED) is prefered due to its limited optical power. Light emitting diodes are semiconductor structures that emit light. Because of its relatively low power emission, the LED's are typically used in applications over short distances and for low bit rate (up to 155Mbps). Depending on the material that they are constructed, the LED's can operate in different wavelength intervals. When compared to the narrow spectral width of a laser source, LEDs have a much larger spectral width (Full Width at Half Maximun or FWHM). In Table 1 are shown the semiconductor materials and its emission wavelength used in the LED's (Franz et al, 2000).

BÁO CÁO HÓA HỌC RESEARCH ARTICLE NOVEL TECHNIQUES OF SINGLE CARRIER FREQUENCY DOMAIN EQUALIZATION FOR OPTICAL WIRELESS COMMUNICATIONS DOC

8. Conclusion In this paper, we present three new modulation techniques for di ﬀ use optical wireless communications with IM/DD. The first applies asymmetrically clipped optical (ACO) principles to SCFDE which we called ACO-SCFDE. The others, namely, RCO-SCFDE and DQO-SCFDE, use the newly introduced technique of repetition and clipping. It was shown through the use of simulation that these new techniques exhibit lower PAPR and better BER performance in a multipath channel. The spectral e ﬃ ciency of these techniques is almost the same when the symbol block size is su ﬃ ciently large. ACO-SCFDE is a direct application of ACO-OFDM using SCFDE modulation instead of OFDM. The former requires FFT and IFFT at the transmitter and receiver but has lower PAPR than ACO-OFDM and better BER performance. RCO-SCFDE and DQO-SCFDE are other two new methods for generating real positive signal needed for transmission over the optical channel. RCO-SCFDE has the same PAPR as ACO-SCFDE but lower computational complexity. DQO-SCFDE has the lowest PAPR, lower computational complexity, and exhibits better BER performances. For this particular reason, we believe that DQO-SCFDE is the most attractive choice for transmitting real positive signal over an optical channel.

GEOGRAPHY AND OCEANOGRAPHY CHAPTER 19 DOCX

TRANG 3 CTD CTD OPTICAL SENSORS OPTICAL SENSORS CHL, CDOM AND CHL, CDOM AND BACKSCATTER BACKSCATTER PITCH BATTERIES PITCH BATTERIES SCIENCE BAY SCIENCE BAY GLIDER CONTROL AND GLIDER CONT[r]

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