Resumo aula anterior Apresentação do Jhonas sobre Óptica Para Fins Bélicos Conectores, acopladores e adaptadores tanto para comunicações qto tb para outros.

Apresentação em tema: "Resumo aula anterior Apresentação do Jhonas sobre Óptica Para Fins Bélicos Conectores, acopladores e adaptadores tanto para comunicações qto tb para outros."— Transcrição da apresentação:

1 Resumo aula anterior Apresentação do Jhonas sobre Óptica Para Fins Bélicos Conectores, acopladores e adaptadores tanto para comunicações qto tb para outros propósitos. Interruptores ópticos 2x2, 4x4....

2 Outros interruptores Design and Simulation of Planar Electro-optic Switches in Ferroelectrics M. Krishnamurthi, L. Tian and V. Gopalan, Appl. Phys. Lett., (2008). PDF ou PDF2 Interruptor de 60ns: NanonaTM High Speed & Low Loss Optical Switch Semiconductor optical switches reach the speed of light April 29, 2011 Ctistis, G., Yuce, E., Hartsuiker, A., Claudon, J., Bazin, M., Gérard, J., & Vos, W. (2011). Ultimate fast optical switching of a planar microcavity in the telecom wavelength range Applied Physics Letters, 98 (16) DOI: / switch a light beam within a semiconductor device at speeds of 0.3 picosecond 2 Tarefa: como detectar? Tema para José

3 Diversas formas e/ou dispositivos para realizar acoplamentos de multiplexagem

4 Multiplexagem em WDM

5 Acopladores

6 Acopladores

7 Acopladores

8 Acoplador baseado em micro-óptica

9 Acoplador bicônico e derivados
Razão de Divisão de Potência:

10 Acoplador com fibras deslocadas lateralmente

11 Acoplador com núcleo sobreposto

12 Acoplador com núcleo sobreposto

13 Acoplador com divisor de feixe

14 Acoplador em X

15 Acoplador em Z

16 Parte das perdas são atribuídas a diferentes tipos de acoplamentos Lembremos

17 Eficiência de Acoplamento Sensitividade ao desalinhamento transversal
SMF núcleo SMF núcleo ∆x SMF ωo = 5.15µm ωo = 25µm η(∆x) = e –(∆x/ωo)2

18 Eficiência de acoplamento Sensitividade de desalinhamento angular
SMF núcleo Ө SMF ωo = 5.15µm ωo = 25µm η(Ө) = e -(ΠӨωo/λ)2 Modo expandido melhora a sensitividade de desalinhamento transversal, mas aumenta a sensitividade angular. Modo limitado pelas dimensões da fibra -> bom compromisso Expanded mode improves transverse mis-alignment sensitivity, but increases angular sensitivity Mode size constrained by fiber dimensions  good compromise Low loss mode size converter from 0.3 µm square Si wire waveguides to singlemode fibres Electronics Letters -- 5 December Volume 38, Issue 25, p T. Shoji,1 T. Tsuchizawa,1 T. Watanabe,1 K. Yamada,1 and H. Morita1 1NTT Corporation, NTT Telecommunications Energy Laboratories, Kanagawa Pref., Japan (Received 24 June 2002) A novel integrated mode size converter for single-mode Si wire waveguides is presented. The mode size converter is constructed with two-dimensional tapered Si waveguides and overlaid high-index polymer waveguides. We calculated the proposed mode size converter characteristics, and fabricated 1.09 mm length Si wire waveguides with the converters. The measured loss of the mode size converter was 0.8 dB per conversion, and the total insertion loss through the sample with an Si wire waveguide was 3.5 dB.

19 Eficiência de acoplamento
Sensitividade por desalinhamento longitudinal SMF núcleo SMF núcleo ∆z η(z) = 1/(1+λz/(1+ Πz/2ωo2)2 For “large” ∆z lensing is required SMF ωo = 5.15µm ωo = 25µm SMF ωo = 5.15µm ωo = 25µm

20 Outros tipos de sistemas para acoplamento da luz com fibra para minimizar perdas

21 Lente no feixe O feixe Gaussiano pode ser caracterizado por sua fase e amplitude em qualquer ponto do feixe Para um acoplamento “perfeito” tanto a fase e amplitude devem estar casadas Componente óptico Gaussian beam can be characterized by a phase and amplitude at any point For “perfect” coupling both phase and amplitude must be matched

22 Lentes no feixe Aplicações Componentes passivos isoladores filtros
splitters circuladores WDM alguns são dispositivos com mais de 2 portas lasers receptores moduladores Projeção de feixe Solda a laser apontadores Componentes ópticos entre fibras Isolator Laser Passive components isolators filters splitters circulators WDMs… some are > 2 port devices Active components lasers receivers modulators Beam projection laser welding free-space pointing Tela

23 O que há em usar lentes discretas
Duram bastante tempo Alta performance Oferece desenho de dispositivos mais flexíveis Relativamente barato Continua a ser ”bons amigos” na industria MAS… A colocação de componentes adicionais, e.g., lentes reduce a robustes e confiabilidade aumento de custos de manipulação Maioria das lentes discretas são grandes em relação às fibras Aumento no tamanho das embalagens Aumento no tamanho do modo – OK para algumas aplicações mas não para outras WRT fibers With Respect To fibers

24 R - Radial Distance (au)
Graded-Index Lens GRIN lens very popular - high quality & cylindrical shape But, large and expensive Typical n(r) - Square Law R - Radial Distance (au) n(R) -Refractive Index (au) a R a GRIN Lens Fiber GRIN Lens

25 Imagem com sistema Fibra/Lente Grin
SM Fiber L=1/4 Pitch L > ¼ Pitch Graded Index MMF

26 Fibra-lente Fused “Collimated” Beam SMF Core (SMF) ¼ Pitch MMF Lens
Core (MMF) Fused “Collimated” Beam ¼ Pitch SMF Core (SMF) A graded index multi-mode fiber also has a square-law refractive index, thus is a small GRIN lens Fusing the appropriate length MMF to a SMF provides a lensed fiber in unitary structure

27 Fibras-Lentes Fundidas
Vantagens Podem ser fundidas em fibras Elimina a sensitividade do desalinhamento transversal de fibras SM Casamento de índice na interface – minimiza reflexões e perdas Tendo o mesmo diâmetro SMFsimplificação de desenho e empacotamento Custo da lente ~”zero” Oferece um bom compromisso entre sensitividades transversal e angular Altamente flexível: da expansão de modo simples para sistemas de focamento Podem ser fundidas em fibras Eliminates SM transverse mis-alignment sensitivity Index match at interface – minimizing reflections & loss Has same diameter as SMFdesign and packaging simplicity Lens cost is ~”zero” Provides a good compromise between transverse sensitivity and angular sensitivity Highly flexible: from simple mode expansion to focusing systems

28 Montagem da fibra-lente fundida Processos críticos
Core/core alignment Fiber eccentricity Core concentricity Reproducible fusion process Interface diameter control Bulging/necking Dopant diffusion control Means to polish endface Final length control Apex control Determination of beam parameters vs endface contour Relationship of endface contour and optical performance MMF SMF Fiber lens choice: Eccentricity Centricity of core Fusion compatability Uniformity & Flexibility) Accurate & reproducible lens length Post fusion After final polish 3. Fiber Lens Endface 2. Fiber Lens 1. Fiber/Lens Fused Interface

29 Outra opção de Fibra-Lente
The insertion of a silica “fiber section” between the SMF and the MMF lens adds additional flexibility to fiber-lens applications Silica Section SMF Core (SMF) MMF Lens Core (MMF)

30 Lembrem-se aquela da lente esférica formato de bola na frente da fibra

31 Acoplamento fibra-esfera/fibra-fibra
Understanding Ball Lenses Ball lenses are great optical components for improving signal coupling between fibers, emitters and detectors. They are also used in endoscopy, bar code scanning, ball pre-forms for aspheric lenses and sensor applications. Ball lenses are manufactured from a single substrate of glass and can focus or collimate light, depending upon the geometry of the input source. Half-ball lenses are also common and can be interchanged with (full) ball lenses if the physical constraints of an application require a more compact design. Essential Equations for Using Ball Lenses Figure 1: Key Parameters There are five key parameters needed to understand and use ball lenses (Figure 1): Diameter of Input Source (d), Diameter of Ball Lens (D), Effective Focal Length of Ball Lens (EFL), Back Focal Length of Ball Lens (BFL) and Index of Refraction of Ball Lens (n). EFL is very simple to calculate (Equation 1) since there are only two variables involved: Diameter of Ball Lens (D) and Index of Refraction (n). EFL is measured from the center of the ball lens, indicated by R in Figure 1. BFL (Equation 2) is easily calculated once EFL and D are known. Numerical Aperture NA (Equation 3) is dependent on EFL and d. It is a commonly referenced term and often used in lieu of d/D. (1) (2) (3) Since NA is often used, Figure 2 illustrates how it increases as the Diameter of the Input Source (d) also increases. Figure 2: Numerical Aperture vs. Diameter for Ball Lens Glass Types offered by Edmund Optics®. Application Examples Figure 3: Laser to Fiber Coupling Example 1: Laser to Fiber Coupling When coupling light from a laser into a fiber optic, the choice of ball lens is dependent on the NA of the fiber and the diameter of the laser beam, or the input source. The diameter of the laser beam is used to determine the NA of the ball lens. The NA of the ball lens must be less than or equal to the NA of the fiber optic in order to couple all of the light. The ball lens in contact with the fiber as shown in Figure 3. Initial Parameters Diameter of Input Laser Beam = 2mm Index of Refraction of Ball Lens = Numerical Aperture of Fiber Optic = 0.22 Calculated Parameter Diameter of Ball Lens (4) A N-BK7 ball lens (index of refraction of 1.517) of 6-8mm in diameter would be ideal for coupling a 2mm laser source into a 0.22NA fiber optic. One can easily try different indices of refraction in order to find the best ball lens for a laser to fiber coupling application. Figure 4: Fiber to Fiber Coupling Example 2: Fiber to Fiber Coupling To couple light from one fiber optic to another fiber optic of similar NA, two identical ball lenses are used. Place the two ball lenses in contact with the fibers as shown in Figure 4. If the fiber optics have the same NA, then the same logic as in Example 1 can be applied. Related Products

32 Pq há necessidade de um amplificador óptico?
Atenuação do sinal. De onde vem a atenuação do sinal? São várias as razões: longa distância, acoplamento entre outras. Qual a vantagem de ter um amplificador óptico? Principalmente amplificar um sinal óptico sem necessidade de converte-lo antes em elétrico.

33 AMPLIFICADOR ÓPTICO O QUE É PARA QUE É QUE TIPOS HÁ

34 Exemplo de comunicação óptica

35 Antigamente Tradicionais repetidores eletrônicos

36 Objetivos dos amplificadores

37 Amplificadores Ópticos
Amplifiers Definition: devices for amplifying the power of light beams German: Verstärker An optical amplifier is a device which receives some input signal and generates an output signal with higher optical power. Typically, inputs and outputs are laser beams, either propagating as Gaussian beams in free space or in a fiber. The amplification occurs in a so-called gain medium, which has to be “pumped” (i.e., provided with energy) from an external source. Most optical amplifiers are either optically or electrically pumped. − Laser Amplifiers versus Amplifiers Based on Optical Nonlinearities Most optical amplifiers are laser amplifiers, where the amplification is based on stimulated emission. Here, the gain medium contains some atoms, ions or molecules in an excited state, which can be stimulated by the signal light to emit more light into the same radiation modes. Such gain media are either insulators doped with some laser-active ions, or semiconductors (→ semiconductor optical amplifiers), which can be electrically or optically pumped. Doped insulators for laser amplification are laser crystals and glasses used in bulk form, or some types of waveguides, such as optical fibers (→ fiber amplifiers). The laser-active ions are usually either rare earth ions or (less frequently) transition-metal ions. A particularly important type of laser amplifier is the erbium-doped fiber amplifier, which is used mostly for optical fiber communications. In addition to stimulated emission, there also exist other physical mechanisms for optical amplification, which are based on various types of optical nonlinearities. Optical parametric amplifiers are usually based on a medium with χ(2) nonlinearity, but there are also parametric fiber devices using the χ(3) nonlinearity of a fiber. Other types of nonlinear amplifiers are Raman amplifiers and Brillouin amplifiers, exploiting the delayed nonlinear response of a medium. An important difference between laser amplifiers and amplifiers based on nonlinearities is that laser amplifiers can store some amount of energy, whereas nonlinear amplifiers provide gain only as long as the pump light is present. − Multipass Arrangements, Regenerative Amplifiers, and Amplifier Chains A bulk-optical laser amplifier often provides only a moderate amount of gain, typically only few decibels. This applies particularly to ultrashort pulse amplifiers, since they must be based on broadband gain media, which tend to have lower emission cross sections. The effective gain may then be increased either by arranging for multiple passes of the radiation through the same amplifier medium (multipass amplifier), or by using several amplifiers in a sequence (→ amplifier chains). Figure 1: Setup of a multipass femtosecond amplifier. Multipass operation (Figure 1) can be achieved with combinations of mirrors (for several passes with slightly different angular directions), or (mostly for ultrashort pulses) with regenerative amplifiers. For very large amplification factors, multi-stage amplifiers (amplifier chains) are often better suited. For example, a regenerative amplifier may amplify pulses to an energy of a few millijoules, and a multipass amplifier further boosts the pulse energy to hundreds of millijoules. Between the amplifier stages, the pulses can be spatially or spectrally filtered in various ways, helping to achieve a high beam quality and/or a shorter pulse duration. − Gain Saturation For high values of the input light intensity or fluence, the amplification factor of a gain medium saturates, i.e., is reduced (→ gain saturation). This is a natural consequence of the fact that an amplifier cannot add arbitrary levels of energy or power to an input signal. However, as laser amplifiers (particularly those based on solid-state gain media) store some amount of energy in the gain medium, this energy can be extracted within a very short time. Therefore, during some short time interval the output power can exceed the pump power by many orders of magnitude. − Detrimental Effects For high gain, weak parasitic reflections can cause parasitic lasing, i.e., oscillation without an input signal, or additional output components not caused by the input signal. This effect then limits the achievable gain. Even without any parasitic reflections, amplified spontaneous emission may extract a significant power from an amplifier. A related effect is that amplifiers also add some excess noise to the output. This applies not only to laser amplifiers, where excess noise can partly be explained as the effect of spontaneous emission, but also to nonlinear amplifiers. − Ultrafast Amplifiers Amplifiers of different kind may also be used for amplifying ultrashort pulses. In some cases, a high repetition rate pulse train is amplified, leading to a high average power while the pulse energy remains moderate. In other cases, a much higher gain is applied to pulses at lower repetition rates, leading to high pulse energies and correspondingly huge peak powers. A number of special aspects apply to such devices, and are discussed in the article on ultrafast amplifiers. − Important Parameters of an Optical Amplifier Important parameters of an optical amplifier include: the maximum gain, specified as an amplification factor or in decibels (dB) the saturation power, which is related to the gain efficiency the saturated output power (for a given pump power) the power efficiency and pump power requirements the saturation energy the time of energy storage (→ upper-state lifetime) the gain bandwidth (and possibly smoothness of gain spectrum) the noise figure and possibly more detailed noise specifications the sensitivity to back-reflections Different kinds of amplifiers differ very much e.g. in terms of saturation properties. For example, rare-earth-doped gain media can store substantial amounts of energy, whereas optical parametric amplifiers provide amplification only as long as the pump beam is present. As another example, semiconductor optical amplifiers store much less energy than fiber amplifiers, and this has important implications for optical fiber communications. − Applications Typical applications of optical amplifiers are: An amplifier can boost the (average) power of a laser output to higher levels (→ master oscillator power amplifier = MOPA). It can generate extremely high peak powers, particularly in ultrashort pulses, if the stored energy is extracted within a short time. It can amplify weak signals before photodetection, and thus reduce the detection noise, unless the added amplifier noise is large. In long fiber-optic links for optical fiber communications, the optical power level has to be raised between long sections of fiber before the information is lost in the noise. − Bibliography [1]P. Urquhart (ed.), Advances in Optical Amplifiers (open-access online edition available), InTech, Rijeka, Croatia (2011) See also: multipass amplifiers, amplifier noise, amplified spontaneous emission, amplification factor, fiber amplifiers, Raman amplifiers, semiconductor optical amplifiers, optical parametric amplifiers, regenerative amplifiers, ultrafast amplifiers, master oscillator power amplifier, chirped-pulse amplification, divided-pulse amplification

38 Diferentes tipos de Amplificadores Ópticos
Semicondutor (SOA) (= Semiconductor Optical Amplifier) SOA convencional GC-SOA (Gain-Clamped SOA) LOA (Linear Optical Amplifier) Fibra Óptica (FOA) Fibras dopadas com Terras Raras Erbium-Doped Fiber Amplifiers (EDFA) : C, L-Band Thulium-Doped Fiber Amplifiers (TDFA) : S-Band Praseodymium-Doped Fiber Amplifiers (PDFA) : O-Band Banda l(nm) Banda C (conventional) Banda L (long) Banda S (short) Conversosr de frequência  comprimento de onda

39 Conversosr de frequência  comprimento de onda http://www. ee. byu
Equation: f * λ = c where: f = frequency in Hertz (Hz = 1/sec) λ = wavelength in meters (m) c = the speed of light and is approximately equal to 3*108 m/s Frequency / Wavelength Calculator If you want to convert wavelength to frequency enter the wavelength in microns (μm) and press "Calculate f". The corresponding frequency will be in the "frequency" field in GHz. OR enter the frequency in gigahertz (GHz) and press "Calculate λ" if you want to convert to wavelength. Wavelength will be in μm. Wavelength: (λ) [μm] Frequency: (f) [GHz] **see nomograph below

40 http://www. teleco. com. br/tutoriais/tutorialdwdm/pagina_4
desde ha um tempo OFA: 1.1. EDFA (do Inglês: E rbium D oped F ibre A mplifier ) 1.2. EYDFA ( do Inglês: E rbium Y tterbium D oped F ibre A mplifier ) 1.3. PDFFA (do Inglês: P raseodymium D oped F luoride F ibre A mplifier ) 1.4. TDFFA (do Inglês: T hulium D oped F luorid F ibre A mplifier ) 1.5. RA (do Inglês: R aman A mplifier ) 1.6 Híbridos OWGA 2.1. EDWA (do Inglês: E rbium D oped W aveguide A mplifier ) 2.2. SOA (do Inglês: S emiconductor O ptical A mplifier ) •  LOA (do Inglês: L inear O ptical A mplifier ) •  TIA (do Inglês: T ransimpedance I ntegrated A mplifier )

41 Mapa atualizado (2011?) Do livro Advances in Optical Amplifiers, Edited by Paul Urquhart, 2011

42 Hoje TX representa o transmissor do sinal
Amplificadores a diodo laser Amplificadores a fibra dopada (Er, operam em 1,55m m ). O Amplificador Óptico a Fibra Dopada com Érbio (AFDE) pode funcionar como amplificador de potência para aumentar o nível do sinal de saída do transmissor; posicionado na entrada do receptor, como pré-amplificador, para aumentar a sensitividade na recepção; ou como repetidor ou amplificador de linha para amplificar o sinal já atenuado ao longo do enlace óptico. TX representa o transmissor do sinal RX representa o receptor do sinal, SMF representa a Fibra Monomodo Padrão (Standard Monomode Fibers) sendo o meio de transmissão, AFDE que representa o Amplificador a Fibra Dopada com Érbio.

43 Diagrama de blocos de um repetidor regenerativo
Uma das grandes vantagens dos amplificadores ópticos está no fato de um único amplificador poder substituir todo o complexo circuito que compõe um repetidor regenerativo. CAG representa o Controlador de Aumento e Ganho do repetidor regenerativo A conseqüência imediata é o aumento da velocidade de transmissão. Outro ponto importante é que esses amplificadores são transparentes à taxa de bits e pode-se aumentar a taxa de transmissão, por exemplo: de 155Mbps para 622Mbps, sem que seja necessário alterar o sistema de amplificação.

44 Componentes de um EDFA ou AFDE
laser semicondutor de bombeamento, operando em uma das bandas de absorção do Érbio, 980nm ou 1480nm por um acoplador que opera com multiplexação por divisão de comprimento de onda (WDM), cuja função é acoplar em uma mesma fibra a potência óptica do laser de bombeamento e o sinal óptico a ser amplificado um trecho limitado de fibra dopada com érbio (FDE), responsável pelo processo de amplificação.

45 Diagrama de níveis de energia do Er3+

46 Espectro de emissão do LiNbO3:Er3+ - parte Vis-IVP

47

48 Tipos de emissão: Estimulada e espontânea

49 Como opera o EDFA Um EDFA consiste de uma extensão curta de fibra(~ 10m) dopada com uma pequena quantidade controlada de Er3+. Os íons de Er3+ tem vários estados de energia (meta-estados). Quando o Er está num estado excitado, um fóton de luz poderá estimular para que ceda algo de sua energia na forma de luz voltando para um estado de menor energia mais estável. A medida que o sinal de entrada está sendo alimentado no sistema, um laser diodo gera um sinal de bombeio (10 a 200 mW)(l = 980nm ou 1480nm) de tal forma que os íons de Er absorverão os fótons indo para estados excitados.

50 Princípios do Amplificador Óptico 1
ERBIUM ELECTRONS IN FUNDAMENTAL STATE PUMP PHOTON 980 nm PUMP PHOTON 980 nm ENERGY ABSORPTION ERBIUM ELECTRONS IN EXCITED STATE IN FUNDAMENTAL STATE

51 Princípios do Amplificador Óptico 2
PUMP PHOTON 980 nm TRANSITION METASTABLE STATE EXCITED STATE FUNDAMENTAL STATE NR

52 Princípios do Amplificador Óptico 3
PUMP PHOTON 980 nm TRANSITION METASTABLE STATE SIGNAL PHOTON 1550 nm STIMULATED PHOTON FUNDAMENTAL STATE EXCITED STATE

53 Perfil do Ganho do Amplificador Óptico
ASE = Amplified Spontaneous Emission

54 ASE = Amplified Spontaneous Emission
O que é ASE Efeitos da ASE sobre sistemas em cascata Como atenuar a ASE Aplicações positivas da ASE

55 Amplificador Óptico: Amplificação de Multi-Comprimentos de Onda

56 Configurações de montagens de EDFA
OI = Optical Isolator WSC = Wavelength Selective Coupler (a) Bombeamento co-propagado – baixo ruído baixa potência de saída (b) Bombeamento contra-propagado – maior potência de saída mas maior ruído (c)Bombeamento dual

57 Melhor bombear com 980nm ou 1480nm?
Baixo ASE, amplificador de ruído bx Com 1480nm Laser de bombeio maior Maior potência de saída Não tão eficiente Grau de inversão de população é menor

58 Quais fontes de laser para bombear?

59 Outro exemplo GFF = Gain-Flattening Filters

60 Em sistemas de transmissão usamos unidades de potência em dB. Assim........

61 DECIBEL (dB)– num sistema de transmissão
Potência de Entrada = Pin Potência de Saída = Pout Transmissão do Sistema : Exemplos: -10dB é Pout = Pin/10 -40dB é Pout = Pin10-4 Transmissão em dB: dBm é a Potência em dB relativo a 1mW Exemplos: -10dBm é P = 0,1W +40dB é P = 10W

62 Ganho do EDFA O ganho do EDFA depende do comprimento da fibra. O ganho começa a decrescer após certo comprimento devido a que o bombeio não tem potência suficiente para criar a inversão de população. Assim a região não bombeada absorve o sinal Gmax = exp(rsL) s é a seção transversal da emissão do sinal r é a concentração de Er L é o comprimento do amplificador de fibra

63 Ganho e ruído nas configurações anteriores

64 Emissão Espontânea Amplificada (ASE)
A fonte dominante de ruído num amplificador óptico é a Emissão Espontânea Amplificada (ASE) Alguns dos íons de Er excitados decaem para o estado fundamental com emissão espontânea antes que tenha tempo de se encontrar com um fóton do sinal de entrada. Assim o fóton é emitido com a fase randômica e direção Uma fração muito pequena dos fótons emitidos ocorrerão na mesma direção da fibra e confinados

65 Potência de saída vs comprimento de onda
ASE = Amplified Spontaneous Emission Amplificação entre 1.53 e 1.56 mm.

66 Largura de banda de ganho de amplificadores ópticos

67 Uma das formas para atenuar ASE

68 Referências Fiber-Optic Communication Systems, Govind Agrawal, 2nd Edition, 1997. Erbium-Doped Fiber Amplifiers: Fundamentals and Technology, P.C. Becker, 1999. Fiber Optic Test and Measurement, D. Dercikson, 1998 Optical Fiber Amplifiers: Materials, Devices and Applications, Sudo Shoichi, 1997. Rare-Earth-Doped Fiber Lasers and Amplifiers, Michel J. F. Digonnet, 2001. Semiconductor Optical Amplifier, Michael J. Connelly, 2002. Advances in Optical Amplifiers, Edited by Paul Urquhart, 2011.

69 Notação de alguns AO de fibra
EDFA (do Inglês: Erbium Doped Fibre Amplifier ) EYDFA ( do Inglês: Erbium Ytterbium Doped Fibre Amplifier ) PDFFA (do Inglês: Praseodymium Doped Fluoride Fibre Amplifier ) TDFFA (do Inglês: Thulium Doped Fluoride Fibre Amplifier ) RA (do Inglês: Raman Amplifier ) Híbridos

70 Notação de alguns AO de guia de onda planar – OWGA – Optical WaveGuide Amplifier
EDWA (do Inglês: Erbium Doped Waveguide Amplifier ) SOA (do Inglês: Semiconductor Optical Amplifier ) LOA (do Inglês: Linear Optical Amplifier ) TIA (do Inglês: Transimpedance Integrated Amplifier )

71 SOA Uma corrente elétrica passa através do dispositivo, com a finalidade de excitar elétrons na região ativa. Quando os fótons se propagam através da região ativa pode fazer com que alguns destes elétrons percam energia na forma de fótons que coincidam com os comprimentos de onda daqueles incidentes. Assim o sinal que passa através da região ativa é amplificada e dizemos que houve ganho. Silicon or semiconductor fiber optic amplifiers (SOA) function in a similar way to a basic laser. The structure is much the same, with two specially designed slabs of semiconductor material on top of each other, with another material in between them forming the 'active layer.’ An electrical current is set running through the device in order to excite electrons which can then fall back to the non-excited ground state and give out photons.  Incoming optical signal stimulates emission of light at its own wavelength.  SOA can be classified into two groups, Fabry-Perot Amplifiers (FPA) and Traveling Wave Amplifiers (TWA).  The difference is the reflectivity coefficient value of both mirror surfaces.

72 Dispositivo

73 Optical Amplifiers: Internal Design
Optical amplification is a key DWDM enabling technology Amplifiers use wavelength band separation (bands : BLUE, RED, IR) to minimize gain tilt Optimized multi-stage amplifier design 1st stage optimized for low noise figure 2nd stage optimized for high output power

74 Multiestágios de AO PUMP Input Output Signal 1st Active Stage
Er3+ Doped Fiber Optical Isolator 1st Active Stage Co-pumped 2nd Active Stage Counter-pumped Nf 1st/2nd stage = Pin - SNRo [dB] - 10 Log (hc2 / 3) Nftotal = Nf1+Nf2/G1

75 Referências

76 Distributed Raman Amplifier (DRA)
DRA está baseado sobre espalhamento Raman. Um bombeamento maior é co-lançado num comprimento de onda menor daquele do sinal a ser amplificado.

77 Espectroscopia Raman Basic theory
The Raman effect occurs when light impinges upon a molecule and interacts with the electron cloud of the bonds of that molecule. The amount of deformation of the electron cloud is the polarizability of the molecule. The amount of the polarizability of the bond will determine the intensity and frequency of the Raman shift. The photon (light quantum), excites one of the electrons into a virtual state. When the photon is released the molecule relaxes back into vibrational energy state. The molecule will typically relax into the first vibration energy states, and this generated Stokes Raman scattering. If the molecule was already in an elevated vibrational energy state, the Raman scattering is then called Anti-Stokes Raman scattering.

78 Complementação sobre AO
ERBIUM-DOPED PLANAR OPTICAL AMPLIFIERS A. Polman Publicado em: Proc. 10th European Conference on Integrated Optics (ECIO) Paderborn, Germany, April , 2001, p. 75 (2001)

79 Transferência de energia Er - Eu
0.19at.%Er 0.19at.%Er, 0.44at%Eu We present an investigation of Er3+ photoluminescence in Y2O3 waveguides codoped with Eu3+. As a function of europium concentration we observe an increase in decay rate of the erbium 4I11/2 energy level and an increase of the ratio of photoluminescence emission from the 4I13/2 and 4I11/2 states. Using a rate equation model, we show that this is due to an energy transfer from the 4I11/2 to 4I13/2 transition in erbium to europium. This increases the branching ratio of the 4I11/2 state towards the 4I13/2 state and results in a higher steady state population of the first excited state of erbium. Absolute intensity enhancement of the 4I13/2 emission is obtained for europium concentrations between 0.1 and 0.3 at. %. In addition, the photoluminescence due to upconversion processes originating from the 4I11/2 state is reduced. Using such state-selective energy transfer the efficiency of erbium doped waveguide amplifiers can be increased. False color image of the green emission of Er31 with and without europium. The green emission from the Er31 4S3/2 state is represented in black. 980 nm light is coupled into the planar waveguide from a fiber ~left hand side of the images!. In the presence of 0.44 at. % europium, the green upconversion emission is reduced considerably. 4I11/2=> 4I15/2 = 980nm 4I13/2=>4I15/2 = 1540nm J. Appl. Phys., Vol. 88, No. 8, 15 October 2000

80 Níveis de energia do Er3+

81 Transferência de energia de QD de Si e Er

82

83 Outros detalhes sobre EDFA

84 Fim sobre AO

85 Defeitos em sólidos, centros de cor e Redes de Bragg
Próxima aula Defeitos em sólidos, centros de cor e Redes de Bragg

86 DECIBEL (dB)– num sistema de transmissão
Potência de Entrada = Pin Potência de Saída = Pout Transmissão do Sistema : Exemplos: -10dB é Pout = Pin/10 -40dB é Pout = Pin10-4 Transmissão em dB: dBm é a Potência em dB relativo a 1mW Exemplos: -10dBm é P = 0,1W +40dB é P = 10W

87 Modos numa fibra Fig.: Electric field contour lines for all the guided modes of a fiber with a top-hat refractive index profile (→ step index fiber). The two colors indicate different signs of electric field values. The lowest-order mode (l = 1, m = 0, called LP01 mode) has an intensity profile which is similar to that of a Gaussian beam. In general, light launched into a multimode fiber will excite a superposition of different modes, which can have a rather complicated shape. Fiber Modes – Single-Mode vs. Multimode Fibers A fiber can support one or several (sometimes even many) propagation modes the intensity distributions of which are located at or immediately around the fiber core, although some of the intensity may propagate within the fiber cladding. Other modes are not restricted to the core region and all called cladding modes. The power in these is usually lost after some distance of propagation, but can in some cases propagate over longer distances. Outside the cladding, there is typically a protective polymer coating, which gives the fiber improved mechanical strength and protection against moisture, and also determines the losses for cladding modes. An important distinction is that between single-mode and multimode fibers: Single-mode fibers usually have a relatively small core (with a diameter of only a few micrometers) and can guide only a single spatial mode (disregarding the fact that there are two different polarization directions), the profile of which in most cases has roughly a Gaussian shape. Changing the launch conditions only affects the launched power, while the spatial distribution of the light exiting the fiber is fixed. Efficiently launching light into a single-mode fiber usually requires a laser source with good beam quality and precise alignment of the focusing optics in order to achieve mode matching. There are actually also large mode area fibers with single-mode guidance, where the alignment tolerances are lower in terms of position but higher in terms of angle (which is less of a problem). Multimode fibers usually have a larger core and/or a larger index difference between core and cladding, so that they support multiple modes with different intensity distributions (see the figure below). In this case, the spatial profile of light exiting the fiber core may depend on the launch conditions, which determine the distribution of power among the spatial modes. Long-range optical fiber communications systems usually use single-mode fibers, because the different group velocities of different modes would mess up the data at high data rates; for shorter distances, however, multimode fibers are more convenient as the demands on light sources and component alignment are lower. Therefore, local area networks (LANs), except those for highest bandwidth, normally use multimode fiber. Single-mode fibers are also normally used for fiber lasers and amplifiers. Multimode fibers are often used e.g. for the transport of light from a laser source to the place where it is needed, particularly when the light source has a poor beam quality and/or the high optical power requires a large mode area. Different modes of a fiber can be coupled via various effects, e.g. by bending, or often by irregularities in the refractive index profile. These may be unwanted or purposely introduced, e.g. as fiber Bragg gratings. Waveguide theory shows that an important factor for the coupling between different fiber modes is the difference of their wavenumbers, which for efficient coupling has to match the wavenumber of a coupling disturbance. Main Parameters The design of a step-index fiber can be characterized with only two parameters, e.g. the core radius a and the refractive index difference Δn between core and cladding. Typical values of the core radius are a few microns for single-mode fibers and tens of microns or more for multimode fibers. Instead of the refractive index difference, one usually uses the numerical aperture, defined as which is the sine of the maximum acceptable angle of an incident beam with respect to the fiber axis (considering the launch from air into the core in a ray-optic picture). The NA also basically quantifies the strength of guidance. Typical values are of the order of 0.1 for single-mode fibers, even though actual values vary in a relatively large range. For example, large mode area single-mode fibers can have low numerical apertures below 0.05, while some rare-earth doped fibers have values of 0.3 and higher for a high gain efficiency. NA values around 0.3 are typical for multimode fibers. The sensitivity of a fiber to bend losses strongly diminishes with increasing NA, which causes strong confinement of the mode field to the core. Another frequently used parameter is the V number which is a kind of normalized frequency. Single-mode guidance is achieved when the V number is below about Multimode fibers often have huge V values.

88 Fiber Modes – Single-Mode vs. Multimode Fibers
A fiber can support one or several (sometimes even many) propagation modes the intensity distributions of which are located at or immediately around the fiber core, although some of the intensity may propagate within the fiber cladding. Other modes are not restricted to the core region and all called cladding modes. The power in these is usually lost after some distance of propagation, but can in some cases propagate over longer distances. Outside the cladding, there is typically a protective polymer coating, which gives the fiber improved mechanical strength and protection against moisture, and also determines the losses for cladding modes. An important distinction is that between single-mode and multimode fibers: Single-mode fibers usually have a relatively small core (with a diameter of only a few micrometers) and can guide only a single spatial mode (disregarding the fact that there are two different polarization directions), the profile of which in most cases has roughly a Gaussian shape. Changing the launch conditions only affects the launched power, while the spatial distribution of the light exiting the fiber is fixed. Efficiently launching light into a single-mode fiber usually requires a laser source with good beam quality and precise alignment of the focusing optics in order to achieve mode matching. There are actually also large mode area fibers with single-mode guidance, where the alignment tolerances are lower in terms of position but higher in terms of angle (which is less of a problem). Multimode fibers usually have a larger core and/or a larger index difference between core and cladding, so that they support multiple modes with different intensity distributions (see the figure below). In this case, the spatial profile of light exiting the fiber core may depend on the launch conditions, which determine the distribution of power among the spatial modes.

89 Fig.: Electric field contour lines for all the guided modes of a fiber with a top-hat refractive index profile (→ step index fiber). The two colors indicate different signs of electric field values. The lowest-order mode (l = 1, m = 0, called LP01 mode) has an intensity profile which is similar to that of a Gaussian beam. In general, light launched into a multimode fiber will excite a superposition of different modes, which can have a rather complicated shape. Long-range optical fiber communications systems usually use single-mode fibers, because the different group velocities of different modes would mess up the data at high data rates; for shorter distances, however, multimode fibers are more convenient as the demands on light sources and component alignment are lower. Therefore, local area networks (LANs), except those for highest bandwidth, normally use multimode fiber. Single-mode fibers are also normally used for fiber lasers and amplifiers. Multimode fibers are often used e.g. for the transport of light from a laser source to the place where it is needed, particularly when the light source has a poor beam quality and/or the high optical power requires a large mode area. Different modes of a fiber can be coupled via various effects, e.g. by bending, or often by irregularities in the refractive index profile. These may be unwanted or purposely introduced, e.g. as fiber Bragg gratings. Waveguide theory shows that an important factor for the coupling between different fiber modes is the difference of their wavenumbers, which for efficient coupling has to match the wavenumber of a coupling disturbance. Main Parameters The design of a step-index fiber can be characterized with only two parameters, e.g. the core radius a and the refractive index difference Δn between core and cladding. Typical values of the core radius are a few microns for single-mode fibers and tens of microns or more for multimode fibers. Instead of the refractive index difference, one usually uses the numerical aperture, defined as                      which is the sine of the maximum acceptable angle of an incident beam with respect to the fiber axis (considering the launch from air into the core in a ray-optic picture). The NA also basically quantifies the strength of guidance. Typical values are of the order of 0.1 for single-mode fibers, even though actual values vary in a relatively large range. For example, large mode area single-mode fibers can have low numerical apertures below 0.05, while some rare-earth doped fibers have values of 0.3 and higher for a high gain efficiency. NA values around 0.3 are typical for multimode fibers. The sensitivity of a fiber to bend losses strongly diminishes with increasing NA, which causes strong confinement of the mode field to the core. Another frequently used parameter is the V number                                    which is a kind of normalized frequency. Single-mode guidance is achieved when the V number is below about Multimode fibers often have huge V values.