Basic Optical Components - PDF Free Download

Basic Optical Components Jorge M. Finochietto Córdoba 2012 LCD EFN UNC Laboratorio de Comunicaciones Digitales Facultad de Ciencias Exactas, Físicas y Naturales Universidad Nacional de Córdoba, Argentina

Optical Networks Seminar Overview Basic Components Network Elements Network Design Network Protocols Transport and Grooming Optical Components 2 / 51

Outline 1 Passive Devices 2 Active Devices Optical Components 3 / 51

Outline 1 Passive Devices Fibers Couplers Isolators and Circulators Filters and Multiplexers 2 Active Devices Optical Components Passive Devices 4 / 51

Outline 1 Passive Devices Fibers Couplers Isolators and Circulators Filters and Multiplexers 2 Active Devices Optical Components Passive Devices Fibers 5 / 51

Optical Fiber Optical Fiber Guides optical waves (wavelengths) by total internal reflection Made of glass or plastic: core (n 1 ) + cladding (n 2 ) + coating Refractive index (ratio of speed of light): n 1 1,45 n 1 n 2 Behaves as a waveguide supporting different propagation modes Multi-mode (MM) rate distance limited by modal dispersion Single-mode (SM) rate distance limited by chromatic dispersion and nonlinear effects Optical Components Passive Devices Fibers 6 / 51

Optical Fiber Attenuation Optical Components Passive Devices Fibers 7 / 51

Outline 1 Passive Devices Fibers Couplers Isolators and Circulators Filters and Multiplexers 2 Active Devices Optical Components Passive Devices Couplers 8 / 51

Couplers Concept Used to combine or split optical signals Made by fusing fibers together, or using waveguides in integrated optics Directional coupling: incoming signal power is distributed among output ports Optical Components Passive Devices Couplers 9 / 51

Couplers Basic Wavelenght-Independent 2 2 Model A 2 2 coupler consists of 2 input ports and 2 output ones Output power at port i (Pi O ) can be modelled as a function of the input power at each port j (Pj O ) as follows P O 1 = αp I 1 + (1 α)p I 2 P O 2 = (1 α)p I 1 + αp I 2 An excess loss β above the coupling loss α needs to be considered [ ] P1 O = αp1 I + (1 α)p2 I β [ ] P2 O = (1 α)p1 I + αp2 I β α is assumed the same λ k (wavelength-independent) Optical Components Passive Devices Couplers 10 / 51

Applications Add/Drop Couplers Used to drop a copy of an incoming signal add another one to the path Implemented by 3dB 2 2 coupler (α = 0,5) Half of the power of each input appears at each output 50/50 Optical Components Passive Devices Couplers 11 / 51

Applications Add/Drop Ring Network (Best Case) N nodes interconnected to a commong optical ring by means of add/drop couplers Each node transmits to its forward neighbor Source and sinks separated by 2 couplers Source signal attenuated by 6dB at sink node if no fiber loss is considered Optical Components Passive Devices Couplers 12 / 51

Applications Add/Drop Ring Network (Worst Case) N nodes interconnected to a commong optical ring by means of add/drop couplers Each node transmits to its backward neighbor Source and sinks separated by N couplers Source signal attenuated by N 3dB at sink node if no fiber loss is considered Optical Components Passive Devices Couplers 13 / 51

Applications Star Couplers N nodes interconnected to a N N star coupler A star coupler can be constructed by interconnecting 3dB 2 2 couplers Each node transmits to any neighbor Source and sinks separated by log 2 (N) couplers Source signal attenuated by log 2 (N) 3dB at sink node if no fiber loss is considered Optical Components Passive Devices Couplers 14 / 51

Applications Tap Used to tap off a small portion of the power from a ligth stream for monitoring purposes Designed with values of α close to 1 (0.9-0.95) Considers only one active input port 90/10 Optical Components Passive Devices Couplers 15 / 51

Applications Splitter 1 N Distributes one transmitted signal among N receivers One Nth of the power of the input appears at each output P O i = PI N (i.e.; α = 1/N) Optical Components Passive Devices Couplers 16 / 51

Applications Combiner N 1 Combines at most N transmitted signals into a single one Since couplers are reciprocal devices, both splitters and couplers are the same device but working on different directions? Optical Components Passive Devices Couplers 17 / 51

Applications Combiner N 1 Combines at most N transmitted signals into a single one Since couplers are reciprocal devices, both splitters and couplers are the same device but working on different directions Power loss Optical Components Passive Devices Couplers 18 / 51

Couplers Basic Wavelenght-Dependent 2 2 Model Coupling ratio α can be designed wavelength dependent Output power at port i (Pi O (λ i )) can be modelled as a function of the input power at each port j (Pj O ) as follows P O 1 = α 1 P I 1(λ 1 ) + (1 α 2 )P I 2(λ 2 ) P O 2 = (1 α 1 )P I 1(λ 1 ) + α 2 P I 2(λ 2 ) Note that if α 1 + α 2 = 1 ] P1 O = α 1 [P 1(λ I 1 ) + P2(λ I 2 ) [ ] P2 O = (1 α 1 ) P1(λ I 1 ) + P2(λ I 2 ) A lossless splitter/combiner for α 1 1 (aka WDM coupler) Optical Components Passive Devices Couplers 19 / 51

Use Case Unidirectional Passive Optical Network A unidirectional Passive Optical Network (PON) uses 2 wavelengths 1500nm downstream data 1310nm upstream data Both wavelengths can be combined/splitted without loss However, both wavelengths are distributed/gathered with loss Head Node End Nodes Optical Components Passive Devices Couplers 20 / 51

Outline 1 Passive Devices Fibers Couplers Isolators and Circulators Filters and Multiplexers 2 Active Devices Optical Components Passive Devices Isolators and Circulators 21 / 51

Isolators and Circulators Isolators 1 2-port nonreciprocal passive device that behaves as diode 2 Allows transmission in only one direction, while blocks it in the other direction. 3 Key parameters 1 Insertion loss: loss in the forward direction ( 1dB) 2 Isolation: loss in the return direction ( 40 50dB) 4 Used to prevent reflections from entering devices like optical amplifiers and lasers Optical Components Passive Devices Isolators and Circulators 22 / 51

Isolators and Circulators Circulators 1 Multi-port nonreciprocal passive device that behaves as a sequential switch 2 Allows transmission in only one direction, while blocks it in others direction. 3 A N-port circulator can be modelled by the output signal at port i (λ O i ) as a function of the input signal at port j (λ O j ) as follows λ O i = λ I j where j = (i + 1) %N Optical Components Passive Devices Isolators and Circulators 23 / 51

Application Wavelength Add/Drop Couplers can implement add/drop functions on different wavelengths with datapath penalty (3dB loss) 50/50 Optical Components Passive Devices Isolators and Circulators 24 / 51

Application Wavelength Add/Drop Couplers can implement add/drop functions on different wavelengths with datapath penalty (3dB loss) Interference Optical Components Passive Devices Isolators and Circulators 25 / 51

Application Wavelength Add/Drop Couplers can implement add/drop functions on different wavelengths with datapath penalty (3dB loss) Circulators can implement add/drop on the same wavelength without datapath loss Optical Components Passive Devices Isolators and Circulators 26 / 51

Application Wavelength Add/Drop Couplers can implement add/drop functions on different wavelengths with datapath penalty (3dB loss) Circulators can implement add/drop on the same wavelength without datapath loss? Optical Components Passive Devices Isolators and Circulators 28 / 51

Application Wavelength Add/Drop Couplers can implement add/drop functions on different wavelengths with datapath penalty (3dB loss) Circulators can implement add/drop on the same wavelength without datapath loss However, circulators cannot add/drop single wavelengths Optical Components Passive Devices Isolators and Circulators 29 / 51

Use Case Bidirectional Passive Optical Network A bidirectional Passive Optical Network (PON) uses the same wavelength for downstream and upstream data Head Node End Nodes Optical Components Passive Devices Isolators and Circulators 30 / 51

Outline 1 Passive Devices Fibers Couplers Isolators and Circulators Filters and Multiplexers 2 Active Devices Optical Components Passive Devices Filters and Multiplexers 31 / 51

Filters and Multiplexers Concepts Enable wavelength selection functions Filtering: 2-port (only select) or 3-port (select-and-reject) Multiplexing and demultiplexing Optical Components Passive Devices Filters and Multiplexers 32 / 51

Filters and Multiplexers Fiber Bragg Grating (FBG) Transparent device with a periodic variation of the refractive index, so that a large reflectivity may be reached in some wavelength range Optical Components Passive Devices Filters and Multiplexers 33 / 51

Applications Add/Drop A drop function can be implemented by concatenating a circulator and a FBG An add function could be implemented by? Optical Components Passive Devices Filters and Multiplexers 34 / 51

Applications Add/Drop A drop function can be implemented by concatenating a circulator and a FBG An add function could be implemented by a circulator: no loss but blocks in-transit wavelengths Optical Components Passive Devices Filters and Multiplexers 35 / 51

Applications Add/Drop A drop function can be implemented by concatenating a circulator and a FBG An add function could be implemented by a circulator: no loss but blocks in-transit wavelengths a coupler: loss but in-transit wavelengths pass through Optical Components Passive Devices Filters and Multiplexers 36 / 51

Filters and Multiplexers Arrayed Waveguide Grating (AWG) Made by 2 couplers interconnected by an array of waveguides An 1 N wavelength (de)multiplexer can be implemented 1 Incoming signal (multiple wavelengths) 2 Signal distribution to waveguides with different lengths 3 Different phase shifts are aplied to each copy of the signal 4 Interference at output ports 5 Each different wavelength is constructed No loss introduced on the datapath (ideally) Optical Components Passive Devices Filters and Multiplexers 37 / 51

Applications Add/Drop All wavelengths can be demultiplexed and multiplexed again with no loss The drop wavelength is terminated on a receiver The add wavelength is originated at a transmitter Optical Components Passive Devices Filters and Multiplexers 38 / 51

Applications Add/Drop All wavelengths can be demultiplexed and multiplexed again with no loss The drop wavelength is terminated on a receiver The add wavelength is originated at a transmitter More than one wavelength can be dropped/added Optical Components Passive Devices Filters and Multiplexers 39 / 51

Outline 1 Passive Devices 2 Active Devices Switches Converters Optical Components Active Devices 40 / 51

Outline 1 Passive Devices 2 Active Devices Switches Converters Optical Components Active Devices Switches 41 / 51

Switches Static Crossconnect Multiplexers can be used to build static crossconnects Fixed capability of routing wavelengths over different ports As a result provisioning is hardwired (patch panel) No (fast) protection at all Optical Components Active Devices Switches 42 / 51

Switches Reconfigurable Crossconnect Optical switches enable reconfigurable wavelength crossconnect functions Used for either provisioning and/or protection Switches must be nonblocking An unused input port can be connected to any unsed output port Optical Components Active Devices Switches 43 / 51

Switches Spanke Architecture An N N switch made by N (1 N) and N (N 1) Strict-sense nonblocking (i.e., regardless of previous connections) Attractive since 1 N elements can be built directly by means of MEMS (movable mirrors), or 1 N splitter plus ON/OFF optical gates (e.g, SOA) Optical Components Active Devices Switches 44 / 51

Switches Wavelength Contention Nonblocking switches do not guarantee successful crossconnects Wavelength contention can occur on output ports Same wavelength on different ports (i.e., fibers) Optical Components Active Devices Switches 45 / 51

Switches Wavelength Contention Nonblocking switches do not guarantee successful crossconnects Wavelength contention can occur on output ports Same wavelength on same port (i.e., fiber) Optical Components Active Devices Switches 46 / 51

Outline 1 Passive Devices 2 Active Devices Switches Converters Optical Components Active Devices Converters 47 / 51

Converters Wavelength Converters Converts data from one wavelength to another one Applications Short-Reach (1310nm) to Long-Reach (transparent) transponder Improve network utilization (more later) Classification Fixed-input - Fixed-output Fixed-input - Variable-output Variable-input - Fixed-output Variable-input - Variable-output Simplest approach: optoelectronic conversion Optical Components Active Devices Converters 48 / 51

Converters Optoelectronic Converters Different levels of transparency a) 1R: only apmlification b) 2R: amplification + reshaping c) 3R: amplification + reshaping + retiming Optical Components Active Devices Converters 49 / 51

Converters Wavelength Conversion Nonblocking switches do not guarantee successful crossconnects Wavelength conversion can be done at output ports Same wavelength on same output port (i.e., fiber) Optical Components Active Devices Converters 50 / 51