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# Introduction to Optical Backbone Networks

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The slides cover: optical communication basics, WDM, OTN and Packet Optical Integration

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### Introduction to Optical Backbone Networks

4. 4. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Waves 4 Longitudinal wave • Oscillates in the same direction as propagation • Ex:- Sound waves Transverse waves • Ex:- Light Both longitudinal or transverse waves follow basic wave principles
5. 5. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Terminology 5 : length of a wave in a particular medium. Common unit: nanometers (nm), 10-9 m f: the number of times that a wave is produced within a particular time period. Common unit: TeraHertz (Thz), 1012 cycles per second c = f  c = velocity of light in a vacuum = 3 x 108 m/s (constant) f = frequency (Hz)  = wavelength (m) f  1 / 
6. 6. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU 6 cannot see! 1. wavelength of these waves is too long for the human eye to detect 2. radio waves are not scattered as much as light waves by gas and dust, and can penetrate clouds 850, 1310, 1550 nm
7. 7. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU dB vs. dBm dB (Decibels) • unit of level (relative measure) • Standard logarithmic unit for the ratio of two quantities • X dB is 10-X/10 in linear dimension • Ex:- 3 dB Attenuation = 10-0.3 = 0.501 • In optical fibres, the ratio is power and represents loss or gain dBm (Decibels-milliwatt) • absolute value • used for output power and receive sensitivity • dBm : Decibel referenced to a milliwatt • X mW = 10log10(X) dBm • Y dBm = 10Y/10 mW • Ex:- 0 dBm = 1 mW, 17dBm = 50 mW 7
8. 8. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Optical Fiber Source : 1. http://www.okokchina.com/product/Electrical/Generators-Cables-Related-Products/Insulated-Wires-Cables-Including-Optical-Fibers/index_13.htm 2. http://en.wikipedia.org/wiki/Multi-mode_optical_fiber 1. 2. Metal (copper) loop Fiber cable 8
9. 9. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Fiber • Capacity • Distance The optical fiber cable in the foreground has the equivalent capacity of the copper cable in the background Source : http://www.igpolicysummit.org/uncategorized/copper-v-fiber-verizon-makes-a-change-following-sandys-devastation/ 9
11. 11. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU q1 n2 n1 Cladding q0 Core Intensity Profile Propagation in Fiber • Light propagates by total internal reflections at the core-cladding interface • Total internal reflections are lossless • Each allowed ray is a mode
12. 12. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Single vs. multi mode Source: http://osd.com.au/multimode-versus-singlemode/ Mode=Path of light High Attenuation (3 dB/km) High dispersion Expensive today (because of less demand) Attenuation = 0.22 dB/km (G.652 @ 1550nm) No mode dispersion 12
13. 13. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU n2 n1 Cladding Core n2 n1 Cladding Core Multi mode vs. Single mode propagation • Multimode –Core diameter varies • step index: 50 mm • graded index: 62.5 mm • Single-mode –Core diameter is about 9 mm Refractive index n = c / v
16. 16. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Attenuation Dispersion Nonlinearity Waveform After 1000 KmTransmitted Data Waveform Distortion It may be a Digital signal, but It’s an Analog optical transmission Propagation issues 16 1 0 Fiber is not a perfect waveguide for light Processed in the electrical domain Processed in the optical domain
17. 17. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Analog transmission effects • Attenuation: – Reduces power level with distance • Dispersion and nonlinear effects: – Erodes clarity with distance and speed • Noise and Jitter: Leading to a blurred image 17 Ex:-FWM
18. 18. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Attenuation • The extent to which lighting intensity from the source is diminished as it passes through a given length of FO cable, tubing or light pipe • Loss due to absorption by impurities – 1400 nm peak due to OH ions • Specified in loss per kilometer (dB/km) – 0.40 dB/km at 1310 nm – 0.25 dB/km at 1550 nm 1310 Window 1550 Window
19. 19. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Attenuation, cont., Source: http://osd.com.au/multimode-versus-singlemode/ Water peak created by fiber imperfections Lowest loss band 19
20. 20. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU OA (works fully in the optical domain) Solution for Attenuation Loss Optical Amplification 20
21. 21. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU • Polarization Mode Dispersion (PMD) Single-mode fiber supports two polarization states Fast and slow axes have different group velocities Causes spreading of the light pulse • Chromatic Dispersion (CD) Different wavelengths travel at different speeds Causes spreading of the light pulse (ps/nm-km) Types of Dispersion 21 Physical phenomenon of signal distortion caused when various modes carrying signal energy or different frequencies of the signal have different group velocity and disperse from each other during propagation
23. 23. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU 60 Km SMF-28 4 Km SMF-28 10 Gbps 40 Gbps Limitations From CD t t • Dispersion causes pulse distortion • Higher bit-rates and shorter pulses are less robust to Chromatic Dispersion • Limits "how fast“ and “how far” 23
24. 24. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Combating CD • Use DSF and NZDSF fibers – G.653 & G.655 • Dispersion Compensating Fiber (DCF/DCM) • Transmitters with narrow spectral width 24
25. 25. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU DSF and NZDSF Wavelength/nm Dispersion coefficient 1310 1550 17 ps/nm/km 4.5 ps/nm/km G.652: widely used, need DCF for high rate transmission, cheapest G.655: little dispersion to avoid FWM, expensive G.653: Main application: submarine 25
26. 26. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Dispersion Compensation Transmitter Dispersion Compensators Dispersion Shifted Fiber Cable +100 0 -100 -200 -300 -400 -500 CumulativeDispersion(ps/nm) Total Dispersion Controlled Distance from Transmitter (km) No Compensation With Compensation 26
27. 27. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU DCF Source: http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5719 Dispersion-> DCF ->Dispersion longer fiber distance -> attenuation  -> Optical Amplifiers -> noise  -> S/N DCM (Dispersion Compensation Module) . Usually placed at bottom of rack 27
28. 28. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Polarization Mode Dispersion (PMD) • Resulting from different propagation velocities of 2 states of cross polarization of optical signal in fiber • Can’t avoid • Due to – Manufacturing process – Installation/usage (temperature, vibration, bending (DCM) • Both PMD and CD are sensitive at higher bit rates Source: http://www.fiberoptics4sale.com/wordpress/optical-fiber-dispersion/ 28
29. 29. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Combating PMD • Improved fibers • Regeneration – Light signal is detected & converted to an electrical signal that is amplified, reshaped & converted back to an optical signal • Follow manufacturer’s recommended installation techniques for the fiber cable 29
30. 30. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU ITU Wavelength Grid • Standard set of wavelengths to be used in FO communications • ITU-T  grid is based on 191.7 THz + 100 GHz • It is a standard for laser in DWDM systems • Wavelength spacing could be 50GHz, 100GHz, 200GHz, …. 1530.33 nm 1553.86 nm 0.80 nm 195.9 THz 193.0 THz 100 GHz
32. 32. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU How to increase network capacity? Space Division Multiplexing (SDM) • Add more fiber & equipment • Slow Time to Market • Expensive Engineering • Limited Rights of Way • Duct Exhaust Time Division Multiplexing (TDM) • PDH/SDH (STM- 16->STM-64(10G)- >STM-256(40G) • Complexity • Electronics more expensive Wavelength Division Multiplexing (WDM) • Economical, mature & quick • Fast Time to Market 32
33. 33. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU What’s WDM? • A technology that utilizes the properties of refracted light to both combine and separate optical signals based on their wavelengths within the optical spectrum • Different signals with specific wavelength are multiplexed into a fiber for transmission 33
34. 34. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU What’s WDM? , Contd., Gas Station Free Way Petrol Car Freeway : Fiber Petrol Car : Supervisory Signal Gas Station : Optical relay Gray Car : Client Service Colored Car : Service in different channels (wavelength) Driveway : Optical wavelength 34
35. 35. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU TDM Vs. WDM SONET 35 • Takes sync and async signals & multiplexes them to a single higher optical bit rate • 4 STM-1 channels in STM-4 • 4 STM-4 channels in STM-16 • 16 STM-4 channels in STM-64 • E/O or O/E/O conversion • Single wavelength per fiber • Takes multiple optical signals and multiplexes onto a single fiber • No signal format conversion • Multiple wavelengths per fiber
37. 37. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU WDM History • Early WDM (late 80s) – Two widely separated wavelengths (1310, 1550nm) • “Second generation” WDM (early 90s) – Two to eight channels in 1550 nm window – 400+ GHz spacing • DWDM systems (mid 90s) – 16 to 40 channels in 1550 nm window – 100 to 200 GHz spacing • Next generation DWDM systems – 64 to 160 channels in 1550 nm window – 50 and 25 GHz spacing 37
38. 38. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Why WDM? • Capacity upgrade of existing fiber networks (without adding fibers) • Transparency: Each optical channel can carry any transmission format (different asynchronous bit rates, analog or digital) • Scalability: Buy and install equipment for additional demand as needed • Wavelength routing and switching: Wavelength is used as another dimension to time and space 38
39. 39. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU WDM principle elements • Allow traffic to enter and leave the optical network – Transponder • Signal/wavelength converter – Muxponder • Combines several client signals into one line signal • Multiplex wavelengths – Optical multiplexer (MUX) and de-multiplexer • Send wavelengths in different directions – ROADM • Optical Amplifier (Amp) • Supervisory channel • Optical Source 39
40. 40. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Optical Multiplexer Optical De-multiplexer Optical Add/Drop Multiplexer (OADM) Transponder WDM Components 1 2 3 1 2 3 850/1310 15xx 1 2 3 1...n 1...n 40
41. 41. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Optical Amplifier (EDFA) Optical Attenuator Variable Optical Attenuator Dispersion Compensator (DCM / DCU) More WDM Components 41
42. 42. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU System structure OTU1 OTUn OTU2 OTU1 OTUn OTU2 OSCOSCOSC OLA Optical Transponder Unit: Access the client services & convert the wavelength compiled with ITU standard Optical Multiplexer Unit: Multiplex several services with different wavelength into one main path signal OA Optical Amplifier: Amplifies the optical signal Optical Supervisory Channel: Terminate & Re-generation. Not amplification. Optical De-multiplexer Unit: De-multiplex one main path signal into several individual signals Optical Line Amplifier 1 2 n nm nm 1,2..n 1 2 n P A A P A A P A P Active Passive OA A 1,2..n P O M U P O D U 42 P
43. 43. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Loss • Passive => Loss (power reduction) – Ex:- Input power to the MUX 0 dB. Output power from the MUX -6 dB. Therefore the loss is 6 dB • Loss can be due to splicing, distance, bending, aging, connectors 43 Source: http://www.thefoa.org/tech/lossbudg.htm
45. 45. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU OTU- Optical Transponder Unit O OE ENon-color (Not defined by ITU-T) Ex:- 1310 nm short reach SMF 1550 nm long reach SMF 850 nm MMF Can’t use these in WDM without OTU Color (Defined by ITU-T) Ex:- 1: 1550.51 nm 2 :1551.23 nm 45 SMF-Single Mode Fiber MMF-Multi Mode Fiber Optical to Electrical conversion Electrical to Optical conversion Wavelength conversion
46. 46. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Uni Versus Bi-directional WDM WDM systems can be implemented in two different ways Bi -directional  5  6  7  8 Fiber  1  2  3  4 Uni -directional  1  3  5  7 Fiber Fiber  1  3  5  7  2  4  6  8  2  4  6  8 • Uni-directional: wavelengths for one direction travel within one fiber two fibers needed for full-duplex system • Bi-directional: a group of wavelengths for each direction single fiber operation for full-duplex system 46
47. 47. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU WDM network topologies • Point to Point • Ring • Mesh Cost  Complexity  Reliability  47
48. 48. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU CWDM vs. DWDM Source: http://www.cable360.net/tech/strategy/businesscases/30007.html CWDM- Coarse WDM, DWDM-Dense WDM DWDM: smaller transmission window CWDM: larger transmission window 48 Closer wavelength spacing: need to maintain stable wavelengths / frequencies
49. 49. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU CWDM vs. DWDM, cont., Types CWDM DWDM Channel spacing (Grid) 20 nm (fixed) 100 GHz/ 50 GHz/ 25 GHz Band 1311~1611 nm (All bands) C-band: 1529nm~1561nm L-band: 1570nm~1603nm Capacity (max) 18 x 10 Gbps 192 x 10 Gbps Laser Un-cooled Laser Cooled Laser Cost 70% 100% Application 100 km (max) 5000 km 49 Since f  1 / , channel spacing can be denotes as both distance and frequency As CWDM works in all 5 bands, amplification is NOT possible
51. 51. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU SDH/SONET vs. WDM 51 All traffic signals are regenerated and switched, making them available for add and drop Only selected signals (wavelengths) are available for add and drop, the rest are “glassed through”. Source : http://www.transmode.com/en/technologies/wdm • Signals are regenerated at each node- the equivalent uninterrupted “wire” stretches only between 2 nodes • A new power budget is calculated for each hop between 2 adjacent node • Light paths in a WDM network are e2e connections, & should be considered as the equivalents of uninterrupted “wires”, stretching from one point in the network to another while passing one or several nodes • Optical transmission characteristics for a wavelength has to be calculated for the complete distance the light path traverse
52. 52. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Modulation • DAC? – medium/channel is band pass (Ex:- light), and/or – multiple users need to share the medium • Analog signal – Typically sinusoidal • Amplitude->ASK • Frequency->FSK • Phase->PSK • Digital signal – 1 – 0 52 QAM Susceptible to noise
54. 54. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Modulation, cont., 54 21 22 23 24 Phase only Phase & Amplitude (2-PSK) (4-PSK) OOK (ASK) Amplitude only
56. 56. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Comparison of optical modulators Types Direct Electro- Absorption External Mach- Zehnder External Coherent Max. dispersion tolerance (ps/nm) 1200-4000 7200-12800 >12800 40000 Cost moderate expensive Very expensive Very expensive Wavelength stability good better best best 56
57. 57. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU 57 Direct Detection (optical power measuring process) Coherent detection (process is sensitive to the amplitude, frequency and phase (Ex:- 16QAM, 64QAM for 100G and above)
58. 58. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Tx and Rx Optical transmitter • Semiconductor – LED – Laser Optical receiver • Photodetector 58 Source : http://www.transmode.com/en/technologies/wdm Produces a coherent (light of one wavelength with all the light waves being in same phase) light Coherent light is a prerequisite for long reach over fiber
59. 59. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU The Big Leap: 10G to 100G Coherent 59Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014 Hard Decision FEC: for every input and output signal a hard decision is made whether it corresponds to a one or a zero bit Soft Decision FEC: process analog signals, allowing much higher error- correction performance Dual Polarization
60. 60. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Beyond 100G - Enhanced Encoding 60Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
62. 62. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU • Compensates the loss • Any analog signal system has noise. Optical signal is also analog • More Amps-> more accumulated noise (N)->S/N->BIR – Amp keeps Signal (S) constant. • Solution: re-generation (electrical domain: OEO regeneration) • Amplification and regeneration gives unlimited distance, theoretically – Ex:- 1500 km if the link has FEC • Optical Signal to Noise Ration (OSNR) = Ratio of optical signal power to noise power for the receiver 62 Pout = GPinPin G
63. 63. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Amplifier types • EDFA - Erbium Doped Fiber Amplifier – Widely used – Only applicable for wavelengths in the C-band used by DWDM • RFA - Raman Fiber Amplifier – Uses non-linearity effect – Uses high power class 4 laser • Use APC (Angular Physical Contact) connectors instead of PC – Ex:-LC/APC (Lucent Connector), SC/APC, FC/APC – 20 km distance • Need to maintain splice loss <0.1dB within 1st 10 km and <0.2dB within next 10 km – Low noise – Low gain efficiency (10~12 dB) 63
65. 65. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Optical Multiplexer and de- multiplexer • TFF - Thin Film Filter – when no. of channels<16 • AWG - Arrayed Waveguide Grating – when no. of channels>=16 – expensive 65
66. 66. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU TFF Source: http://www.fiberoptics4sale.com/wordpress/what-is-multilayer-dielectric-thin-film-filter/ 0.1 dB loss. Therefore max. of 16 channels Has the lowest power 66
69. 69. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Supervisory technologies • OSC - Optical Supervisory Channel – Often used in backbone systems – Uses OTN (G.709) framing (similar to SDH) – Costly • ESC - Electrical Supervisory Channel – Often used in metropolitan systems – OTU is mandatory at every site • OLA sites don’t have OTU. Therefore can’t mange OLAs with ESC 69
70. 70. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU 70 ADM OADM ROADM function in the traditional SONET/ SDH networks • is a device used in photonic domain under WDM systems for multiplexing and routing different channels of light into or out of a single mode fiber • best solution for a small & static optical network • OADM with remotely reconfigurable optical switches in the middle stage • Enables more automation, reducing the risk for manual errors • best solution for a larger optical network
72. 72. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Key attributes of ROADM Module • Fully Flexible, Remotely Reconfigurable Optical Add Drop • Automatic power equalization on inputs, outputs, adds, drops • Optical Power Monitoring (OPM) of all channels Key benefits of ROADM Module • Elimination of the OEO “Pass-through” tax • Scalable Bandwidth (Start with 1, grow by 1 ) • Single Wavelength Granularity – No stranded bandwidth • Fully Automated Optical Layer 72Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
73. 73. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Static Networks Based on Fixed- Wavelength Filters • Topology and capacity/node determined at time of network design – Traffic projections based upon best estimates at the time – Not always cost effective to “overbuild” the system • Can lead to premature system exhaust – Expected system lifetime: 5-10 yrs – Traffic projections not accurate leading to premature system exhaust • Insufficient ’s available to hot spots • Unlit ’s to cold spots cannot be utilized – Topology is inconsistent for emerging applications • Telephony, SAN, Enterprise, VoD 73 Physical WDM Ring Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
74. 74. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU ROADMs Enable Any-Node-to- Any-Node Topologies • Provision wavelengths independently between nodes • No blocking extends system life to capacity limitation – Relieves need for accurate traffic growth forecasting 74 Physical WDM Ring Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
75. 75. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU ROADM Generations • 1st generation: Wavelengths Blocker based ROADMs – 2 degree nodes only – 100 GHz channel spacing – Add/Drop only – Neither colorless nor directionless • 2nd generation – 2 degree nodes and very limited multi degree functionality – 100 GHz channel spacing – Add/Drop only – Neither colorless nor directionless node support • 3rd generation: WSS 1:N based ROADMs – Multi degree node support – 50 GHz and 100 GHz channel spacing – Colorless and directionless node support • 3rd + generation – Multi degree node support – Flexible channel spacing – Future proof on • Colorless and directionless node support • Contentionless node support 75Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
76. 76. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU 2 degree ROADM 76 No. of inputs Source : http://www.transmode.com/en/technologies/wdm 1 MUX per direction 1 MUX per direction Specific  MUX port
77. 77. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Good features to have on a WSS system 77 • Colorless • Directionless • Contentionless
78. 78. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Colorless 2 degree ROADM 78 Source : http://www.transmode.com/en/technologies/wdm Any  connected to any MUX port 1 MUX per direction 1 MUX per direction
79. 79. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Directionless 2 degree ROADM 79 can be made colorless by combining with traffic units having tunable transceivers Source : http://www.transmode.com/en/technologies/wdm Share MUX between directions
80. 80. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Directionless and contentionless 2 degree ROADM 80 can be made colorless by combining with traffic units having tunable transceivers Source : http://www.transmode.com/en/technologies/wdm 1 MUX per direction Multiples of same  can be add/drop to same MUX
84. 84. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Automatically Switched Optical Network (ASON) • Non-IP network layer control • Alternative/supplement for/to NMS based connection management • Does not change transport plane functionality • Signaling between transport equipment for network discovery • Each network element knows the network topology • Requirements and architecture => ITU-T (G.8080/Y.1304) • Protocols => IETF (GMPLS) • ASON types – Electrical (ODU/OTN switching, a.k.a Layer-1 ASON) • Granular • Fast – Optical (Wavelength SON (WSON), a.k.a Layer-0 ASON) •  switching 84
85. 85. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU 85 Source: http://en.wikipedia.org/wiki/Automatically_switched_optical_network Common control plane simplify network OAM & automatic e2e provisioning
87. 87. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Generalized Multi-Protocol Label Switching (GMPLS) • The optical layer is connection oriented (circuit switched), Light paths are easy to be established • Light paths can be seen as LSPs between ingress and egress OXCs. • Multiprotocol Lambda Switching (MPλS) was defined as a control plane for optical networks • MPLS and MPλS were then unified and called GMPLS (RFC 3945) • Extends MPLS to provide the control plane (signaling and routing) for devises that switch in any of these domains: packet, time, wavelength and fiber • GMPLS starting point is based on the IP view of the transport plane: one physical layer – Fibers are the reference points – Equipment are black boxes identified by switching capabilities – Topology and link state information distributed to all equipment independent of network layer the equipment operates on (“peering”) • GMPLS is a tool box which can be used to support ASON’s view of the transport plane 87
89. 89. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU What is “OTN”? • As per ITU-T, it’s G.709 standard – a.k.a Digital Wrapper (DW) – a.k.a Optical Transport Hierarchy (OTH) standard • OTN could mean; – OTN wrapper capability – OTN switching capability • In the industry/telco field? – OTN – POT (Packet Optical Transport) • packet (MPLS-TP?)+ TDM (SDH/PDH) + WDM + ROADM – Optical Packet Transport layer 89
90. 90. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU OTN aim • Combine the – Benefits of SONET/SDH (OAM&P) • Monitoring a connection e2e over multiple transport segments – Bandwidth expandability of DWDM • Designed to transport both – Packet mode traffic : IP and Ethernet – Legacy SDH/SONET traffic • Includes FEC 90
91. 91. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Main functionality provided by an OTN • Transparent transport of different optical clients • Interconnection of different administrative domains • Optical channel networking and protection • Performance monitoring and alarm supervision • Network management 91
93. 93. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU SONET & SDH multiplexing hierarchies 93 Source : http://www.transmode.com/en/technologies/wdm All the clocks in the SDH/SONET network are perfectly synchronized to a single master clock. This allows lower speed signals to be added/dropped from the SDH/SONET stream without de-multiplexing the entire stream into its individual components
94. 94. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU OTN signal structure and terminology (Ex:-) 94 Carrier Ethernet frame is carried as the payload of an Optical Channel Payload Unit (OPU) Source : http://www.transmode.com/en/technologies/wdm
97. 97. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Pre-OTN WDM Vs. OTN Pre-OTN WDM • simple transport • Bandwidth multiplication by means of WDM transport • Point-to-point application that can transport STM-N/OC- N as a service OTN • networking – solution • Management enabler of WDM network • First transmission technology in which each stakeholder gets its own (ODUk) connection monitoring 97
98. 98. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU OTN switching 98 • Prime advantage: sub-lambda grooming at intermediate sites. • Industry trend(both suppliers and operators): Start WITHOUT OTN switching and go for OTN switching in the future if all the lambdas run out/close to run out (aka Wave-length blocking). • This requires that you select a vendor who's capable of OTN switching but you need NOT purchase OTN switching components (cards) on day one. • You do NOT need OTN switching to achieve mesh protection. What is then required is ASON/GMPLS.
99. 99. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU OTN networking efficiency: virtual wavelengths • Flexible granularity options to maximize services and revenue per wavelength 99 Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
100. 100. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU All-Optical (without digital switching) • “Services over wavelengths” - static • Inefficient • Optical-only switching • No digital switching & reconfiguration • Patch panel & truck-roll re-grooming 100 Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
101. 101. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU WDM + Stand-alone OXC’s: 2 Platform Solution • OXC provides network efficiency • 2 platform solution: space & power • Back-back client connections • Segmented provisioning/protection • No end-end management/automation 101 Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014
102. 102. Anuradha Udunuwara | udunuwara@ieee.org | www.linkedin.com/in/anuradhau | @AnuradhU Converged DWDM & OTN Switching :Collapsing Layers, Simplifying Networks • Converged OTN/WDM switching • Eliminate I/C cost, extra space/power • Eliminates many points of failure • Automated, end-end provisioning • End-to-end service protection 102 Source: 2nd Annual WDM & Next Generation Optical Networking APAC 2014