CS 268: Optical Networks

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Big Picture CS 8: Optical Networks Data Center SONT SONT Ion Stoica April, 004 SONT SONT (Based in part on slides from d Bortolini (Network

Division Multiplexing () Synchronous Optical Network (SONT) Transmitted data waveform Waveform after 000 km Fiber Attenuation Dispersion 0. 0. 0.4 0.

- Wider window - Optical amplifiers Dispersion causes the pulse to spread as it travels along the fiber Chromatic dispersion - ight propagation

1 Big Picture CS 8: Optical Networks Data Center SONT SONT Ion Stoica April, 004 SONT SONT (Based in part on slides from d Bortolini (Network Photonics), ing Huang (UC Berkeley), Shivkumar Kalyanaraman (RPI), arry McAdams (Cisco)) Access Metro ong Haul Metro Access Dense Wavelength Division Multiplexing () Synchronous Optical Network (SONT) Transmitted data waveform Waveform after 000 km Fiber Attenuation Dispersion window 0 window Telecommunications industry uses two windows: 0 & 0 nm 0 window is preferred for long-haul applications - ess attenuation - Wider window - Optical amplifiers Dispersion causes the pulse to spread as it travels along the fiber Chromatic dispersion - ight propagation in material varies with the wavelength - Degradation scales as (data-rate) 0. λ Wavelength (Figure from

2 Dispersion Modal dispersion - Only for fiber that carry multiple light rays (modes) - Different modes travel at different speeds - Multimodal fiber used only for short distances Dense Wavelength Division Multiplexing () Synchronous Optical Network (SONT) 8 System Design.488 Gbps () km 0/0 nm Regenerator - R (Reamplify, Reshape and Retime) 0 km.488 Gbps () 4 Optical Amplifiers (OA) 0- nm ramge 0/0 nm *.488 Gbps = 40 Gbps uncorrelated vawelengths stabilized, correlated vawelengts 9 OA amplifies all λs System Design All-Optical Switching nm Rx aser 0 4 xternal Modulator Optical Combiner xx nm Amplify xx nm Rx Filter Reamplify Reshape Retime Tx nm λ! "# $ % # %# &%' )(&! * & +,(&% *+ (! ' '(% &- (&% Fibers in Demux Demux All-optical OXC Mux Mux Fibers out

3 -D MMS Optical Switch MMS: Microelectromechanical systems -Dimensional array of micromirrors - mirror per wavelength Digital control; no motors -input Input & -outoput Output fiber illustration Wavelength with four wavelengths -D MMS array Dispersive lement Micro-mirror Array Input Fiber Output Fiber Output Fiber Digital Mirror Control lectronics -D MMS with dispersive optics - Dispersive element separates the λ s from inputs - MMS independently switches each λ - Dispersive element recombines the switched λ s into outputs 4 Optical Switch Optical Add-Drop Multiplexer in in add add 4 add add add add add M add Tunable lasers out out Add-drop one λ ach λ is associated with a fixed add/drop port Used to implement ring topologies in out 4 in 4 out in out λ in in out out DMUX λ MUX Wavelengthmultiplexer N in drop drop 4 drop drop drop drop drop M drop N out N x M four-port optical matrix switch SONT Dense Wavelength Division Multiplexing () Synchronous Optical Network (SONT) ncode bit streams into optical signals propagated over optical fiber Uses Time Division Multiplexing (TDM) for carrying many signals of different capacities - A bit-way implementation providing end-to-end transport of bit streams - All clocks in the network are locked to a common master clock - Multiplexing done by byte interleaving 8

4 > Synchronous Transport Signal (STS) ncoding First two bytes of each frame contain a special bit pattern that allows to determine where the frame starts Receiver looks for the special bit pattern every 80 bytes - Size of frame = 9x90 = 80 bytes overhead Data (payload) Overhead bytes are encoded using Non-Return to Zero - high signal ; low signal 0 To avoid long sequences of 0 s or s the payload is XOR-ed with a special -bit patter with many transitions from to 0 - Duration of a frame is µsec (.84 Mbps for STS-) 9 rows Synchronous Payload nvelope (SP) 90 columns SONT STS- Frame 9 0 SONT Overhead Processing Three layers of overhead - Path overhead (POH): end-to-end transport - ine overhead (OH): mux-to-mux transport - Section overhead (SOH): adjacent network element "! STS- Frame Format MUX Section Section Section Section Regenerator ine Intermediate Multiplexer ( or DCS) Path Regenerator ine DMUX # $ % $ & (')" Two-dimensional: 9*80 = 80 bytes Time Frame: µsec Rate: 80*8 bit/ µsec =.84 Mbps For STS- only the number of columns changes (*80 = 0) STS- Headers Section Overhead (SOH) Section Overhead (SOH)! " ine Overhead (OH) * +, -. Path Overhead (POH): Floating; can begin anywhere First lines in the header Main functions - Framing (A, A) - Monitor performance - ocal orderwire (): select repeater/terminal within communication complex - Proprietary OAM (Operation, Administration, and Maintenance) (F) /0 4 F0 F:GH I J SOH > C D 4 0 N P 8:9; =< ABA M+N OP.N K QSR T U=V.W ^ B 8 B 4 4

$switch (K, K) Switchover in case of failure - ine maintenance 0 H VW..D C < :XY X[Z.\] :XY X[Z.\] :XY X[Z.\] A OH H VW H VW / 0 /H /H :< 9 M+N O=P.$

5 9 A D K V $ ine Overhead (OH) ast lines in the header Main functions - ocating payload (SP) in the frame (H, H) - Muxing and concatenating signals - Performance monitoring - Automatic protection switch (K, K) Switchover in case of failure - ine maintenance 0 H VW..D C < :XY X[Z.\] :XY X[Z.\] :XY X[Z.\] A OH H VW H VW / 0 /H /H :< 9 M+N O=P.N K Q R N P st column in SP Main functions - Info about SP content - Performance monitoring - Path status - Path trace SP can start anywhere in the current frame and span the next one - Avoids buffer management complexity & artificial delays st STS- Path Overhead (POH) nd STS- P O H SP 9 rows BN > X P ^ D C < Z AR X! P#" X=Y %[AY XY & '#( P.N ) D =O.R X=Y ^ $N \QY $N \QY BX#=OP] B 8 B STS-N Frame Format STS-N: Generic Frame Format d Te F#f V.U gwhi j k lm Un e G: o p ok q j##r I 0 4 W q l VU *,+;-/.+,0 *,+ -/.+,0 4>;8:9 -<4;0= 4 4IBD#4 8 4CBD4 8 49;F 4 G 49 F 4;G JKJ JKJ MM NO 00 * +;PTQRS94 + PQ>RS9#4 UaVSXY UWVSXZY N [ \,]_^` \,]_^>`.;0. 0 bb P+H P+, D 0 D;0 +F 4 8c,49 G +F 4 8c,49;G s#t vw>xy sut vw>xy z{ z{ } ~ ~ ƒi m x{ } ~ ~ ˆ m x{ } ~ ~ Š Š ˆ ˆ ˆ ˆ m x{ } ~ ~ ƒ ƒ x{ } ~ ~ Œ Œ Œ Œ x{ Multiple frame streams, w/ independent payload pointers Note: header columns also interleaved STS- STS-N 8 STS-Nc Frame Format Practical SONT Architecture d e F#f VU gwhi j k lm Un Transport Overhead: SOH+OH *,+HD;P94 D;9#4 G-<+,GH4 = *,+HD;P9#4 D 94;G>-<+,G,4 = JJ 9;-<4>c;49HG,4 8S0#u8 ;P H84I9,D;G>G;99<8:94;0m <4>c;49,G,4 80# 8 ;P u,84i9hd;gg 9#9Ž8 9#4 0m9;0 J;KHJ MM V V V + 9H + 9, ;c;49 G 4 8 c;49 G;4 8 `` AA 40 ;04;G 40 ;04 G 8:0u 8 0#m N N < ;+, < ;+H D K K +Ž ; m +< m JJ D;, D; H 4> ;9 AA + 9;G +;9 G BD<RS4 0u š BD<R4;0# š J J,œ Add-Drop Multiplexer DCS Digital Crossconnect Current IP over SONT technologies use concatenated mode: OC-c ( Mbps) to OC-9c (0 Gbps) rates a.k.a super-rate payloads 9 0

6 _ Protection Technique Classification + Protection Restoration techniques can protect the network against: - ink failures Fiber-cables cuts and line devices failures (amplifers) - quipment failures OXCs, s, electro-optical interface. Protection can be implemented - In the optical channel sublayer (path protection) - In the optical multiplex sublayer (line protection) Different protection techniques are used for - Ring networks - Mesh networks Traffic is sent over two parallel paths, and the destination selects a better one In case of failure, the destination switch onto the other path Pros: simple for implementation and fast restoration Cons: waste of bandwidth : Protection : Ring Protection ach channel on one ring is protected by one channel on the other ring When faults loop around During normal operation, no traffic or low priority traffic is sent across the backup path In case failure both the source and destination switch onto the protection path Pros: better network utilization Cons: required signaling overhead, slower restoration 4 Protection in Ring Network Protection in Mesh Networks Network planning and survivability design - Disjoint path idea: service working route and its backup route are topologically diverse. - ightpaths of a logical topology can withstand physical link failures. P(QR ST UVWXY Z (Unidirectional Path Switched Ring)! "$#%%&&(' ")*,+ -.' / ' #+ + %0#))' )*# / -." " / - %." / ' #.-+ + %& (Bidirectional ine Switched Ring) :; :<=> >@BA*C DFG H*I&D.JIC H! "!K( / ' -.-. / #."-.' -.")M N #.O*' "9) 4&. + -'8 " / ' -*+ + % ' "9) [X\S]^8WXY Z

ine Protection. :N Protection Backup fibers are used for protection of multiple links Assume independent failure and handle single failure. The capacity reserved for protection is greatly reduced.

7 Path Protection / ine Protection Shared Protection Normal Operation Path Switching: restoration is handled by the source and the destination. ine Switching: restoration is handled restoration by is the handled nodes by adjacent the nodes to adjacent the failure. to the Span failure. Protection: if additional fiber is available. ine Protection. :N Protection Backup fibers are used for protection of multiple links Assume independent failure and handle single failure. The capacity reserved for protection is greatly reduced. Normal Operation In Case of Failure 8 Dense Wavelength Division Multiplexing () Synchronous Optical Network (SONT) GFP provides a generic mechanism to adapt traffic from higher-layer client signals over an octet synchronous transport network (e.g., SONT) thernet IP/PPP Other Client Signals GFP Client Specific Aspects (Payload Dependent) GFP Common Aspects (Payload Independent) SONT/SDH VC-n Path Other octetsynchronous paths OTN ODUk Path 9 40 Frame-mapped - Need to know the client protocol - Associate a length to each higher level frame - fficient: eliminate the need for byte stuffing or for block encoding (e.g., 8B/0B) Transparent - No need to know the client protocol - ess efficient; can transmit signal even when the client is idle 4

Introduction To Optical Networks Optical Networks: A Practical Perspective

Introduction To Optical Networks Optical Networks: A Practical Perspective Galen Sasaki Galen Sasaki University of Hawaii 1 Galen Sasaki University of Hawaii 2 Galen Sasaki University of Hawaii 3 Telecommunications