RCL FiberOptic Networks Xavier Fernando Ryerson Communications Lab

RCL Fiber-Optic Networks Xavier Fernando Ryerson Communications Lab

OSI – 7 Layer Model This Course RCL

Network Categories RCL Optical Networks are categorized in multiple ways: • All Optical (or Passive Optical) Networks Vs Optical/Electrical/Optical Networks • Based on service area – Long haul, metropolitan and access network – Wide area (WAN), metropolitan area (MAN) or local area network (LAN) • Depending on the Protocol – SONET, Ethernet, ATM, IP • Number of wavelengths – single wavelength, CWDM or DWDM

Long/Metro & Access Networks Long Haul Network RCL

RCL Global Network Hierarchy

Different Network Specs RCL Who Uses it? Span (km) Bit Rate (bps) Multiplexing Fiber Laser Receiver Core/ Long. Haul Phone Company, Gov’t(s) ~103 ~1011 (100’s of Gbps) DWDM/ TDM SMF/ DCF EML/ DFB APD Metro/ Regional Phone Company, Big Business ~102 ~1010 (10’s of Gbps) DWDM/C WDM/TD M SMF/ LWPF DFB APD/ PIN Access/ Local. Loop Small Business, Consumer ~109 (56 kbps 1 Gbps) TDM/ SCM/ SMF/ MMF DFB/ FP PIN Core - Combination of switching centers and transmission systems connecting switching centers. Access that part of the network which connects subscribers to their immediate service providers LWPF : Low-Water-Peak Fiber, DCF : Dispersion Compensating Fiber, EML : Externally modulated (DFB) laser

RCL Local Area / Access Networks Local-area networks • Interconnection on number of local terminals • Main technologies: Ethernet, Fast Ethernet, Gigabit Ethernet (better for multiple access) • Usually passive star or bus networks Access networks • The first (or last) network segment between customer premises and a WAN or MAN – Usually owned by a Local Exchange Carrier • PON is getting popular • Fiber-copper technologies: HFC (fiber-coaxial cable) or DSL (fiber-twisted pair) • Fiber-wireless and free-space optics are also used

RCL Metropolitan-area/regional-area networks • A MAN or RAN covers a North American metropolitan area, or a small to medium-sized country in Europe or Asia • Optical ring/mesh topologies with adequate backup and protection • Main technologies: SONET, ATM, Gigabit & 10 Gigabit Ethernet, DWDM • Non-optical technologies: T 1, T 3, Frame Relay • Several LANs could be connected to MAN

Wide-Area Networks (WAN) • Long haul inter-city connections • Either government-regulated or in the public network environment – WANS originated in telephony • Main technologies: SONET/SDH, ATM, WDM – Voice circuits vs. data packets – Non-optical technologies: T 1(1. 544 Mb/s)/E 1(2. 048 Mb/s), DS-3 (44. 736 Mb/s ), Frame Relay – Standards bodies include ITU-T, IETF, ATM Forum, Frame Relay Forum, IEEE RCL

RCL Fiber in the Access End Fiber increasingly reaches the user

RCL PON PASSIVE OPTICAL NETWORKS

Passive Optical Networks RCL • There is no O/E conversion in between the transmitter and the receiver (one continuous light path) • Power budget and rise time calculations has to be done from end-to-end depending on which Tx/Rx pair communicates • Star, bus, ring, mesh, tree topologies • PON Access Networks are deployed widely The PON will still need higher layer protocols (Ethernet/IP etc. ) to complete the service

RCL Passive Optical Network (PON) Topologies BUS RING STAR

Network Elements of PON RCL • Passive Power Coupler/Splitter: Number of input/output ports and the power is split in different ratios. – Ex: 2 X 2 3 -d. B coupler; 80/20 coupler • Star Coupler: Splits the incoming power into number of outputs in a star network • Add/Drop Bus Coupler: Add or drop light wave to/from an optical bus • All Optical Switch: Divert the incoming light wave into a particular output

Fig. 10 -4: Fused-fiber coupler / Directional coupler • P 3, P 4 extremely low ( -70 d. B below Po) • Coupling / Splitting Ratio = P 2/(P 1+P 2) • If P 1=P 2 It is called 3 -d. B coupler RCL

Definitions Try Ex. 10. 2 RCL

Star Coupler RCL • Incoming total power is equally split between N outputs • Usually bidirectional • Splitting Loss = 10 Log N • Excess Loss = 10 Log (Total Pin/Total Pout)

Star Network RCL Power Budget: Ps-Pr = 2 lc + α(L 1+L 2) + Excess Loss + 10 Log N + System Margin Worst case power budget need to be satisfied

RCL Linear bus topology Ex. 12. 1

Add-Drop Bus-Coupler Losses Connector loss (Lc) = 10 Log (1 -Fc) Tap loss (Ltap) = -10 Log (CT) Throughput loss (Lth) = -20 Log (1 -CT) Intrinsic loss (Li) = -10 Log (1 -Fi) RCL

Star, Tree & Bus Networks RCL • Tree networks are widely deployed in the access front • Tree couplers are similar to star couplers (expansion in only one direction; no splitting in the uplink) • Bus networks are widely used in LANs • Ring networks (folded buses with protection) are widely used in MAN • Designing ring & bus networks are similar

Linear Bus versus Star Network RCL • The loss linearly increases with N in bus (ring) connections while it is almost constant in start (tree) networks (Log(N))

RCL Synchronous Optical Network SONET

Brief History RCL • Early (copper) digital networks were asynchronous with individual clocks resulting in high bit errors and non-scalable multiplexing • Fiber technology made highly Synchronous Optical Networks (SONET) possible. • SONET standardized line rates, coding schemes, bit-rate hierarchies and maintenance functionality

Synchronous Optical Networks RCL • SONET is the TDM optical network standard for North America (called SDH in the rest of the world) • De-facto standard for fiber backhaul networks • OC-1 consists of 810 bytes over 125 us; OC-n consists of 810 n bytes over 125 us • Linear multiplexing and de-multiplexing is possible with Add-Drop-Multiplexers

RCL SONET/SDH Bandwidths SONET Optical Carrier Level SONET Frame Format SDH level and Frame Payload bandwidth Format (kbps) Line Rate (kbps) OC-1 STS-1 STM-0 50, 112 51, 840 OC-3 STS-3 STM-1 150, 336 155, 520 OC-12 STS-12 STM-4 601, 344 622, 080 OC-24 STS-24 – 1, 202, 688 1, 244, 160 OC-48 STS-48 STM-16 2, 405, 376 2, 488, 320 OC-192 STS-192 STM-64 9, 621, 504 9, 953, 280 OC-768 STS-768 STM-256 38, 486, 016 39, 813, 120 OC-3072 STS-3072 STM-1024 153, 944, 064 159, 252, 480

Synchronous Optical Networks • SONET is the TDM optical network standard for North America (It is called SDH in the rest of the world) • We focus on the physical layer • STS-1, Synchronous Transport Signal consists of 810 bytes over 125 us • 27 bytes carry overhead information • Remaining 783 bytes: Synchronous Payload Envelope RCL

SONET/SDH Bit Rates SONET Bit Rate (Mbps) SDH OC-1 51. 84 - OC-3 155. 52 STM-1 OC-12 622. 08 STM-4 OC-24 1244. 16 STM-8 OC-48 2488. 32 STM-16 OC-96 4976. 64 STM-32 OC-192 9953. 28 STM-64 RCL

Digital Transmission Hierarchy (T-Standards) DS 3 DS 2 DS 1 Predominant before optical era Additional framing bits stuffed at each level to achieve synchronization Not possible to directly add/drop sub-channels RCL

RCL Fig. 12 -5: Basic STS-1 SONET frame

RCL Fig. 12 -6: Basic STS-N SONET frame STS-N signal has a bit rate equal to N times 51. 84 Mb/s Ex: STS-3 155. 52 Mb/s

RCL

RCL SONET Add Drop Multiplexers ADM is a fully synchronous, byte oriented device, that can be used add/drop OC subchannels within an OC-N signal Ex: OC-3 and OC-12 signals can be individually added/dropped from an OC-48 carrier

RCL SONET/SDH Rings • SONET/SDH are usually configured in ring architecture to create loop diversity by self healing • 2 or 4 fiber between nodes • Unidirectional/bidirectional traffic flow • Protection via line switching (entire OC-N channel is moved) or path switching (sub channel is moved)

2 -Fiber Unidirectional Path Switched Ring RCL Node 1 -2 OC-3 Node 2 -4; OC-3 Ex: Total capacity OC-12 may be divided to four OC-3 streams

2 -Fiber UPSR • Rx compares the signals received via the primary and protection paths and picks the best one • Constant protection and automatic switching RCL

All secondary fiber left for protection 4 -Fiber Bi-directional Line Switched Ring (BLSR) RCL Node 1 3; 1 p, 2 p 3 1; 7 p, 8 p

BLSR Fiber Fault Reconfiguration In case of failure, the secondary fibers between only the affected nodes (3 & 4) are used, the other links remain unaffected RCL

RCL BLSR Node Fault Reconfiguration If both primary and secondary are cut, still the connection is not lost, but both the primary and secondary fibers of the entire ring is occupied

RCL Generic SONET network City-wide Large National Backbone Local Area Versatile SONET equipment are available that support wide range of configurations, bit rates and protection schemes

RCL DO THE REST

Network Terminologies RCL

Some Terms RCL Topology – logical manner in which nodes linked Switching – transfer of information from source to destination via series of intermediate nodes; Circuit Switching – Virtual circuit established Packet Switching – Individual packets are directed Switch – is the intermediate node that stream the incoming information to the appropriate output Routing – selection of such a suitable path Router – translates the information from one network to another when two different protocol

The Optical Layer The OL is a wavelengt h based concept lies just above the physical layer RCL

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RCL Optical Cross Connects

WDM Networks RCL • Single fiber transmits multiple wavelengths WDM Networks • One entire wavelength (with all the data) can be switched/routed • This adds another dimension; the Optical Layer • Wavelength converters/cross connectors; all optical networks • Note protocol independence

RCL WDM Networks • Broadcast and Select: employs passive optical stars or buses for local networks applications – Single hop networks – Multi hop networks • Wavelength Routing: employs advanced wavelength routing techniques – Enable wavelength reuse – Increases capacity

WDM P-P Link Several OC-192 signals can be carried, each by one wavelength RCL

RCL Single hop broadcast and select WDM Star Bus • Each Tx transmits at a different fixed wavelength • Each receiver receives all the wavelengths, but selects (decodes) only the desired wavelength • Multicast or broadcast services are supported • Dynamic coordination (tunable filters) is required

RCL A Single-hop Multicast WDM Network

RCL Multi-hop Architectur e Four node broadcast and select multihop network Each node transmits at fixed set of wavelengths and receive fixed set of wavelengths Multiple hops required depending on destination Ex. Node 1 to Node 2: N 1 N 3 ( 1), N 3 N 2 ( 6) No tunable filters required but throughput is less

RCL Fig. 12 -17: Data packet In multihop networks, the source and destination information is embedded in the header These packets may travel asynchronously (Ex. ATM)

Shuffle Net is one of several possible topologies in multihop networks N = (# of nodes) X ( per node) Max. # of hops = 2(#of-columns) – 1 (-) Large # of ’s (-) High splitting loss RCL A two column shuffle net Ex: Max. 2 X 2 - 1= 3 hops

RCL Wavelength Routing • The limitation is overcome by: – reuse, – routing and – conversion • As long as the logical paths between nodes do not overlap they can use the same

12 X 12 Optical Cross-Connect (OXC) Architecture This uses space switching RCL

RCL Optical Cross Connects (OXC) • Works on the optical domain • Can route high capacity wavelengths • Space switches are controlled electronically • Incoming wavelengths are routed either to desired output (ports 1 -8) or dropped (912) • What happens when both incoming fibers have a same wavelength? (contention) • Try Ex. 12. 5

RCL Ex: 12. 5: 4 X 4 Optical crossconnect Wavelength switches are electronically configured Wavelength conversion to avoid contention