Optical Networking Technologies 1 Outline Introduction to Fiber

Optical Networking Technologies 1

Outline • Introduction to Fiber Optics • Passive Optical Network (PON) – point-topoint fiber networks, typically to a home or small business • SONET/SDH • DWDM (Long Haul) 2

Optical Transmission electrical signal Optical Fibre Transmission System optical signal Optical Fibre Transmission System electrical signal Advantages of optical transmission: 1. Longer distance (noise resistance and less attenuation) 2. Higher data rate (more bandwidth) 3. Lower cost/bit 3

Optical Networks • Passive Optical Network (PON) – Fiber-to-the-home (FTTH) – Fiber-to-the-curb (FTTC) – Fiber-to-the-premise (FTTP) • Metro Networks (SONET) – Metro access networks – Metro core networks • Transport Networks (DWDM) – Long-haul networks 4

Optical Network Architecture DWDM SONET Long Haul Network Metro Network transport network Metro Network PON Access Network CPE (customer premise) 5

All-Optical Networks • Most optical networks today are EOE (electrical/optical/electrical) • All optical means no electrical component – To transport and switch packets photonically. • Transport: no problem, been doing that for years • Label Switch – Use wavelength to establish an on-demand end-to-end path • Photonic switching: many patents, but how many products? 6

Optical 101 • Wavelength ( ): length of a wave and is measured in nanometers, 10 -9 m (nm) – 400 nm (violet) to 700 nm (red) is visible light – Fiber optics primarily use 850, 1310, & 1550 nm • Frequency (f): measured in Tera. Hertz, 1012 (THz) • Speed of light = 3× 108 m/sec 7

Optical Spectrum l IR UV 125 GHz/nm Visible 850 nm 1550 nm 1310 nm • Light Bandwidth – Ultraviolet (UV) – Visible – Infrared (IR) • Communication wavelengths – 850, 1310, 1550 nm 1550 nm 193, 548. 4 GHz 1551 nm 193, 424. 6 GHz 1 nm 125 GHz – Low-loss wavelengths 8

Optical Fiber • An optical fiber is made of three sections: – The core carries the light signals – The cladding keeps the light in the core – The coating protects the glass Core Cladding Coating 9

Optical Fiber (cont. ) • Single-mode fiber – Carries light pulses by laser along single path • Multimode fiber – Many pulses of light generated by LED travel at different angles SM: core=8. 3 cladding=125 µm MM: core=50 or 62. 5 cladding=125 µm 10

Bending of light ray 7. 11

Figure 7. 12 Propagation modes 7. 12

Figure 7. 13 Modes 7. 13

Figure 7. 14 Fiber construction 7. 14

Figure 7. 15 Fiber-optic cable connectors 7. 15

Figure 7. 16 Optical fiber performance 7. 16 Note: loss is relatively flat

Fiber Installation Support cable every 3 feet for indoor cable (5 feet for outdoor) Don’t squeeze support straps too tight. Pull cables by hand, no jerking, even hand pressure. Avoid splices. Make sure the fiber is dark when working with it. Broken pieces of fiber VERY DANGEROUS!! Do not ingest! 7. 17

Optical Transmission Effects Attenuation Dispersion & Nonlinearity Distortion Transmitted Data Waveform After 1000 Km 18

Optical Transmission Effects Attenuation: Loss of transmission power due to long distance Dispersion and Nonlinearities: Erodes clarity with distance and speed Distortion due to signal detection and recovery 19

Transmission Degradation Ingress Signal Egress Signal Loss of Energy Optical Amplifier Shape Distortion Dispersion Compensation Unit (DCU) Loss of Timing (Jitter) t Phase Variation t Optical-Electrical-Optical (OEO) cross-connect 20

Passive Optical Network (PON) • Standard: ITU-T G. 983 • PON is used primarily in two markets: residential and business for very high speed network access. • Passive: no electricity to power or maintain the transmission facility. – PON is very active in sending and receiving optical signals • The active parts are at both end points. – Splitter could be used, but is passive 21

Passive Optical Network (PON) OLT: Optical Line Terminal ONT: Optical Network Terminal Splitter (1: 32) 22

PON – many flavors • ATM-based PON (APON) – The first Passive optical network standard, primarily for business applications • Broadband PON (BPON) – the original PON standard (1995). It used ATM as the bearer protocol, and operated at 155 Mbps. It was later enhanced to 622 Mbps. – ITU-T G. 983 • Ethernet PON (EPON) – standard from IEEE Ethernet for the First Mile (EFM) group. It focuses on standardizing a 1. 25 Gb/s symmetrical system for Ethernet transport only – IEEE 802. 3 ah (1. 25 G) – IEEE 802. 3 av (10 G EPON) • Gigabit PON (GPON) – offer high bit rate while enabling transport of multiple services, specifically data (IP/Ethernet) and voice (TDM) in their native formats, at an extremely high efficiency – ITU-T G. 984 23

x. PON Comparison BPON EPON GPON Standard ITU-T G. 983 IEEE 803. 2 ah ITU-T G. 984 Bandwidth Down: 622 M Up: 155 M Symmetric: 1. 25 G Down: 2. 5 G Up: 2. 5 G Downstream λ 1490 &1550 1490 & 1550 Upstream λ 1310 Transmission ATM Ethernet ATM, TDM, Ethernet 24

PON Case Study (BPON) Optical Line Terminal (OLT) (Central Office) Packet Core (IPo. ATM) Optical Network Terminal (ONT) (customer premise) Two Ethernet ports One T 1/E 1 port Optical transport: 622 M bps T 1/E 1 802. 3 CES RFC 2684 AAL 1 AAL 5 SAR/CS ATM TDM Core (PSTN) PON (G. 983) 25

GPON 26

EPON Evolution 27

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EPON Downstream 31

EPON Upstream 32

SONET in Metro Network Long Haul (DWDM) Network Core Router Metro SONET Ring Voice Switch Access Ring T 1 PBX 33

IP Over SONET is designed for TDM traffic, and today’s need is packet (IP) traffic. Is there a better way to carry packet traffic over SONET? T 1 DS 3 OC-3 IP IP ? ? SONET TDM Traffic SONET 802. 3 RFC 2684 IP IP AAL 5 PPP 802. 3 ATM RFC 1619 GFP SONET GFP: Generic Frame Procedure RFC 2684: Encapsulate IP packet over ATM RFC 1619: Encapsulate PPP over SONET 34

ATM over SONET (STS-3 c) Cell 1 Cell 2 Cell 3 260 columns (octets) Cell 1 Cell 2 Cell 3 OH 9 rows STS-3 c Envelope 35

PPP over SONET • RFC 1619 (1994) • The basic rate for PPP over SONET is STS-3 c at 155. 520 Mbps. • The available information bandwidth is 149. 760 Mbps, which is the STS-3 c envelope with section, line and path overhead removed. • Lower signal rates use the Virtual Tributary (VT) mechanism of SONET. 36

PPP over SONET (STS-3 c) PPP Frame 1 (HDLC) PPP Frame 2 (HDLC) PPP Frame 3 (HDLC) 260 columns (octets) PPP Frame 1 a PPP Frame 2 a PPP Frame 1 b PPP Frame 2 b POH PPP Frame 2 c 2 d Path overhead 9 rows PPP Frame 3 STS-3 c Envelope 37

Dense Wave Division Multiplexing (DWDM) Ref: Cisco DWDM Primer 38

Continue Demands for More Bandwidth Same bit rate, more fibers More Fibers Slow Time to Market Expensive Engineering Limited Rights of Way Duct Exhaust W D M Faster Electronics (TDM) Same fiber & bit rate, more ls Fiber Compatibility Fiber Capacity Release Fast Time to Market Lower Cost of Ownership Utilizes existing TDM Equipment Higher bit rate, same fiber Electronics more expensive 39

TDM vs. WDM • Time division multiplexing –Single wavelength per fiber –Multiple channels per fiber – 4 OC-3 channels in OC-12 – 4 OC-12 channels in OC-48 – 16 OC-3 channels in OC-48 • Wave division multiplexing –Multiple wavelengths per fiber – 4, 16, 32, 64 wavelengths per fiber –Multiple channels per wavelength Channel 1 Channel n Single Fiber (One Wavelength) l 1 l 2 Single Fiber (Multiple Wavelengths) ln 40

TDM vs. WDM • TDM (SONET/SDH) –Take sync and async signals and multiplex them to a single higher optical bit rate –E/O or O/E/O conversion DS-1 DS-3 OC-1 OC-3 OC-12 OC-48 SONET ADM Fiber • WDM –Take multiple optical signals and multiplex them OC-12 c OC-48 c onto a single fiber OC-192 c –No signal format conversion DWDM OADM Fiber 41

FDM vs. WDM vs. DWDM • Is WDM also a Frequency Division Multiplexing (FDM) which has been widely available for many years? • Short Answer: Yes. There is no difference between Wavelength Division and Frequency Division. In general, FDM is used in the context of Radio Frequency (MHz – GHz) while WDM is used in the context of light ( THz) • WDM: The original standard requires 100 GHz spacing to prevent signals interference. • Dense WDM (DWDM): support multiplexing of up to 160 wavelengths of 10 G/wavelength with 25 GHz spacing – The use of sub 100 GHz for spacing is called Dense WDM. – Some vendors even propose to use 12. 5 GHz spacing, and it would multiplex up to 320 wavelengths Spectrum A spacing Spectrum B 42

DWDM Economy Conventional TDM Transmission— 10 Gbps 40 km 40 km 40 km 1310 1310 TERM 1310 1310 1310 1310 RPTR RPTR RPTR RPTR TERM 1310 1310 RPTR RPTR TERM RPTR RPTR OC-48 DWDM Transmission— 10 Gbps OA 120 km OA 4 Fiber Pairs 32 Regenerators OA 120 km OA OC-48 1 Fiber Pair 4 Optical Amplifiers 43

Optical Transmission Bands Band “New Band” S-Band C-Band L-Band U-Band Wavelength (nm) 1360 1460 1530 1565 1625 – – – 1460 1530 1565 1625 1675 44

DWDM: How does it work? TDM: multiple services onto a single wavelength TDM DWDM TDM Single pair of fiber strand Multiple wave lengths 45

DWDM Network MUX DEMUX 46

DWDM Network Components l 1 850/1310 15 xx l 2 l 1. . . n l 3 Transponder Optical λ => DWDM λ Usually do O-E-O Optical Multiplexer l 1 l 2 l 1. . . n l 3 Optical De-multiplexer Optical Add/Drop Multiplexer (OADM) 47

Optical Amplifier (OA) Pin gain Pout n EDFA (Erbium Doped Fiber Amplifier) amplifier n Separate amplifiers for C-band L-band 48

Optical ADM (OADM) • OADM is similar in many respects to SONET ADM, except that only optical wavelengths are added and dropped, and there is no conversion of the signal from optical to electrical. Q: there is no framing of DWDM, so how do we add/drop/pass light? A: λ It is based on λ and λ only. 49

Cisco ONS 15800 • • TO build a long haul network Up to 64 channels (i. e. , wavelengths) OC-12, OC-48, OC-192 up to 500 km LEM: Line Extension Module http: //www. cisco. com/warp/public/cc/pd/si/on 15800 s/prodlit/ossri_ds. pdf 50

DWDM Network (point-to-point) OLA: Optical Line Amplifier 51

DWDM Network Add-and-Drop Note: this is a linear topology, and not a ring topology. Chicago λ 1: to Pittsburg λ 2: to New York Pittsburg λ 1: drop λ 2: pass New York 52

SONET and DWDM terminal Long Hall SONET Chicago SONET DWDM SONET New York OC-3 IP IP PPP SONET 53

IP over DWDM ? ? ? IP IP IP DWDM terminal ? ? ? DWDM terminal DWDM Note: There is no protocol called “IP over DWDM” or “PPP over DWDM”. However, there are many publications on “IP over DWDM” and they all require a layer-2 protocol which provides the framing to encapsulate IP packets. (see the previous slide) 54

Summary • • Optical Fiber Network – the market needs Access Network – Passive Optical Network (PON) • Metro Network – SONET/SDH • Transport Network (Long-Haul) – DWDM • DWDM can be applied to metro and access networks as well, but unlikely for its high cost. • Optical network is a layer-1 technology, and IP is a layer-3 protocol. There must be a layer-2 protocol to encapsulate IP packets to layer-2 framing before it goes to the optical layer – ATM (via RFC 2684) – SONET (via PPP) – Ethernet (via GFP) 55