Optical Networking Technologies 1

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

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

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

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, m (nm) – 400nm (violet) to 700nm (red) is visible light – Fiber optics primarily use 850, 1310, & 1550nm Frequency (f): measured in TeraHertz, (THz) Speed of light = 3×10 8 m/sec 7

Optical Spectrum Light – Ultraviolet (UV) – Visible – Infrared (IR) Communication wavelengths – 850, 1310, 1550 nm – Low-loss wavelengths 1550nm193,548.4GHz 1551nm193,424.6GHz 1nm125 GHz 8 UV IR Visible 850 nm 1310 nm 1550 nm 125 GHz/nm Bandwidth

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 9 Cladding Core Coating

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 10 SM: core=8.3 cladding=125 µm MM: core=50 or 62.5 cladding=125 µm

7.11 Bending of light ray

7.12 Figure 7.12 Propagation modes

7.13 Figure 7.13 Modes

7.14 Figure 7.14 Fiber construction

7.15 Figure 7.15 Fiber-optic cable connectors

7.16 Figure 7.16 Optical fiber performance Note: loss is relatively flat

7.17 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!

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

Optical Transmission Effects 19 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

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

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

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 155Mbps. It was later enhanced to 622Mbps. – 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 802.3ah (1.25G) – IEEE 802.3av (10G 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

xPON Comparison BPONEPONGPON StandardITU-T G.983IEEE 803.2ahITU-T G.984 BandwidthDown: 622M Up: 155M Symmetric: 1.25G Down: 2.5G Up: 2.5G Downstream λ 1490 & & 1550 Upstream λ 1310 TransmissionATMEthernetATM, TDM, Ethernet 24

PON Case Study (BPON) 25 Two Ethernet ports One T1/E1 port Optical transport: 622M bps PON (G.983) ATM AAL1AAL5 CES T1/E1 RFC Optical Network Terminal (ONT) (customer premise) Optical Line Terminal (OLT) (Central Office) Packet Core (IPoATM) TDM Core (PSTN) SAR/CS

GPON 26

27 EPON Evolution

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EPON Downstream 31

EPON Upstream 32

SONET in Metro Network 33 Long Haul (DWDM) Network Metro SONET Ring Access Ring Voice Switch PBX Core Router T1

IP Over SONET 34 SONET IP ???? SONET IP ATM AAL5 RFC SONET IP PPP SONET T1 DS3 OC-3 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? SONET GFP IP GFP: Generic Frame Procedure TDM Traffic RFC1619 RFC 2684: Encapsulate IP packet over ATM RFC 1619: Encapsulate PPP over SONET

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

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

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

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

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

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 40 Single Fiber (One Wavelength) Channel 1 Channel n Single Fiber (Multiple Wavelengths) l1 l2 ln

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 WDM – Take multiple optical signals and multiplex them onto a single fiber – No signal format conversion 41 DS-1 DS-3 OC-1 OC-3 OC-12 OC-48 OC-12c OC-48c OC-192c Fiber DWDMOADM SONETADM Fiber

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 10G/wavelength with 25GHz spacing – The use of sub 100GHz for spacing is called Dense WDM. – Some vendors even propose to use 12.5GHz spacing, and it would multiplex up to 320 wavelengths 42 Spectrum A Spectrum B spacing

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

Optical Transmission Bands BandWavelength (nm) “New Band”1360 – 1460 S-Band1460 – 1530 C-Band1530 – 1565 L-Band1565 – 1625 U-Band1625 –

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

DWDM Network 46 MUX DEMUX

DWDM Network Components 47 Optical Multiplexer Optical De-multiplexer Optical Add/Drop Multiplexer (OADM) Transponder  15xx 1...n Optical λ => DWDM λ Usually do O-E-O

Optical Amplifier (OA) 48 P out P in EDFA (Erbium Doped Fiber Amplifier) amplifier Separate amplifiers for C-band and L-band gain

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. 49 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.

Cisco ONS 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

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

DWDM Network Add-and-Drop 52 Chicago Pittsburg New York Note: this is a linear topology, and not a ring topology. λ1: to Pittsburg λ2: to New York λ1: drop λ2: pass

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

IP over DWDM ??? 54 DWDM terminal DWDM terminal IP 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)

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 RFC2684) – SONET (via PPP) – Ethernet (via GFP) 55