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Optical Networking Technologies

Optical Networking Technologies. 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). Optical Transmission. optical signal. electrical signal. electrical signal. Optical

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Optical Networking Technologies

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  1. Optical Networking Technologies

  2. 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)

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

  4. 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

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

  6. 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?

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

  8. Optical Spectrum l IR UV 125 GHz/nm • Light • Ultraviolet (UV) • Visible • Infrared (IR) • Communication wavelengths • 850, 1310, 1550 nm • Low-loss wavelengths Visible 850 nm 1550 nm 1310 nm Bandwidth

  9. Optical Fiber Core Cladding • An optical fiber is made ofthree sections: • The core carries thelight signals • The cladding keeps the lightin the core • The coating protects the glass Coating

  10. 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

  11. Bending of light ray

  12. Figure 7.12 Propagation modes

  13. Figure 7.13 Modes

  14. Figure 7.14 Fiber construction

  15. Figure 7.15 Fiber-optic cable connectors

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

  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!

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

  19. 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

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

  21. 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

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

  23. 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.984

  24. xPON Comparison

  25. PON Case Study (BPON) Optical Network Terminal (ONT) (customer premise) Optical Line Terminal (OLT) (Central Office) Two Ethernet ports One T1/E1 port Optical transport: 622M bps T1/E1 802.3 Packet Core (IPoATM) CES RFC2684 AAL1 AAL5 SAR/CS ATM TDM Core (PSTN) PON (G.983)

  26. GPON

  27. EPON Evolution

  28. EPON Downstream

  29. EPON Upstream

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

  31. IP Over SONET 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? T1 OC-3 DS3 IP 802.3 IP RFC2684 IP IP ???? AAL5 PPP 802.3 ATM GFP RFC1619 SONET SONET SONET SONET SONET TDM Traffic GFP: Generic Frame Procedure RFC 2684: Encapsulate IP packet over ATM RFC 1619: Encapsulate PPP over SONET

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

  33. PPP over SONET • RFC 1619 (1994) • The basic rate for PPP over SONET is STS-3c at 155.520 Mbps. • The available information bandwidth is 149.760 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.

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

  35. Dense Wave Division Multiplexing (DWDM) Ref: Cisco DWDM Primer

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

  37. 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 Single Fiber (One Wavelength) Channel n l1 l2 Single Fiber (Multiple Wavelengths) ln

  38. TDM vs. WDM DS-1 DS-3 OC-1 OC-3 OC-12 OC-48 • 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 themonto a single fiber • No signal format conversion SONET ADM Fiber OC-12c OC-48c OC-192c DWDM OADM Fiber

  39. 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 Spectrum A Spectrum B spacing

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

  41. Optical Transmission Bands

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

  43. DWDM Network MUX DEMUX

  44. DWDM Network Components l1 l1...n 850/1310 15xx l2 l3 Transponder Optical Multiplexer Optical λ => DWDM λ Usually do O-E-O l1 l1...n l2 l3 Optical De-multiplexer Optical Add/Drop Multiplexer (OADM)

  45. Optical Amplifier (OA) Pout Pin gain • EDFA (Erbium Doped Fiber Amplifier)amplifier • Separate amplifiers for C-band and L-band

  46. 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.

  47. 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/on15800s/prodlit/ossri_ds.pdf

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