Part 2 Part2: Lecture 01 Optical technologies Optical networks: Technologies Hybrid networking, network virtualization Traffic engineering (Marijke Kaat) OpenFlow and SURFnet (Ronald van der Pol) Physical layer Part2: Lecture 01 Optical technologies Application Presentation Session Transport Network Data Link Physical The purpose of the physical layer (PHY) is to create the electrical, optical, or microwave signal that represents the bits in each frame. 1
PHY functions From bits to signals Channel coding encode a series of bits into signals Modulation adapt signal to the transmission channel Multiplexing share the channel Packet Transmission Packets Sender Receiver 0100010101011100101010101011101110000001111010101110101010101101011010111001 Header/Body Header/Body Header/Body Bit Stream 0 0 1 0 1 1 1 0 0 0 1 Digital Signal Analog Signal Analog and digital data Signaling Digital data à modulation/demodulation à analog transmission Modem: Signaling is the method of representing the bits (signals) The Physical layer standards must define what type of signal represents a "1" and a "0"Bits Analog data à coder/decoder à digital transmission CODEC: CODEC 2
Modems speeds Encoding Bit rate (bits/s) The number of bits processed per unit of time. Encoding is the symbolic grouping of bits (symbols or code groups) prior to being presented to the media. Bauds or signal rate or modulation rate (baud): The number of signaling events per second 1 kbd = 1000 baud è 1000 symbols per second 1000 tones in a modem 1000 pulses in a line code 00 11 01 10 4 symbols per second = 4Bd 8 bits per second = 8 b/s Advantages using code groups include: Reducing bit level error Helping to distinguish data bits from control bits Better media error detection 1 second Encoding examples More encodings NRZ - Non return to zero SONET uses NRZ (light off, light on) High voltage = 1; Low voltage = 0 Voltage does not return to 0 between bits Manchester encoding Ethernet uses Manchester encoding (10 Mbit/s) XOR of clock and data 8b/10b = 8 bits of data in 10 bit symbols (5b/6b + 3b/4b) Used in: GigaBit Ethernet InfiniBand USB 3.0 PCI Express (< 3.0) 64b/66b: 64 bit data in 66 bit symbols Used in: 10 GE 40 GE 100GE 3
Optical transmission Transmission media Total internal reflection. Beware of: Degradation of signal Fiber fuse Used to : 1. Achieve higher bandwidth 2. Span longer distances Optical transmission range Optical Spectrum UV Visible IR 125 GHz/nm λ λ = c ν Light Ultraviolet (UV) Visible Infrared (IR) Communication wavelengths 850, 1310, 1550 nm Low-loss wavelengths Specialty wavelengths 980, 1480, 1625 nm 850 nm 980 nm 1310 nm 1480 nm 1550 nm 1625 nm 4
Comparison Fiber optic cables Pros of electrical transmission Pros of optical transmission Core: A center core made from glass or plastic fibers Lower material cost Lower cost of transmitters and receivers Capability to carry electrical power as well as signals exceptionally low loss, absence of ground currents and other parasite signal and power issues inherently high data-carrying capacity. Cladding: A plastic coating cushions the fiber center; Kevlar fibers help to strengthen the cables and prevent breakage. Buffer coating: the outer insulating jacket made of teflon or PVC. Fiber cables Different single mode fibers Multi mode Cheaper Over short distances: 2 km for 100 Mbit/s (100BASE-FX) 220 550 m for 1 Gbit/s (1000BASE-SX) 300 m for 10 Gbit/s (10GBASE-SR) Wavelengths: 850 and 1300 nm Single mode Single mode Over long distances: 80 km at 10Gbit/s (XENPACK) Wavelengths:1300 nm and 1550 nm SMF (G.652) DSF (G.653) NZDSF v Good for TDM at 1310 nm v OK for TDM at 1550 nm v OK for DWDM (With Dispersion Mgmt) v OK for TDM at 1310 nm v Good for TDM at 1550 nm v Bad for DWDM (C-Band) v OK for TDM at 1310 nm (G.655) v Good for TDM at 1550 nm v Good for DWDM (C + L Bands) 5
Connectors GBIC - Gigabit Interface Converter Transceivers SFP - Small Form-factor Pluggable (and SFP+) SC - square/standard LC - little/local ST - straight tip/bayonet XENPACK XFP - 10 Gigabit Small Form-factor Pluggable Couplers db Attenuation Decibels (db) is the unit to express differences in signal strengths (loss or gain) between start and end. It s a relative value expressing attenuation. P1 and P2 power at start and end P1/P2 is the power ratio db= 10 Log 10 (P1/P2) E.g.: a ratio P1/P2 = 2 is equivalent to 3DB 6
dbm Power budget Decibels milliwatt (dbm) is the unit to express power of an interface (output power and the receiver sensitivity). Its an absolute value. Input power P in P in = 0 dbm P in = 1mW Output power P out P out = -20 dbm P out = 0.01mW X dbm = 10 Log 10 (Power in mw/1mw) Optical loss: P in -P out (in db) P in -P out = 20 db Affected by: Fiber attenuation Splices Patch Panels/Connectors Optical components (filters, amplifiers, etc) Bends in fiber Contamination (dirt/oil on connectors) What about Maximum tolerated power and Maximum Launch power? Optical Attenuation Specified in loss per kilometer (db/km) 0.40 db/km at 1310 nm 0.25 db/km at 1550 nm Loss due to absorption by impurities 1400 nm peak due to OH ions 1310 Window 1550 Window Test EDFA optical amplifiers available in 1550 window 7
Optical networks Optical networks An optical network utilizes fiber optic as transmission medium.. First generation optical networks - SONET/SDH networks: optics provided transmission and capacity. switching and intelligence handled in electronics Second generation networks - all optical: routing, switching and intelligence are moving in the optical layer. Basic components Couplers and splitters, used to combine and split signals in the network; Taps are type of couplers that tap off small portion of the power from a light stream for monitoring purposes; Wavelength crossconnect Cascading mux and demux can create a (static) OXC Filters λ 1, λ 2, λ 3, λ 4 λ Wavelength 1 filter λ 1 1, λ 1 2, λ 1 3, λ 1 4 λ 1 λ 2 λ 3 λ 4 λ 2, 1 λ1, λ 1 2 3, λ 2 4 Multiplexers(mux) and demultiplexers (demux) λ 2, λ 2 1 2, λ 2 3, λ 2 4 λ 1 1, λ 2 2, λ 2 3, λ 1 4 λ 1 λ 2 λ 1, λ 2, λ 3, λ 4 λ 1, λ 2, λ 3, λ 4 λ 3 λ 1 λ 2 λ 3 λ 4 λ 4 8
MEMs devices Amplifiers Signals get attenuated as they travel in fibers. Two approaches: Regenerators, converts optical into electrical signal and retransmit; Amplifiers: Amplification window, the range of wavelengths over which there is signal gain Types: erbium doped fiber amplifiers (EDFAs); Semiconductor optical amplifiers (SOA); Raman optical amplifiers. Transmitters Semiconductor lasers are the light source for optical transmission. They have a fixed wavelength for operation. Think of gigabit Ethernet: 1000SX 1000LX 1000ZX Tunable lasers can alter the wavelength of operation. They open up the possibility to have: Reconfigurable optical networks Optical packet switched networks Multiplexing schemes TDM: SONET/SDH (D)WDM 9
TDM TDM Time-Division Multiplexing (TDM) two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. TDM example: T-carrier Telephony switches: DS0 (Digital Signal 0) is the basic voice signal: 64kbit/s (8Khz sample rate with 8bit sample) In North America: DS1 (running over a T1 line) is 24DS0 plus 8kbps synchronization and maintenance overhead:1.544mbps DS3 (running over a T3 line) is 28 DS1 (or 672 DS0): 44.736Mbps In Europe/Japan: E1 is 32 DS0: 2.048Mbps E3 is 512 DS0: 34.368 Mbps SONET/SDH Synchronous Optical Networking (SONET) Synchronous Digital Hierarchy (SDH) Originally designed to transport different circuits (DS0, DS3) of different origins within a single framing protocol. Currently the frame can transport: Ethernet (Ethernet over SONET - EOS) IP (Packet over SONET - POS) Learn more: "Synchronous Optical Network (SONET) - Basic Description including Multiplex Structure, Rates and Formats," ANSI T1.105-1995. "Synchronous Optical Network (SONET)--Payload Mappings," T1.105.02-1998. 10
STS-1 STS-3 An STS-3 frame has 9 rows * 270 columns = 2430 bytes. It is transmitted in 125microseconds: 8Khz STS-3: 155.52 Mbps (equivalent to 1 STM-1 in SDH) Transport Overhead Synchronous Payload Envelope New transport overhead is obtained with byte interleaving. Channelized and concatenated (unchannelized) Ethernet frames: First: header Then: Payload Finally: Trailer Transmitting SONET/SDH frames SONET/SDH frames Transmitted row by row (each row with transport overhead and payload) SONET/SDH data rates SONET Optical SONET frame SDH level and Payload Line rate (kbps) Carrier Level format frame format bandwidth (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 11
Optical carrier level Learn more: PPP over SONET/SDH RFC 2615- Jun.1999 Packets over SONET/SDH STS-N Electrical multiplexer OC-N optical transmitter PO PO User data Stream-1 User data User data EO conversion OC-N signal SPE TO SPE User data Stream-2 User data Stream-N STSX-N interface GFP Generic Framing Protocol: it allows to map client packets into the SONET/SDH payloads, in order to transport non-tdm traffic more efficiently. (D)WDM Ethernet frame 12
WDM Transmission windows Wavelength-division multiplexing (WDM) multiplexes multiple optical carrier signals on a single optical fiber by using different wavelengths (colours) of laser light to carry different signals. Band Description Wavelength range O band original 1260 to 1360 nm E band extended 1360 to 1460 nm S band short wavelengths 1460 to 1530 nm C band conventional ("erbium window") 1530 to 1565 nm L band long wavelengths 1565 to 1625 nm U band ultralong wavelengths 1625 to 1675 nm Types of WDM (Conventional) WDM 16 channels in the C-band(1550nm) Wavelength tloss 1rst wavelength 850nm 3dB/km 2 nd wavelength 1310nm 0.4dB/km 3 rd wavelength 1550nm (C band) 0.2dB/km 4 th wavelength 1625nm (L band) 0.2 db/ km Dense WDM - DWDM 40 channels at 100Ghz spacing or 80 channels at 50 Ghz spacing in the C-band Ultra DWDM extend the spacing to 2GHz With Raman amplification instead EDFA channles double and reach the L-band Coarse WDM Started with two channels (1310 and 1550 nm) Nowadays 16 channels in the O-band (around 1310nm) and C-band (around 1550nm) 13
19/04/16 Interfaces to WDM TDM and DWDM Comparison Transponders are an essential component: They convert the incoming optical signal in an ITU-standard wavelength. SONET/SDH from client -> an electrical signal -> ITU wavelength TDM (SONET/SDH) Takes signals and multiplexes them to a single higher optical bit rate E/O or O/E/O conversion (D)WDM Takes multiple optical signals and multiplexes onto a single fiber No signal format conversion DS-1 DS-3 OC-1 OC-3 OC-12 OC-48 OC-12c OC-48c OC-192c SONET ADM DWDM OADM Fiber Fiber OTN Know what to buy? OTN Optical Transport Network Replaces SONET/SDH as transport mechanisms, as it betters integrate with DWDM. OTN specifies a digital wrapper to create an optical data unit (ODU), Learn more: ITU G.709 Optical Transport Network (OTN)" ITU G.872 "Architecture for the Optical Transport Network (OTN)" CISCO CRS Available Interface modules: 1-Port OC-768C/STM-256C Tunable WDMPOS 4-Port 10GE Tunable WDMPHY 4-Port OC-192c/STM-64 POS/DPT 8-Port 10 Gigabit Ethernet 16-Port OC-48c/STM-16c POS/DPT Cisco CRS Single-Port OC-768c/STM-256c POS Juniper T4000 Available line cards: 100-Gigabit Ethernet 10-Port 10GbE Oversubscribed Ethernet 4-port 10 GE 4-Port OC-192 10-Gigabit Ethernet Dense Wavelength Division Multiplexing (DWDM) Optical Transport Network 10-Gigabit Ethernet Dense Wavelength Division Multiplexing (DWDM) N.b: these are just two random examples to show you now (should) know what these routers can do. 14
Literature Home reading Chapter 1 Technology overview Chapter 2 SONET and SDH Basics Chaper 3 SONET and SDH: advanced topics Chapter 1- Introduction to optical networks Section 6.1 - SONET/SDH For the test on Apr. 22 read: A survey of network virtualization by Chowdory and Boutaba http://www.sciencedirect.com/science/article/pii/s1389128609003387 (EXCLUDING section 3) 15