Optical Communications and Networking

Transcription

1 1 Optical Communications and Networking Optical Access Network 卢薇

2 2 Carriers Networks Central Office Subscriber Business Wide Area Network (WAN) Metro Area Network (MAN): Inter-CO Network Metro Area Network (MAN): Access Network

3 3 Broadband Access Network Access Network:known as the first-mile / last-mile / subscriber-access network, connects the service provider central offices (COs) to businesses and residential subscribers. Broadband Access Networks are required by emerging applications, like HDTV, video on demand, online gaming and virtual reality, etc. Broadband Access Technologies: Digital Subscriber Line, DSL Hybrid Fiber Coax, HFC Broadband Over Power Lines, BPL Broadband Wireless Access, BWA Fiber-to-the-x, FTTx, x can be node, curb, building and home

4 4 Broadband Access Technologies: DSL Digital Subscriber Line (DSL): bring high-bandwidth information to home and small businesses over ordinary copper telephone lines using a point-topoint topology Asymmetric DSL, ADSL Symmetric DSL, SDSL Integrated DSL, IDSL High-Speed DSL, HDSL Very-High-Speed DSL, VDSL Advantage: sufficient copper resources, reduce investment cost, suitable for a wide range of scenarios PC Phone ADSL Modem Higher Frequency Band 25kHz~1.1MHZ 0~4kHZ Splitter Telephone Switching Equipment Upstream Downstream Telephone Network ISPs

5 5 Broadband Access Technologies: DSL xdsl ADSL SDSL Symmetry Downstream Bandwidth Upstream Bandwidth Maximum Transmission Reach Asymmetric 1.5Mbit/s 64Kbit/s 4.6~5.5km Asymmetric 6~8Mbit/s 640Kbit/s~1Mbit/s 2.7~3.6km Symmetric 384Kbit/s 384Kbit/s 5.5km Symmetric 1.5Mbit/s 1.5Mbit/s 3km IDSL Symmetric 160Kbit/s 160Kbit/s 4.6~5.5km HDSL VDSL Symmetric (2 wired) 1.5Mbit/s 1.5Mbit/s 2.7~3.6km Symmetric (1 wired) 768Kbit/s 768Kbit/s 2.7~3.6km Asymmetric 12.96Mbit/s 1.6~2.3Mbit/s 1.4km Asymmetric 25Mbit/s 1.6~2.3Mbit/s 0.9km Asymmetric 52Mbit/s 1.6~2.3Mbit/s 0.3km

6 6 Broadband Access Technologies: HFC Hybrid Fiber Coax (HFC) Network:fibers for core network, coax for distribution network, support up to 20Mbit/s data rate Full-service access: analog television, digital broadcast, Internet services, etc. Combine analog and digital transmission technology, fiber and coax technology, RF technology and highly-distributed intelligent technology A cost-efficient evolution strategy to push fiber near to subscribers Not only improve access bandwidth but also reduce network cost A promising solution for broadband access networks

7 7 HFC Network Architecture Transport Ring HeadEnd Distribution Hub Optical Node RF Hybrid Coupler RF Amplifier Customer House Optical Fiber Coaxial Cable

8 8 HFC Network Frequency Division Upstream Channel Downstream Channel Upstream Analog Television Downstream Personal (Digital) (Digital) Communication f f 1 2 f 3 f 4 f5 f 6 Area f 1 f 2 f 3 f 4 f 5 f 6 North America 5MHz 42MHz 88MHz 550MHz 860MHz 1000MHz Europe 5MHz 65MHz 110MHz 550MHz 862MHz 1000MHz China 5MHz 65MHz 65MHz 550MHz 750MHz 1000MHz Japan 5MHz 48MHz 88MHz 550MHz 860MHz 1000MHz

9 9 Broadband Access Technologies: BPL Broadband Over Power Lines (BPL):Couple radio frequency (RF) energy to existing electrical power lines to deliver high-speed voice and data communications to customers ISPs EPL Router Electrical Power Modern

10 10 Broadband Access Technologies: BPL Advantages Reduce investment in infrastructure construction since electrical power lines reach virtually every home in rural and urban areas Provide a convenient way to access internet whereas power grid exists More cheaper Always online Technical Obstacles Narrower bandwidth and bandwidth competition between subscribers Severe signal attenuation due to electrical power lines interference to high-frequency signals Electromagnetic radiation and data security problems caused by non-shield lines

11 11 Broadband Access Technologies: BWA Broadband Wireless Access (BWA):Provide high-speed communication access by wireless means to consumer and business markets Wireless personal area network, WPAN Wireless local area network, WLAN Wireless metropolitan area network, WMAN Wireless wide area network, WWAN

12 12 WPAN Wireless Personal Area Network (WPAN):Suitable for the connections between terminals in a small coverage, e.g., a wireless connection between Bluetooth headset and mobile phone; can be dynamically built Bluetooth: Working frequency: 2.4GHz, data rate: 1Mbit/s, transmission distance: m Infrared Wireless: Point-to-point short-reach communication, small size, low power, small interference, up to 16Mbit/s data rate ZigBee: Simpler and cheaper than Bluetooth, a defined data rate of 250Kbit/s, typically used in low data rate applications, e.g., home automation, medical device data collection

13 13 WLAN Wireless Local Area Network (WLAN):Links two or more devices using wireless communication to form a LAN within a limited area so that users can move around within the area and yet still be connected to the network Standard: IEEE a and IEEE b Advantages: Up to 11Mbit/s data rate, coverage ranges from several meters to hundreds of meters Modes of Operations: ad hoc mode and infrastructure mode

14 14 WMAN Wireless Metropolitan Area Network (WMAN) : A wireless network intended to support communications between devices and internet access in an metropolitan World Interoperability for Microwave Access (WiMAX): Based on the IEEE standard, a data rate of 1 to 10 Mbit/s, has a coverage of tens of kilometers As wireless extension of wired network access, provide a convenient network access for remote suburbs

15 15 WWAN Wireless Wide Area Network (WWAN): Transmit data over a long distance across a metropolitan area in a radius of tens of kilometers Mobile Telecommunication Cellular Network Technologies: LTE, WiMAX, etc. 3G (144Kbit/s), 4G (100Mbit/s), 5G (10Gbit/s)

16 16 BWA Advantages Flexible Coverage Broad Spectrum High Spectrum Utilization Flexible Link Adaptive Technology Dynamic Bandwidth Allocation Capability High Security Provide Connection-Oriented Services and Good QoS Assurance Good Support for Mobility

17 17 Broadband Access Technologies: FTTx Fiber-to-the-x (FTTx):a generic terminology for any broadband access network architecture that use optical fibers FTTN: Fiber to the node FTTC: Fiber to the curb FTTB: Fiber to the building FTTH: Fiber to the home Advantages (vs. DSL, HFC, BPL, BWA) Low investment and operation cost Low transmission attenuation and broader coverage Higher-bandwidth access

18 18 Global Subcarrier Growth

19 19 Optical Access Network Optical Access Network (OAN):connect central office (CO) and end-user subscribers with optical fibers to support last-mile telecommunications Point-to-point Active Optical Network Cost Bandwidth per User Passive Optical Network(PON)

20 20 Asymmetric Optical Access Network 1-to-1 Delivery Broadcast-and-Select Low Cost and Promising!

21 21 PON Terminologies OLT:Optical line terminal located at the service provider s central office ONU:Optical network units located at/near end users Upstream:Communication from ONU to OLT Downstream: Communication from OLT to ONU Core Network OLT Upstream Splitter ONU 1 ONU 2 User 1 User 2 Central Office Downstream Optical Distribution Network (ODN) ONU N User N

22 22 OLT Function Core Network Service Function Service Interface ATM Cross Connect Core Function Multiplexer/D e-multiplexer ODN Interface ODN Interface Service Interface Basic Function Operation Administration and Maintenance (OAM) Power Send data to ONUs in a broadcast way Initial and control the ranging process and record the corresponding information Assign bandwidth for ONU, i.e., time window for data transmission

23 23 ONU Function Core Function Service Function ODN ODN Interface Transmission Multiplexer/D e-multiplexer Client and Service Multiplexer /Division User Interface User 1 Basic Function Operation Administration and Maintenance (OAM) Power User Interface User N Receive data from OLT selectively Coordinate with OLT in terms of ranging and power control Buffer users data and send them in the assigned time window by OLT

24 Technical Standard Lecture 11: Optical Access Network 24 Next-Generation PON ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) IEEE ah ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G.987 ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) IEEE av ( ) ITU-T G ( ) ITU-T G ( ) ITU-T G ( ) NG-PON2 OFDM PON Co-DWDM-PON TWDM-PON NG-PON1 10G-GPON 10G-EPON TDM-PON GPON EPON A/BPON Time Line/Year

25 25 TDM-PON Downstream 1 2 n ONU 1 1 User 1 OLT Central Office 1 2 n Broadcast Splitter 1 2 n 1 2 n ONU 2 ONU N 2 n User 2 User N Upstream 1 ONU 1 1 User 1 OLT 1 2 n 2 ONU 2 2 User 2 Central Office Splitter Time Division Multiple Access (TDMA) n ONU N n User N

26 26 Synchronous Time Division Multiplexing (STDM) Send Data Multiplexer De-multiplexer Recieve Data A A A A A A B B B Wasted Time Slot B B B C E B A E D B A E D C B A C D D D D E E E E E E Advantages: Fixed time slots, good fairness, easy control Disadvantages: low channel utilization, cannot adaptive to users bandwidth

27 27 Asynchronous Time Division Multiplexing (ATDM) Send Data Multiplexer De-multiplexer Recieve Data A A A A A A B B B B B B C 5E 2B1A 5E 4D2B1A 5E 4D3C2B1A C D D D D E E E E E E Advantages: high channel utilization, adaptive to users bandwidth Disadvantages: more complicated

28 28 Multi-Point Control Protocol (MPCP) Multi-Point Control Protocol (MPCP):a signaling protocol between the OLT and the ONUs to facilitate a dynamic timeslot allocation scheme MPCP consists of three functions: Discovery Processing: the OLT discovers and registers new ONUs Report Handling: the OLT handles the REPORT messages that include bandwidth requirements generated by ONUs to make bandwidth assignments accordingly Gate Handling: the OLT sends gate messages to ONUs to grant time slots for them to transmit data

29 29 MPCP: Discovery Processing OLT GATE discovery: Type = Broadcast Content = Discovery window start, end times ONU Discovery Window REGISTER_REQ: Content = ONU Mac address REGISTER: Content = Assigned LLID GATE: Content = Grant Random Delay ONU registered and logical connection established REGISTER_ACK

30 30 MPCP: REPORT Handling OLT MAC Control Client ONU MAC Control Client Generate REPORT message TBO TBO MA_Control.indicator (REPORT) MAC Control Clock Register RTT Register MAC PHY - TB TBO TBO MA_Control.request (REPORT) MAC Control Clock Register Timestamp REPORT message MAC PHY TB TBO TBO

31 Upstream Data Path Lecture 11: Optical Access Network 31 MPCP: GATE Handling MAC Control Client MAC Control Clock Register OLT MA_Control.request (GATE) Time Stamp GATE message MAC PHY Start Stop TS Start Stop MAC Control Client MA_Control.indicator (GATE) MAC Control Write Registers TS Start Stop Clock Register MAC PHY ONU Slot Start Register Slot Stop Register Laser ON/OFF MA_DATA.request (?)

32 32 Exchange Process of REPORT and GATE MAC Client Ingress Queue OLT MAC Control Client DBA Agent MAC Client Egress Queue MAC Client Ingress Queue ONU MAC Control Client DBA Agent MAC Client Egress Queue Discovery Agent Discovery Agent Reporting Process Discovery Process Gating Process Gating Process Discovery Process Reporting Process Control Parser Control Multiplexer Control Parser Control Multiplexer MAC Control MAC Control MAC MAC PHY REPORT message GATE message PHY

33 33 Ranging Technology Upstream Conflict 1 1 ONU 1 1 User 1 OLT ONU 2 2 User 2 Splitter Central Office ONU User 3 The physical distances between OLT and ONUs are different Packets cannot arrive OLT in their pre-allocated time slots, resulting in conflicted packets OLT cannot recognize the conflicted packets, resulting in high bit error rate and sync loss

34 34 Timestamp Ranging T 1 : OLT local time T 4 : OLT local time OLT Tx Rx A T 1 T 3 Timestamp = T 1 Timestamp = T 3 ONU Tx Rx Downstream T 2 : ONU local time T 1 Wait Time at ONU T 3 T 3 : ONU local time Upstream Set ONU local time as T 1 RTT = T Downstream + T upstream = T 4 T 1 T 3 T 2 = T 4 T 3 Balance Delay: T d = T equ RTT

35 35 Upstream: Dynamic Bandwidth Allocation (DBA) (1) Interleaved Polling with Adaptive Cycle Time (IPACT):

36 36 IPACT DBA Strategies Fixed-service scheme: ignore requested timeslot size and always grants a fixed timeslot, we have B i = W Limited-service scheme:grants requested timeslot size, but no more than Maximum scheduling timeslot W MAX, we have B i = min B i,request W MAX Gated-service scheme: allocate as much timeslot as is requested by the ONU, we have B i = B i,request Constant/Linear-credit-service scheme: add a constant credit to requested timeslot size, we have B i = min B i,request + Const W MAX or B i = min B i,request Const W MAX Elastic-service scheme: get rid of a fixed Maximum scheduling timeslot limit. The only limiting factor is the maximum cycle time, we have B i = min B i,request i 1 N W j=i N B j,where N is the number of ONUs

37 37 Upstream: Dynamic Bandwidth Allocation (DBA) (2) Cyclic Polling-based with Dynamic Bandwidth Allocation (DBACP): OLT Tx Rx G G Idle timeslots Cycle K Cycle K R 1280 R G G 2800 R 3000 R ONU 1 Tx Rx G 6400 R G 2800 R ONU 2 Tx Rx G 1280 R G 3000 R DBA strategy: B i = B i,request + B cycle B i,request /N, B i,request < B cycle ( B i,request B i,request ) B cycle, B i,request B cycle

38 38 WDM-PON Wavelength Division Multiplexing (WDM) Transmitter (λ 1 ) λ 1, λ 2,, λ n λ 1, λ 2,, λ n Receiver (λ 1 ) Transmitter (λ 2 ) Multiplexer Fiber Optical Amplifier Fiber De- Multiplexer Receiver (λ 2 ) Transmitter (λ n ) Receiver (λ n ) Transmitter: Light-emitting diode, LED Laser diode, LD Multiplexer/De-multiplexer Arrayed waveguide grating, AWG Receiver Receiver sensitivity

39 MUX DEMUX Lecture 11: Optical Access Network 39 WDM-PON Transmitter (λ 1 ) OLT ODN ONU 1 Receiver (λ 1 ) Transmitter (λ 2 ) Transmitter (λ n ) Receiver (λ 1 ) Receiver (λ 2 ) MUX DEMUX Transmitter (λ 1 ) ONU 2 Receiver (λ 2 ) Transmitter (λ 2 ) ONU n Receiver (λ n ) Receiver (λ n ) Transmitter (λ n )

40 40 WDM-PON Advantages and Disadvantages Advantages: Large bandwidth capacity Transparent transmission, support any communication protocol Better scalability and flexibility: Application-oriented service provisioning to satisfy various QoS requirements, e.g., bandwidth, delay, bit error rate and jitter, etc. Higher security Disadvantages Higher cost caused by more expensive devices and incompatible ODN Low wavelength utilization and more complicated wavelength management Cannot fully utilize the advantage of broadcast in the downstream direction

41 41 WDM-PON Key Technologies: Light Source Solutions to Multi-Wavelength Optical Source: Distributed feed back laser (DFBL) Vertical cavity surface emitting laser (VCSEL) Multi-frequency laser (MFL) Spectrum sliced broadband light source Tradeoff Cost Performance

42 42 WDM-PON Key Technologies: MUX/DEMUX (1) Coupler E i1 (f) E o1 (f) Input Ports Output Ports E i2 (f) E o2 (f) E o1 (f) E o2 (f) = e jβi cos(κi) isin(κi) isin(κi) cos(κi) E i1 (f) E i2 (f)

43 43 WDM-PON Key Technologies: MUX/DEMUX (2) Arrayed waveguide grating (AWG) Arrayed Waveguide λ 11, λ 12, λ 13, λ 14 λ 11, λ 22, λ 33, λ 44 λ 21, λ 22, λ 23, λ 24 λ 31, λ 32, λ 33, λ AWG λ 21, λ 32, λ 43, λ 14 λ 31, λ 42, λ 13, λ 24 Input Coupler Output Coupler λ 41, λ 42, λ 43, λ 44 λ 41, λ 12, λ 23, λ 34

44 44 WDM-PON Key Technology: ONU Colorless (1) Tunable Laser: CO Input Data ONU Tunable Laser Output Data Rx AWG Fiber AWG Modulator Input Data Tunable Laser Advantages: Simple architecture, high bit rate, high wavelength adaptability, long transmission distance (~80km) Disadvantages Very expensive, dynamic wavelength assignment algorithm is needed

45 45 WDM-PON Key Technology: ONU Colorless (2) Spectrum Slicing: CO ONU TX/RX AWG Fiber AWG 1530nm 1565nm Input Data TX/Rx Modulator Filter LED Advantages: Low cost Disadvantages Low bit rate (<155Mb/s), short transmission distance

46 46 WDM-PON Key Technology: ONU Colorless (3) Injection Locked FP Laser: ONU 1 Broadband Light Source ASE seed light CO 1530nm 1565nm λ 1 λ 2 TX/RX ONU 2 TX/RX λ 1 λ 2 λ 3 λ 4 TX/RX TX/RX AWG Fiber AWG λ 4 ONU 3 RX WDM Upstream Data TX/Rx Advantages:low cost Filtered ASE spectrum λ IL F-P Laser Disadvantages: seed light is needed, limited bit rate λ Upstream Injection Locked Free Running Spectrum λ

47 47 WDM-PON Key Technology: ONU Colorless (4) Reflective Semiconductor Optical Amplifiers: Broadband Light Source ASE seed light CO 1530nm 1565nm λ 1 λ 2 ONU 1 TX/RX ONU 2 TX/RX λ 1 λ 2 λ 3 λ 4 TX/RX TX/RX AWG Fiber AWG λ 4 ONU 3 RX WDM Upstream Data TX/Rx λ RSOA Advantages:relatively higher bit rate Filtered ASE spectrum Disadvantages: seed light is needed, limited transmission distance λ Amplified & reflected output from RSOA RSOA mirror

48 48 Bandwidth Allocation in WDM-PON: Fixed ONU 1 Tx Multi-Wavelength Optical Source CO λ 1 Rx Array of Receivers De-Multiplexer Fiber λ 1 λ 2 λ 3 λ n MUX/DEMUX λ 2 ONU 1 Tx Rx λ 4 ONU n Tx Rx

49 49 Bandwidth Allocation in WDM-PON: Dynamic Multi-Wavelength Optical Source CO λ 1 λ 2 λ 3 λ n λ 1 ONU 1 Tunable Tx Rx Array of Receivers De-Multiplexer λ 1 λ 2 λ 3 λ n Fiber λ 1 λ 2 λ 3 λ n MUX/DEMUX λ 1 λ 2 λ 3 λ n λ 1 λ 2 λ 3 λ n λ 2 ONU 1 Tunable Tx Rx ONU n Tunable Tx λ 4 Rx

50 Coupler Coupler AWG Coupler Coupler Lecture 11: Optical Access Network 50 TWDM-PON Basic Architecture TX1 TX2 TX3 TX4 RX1 RX2 RX3 RX4 λ d1 λ d2 λ d3 λ d4 λ u1 λ u2 λ u3 λ u4 OLT AWG AWG λ d1,, λ d4 λ u1,, λ u4 ODN 1 ODN 2 λ d1 λ u1 λ d2 λ u2 λ d3 λ u3 λ d4 λ u4 λ d2 λ u2 λ d2 λ u2 λ d2 λ u2 ONU 1 RX1 TX1 ONU 2 RX1 TX1 ONU N RX1 TX1

51 51 TDM-based TWDM-PON TX1 OLT TX2 AWG WDM Downstream ONU 1 TX4 WDM λ d1,, λ dn AWG λ u ONU 2 Burst-Mode RX λ u TDM Upstream λ d2 λ u λ dn ONU N Main Advantage: Improve downstream bandwidth capacity, compatible with traditional TDM-PON and leverage network expansion and upgrade

52 52 WDM-based TWDM-PON TX OLT ONU 1 RX1 TDM Downstream RX2 RX4 AWG WDM λ d λ u1,, λ un WDM Upstream AWG λ d λ u2 λ d λ un ONU 2 ONU N Main Advantage: Simplify network control protocol, no need to coordinate ONUs data transfer and perform load balancing

53 Coupler AWG Coupler Lecture 11: Optical Access Network 53 TDM-over-WDM TWDM-PON TX1 TX2 λ d1 λ d2 OLT λ d1 λ u1 TDM ONU 1 ONU 2 ONU 3 TXn RX1 RX2 RXn λ dn λ u1 λ u2 λ un AWG WDM λ dn λ un ONU (n-2) ONU (n-1) ONU n

54 Coupler Lecture 11: Optical Access Network 54 WDM-over-TDM TWDM-PON TX1 TX2 TXn RX1 RX2 RXn λ d1 λ d2 λ dn λ u1 λ u2 λ un OLT AWG TDM WDM AWG AWG λ u1 λ d1 λ un λ dn λ u1 λ d1 λ un λ dn ONU 1-1 ONU 1-n ONU m-1 ONU m-n

55 55 Performance and Cost Comparisons Compared Aspects TWDM-PON Architectures TDMA WDMA TDM over WDM WDM over TDM Architecture Features ONU: dedicated Wavelength (downstream) WDM for upstream to simplify access protocol Increase user and bandwidth upgrade economically Reduce system cost while providing highquality services Fiber Share upstream/downstre am share or separated upstream/downstre am share or separated upstream/downstre am share upstream/downstre am share Topology Upstream: TDMA Downstream: WDM Upstream:WDM Downstream: TDMA Groom Multiple TDMs with a WDM Groom multiple WDMs with a TDM Network Flexibility Bad Bad Good Good Use Cost per Users Infrastructure Cost per Users Common Cheap Expensive Expensive Cheap Cheap Common Expensive

56 56 TWDM-PON Advantages Flexible networking to reduce OPEX and CAPEX Compatible with traditional TDM-PON High bandwidth capacity Long transmission distance and broad coverage Reduce investment cost and risk