Multilevel Serial PMD Update. Rich Taborek - IEEE HSSG - 10 GbE

Transcription

1 Multilevel Serial PMD Update Rich Taborek - IEEE HSSG - 10 GbE

2 What is MAS? Multilevel Analog Signaling: Generic term used to describe various Multilevel Modulation methods Applicable to most media: Copper, Wireless, Fiber, etc. Common methods include PAM, FSK, DPSK, QAM, etc. Why? Reduce the Line Rate for a given Data Rate How Much? ½ the data rate first, ¼ is possible MAS transceivers bring CMOS to the PMD to: Reduce OptoElectronics ƒ/cost Optimize System Interconnect Optimize Tx-Rx Link Operation Increase Link Distance Support Installed Fiber 200 m Simplify Emissions Compliance 2 Rich Taborek - IEEE HSSG - 10 GbE

3 Technology Lowpass Filtered Photocurrent (A) T i m e ( s ) x NRZ, Quinary Amplitude Shift Keying of Optical Intensity A.k.a. 5-level PAM of Optical Intensity 5 Gbaud (2.5 GHz) line rate for 10 Gbps Simple Single-Channel (Serial) PMD type Adaptation of 1000BASE-T Ethernet modulation, but simpler No crosstalk, echo, DSP FEC compensation required PMD independent: Optical LW/SW, MMF/SMF, CX Copper Hari/MAS/laser driver implementable in, 0.18µm CMOS Single CMOS chip includes Laser Driver for most PMDs Only Laser, PIN, and TIA required for full PMD Small, Low Power, accommodates Small Form Factor package 10G PMD BOM should be not much higher than for 1G at maturity 3 Rich Taborek - IEEE HSSG - 10 GbE

4 MAS Attributes Meets or exceeds ALL HSSG distance objectives 2.5 GHz line rate yields ~200 m over installed 1300 nm ~800 m over enhanced MMF 2/10/40 km SMF OK. Need HD Laser Driver for >10 km rate = $ O/E, distance, reliability, emissions costs with CMOS, smart closed-loop optical feedback Only technology capable of supporting 1/10G operation Open technology, no basic IP, no barriers to entry Higher rates with more sophisticated modulation (e.g. PAM9, QAM, FDM), combination with WWDM, Parallel Optics Risks: New technology for optics, Need Linear TIA 4 Rich Taborek - IEEE HSSG - 10 GbE

5 PMA - Binary vs. PAM5 Signaling Maximum Optical Power Logic Level 1 Logic Level +2 Bit1: 0/1 +1 Bit: 0/1 Coding 0 Minimum Optical Power Binary Signaling a.k.a. PAM2, On-Off-Keying Bit2: 0/ PAM5 1000BASE-T 5 Rich Taborek - IEEE HSSG - 10 GbE

6 PAM Signaling PAM5 Example Lowpass Filtered Photocurrent (A) PAM Available Power Time (s) x Received pattern from simulation - Courtesy Transcendata, Inc. 6 Rich Taborek - IEEE HSSG - 10 GbE

7 PAM5 4 Code Mapping Simple, Direct Mapping Parallel 10GMII: 32 bit data path divided into four 8 bit lanes + 1 control bit per lane Character set includes: DATA, IDLE, SOP, EOP, ERROR Serial 10GMII: 4 lane serial data path One 8B/10B code-group corresponds to one Parallel 10GMII character PAM5 4: Serial link One PAM5 4 symbol corresponds to one Serial GMII 8B/10B (Hari) code-group 7 Rich Taborek - IEEE HSSG - 10 GbE

8 PAM5 4 Code Mapping Example Parallel 10GMII D<0:7> I I S d p d d --- d d d d f I I I I I D<8:15> I I d p d p d d --- d d d f T I I I I I D<16:23> I I d p d p d d --- d d d f I I I I I I D<24:31> I I d p d s d d --- d d d f I I I I I I Serial 10GMII Lane 0 K R S d p d d --- d d d d f K R K R K Lane 1 K R d p d p d d --- d d d f T K R K R K Lane 2 K R d p d p d d --- d d d f R K R K R K Lane 3 K R d p d s d d --- d d d f R K R K R K PAM5 4 R R R S d p d p --- d d d --- d f T R R K K K K 8 Rich Taborek - IEEE HSSG - 10 GbE

9 PAM Coding Objectives PAM systems have coding objectives similar to those of On-Off-Keying (e.g. 8B/10B) including: Special Symbol support (SOP, EOP, Idle, etc.) DC Balance for jitter containment, AC/DC coupling High Transition Density/Low Run Length (CDR) Good Error Containment, Hamming Distance Fast symbol/frame synchronization Low Emissions/Good Spectral properties Low complexity PAM systems benefit from FEC coding gain E.g. Reed-Solomon(255,239) code in 10-4 BER, out Rich Taborek - IEEE HSSG - 10 GbE

10 PAM5 4 Coding Detail 1 PAM5 symbol = 1 baud = Gbaud Each PAM5 symbol supports 2+ bits 4 PAM5 symbols = 5 4 = 625 codes = ~9.22 bits 8B/10B supports 256 data codes, 12 special codes 268 codes map to ~ 400/1024 total codes PAM5 4 coding structure Avoid 5 flat-line symbols (e.g. all +2, +1, etc.) 5 Reserve ternary codes (+2, 0, -2) for special codes 81 Encode 9 bits per symbol: 8 Data, 1 FEC 512 Treat remaining 27 symbols as invalid 27 Scramble PAM5 4 symbols for DC Balance Total: Rich Taborek - IEEE HSSG - 10 GbE

11 Circuit Design Challenges Waveform Synthesis and Capture 5 GigaSymbols per second (Gsps) but process amenable to parallel processing Clock and Data Recovery (CDR) for Hari & PAM5 Low Jitter PLL with/without Reference Clock PAM5 no worse than Hari Forward Error Correction (FEC) Focusing on Reed-Solomon codes Issues: Mapping efficiency, coding gain, gate count, low latency 11 Rich Taborek - IEEE HSSG - 10 GbE

12 Location in 10 GbE Parallel Serial Medium TXC MAC TXD RXC 36 PCS/PMA MAS PMD RXD 36 PHY Management MDC MDIO Management 12 Rich Taborek - IEEE HSSG - 10 GbE

13 /Transceiver Data Flow C CCC E/O Des Dcd I/R Enc Ser MAS E/O c Hari Local Clk PLL PAM5 4 C CCC E/O Ser Enc I/R Dcd Des MAS O/E c Management PAM5 4 Link operates independently of Hari Local Clock not supported on Hari, Optional in Transceiver Insert/Remove protocol not required if no Local Clock 13 Rich Taborek - IEEE HSSG - 10 GbE

14 OSI/1 GbE/10 GbE MAS Models Data Format N x 8 bit 10 bit 1 bit Typical 1 Gig Link Protocol Coding SERDES XCVR Media OSI Reference Model Application Presentation Session Transport Network Data Link Physical Proposed 10 Gig PAM5x4 Protocol Coding SERDES SERDES XCVR Media 4 x 8 bit 4 x 10 bit Hari 4 x 1 bit 1 bit 14 Rich Taborek - IEEE HSSG - 10 GbE

15 10 GbE MAS Specific Elements OSI REFERENCE MODEL LAYERS APPLICATION PRESENTATION SESSION TRANSPORT NETWORK DATALINK PHYSICAL 802.3ae FULL DUPLEX LAYERS HIGHER LAYERS LLC LOGICAL LINK CONTROL MAC CONTROL (OPTIONAL) MAC MEDIA ACCESS CONTROL RECONCILIATION PARALLEL 10GMII PCS PHYSICAL CODING SUBLAYER PMA PHYSICAL MEDIUM ATTACHMENT SERIAL 10GMII PMD PHYSICAL MEDIUM DEPENDENT PMDC PMD CODING SUBLAYER (MAS) PMDS PMD SIGNALING SUBLAYER (MAS) LX-PMD MDI MEDIUM SX-PMD MDI MEDIUM 15 Rich Taborek - IEEE HSSG - 10 GbE

16 MAS System Structure Example Device 1 Multiport 10GbE MAC/PHY Integrated 10G MII Integrated PHY/Hari Core PCB mounted Device 2 Singleport 10GbE MAC/PHY Quad-Serial 10 GMII interface (Hari) Gbaud, 8B/10B encoded >0-24 nominal Mgmt 8/16/32 8/16/32 / Transceiver Front Panel Mounted Integrated Hari Core Parallel 10GMII PCS/PMA Discrete Hari Chip Mgmt Medium: MMF, SMF, CX Distance: >0 m to 40 km 5 Gbaud, PAM5 encoded Medium / Transceiver 16 Rich Taborek - IEEE HSSG - 10 GbE

17 MAS Transceiver Block Diagram Management Interface Link Management Auto Negotiation PHY Control TX CTL Quad SerDes Data IFCE Encode Decode Error Detection and Correction RX CTL Waveform Synthesis Waveform Capture Signal Detect Optical Connector CHIP Clock Recovery Optics Version shown, Alternatives: Short-haul Copper 17 Rich Taborek - IEEE HSSG - 10 GbE

18 PAM s History in Ethernet 100BASE-TX uses multi-level coded symbols 100BASE-T4 uses multi-level coded symbols 100BASE-T2 uses PAM5 1000BASE-T uses PAM5 MAS, PAM5, is NOT new to Ethernet 18 Rich Taborek - IEEE HSSG - 10 GbE

19 Optical Issues Non-Issues Laser BW ~1.1 Baud ~5.5 GHz Kink-free Lasers required Non-linearity Characterization Laser Noise Containment Rx BW ~0.75 Baud ~ 4 GHz Linear TIA Availability MAS Optical Power Penalty 4.1 db (optical) for PAM5 Receiver Nonlinearity Large Signal Nonlinearity Sidemode Supression Ratio Laser Absolute Wavelength Laser Temperature Control Photodetector linearity Skew (lane, power) Crosstalk Packaging (independent) Protocol (independent) Media (independent) 19 Rich Taborek - IEEE HSSG - 10 GbE

20 Large and Small-Signal Nonlinearity LD Gross Nonlinearity LD Small-Signal Nonlinearity saturation Laser Power kink Laser Power y max threshold I th I sat Current Current 20 Rich Taborek - IEEE HSSG - 10 GbE

21 Linearity Compensation Light Vertical Eye Closure Penalty V 2 PD Voltage V 1 V 0 V -1 V -2 I TH I -2 I -1 I 0 I 1 I 2 100% Noise I SAT LD Current 21 Rich Taborek - IEEE HSSG - 10 GbE

22 Auto-Negotiation Protocol uses Signal Detect-based Tones New AN protocol for optical/copper serial links Enables speed negotiation, simple 1/10 GbE integration Tone frequency can easily span >10X line rates Tone Pulses correspond to Fast Link Pulses (FLPs) Tone Pulses are arranged Pulses to a Burst Tone Pulses calibrate MAS Tx power and Rx levels Increases optical link budget Eliminates optical compression penalty Compensates for laser non-linearity Rx levels set to ensure same SNR/BER for all eyes 22 Rich Taborek - IEEE HSSG - 10 GbE

23 1/10 GbE MAS Signaling 1 GbE 8B/10B 10 GbE PAM5 200 ps ps 1 bit ps 1 code-group 23 Rich Taborek - IEEE HSSG - 10 GbE

24 New Optical Multilevel Technology Kestrel Solutions - Optical FDM Uses Frequency Division Multiplexing combines individual 155 Mb/s channels into a single wavelength QPSK is the simplest form of QAM (QAM4) Multiple-Subcarrier Modulation (MSM) Multiple digital streams are modulated onto carriers at different frequencies, permits transmission with minimal ISI. Work in Progress: Roy You and Joseph M. Kahn, Average-Power Reduction Techniques for Multiple-Subcarrier Optical Intensity Modulation, IEE Colloquium on Optical Wireless Communication, London, England, June 22, Rich Taborek - IEEE HSSG - 10 GbE