Low-cost WDM Transceiver Technology for 10-Gigabit Ethernet and Beyond Brian E. Lemoff, Lisa A. Buckman, Andrew J. Schmit, and David W. Dolfi Agilent Laboratories Hot Interconnects 2000 Stanford, CA August 16-18, 2000 Presentation Overview Motivation 10 Gigabit Ethernet Overview WWDM Transceiver Design Experimental Results Future Directions Existing Fiberoptic LAN Standards LAN Transceiver Technology Standard Baud Rate Length Fiber Core Optical Sources Dia. FDDI 125 MBd 2 km 62.5 µm 1300-nm LED Fibre Channel 1.062 GBd 1 km single-mode 1300-nm Fabry-Perot Laser ATM 155 MBd 2 km 62.5 µm 1300 nm LED 622 MBd 500 m 62.5 µm 1300 nm LED Ethernet 20 MBd 2 km 62.5 µm 770 nm 860 nm LED 125 MBd 2 km 62.5 µm 1300 nm LED Gigabit 1.25 GBd 220 m 62.5 µm 770 nm 860 nm Lasers Ethernet 550 m 62.5 µm 1300 nm Fabry-Perot Laser 6 km single-mode 1300 nm Fabry-Perot Laser Simplex Sugarcube TX and RX. 820-nm LED, GaAs PIN. 10 Mb/s to 155 Mb/s. Duplex-SC Transceiver 1x9 package. 1300-nm LED, InGaAs PIN. 100 Mb/s to 622 Mb/s. Duplex-SC Transceiver 1x9 package. 850-nm VCSEL or 1300-nm FP-Laser. Gigabit Ethernet, Fibre Channel. MT-RJ or LC Small Form Factor Transceiver. 1/2 -wide package now replacing 1-inch 1x9 package at all data rates. Current Discussion Forums IEEE 802.3ae (10-Gigabit Ethernet): First draft of new standard for 10-GbE is expected later this year. T11 10-Gigabit Fibre Channel: T11.2/T11.3 is considering alternatives for 10-GFC. Optical Internetworking Forum (OIF): Industry organization is considering low-cost technologies for shortreach OC-192 (10-Gb/s). 10-Gigabit Ethernet Objectives To provide physical layer solutions to support: 100 m on installed multimode fiber 300 m on multimode fiber 2 km on single mode fiber 10 km on single mode fiber 40 km on single mode fiber 1
Proposed 10-Gb/s Solutions Parallel Optics - VCSEL arrays, fiber ribbon Multilevel modulation - Lower Bandwidth, Higher SNR Serial TDM - Single high-speed laser and detector Wide WDM - Multiple wavelengths, lower-speed lasers 10-GB/s Serial Proposals 1. 850-nm VCSEL + New 50-mm Fiber - With new fiber installation, claims of up to 300-m link lengths. 2. 1300-nm Fabry-Perot - Directly modulated, uncooled device capable of up to 2-km link length in SMF. 3. 1300-nm DFB - Directly modulated, uncooled device capable of up to 10-km link length in SMF. 4. 1550-nm EA-DFB - Externally modulated, cooled device capable of up to 40-km link length in SMF. Each of these proposals would use either SiGe or GaAs chip sets. Assuming 8B/10B coding, the baud rate is 12.5 GBd. Assuming Scrambling, the baud rate is 10.0 GBd. 10-GbE Objective 10-Gb/s Serial - Summary Solution 100 m on installed MMF No solution. FP laser can go 65 m. 300 m on MMF 850-nm VCSEL on new MMF No solution for installed MMF 2 km on SMF Uncooled 1300-nm FP laser 10 km on SMF Uncooled, Isolated 1300-nm DFB 40 km on SMF Traditional telecom-style cooled, isolated, externally modulated DFB Wavelength Division Multiplexing Brief Review for the Uninitiated Multiple data channels in a single fiber. Each channel has a different wavelength. WDM Multiplexer (mux) combines signals from several lasers into a single fiber. WDM Demultiplexer (demux) separates wavelengths onto separate detectors. Common practice in long-distance telecom with tight channel spacing (< 1 nm) and HIGH PRICE! 4 x 2.5 Gb/s WWDM LX Data 4 duplex channels, 2.5 Gb/s/channel Fiber Dual use SMF/MMF (SM TX, MM RX) Package Duplex-Connectorized Transceiver Sources Uncooled, unisolated DFB, No SMSR spec Wvlngth 1280,1300,1320,1340 nm (now changed to 1275.7, 1300.2, 1324.7, 1349.2) MUX 4-to-1 silica waveguide combiner Detectors InGaAs PIN photodiode array DEMUX Compact molded plastic bulk zigzag Wide Channel Spacing for Low Cost No temperature control required over 00ºC operation Laser wavelength varies by 5.0nm @1300nm Much higher laser yield is possible Wafer-to-wafer and intra-wafer wavelength spreads are tolerated Smaller, simpler demultiplexing optics Smaller, less collimated beams. Interference filters or gratings. Multimode fiber can be supported Large spatial and angular spread makes fine λ resolution tough. No amplifiers Narrow spacing unnecessary Entire useful spectrum of fiber can be covered if necessary 2
Agilent Labs SpectraLAN-LX Small Form Factor Prototype (Not for production) Assembled Module (nonfunctional) Assembled WWDM MTRJ Module MTRJ Connector RX TX Ball Grid Array NOTE: Laboratory prototype only. Production version will have larger package. Transmitter Optical Subassembly Transmitter Optical Subassembly Silica Waveguide Combiner SM Fiber Stub Si V-Groove Chip DFB Lasers Ceramic MCM Monitor Photodiode Array Receiver Optical Subassembly Wavelength Demultiplexer Three views of ray tracing in wavelength demultiplexer Wavelength Demultiplexer Multimode Fiber Stub InGaAs PIN Photodiode Array 3
Wavelength Demultiplexer 4-Channel Transmitter IC 12-Channel RX IC - Using 4 channels Soon-to-be available 4-channel IC will greatly reduce RX footprint Transmission (db) Demultiplexer Transmission Spectrum 0-1 -2-11 -12-13 -14-15 -16-17 -18-19 -20 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 Wavelength (nm) TX Interchannel Crosstalk Measured with external RX; 2.488 Gb/s 2 7-1 PRBS TX Interchannel Crosstalk at 3.125 GBd Single TX channel on, others off log BER one laser on all lasers on One channel on, three off 3.125 Gb/s PRBS extinction 8.4 db All 4 channels on 0-29 -28-27 -26-25 Received Optical Power (dbm) BER curves show no power penalty for single channel vs. four channels on TX. All four channels on 3.125 Gb/s PRBS extinction 9.0 db 4
TX-to-RX Crosstalk at 2.488 Gb/s No power penalty is observed in RX due to 4-channel TX data WWDM Link Results - 300 m MMF log BER TX data on TX data off TX data and supply off 1340 nm 2.488 GBd/channel 2 7-1 PRBS 1320 nm Multimode Polymer Mux Injection-molded demux 1300 nm Total launch power: -2 dbm -26-25 -24-23 -22-21 -20-19 -18-17 -16 Received Optical Power (dbm) 1280 nm 4 x 2.5-Gb/s WWDM Pro: One module satisfies all 10-GbE objectives from 1 m to 10 km, MMF and SMF. Lower speed electrical signals Low-cost laser and IC technologies Con: More chips More complicated assembly Requires optical mux and demux Future directions Many alternatives for 100-Gb/s to 1-Tb/s Transceivers Some Examples 100 Gb/s: 10 wavelengths, 10.0-Gb/s per channel 4 wavelengths, 12.5-Gsym/s per channel using PAM multilevel logic. 8 wavelengths, 12.5-Gb/s per channel 1 Tb/s: 10 fibers with 10 x 10.0-Gb/s WWDM per fiber 10 fibers with 4λ x 12.5-Gsym/s PAM per fiber And the list goes on... 5