conference & convention enabling the next generation of networks & services Fibers for Next Generation High Spectral Efficiency Undersea Cable Systems Neal S. Bergano and Alexei Pilipetskii Tyco Electronics Subsea Communications
conference & convention enabling the next generation of networks & services Presenter Profile Alexei Pilipetskii received his M.S degree in physics from Moscow State University in 1985. From 1985 to 1994 he worked at the General Physics Institute in Russia. He received his Ph.D. in 1990 for research in nonlinear fiber optics. From 1994 to 1997 he was with the University of Maryland Baltimore County, where his interest shifted to fiber optic data transmission. Since 1997 he has been with SubCom, where he works on a number of research and development projects. He is currently the director of a research group focusing on next Alexei Pilipetskii generation technologies for undersea Director - System Modeling & Signal transmission systems. Processing Research email: apilipetskii@subcom.com Tel: 732-578-7533
conference & convention enabling the next generation of networks & services Fibers for Next Generation High Spectral Efficiency Undersea Cable Systems • The importance of new “linear” fiber types • Dispersion management in transoceanic length cable systems – 10G DPSK transmission • High spectral efficiency systems: – Will require polarization multiplexed formats – The DP-PSK format with coherent receivers • Transmission Fiber “Figure-Of-Merit” (FOM) • New transmission results
conference & convention enabling the next generation of networks & services Advances in Technology – New Fiber Types are Important! 155x100G in 60nm 100000 Experimental 3,730 10000 Transmission 1,800 L 6,000 a C R Capacity (Gb/s) r o g e h e c 1000 320 D e e A r i H i 2,560 e s v A r y n e p e F m b t 640 r 100 a e u s r p r i l F d s l & l i T i C f i 100 b o i r e 160 - e a n B r L n s r a s F a F s F r n l E m D o a g d 40 C t r i e + s m t A M e E s 10 L A m a n i a q G o a r t e n p u s n a e r d a a l g a 10 D i i n f g l e i i N F i D e z e s i r a Z A 2.5 5 b + m p s t D r e i e F 1 e o e W S r r n n a i s b F D t i e o a M r O n n A p d m t i c N p a l Z i l f i D e S r s F 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 Year
conference & convention enabling the next generation of networks & services Why Fibers are So Important: Linear and Nonlinear Transmission 18 Nonlinearity 17 OSNR limited limited Q (dB) 16 15 14 experiment 13 simulation 12 -3 0 3 Relative pre-emphasis (dB) • One of the first Q vs. power curves published: 16x10Gb/s at 7500 km • Nonlinearity limits achievable performance (Q-factor), distance and spectral efficiency Ref: Golovchenko, E.A., et. al. , OFC 1999, paper ThQ3
conference & convention enabling the next generation of networks & services Fibers and Dispersion Management • First optically amplifier systems were not designed to support WDM – Transmission at or close to zero dispersion • Deep dispersion management: – NZDSF with SMF Suppressed nonlinear effects between WDM channels Further improvement: large effective area NZDSF (~ 70 m 2 ) – – 10 Gb/s bit rates, OOK signals, true WDM transmission • Dispersion slope compensated systems – Increased transmission bandwidth Large effective area SMF (~105 m 2 ) – Ref: A. Gnauck, et al; IEEE JLT, vol. 26, 2009, p1032 N.S. Bergano, IEEE JLT,” Vol. 23, 2005, p 4125
conference & convention enabling the next generation of networks & services NZDSF Dispersion Map Large Area Large Area NZDSF NZDSF NZDSF NZDSF SMF ~ 500 km ~ 500 km Large Area NZDSF 70 m 2 0.1ps/km -nm 2 55 m 2 0.07ps/km -nm 2 NZDSF SMF Dispersion Total Wavelength NZDSF Large Area NZDSF • True WDM map – Performance may vary with dispersion within the transmission band
conference & convention enabling the next generation of networks & services Dispersion Flattened Map D+ D- D+ D- D+ ~ 500 km ~ 500 km 75/110 m 2 D+ 25-35 m 2 D- D+ Total Dispersion Wavelength D- • Increased linearity – Performance equalized across transmission bandwidth
conference & convention enabling the next generation of networks & services 10G DPSK Transmission in NZDSF Dispersion Map 16 RZ-DPSK 15 Transmission simulation: 9000 km Ref: W. Anderson, et. al., 14 Q factor (dB) OFC 2005, OthC1 Large Large 13 Low dispersion dispersion dispersion 12 Experiments: 13000 km, Ref: J.-X. Cai., et. al., RZ-OOK 11 OFC 2004, PDP34 10 9 1535 1540 1545 1550 1555 1560 1565 Wavelength (nm) • Properly-built dispersion map optimizes performance
conference & convention enabling the next generation of networks & services 10G DPSK in Undersea Transmission – Success of Dispersion Management Modulation RZ-OOK RZ-DPSK format (10 Gb/s) (10 Gb/s) Channel 33 GHz 33 GHz spacing Fiber plant Dispersion DFF Flattened Fibers (DFF) Amplifier 45 км 75 км spacing System length 9000 км 12700 км • Combination 3dB in Rx sensitivity, better nonlinear tolerance in pulse overlapped regimes, and better FEC Very difficult to beat this performance at SE up to 0.4 bit/s/Hz
conference & convention enabling the next generation of networks & services The Need for High Spectral Efficiency Will Require Polarization Multiplexed Formats 15 42.8 Gb/s Pol.Mux.- RZ-DBPSK 13 Ref: J.-X. Cai et. al OFC’08, PDP4 Q-Factor [dB] 50x42.8 Gb/s, 5200 km, 66.7GHz channel spacing 11 150 km repeater spacing CSRZ-DBPSK 9 RZ-DQPSK 7 -6 -3 0 3 6 Pre-Emphasis [dB] • Polarization Multiplexed format shows superior performance – Higher nonlinear tolerance & higher spectral efficiency – Favors coherent polarization multiplexed transponders
conference & convention enabling the next generation of networks & services Coherent Detection with DSP Ref. A. Salamon, et al., MILCOM 03, M. Taylor, PTL 2004, no. 2, pp. 674–676 90 ° A/D Optical Transmission Hybrid A/D PBS LO DSP 90 ° Path A/D Optical Hybrid A/D • Coherent detection allows access to the signal field: – Polarization de-multiplexing of PDM signals – High spectral efficiency in excess of 1 bit/s/Hz – Digital signal processing at the receiver
conference & convention enabling the next generation of networks & services Dispersion Management with Coherent Technology • In-line dispersion compensation can be dropped with coherent 3 3 3 Optimized for Optimized for Rx 2 2 2 coherent coherent • No in-line dispersion Delta Q (dB) Delta Q (dB) Delta Q (dB) compensation reduces 1 1 1 nonlinear penalties and 0 0 0 improves OSNR • Very simple transmission line -1 -1 -1 design Legacy Legacy -2 -2 -2 Difficulty: >10 5 ps/nm need to -2 -2 -2 0 0 0 2 2 2 4 4 4 6 6 6 be compensated in DSP for Relative Launch Power (dB) Relative Launch Power (dB) Relative Launch Power (dB) the long undersea cases
conference & convention enabling the next generation of networks & services “Linear” Fibers are Important for Coherent Detection Systems • Transition from OOK to PSK with 3 dB better receiver sensitivity and better FEC resulted in reduction of required power per channel • Helped in managing nonlinearity • Transition to PDM modulation formats with 40G and 100G rates will result in higher required OSNR and power per channel • We’ll need more “linear” fibers
conference & convention enabling the next generation of networks & services Advanced Fiber Types Better span losses Better nonlinear tolerance A eff1 Smaller loss Performance target Performance target Performance Q(dB) Performance Q(dB) Higher loss A eff2 Difference in span loss (dB) (A eff1 /A eff2 )[dB] Channel power (dB) Channel power (dB) ( ) 10 log( / ) ( )( ) FOM in dB A A SpanLoss SpanLoss dB 1 2 1 2 eff eff
conference & convention enabling the next generation of networks & services Improved Fibers 50 km Spans 100 km Spans 180 180 170 170 0.17dB/km, 150 m 2 0.17dB/km, 150 m 2 160 160 150 150 140 140 130 130 FOM 2.5dB FOM 3.5dB 120 120 110 110 100 100 0.19dB/km, 105 m 2 0.19dB/km, 105 m 2 90 90 80 80 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.14 0.15 0.16 0.17 0.18 0.19 0.20 FOM ( in dB ) 10 log( A / A ) ( SpanLoss SpanLoss )( dB ) eff 1 eff 2 1 2
conference & convention enabling the next generation of networks & services The Push to Higher Spectral Efficiency: New Experimental Results • 96x100G over 10600 km (300% spectral efficiency) & 400% spectral efficiency over 4400 km • Short 52 km amplifier spacing (better performance) • New experimental transmission 12 Transmission distance at optimal power fiber (0.183 dB/km, 150 m 2 area) 11 Q-factor [dB] 300% SE • 100G on 33GHz (300%) 10 • 100G on 25GHz (400%) 400% SE 9 • Post-deadline paper 8 – OFC 2010 PDPB10 0 5000 10000 15000 Transmission Distance [km]
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