1 © 1999, Cisco Systems, Inc. IP over DWDM NANOG May 24, 1999 Larry McAdams

2 NANOG 5/24/99 Outline l Optical Transmission Fundamentals l DWDM Systems l IP over DWDM

3 NANOG 5/24/99 Its Analog Transmission Attenuation Dispersion Nonlinearity Waveform after 1000 kmTransmitted data waveform Reflectance

4 NANOG 5/24/99 Fiber Attenuation l Telecommunications industry uses two windows: 1310 & 1550 l 1550 window is preferred for long-haul applications u Less attenuation u Wider window u Optical amplifiers 1310 window 1550 window

5 NANOG 5/24/99 Fiber Dispersion Wavelength Dispersion ps/nm-km nm 1550nm Normal fiber Non-dispersion shifted fiber (NDSF) >95% of deployed plant Reduced dispersion fibers Dispersion shifted fiber (DSF) Non-zero dispersion shifted fibers (NZDSF)

6 NANOG 5/24/99 Dispersion l Dispersion causes the pulse to spread as it travels along the fiber l Chromatic dispersion is important for singlemode fiber u Depends on fiber type and laser used u Degradation scales as (data-rate) 2 l Modal dispersion limits use of multimode fiber to short distances Interference

7 NANOG 5/24/99 Polarization Mode Dispersion l Most severe in older fiber l Caused by several sources u Core shape u External stress u Material properties l Becomes an issue at OC-192

8 NANOG 5/24/99 Four-Wave Mixing (FWM) l Creates in-band crosstalk that can not be filtered l Problem increases geometrically with  Number of s  Spacing between s u Optical power level l Chromatic dispersion minimizes FWM

9 NANOG 5/24/99 Outline l Optical Transmission Fundamentals è DWDM Systems l IP over DWDM

10 NANOG 5/24/99 EDFAs Enable DWDM km Terminal Regenerator - 3R (Reamplify, Reshape and Retime) Terminal 120 km Terminal EDFA - 1R (Reamplify) Terminal EDFA amplifies all s Terminal

11 NANOG 5/24/99 EDFA Schematic EDFAs amplify all s in 1550 window simultaneously l Key performance parameters include u Saturation output power, noise figure, gain flatness/passband Pump Laser WDM Coupler WDM Coupler EDF DCF Optical Isolator 1480 Pump Laser Optical Filter Optical Isolator EDF

12 NANOG 5/24/99 DWDM System Design Amplify DWDM Filter Optical Combiner 15xx nm1310 nm Reamplify Reshape Retime Rx Tx 1310 nm Rx External Modulator Laser 15xx nm

13 NANOG 5/24/99 DWDM State-of-the-Art Data Rate l Point-to-point systems  40 x OC-48 deployed  16 x OC-192 deployed  160 x OC-192 announced l Configurable OADMs l Metro rings 1-10 Tbps per fiber is just around the corner!

14 NANOG 5/24/99 Outline l Optical Transmission Fundamentals l DWDM Systems è IP over DWDM

15 NANOG 5/24/99 Synchronization for IP over DWDM OC-48c Ethernet Gig-Ethernet Ethernet DS1 Point-to-point application Synchronization driven from router Router interface internal timed T1 OC-12c~~ ~ ~~ ~ OC-48c FIBER REGEN WDM OC-3c PRS SONET NETWORK OC-48c SONET network application Synchronization driven from network Router interface timed to PRS via Rx OC-48c

16 NANOG 5/24/99 Protection for IP over DWDM l Optical protection is not sufficient u Only protects transmission infrastructure l Layer 3 must provide path restoration u Opportunity for differentiation at the service level Optical Cloud

17 NANOG 5/24/99 Ciena 40 DWDM TX RC TX 500 km 100 km 25 dB RC TX RC GSR SR OC-48 PoS Error-free transmission over 20,000 kms without SONET regeneration TX RC GSR SR OC-48 PoS

18 NANOG 5/24/99 Nortel 16 DWDM and OC-192 Ring PRS Working Protect Lack of transponders prohibits direct connections at OC-192

19 NANOG 5/24/99 Conclusion - IP over DWDM l Transmission is an analog problem u Proprietary solutions abound l DWDM provides 100s Gbps of capacity u Transponders are required for an open architecture l Large scale deployments have been achieved u IP directly over DWDM is a reality