1. www.viewegteubner.de Vieweg+TeubnerPLUS Additional information to media of Vieweg+Teubner Verlags Elements of optical networking Megabit and Gigabit and Terrabit and ??? by Prof. Dr. V. Brückner

2. 1. The optical channel - DWDM 2. Limits by attenuation 3. Limits by dispersion Megabit and Gigabit and Terrabit and ???

3. kB/s MB/s GB/s 1 ms1 µs1 ns Digital Bit pattern transmitter TB/s I1I1 I2I2 I3I3 about 40 channels 10000 1 11 Dense Wavelength Division Multiplexing (DWDM) Bit duration

4. DWDM: the single optical channel: The optical channels (wavelength consideration) frequency f0f0 ΔfΔf 100% 50% wavelength λ0λ0 Δλ Line width wavelength

5. frequency f0f0 wavelength λ0λ0 The optical channels (wavelength consideration) DWDM: the single optical channel: Δλ1 pm line width wavelength

6. 3 optical channels: frequency 100 GHz 195.8 THz195.7 THz195.9 THz (193.1 + n. 0.1) THz ITU-T G.694.1 for 100 GHz: at λ = 1531.12 nm and Δf = 100 GHz -> Δλ = 0.75 nm wavelength 1531.12 nm1530.37 nm1531.87 nm 0.75 nm channel spacing Requirements to wavelength stability of lasers: ±2.5% (±0.02 nm)!!!!! The optical channels (wavelength consideration)

7. 3 optical channels + modulation: wavelength 1531.12 nm1530.37 nm1531.87 nm 0.75 nm channel spacing The optical channels (modulation) Optical Time Division Multiplexing (OTDM) Principle: Shuffling in time (different run times in glass fibers)

8. 3 optical channels + modulation: wavelength 1531.12 nm1530.37 nm1531.87 nm 0.75 nm channel spacing The optical channels (modulation) Equal length of time slots: Synchronous digital Hierarchie (SDH) Flexible length of time slots : Asynchronous Transfer Modus (ATM) STM levelBit rate STM-25639813,12 MBit/s STM- 649953,28 MBit/s STM- 162488,32 MBit/s STM- 4622,08 MBit/s STM- 1155,52 MBit/s Synchron Transport Moduls:

9. fiber 1 n MUXDEMUX 1 n WDM OTDM with WDM: The optical channels (modulation) Principle : Shuffling in time e.g. for STM-256 (40 GB/s) S 1 : 1, τ 1 < 10 ps S 2 : 1, τ 1 < 10 ps S m : 1, τ 1 < 10 ps... t m time slots a 25 ps = 1/40GBps... S1S1 S2S2 SmSm τ1τ1 τ1τ1 τ1τ1 Principle: Generation of a frame of m time slots, in total 40 GB/s (40 GBps) Transmission capacity n * 40 GB/s

10. 3 optical channels + modulation: wavelength 1531.12 nm1530.37 nm1531.87 nm 0.75 nm 40 GB/s ~ f M = 40 GHz (0.3 nm) Modulation with 40 GB/s (STM-256): channel spacing safety clearance Safety clearance: 0.15 nm The optical channels (modulation) Resulting spectrum: Side bands f 0 ± f M

11. Optical channels: scaling wavelength Present time: 40 channels - about 30 nm (40 GBps) = 1.6 TBps 1531.12 nm1501.87 nm future: 80 channels - about 60 nm (40 GBps) = 3.2 TBps 160 channels - about 120 nm ?? (40 GBps) = 6.4 TBps 320 channels - about 240 nm ???? (40 GBps) = 12.8 TBps The optical channels (wavelength + modulation)

12. Optical channels – conclusions: or: 40 channels - about 30 nm (40 GBps) = 1.6 TBps or: 80 channels - about 60 nm (20 GBps) = 1.6 TBps or: 20 channels - about 15 nm (80 GBps) = 1.6 TBps either: 10 channels - about 7.5 nm (160 GBps) = 1.6 TBps Transfer of a data rate of 1.6 TBps: Which way is better? Which problems arise? The optical channels (wavelength + modulation) Problem: low channel number -> higher channel distance -> technically less complicated higher bit rate -> shorter time slots -> technically more complicated (Dispersion) Problem: lower bit rate -> less dispersion influence -> technically less complicated higher channel number -> shorter channel distance -> techncally more complicated (demultiplexing) or

13. laser modulator MUXWDM DWDM glass fiber core 9 µm cladding 125 µm losses - attenuation The optical channels (limits by attenuation)

14. laser modulator MUX fiber The fiber: power in fibers P0P0 z P 100% 50% physics: powerengineering: level W, mWdB, dBm p0p0 z p -3dB attenuation in fibers (α): losses per kilometer (dB/km) The optical channels (limits by attenuation)

15. 70080090010001100120013001400150016001700 Wavelength [nm] 0,1 1 10 losses [dB/km] Rayleigh scattering OH absorption standard SMF AllWave TM Best values: 0.2 dB/km at 1500 nm IR absorption Si O O O H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H 2 nd 3d3d LS DWDM: 40 channels, 50 GHz distance H H vibrations The optical channels (limits by attenuation)

16. 70080090010001100120013001400150016001700 wavelength [nm] 0,1 1 10 losses [dB/km] 3d3d LS DWDM: 40 chanals, 50 GHz 200 nm Max. bandwidth in SSMF: 200 nm or 25 THz The optical channels (limits by attenuation)

17. laser modulator MUX fiber The fiber: amplification RecSTA LD optical data optical data electrical data IDID I0I0 3R regeneration: amplification (Re-amplification), clock reinstallation (Re-timing) and pulse formation (Re-shaping) Classical way: >> The optical channels (limits by attenuation)

18. 3R regeneration: amplification (Re-amplification), clock reinstallation (Re-timing) and pulse formation (Re-shaping) optical way: Optical amplification: Erbium-doped fiber amplifier EDFA Raman amplifier ROA Semiconductor optical amplifier SOA no Re-timing, no Re-shaping!!! The fiber: amplification laser modulator MUX fiber >> The optical channels (limits by attenuation)

19. kBit/s MBit/s GBit/s 1 ns Bit pattern Laser Modulator DWDM The optical channels (limits by dispersion)

20. ideal rect pulse time real rect pulse, 3, 5, 7 usw. time real, Gaussian pulse after a short glass fiber time broadened, Gauss-shaped pulse after dispersion in a long glass fiber p di s Influence of dispersion to a single Bit dis > p The optical channels (limits by dispersion)

21. L 0 = 0 L 1 > L 0 L 2 > L 1 L 3 > L 2 2 Bits 2 Bits ?? 1 oder 2 Bits ????? time The optical channels (limits by dispersion)

22. Dependent on The optical channels (limits by dispersion)

23. modal dispersion Modal Dispersion in SI-Fibers (MMF) Different runtime Δt g for all paths, because of different paths ways Δt g The optical channels (limits by dispersion)

24. modal dispersion modal dispersion in GI-Fibers (MMF) Nearly the same runtime for all paths, because different paths and velocities are compensated The optical channels (limits by dispersion)

25. Chromatic Dispersion (CD) = Material Dispersion + Waveguide Dispersion Different wavelengths in the LD-Spectrum have different transit times Light sources are not monochromatic, but have a finite broad spectrum t t 3 t 2 t 1 The optical channels (limits by dispersion)

26. P Material dispersion L 1 2 3 Selection of 3 wavelengths: 3 > 2 > 1 thus n 3 < n 2 < n 1 thus v 3 > v 2 > v 1 3 2 1 Path difference in Multi-Mode and Single-Mode fibers Spectral width -> t g by different propagation speeds n λ Dispersion The optical channels (limits by dispersion)

27. t g by different propagation speeds in core and cladding (in SMF only) L d 1 = 9 µm d 2 = 5µm< d 1 P x P x Situation: n K > n M thus v K < v M Wave guide dispersion The optical channels (limits by dispersion)

28. SMFDFFDSF index core D Chrom (ps/km*nm) SMF DSF DFF (µm) chromatic dispersion The optical channels (limits by dispersion)

29. bit pattern dispersion compensation pulse broadening (overlap of Bits) chromatic dispersion The optical channels (limits by dispersion)

30. dispersion compensating fiber 5 km DCF 40 km SMF Spleisses 40 km SMF 5 km DCF SMF 8 partsSMF + 1 part DCF DCF -300 D ps/km*nm -200 -100 0 +100 1.1 (µm) 1.31.51.7 compensation: DCF core n The optical channels (limits by dispersion)