Fotonica in SURFnet6 Wouter Huisman Netwerkdiensten, SURFnet

1 Agenda -Fibers & Infra -Module Blocks -Transmitter, Receivers, Amplifiers, Filters -Systems -Single channel lasers/receivers -Amplified single channel -C/DWDM -DCM, PMD, FEC -Latest technology -SURFnet’s network

2 Optical fiber - Historical perspective -Internal reflection known from 19 th century (John Tyndall, 1870) -Early fibers with cladding extremely lossy ~1000dB/km (1960) -Today fiber loss ~0.2dB/km Refractive index N1(water) > N2 (air)

3 Fiber basics -Multi Mode (MM) -Intra office -SX -max 500m -Single Mode (SM) -LX, ZX, C/DWDM 5-10µm µm Core Cladding

4 Fiber Loss (SM) -Fiber loss is wavelength dependent, minimum is around 1550nm 1310nm1470nm-1620nm

5 Fiber plant layout Equipment POP Splice Handhole Patching at ODF MMR ~4km

6 Fiber Plant test Basic paramaters: - Length - Loss - Reflection OTDR (optical time domain reflectometer)

7 10Gb/s optical transmitter technologies DFB External Modulation - DM-DFB (Directly Modulated Distributed Feed Back laser) Cheap, small, low power consumption Chirped, i.e. different wavelength during “ones” and “zeros” which leads to a wide optical spectrum and associated transmission impairments Used for short reach transmission {0,1,1,0,1,1,…,0,1,0} DFB {0,1,1,0,1,1,…,0,1,0} Mach-Zehnder LiNbO3 modulator External Modulation - CW-DFB (Continuous Wave DFB laser) and MZ (Mach-Zehnder) combination Expensive, relatively large, high-power drivers (high power consumption) Excellent performance Typically used for DWDM (Dense Wavelength Division Multiplexing)

8 Typical optical receiver setup preampAGC CLK decision circuit (A)PD P rec (dBm) BER P sens data

9 Traditional optical fiber transmission systems -Combination of transmitter and receiver connected directly to dark fiber -Typical distance is max 100km -150Mb/s -2.5Gb/s TxRx P T (dBm)P R (dBm) Transmission fiber α (dB/km) Transmission distance = (P T -P R ) / α (km)

10 3R regeneration - OEO Transmitter – Receiver = 3R -Re-amplification -Re-timing -Re-shaping TxRxTxRxTxRx

11 EDFAs (Erbium Doped Fiber Amplifiers) Fiber doped with Er 3+ ions be excited by 980nm or 1480nm photons Spontaneous emission generates noise Excited state Erbium ions can be stimulated to decay to ground state via stimulated emission by a 1550nm signal Pump laser Incoming Outgoing

12 Single Channel System with amplifiers TxRx OA Pre and Post Amplifiers allow for longer single span Systems upto 240km -150Mb/s -2.5Gb/s Tx OLA OA Rx OA OLA

13 Wavelength Division Multiplexing (C/DWDM) - WDM filters, passive device - Muxing coloured wavelength - Spacing between ’s determines the number of channel per fiber - SURFnet’s DWDM supports 10Gb/s

14 DWDM System OADM Node Mux Terminal NodeAMP Node OEO … Mux OEO … DCF OEO … … DCF Demux Terminal Node OEO Typically 80 channels spaced at 100GHz using C and L band Each channel operating at 10Gb/s, thus 800Gb/s per fiber Limited Optical Add and Drop for point-to-point optical lightpaths

15 Chromatic Dispersion -Typical value dispersion (D) 17ps/nm*km Transmission Rate Spectral Width (F) Bitperiod(T b) Max distance (km) 2.5Gb/s0.0254x Gb/s0.11x Gb/s0.42.5x T ~ bitperiod L = Tb/  F*D 10Gb/s FF

16 Chromatic Dispersion After 120km transmission Speed of Light is Wavelength dependent: Chromatic dispersion affects pulse shape Optical pulse shape at transmitter output Tx 120km standard SMF D=17.8 ps/nm km Rx OA ƒ 120km-10Gb/s system configuration r b = 10Gb/s c = 1557nm OA

17 z=0km z=5000km D=-87500ps/nm z=0km z=5000km D=+87500ps/nm dispersion compensation off dispersion compensation on eDCM DFB+MZ Rx {0,1,1,0,1,1,…,0,1,0} Total 5000km standard transmission fiber H(f)  h -1 (t) OA 12 No more need for dispersion compensation via DCFs (Dispersion Compensating Fibers)!!

18 PMD

19 FEC -Forward Error Correction -Technique to improve bit error rate resulting better P receiver -Adding FEC increases bitrate  worse P receiver P rec (dBm) BER P sens FEC on Parity check indicates the single error bit

20 New developments -40Gb/s and 100Gb/s -QPSK/QAM 40G over 10Gb/s From Static to Dynamic: -MEMS – Switchable mirrors -Dynamic WDM -eDCM -Tunable lasers -Tunable filters -DRAC

21 Layer 0 Evolution Advanced FEC Advanced Signal Processing Higher Spectral Efficiency (QPSK/QAM) Remove Raman, Increase Performance Remove DCMs & Amps, Increase PMD Tolerance, Eliminate complex engineering rules (esp. OADM) 4x Capacity per Line and 40G Service Support OADM Node Mux Terminal NodeAMP Node OEO … Mux OEO … DCF OEO … … DCF Demux Terminal Node Raman OEO Mux OEO … … Demux OEO ROADM Node Terminal NodeAMP NodeTerminal Node

22 Dynamic Networking ROADM SMF-28 E-LEAF TWc ROADM

23 SURFnet6 third generation DWDM 10Gb/s per channel 50GHz channel spacing wavelength locking optical add/drop forward error correction dispersion compensation C-band, can be upgraded to add L-band

24 Thanks!