400 Gb/s & 1 Tb/s systems and fiber nonlinearities

Jacklyn D. Reis, PhD

Luis H. H. de Carvalho, BScCarolina Franciscangelis, BScVictor Parahyba, BScJúlio C. M. Diniz, MScDaniel M. Pataca, PhDFábio D. Simões, PhDNeil G. Gonzalez, PhDJúlio César R.F. de Oliveira, PhD

CPqD, Campinas, São Paulo, Brazil 23-25 February 2014Day 1

1. Fiber Nonlinear Limits

2. 1 Tb/s Super Channel

3. Field Trial with Nonlinear Compensation1. 1 Tb/s super channel 138 km

2. 112 Gb/s DP-QPSK 338 km

Outline

Nonlinear Limits in Optical Networking• Spectral efficiency times distance [bit/s/Hz]*km• Longer distance• Higher launch power• Higher optical channels• Linear Regime ASE• Nonlinear Regime Kerr nonlinearities

Essiambre et al, IEEE/OSA JLT’10.Nespola et al, OptEx’14.

Liu et al, IEEE SPMag’14

FIBER NONLINEARITIESPART I

Simulation model• Electrical + optical components for simulation super

channels / WDM systems implemented in Matlab• DSP normalization, CD equalizer (2x), LMS (2x), blind

phase search, synchronization, EVM/SNR

Maximum reach without amplification• If 7% HD FEC with 3.8x10-3 (SNR≈21.1 dB) Maximum

reach of 175 km with linear compensation only• Launch power ≈ 4 dBm (single polarization)

-21 dBm-11 dBm

-16 dBm

-6 dBm-1 dBm

+4 dBm

-1 dBmSignal+SPMSPMSPM

+19 dBm

Maximum reach without amplification

• Output optical spectrum for different input power (or transmission distance).

• Nonlinear generation from -21 (50 km-SSMF, top left) dBm up to 19 dBm (250 km, bottom right) launch power

-21 dBm-16 dBm-11 dBm-6 dBm+4 dBm+9 dBm+14 dBm

Maximum reach without amplification

• Considerations on launch power and receiver sensitivity• If receiver sensitivity is lower than -33 dBm, than the input power has

to increase

• Input power is upper bounded by fiber nonlinearities (~4 dBm up to 100 km – SSMF)

• To avoid increasing the launch power to support the loss budget, amplification prior the coherent receiver may be used to enhance sensitivity

Multi-carrier transmission at 50 GHz grid• Nx43 Gbaud – 64QAM at 50 GHz frequency grid after

100 km of SSMF (0.2 dB/km, 16 ps/nm/km, 1.3 W-1km-

1)

9

Multi-carrier transmission at 50 GHz grid• Intra-channel SPM versus inter-channel XPM at 50 GHz• From 1 Channel to 4 Channels 3 dB penalty on launch power BER = 10-3

due to XPM

1T SUPER CHANNELPART II

Optical pre-filtering

• Experimental setup• WDM scenario: 3 channels, 35-GHz spacing.• Optical filtering: Nyquist optical filter, bandwidth variation.• Use of conventional DSP, without ICI or ISI compensation.

• Results analysis• Measured performance at central channel (worst scenario).• Q-Penalty in reference to “non-filtered” 224G RZ PDM-16QAM.• Best performance @ 26GHz bandwidth (ICI vs ISI trade-off).

Test Channel

VOA

2x1

Neighbors

SC

OP

E (

40

-GS

/s)

(a)

EDFA

3 dB

Wa

ve

Sh

ap

er

Mod. RZPDM-16QAM

Mod. RZPDM-16QAM

LO Off

line

DS

P

(b)

ICR

Experimental Setup

Fig. 1: Experimental setup. (a) 1.12-Tb/s transmitter; (b) 224G RZ-PDM-16QAM optical eye and constellations; (c) 1.12-Tb/s spectrum in a 175-GHz flexi-grid WSS channel; (d) Recirculation loop; (e) DSP-Rx block diagram.

Back-to-back characterization (per-carrier)

• Measured performance @ 1e-3 BER• 224Gb/s RZ PDM-16QAM (Reference): 26 dB (6-dB implementation penalty).• Reference after filtering: 25.5 dB (0.5-dB matched filter improvement).• 1.12-Tb/s Superchannel (5-Carriers): 26.3 dB (0.8-dB multiplexing penalty).• 1.12-Tb/s after 5 ROADMs@175-GHz: 27.4 dB (1.1-dB penalty).

• Required OSNR @ FEC Limit: 3.8e-3 BER• 1.12-Tb/s Superchannel (5-Carriers): 23.3 dB.

Transmission results

Launch-Power after 700km

BER with NLC after 1000 km Transmission performance

OSNR performance (per-carrier) • Launch-Power test• Per-carrier investigation.• Optimum value: -1 dBm/carrier

• Transmission results• 700 km and 7 ROADM passes

• Using conventional DSP

• 1000 km and 10 ROADM passes

• Employing nonlinear compensation.

• OSNR performance• Without NLC

• After 700 km: 25.3 dB• Transmission penalty: 2 dB

• With NLC• After 1000 km: 23.9 dB• Transmission penalty: 0.6 dB

• Improvement of 1.4 dB in transmission penalty by employing NLC

• Transmission reach improved from 700 to 1000 km.

FIELD TRIALPART III

Field Trial: GIGA Network• Campinas to Jundiaí ~138 km• Campinas to São Paulo ~330 km

1 Tb/s Super Channel: 5 x 224 Gb/s DP-16QAM

RZ+PFDAC free

6 b/s/Hz SE (175 GHz grid)ECOC’13

1 Tb/s: 5 x 224 Gb/s DP-16QAM 138 km• BER Improvement at Optimal Power 3.5x

112 Gb/s: DP-QPSK 330 km• BER Improvement at Optimal Power 1.5x / 2.8x• Nonlinear tolerance 2 dB improvement w/o MLSE

Conclusions

• DSP plays a major role on high-speed optical networking

• Fiber nonlinear effects limit the launch power• Shorter capacity• Shorter distance

• Digital nonlinear compensation• At least 2 dB improvement on nonlinear tolerance• Network parameters in deployed fibers• Chip implementation is yet to appear

Obrigado!

www.cpqd.com.br