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Digital Signal Processing for 100G/400G Optical Fiber Connectivity Links

Eiselt, Nicklas; Vegas Olmos, Juan José; Tafur Monroy, Idelfonso

Publication date:2016

Document VersionPublisher's PDF, also known as Version of record

Link back to DTU Orbit

Citation (APA):Eiselt, N., Vegas Olmos, J. J., & Tafur Monroy, I. (2016). Digital Signal Processing for 100G/400G Optical FiberConnectivity Links. Poster session presented at Big Data Photonics Workshop 2016, Los Angeles, California,United States.

Digital Signal Processing for 100G/400G Optical Fiber Connectivity Links

Nicklas Eiselt1,2, J. J. Vegas Olmos1 and Idelfonso T. Monroy1

(1) Technical University of Denmark (DTU), Department of Photonics Engineering, Ørsteds Plads, Build. 343, DK-2800

(2) ADVA Optical Networking SE, Märzenquelle 1-3, 98617 Meiningen, Germany

niei@fotonik.dtu.dk

Experimental Setup

Acknolowledgement

Conclusion

Experimental Results @ 56 Gbit/s

Optical b2b performance Transmission over 80 km SSMF

Parameter Setup

Data Rate 56 Gb/s

Frequency 194.25 THz

DAC/ADC 84 GS/s

MZM LiNbO3, > 35 GHz bw

PIN/TIA 30 GHz bw

MUX/DEMUX 39 GHz bw

SSMF (80 km)

EDFA

VOA

OSA

MZM

DCF MUX DEMUX

DAC 84 GS/s

Noise Loading

ADC 84 GS/s

PIN/TIA

VOA

EDFA

Tx DSP PAM4/DMT

(offline)

VOA DCF

Rx DSP PAM4/DMT

(offline)

Four-level pulse amplitude modulation (PAM-4)

Discrete Multitone (DMT)

DSP

Data S/P

TS Mapping

P/S Cyclic Prefix

IFFT

Quantization Clipping

BER P/S

Equalizer Demapping

CP Remove FFT

TS Remove

Synchronisation S/P

Transmitter Receiver

deBruijn Mapping

Oversampling Level Adjust

Quantization Pre-EQ Shaping

FFE BER

Resampling Clock-Rec.

Normalization

Transmitter Receiver

1

2

3

4

5

6

1

22 24 26 28 30 32 34 36 38 40

- B

ER

OSNR [dB]

DSB-DMT

VSB-DMT

PAM-4

HD-FEC

Motivation – DWDM InterconnectionsLow-Cost Approach (Scale up from short reach)

• 400G direct detection

• 8x50G DWDM/ 4x100G WDM

8 x DMT @ 56 Gb/s

8 x PAM-4 @ 56 Gb/s

Several Tb/s link capacity, reach up to 100 km RX Low cost Low power consumption (Some) dispersion tolerance

TX Low cost Low power consumption

Wavelength range C-band, EDFA amplification Optical dispersion

compensation

Data rates multiples of 400G

DWDM

Estimated SNR of double sidband DMT (DSB-DMT) and vestigial sideband DMT (VSB-DMT) at optical b2b

Residual Dispersion & PAM-4

22

24

26

28

30

32

-250-200-150-100 -50 0 50 100 150 200 250 300

RO

SNR

@ B

ER=3

.8e

-3

CD [ps]

FFE 3 FFE 7 FFE 11

FFE 21 FFE 31

Required OSNR at the FEC-limit of 3.8e-3 vs. residual dispersion with different FFE tap count

Launch Power

Optimum launch power into 80 km SSMF using PAM-4: Where to put the DCF?

Optimum launch power into 80 km SSMF using DSB-DMT; DCF is not required!

2

3

4

5

6

7 28

30

32

34

36

38

40

422

-8 -6 -4 -2 0 2 4 6 8 10

OSN

R [

dB

]

- B

ER

Launch Power per Channel [dBm]

DCF Tx

DCF Rx

2

3

4 28

30

32

34

36

38

40

421

-4 -2 0 2 4 6 8 10

OSN

R [

dB

]

- B

ER

Launch Power per Channel [dBm]

DSB-DMT - 80 km

BER vs. OSNR for b2b-mode

1

2

3

4

5 6

1

22 24 26 28 30 32 34 36 38 40

- B

ER

OSNR [dB]

PAM-4 - 80 km

DSB-DMT - 80 km

VSB-DMT - 80 km

OSNR Performance

Estimated SNR of double sidband DMT (DSB-DMT) and vestigial sideband DMT (VSB-DMT) at 80 km SSMF

BER vs. OSNR at 80 km SSMF

• PAM-4 and vestigial sideband DMT show a lot of potential for a low-cost solution for next generation of inter-data center interconnections

• PAM-4 outperforms DSB-DMT and VSB-DMT in terms of required OSNR at the FEC-threshold for the b2b-case and even for 80 km SSMF

• DMT does not require any DCF 5 dB higher power margin for DMT compared to PAM-4

The work was in part funded by the European Commission in the Marie Curie projects ABACUS and FENDOI and by the German ministry of education and research (BMBF) in projects SASER-ADVAntage_NET and SpeeD under contracts 16BP12400 and 13N13744

PAM-4 Eye Diagrams used for transmission

After DAC After MZM

DMT Parameters

FFT length 1024

Oversampling 1.05

Max. used subcarriers 486

OFDC Frame 123 Symbols + 5 training symbols

Equalizer 1-tap, Decision-Directed

Bit & Powerloading Chow’s & Cioffi’s algorithm

Format HD-FEC OSNR b2b OSNR 80 km

PAM-4 3.8e-3 ~ 23.8 dB ~ 24.8 dB

DSB-DMT 3.8e-3 ~ 25.7 dB ~ 27.2 dB

VSB-DMT 3.8e-3 ~ 27 dB ~ 31 dB

Results

References [1] N. Eiselt, et al., „Experimental Comparison of 56 Gbit/s PAM-4 and DMT for Data Center Interconnect Applications“, Photonische Netze, 17. ITG Fachtagung, 2016, Leipzig