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Evarist Palushani. DTU Fotonik , Department of Photonics Engineering, Technical University of Denmark, Building 343, 2800 Lyngby, Denmark epalu@fotonik.dtu.dk. Ph.D. in the NOSFERATU project. Outline. Project objectives Pulse shaping: Flat-top pulse generation:

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Presentation Transcript
slide1

Evarist Palushani

DTU Fotonik, Department of Photonics Engineering,

Technical University of Denmark, Building 343, 2800 Lyngby, Denmark

epalu@fotonik.dtu.dk

Ph.D. in the NOSFERATU project

slide2

Outline

  • Project objectives
  • Pulse shaping: Flat-top pulse generation:
    • Long Period Grating pulse shaper
    • Optical Fourier Transform technique
  • All-optical Retiming and Synchronization
    • Time Lens based Packet Synchronization
slide3

Project objectives

NOSFERATU:Non-linear optical switching for extremely high data rate communications

slide4

Project objectives 2

  • Optical Ethernet upgrade from futures 100 GE lines to 1 TE (Terabit Ethernet)
  • Definition of a network scenario
  • Development of techniques for network intelligence and efficient switching/routing
  • Investigation of optical effects and limitations for 1 TE Optical Time Division Multiplexing (OTDM)
  • Functionalities to be addressed, developed and investigated:
    • OTDM networking issues for optical 1 TE solutions
    • Stable 1 TE multiplexer
    • Pulse shaping for suitable terabit OTDM communications
    • Suitable nonlinear switches, for stable channel selection

Ph.D.

Ph.D.

Post Doc.

slide5

Outline

  • Project objectives
  • Pulse shaping: Flat-top pulse generation
    • Long Period Grating pulse shaper
    • Optical Fourier Transform technique
  • All-optical Retiming and Synchronization
    • Time Lens based Packet Synchronization
slide6

Pulse Shaping for Demux Optimisation

  • Flat-top pulses suggested for:
    • Polarisation-independent (PI)1 NOLM operation when:
      • Correct adjustment of control pulse power (Pctrl)
      • Correct adjustment of control polarisation
    • Time jitter tolerance in OTDM switches2

1H. Mulvad, “Polarization-Independent High-Speed Switching in a Standard Nonlinear Optical Loop Mirror”, OFC 2008, Paper OMN3

2L.K. Oxenløwe,``640 Gb/s Timing Jitter-Tolerant Data Processing Using a Long-Period Fiber-Grating-Based Flat-Top Pulse Shaper,‘’ IEEE J. Quantum Electronics, vol.14, pp. 566-572 (2008)

slide7

LPG1

LPG2

Input pulse

L

T

Long Period Grating : Pulse Shaper

L: spacing between filters

T: time delay between coupled modes

T= 400 fs

Gaussian input pulse

FWHM = 700 fs

Wavelength tuning determines pulse shape

slide8

640 Gbit/s PI demultiplexing in a NOLM

Polarisation scrambler on the data

slide9

Outline

  • Project objectives
  • Pulse shaping: Flat-top pulse generation
    • Long Period Grating pulse shaper
    • Optical Fourier Transform technique
  • All-optical Retiming and Synchronization
    • Time Lens based Packet Synchronization
slide10

C

j-mod

Dacc

Optical Fourier Transform Technique (OFT): Pulse Shaper

A0

A1

C : time lens

linear chirp

L : fiber length

β2: dispersion

temporal

F1

F0

spectral

for

where

Required combination of phase modulator and dispersive element

Mapping of the spectrum shape into the time domain

Possible to taylor the length of the output pulse by changing C

slide11

OFT without Phase Modulation

a0

a1

f0

f1

for

Far field image yields optical waveform as the OFT of input

Need wide input spectrum/narrow pulse, since no phase modulation

Here: SPM spectral broadening and shaping by broad band-pass optical fiter

slide12

simulated

xcorrelator

measured

power [a.u.]

+

autocorrelator

16 SMF

8 m SMF for chirp compensation

power [a.u.]

time [ps]

Result 1: Frequency-Time Information Mapping

power [a.u.]

FWHM=15 nm

power [dBm]

Good agreement between predicted and measured pulse shapes

wavelength [nm]

slide13

Result 2: Narrow flat-top gating pulse generation

Pre-transform at L = 10 m SMF of very flat m~2 spectrum

Mix between m=2 (pulse top) and m=1 (tails)

Flat-top pulse shape with FWHM 1.6 ps ~ 640 Gbit/s timeslot

slide14

320 Gbit/s Demultiplexing: Timing tolerance

  • The flat-top pulse (gating signal) is used in a FWM demultiplexing experiment
  • 320 Gbit/s data signal used as pump
  • Flat top pulses (previous slide) used as probe

Pre-transform flat-top pulse able to FWM-demux 160-320 Gbit/s

Simultaneous switching window and timing tolerance measured

400 fs timing tolerance ~ switching window flat top

14

slide15

Outline

  • Project objectives
  • Pulse shaping: Flat-top pulse generation:
    • Long Period Grating pulse shaper
    • Optical Fourier Transform technique
  • All-optical Retiming and Synchronization
    • Time Lens based Packet Synchronization
slide16

All-optical Retiming and Synchronization

From asynchronous 10 GE NRZ to synchronous 1 TE RZ

slide17

Time Lens based Packet Synchronization

Δf=fin-fL

Nominal speed: fin

Local clock: fL

slide18

Results: Time Lens based Packet Synchronization

Δf= 200 kHz

Usynch. packets

Synch. 5120 bits/packet

Synch. 12144 bits/packet