masataka nakazawa 　（中澤　正隆） research institute of electrical communication...

Masataka Nakazawa 　（中澤　正隆）

Research Institute of Electrical Communication （電気通信研究所）

Tohoku University （東北大學）2-1-1 Katahira, Aoba-ku, Sendai-shi, 980-8577 Japan

Advanced optical fiber technologyfor high-speed optical communication

Advanced optical fiber technologyfor high-speed optical communication

台湾中山大學　 Seminar高雄 , Dec., 6th, 2007

Advanced photonic networkAdvanced photonic network

IDC, ISP

Core node

Edge node

ISP

■ High speed/high capacitytransport system

・ OTDM / ETDM・ High capacity WDM・ Multi-wavelength processing Recently 100 Gbit/s ETDM is feasible

○Mode-locked lasers○Pulse compression/reshaping devices○Dispersion/PMD compensation devices○Ultrafast demultiplexing (NOLM, SMZ)○Optical 3R regenerator/Adaptive optical equalizer

■ Ultrafast photonic devices

■ Networking devices・ Wavelength routing・ Optical packet routing・ Optical switching (OXC, Burst, Packet)○OADM(FBG, AWG, Tunable filters)・ Optical header recognition・ Optical buffer memory○Wavelength conversion/Tunable optical 　 source

Fiber key technologies for ultrafast optical transmission Fiber key technologies for ultrafast optical transmission

(1) Ultrashort optical pulse generation in the pico-femtosecond region• Pulse generation using mode-locked lasers/high-speed modulation• Pulse compression using DF-DDF• Pedestal reduction of compressed pulses using DI-NOLM

(2) Compensation of the total dispersion of a transmission line• Third- and fourth-order dispersion compensation

(3) Ultrafast demultiplexing• Ultrafast NOLM with 1 ps switching window

In ultrahigh-speed systems at > 160 Gbit/s, fiber devices are widely used.

Advantages of fiber devices are

• Ultrafast response speed of 10 fs• Low loss Excellent figure of merit• Ultra wide band (800-1600 nm)• Low noise• High reliability

OutlineOutline

(1) Optical sources

(2) Pulse compression and reshaping

(3) Transmission line• Dispersion management • Nonlinear fiber effects• PCF and PBF and their applications

(4) Demultiplexing

(5) A new transmission scheme using optical Fourier transformation / Parabolic pulse generation

(6) Summary

Setup for the generation of 1.28 Tbit/s signal

Setup for the generation of 10 GHz clock light

70 km transmission line

9

1

EDFA

LN (AM)PC

BPF 1 nm

Clock extraction circuit

10 GHz

High power EDFA

Regeneratively mode-locked fiber laser

PLC MUX

640 Gbit/s

10 Gbit/s

LNPC PC

High power EDFA

Transmission Fiber

PC

DF-DDFHigh power EDFA

DI-NOLM

SMF

DFF

PC

DCF

EDFA BPF 1 nm

1

9BPF 3 nm

LD (cw)

Clock light

1.28 Tbit/s signal

clock = 1542 nm)

PC PBS

70 km

PC

LN (PM)

High power EDFA

SMF RDFBPF 15 nm

PBS

Optical Delay

Pre-chirping unit

= 1544 nm)

Setup for the demultiplexing of 1.28Tbit/s OTDM signal to 10 Gbit/s

(450 m)

NOLM Control IN

Walk-off free, dispersion-flattened NOLM

BPF 10 nm

( = 1556 nm)

PC

10 GHz

PLL mode-locked fiber laser

PCBPF 15 nm

High power EDFA

Transmitted 1.28 Tbit/s signal


Isolator

EDFA

BPF 1 nm

BPF 1 nm

9

1640 Gbit/s

PC

High power EDFA Autocorrelator

PBS ATT

ED

EDFA

PD

Sampling oscilloscope

High power EDFA

= 1533 nm)

1.28 Tbit/s OTDM transmission using advanced fiber technologies


M. Nakazawa et al., Electron. Lett., vol. 24, 2027 (2000).

Single-channel 1.28 Tbit/s and 2.56 Tbit/s DQPSK transmission

Single-channel 1.28 Tbit/s and 2.56 Tbit/s DQPSK transmission

H. G. Weber et al., Electron. Lett., vol. 42, 178 (2006).

10~40 GHz MLFL and MLLD10~40 GHz MLFL and MLLD

40 GHz ClockExtractionCircuit

WDMCoupler

PM-EDF

PM-DSF

PZT

Coupler

Coupler

Isolator

Optical filter

IntensityModulator

Amp

Phase Controller

Synthesizer DBM

Feedback Circuit

High VoltageController

Phase-locked-loop (PLL)

StabilizationRegeneratively

Mode-locked Loop

(Soliton Effect)

40 GHz Microwave Output

1.48 m LD

40 GHz, ps Optical Output

Electro-AbsorptionModulator

Gain DBR

R = 10 %R = 30 %

Cavity length = 3.8 mm

InGaAsP

0.7 mW

90 mA40 GHz

(2x104 harmonics)

Phase controller

1.48 m LD

Filter

Intensity modulator

Isolator


PM-EDF

PM-DSF

Optical output pulses　

PZT

(70 m)

M. Nakazawa et al., Electron. Lett., 30, 1603 (1994)

(15 m)

Regeneratively and harmonically mode-locked fiber laser

Regeneratively and harmonically mode-locked fiber laser

Frequency

frep= 40 GHz

fFSR= 2 MHz

A B

ff

Optical filterTime t

Inte

nsi

ty

|E|2

A B

t t

f f

SPM

M. Nakazawa et al., Electron. Lett., vol. 32, pp. 461-462, Feb. (1996).

Output pulse characteristics at 40 GHzOutput pulse characteristics at 40 GHz

Optical spectrumAutocorrelation waveform 40 GHz clock spectrum

-100

-80

-60

-40

-20

0

39.5 39.52

Inte

nsity

[dB

m]

Frequency [GHz]

0

0.2

0.4

0.6

0.8

1

1.2

-4 -3 -2 -1 0 1 2 3 4

Inte

nsity

[a.

u.]

Time [ps]

1.4 ps

-80

-60

-40

-20

0

20

1555 1560 1565In

tens

ity

[dB

]Wavelength [nm]

2.2 nm(273 GHz)

Time-bandwidth product = 0.36(Nearly transform-limited sech pulse)

Line

ar s

cale

[a.

u.]

Resolution: 1 kHz

1 kHz

10 kHz/div

Features:(1) Transform-limited picosecond pulse(2) Symmetric comb profile(3) Ultranarrow linewidth(4) Ultrastable repetition rate(5) 1~3 mW Output (easy amp. with EDFA)

OutlineOutline

(1) Optical sources


(3) Transmission line• Dispersion management• Nonlinear fiber effects• PCF and PBF and their applications

(4) Demultiplexing


(6) Summary

Adiabatic soliton compression

• Pulse width can be compressed when D is adiabatically decreased as a function of distance z.

• 3 ps pulses can be compressed to < 100 fs at 10 GHz.

Pulse compression using a dispersion decreasing fiber (DDF)

Pulse compression using a dispersion decreasing fiber (DDF)

D : GVD : pulse width

Soliton energy

GVD

10 ps/nm/km

0.1 ps/nm/km

E D

z

= 3 ps

< 100 fs

Wavelength tunable femtosecond pulse compressionusing a dispersion-flattened DDF

Wavelength tunable femtosecond pulse compressionusing a dispersion-flattened DDF

K. Tamura and M. Nakazawa, PTL, 11, 319 (1999).

Pedestal elimination using a dispersion-imbalancednonlinear optical loop mirror (DI-NOLM)

Pedestal elimination using a dispersion-imbalancednonlinear optical loop mirror (DI-NOLM)

K. Tamura and M. Nakazawa, PTL, 11, 230 (1999).

54 fs pulse generation in a polarization-maintainingdispersion-flattened dispersion decreasing fiber

54 fs pulse generation in a polarization-maintainingdispersion-flattened dispersion decreasing fiber

Problem in ultrahigh-speed pulse compressionProblem in ultrahigh-speed pulse compression

Output power from DDF varied randomly due to SBS, resulting in unstable compression.

Output waveforms(a) Compressed (b) Uncompressed

0.4

0.8

1.2

1.6

2

2.4

2.8

-4 -2 0 2 4

Inte

nsi

ty [

a.u.

]

Time [ps]

圧縮時

0.4

0.8

1.2

1.6

2

2.4

2.8

-4 -2 0 2 4

Inte

nsi

ty [

a.u.

]

Time [ps]

非圧縮時

Optical spectrum of backscattered light from DDF

SBS

0.09 nm (11 GHz)

Source spectrum leaked through the circulator

DDFEDFA

40 GHz, 1.7 psMode-locked Fiber Laser(MLFL) Optical Spectrum

AnalyzerLinewidth ~1 kHz

In ultrahigh-speed pulse compression that exceeds 40 GHz, the optical power of each longitudinal mode increases, and stimulated Brillouin scattering (SBS) occurs.

OutlineOutline

(1) Optical sources



(4) Demultiplexing


(6) Summary

Femtosecond pulse propagation in a dispersion-managed fiber

Femtosecond pulse propagation in a dispersion-managed fiber

0 km

30 km

0 km

30 km

0.1 km

29.99 km

Time

GV

D

25 km 5 km

DSCFSMF

D+Positive Disp.Positive Slope

D-Negative Disp.Negative Slope

Dispersion management Line (DML)Each portion; Non-zero dispersion (For FWM suppression)Total; Zero and flat dispersion(For wide-band transmission)

0

D-

Wavelength

D+Total

+D [ps/nm/km]

Trade-off between D. slope and Aeff in SLA+IDF

D+ D-

Power Nonlinearity

L

K.Mukasa et al., ECOC97 Proceeding, Mo3C-127 (1997)

Dispersion-managed transmission lineDispersion-managed transmission line

Inte

nsity

Time 1.6 ps/div

Inte

nsity

Time 1.6 ps/div

Inte

nsity

Time 1.6 ps/div

Inte

nsity

Time 1.6 ps/div

Pulse waveformsPulse waveforms

1.28 Tbit/s – 0 km (Pre-Chirped) 1.28 Tbit/s – 70 km

After Polarization Demultiplexing

(a) (b)

(c) (d)

Nonlinear effects in fibers and their applicationsNonlinear effects in fibers and their applications

SPM• pulse compression • supercontinuum generation• intensity filter

XPM

• all-optical switch (demultiplexer, regenerator)• wavelength converter

FWM• parametric amplifier • optical limiter • wavelength converter• demultiplexer • phase conjugator

SRS• amplifier • modulator

SBS• amplifier • narrowband filter • slow light

• soliton effect

Gain Spectrum of SRS

dIs

dzgRIpIs sIs

Gain is proportional topump intensity.

pump

stimulatedemission

stimulatedabsorption

F. Forghieri et al., Optical Fiber Telecommunications IIIA ,I. P. Kaminow and T. L. Koch Eds., Academic Press (1997).

Stimulated Raman Scattering (SRS)Stimulated Raman Scattering (SRS)

M. Nakazawa, Appl. Phys. Lett., 46, 628 (1985).

Frequency (cm-1)

Gai

n c

oef

fici

ent

10.2 THz, 84 nm (1536-1620nm)

0

5

10

15

1540 1560 1580 1600 1620

Gai

n (d

B)

Wavelength (nm)

Raman P-EDFA

Total

The largest bandwidth of 10.2 THz was achieved using P-EDFA

gain-blocks and a two- pumped Raman amplifier gain-blockBy courtesy of NTTMasuda et al., OFC2007

Gain-flattened 10.2-THz continuous bandwidth inline optical repeater

Gain-flattened 10.2-THz continuous bandwidth inline optical repeater

Parametric amplifiers based on FWMParametric amplifiers based on FWM• Single-pump amplifier

HNLF (200+200+100m)=11.4 W-1 km-1

maximum internal fiber gain=49dB with cw pump

J. Hansryd and P. A. AndreksonIEEE PTL 13, 194 (2001).

HNLF (20m)

Gain>10dB is obtained for200nm signal wavelengthrange with pulsed pump

M.-C. Ho et al., J. LT 19, 977 (2001)

=18 W-1 km-1

• Two-pump amplifier• broadband• polarization-independent operation

is obtained with orthogonal polarization pumps

K. K. Y. Wong et al., PTL 14,911 (2002).

HNLF (1 km) = 17 W-1km-1

Photonic crystal fiber (PCF)

Comb based on a mode-locked laser

Broadened comb with PCF

Spectral broadening of an optical comb using PCFSpectral broadening of an optical comb using PCF

By courtesy of AIST

J. K. Ranka et al., Opt. Lett., vol. 25, pp. 25-27 (2000).

Ti:Sapphire laser

Octave-spanning comb using femtosecond fiber laser and HNLF

Octave-spanning comb using femtosecond fiber laser and HNLF

10-5

10-4

10-3

10-2

10-1

100

200018001600140012001000Wavelength (nm)

20401020

Nor

m.s

pect

ral p

ower

(dB

)

Oscillator

Octave-spanning comb

-10

0

-30

-20

-40

-50

•frep: 54 MHz•Pulse width: 90 fs•Center wavelength: 1560 nm•Average power: 40-50 mW

HNLF

•Length: 20 cm•Zero dispersion wavelength: 1447 nm•nonlinear coefficient : 21 /W/km

OSAAmplifier

Isolator

Polarizer+controller

WDMcoupler

Er:fiber

Pump

Oscillator

Coupler

Drum PZT

M. Nakazawa, et al. Electron. Lett. 29, 1327, 1993

H. Inaba et al., Opt. Express, 14, 5223 (2006).

The Fourier transformation between time and frequency axesf(n) = nfrep + fCEO

fCEO = (/2)frep : fCEO is obtained by one octave method.

Ref.: Th. Udem et al., Phy. Rev. Lett., 82, 3568 (1999).

Carrier envelope phase

n

f(n)fCEOfrep

Carrier envelope offset (fCEO)Carrier envelope offset (fCEO)

45dB at 100 kHz RBW

fCEO frep - fCEO

frep

Carrier envelope offset beat

Continuous measurement over 1 week!H. Inaba et al., Opt. Exp. 14, 5223 (2006).

Long-term frequency measurement of iodine stabilized Nd:YAG laser

Long-term frequency measurement of iodine stabilized Nd:YAG laser

By courtesy of AIST

Nonlinear optical properties of SWCNTNonlinear optical properties of SWCNT

[1] Y. –C. Chen, et al., Appl. Phys. Lett., vol. 81, 975 (2002). [2] Y. Sakakibara et al., Japan patent 2001-320383.

Applications: • Pulse shaping• ASE noise reduction• Passively mode-locked laser

SWCNT (Single-Wall Carbon Nano Tube)

• Saturable absorption effects in infrared wavelengths• Recovery time < 1 ps

Possibility of simple, low cost, ultrahigh-speed nonlinear optical material in the 1.5 m band

SWCNT

Passively mode-locked fiber laser with SWNT/PMMA as a saturable absorber

Passively mode-locked fiber laser with SWNT/PMMA as a saturable absorber

Cavity length: 10.3 m

Optical output

PM optical isolator

Polarizationcontroller

PM coupler

Focal Point Diameter: 10 m

Collimator CollimatorLens Lens

PMMA/SWNT

Z-axis movable stage

PM optical isolatorEDFA

PMMA with SWNT

SWNT: produced by HiPCO methodSWNT concentration: 500 ppm

1550 nm

0

20

40

60

80

100

120

1000 1500 2000 2500Wavelength [nm]

Ab

sorb

ance

[%

] SWNT/PMMA

SWNT

SWNT (S1 absorption)

Linear absorption spectraM. Nakazawa et al., Opt. Lett., 31, 915 (2006).

Pump power: 60.3 mW

Optical spectrumAutocorrelation waveform

FWHM = 317 fs (sech)

Laser output characteristicsLaser output characteristics

Time-bandwidth product = 0.26Output power = 5.2 mWRepetition rate = 19.4 MHz

- 1.5 - 1.0 - 0.5 0.0 0.5 1.0 1.50.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

tSHG

=492 fsec

tFWHM

=317 fsec

SH

G I

nten

sity

[a.

u.]

Time Delay [ps]1540 1550 1560 1570 1580

- 80

- 70

- 60

- 50

- 40

- 30

Δ λ =6.6 nm

Inte

nsit

y [d

Bm

]

Wavelength[nm]

Classification of photonic crystal fibersClassification of photonic crystal fibers

Dispersion characteristics of PCFDispersion characteristics of PCF

Wavelength (m)

GVD

Bulk Silica (material dispersion)

0.6 0.8 1 1.2 1.4

0

−

+

PCF

Strongly guiding Air-silica(structural dispersion)

1.6

(a)

1.55 m (0.2 dB/km)Long distanceInGaAsP / InGaAs pin

0.8 m (6 dB/km)Short distanceGaAlAs / Si

1.3 m (0.4 dB/km)Medium distanceFTTHInGaAsP / InGaAs pin

Large d/

Medium d/

Small d/

Wavelength (m)

GVD

0.6 0.8 1 1.2 1.4 1.6

−

+

(b)

・ Conventional fiber (doped core fiber) structural dispersion < 0・ Zero dispersion wavelength > 1.28 m

d

10 Gb/s x 4ch WDM transmission at 850 nm using PCF10 Gb/s x 4ch WDM transmission at 850 nm using PCF

VCSEL1

LN modulator10 Gb/s, NRZ

Photonic crystal fiber 5 km

Bit error rate

Eye diagram and optical spectrum (Ch.1)

Light sourcein the 800 nm region

VCSEL2

VCSEL3

VCSEL4

WDMMUX

Opticalamplifier(EDFFA)

Optical amplifier(EDFFA) WDM

DEMUX

Si-APD BERT

AW

G

AW

G

VCSEL: Vertical Cavity Surface Emitting LaserAWG: Arrayed Waveguide GratingEDFFA: Erbium-Doped Fluoride Fiber AmplifierSi-APD: Silicon Avalanche Photo DiodeBERT: Bit Error Rate Tester

20 ps/div 850 851 852 853 854

光出

力 (

10

dB

/div

)

波長 (nm)

21 dB

Wavelength (nm)

10 d

B/d

iv

3

4

5

6

7

8

910

-20 -19 -18 -17 -16 -15 -14 -13

0 km5 km 1チャネル5 km 2チャネル5 km 3チャネル5 km 4チャネル

log

(B

ER

)

受光パワー (dBm)

12

-

-

-

-

-

--

-

-

Received optical power (dBm)

Channel 1Channel 2Channel 3Channel 4

• 10 Gbit/s-2 km transmission was also achieved without EDFFA. • 40 Gbit/s-2 km transmission was also demonstrated.

[1] Y. Oikawa et al., Photon. Technol Lett, 19, 613 (2007).[2] H. Hasegawa et al., Electron. Lett., 43, 117 (2007).[3] H. Hasegawa et al., Electron. Lett., 43, 642 (2007).

Air hole pitch3.4 mAir hole diameter: 1.2 mMode field diameter: 5.3 mTransmission loss: 5.2 dB/kmDispersion: -62.8 ps/nm/km

All-fiber acetylene (C2H2) gas cell using PBFAll-fiber acetylene (C2H2) gas cell using PBF

Splice with SMF

End view cleaved from a few mm from the splice

F. Benabid et al., Nature, vol.434, 488 (2005).

Application・ Frequency standard・ Compact frequency-stabilized laser・ Interaction between light and atom

Transmission spectrum

1 Gsymbol/s, 64 coherent QAM optical transmission[1] 1 Gsymbol/s, 64 coherent QAM optical transmission[1]

QAMModulator

OFS

I

Q Optical Filter ( ～ 5nm)

DSF 75 km

DSF 75 km

EDFA PC2

PC1

C2H2 Frequency-Stabilized Fiber Laser[2]

(fOFS =2.5 GHz)

Attenuator

A/D Digital Signal

Processor

PD

Synthesizer

(fsyn= 1.5 GHz)

FeedbackCircuit

LocalOscillator

DBM

IF signalfIF=fsyn+fOFS=4 GHz

(Tunable Fiber Laser)

PC6PC5

PD

OFS ： Optical frequency shifterEDFA: Erbium-doped fiber amplifierDSF: Dispersion-shifted fiberPC: Polarization controllerPol: PolarizerPD: Photo-detectorDBM: Double balanced mixer

PC4 Pol

Arbitrary WaveformGenerator

PC3

｜ fOFS- fLO ｜ =fsyn

Pilot signal

EDFA

EDFA

EDFA

EDFA

⊥

//

⊥, //

// //

//

⊥

Synthesizer

FBG

Lock-inamplifier

Feedbackcircuit

C2H2 cell

PDLN modulator

High voltage controller

Coupler

Laser output

WDM coupler

90/10 coupler

PZT

EDF

Circulator

FBG

MLP

Cavity length ~ 4 m(FSR= 49.0 MHz)

Feedbackcircuit

[1] J. Hongo et al., Photon. Technol. Lett., 19, 638 (2007).

[2] K. Kasai et al., OFC2006, OWM4

1.48 m LD

-40

-35

-30

-25

-20

-15

-10

-5

0

-12 -8 -4 0 4 8 12

Refle

ctan

ce [dB

]

Optical frequency [GHz]

Maximum reflectance 65 %

Linewidth1.3 GHz

Side lobe suppression 13 dB

Center wavelength1538.21 nm

Measured reflection spectrum

Reflection spectrum of PM FBG filterReflection spectrum of PM FBG filter

A. Suzuki et al., IEICE ELEX, vol. 3, 469 (2006).

Experimental results for 1 Gsymbol/s, 64 QAM transmission over 150 km

Experimental results for 1 Gsymbol/s, 64 QAM transmission over 150 km

Q

I

Q

I

3 dB

Bit Error Rate characteristics

-3410-5

10-4

10-3

-32 -30 -28 -2610-5

10-4

10-3

-34 -32 -30 -28 -26

Bit

err

or

rate

Received power [dBm]

Transmission power: - 5 dBm

Back-to-backAfter 150 km transmission

Received Power [dBm]

Bit

Err

or

Rat

e

Constellationmap

Eye pattern (I)

Eye pattern (Q)

(a)Back-to-back (Received power: -27 dBm)

(b)After 150 km transmission (Received power: -24 dBm)

-1 +1 0 Q symbol

-1 +1 0 I symbol

-1 +1 0 I symbol

-1 +1 0 I symbol

-1 +1 0 Q symbol

-1 +1 0 Q symbol

Q

I

Q

I

Q

I

Experimental result for polarization-multiplexed 1 Gsymbol/s, 128 QAM (14 Gbit/s) transmission over 160 km

Experimental result for polarization-multiplexed 1 Gsymbol/s, 128 QAM (14 Gbit/s) transmission over 160 km

Constellation diagram

Eye pattern (I)

Eye pattern (Q)

(a) Back-to-back(Received power:

-29.5 dBm)

(b) 160 km transmission for orthogonal data

(Received power: -26.5 dBm)

(c) 160 km transmission for parallel data

(Received power: -26.5 dBm)

OutlineOutline

(1) Optical sources



(4) Demultiplexing


(6) Summary

Setup for the generation of 1.28 Tbit/s signal

Setup for the generation of 10 GHz clock light

70 km transmission line

9

1

EDFA

LN (AM)PC

BPF 1 nm


10 GHz

High power EDFA

Regeneratively mode-locked fiber laser

PLC MUX

640 Gbit/s

10 Gbit/s

LNPC PC

High power EDFA

Transmission Fiber

PC

DF-DDFHigh power EDFA

DI-NOLM

SMF

DFF

PC

DCF

EDFA BPF 1 nm

1

9BPF 3 nm

LD (cw)

Clock light

1.28 Tbit/s signal

clock = 1542 nm)

PC PBS

70 km

PC

LN (PM)

High power EDFA

SMF RDFBPF 15 nm

PBS

Optical Delay

Pre-chirping unit

= 1544 nm)

Setup for the demultiplexing of 1.28Tbit/s OTDM signal to 10 Gbit/s

(450 m)

NOLM Control IN

Walk-off free, dispersion-flattened NOLM

BPF 10 nm

( = 1556 nm)

PC

10 GHz

PLL mode-locked fiber laser

PCBPF 15 nm

High power EDFA

Transmitted 1.28 Tbit/s signal


Isolator

EDFA

BPF 1 nm

BPF 1 nm

9

1640 Gbit/s

PC

High power EDFA Autocorrelator

PBS ATT

ED

EDFA

PD

Sampling oscilloscope

High power EDFA

= 1533 nm)



M. Nakazawa et al., Electron. Lett., vol. 24, 2027 (2000).

Reduction of walk-off in NOLM for demultiplexing Reduction of walk-off in NOLM for demultiplexing

t

・Optimum NOLM with sufficient length can be obtained while avoiding

unwanted overlapping between signal and control pulses.

t

Control pulse

OTDM signal

t

Demultiplexed signal

NOLM with reduced walk-off

OTDM signal (640 Gbit/s)

Control pulse

t

t

t

t

t

t

・・・

Short DFFs connected to alternate walk-off sign

Demultiplexed signal (10 Gbit/s)

(50 m x 9 = 450 m)

Group delay characteristicsof walk-off free NOLM

M. Nakazawa et al., Electron. Lett., 34, 907 (1998).

Error-free 320 Gb/s simultaneous add-drop multiplexingusing NOLM

Error-free 320 Gb/s simultaneous add-drop multiplexingusing NOLM

H. C. Hansen Mulvad et al., OFC2007, OTuI5.

Add port Drop port

OutlineOutline

(1) Optical sources



(4) Demultiplexing


(6) Summary

t

f

t f

Transform-limited pulse=0.44 (Gaussian)=0.32 (Sech)

Spectral shape must be maintained.

Simultaneous elimination of all

linear distortions (including

time-varying perturbations)

Jitter, Higher-order dispersion, PMD, Adaptive equalization, …

Compensation of individual

waveform distortion in time domain

t t t

f

No rigid restrictions on input spectrum

Waveform disturbed.Transmitted spectrum may vary.

Conventional optical transmission

Distortion-free transmission with optical Fourier transformation (OFT)Transform spectrum into waveform in time domain

PMGVD

CLK OFT

Distortion-free transmission using time-domain optical Fourier transformation (OFT)


2

chirp 2

1exp),()( Ktitzutu

The transmitted pulse is linearly chirped in the form

When uchirp(t) is passed through a GVD medium, the output v(t) is expressed as

tdtt

D

itu

D

it 2

chirp )(2

exp)(2

)(v

When D =1/K , the output v(t) is written in the following form

(K is the chirp rate)

DtzUKtiD

i

tdtDtitzuKtiD

it

,2

1exp

2

exp),(2

1exp

2)(

2

2

v

The output waveform is proportional to the input spectrum U(z,), = t/D.

u(z, t) v(t)

U(z, )

D = k”L

GVD

V()PM

CLK

１２３

uchirp(t)

１

２

３

Time

Time

OFT



Advantage:

Any linear distortions (even when they vary with time) can be eliminated simultaneously with only one circuit.

M. Nakazawa et al, PTL, vol. 16, 1059 (2004).

ErrorDetector

Receiver (Demux, OFT, and demodulation)

PC

40 160 Gbit/s

160 Gbit/s transmitter975 km transmission line

40 GHzMLFL(1550 nm)

MUX

40 GHz

PPG

PLL

40 Gbit/s215-1 PRBS

PC

EDFAATT

DPSKModulator

Q Q

BalancedPD

DI

160 Gbit/s-1,000 km OTDM DPSK transmission using time-domain OFT

160 Gbit/s-1,000 km OTDM DPSK transmission using time-domain OFT

40 GHz PhaseModulator

SMF

PhaseShifter

EDFAPC

1:4MUX

160 40 Gbit/s

DEMUX

EDFA

10 GHz

CLK Phase

Shifter

OFTC

EDFA SMF50 km

IDF25 km

x13

1 1 0 1

1 1 0 1

OOK

DPSK

-34 -32 -30 -28 -26 -24 -22

Bit

Err

or

Ra

te

Received Optical Power [dBm]

10-11

10-4

10-5

10-6

10-7

10-8

10-9

10-10

Back-to-back975 km (without OFTC)975 km (with OFTC)

Data Optical intensity

Data Optical phase change

All-optical time-domain OFT by XPM in fiber with a parabolic pulse

All-optical time-domain OFT by XPM in fiber with a parabolic pulse

Chirp rate K

us(t) v(t)uchirp(t)

uc(t)

GVD

Apply linear chirp to a signal us(t) by cross-phase modulation with a control pulse (parabolic pulse) uc(t).

Phase modulation and chirp applied to signal us(t)

Nonlinear coefficient , Length lD = 1/K

Ktt

tPl

ttltPt

)(

2)()(,)(2)(

20 )/(1)( tPtP

tlP

t2

04)(

i.e., chirp rate 204

lP

K

P0

t

[1] T. Hirooka et al., CLEO-PR2005, CFJ3-4INV. [2] T. T. Ng et al., OFC2007, JWA58.

40 GHz bright and dark parabolic pulse generation using AWG

40 GHz bright and dark parabolic pulse generation using AWG

40 GHzmode-locked fiber laser

Parabola-shapingoptical filter(pre-shaping)

64 ch AWG pulse shaper

128 ch current source

VOA PS

Parabola fitting Parabola fitting

Bright parabolic pulse Dark parabolic pulse

Elimination of third-order dispersion by all-optical FT at 40 GHz

Elimination of third-order dispersion by all-optical FT at 40 GHz

TransmissionFiber (D) Optical

Delay Line

AWG PulseShaper

HNLF 1 km

= 17 W-1km-1

zero disp= 1543 nm

1550 nm, 1.7 ps

40 GHzMode-lockedFiber Laser

40 GHzMode-lockedFiber Laser

1537 nm, 1.7 ps

ClockRecovery

OpticalSamplingScope

OpticalSpectrumAnalyzer

GVD

5 nm

Pctrl = 28.5 dBm

PolarizationController

Distorted SignalPulse

Dark Parabolic Pulse

OFT Output

OFT Output (Sinusoidal PM)

3 ps 3 ps

10 ps 3 ps

1st ParabolicFiltering

Line by LineShaping

SummarySummary

We have reviewed advanced fiber technologies and their applications to high-speed optical communication, in which we showed that such fiber device technologies are indispensable to realize ultrahigh-speed communication.

Key fiber technologies cover various fields such as

(1) Optical source(2) Pulse compression and reshaping(3) Transmission line(4) Nonlinear effects(5) Demultiplexing

Advanced fiber device technology will largely accelerate ultrahigh-speed optical communication as the fibers have an excellent figure of merit due to low loss and long-length characteristics.

25.6-Tb/s C+L-band transmission of polarization-multiplexed RZ-DQPSK signals

25.6-Tb/s C+L-band transmission of polarization-multiplexed RZ-DQPSK signals

A. H. Gnauck et al. (Alcatel-Lucent), OFC2007, PDP19.

MDFs (Medial Dispersion Fibers) for 40 Gb/s transmission

Fiber type P-MDF N-MDF Total

Disp. [ps/nm/km] 13 -13 0

Slope [ps/nm2/km] 0.07 -0.07 0

Aeff [m2] 95 32 63

Loss [dB/km] 0.190 0.220 0.205

SLA+IDF

NZ-DSF

700

250

(ps/nm)

(km)500

350MDF

Dis

pers

ion

chan

ge

H.Sugahara et al., Post-deadline paper of OFC2002, FC6

The maximum accumulated dispersionof SLA(PSCF)+IDFIs too large to realizeLong-haul 40Gb/sWDM transmission

K.Mukasa et al., ECOC’00 Proceeding, 2-4-2 (2000)

New dispersion management for the high bit-rate WDM transmission

New dispersion management for the high bit-rate WDM transmission

InlineAmp.

InlineAmp.

G.656 fiber 80 km

PumpPump

G.656 fiber 80 km

PumpPump

G.656 fiber 80 km

PumpPump

P-EDF DCF, 6 km

PumpPump

GEQ

980 nm

Isolator

1480, 1505 nm

P-EDFA Raman Amp.

P-EDF

Pump

1480 nm

P-EDFA

Tx Rx

G.656 fiber 80 km

PumpPump

1440 nm,1470 nm,1500 nm,

580 mW

1440 nm,1470 nm,1500 nm,

340 mW

TransmissionLine

Unit SpanInline AmplifierDRA

Experimental setup: continuous-band repeater sectionExperimental setup: continuous-band repeater section

By courtesy of NTTMasuda et al., OFC2007

Recent trends in ultrahigh-speed OTDM transmissionRecent trends in ultrahigh-speed OTDM transmission

○ 160 Gb/s (OOK) ● 160 Gb/s (DPSK)□ 160 Gb/s-based WDM (OOK) ■ 160 Gb/s-based WDM (DPSK)△ > 160 Gb/s (OOK) ▲ > 160 Gb/s (DPSK, DQPSK)

SP: Single-polarization,AP: Alternating-polarization

200G,SP

400G,SP

640G,SP

19ch,SP

320G,AP

1.28T,AP

6ch,AP

4chCS-RZ,AP 4ch,AP

7ch,CS-RZAP,FEC

8ch,SP

8ch,APCS-RZ

6ch,APFEC

640GDPSK,AP

2.56T,DQPSK,AP

1.28T,DQPSK,AP

640G,DQPSK,AP

320G,SP

AP,FEC

SP,FEC

Field,8chCS-RZ,AP,FEC

AP

AP

Field,SP

AP

SPSP

SP,CS-RZ

SP

SP

Field,SP

Field,SP

Field,SPField,SP

Tra

nsm

issi

on

dis

tan

ce (

km)

OOK

DPSK

OOK(On-Off-Keying) → DPSK(Differential Phase Shift Keying)

UV interference Periodic index change

Induced refractive index change

Fabrication of FBGFabrication of FBG

Average index is not constant. Constant average index

No phase mask

Phase mask method

Apodization methodUV intensity is changed by using a silt with a sinusoidal shaped aperture.Average index is then adjusted by using a slit with an inverse aperture.

15 cm FBG realized by scanning mirror.

SBS threshold power for a soliton trainSBS threshold power for a soliton train

210 eff

B

A

Pg gB: Brillouin gain (=5x10-11 m/W), : Fiber loss, Aeff: Effective area, P0: Optical CW power

[1] R.G.Smith, Appl. Opt. 11, 2489 (1972).[2] M. Denariez and G. Bret, Phys. Rev. 171, 160 (1968).

“Average power” of a fundamental soliton train

eff2

2

31

avg 776.0 BAD

cnPN

D: Group velocity dispersion (GVD), : Wavelengthn2: Nonlinear refractive index, FWHM of input pulseB: Repetition rate, Aeff: Effective area

Longitudinal mode power

2

22

eff31

avg0 463.2 BD

cn

A

M

PP

N

f

M = /B

B

(2)

(3)

(Assume that PavgN=1 is divided equally into M modes)

(1)

SBS threshold for solitons is obtained from (1) and (3).

SBS threshold power (CW) [1]

Soliton power per mode vs. repetition rate.

CW power of solitons increases in proportion to B2. Broadening the source linewidth can reduce the

Brillouin gain (gB) and alleviate SBS [2]:

BpB

BB gg

B: Bandwidth of SBS gain spectrum

(=16 MHz)p: Source linewidth

Rec

eive

d P

ower

(dB

m, B

ER

=1

x 10

-9)

-40

-35

-30

-25

-20

-15

-10

20 40 60 80 100 120

Channel Number

1.28 Tbit /s - 70 km

PRBS 215-1

Channel Number

Bit error rate characteristicsBit error rate characteristics

-35 -30 -25 -20 -15 -10

Received Power (dBm)

10-3

10-4

10-5

10-6

10-7

10-8

10-9

10-10

10-11

10-12

Bit

Err

or R

ate

0 kmCh.1Ch.2Ch.3Ch.4Ch.5Ch.6

PRBS 215-1

BER characteristics Received power (@BER=1x10-9) vs channel number

1.28 Tbit/s – 70 km

Loss reduction of SLA and IDF and Pure Silica Core Fiber

Loss=0.185dB/kmLoss=0.185dB/kmAeff=100-110Aeff=100-110mm22

Disp.=+20ps/nm/kmDisp.=+20ps/nm/kmSlop=+0.06ps/nmSlop=+0.06ps/nm22/km/km

Loss=0.235dB/kmLoss=0.235dB/kmAeff=28-32Aeff=28-32mm22

Disp.=-45ps/nm/kmDisp.=-45ps/nm/kmSlop=-0.15ps/nmSlop=-0.15ps/nm22/km/km

【 SLA 】Large Aeff (Strong power)Low attenuation loss

【 IDF 】 Disp. Compensation Lower input power

Length ratio2:1-3:1

【 SMF+RDF total 】 Dispersion=0ps/nm/km Slope=0.00ps/nm2/kmAeff=80m2Loss=0.203dB/kmPMD=0.04ps/rkmCommercially

Available(OFS Denmark)

Silica level Loss=0.170dB/kmLoss=0.170dB/kmAeff=100-110Aeff=100-110mm22

Disp.=+20ps/nm/kmDisp.=+20ps/nm/kmSlop=+0.06ps/nmSlop=+0.06ps/nm22/km/km

PSCF technology

Only the attenuation loss can be reduced keeping other optical properties

K.Nagayama et al., Electron Lett. 38 (2002) pp1168-1169

The lower loss ever reported; 0.148dB/kmusing Pure silica core fiber technology

Optical properties improvements of SLA+IDFOptical properties improvements of SLA+IDF

Four-Wave Mixing (FWM)

1 23

21 2 3 d2(1)

d 2 ( )2 2c2 D(1)()2

(Nonlinear phase shift is ignored.)

P3(z) 16 2

2n2

Aeff

2

P12 (0)P2 (0)

sin2 ( )z / 2 ( )2

Four-wave mixing (FWM)Four-wave mixing (FWM)

Intrachannel FWM

Quasi-linear highly-dispersed pulse transmission

TX DC RX

Pulses are broadened and linearly chirped. (Nonlinear interaction between adjacent pulses is grately reduced.)

Frequency components belonging to different pulses can meet and produce mixingproduct at other bit positions.

amplitude jitter

ghost pulseI. Shake et al., Electron. Lett. 34, 1600 (1998).R. J. Essiambre et al., Electron. Lett. 35, 1576 (1999).P. V. Mamyshev and N. A. Mamysheva, Opt. Lett. 24, 1454 (1999).

amplitude jitter

Intrachannel FWMIntrachannel FWM

Characteristics of the fabricated PCF Characteristics of the fabricated PCF

Cross section of PCF

Air hole pitch 3.4 m

Air hole diameter d 1.2 m

Mode field diameter (850 nm) 5.3 m

Cutoff wavelength Endlessly single-mode

Transmission loss (850 nm) 5.2 dB/km (SIF: 3 dB/km)

Dispersion (850 nm) -62.8 ps/nm/km

-200

-150

-100

-50

0

50

700 800 900 1000 1100 1200

PCFSIF

Dis

pe

rsio

n (

ps/

nm

/km

)

Wavelength (nm)850

-62.8

-97.5

Dispersion characteristics

D

cTL o

D 2

2

2ln2

D

cTL o

D 2

2

2ln2

Dispersion distance: LD=37.4 km (10 Gbit/s) 、 2.3 km (40 Gbit/s)

(To: Pulse width, D: dispersion)

10 Gbit/s-2 km PCF transmission at 850 nm with a directly-modulated VCSEL

10 Gbit/s-2 km PCF transmission at 850 nm with a directly-modulated VCSEL

Conversion gain=500 V/W

Pulse patterngenerator VCSEL

852 nm

215-1 PRBS 　10 Gbit/s NRZ

Bias tee

PCF 2 km

Si-APDBit error ratetester

(a) Eye diagram after 2 km transmission (Received power: -13 dBm)

20 ps/div

3

4

5

6

7

89

10

-18 -17 -16 -15 -14 -13 -12

Lo

g (

BE

R)

Received power (dBm)

12

-

-

-

-

-

-

-

-11--

0 km2 km

3

4

5

6

7

89

10

-18 -17 -16 -15 -14 -13 -12

Lo

g (

BE

R)

Received power (dBm)

12

-

-

-

-

-

-

-

-11--

0 km2 km

(b) BER measurement

Dispersion and transmission loss of PCFDispersion and transmission loss of PCF

[1] K.Nakajima et al., OFC2004, PD 23, 2004.[2] L. Farr et al., ECOC2002, PD 1.3, 2002.[3] H. Kubota et al., CLEO ’01, PD CPD3-1, 2001.

Trade-off between dispersion and transmission loss

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Multi-mode

-50 -60

-70

2.7 dB/km

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Single-mode

D=0 ps/nm/km

-50 -60

-70

2.7 dB/km41dB/km

7.1 dB/km

3.4

0.35 -62.8 ps/nm/km

5.3 dB/km

5.2 dB/km

29 dB/km

2.8 dB/km

[2][2]

[1]

[3]

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Multi-mode

-50 -60

-70

2.7 dB/km

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Single-mode

D=0 ps/nm/km

-50 -60

-70

2.7 dB/km41dB/km

7.1 dB/km

3.4

0.35 -62.8 ps/nm/km

5.3 dB/km

5.2 dB/km

29 dB/km

2.8 dB/km

[2][2]

[1]

[3]-50 ps/nm/km

-60 ps/nm/km

-70 ps/nm/km

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Multi-mode

-50 -60

-70

2.7 dB/km

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Single-mode

D=0 ps/nm/km

-50 -60

-70

2.7 dB/km41dB/km

7.1 dB/km

3.4

0.35 -62.8 ps/nm/km

5.3 dB/km

5.2 dB/km

29 dB/km

2.8 dB/km

[2][2]

[1]

[3]

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Multi-mode

-50 -60

-70

2.7 dB/km

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

0.2

0.3

0.4

0.5

0.6

0.7

1 2 3 4 5 6

d/

m

Single-mode

D=0 ps/nm/km

-50 -60

-70

2.7 dB/km41dB/km

7.1 dB/km

3.4

0.35 -62.8 ps/nm/km

5.3 dB/km

5.2 dB/km

29 dB/km

2.8 dB/km

[2][2]

[1]

[3]-50 ps/nm/km

-60 ps/nm/km

-70 ps/nm/km

d/

For small　 Dispersion Decrease　 Loss Increase

For small loss, it is important to design a PCF with a large dispersion that is allowable in terms of the transmission distance and bit rate.

22

22.5

23

23.5

24

24.5

25

25.5

850 851 852 853 854G

ain

(dB

)Wavelength (nm)

Gain characteristicsSignal power: -25 dBmPump power: 500 mW

Bandwidth=3 nm980 nm pump

980 nm pump850 nm signal

1550 nm band

550 nm band

4F7/24S3/2

4I11/2

4I13/2

4I15/2

980 nm pump

980 nm pump850 nm signal

1550 nm band

550 nm band

4F7/24S3/2

4I11/2

4I13/2

4I15/2

Er fluoride fiber amplifier (EDFFA) in the 800 nm regionEr fluoride fiber amplifier (EDFFA) in the 800 nm region

=4.64 dB

Wavelength=975 nmMaximum power=500

WDM Coupler850 nm signal

EDF

Isolator

Fiber length: 5 mErconcentration: 2000 ppm

WDM Coupler

Insertion loss=4.64 dB



EDF

Isolator

Erconcentration: 2000 ppm

WDM Coupler=4.64 dB



EDF

Isolator

Erconcentration: 2000

WDM Coupler


Pump LD (InGaAs/GaAs)



EDFF

Isolator


WDM Coupler output=4.64 dB



EDF

Isolator

Fiber length: 5 mErconcentration: 2000 ppm

WDM Coupler




EDF

Isolator

Erconcentration: 2000 ppm

WDM Coupler=4.64 dB



EDF

Isolator


WDM Coupler


Pump LD (InGaAs/GaAs)

Wavelength=975 nmMaximum power=500 mW


EDFF

Isolator


WDM Coupler output

Gai

n (d

B)

Energy diagram of Er ion

Demultiplexing 1.28 Tbit/s signal to 10 Gbit/s Demultiplexing 1.28 Tbit/s signal to 10 Gbit/s

(Loop length : 450 m)

Ultrafast NOLM

BPF

10 GHz

Control pulse source (PLL mode locked fiber laser)

BPF EDFA


BPF (c = 1542 nm)

640 Gbit/sPC

PBS EDFA

( = 1533 nm)

Error detector

10 Gbit/s9

1

Clock extraction circuit in pre-chirping unit

LiNbO3 intensity modulator

1.28 Tbit/s signal

Transmission fiber

Clock light source (cw LD)

( = 1556 nm)

( = 1542 nm)10 GHZ clock light

Power transfer functions Power transfer functions SetupSetup

Bit error rate characteristicsBit error rate characteristics

(Control power ~200 mW)

Amplitude noise suppression of 160-G OOK/DPSKAmplitude noise suppression of 160-G OOK/DPSK

By courtesy of Fujitsu and HHI

320 Gbit/s DQPSK all-optical wavelength conversion using four wave mixing

320 Gbit/s DQPSK all-optical wavelength conversion using four wave mixing

M. Galili et al., OFC2007, OTuI3.

After filter & amp.

Comparison of conventional distortion compensation scheme with present OFT scheme

Comparison of conventional distortion compensation scheme with present OFT scheme

Waveform distortion

Conventional scheme OFT scheme

Must be compensated individually.

Sensitive to slight variations in perturbations especially for high-speed OTDM transmission.

Any linear distortions (even when they vary with time) can be eliminated simultaneously with only one circuit.

Jitter In-line synchronous modulation

(soliton control)

L. F. Mollenauer and C. Xu, CLEO 2002, CPDB1-1.

L. A. Jiang et al., Opt. Lett. vol. 28, 78 (2003).

PMD PMD compensator M. Romagnoli et al., Opt. Lett. vol. 24, 1197 (1999).

Higher-order dispersion

Dispersion-slope compensation fiber

Prechirp + Phase Modulation

M. Nakazawa et al., ECOC 2003 PDP, Th4.3.8.

Time-varying dispersion

Adaptive equalization (nonlinearly chirped FBGs, VIPAs, …)

T. Hirooka et al., ECOC 2004, Th1.5.3.

Parabolic pulseParabolic pulse

In a nonlinear optical fiber amplifier with normal GVD, a chirped pulse with a parabolic shape can be generated asymptotically.

Highly linear chirp No optical wave breaking

Approaches a parabolic shape at z∞ asymptotically without radiation, regardless of initial waveform [2]

Self-similar stable propagation“Similariton”[3]

[1] K. Tamura and M. Nakazawa, Opt. Lett., vol. 21, 70 (1996).[2] M. E. Fermann et al., Phys. Rev. Lett., vol. 84, 6010 (2000). [3] F. O. Ilday and F. W. Wise, CLEO2003, CTHPDA3.

Pump

High-quality pulse compression is possible by compensating for the chirp [1]

Characteristics of parabolic pulse

Optical fiber amplifier (Normal GVD)

Parabolic shape

Linear chirp•GVD-induced chirp•(Enhanced) SPM-induced chirp

TDC

BalancedReceiver

PLC MZDI

DEMUXOBPFPC

PBS

IL

Pre-Amp.

EDFA (C) orEDFA (Extended L)

ClockRecovery

CPL

CPL

RZ

RZ

IL

PC

PC

PLC+LNMod

PLC+LNMod

DCF

GEQ

P-EDFARamanAmp.

RamanAmp.

LC

LD1

LD31

LD33

LD101

LC

LD2

LD32

LD34

LD102

Tx

Rx

102 Ch DFB-LDs1535.82–1619.62 nm, 100-GHz spacing

111 Gb/sCSRZ-DQPSK

PolarizationMultiplexing

Ultra-high Speed111-Gb/s Channels

Ultra-wide-band 10.2-THzPost Amplifier

Spectral Efficiency= 2.0 b/s/Hz

20-Tb/s RZ-DQPSK transmission over 240 km20-Tb/s RZ-DQPSK transmission over 240 km

By courtesy of NTTMasuda et al., OFC2007 14

160 GHz parabolic pulse generation using ND-DDF (with linear approximation of GVD profile )

160 GHz parabolic pulse generation using ND-DDF (with linear approximation of GVD profile )

Fiber 1 ： D = -1.6 -0.1 ps/nm/km 　 (Linear decrease) = 3.3 W-1km-1, Length = 400 m

Fiber 2 ： D = -0.1 ps/nm/km 　 = 3.3 W-1km-1, Length = 1600 m

Input ： 160 GHz, 2.0 ps, 400 mW (Average power)

(a) GVD profile of ND (Normal Dispersion)-DDF

(b) Pulse propagation in ND-DDF

1 Length (km)

Time (ps)

Power (W)

Time (ps)

(c) Output waveform

Length (km)

No

rmal

Dis

per

sio

n (

ps/

nm

/km

)

Po

wer

(W

)

[1] T. Hirooka and M. Nakazawa, Opt. Lett. 29, 498 (2004).[2] T. Hirooka et al., CLEO-PR2005, CFJ3-4INV.

Polarization-multiplexed 1 Gsymbol/s, 128 QAM (14 Gbit/s) coherent optical transmission system

Polarization-multiplexed 1 Gsymbol/s, 128 QAM (14 Gbit/s) coherent optical transmission system

QAMModulator

PC

QAM(//)

QAM( )

Pilot

LO

⊥

(MUX)

(DEMUX)

Optical Filter (~ 5nm)

SMF 80 km

SMF 80 km

Att A/D

Digital SignalProcessor

IF SignalfIF=fsyn+fOFS=4 GHz

PD

PD

Synthesizer

(fsyn= 1.5 GHz)

DBM

1.4 GHz FBG

(fOFS =2.5 GHz)

Att

EDFA

EDFA: Erbium-doped Fiber AmplifierPC: Polarization ControllerOFS: Optical Frequency ShifterPBS: Polarization Beam SplitterDSF: Dispersion-shifted FiberFBG: Fiber Bragg GratingPD: Photo-detectorDBM: Double Balanced Mixer

QAMModulator

PBS

PBS

Q

I

C2H2 Frequency-Stabilized Fiber Laser

I

Q

Arbitrary Waveform Generator

Delay Line

( or )

OFS

Feedback Circuit

Arbitrary Waveform Generator

Optical Frequency

PilotQAM data signal

Inte

nsi

ty

2.5 GHz

- 3 dBm

Nyquist filter included

masataka nakazawa （中澤 正隆） research institute of electrical communication...

Documents

masataka nakazawa 　（中澤　正隆） research institute of electrical communication...