[PPT] - All-Optical Regeneration of Phase-Encoded Signals in Transmission PowerPoint Presentation

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M. Matsumoto

Graduate School of Engineering Osaka University

2010 IEEE Photonics Society Summer Topical Meeting

n Nonlinear Fiber Optics

July 19-21, 2010

All-Optical Regeneration of Phase-Encoded Signals in Transmission Systems

SLIDE 2

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Outline

◆ Introduction ◆ Summary ◆ (D)BPSK signal regeneration ◆ (D)QPSK signal regeneration ◆ Discussion

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Introduction

Demand for cost-effective high-capacity transmission is increasing.

◆ Higher symbol rates are being

used.

◆ Advanced modulation formats having high spectral efficiency

are being introduced. and/or

, ...

time

Re Im

Transmission distance is limited by noise accumulation together with nonlinear and linear signal impairments. Long-distance systems may need signal regenerators.

TX RX TX RX TX RX

It is desired that some or all of the electrical regenerators are replaced by all-optical regenerators.

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Introduction

Issues All-optical regenerators  higher-speed operation  lower-power consumption  less format-dependent operation are expected. ◆ Regeneration of signals in advanced modulation formats (QPSK, 8PSK, QAM,....) is yet to be explored. ◆ Regenerators accept only signals meeting predetermined conditions (pulse width, chirp,...). ◆ DEMUX/MUX are needed in general for regeneration of WDM signals.

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Regeneration of PSK signals

 Regeneration of PSK signals needs regeneration of amplitude

and phase or two quadrature components (two dimensions).

 Regeneration of OOK signals is simple.

Pout Pin

1. Phase-preserving amplitude regeneration
2. Phase and amplitude regeneration using PSK to OOK

demodulation and amplitude regeneration

3. Phase and amplitude regeneration using saturated phase-

sensitive amplifier

4. Noise averaging between adjacent symbols

Schemes of (D)BPSK signal regeneration

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1. Phase-Preserving Amplitude Regeneration

phase-preserving amplitude regeneration

transmission over nonlinear fiber (SPM)

Phase noise after the transmission over nonlinear fiber is reduced.

 Saturation of four-wave mixing in fiber

M.Matsumoto, PTL17,1055(2005)

 Asymmetric NOLM

A.G.Striegler et al.,PTL17,639(2005), K.Cvecek et al.,PTL19,146(2007)

 Semiconductor saturable absorber

Q.T.Le et al.,PTL22,887(2010)

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2. Phase and Amplitude Regeneration Using

Amplitude-Only Regenerator

Phase modulation Amplitude modulation Amplitude regenerator Amplitude information is transformed back to phase information.

Demodulation using delay interferometer Coherent demodulation

(Amplitude noise is removed.)

DPSK OOK BPSK OOK

Local Oscillator

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2-1. DPSK Regenerator Using a Straight-Line Phase Modulator

2R amplitude regenerator All-optical phase modulator input

utput

1-bit DI CR / Optical pulse source

λs λs+ Δλ

Clock recovery / Optical pulse source 1-bit delay interferometer x N

λ's λ's

HNLF HNLF Phase modulator Amplitude regenerator

Strength of the 2R amplitude regenerator > 6.5dB

M. Matsumoto, PTL17, 213 (2007).

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Experimental Setup

10Gb/s DPSK signal regeneration
Two-stage Mamyshev regenerator in bidirectional configuration is used.
Mode-locked semiconductor laser (MLLD) is used as a clock source.
XPM-based all-optical phase modulation is used.

HNLF1: D=-0.35ps/nm/km γ ~12/W/km L=1.8km

M. Matsumoto and H. Sakaguchi, OE16, 11169 (2008)
M. Matsumoto and Y. Morioka, OE17, 6913 (2009)

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Experimental Result

Waveforms in the regenerator input signal (A) OOK signal after DI (B) OOK signal after 2R (C)

utput signal (D)

HNLF: D=2.2ps/nm/km γ ~12/W/km L=2.4km Δλ=4.5nm, walkoff time =24ps

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Transmission Experiment

DPSK TX DPSK signal regenerator DPSK RX ATT1 DDM fiber (DSF) 40km SMF (50km)+DCF Ps ATT2

Transmission experiment at 10Gb/s

Signal before the regenerator is degraded either by nonlinearity (when Ps is large) or by ASE (when ATT1 is large).

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Experimental Result

Signal before regeneration is degraded by nonlinearity.

1e-10 1e-9 1e-8 1e-7 1e-6 1e-5 0.0001 0.001 0.01

40
35
30
25
20
15

BER received power Prec (dBm)

after 2nd span

1e-10 1e-9 1e-8 1e-7 1e-6 1e-5 0.0001 0.001 0.01

40
35
30
25

BER received power Prec (dBm)

after 1st span

regenerator not inserted regenerator inserted

- Ps=8dBm
- 9.5dBm
- 11dBm

regenerator not inserted regenerator inserted

- ATT2=8dB
- 14dB
- 18dB

Ps=9.5dBm

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2-2. DPSK Regenerator Using a Mach-Zehnder Interferometer Modulator

Complementary OOK signals drive all-optical modulators in MZI.
All-optical modulators in MZI can be either phase or amplitude

modulators.

utput

CR / Optical pulse source All-optical modulator All-optical modulator

1-bit DI

DPSK OOK OOK

Ain exp(in) Aout exp(out)

I. Kang et al.,Th4.3.3,ECOC2005 (2005)
P. Vorreau et al.,PTL18, 1970 (2006)
Ch. Kouloumentas et al.,OMT5, OFC2010 (2010)

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Requirements for the Modulators

Additional 2R regenerators are needed either before or after the DI for suppression of both phase and amplitude noise.

utput

CR / Optical pulse source Phase modulator Phase modulator 1-bit DI

Phase-preserving 2R regenerator 2R regenerator 2R regenerator

(Strength of the amplitude regenerator > 0.46 dB) Amplitude modulators instead of phase modulators can be used. Saturation behavior of the modulators may make the 2R amplitude regenerators unnecessary.

R. Elschner et al., OL32, 112 (2007)
R. Elschner et al.,ThP3, 2007LEOS Annual Meeting (2007)
J. Wang et al., OE17, 22639 (2009).

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Logic Alteration and its Recovery

D

cn dn=cn ⊕ dn-1

DPSK regenerator using DI for DPSK --> OOK demodulation bn=an ⊕ an-1 D

=

bk

・・・ 0 1 1 0 1 0 1 1 1 0 1 0 π π 0 π 0 π π π 0 π （phase ）（phase

time

ak ・・・ 0 0 1 0 0 1 1 0 1 0 0 1

0 0 π 0 0 π π 0 π 0 0 π ）

time

Demodulation by DI alters data logic. (Phase difference absolute phase) The logic alteration can be recovered by pre/post-coding.

I. Kang et al.,Th4.3.3,ECOC2005 (2005)
P. Vorreau et al.,PTL18, 1970 (2006)

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2-3. BPSK Regenerator Using Coherent Demodulation

Demodulation from DPSK to OOK by DI may be replaced by coherent demodulation.

2R phase modulator input

utput

CR / Optical pulse source Local

scillator

Coherent demodulation can be similarly used in the MZI-based regenerator.

Required strength of 2R may be halved. Logic of the signal is preserved. ◆ Phase-locked local oscillator is needed.

1-bit DI

2R phase modulator input

utput

CR / Optical pulse source

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3. BPSK Regenerator Using Phase-Sensitive Amplifier

Degenerate nonlinear interferometer Two-pump degenerate FWM

3dB coupler

Es Ep Es,out

signal pump1 pump2

ω

Es,out = µEs,in + E s,in

µ

2 2 = 1

( )

Phase-sensitive gain

in small-signal condition

Extraction of one quadrature component

K. Croussore et al.,OL29, 2357 (2004)
K. Croussore et al.,OE14, 2085 (2006)
A. Bogris and D. Syvridis, PTL18, 2144 (2006)
K. Croussore and G. Li, JSTQE14, 648 (2008)
C. J. McKinstrie and S. Radic, OE12, 4973 (2004)
M. E. Marhic and C. -H. Hsia, Quantum Opt.3, 341 (1991)

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Phase and Amplitude Regeneration

x G x 1/G Phase-sensitive gain Phase-sensitive gain and its saturation

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Recent Experiment

OFC 2010 PDPC3

ωp1ωs

ω

2ωs −ωp1

ωp1ωs

ω

pump seed generation in HNLF1 injection locking of LD

ωp1 ωs ωp2

PSA in HNLF2

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Regeneration of (D)QPSK signals

1. Phase-preserving amplitude regeneration
2. Phase and amplitude regeneration using PSK to OOK

demodulation and amplitude regeneration

3. Phase and amplitude regeneration using saturated phase-

sensitive amplifier

Schemes of (D)QPSK signal regeneration

regenerator

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(D)QPSK Regenerator Using Amplitude Regenerators

1. Regenerator using straight-line phase modulators
2. Regenerator using MZI

2R regenerator input

utput

phase modulator 0 / π 0 / π/2 CR / Optical pulse source θDI=π/4 θDI=-π/4 2R regenerator phase modulator input

utput

CR/Pulse source All-optical modulator All-optical modulator All-optical modulator All-optical modulator 2R 2R 2R 2R θDI = π/4 θDI = -π/4 π/2

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(D)QPSK Regenerator Using Amplitude Regenerators

Required strength of 2R amplitude regenerators is larger than

that of DPSK regenerators.

Delay interferometers (DIs) are not operated at their maxima in output power vs phase difference response. Suppression of input phase noise is weaker.

Logic alteration can be recovered by suitable pre/post coding at

terminals.

Coherent demodulation instead of DI demodulation can be
used. (X. Yi et al., JLT28,587 (2010))

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Numerical Simulation

2R regenerator input

utput

phase modulator 0 / π 0 / π/2 CR / Optical pulse source θDI=π/4 θDI=-π/4 2R regenerator phase modulator

All-optical modulators using XPM in HNLF Cascaded Mamyshev-type 2R amplitude regenerators 80Gsymbol/s (160Gbit/s) 2.5ps RZ-DQPSK

M. Matsumoto, OE18, 10 (2010)

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Numerical Simulation

2
1

1 2

2
1

1 2 Imaginary part [mW

1/2]

Real part [mW

1/2]

(a)

1.5

1.5

1.5

1.5 Imaginary part [mW

1/2]

Real part [mW

1/2]

(b)

2
1

1 2

2
1

1 2 Imaginary part [mW

1/2]

Real part [mW

1/2]

(c)

1.5

1.5

1.5

1.5 Imaginary part [mW

1/2]

Real part [mW

1/2]

(d)

input OSNR 26 dB/0.1nm 24 dB/0.1nm

2 4 6 8 10 20 22 24 26 28 30 32 standard deviation of phase fluctuation (deg) OSNR (dB/0.1nm)

,input ,output

simulation using 1024 symbols

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QPSK Regenerator Using Phase-Sensitive Amplifiers

Saturated phase-sensitive gain in two quadratures Coherent addition

Z. Zheng et al., OC281, 2755

(2008)

Phase-sensitive gain for extraction of individual quadrature components + phase-preserving multi-level amplitude regeneration QAM regeneration

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Issues

1. Regenerators accept only predetermined-shaped pulses.

For wide acceptance of all-optical regenerators in practical systems, several issues must be addressed:

Optical dispersion compensation will be needed before the

regenerator.

In some types of regenerators, pulse overlap before

regenerators leads to inter-symbol interference.

Such ISI may be mitigated by signal processing at the

receiver such as Maximum Likelihood Sequence Estimation, while the regenerator performance is mostly retained. Cooperative use of

all-optical regeneration and other
ptical compensation methods
electrical signal processing at terminals.

will be a future research topic.

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Summary

Regeneration of phase-encoded signals has been discussed.

1. (D)BPSK-signal regeneration
Phase-preserving amplitude regenerator
Phase and amplitude regenerator using (D)BPSK to OOK

demodulation

Phase and amplitude regenerator using phase-sensitive

amplifier

2. (D)QPSK-signal regeneration
Simulation of 160Gb/s DQPSK signal regeneration using

fiber-based amplitude regenerator.

3. Issues in using all-optical regenerators in real systems

Graduate School of Engineering Osaka University

2010 IEEE Photonics Society Summer Topical Meeting

July 19-21, 2010

All-Optical Regeneration of Phase-Encoded Signals in Transmission Systems

Outline

◆ Introduction ◆ Summary ◆ (D)BPSK signal regeneration ◆ (D)QPSK signal regeneration ◆ Discussion

Introduction

Demand for cost-effective high-capacity transmission is increasing.

used.

are being introduced. and/or

, ...

Transmission distance is limited by noise accumulation together with nonlinear and linear signal impairments. Long-distance systems may need signal regenerators.

TX RX TX RX TX RX

It is desired that some or all of the electrical regenerators are replaced by all-optical regenerators.

Introduction

Regeneration of PSK signals

 Regeneration of PSK signals needs regeneration of amplitude

and phase or two quadrature components (two dimensions).

 Regeneration of OOK signals is simple.

Pout Pin

demodulation and amplitude regeneration

sensitive amplifier

Schemes of (D)BPSK signal regeneration

phase-preserving amplitude regeneration

transmission over nonlinear fiber (SPM)

Phase noise after the transmission over nonlinear fiber is reduced.

M.Matsumoto, PTL17,1055(2005)

A.G.Striegler et al.,PTL17,639(2005), K.Cvecek et al.,PTL19,146(2007)

Q.T.Le et al.,PTL22,887(2010)

Amplitude-Only Regenerator

Phase modulation Amplitude modulation Amplitude regenerator Amplitude information is transformed back to phase information.

Demodulation using delay interferometer Coherent demodulation

(Amplitude noise is removed.)

DPSK OOK BPSK OOK

2-1. DPSK Regenerator Using a Straight-Line Phase Modulator

2R amplitude regenerator All-optical phase modulator input

1-bit DI CR / Optical pulse source

Strength of the 2R amplitude regenerator > 6.5dB

Experimental Setup

Experimental Result

Waveforms in the regenerator input signal (A) OOK signal after DI (B) OOK signal after 2R (C)

Transmission Experiment

DPSK TX DPSK signal regenerator DPSK RX ATT1 DDM fiber (DSF) 40km SMF (50km)+DCF Ps ATT2

Transmission experiment at 10Gb/s

Signal before the regenerator is degraded either by nonlinearity (when Ps is large) or by ASE (when ATT1 is large).

Experimental Result

Signal before regeneration is degraded by nonlinearity.

after 2nd span

after 1st span

2-2. DPSK Regenerator Using a Mach-Zehnder Interferometer Modulator

modulators.

DPSK OOK OOK

Requirements for the Modulators

Additional 2R regenerators are needed either before or after the DI for suppression of both phase and amplitude noise.

Phase-preserving 2R regenerator 2R regenerator 2R regenerator

(Strength of the amplitude regenerator > 0.46 dB) Amplitude modulators instead of phase modulators can be used. Saturation behavior of the modulators may make the 2R amplitude regenerators unnecessary.

Logic Alteration and its Recovery

cn dn=cn ⊕ dn-1

DPSK regenerator using DI for DPSK --> OOK demodulation bn=an ⊕ an-1 D

=

bk

・・・ 0 1 1 0 1 0 1 1 1 0 1 0 π π 0 π 0 π π π 0 π （phase ） （phase

ak ・・・ 0 0 1 0 0 1 1 0 1 0 0 1

0 0 π 0 0 π π 0 π 0 0 π ）

Demodulation by DI alters data logic. (Phase difference absolute phase) The logic alteration can be recovered by pre/post-coding.

2-3. BPSK Regenerator Using Coherent Demodulation

Demodulation from DPSK to OOK by DI may be replaced by coherent demodulation.

Coherent demodulation can be similarly used in the MZI-based regenerator.

Required strength of 2R may be halved. Logic of the signal is preserved. ◆ Phase-locked local oscillator is needed.

Degenerate nonlinear interferometer Two-pump degenerate FWM

Es Ep Es,out

ω

Es,out = µEs,in + E s,in

( )

Phase-sensitive gain

in small-signal condition

Extraction of one quadrature component

Phase and Amplitude Regeneration

x G x 1/G Phase-sensitive gain Phase-sensitive gain and its saturation

Recent Experiment

・・・ 0 1 1 0 1 0 1 1 1 0 1 0 π π 0 π 0 π π π 0 π （phase ）（phase