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

All-Optical Regeneration of Phase-Encoded Signals in Transmission Systems M. Matsumoto Graduate School of Engineering Osaka University 2010 IEEE Photonics Society Summer Topical Meeting on Nonlinear Fiber Optics July 19-21, 2010 1 WC3.2 Matsumoto / 27

Outline ◆ Introduction ◆ (D)BPSK signal regeneration ◆ (D)QPSK signal regeneration ◆ Discussion ◆ Summary 2 WC3.2 Matsumoto / 27

Introduction Demand for cost-effective high-capacity transmission is increasing. ◆ Advanced modulation formats having high spectral efficiency are being introduced. Im ... , and/or Re ◆ Higher symbol rates are being used. time Transmission distance is limited by noise accumulation together with nonlinear and linear signal impairments. Long-distance systems may need signal regenerators. RX TX RX RX TX TX It is desired that some or all of the electrical regenerators are replaced by all-optical regenerators. 3 WC3.2 Matsumoto / 27

Introduction All-optical regenerators  higher-speed operation  lower-power consumption  less format-dependent operation are expected. Issues ◆ 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. 4 WC3.2 Matsumoto / 27

Regeneration of PSK signals  Regeneration of OOK signals is simple. P out P in  Regeneration of PSK signals needs regeneration of amplitude and phase or two quadrature components (two dimensions). Schemes of (D)BPSK signal regeneration 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 5 WC3.2 Matsumoto / 27

1. Phase-Preserving Amplitude Regeneration transmission over phase-preserving nonlinear fiber (SPM) amplitude regeneration 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) 6 WC3.2 Matsumoto / 27

2. Phase and Amplitude Regeneration Using Amplitude-Only Regenerator Phase modulation Demodulation using delay interferometer DPSK OOK Coherent demodulation Amplitude modulation BPSK OOK Local Amplitude Oscillator regenerator (Amplitude noise is removed.) Amplitude information is transformed back to phase information. 7 WC3.2 Matsumoto / 27

2-1. DPSK Regenerator Using a Straight-Line Phase Modulator CR / Optical All-optical pulse source phase modulator output input 2R amplitude regenerator 1-bit DI HNLF λ ' s Clock recovery / Optical pulse source λ ' s Phase modulator x N λ s HNLF 1-bit delay λ s + Δλ interferometer Amplitude regenerator M. Matsumoto, PTL17, 213 (2007). Strength of the 2R amplitude regenerator > 6.5dB 8 WC3.2 Matsumoto / 27

Experimental Setup HNLF1: D=-0.35ps/nm/km γ ~12/W/km L=1.8km • 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. M. Matsumoto and H. Sakaguchi, OE16, 11169 (2008) 9 WC3.2 Matsumoto / 27 M. Matsumoto and Y. Morioka, OE17, 6913 (2009)

Experimental Result Waveforms in the regenerator input signal (A) OOK signal after DI (B) OOK signal after 2R (C) output signal (D) HNLF: D=2.2ps/nm/km γ ~12/W/km L=2.4km Δλ =4.5nm, walkoff time =24ps 10 WC3.2 Matsumoto / 27

Transmission Experiment Transmission experiment at 10Gb/s SMF (50km)+DCF DDM fiber (DSF) 40km DPSK DPSK signal DPSK ATT1 ATT2 TX RX regenerator P s Signal before the regenerator is degraded either by nonlinearity (when P s is large) or by ASE (when ATT1 is large). 11 WC3.2 Matsumoto / 27

Experimental Result Signal before regeneration is degraded by nonlinearity. -- ATT2=8dB P s =9.5dBm -- P s =8dBm -- 14dB -- 9.5dBm -- 18dB -- 11dBm regenerator inserted regenerator inserted regenerator not inserted regenerator not inserted 0.01 0.01 0.001 0.001 0.0001 0.0001 1e-5 1e-5 BER BER 1e-6 1e-6 1e-7 1e-7 1e-8 1e-8 1e-9 1e-9 1e-10 1e-10 -40 -35 -30 -25 -40 -35 -30 -25 -20 -15 received power P rec (dBm) received power P rec (dBm) after 2nd span after 1st span 12 WC3.2 Matsumoto / 27

2-2. DPSK Regenerator Using a Mach-Zehnder Interferometer Modulator OOK DPSK output All-optical modulator CR / Optical pulse source All-optical A in exp( � in ) A out exp( � out ) 1-bit DI modulator OOK • Complementary OOK signals drive all-optical modulators in MZI. I. Kang et al.,Th4.3.3,ECOC2005 (2005) P. Vorreau et al.,PTL18, 1970 (2006) Ch. Kouloumentas et al.,OMT5, OFC2010 (2010) • All-optical modulators in MZI can be either phase or amplitude modulators. 13 WC3.2 Matsumoto / 27

Requirements for the Modulators Additional 2R regenerators are needed either before or after the DI for suppression of both phase and amplitude noise. R. Elschner et al., OL32, 112 (2007) R. Elschner et al.,ThP3, 2007LEOS Annual Meeting (2007) 2R regenerator Phase output modulator Phase-preserving CR / Optical 2R regenerator pulse source Phase 1-bit DI modulator 2R regenerator (Strength of the amplitude regenerator > 0.46 dB) Saturation behavior of the modulators may make the 2R amplitude regenerators unnecessary. Amplitude modulators instead of phase modulators can be used. J. Wang et al., OE17, 22639 (2009). 14 WC3.2 Matsumoto / 27

Logic Alteration and its Recovery Demodulation by DI alters data logic. (Phase difference absolute phase) D b n =a n ⊕ a n-1 = DPSK regenerator using DI for DPSK --> OOK demodulation 0 0 π 0 0 π π 0 π 0 0 π （ phase （ phase 0 π π 0 π 0 π π π 0 π ） ） a k ・・・ 0 0 1 0 0 1 1 0 1 0 0 1 b k ・・・ 0 1 1 0 1 0 1 1 1 0 1 time time The logic alteration can be recovered by pre/post-coding. D d n =c n ⊕ d n-1 c n I. Kang et al.,Th4.3.3,ECOC2005 (2005) P. Vorreau et al.,PTL18, 1970 (2006) 15 WC3.2 Matsumoto / 27

2-3. BPSK Regenerator Using Coherent Demodulation Demodulation from DPSK to OOK by DI may be replaced by coherent demodulation. phase CR / Optical modulator pulse source output input 2R 1-bit DI phase CR / Optical modulator pulse source input output 2R Local Coherent demodulation can be similarly oscillator 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. 16 WC3.2 Matsumoto / 27

3. BPSK Regenerator Using Phase-Sensitive Amplifier Degenerate nonlinear interferometer 3dB coupler K. Croussore et al.,OL29, 2357 (2004) E p E s K. Croussore et al.,OE14, 2085 (2006) E s,out Two-pump degenerate FWM pump1 pump2 A. Bogris and D. Syvridis, PTL18, 2144 (2006) signal K. Croussore and G. Li, JSTQE14, 648 (2008) ω 2 � � 2 = 1 ( ) � E s,out = µ E s,in + � E s,in µ in small-signal condition C. J. McKinstrie and S. Radic, OE12, 4973 (2004) M. E. Marhic and C. -H. Hsia, Quantum Opt.3, 341 (1991) Phase-sensitive gain Extraction of one quadrature component 17 WC3.2 Matsumoto / 27

Phase and Amplitude Regeneration Phase-sensitive x 1/G gain x G Phase-sensitive gain and its saturation 18 WC3.2 Matsumoto / 27

Recent Experiment OFC 2010 PDPC3 ω p1 ω p2 ω ω PSA ω p1 ω s ω s ω p1 ω s in HNLF2 pump seed injection generation locking of 2 ω s −ω p1 in HNLF1 LD 19 WC3.2 Matsumoto / 27

Regeneration of (D)QPSK signals regenerator Schemes of (D)QPSK signal regeneration 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 20 WC3.2 Matsumoto / 27

(D)QPSK Regenerator Using Amplitude Regenerators 1. Regenerator using straight-line phase modulators 0 / π /2 0 / π phase CR / Optical phase modulator pulse source modulator θ DI = π /4 output 2R input regenerator 2R regenerator θ DI =- π /4 2. Regenerator using MZI θ DI = π /4 2R All-optical modulator All-optical 2R input modulator CR/Pulse source 2R output All-optical modulator π /2 θ DI = - π /4 All-optical 2R modulator 21 WC3.2 Matsumoto / 27

(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)) 22 WC3.2 Matsumoto / 27