New Optical Functional Devices Functional Devices for all Optical Networks EurOpnet 00 Tutorial, January 30 Philippe Gallion Ecole Nationale Supérieure des Télécommunications URA CNRS 80 46, rue Barrault, 75634 Paris - Interest in All Optical Signal Processing - Physics Phenomena 3 - Wavelength Conversion 4 - Nonlinear Mirror Demultiplexing 5-3R Regeneration 6 - Conclusion Functional Devices, P.G., ENST Functional Devices, P.G., ENST Bandwidth requirement - Interest in All Optical Signal Processing Bandwidth requirement OTDM versus (D)WDM From Optoelectronic to «All Optical» Signal Processing Bandwidth: nm @.55 µ = 5Ghz @ 93THz - Today radio-frequency range < 00GHz - Overall optical fiber bandwidth: few 0THz btwn.3 &.5µ - Erbium amplifier bandwidth: few THz btwn.53 &.56µ - Today needs : 00 Gbit/s to Tbit/s per fiber? - Electronic bandwidth : few 0GHz Up to now: - Optical transmissions - Commutation, Routing & Processing in electronic domain - O/E & E/O conversions : slow, expensive (packaging), noisy, scrambling of the optical phase, lack of transparency... How to increase the bandwidth? Functional Devices, P.G., ENST 3 Functional Devices, P.G., ENST 4 OTDM versus (D)WDM The first reported WDM experiment: Rê Horaky (the sun at noon) transmits a WDM light beam to the praying Tapéret (800-900 B.C.) Le Louvre, Paris Wavelength Division Multiplexing (WDM) R E/O R E/O R i E/O ι ι E/O R Optical Mux Demux R Link E/O 3 E/O R i Optical Time Domain Multiplexing (OTDM) R E/O E/O R Optical R E/O Mux R Link Demux E/O R i E/O E/O R i Single Optical Source Functional Devices, P.G., ENST 5 Functional Devices, P.G., ENST 6
From Optoelectronic to «All Optical» Signal Processing Transmission OTDM versus (D)WDM Pulse generation & pulse shaping Dispersion compensation... Routing Wavelength Conversion Fix and programmable Optical Add & Drops (OAD) Restauration Optical Cross Connect (OXC) Optical signal processing Optical Demultiplexing Address label reading Clock (phase) Recovery Optical Regeneration : Re-amplification, Re-timing, Re-shaping (3R)... Supervision: wave watcher... Functional Devices, P.G., ENST 7 - Physical Phenomena Semiconductors Inter-band Dynamics Semiconductors Intra-band Dynamics Non-linearities in optical fiber Functional Devices, P.G., ENST 8 Semiconductors Inter-band Dynamics Gain and refractive index dependent on the carrier density Gain saturation A = Differential gain G = Optical gain G(N) = A(N N 0 ) N 0 = Carrier density for transparency Typical time constant from 0, to ns determined by the effective carrier lifetime τ = eff τ s 3 + ( GP) N Strong effect: power < mw, interaction length few 00µ Phase-amplitude coupling : α = few units Differential spontaneous emission rate 44 443 Differential stimilated emission rate τ s = Spontaneous carrier lifetime ( when I ) P = Photon density α = n n with n = n j n Functional Devices, P.G., ENST 9 Chirping in a When the optical Power increases : - The carrier density decreases - The refractive index increases (plasma effect) - The optical frequency decreases Functional Devices, P.G., ENST 0 Semiconductors Intra-band Dynamics Cross Gain Modulation (XGM) A strong stimulated rate disturbs quasi-equilibrium G(N, P) = A(N N 0 )( εp) ε gain compression factor P photons density ps time constant determined by intra-band thermalizations Gain compression (or compression) qlq % (heterostructure) 0% (quantum wells ) Gain suppression dip Gain saturation level Gain Gain Max 3dB P saturation P input XGM Two beams with intensity I and I in the same When I saturates the gain, I experiments also a reduced gain : XGM E experiments also the index change associated to the gain change (XPM) Pump E = I exp jϕ E = I exp jϕ with I << I Functional Devices, P.G., ENST Functional Devices, P.G., ENST
Nonlinear Index and Cross Phase modulation (XPM) Gain Linear Nonlinear Four Wave Mixing (FWM) in Semiconductor Optical Amplifier () Index Frequency Kramers- Kronig s Transformation (Hilbert s Transformation) E = I exp jϕ Lasing Frequency Frequency Carrier heating Large bandwidth (<0nm), asymmetrical High nonlinear index (α near ) Spectral hole burning Low bandwidth(<0nm) symmetrical Low nonlinear index (α near 0) XPM E = I exp jϕ Functional Devices, P.G., ENST 3 Physical origins: Interband for low frequencies : carrier density modulation, Intraband for high frequencies : nonlinear gain i.e. carrier heating, spectral-holeburning, photon absorption, Kerr effect Application to Wavelength conversion, 3R regeneration, Spectrum inversion Spurious effect in WDM systems Functional Devices, P.G., ENST 4 FWM New Frequencies Generation in WDM Systems Optical Kerr effect Nonlinearities in optical fiber Polarization: Index: P(E) = ε 0 χ () 3 E χ 4 () 4 E 3 + 4χ (3) E 4 4 3 3 +... linear =0 (symetry) Kerr effect n(ω, I)= { n(ω) { n I with I = E Z 0 dispersion Kerr effect Input Output Self Phase Modulation (SPM) & Cross Phase Modulation (XPM) Low effect but transverse confinement and longitudinal integration ϕ = π 0 n L S Ρ L = length km S = cross section 50µ 0 = wavelength =,5 µ P = optical poower Very fast effects but: Walk off problems Other concurrent nonlinear effects ϕ = π for PL = W.km Functional Devices, P.G., ENST 5 Functional Devices, P.G., ENST 6 Self Phase Modulation (SPM) & Cross Phase Modulation (XPM) Self Phase Modulation (SPM) SPM E = Cross Phase Modulation (XPM) XPM I exp jϕ Linear Propagation: k(ω) = ω 0 v ϕ + Nonlinear Propagation: Nonlinear Propagation: Soliton (ω ω 0 ) v G + (ω ω 0 ) Phase Enveloppe Enveloppe Propagation Propagation Distorsion! ω v G E = I exp jϕ E = I exp jϕ with I << I Functional Devices, P.G., ENST 7 k(ω) = ω 0 v ϕ + (ω ω 0 ) v G + (ω ω 0 )! ω v G +... + γi Phase Enveloppe Enveloppe Nonlinearities Propagation Propagation Distorsion Functional Devices, P.G., ENST 8
Wavelength Converter 3 - Wavelength Conversion Wavelength converter Cross Gain Modulation (XGM) in an Cross Phase Modulation (XPM) in an Gain Modulation in Semiconductor Laser (SCL) Wavelength conversion in bistable Laser Structure Four Wave Mixing (FWM) in a in Modulated optical input tuning control Wavelength converter gain control Wavelength routing Wavelength re-use WDM network reconfiguration Optical circuit & packet (ATM IP) switching out Modulated optical output Functional Devices, P.G., ENST 9 Functional Devices, P.G., ENST 0 Inputs N ATM Matrix for wavelength routing Wavelength encoder D CONTROL UNIT D Spatial switch Memory Star coupler K ' '' 0xT K N' (K-)xT K Wavelength converter Optical gate Delay line D Outputs N'' :K Filter Detector Europeen Project ACTS OPEN et KEOPS Functional Devices, P.G., ENST Expected Properties All optical device: Transparent to modulation format Bit rate independent: 55Mb/s à 0 Gb/s.40Gb/s No clock recovery requirement Flexible implementation Speed (0 Gbit/s and more) Wide conversion range Up conversion & down conversion allowed Polarization independent Input wavelength rejection No BER penalty (cascability) High extinction (on /off) ratio No jitter No chirp Amplification of the signal level Pulse reshaping All of them together? Functional Devices, P.G., ENST Optoelectronic conversion No bit rate transparency Bit rate bottleneck Noise Cost (packaging) All optical conversion Bit rate transparency High bit rate Possible pulse regeneration Integration: low cost Optoelectronic conversion v.s. all optical conversion Electronical processing Optical Processing Cross Gain Modulation (XGM) in an (TU Denmark) CW The carrier depletion induced by ( ) modulated signal amplification reduce the available gain for the CW signal ( ) amplification filter Functional Devices, P.G., ENST 3 Functional Devices, P.G., ENST 4
Performances for XGM in an Large conversion range: Few0nm, i.e. few 000GHz Gain bandwidth limited Modulation bandwidth: Few 0 Gbit/s Carrier lifetime limited Low chirp But: Inverted modulation (even cell number required) External output carrier generation High driving signal level: 0 to -0 dbm Low on/off ratio: 5 to 0 db Functional Devices, P.G., ENST 5 Cross Phase Modulation (XPM) in an Mach Zendher Interferometer (MZI) Conversion Input signal filter Converted signal CW signal Cross Phase Modulation (XPM) Low control power ( only a phase shift π is required) Accurate control power Polarization independent Possible up conversion and down conversion Low chirp 40 Gbit/s operation already demonstrated Optical Cross Connect (OXC) 6x0 Gbit/s already demonstrated Functional Devices, P.G., ENST 6 Gain Modulation in Semiconductor Laser (SCL) Oscillator Wavelength Conversion in Bistable Laser Structure Ι Ι Ι B Ι Ι ΙB Bragg region filter active region active region Bragg region AM and FM The carrier depletion induced by ( ) signal injection reduce the available gain for the CW lasing ( ) operation Gain and index changes result in simultaneous AM and FM (i.e. chirped) output Few0 Gbit/s, On/Off Ratio > 0dB, P control = few dbm Functional Devices, P.G., ENST 7 saturable absorber reff ( ω ) Saturable absorption Non injected (i.e. unpumped) region Vanish out under light injection Operation up to 40GBit/s demonstrated Possible re-timing operation by simultaneous optical or electrical clock modulation Functional Devices, P.G., ENST 8 Output Wavelength Tuning Lasing wavelength vs. injection current in the Bragg section Pout Optical Bisability Pout 554.0 553.0 Pin Pin t asing wavelength (nm) 55.0 55.0 0 0 40 60 80 00 Injection current in the Bragg section (ma) Mode hopping Progressive index saturation results in tuning efficiency (slope) reduction The bistability improve the on/off ratio) Reshaping possibility Functional Devices, P.G., ENST 9 Functional Devices, P.G., ENST 30
0 - BER influence Four Wave Mixing (FWM) in a pump 0-4 0-6 signal Beating at the frequency difference ω SIGNAL -ω PUMP 0-8 0-0 Bistable laser Reference - -0-8 -6-4 - Received power (dbm) Low degradation (or small improvement!) of the BER allows large scale cascability Functional Devices, P.G., ENST 3 Power (dbm) 0-0 -40 Conjugated Signal Pump Signal 545 555 565 Wavelength (nm) Applications : Wavelength conversion All optical clock recovery Spectrum inversion Spurious effect: Diaphotie in WDM systems Functional Devices, P.G., ENST 3 Conversion efficiency η = P CONJUGATED OUT PROBE SIGNAL P IN Functional Devices, P.G., ENST 33 Efficiency (db) 0 0 0-0 -0-30 Four Wave Mixing Efficiency (BT Labs) -40 0 0 0 3 Detuning (GHz) Interband 0 4 Efficiency (db) 0 0 0-0 -0-30 simulation experiment Interband + intraband -40 0 0 0 3 0 4 Detuning (GHz) Physical origins: Interband for low frequencies : carrier density modulation, Intraband for high frequencies : nonlinear gain i.e. carrier heating, spectralhole-burning, photon absorption, Kerr effect Takes benefit of built-in gain Functional Devices, P.G., ENST 34 FWM Performances (ENST) Transparency for the modulation format High bit rate Wide conversion range (65nm) by multiple conversion Polarization dependent 4 - Optical Demultiplexing by Nonlinear Mirror Optical Linear Mirror Loop Optical Nonlinear Mirror Loop Nonlinearity realization SLALOM 4x0GBit/s Demultiplexing Functional Devices, P.G., ENST 35 Functional Devices, P.G., ENST 36
Optical Linear Mirror Loop Linear Optical Loop Mirror (LOLM) Nonlinear Optical Loop Mirror (NLOLM) Incident Reflected E 0 E R COUPLEUR ( α) / Linear Reciprocal Loop BOUCLE LINEAIRE ET RECIPROQUE Incident Reflected E 0 E R COUPLEUR ( α) / expj Φ NL Non Linear Loop BOUCLE NON-LINEAIRE Transmitted E T jα / Transmitted E T jα / expj Φ NL Repartition coefficients for intensity : A = : ( α) and A : α Repartition coefficients for amplitude : a = : ( α) / and a : jα / Transmitted reflected fields for E 0 =: E T = a = + a = ( α) α = 0 for α = / E R = a = a = jα / ( α) / = j for α = / In linear regime output port is the input port (mirror) Functional Devices, P.G., ENST 37 Clockwise & unclockwise equal intensities : NL phase shift are identical Tuning for a nonlinear phase difference de phase equal to π Tradeoff between contrast (α /) & sensitivity (α /) High level signal () transmission (NL regime) Low level signal (0) reflection (NL effects are negligible) Functional Devices, P.G., ENST 38 Non linearity realization Fiber or semiconductor amplifier - Cross phase Modulation (XPM) in a fiber (NOLM) - Very fast(>00ghz) - High optical driving signal level (0 to 30dBm) - Long length(km) Control data (pump) SLALOM Semiconductor Laser Amplifier in a Loop Optical Mirror contrôle (pompe) - Cross phase Modulation (XPM) in SC amplifier (SLALOM) Semiconductor Laser Amplifier in a Loop Optical Mirror - Fast (<0GHz, inter-band & <00GHz intra-band) - Low optical driving signal level ((-0 à 0dBm) - Compact (<mm) données multiplexées Input data coupleur 50/50 t coupleur 00/0 Utilizations : - Intensity Filter - Correlator - Demuliplexer... Filtre Output données data démultiplexées Functional Devices, P.G., ENST 39 Functional Devices, P.G., ENST 40 4x0GBit/s Demultiplexing (HHI) 5-3R Regeneration Re-amplification, Re-timing, Re-shaping (3R) Re-amplification Pulse reshaping by nonlinear filtering Re- timing (Re-synchronization) Clock (phase) recovery 3R Regeneration MZI all optical regeneration All optical regeneration using FWM in Functional Devices, P.G., ENST 4 Functional Devices, P.G., ENST 4
Re-amplification Noise Signal P OUT Non linear transfert function P IN Noise P OUT Non linear transfert function P IN Amplified Spontaneous Emission (ASE) Suppression (France Telecom) Signal Noise Noise Re-amplification is limited by accumulated ASE and limited amplifier output power On/off ratio improvement by nonlinear response Different processing for weak (0) & strong () signals Act as digital electronics Functional Devices, P.G., ENST 43 Functional Devices, P.G., ENST 44 Noise Suppression & Intensity Modulation (Tokyo Institute of Technology) Intensity noise of a spectrumsliced incoherent source Gain saturated with current modulation Beat noise reduction Noise error floor observed with LiNbO 3 linear modulation is removed Pulse reshaping by nonlinear filtering P OUT reflected transmitted t Outputs t Input Non linear transfert function P IN Functional Devices, P.G., ENST 45 Functional Devices, P.G., ENST 46 Re-timing (Re-synchronization) Clock (phase) recovery Input Clock Recovery Optical Gate Output 0 0 Mode locked laser Clock signal Gate Opening Input Output after the Gate Output after Power Control de la porte Functional Devices, P.G., ENST 47 0 0 R.Z. Data Sequence Self-Pulsating laser Clock signal - Large wavelength deviation (3 nm) - Low time jitter ( ps) - High bit-rate (3.8 GHz). Functional Devices, P.G., ENST 48
Self Pulsating Laser Ouput puissance power optique I I Laser Self pulsating DFB Autopulsant laser T AP = /f AP Self pulsation origins: Instabilities in longitudinal carrier or field distributions (Spatial-Hole Burning) Dispersive self Q-switching associated to the negative slope of the Bragg grating Functional Devices, P.G., ENST 49 Synchronization time (HHI) a - data signal b - clock signal c - recovered clock signal 0 Gbit/s ns (0 one bits) locking time Synchronization resist to > 00 zero bits Compatible with IP packet switching Functional Devices, P.G., ENST 50 3R Regeneration Input Jitter & Amplified Spontaneous Emission (ASE) Suppression (France Telecom) Clock Recovery Amplification Power Control Optical Gate Reamplification Retiming Non-linear Filter Reshaping Output Functional Devices, P.G., ENST 5 Functional Devices, P.G., ENST 5 MZI all optical regeneration - MZI all optical regeneration - (Alcatel Corporate Research Center) Input signal Clock signal filter Regenerated signal Input signal XPM is the key phenomena Up to 40Gbit/s operation demonstrated Functional Devices, P.G., ENST 53 cascaded MZI to improve nonlinear response 0 and 40 Gbit/s operation. db penalty Polarization insensitivity and0 db power dynamic range Functional Devices, P.G., ENST 54
All optical regeneration using FWM in (ENST) Conclusion - Ouput extinction ratio (db) 4 Theoretical limit 0 8 6 0 db improvement 4 4 6 8 0 Input extinction ratio (db) P signal /P clock = 0 db P signal /P clock = 0 db P FWM P PUMP.P PROBE PUMP = SIGNAL PROBE =CLOCK The squaring improved the On/off ratio The pulse overlap is the correlation process between clock and signal Nonlinear Fiber Devices Semiconductor Optical Devices (Intraband dynamics) Semiconductor Optical Devices (Interband dynamics) Fast electronical Devices High Integration Electronical Devices Integration Possibility 0 7 0 8 0 9 0 0 0 0 (Hz) Functional Devices, P.G., ENST 55 Functional Devices, P.G., ENST 56 Conclusion - Nonlinearity allows light with light interaction They are the key phenomena for all optical devices Nonlinearity is spurious in analog devices and systems Digital electronics takes benefit if it at each step They are the key phenomena for optical regeneration The all optical processing do not exist! It a user (system) point of view Electrons play a key role in light- matter interaction The speedy user have no time left to look at it Wide range of functional devices is today available Are this grapes too unripe? (Jean de La Fontaine) Functional Devices, P.G., ENST 57