PhD Seminar David Dahan 2005

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Raman and Parametric mediated amplification and all optical processing for high speed fiber optics communication systems

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PhD Seminar David Dahan 2005

  1. 1. 1 Raman and Parametric mediated amplification and all optical processing for high speed fiber optics communication systems David Dahan Electrical Engineering Department Technion 27/06/2005
  2. 2. 2 Acknowledgements  My supervisor : Prof. Gadi Eisenstein  Former and current students  Dr. Kobi Lasri  Dr. Alberto Bilenca  Evgeny Shumakher  Robert Alizon  Din Hadass  Ido Ben-Aroya  Laboratory staff  Dr. Mark Sogolov  Dr. Boris Levit  Dr. Alex Bekker  Vladimir Smulakovsky  Scholarships and prices  Technion: Martin Prosserman fellowship  Ministry of Science: Levy Eskhol scholarship  IEEE/LEOS: Graduate student fellowship award (2005)
  3. 3. 3 Research Topics  Stimulated Raman Scattering (SRS) in fiber  ASE Noise properties of saturated Raman Fiber amplifier in CW regime  Inter band Raman mediated wavelength converter and reshaper  Parametric Processes in fibers for optical pulse source generation  A Self Starting Ultra Low Jitter Pulse Source Using Coupled Optoelectronic Oscillators with an Intra Cavity Fiber Parametric Amplifier  Multi wavelength pulse sources based on saturated OPA without spectral broadening  SRS + Parametric processes  All optical tunable delay line via Slow and fast light propagation in a narrow band parametric amplifier : a route to optical buffering
  4. 4. 4 Motivations 1300 1400 1500 1600 U Fiber Type Standard AllWave FiberLoss(dB/km) 0.15 EDFA 0.25 0.35 C LS+ S TDFA GS-TDFA GS-EDFA Raman, OPA Optical Wavelength (nm) How can we cope with the increasing demand in information capacity?
  5. 5. Motivations Operation over these extremely large optical bandwidths requires that several key components be developed !  All optical processing devices :  Wavelength converter and re-shapers  All optical buffers  High bit rate stable optical pulse sources  Low jitter self starting source  Multi wavelength source  Wide Band Amplifiers (Raman, OPA)  Noise properties
  6. 6. 6 Inter band Raman - Mediated Wavelength Converter with Noise Reduction Capabilities
  7. 7. 7 Raman wavelength converter : Principle of operation Signal at wavelength λs t t P1s P0s Ppr t t Probe : λpr~ λs-100 nm, Ppr<<P1s Optical fiber (L km) Large detuning may degrade the conversion because of large walk off Need to operate almost symmetrically around the zero dispersion wavelength
  8. 8. 8 Raman wavelength converter : Principle of operation  Fast Raman response - few fs  Strong depletion regime (Ps>>Ppr)        (0) exp (0) (0)exp pr s s R s eff pr pr P L D P C P L P L     1 exp( )s s eff s L L      R p s R eff g f f C KA  
  9. 9. 9 Experimental set up: wavelength conversion λ λ 0~1536.3 nm λsλpr Highly Nonlinear Fiber : γ~ 10.6 W-1/km, λ0~1536.3 nm ,S0~ 0.018 ps/(nm2-km) ~100 nm
  10. 10. 10 Experimental result : wavelength conversion Ramaninduceddepletionat1483nm inCWregime[dB] -5 10 15 20 25 -16 0 5 -14 -12 -10 -8 -6 -4 -2 0 0 2 4 6 8 10 12 14 16 Theory Measurements Input Power at 1584 nm [dBm] Extinctionratioat10Gb/s forprobesignalat1491nm[dB] ER Measurements+ CR~3.7 W-1 /Km extracted from CW measurement
  11. 11. 11 Experimental set up : wavelength conversion with reshaping capabilities
  12. 12. 12 Converted Signal, p=1500 nm Reshaping results @ 10 Gbit/s Original Signal, s=1581 nm
  13. 13. 13 Reshaping results @ 10 Gbit/s Original Signal, s=1581 nm Converted Signal, p=1490 nm
  14. 14. 14 Reshaping results @ 10 Gbit/s Original Signal, s=1581 nm Converted Signal, p=1480 nm
  15. 15. 15 Reshaping results @ 10 Gbit/s Original Signal, s=1581 nm Converted Signal, p=1470 nm
  16. 16. 16 BER measurement at 10 Gbit/s : Large crosstalk : -13 dB -28 -26 -24 -22 -20 -18 -16 -14 -14 -12 -10 -8 -6 -4 -2 0 Received optical power [dBm] Signal @1581 nm Converted signal @1495 nm Converted signal @1485 nm Converted signal @1480 nm Converted signal, p =1495 nm, Q=8 Original Signal, s =1581 nm, Q=3.5 Log10(BER)
  17. 17. 17 BER measurement at 10 Gbit/s : Moderate crosstalk : -18 dB Converted signal @1495 nm Converted signal @1485 nm -28 -26 -24 -22 -20 -18 -16 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 Received optical power [dBm] Converted Signal, p=1495 nm Q=10 Signal @1581 nm Original Signal, s=1581 nm Q=5.5 Converted Signal, p =1485 nm, Q=9.6 Log10(BER)
  18. 18. 18 Numerical simulations : operational bandwidth Converted Wavelength [nm] OutputQfactor[dB] 1470 1480 1490 1500 1510 1520 7 8 9 10 11 12 13 14 15 Extinction Ratio 7 8 9 10 11 12 13 14 15 Q factor OutputExtinctionRatio[dB] λs=1581 nm, Ps=21 dBm, Q=7.8 Operational conversion bandwidth = 35 nm
  19. 19. 19 Slow and fast light propagation via narrow band optical parametric amplifier : a route to optical buffering
  20. 20. 20 Motivations  Tunable optical pulse delays are of central importance to numerous fields including optical coherence tomography, ultra-fast pulse metrology, and optical communications.  Next Internet Router generation will be based on all optical packet switching : Need to develop all optical buffering devices.  Promising approach : controlling the velocity of optical pulses through dispersive media, a concept termed as slow and fast light
  21. 21. 21 Speed of light  The velocity of a pulse of light is determined by the group index ng : vg=c/ng with c the speed of light in vacuum (c=300 000 km /s).  The group index is determined not only by the refractive index of the medium but also by the dispersive characteristics of the structure : g n n n       Refractive index Dependence of refractive index on the light frequency
  22. 22. 22 Dispersion Near a Resonance refractive index n n in   ' " 1 2 group index ng (max) 105 n(max) . 01 !!  Index, Re(χ)  Group index ng  Absorption, Im(χ) Narrower absorption line Larger index slope
  23. 23. 23 Slow Light Observations of Hau et al. The speed of light can be slowed down using the absorption rays in an ultra cold atomic gas : this requires a complex experimental set up which is not practical for commercial application
  24. 24. 24 Other media  SC Waveguide (Passive and active) – Limited by carrier life time. Maximum delay one bit.  Ruby Crystal – large delay narrow bandwidth  Rubidium vapor – Large delays ultra narrow bandwidth and large attenuation  Nonlinearities in optical fibers may, on the other hand, offer optical gain in addition to other advantages such as a broad range of operating wavelengths, operation at room temperature and flexible length
  25. 25. 25 Slow and Fast Light via Stimulated Brillouin Scattering Positive and negative delays up to 30 ns have been obtained for pulse with large width (20 ns) using Stimulated Brillouin Scattering in fiber. (Boyd et. Al) The Stimulated Brillouin scattering can be used only for wide pulses (several ns). This is not practical for high bit rate applications which require pulse width of 100 ps and lower. Need to find another process to generate a narrow band gain spectrum in the fiber but large enough to amplified picosecond pulses
  26. 26. 26 Narrow band Optical Parametric Amplifier (OPA) A partially degenerated OPA usually operates in the anomalous dispersion regime of the fiber. A significant parametric gain is obtained as usual for frequencies satisfying -4γP0<Δk<0 With When the pump wave propagates in the normal dispersion regime of the fiber (β2>0) with a negative fourth order dispersion parameter (β4<0) the phase matching condition occurs far from the pump wavelength.     2 4 2 4 12s p s pk          
  27. 27. 27 Phase mismatching as a function of the wavelength λ0=1539 nm, λp=1530 nm, γ=2.5 W-1km-1, P0=10W, λs1=1377 nm, λs2=1721 nm 1400 1500 1600 1700 -50 0 50 100 150 200 Wavelength [nm] Δk/γP0 β4<0 β4>0 λ0 β2>0 β2<0 λs1 λs2 Phase matching
  28. 28. 28 ASE and gain spectra using 200 m long DSF with λ0=1539 nm The spectral separation between this narrow gain spectrum and λp increases while its width decreases as the spectral separation λ0-λp increases. The parametric process is coupled to Stimulated Raman Scattering (SRS) for |λp-λs| up to 150 nm. The narrow gain spectra are very sensitive to the longitudinal variations of λ0 along the fiber and lead to local variations of the group index
  29. 29. 29 System Set up
  30. 30. 30 Delay in high gain regime without SRS (|λp- λs |>150 nm)      2 3 2 42 6 2 g p p c d k c d k n c d d                      Short wavelength side Long wavelength side 1400 1500 1600 1700 -50 0 50 100 150 200 Wavelength [nm] Δk/γP0 0g g g g c n v n n       0g g g g c n v n n       Pulse delay Pulse advancement Slow light Fast light
  31. 31. 31 Theoretical gain and delay spectra Wavelength [nm] OPAGain[dB] TimeDelay[ps] 1376 1376.5 1377 1377.5 1378 -5 0 5 10 15 20 25 30 35 40 -15 -10 -5 0 5 10 15 20 25 30 (a) Wavelength [nm] TimeDelay[ps] OPAGain[dB] (b) 1720 1720.5 1721 1721.5 1722 1722.5 -5 0 5 10 15 20 25 30 35 40 -15 -10 -5 0 5 10 15 20 25 30 (b) λp=1530 nm, P0=10 W, 200 m long DSF In both spectral regimes, the same maximum gain value of 34 dB and the maximum absolute value of the induced timing delay is 19 ps. Both delay spectra are large and quite flat over some 40 GHz where the gain exceeds 25 dB.
  32. 32. 32 Theoretical gain and delay spectra in Raman assisted OPA Wavelength [nm] OPAGain[dB] TimeDelay[ps] 1425 1426 1427 1428 1429 1430 1431 -10 0 10 20 30 40 -5 0 5 10 15 20 (a) Wavelength [nm] OPAGain[dB] TimeDelay[ps] 1656 1657 1658 1659 1660 1661 1662 5 10 15 20 25 30 35 40 -7.5 -5 -2.5 0 2.5 5 7.5 10 (b) λp=1535 nm, P0=10 W, 200 m long DSF  When |λp-λs|<150 nm, the parametric process is coupled with SRS  It causes enhancement of the delay in the short wavelength side whereas it reduces the time advancement at the long wavelength side
  33. 33. 33 Slow light observations - spectra  The spectra broaden and shift towards shorter wavelengths (since β4<0) as predicted by the numerically calculated gain spectra .  The coupling between the parametric process and SRS widens the gain spectra especially on the short wavelength side .  The somewhat wider experimental spectra are attributed once more to a longitudinal variation of λ0 along the fiber. 1425 1426 1427 1428 1429 1430 1431 -20 -10 0 10 20 30 40 50 60 70 1425 1426 1427 1428 1429 1430 1431 -70 -60 -50 -40 -30 -20 Wavelength [nm] Raman assisted parametric gain Parametric gain only Wavelength [nm] G=49 dB G=44 dB G=42 dB G=37 dB G=31 dB G=25 dB P0 + ASEPower[dBm] Gain[dB] P0 + λs λs
  34. 34. 34 Slow light observations Time [ps] 0 50 100 150 200 250 0 0.2 0.4 0.6 0.8 1 Normalizedintensity (a) (1)(2)(3)(4) 0 100 200 300 400 0 0.2 0.4 0.6 0.8 1 0 100 200 300 400 0 0.2 0.4 0.6 0.8 1 Normalizedintensity Normalizedintensity Time [ps] Time [ps] (c) (d) (1) (2)(3)(4)(5)(6) (1) (2)(3)(4)(5)(6) Normalizedintensity Time [ps] 0 50 100 150 200 250 300 350 0 0.2 0.4 0.6 0.8 1 (1) (2)(3)(4)(5)(6)(b) 200 m 500 m 1000 m 2000 m λs=1428.6 nm λp=1535 nm
  35. 35. 35 Measured delays as a function of parametric gain for different fiber lengths  For a fixed gain level, the delay increases with fiber length. However, the obtainable delay range decreases for very long fibers due to saturation.  There exists therefore an optimal length : 500 m long DSF offers a tunability range 146 % larger than the minimum delay. Delay[ps] 0 10 20 30 40 50 0 50 100 150 200 Gain [dB] L=200m L=500m L=1000m L=2000m
  36. 36. 36 Delay versus fiber length  200 m and 2000 m long Raman assisted OPA provide the same gain at λs  The overall delay which is the accumulative effect of the group index distribution is larger in the long fiber as predicted  The small tuning range of long fibers results from the fact that their minimum delay is large and they saturate rapidly 0 500 1000 1500 2000 0 0.5 1 1.5 2 2.5 x 10 -5 DSF length [m] Groupindexvariations λs λs λpeak Wavelength [nm] 1426.5 1427 1427.5 1428 1428.5 1429 -20 -10 0 10 20 30 40 50 60 70 OPAGain[dB] -5 2000 m long DSF 200 m long DSF λs λpeak
  37. 37. 37 Delay versus pump wavelength  The combined effects of SRS and parametric gain enhance the time delay at the spectral edges while the gain is decreased.  A slight signal broadening is noticeable in two cases:  When the signal is close to the peak gain, broadening is cause by saturation  when it is located at the spectral edge, there are strong group index variations which induce dispersion. 1428 1429 1430 1431 1432 -70 -65 -60 -55 -50 -45 -40 -35 -30 Wavelength [nm] λs ASEPower[dBm] (a) λp=1535 nm λp=1535.1 nm λp=1535.15 nm λp=1535.18 nm 0 50 100 150 200 0 0.2 0.4 0.6 0.8 1 1.2 Time [ps] (b) No gain G=30.4 dB, d= 11.3 ps G=24.5 dB, d=16.2 ps G=11.2dB, d=22.2 ps G=-5 dB, d=29.1 ps
  38. 38. 38 Fast light observations 0 50 100 150 200 0 0.2 0.4 0.6 0.8 1 Time [ps] NormalizedIntensity No gain G=24 dB, d= - 4.7 ps (a) 0 50 100 150 200 0 0.2 0.4 0.6 0.8 1 Time [ps]NormalizedIntensity No gain G=27 dB, d= - 11 ps (b)  For the present system, negative delay (fast light) occurs at wavelengths longer than the pump wavelength.  The longest available single mode laser operated at 1600 nm where the negative delay per unit length is small. Using 2 and 3 km long DSF we have demonstrated a pulse advancement of 4 and 11 ps respectively.
  39. 39. 39 Parametric Processes in fibers for optical pulse source generation
  40. 40. 40 A Self Starting Ultra Low Jitter Pulse Source Using Coupled Optoelectronic Oscillators with an Intra Cavity Fiber Parametric Amplifier
  41. 41. 41 Background and motivation  Timing stability is a performance limiter  Known sources of highly stable pulse trains Self-starting optoelectronic oscillators  Optoelectronic oscillator with an EO modulator  Interlocked microwave and mode locked diode lasers based optoelectronic oscillators Jitter level : Several tens of fs at 10 GHz repetition rate Actively mode locked laser ( fiber or diode )  Jitter level is dictated by high quality external drive microwave source Jitter level : Below 10 fs at 10 GHz repetition rate
  42. 42. 42 500 m HNLF MZ Modulator Polarization Controller TL1 EDFA EDFA AWG TL2 50% 50% OSA/PSA/AC OBPF3 Polarization Controller Polarization Controller OBPF2 OBPF1 (0.4 nm) p=1543.5 nm  Power Amplifier G IM Bias-T Photo-HBT Bias-T VB VC BPF 10 GHz Directional coupler G Experimental set up  OPA based pulse generating mechanism ( Hansyrd, 2001 ) s=1559 nm
  43. 43. 43 500 m HNLF 10 km DSF MZ Modulator Polarization Controller TL1 EDFA EDFA AWG TL2 50% 50% OSA/PSA/AC EDFA OBPF3 Polarization Controller Polarization Controller OBPF2 OBPF1 (0.4 nm) p=1543.5 nm OBPF4 PM BER  Power Amplifier G IM Bias-T Photo-HBT Bias-T VB VC BPF 10 GHz Directional coupler G Experimental set up  Additional source is needed for PM in order to elevate SBS threshold s=1559 nm
  44. 44. 44 500 m HNLF 10 km DSF MZ Modulator Polarization Controller TL1 EDFA EDFA AWG TL2 50% 50% OSA/PSA/AC EDFA OBPF3 Polarization Controller Polarization Controller OBPF2 OBPF1 (0.4 nm) p=1543.5 nm OBPF4  Power Amplifier G IM Bias-T Photo-HBT Bias-T VB VC BPF 10 GHz Directional coupler G  Nonlinear pump modulation reduces the need for phase modulation Experimental set up s=1559 nm
  45. 45. 45 Nonlinear pump modulation 0 2 4 6 8 10 0 0.2 0.4 0.6 0.8 1 Theory Measurements t t Normalizedtransmissionfunction Driving voltage V Mach-Zehnder modulator biased at transmission maximum
  46. 46. 46 Nonlinear pump modulation 0 2 4 6 8 10 0 0.2 0.4 0.6 0.8 1 Theory Measurements f [GHz] 10-10 fopt 20 GHz fc Normalizedtransmissionfunction Driving voltage V Driven by 10 GHz sinusoidal input produces optical pulses at 20 GHz Pulses are distorted by Mach-Zehnder imperfections
  47. 47. 47  Initial spectrum has more spectral components  Broader spectrum reduces the need for PM  Spectral lines at 10 GHz far from the carrier cause time domain distortion 0 50 100 150 200 0 0.5 1 1.5 2 1542.5 1543 1543.5 1544 1544.5 -40 -20 0 20 Nonlinear pump modulation Wavelength nm Time ps OpticalpowerdBm DetectedpowermW p Nonlinearly modulated pump Filtered pump
  48. 48. 48  Spectral lines at 10 GHz far from the carrier cause time domain distortion  Around 1the spectrum is of 10 GHz pulse train  Two missing lines cause the 20 GHz sub-pulses 0 50 100 150 200 0 0.5 1 1.5 2 0 50 100 150 200 0 0.5 1 1.5 2 1542.5 1543 1543.5 1544 1544.5 -40 -20 0 20 Nonlinear pump modulation Wavelength nm Time ps 1542.5 1543 1543.5 1544 1544.5 -40 -20 0 20 OpticalpowerdBm DetectedpowermW p 1 Nonlinearly modulated pump Filtered pump
  49. 49. 49 -60 -40 -20 0 20 40 60 0 0.2 0.4 0.6 0.8 1 -60 -40 -20 0 20 40 60 0 0.2 0.4 0.6 0.8 1 1510 1530 1550 1570 1590 -5 5 15 25 35 45 Pulse generation using OPA Wavelength nm Time ps GaindB Normalizedpower Pp = 30.4 dBm Pp = 23.9 dBm  Parametric gain level and bandwidth depend on pump power  acts as a discriminator eliminating the 20 GHz sub-pulses  At signal wavelength ( s ), 7.6 ps wide pulses are obtained. > 26 dB 6.5 dB Pump Signal Compressed signal
  50. 50. 50 -60 -40 -20 0 20 40 60 0 0.2 0.4 0.6 0.8 1 -60 -40 -20 0 20 40 60 0 0.2 0.4 0.6 0.8 1 -60 -40 -20 0 20 40 60 0 0.2 0.4 0.6 0.8 1 1510 1530 1550 1570 1590 -5 5 15 25 35 45 Pulse generation using OPA Wavelength nm Time ps GaindB Normalizedpower Pp = 30.4 dBm Pp = 23.9 dBm  Pulses are chirped and can be linearly compressed Pump Signal Compressed signal
  51. 51. 51 1557 1558 1559 1560 1561 -60 -40 -20 0 1557 1558 1559 1560 1561 -60 -40 -20 0 1526 1527 1528 1529 1530 -60 -40 -20 0 0 50 100 150 200 0 1 2 3 4 Pulse source spectra  Broad signal and idler spectra : FWHM of 1.4 nm - 1.5 nm Wavelength nm Time ps OpticalpowerdBm DetectedpowermW Signal Idler 0.01 nm resolution 30 GHz detection bandwidth
  52. 52. 52 -20 -10 0 10 20 0 0.2 0.4 0.6 0.8 1 -20 -10 0 10 20 0 0.2 0.4 0.6 0.8 1 Autocorrelation traces Experiment Accumulated dispersion ps/nm FWHMps 0 5 10 15 2 4 6 8 10 12 14 Simulation Delay ps Intensitya.u. Raw Comp. Signal Idler  Signal : TFWHM = 3.4 ps ( 7.6 ps ) , TBP = 0.58  Idler : TFWHM = 3.0 ps ( 7.8 ps ) , TBP = 0.57  Pump induced XPM causes significant chirping  can be compensated linearly by an anomalous dispersion
  53. 53. 53 Comparison with results using sinusoidal pump modulation with phase modulation @ 500 Mbps Wavelength [nm] 1542 1543 1544-60 -40 -20 0 [dBm] 1526 1527 1528 -70 -50 -30 -10 10 1557 1558 1559 1560 -70 -50 -30 -10 10 [dBm][dBm] 100 ps PumpSignalIdler Δλs=0.41 nm TFWHM=9.5 ps (after compression) TBP=0.45 Δλs=0.39 nm TFWHM=9 ps (after compression) TBP=0.47 Δλs=0.16 nm TFWHM=37 ps
  54. 54. 54  Phase noise ( timing jitter ) is substantially reduced 500 m HNLF 10 km DSF MZ Modulator Polarization Controller TL1 EDFA EDFA AWG TL2 50% 50% OSA/PSA/AC EDFA OBPF3 Polarization Controller Polarization Controller OBPF2 OBPF1 (0.4 nm) p=1543.5 nm OBPF4  Power Amplifier G IM Bias-T Photo-HBT Bias-T VB VC BPF 10 GHz Directional coupler G  Pulse spectra doesn’t undergo any noticeable change when system becomes locked 500 m HNLF MZ Modulator Polarization Controller TL1 EDFA EDFA AWG TL2 50% 50% OSA/PSA/AC OBPF3 Polarization Controller Polarization Controller OBPF2 OBPF1 (0.4 nm) p=1543.5 nm  Power Amplifier G IM Bias-T Photo-HBT Bias-T VB VC BPF 10 GHz Directional coupler G Experimental set up s=1559 nm
  55. 55. 55 Signal jitter estimation 10 2 10 3 10 4 10 5 10 6 -120 -100 -80 -60 0 1 2 3 4 5 0 0.5 1 1.5 2 0 1 2 3 4 5 0 0.5 1 1.5 2 100 Hz – 15 kHz 500 Hz – 1 MHz 100 Hz – 1 MHz Measured Curve fitted 1st harmonics 2nd harmonics 3rd harmonics 4th harmonics Offset frequency Hz PhasenoisedBc/Hz Harmonics number σ2·104  Estimated jitter levels  100 Hz – 15 kHz : 29.6 fs  500 Hz – 1 MHz : 28.9 fs  100 Hz – 1 Mhz : 39.8 fs
  56. 56. 56 0 1 2 3 4 5 -0.5 0 0.5 1 1.5 2 2.5 0 1 2 3 4 5 -0.5 0 0.5 1 1.5 2 2.5 10 2 10 3 10 4 10 5 10 6 -120 -100 -80 -60 Idler jitter estimation 100 Hz – 15 kHz 500 Hz – 1 MHz 100 Hz – 1 MHz Measured Curve fitted 1st harmonics 2nd harmonics 3rd harmonics 4th harmonics Offset frequency Hz PhasenoisedBc/Hz Harmonics number σ2·104  Estimated jitter levels  100 Hz – 15 kHz : 49.7 fs  500 Hz – 1 MHz : 34.3 fs  100 Hz – 1 Mhz : 58.8 fs
  57. 57. 57 Multi wavelength pulse sources based on saturated OPA without spectral broadening
  58. 58. 58 Motivations  For high bit rates and long transmission distances RZ format is more robust than NRZ format  In RZ-WDM systems , it is necessary to develop laser pulsed sources at high bit rate for each channel  A cost effective way is to use CW sources and to create RZ pulses for all the channels simultaneously
  59. 59. 59 Multi-wavelength pulse source : principle of operation HNLF CW CW MZ Pump λp λs Signal λp λsλid1 λid2λid3λid5 λid4 A high input CW signal saturates the OPA : high FWM orders are generated
  60. 60. 60 2Δf3Δf Phase modulation induced spectral broadening  Phase modulating the pump to increase SBS threshold leads to severe spectral broadening for FWM product waves.  Channel quality degraded through phase to intensity noise conversion via dispersion λp λs λid2 λid1 λid3 Δf Δf
  61. 61. 61 2Δf3Δf Phase modulation induced spectral broadening  The degradation is enhanced with the FWM order λp λs λid2 λid1 λid3 Δf Δf
  62. 62. 62 Experimental Set up
  63. 63. 63 OPA spectrum 1480 1500 1520 1540 1560 1580 1600 1620 -70 -60 -50 -40 -30 -20 -10 0 10 20 wavelength [nm] Opticalpower[dBm] no signal Ps in=-17 dBm Ps in=-7 dBm Ps in=3 dBm signalIdler 1 Idler 2Idler 3 Pump
  64. 64. 64 Channel pulse sources at 10 GHz Δ λ= 0.98 nm 1558 1560 1562 1564 -60 -40 -20 0 Opticalpower[dBm] 1538 1540 1542 1544 1546 -60 -40 -20 0 Δ λ= 0.9 nm 1567 1569 1571 1573 1575 -60 -40 -20 0 Δλ=0.9 nm 1529 1531 1533 1535 -50 -30 -10 10 Wavelength [nm] Δλ=0.9 nm Signal λs=1561.nm Idler1 λid1=1542nm Idler2 λid2=1571nm Idler3 λid3=1531.5 nm ΔT=6ps Δf ΔT=0.72 ΔT=5.6ps Δf ΔT=0.64 ΔT=5.8ps Δf ΔT=0.63 ΔT=6ps Δf ΔT=0.69
  65. 65. 65 Timing Jitter estimations 0 50 100 150 100 Hz – 15 kHz 500 Hz – 1 MHz 100 Hz – 1 MHz TimingJitter[fs] Signal Idler 1 Idler 2 Idler 3
  66. 66. 66 Conclusion  Various aspects of Raman and parametric mediated amplification and all optical processing have been investigated.  Beside its use for Raman amplification, SRS can be used in absorption regime as inter band wavelength converter with reshaping capabilities.  Tunable all optical delay and advancement can be produced via narrow band gain spectra produced through Raman assisted optical parametric amplification  Parametric effects offer quantitative and qualitative methods for high bit rate and low jitter pulse sources.  All these all optical devices provide key tools toward the development of the next generation high bit rate optical fiber systems

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