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

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
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
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
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. 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
Inter band Raman - Mediated
Wavelength Converter with Noise
Reduction Capabilities

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
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
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
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
Experimental set up :
wavelength conversion with reshaping capabilities

12. 12
Converted Signal, p=1500 nm
Reshaping results @ 10 Gbit/s
Original Signal, s=1581 nm

13. 13
Reshaping results @ 10 Gbit/s
Original Signal, s=1581 nm Converted Signal, p=1490 nm

14. 14
Reshaping results @ 10 Gbit/s
Original Signal, s=1581 nm Converted Signal, p=1480 nm

15. 15
Reshaping results @ 10 Gbit/s
Original Signal, s=1581 nm Converted Signal, p=1470 nm

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
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
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
Slow and fast light propagation via
narrow band optical parametric
amplifier : a route to optical
buffering

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
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
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
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
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
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
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
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
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
System Set up

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
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
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
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
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
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
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
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
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
Parametric Processes in
fibers for optical pulse
source generation

40. 40
A Self Starting Ultra Low Jitter
Pulse Source Using Coupled
Optoelectronic Oscillators with an
Intra Cavity Fiber Parametric
Amplifier

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
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
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
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
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
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
 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
 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
-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
-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
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
-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
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
 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
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
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
Multi wavelength pulse sources
based on saturated OPA without
spectral broadening

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
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
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
2Δf3Δf
Phase modulation induced spectral
broadening
 The degradation is enhanced with the FWM order
λp
λs
λid2
λid1
λid3
Δf Δf

62. 62
Experimental Set up

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
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
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
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