1. D. Dahan, A. Bilenca, R. Alizon and G. Eisenstein
Noise Reduction Capabilities of a Raman - Mediated Wavelength Converter  
D. Dahan, A. Bilenca, R. Alizon and G. Eisenstein
Technion- Israel Institute of Technology
Department of Electrical Engineering

2. Outline Motivation Raman wavelength converter : Principle of operation
Experimental set up and results
Wavelength conversion
Reshaping capabilities
Numerical Simulations
Conclusion

3. Motivations
How can we cope with the increasing demand in information capacity?
Fiber Type
Standard
AllWave S+ S C L U
0.35
Raman
GS-EDFA
Fiber Loss (dB/km)
0.25
EDFA
GS-TDFA
TDFA
0.15
1300
1400
1500
1600
Optical Wavelength (nm)

4. Raman wavelength converter : Principle of operation
Signal at wavelength λs
Optical fiber (L km)
P1s
P0s t t
Ppr t t
Probe : λpr~ λs-100 nm, Ppr<<P1s
Large detuning may degrade the conversion because of large walk off
Need to operate almost symmetrically around the zero dispersion wavelength

5. Raman wavelength converter : Principle of operation
Fast Raman response - few fs
Strong depletion regime (Ps>>Ppr) *

6. Experimental set up: wavelength conversion
Signal
HNLF 4 km
L band
EDFA
OTF
1584nm
WDM couplers
1480/1550
100 MHz PC
Mod
10 Gbit/s Data
Probe TL RX nm λ D
λ 0~ nm λs
λpr
Highly Nonlinear Fiber :  ~ 10.6 W-1/km, 0~ nm ,S0~ ps/(nm2-km)

7. Experimental result : wavelength conversion
Raman induced depletion at 1483 nm
in CW regime [dB] -5 10 15 20 25
-16 5
-14
-12
-10 -8 -6 -4 -2 2 4 6 8 12 14 16
Theory
Measurements
Input Power at 1584 nm [dBm]
for probe signal at 1491 nm [dB]
Extinction ratio at 10 Gb/s
ER Measurements +
CR~3.7 W-1/Km extracted from CW measurement

8. Experimental set up : wavelength conversion with reshaping capabilities
Receiver
HNLF 4 km
L band
EDFA
OTF
WDM
couplers
1480 /
1550 PC
Probe
Tunable
Laser
100
MHz
Mod 10
Gbit
s data
Signal % 90
SMF 2
Att
1581 nm
1470 -
1500

9. Reshaping results @ 10 Gbit/s
Converted Signal, p=1500 nm
Original Signal, s=1581 nm
Converted Signal, p=1495 nm
Converted Signal, s=1490 nm

10. Reshaping results @ 10 Gbit/s
Converted Signal, p=1485 nm
Converted Signal, p=1480 nm
Converted Signal, p=1470 nm
Converted Signal, p=1475 nm

11. BER measurement at 10 Gbit/s : Large crosstalk : -13 dB
-28
-26
-24
-22
-20
-18
-16
-14
-12
-10 -8 -6 -4 -2
Received optical power [dBm] nm
Converted nm
Converted nm
Converted nm
Converted signal, p =1495 nm, Q=8
Original Signal,
s =1581 nm, Q=3.5
Log10(BER)

12. BER measurement at 10 Gbit/s : Moderate crosstalk : -18 dB
Converted nm
Converted nm
-28
-26
-24
-22
-20
-18
-16
-14
-12
-10 -8 -6 -4 -2
Received optical power [dBm]
Converted Signal,
p=1495 nm Q=10 nm
Original Signal,
s=1581 nm Q=5.5
p =1485 nm, Q=9.6
Log10(BER)

13. Numerical simulations : formalism
Coupled Nonlinear schrodinger equation :
Solved using the split step Fourier method

14. Numerical simulations : noise transfer
CW regime, without walk off and modulation instability :
200
300
Input signal power (GPsin) [mW]
walk off=0 ps
walk off=10 ps
100
0.05
0.1
0.15
0.3
0.35
Noise Transfer ratio pr/s
walk off=40 ps
walk off =80ps
Simulations results
0.25
0.2

15. Numerical simulations : operational bandwidth
Converted Wavelength [nm]
Output Q factor [dB]
1470
1480
1490
1500
1510
1520 7 8 9 10 11 12 13 14 15
Extinction Ratio
Q factor
Output Extinction Ratio [dB]
Original nm, Ps(0)=21 dBm, Q=7.8

16. Conclusions
Raman mediated crosstalk : Novel technique for inter-band wavelength conversion and reshaping
Demonstration of conversion and reshaping capabilities from L to S bands at 10 Gbit/s
Fast Raman response allows operations to higher bit rates
Walk off is the main limiting factor but can be reduce by increasing the power or the fiber Raman gain.