Transcript 4 Chromatic Dispersion Measurement for Time Lenses

Optoelectronics Circuits & Systems Lab
OCDMA Optical
Source Development
April 16, 2005
Jason Chou, Ozdal Boyraz, and Bahram Jalali
University of California, Los Angeles
Optoelectronics Circuits & Systems Lab
Goal
 Conventional supercontinuum source
produces broadband spectrum, where only
small portion is used
 Goal is to create spectrum only where it is
needed
 Approaches:
• Broadband comb generations
• Asymmetric comb generation
Optoelectronics Circuits & Systems Lab
SC-enhanced Mode Locked Source
MLL
Filter
DS Fiber
EDFA
• Requires only a few longitudinal modes from the mode locked laser
• Simplifies design
• Extend the spectrum to create a broad comb of frequencies of
multi-THz bandwidth by super-broadening
• Decouples the laser design from the spectrum requirement of OCDMA
Optoelectronics Circuits & Systems Lab
Broadband Spectral Comb Generation
ML
Laser
Line Selection
Filter
DS Fiber
EDFA
p
p
p
•Desired lines are selected from MLL spectrum
•Act as seed for generating desired spectral lines
•Generation achieved using SPM and FWM in nonlinear media
Optoelectronics Circuits & Systems Lab
Asymmetric Broadband Spectral Comb
Generation
DSF1
Seed
Pulse
DSF2
DSF3
AWG
EDFA
p
p
DS Fibers
p
•Spectrum location is optimized using dispersion
slope engineering
Optoelectronics Circuits & Systems Lab
Numerical Simulation
Starting Spectrum
After FWM in single mode fiber
Asymmetry
Optical Frequency
Optical Frequency
•Asymmetry in spectrum can be induced through dispersion slope
•Effect is modest in standard single mode fiber
•Can be drastic in dispersion engineered media
Optoelectronics Circuits & Systems Lab
Experimental Demonstration
Conventional Supercontinuum
Generation
40
30
Output Spectrum
Power [dBm/nm]
20
10
0
-10
Input
Seed
-20
-30
-40
1525
1530
1535
1540
1545
1550
1555
1560
1565
1570
Wavelength [nm]
•Independent control of channel separation and total bandwidth
•Power is concentrated in discrete OCDMA channels
•>25nm bandwidth
•Promising approach
1575
Optoelectronics Circuits & Systems Lab
Next Steps
 Dispersion engineering will be investigated by cascading fibers
with dispersion tailored profiles to improve efficiency and
flatten channel profile.
 Dynamic range per channel is limited by ASE-FWM beating
effect which can be mitigated by adding narrowband optical
filters to suppress EDFA noise background.
 Alternative approach to improve FWM efficiency and reduce
noise is to filter and overlap MLL pulses before passing
through dispersion engineered fibers.