clock recovery by fp-fbgs –how things shape up? e source line width is narrower than the resonator...
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Clock recovery by FP-FBGs –How things shape up?
e source line width is narrower than the resonator bandwidth.
Optical Clock Recovery with Fabry-Perot FilterBased on Fiber Bragg Gratings
Nandu VS1,VT Gopakumar2, V P Mahadevan Pillai1, Madhusoodhanan3,Balaji Srinivasan4
1.Department of Optoelectronics, University of Kerala 2.VKCET,Dept of ECE,Parippally,Kerala,3.Department of
Instrumentation,CUSAT,Kerala4.Department of Electrical Engineering IIT Madras, Chennai, email:[email protected].
Theory of clock recovery by FP-FBGs
AbstractFabry-Perot filters based on fiber Bragg gratings are widely used as optical narrowband filters and as sensors. Here we propose and demonstrate all optical clock recovery with Fabry-Perot filters made up of fiber Bragg gratings.
Motivation
All optical signal processing,System synchronization,All optical timing extraction.
FP-FBG Fabrication Schematic
Simulation results
ConclusionsSo far complex methods are used for all optical clock recovery, here we described a simple in fiber and very stable passive optical clock recovery circuit.Above proposed Optical clock recovery circuits will be highly useful for optical signal processing system, such as all optical regenerative repeaters, all optical time division switching systems, and all optical de-multiplexers.
Acknowledgement I would like to thank my good old student Mrs.Ranju Aziz, (Faculty, Dept.of Opto Electronics, Kerala University) and Mr.Prshanth,(MS Scholar of
ESD @IITm) for their valuable help during the initial stage and measurement stage respectively.
FBG Writing Set up and characterization @ESD,IITm
FP-FBG Fabricated @ FBG writing facility @ ESD,
IITm
One of the pass bands of FP-FBGs is designed and fabricated to the center frequency of the incoming optical data stream. The
The FSR of the FP-FPG is equal to data clock frequencyThe source line width is narrower than the resonator bandwidth.Only the line spectral components , which contain the carrier frequency fo and the timing components fo±B are transmitted, this results in optical continuous timing clock extraction.
Continuous spectral components of RZ optical data
Line spectral components
Bitrate
FSR
Optical Spectrum of extracted Optical clock
FP-FBG filter Pass Bands
ExcimerLaser@248nm
Cylindricallens
Phase MaskHolder
Fiber Holder
Fiber translational stage
Light wave Measurement System
Tunable laser
Power Meter
Network cable
FP-FBGL
δL
δL=10mm L=3mmFSR=10.58Gneff=1.43Hz
(Photline MX-LN)
δL=10mmL=3mm
PIN PD+TIA
Tunable laser Source
10Gbps PRBS Generator
Optical intensity Modulator
FP-FBG
Polarization controller
Optical Receiver
ESA
The FSR of the FP-FPG is equal to data clock frequency
We got the FSR of 10.58GGz @ an effective cavity length of 10mm.We are trying to increase the cavity length so as to get the FSR of 10GHz,by holding the FP-FBG tightly in the fiber holder and paste it to a stick or by a Piezo-Electric resonator and characterize it again.We are also trying to write another FP-FBG with δL=10.484 mm long so as to get the FSR of 10GHz exactly to recover the clock.
Grating fabrication Real time simulation software
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5
x 1011
-150
-140
-130
-120
-110
-100
-90
f (Hz)
P (
dB
m)
3000 3500 4000 45000
0.5
1
1.5
2
2.5
x 10-13
Time(ps)
Am
plitu
de(a
rb.
unit)
Optical Spectrum @10Gbps, 231-1 PRBS RZ Power extinction of line Spectral component to Cont. Spectrum>50dB
Recovered clock@ 10GHz (not scaled)
FP-FBG SpectrumEffective cavity Length δL=10mmFBG Length L=3mm
λB=1550.8nmR=95%Power Extinction>30dB
Clock recovery simulation results
FP-FBG Experimental Set up for Optical clock recovery