Distributed Brillouin sensing with
sub-meter spatial resolution based on
four-section pulse
OM3G.3(OFC2013)
Presenter: Heng Kong
Date: 2013-4-9
Outline
 Content
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Introduction
Operation Principle
Experimental results and discussion
Conclusion
 Four-section pulse based Brillouin distributed fiber sensor
 sub-meter spatial resolution
 mitigate the secondary “echo” directly without extra measurement
time and post-processing algorithm”
State Key Laboratory of Information Photonics & Optical Communications (Beijing
University of Posts and Telecommunications)
Background
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Rayleigh Scattering
Raman Scattering
Brillouin Scattering
Fresnel Reflection
Brillouin Scattering
 Spontaneous Brillouin Scattering
 Stimulated Brillouin Scattering
Introduction
Distributed fiber sensors based on Brillouin optical timedomain analysis(BOTDA):
Problems
Solutions
Disadvantages
Spatial resolution <
1m
Pre-pulse, dark-pulse,πphase-shift pulse
Exits the secondary “echo”
Secondary “echo”
Differential pulse pair,πphase-shift pulse pair
The measurement time is
twice longer
Long measurement
time
Brillouin gain-profile
tracing; deconvolution
based method
Need use post-processing
algorithm
Operation Principle
Features:
 a)Higher spatial resolution than bright pulse; T determines the
spatial resolution
 b)T1 acts as sensing pulse;T2 plays the role of mitigating the
secondary “echo”; The longer T1, the longer T2
 c)four-section pulse is better
Fig.1. (a): dark pump pulse. T determines the spatial resolution; (b) four-section pump pulse. T1 determines the spatial resolution.
(c) Probe traces vs. position. Blue trace: probe trace based on dark pulse technique; Red trace: probe trace based on four section pulse
technique.
Experimental results and discussion
1mW
20dBm
1550nm
3kHz
25℃ 10.818GHz(10m)
70℃ 10.856GHz(50cm)
50:50
700MHz
α:100mW
β:1mW
β’:120mW
γ:100mW
β:5ns,β’:10ns
Fig. 2. Experimental setup.
PC: polarization controller: EOM: electro-optic modulator; EDFA: Erbium-doped
fiber amplifier; PD: photo-detector; PG: pulse generator.
500MHz
1G/s
Experimental results and discussion
观测到BFS
Fig. 3. (a) The 3D-mapping of Brillouin
gain versus both location and frequency
shift with dark pulse based technique.
(b) The 3D-mapping of Brillouin gain
versus both location and frequency shift
with four-section pulse based technique.
Fig. 4. (a) Top view of 3D-mapping with dark pulse based technique.
(b) Spectral gain curves at two typical locations with dark pulse based technique.
(c) Top view of 3D-mapping with four-section pulse based technique.
(d) Spectral gain curves at two typical locations with four-section pulse based technique.
Conclusion
A novel Brillouin distributed fiber sensor based on foursection pulse:
 Theoretical analysis and experimental demonstration
(10m long, 50cm spatial resolution)
 Mitigate the secondary “echo” phenomenon directly
 Hope it can help the development in future
Thank You !
More details:
http://www.ofcnfoec.org/home/
http://front.sjtu.edu.cn/~llyi/waveguide