Presenter: Heng Kong Date: 2013-4-9

1. Distributed Brillouin sensing with sub-meter spatial resolution based on four-section pulseOM3G.3(OFC2013) Presenter: Heng Kong Date: 2013-4-9

2. Outline • Content • 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)

3. Background • Rayleigh Scattering • Raman Scattering • Brillouin Scattering • Fresnel Reflection • Brillouin Scattering • Spontaneous Brillouin Scattering • Stimulated Brillouin Scattering

4. Introduction Distributed fiber sensors based on Brillouin optical time-domain analysis(BOTDA):

5. 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.

6. Experimental results and discussion 1mW 25℃ 10.818GHz(10m) 70℃ 10.856GHz(50cm) 50:50 20dBm 1550nm 3kHz 700MHz α:100mW β:1mW β’:120mW γ:100mW 500MHz 1G/s 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.

7. 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.

8. Conclusion • A novel Brillouin distributed fiber sensor based on four-section 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

9. Thank You ! More details: http://www.ofcnfoec.org/home/ http://front.sjtu.edu.cn/~llyi/waveguide