Ch9-Stimulated Brillouin Scattering
Stimulated Brillouin Scattering
Nonlinear Fiber Optics
Sep. 2005-Jan. 2006
Tel: +86-10-62282332 E -mail: xukun@https://www.360docs.net/doc/4f592039.html,
Key Lab of Optical Communication and Lightwave Technologies (Beijing University of Posts and Telecommunications), Ministry of Education, P.R.China
Dr. Kun Xu
Course Outline
1.Introduction
2.Pulse Propagation in Fibers
3.Group-Velocity Dispersion
4.Self-Phase Modulation
5.Optical Solitons
6.Polarization Effects
7.Cross-Phase Modulation
8.Stimulated Raman Scattering
9.Stimulated Brillouin Scattering
10.Parametric Processes
Stimulated Brillouin Scattering
1.Basic Concepts
2.Quasi-CW SRS
3.Dynamic Aspects
4.Brillouin Fiber Laser
5.SBS Applications
Basic Concepts
Brillouin Effect: 在分子介质中，自发拉曼散射将一小部分的入射功率由一光束转移到另一频率下移的光束中，频率下移量由介质的传声特性决定。
光子→散射→声子
Stokes波
与SRS的不同：
方向：SRS双向，SBS只有后向
频移：SRS大（－10T）SBS小（－10G）
阈值：SRS大，SBS小（－1mW)
参与的声子：光频声子和声频声子
?
of electrostriction. The acoustic wave in turn modulates the refractive index of the medium. This pump-induced index grating scatters the pump light through Bragg diffraction. Scattered
?
Quasi 准连续波时，泵浦波和s
B p s s p
B p s p dI g I I I dz dI g I I I dz
αα＝-+＝--在考虑线偏振时，布里渊增益减小为2/3
/21
B cr eff eff g P L A ≈布里渊增
益峰值
与偏振、掺杂、心径等有关。当纤芯有效
平方微米，有效长度20km ，布里11米/瓦时，阈值为1毫瓦
?0(0)/()/s s s in G I I L b b ==Gain Saturation
Variations in the pump and Stokes intensities along fiber length
由于泵浦消耗，净增益显著减小
Gain saturation in Brillouin
amplifiers for several values of GA
Dynamic Aspects
动态特性：泵浦脉宽大于()
()
()2
22
222
22*
22*12222
12222
1p
p p B p p s p s g s s s B s s p s p g B p s A A A i g A i A A A AQ z t t A A A i g A i A A A A Q z t t Q
T i Q A A t
βαγυβαγυδ??????????????＋＋＋＝＋－＋＋＋＝＋＋＋＋＝描述材料密
度的方程
()模耦合方程
11p
p B p s p g s s B p s s
g I I g I I I z t
I I g I I I z t
αυαυ????????＋＝－－－＋＝－当脉宽远大于声子寿命，GVD
在形成稳定值时，有弛豫振荡现象，如有外反馈，形成稳定振荡。可以通过引入微扰项的方法分析这一现象。
解释：由于泵浦波的消耗引起泵浦波波动，其放大能力减弱，在反方向形成波动。可以与激光器的强度调制过程相比－张弛振荡。
Relaxation Oscillations
Even though the group velocity vg is the same for the pump and the Stokes waves, their relative speed is 2vg because of their counterpropagating nature. Relaxation oscillations occur as a result of this effective group-velocity mismatch.
Brillouin Fiber Laser
?CW运转的布里渊激光器
z环形腔提高了泵浦的功率，
使阈值降低
z用于传感器
z FP腔的布里渊激光器的频谱
分量太多，有多条Stokes线
?脉冲运转布里渊激光器
z用周期脉冲泵浦特定光纤长
度的腔形布里渊激光器，形成
窄脉冲
z通过自脉动产生脉冲序列
?光纤布里渊放大器
z 对泵浦源的要求是单纵模且谱宽极窄z 放大的宽度窄，不适合用于光通信z 可以选择放大和窄带光通信?光纤传感器：分布的温度和应力传感器
SBS Applications
Schematic illustration of a Brillouin amplifier
Consideration in DWDM Design
?
?光纤放大器中使用隔
离器（阻断反向传播）
SBS vs. SRS
Email: xukun@https://www.360docs.net/doc/4f592039.html,
Tel: 86 -10 -62282332
Web: https://www.360docs.net/doc/4f592039.html, Thank You All for Your Attention! Any Questions and Suggestions are Welcome!