实验研究了基于包层腐蚀型单模光纤(SMF)声光滤波器(AOTF)在不同加载声波频率以及不同包层腐蚀深度下的滤波特性。在声光作用下，光纤中基模(LP01)与包层模(LP11)的耦合效率随着包层直径的减小而增大；同一包层直径条件下，AOTF谐振波长随着声波频率的增加而发生“蓝移”。数值模拟了AOTF谐振波长随声波频率变化的趋势，模拟结果与实验数据保持较高的一致性。实验还分析了外加轴向应力对光纤型AOTF滤波特性的影响。结果表明，AOTF的谐振波长随着轴向应力的递增发生“红移”，这样就可方便地实现轴向应力调谐滤波；调谐带宽随着包层直径的增加而下降；加载声光频率与调谐带宽成反比。在包层直径d=35 μm，声光频率fa=1 MHz时，获得了超过150 nm的调谐带宽。

The filtering properties of all-fiber acousto-optic tunable filter (AOTF) based on cladding etched sing-mode fiber (SMF) are investigated experimentally. Influenced by the acousto-optic effcect, the acousto-optic coupling efficiency from LP01 core mode to LP11 cladding mode is enhanced by reducing the cladding diameter. At a fixed cladding diameter, the resonant wavelength of the AOTF shifts to the shorter wavelength side as the acoustic frequency increases. Moreover, the change of resonant wavelength with the acoustic frequency is numerically calculated and the simulation curves are in good agreement with the experimental results. The axial strain characteristics of all-fiber AOTF based on cladding etched SMF are analyzed experimentally. The results show that the resonant wavelength appears red shift as the increasing of axial strain, so it′s easy to achieve the tunable filter using the axial strain dependence. The tuning bandwidth is inverse to the acousto frequency and the cladding diameter. When the cladding diameter is kept at 35 μm and the acousto frequency is fixed at 1 MHz, an AOTF with tuning bandwidth greater than 150 nm is demonstrated.