采用后向散射法对B6类光纤模场直径的测量

Application of Back-Scattering Method on the Measurement of MFD of B6 Optical Fiber

弯曲损耗不敏感光纤(B6类光纤)已广泛应用于光纤入户(FTTH)和接入网网络改造中。相对于传统的直接远场扫描法、远场可变孔径法、近场扫描法,后向散射法是一种新型的光纤模场直径测试方法。后向散射法主要利用常规光时域反射仪(OTDR)通过双向测量法对光纤接头损耗的精确测定以及在测试中对高阶模影响的有效控制,使其测得的弯曲损耗不敏感光纤的模场直径与可变孔径法(试样长度≥22m)测得的模场直径具有很好的一致性。此外,利用后向散射法测得的1 310nm和1 550nm双波长下的模场直径结果还可进一步计算得弯曲损耗不敏感光纤的截止波长。由此,后向散射法为光纤光缆厂家提供了一种低成本、经济高效的测试手段。

Bend-insensitive fiber（B6 optical fiber） has been widely used in FTTH and access network cabling update. Compared with the traditional testing methods, such as direct far-field scanning method, far-field variable aperture method and near-field scanning method, back-scattering method is a new method for measuring the mode field diameter （MFD） of optical fibers. The back-scattering method mainly uses the conventional optical time domain reflectometer （OTDR） to accurately determine the optical fiber splicing loss by bi-direction measurement, and effectively controls the influence of the high-order mode in the test, so that the bend-insensitive fiber MFD measured by back-scattering method is in good agreement with the bend-insensitive fiber MFD measured by variable aperture method （the sample length is more than 22 m）. Further more, the cut-off wavelength of the bend-insensitive fiber can be further calculated by the MFD at the 1 310 nm and 1 550 nm dual wavelengths measured by back-scattering method. Thus the back-scattering method provides a low-cost, economical and efficient testing method for optical fiber and cable manufacturers.