利用反射率影像量測光纖端面之折射率分佈

Refractive Index Profi ling of Various Optical Fibers

直接利用影像擷取方式來量測端面斷切各種光纖之反射影像強度，直接推算光纖端面橫截面多波長的折射率分佈曲線，這是首次使用顯微鏡搭配鹵素燈源直接用來量測光纖端面折射率之研究。透過所發展的量測方法，在各種光纖上的第一面絕對反射率可以被精確地測量，並可以推得在波段400 nm至1100 nm多個波段下之折射率分布。本研究所提出的方法不僅適用於一般單模光纖，亦可適用於多模光纖或光纖預型體。 A direct image method of surface refl ectivities on a cleaved fi ber end with a halogen lamp illumination to measure the refractive index profi ling(RIP) is proposed in this study. A polished black glass with a surface fl atness l /20(l = 632.8nm) is used to be the reference standard for measuring the spectral refl ectivity of the fi ber end. By the image calibration between the fiber end and the black glass, not only the nonuniformity of the sensitivity but also the spectral responsivity of the CCD pixels is eliminated to achieve the high spatial accuracy. Various measuring errors such as a fi ber terminator, oblique incident on the fi ber end and the intensity fl uctuations of the lamp are improved to precisely measure the RIP. The RIP of various fi bers such as a single-mode fi ber, ultra-high numerical aperture fi ber, a graded-index fi ber can be precisely measured to verify the system performance. The resolution and accuracy for measuring RIP on the cleaved fi ber end can be achieved about ~0.001 and ~0.003, respectively.