| 摘要 |
PURPOSE:To obtain a constant polarization type optical fiber with a small loss up to a longer wavelength zone by adopting a 4-layered sectional structure, using GeO2-F2O-SiO2 glass as the material of the 2nd elliptical clad, and making the refractive index of the clad higher than that of the 1st clad made of high purity SiO2. CONSTITUTION:The 1st concentric clad 2 made of high purity SiO2 is formed around a glass core 1. The refractive index of the clad 2 is lower than that of the core 1. The 2nd clad 3 made of GeO2-F2O-SiO2 glass and having an elliptical section is formed around the 1st clad 2. The refractive index of the clad 3 is lower than that of the core 1 and higher than that of the 1st clad 2. The 3rd clad 4 having a lower refractive index than the 2nd clad 3 is further formed around the clad 3. Thus, the desired constant polarization type optical fiber is obtd. Since the 2nd elliptical clad is made of GeO2-F2O-SiO2 glass without using B2O3, the loss of the fiber is small up to a longer wavelength zone and the fiber has superior polarizing characteristics. |
