There has been a rapidly increasing demand for the high numerical aperture (NA) in specialty optical fibers used in
recent high power fiber lasers and remote sensing applications. Various polymer clad resins (PCR) have been reported
aimed for a low refractive index to achieve a high NA, which resulted in a lower modulus. In this study, we report a
novel PCR with a higher modulus whilst maintaining a high NA over 0.44 using newly designed fluorinated oligomer
and monomer having low refractive index and high functionality. Some resins prepared various formulations using
synthesized oligomers and then compared curing speed.
In order to clarify the relationship between the water resistance and compositional additives in the primary coating for optical fibers, we prepared various primary coatings that contained silane coupling agents in combination with amine synergists. We observed the appearance of the interface between glass and primary coating after soaking in water at 65° for 30 days. Water resistance was found to be heavily influenced by the content and type of silane coupling agents and amine synergists and their trends are reported.
As GeO<sub>2</sub> concentration increased, residual stress increased. For the same tension, axial stress induced by drawing is
linearly proportional to GeO<sub>2</sub>-dopant concentration. The residual stress of the fiber (about axial direction) is originated
from phase distribution caused by photo-elastic effect: A phenomena that a fiber becomes birefringent through the nonisotropic stresses. The photo-elastic effect makes phase shift such that intensity difference of light is appeared. The phase profile is obtained by measuring the intensity difference. And phase profile can be converted to the stress profile by Abel transformation. The magnitude of stress induced by drawing tension, is different as glass material constitution. As material is the more viscous, induces the more stress. Generally the glass for which dopants such as Ge, B, P and F are added has lower viscosity value compared with pure silica glass. And as dopant concentration increased, viscosity decreased. We investigated the relation between GeO<sub>2</sub>-dopant concentration and the magnitude of residual stress. Perform core was deposited with Ge-Si ratio having parabolic increment about radial direction. GeO<sub>2</sub> concentration of core varied from 0 to 21.67mol%. That was also described to index change. The index difference (delta N) of core and clad was 0.026. The preform was drawn for fixed tension. Residual stress of optical fiber was measured after drawing. And fiber was fully annealed by flame. After then stress was measured one more. We obtained stress as the difference these two data: before and after anneal process. In fiber drawing process, tension was differently applied for each point
of core region so that the measured stress about radial direction was not correct. To compensate the error, stress of sample was referred to pure-silica rod of that.