Polymer claddings with low refractive indices for silica core fibers were developed. Applications include fiber
lasers and transmission of high power lasers in surgery. For many applications, operating fibers under high
temperatures is desirable. In a previous publication, the results of testing polymer cladded silica core fiber at 150°C
for 6400 hours were given, along with 5000 hours of testing polymer films. The results at 150°C were encouraging,
with little additional loss measured. Here we test polymers under more severe conditions, at 270°C, for periods up
to 10 hours. The polymers' cured indices range from 1.374 to 1.397 (at 852 nm). Changes in Young's modulus,
refractive index, yellowing, weight, hardness, strength, and elongation were observed. While these polymers cannot
function at 270°C for extended periods, it is possible to expose them for shorter durations without significant
damage. Some polymer properties actually improved after 4 hours of heating. Fibers clad with such polymers have
been successfully jacketed with extruded materials, and have endured high temperatures for a few minutes. It is
possible that a sensor, fiber laser or other fiber device could function in these temperatures for short periods without
the coating properties changing beyond values required for operation.
Low index polymer claddings were developed and tested for use with silica core fibers. Polymers with varying indices of
refraction were developed, so that numerical apertures useful for multiple applications were produced. High transmission
over a wide wavelength range was obtained, both for films and for clad fibers. A refractive index as low as 1.363 was
achieved, which results in a numerical aperture of 0.50 (at 852 nm) when used in cladding silica cores. Results for fibers
clad with 1.373 index material under high temperatures (150 °C) show that worst case change in loss was within 0.084
dB, even over a time frame of 6400 hours.
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.