Gregory Scott Glaesemann

Analysis of single mode bent fiber failure under high power conditions

Optical fiber networks are being developed that require higher optical power levels. Examples include long haul communication with Raman amplification and fiber to the premises. Previous studies indicate that tightly bent optical fiber can mechanically fail when exposed to high optical power levels. In an extreme case where fiber is sharply bent and subjected to a power level of 1 to 2 W in the near-infrared wavelength window, optical fiber can fail in minutes. It also has been shown that time to failure decreases with increasing bend stress and optical power. This study is a further investigation of the physical events leading to failure. Previously we demonstrated that the optical signal that escapes the core of bent fiber passes into the coating, where a small amount is absorbed and converted to heat. As a result the coating can be heated to significant temperatures resulting in degradation over time. This paper focuses on several key aspects of the failure kinetics associated with bent fiber under high power. As a result of bending, optical power leaked from the core is distributed in the glass cladding and polymer coating. We have modeled this power distribution and compared it with measured temperature profiles in the coating. The results show that this redistribution of the power is key to establishing the distribution of temperature in the coating and ensuing degradation. This understanding is used to design glass and coating solutions for inhibiting this potential failure mode.