Optical Fiber Slow Cooling for Structural Relaxation
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Solution Overview
Problem
The high fictive temperature and attenuation in optical fibers due to rapid cooling and high draw speeds during manufacturing, which limits the structural relaxation of glass, resulting in elevated signal loss.
Innovation Solution
A system and method involving multiple passes through a slow cooling device with a temperature range of 1000° C. to 1400° C., combined with fluid bearing devices to extend the residence time of optical fibers in the glass transition region, facilitating complete structural relaxation and reducing fictive temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast draw speeds and rapid cooling are used during optical fiber manufacturing, then productivity is improved, but the fictive temperature and attenuation increase due to insufficient structural relaxation of glass
Solution Approach 1:
The patent applies preliminary action by implementing a slow cooling zone immediately after the draw furnace, where the fiber is cooled at a controlled rate (10-100°C per second) before entering the buffer coating zone. This preliminary slow cooling allows structural relaxation to occur before the fiber is pulled at high speed through the coating process, thereby reducing fictive temperature and attenuation while maintaining high productivity.
Solution Approach 2:
The manufacturing process is segmented into distinct zones: a draw furnace zone, a slow cooling zone with controlled cooling rates, and a buffer coating zone. This segmentation allows each zone to perform its specific function - the slow cooling zone specifically addresses structural relaxation without interfering with the high-speed drawing and coating processes, thus resolving the contradiction between speed and quality.
2Reliability
If slow cooling is used to reduce fictive temperature and attenuation, then optical fiber quality is improved, but the residence time in the glass transition region remains too short to achieve complete structural relaxation
Solution Approach 1:
The patent introduces an additional spatial dimension by inserting a dedicated slow cooling zone between the draw furnace and the buffer coating apparatus. This additional zone provides extended residence time (0.5-10 seconds) in the glass transition temperature region, allowing complete structural relaxation without compromising the overall draw speed or productivity of the manufacturing process.
3Reliability
If extended residence time in the glass transition region is provided, then structural relaxation is improved and fictive temperature is reduced, but the manufacturing process complexity increases
Solution Approach 1:
The patent merges the slow cooling function with the existing buffer coating application process. The buffer coating zone serves dual purposes: applying the protective coating and providing the slow cooling environment through controlled thermal conditions. This integration achieves extended residence time and complete structural relaxation without adding separate complex cooling equipment, thereby minimizing process complexity while improving fiber quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the fictive temperature and attenuation of optical fibers, achieving lower signal loss and improved optical properties by prolonging the exposure time to the glass transition region.
Implementation Method 1
slow cooling of the fibers in the glass transition region and in the sub-Tg region
Implementation Method 2
increased relaxation of the glass can be induced
Implementation Method 3
the cooling rate of the optical fiber is reduced to facilitate structural relaxation of the glass
Data Source
AI summary
A system for processing an optical fiber includes: a draw furnace, the draw furnace containing an optical fiber preform; a bare optical fiber drawn from the optical fiber preform, the bare optical fiber extending from the draw furnace along a process pathway; and a slow cooling device operatively coupled to and downstream from the draw furnace, the slow cooling device exposing the bare optical fiber to a slow cooling device process temperature in the range from 1000° C. to 1400° C., wherein the bare optical fiber passes through the slow cooling device at least two times.