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Simple Method for Stripping Polyimide-Coated Optical Fiber

Matthew Marshall, Jacob Williamson, Seth Hyra, Robert H. Leonard, Spencer E. Olson

TL;DR

Polyimide coatings on optical fibers are difficult to strip using conventional thermal, chemical, or mechanical methods and risk fiber damage. A simple chemical–mechanical approach soaks the fiber end in a $2:1$ methanol:$acetone$ bath (room temperature, ≳6 h) to swell and detach the coating, with heating to about $40^\circ C$ shortening the soak to ≈4 h. The 2:1 mix consistently yields the easiest stripping, with radial coating expansion up to about $6\,\mu\mathrm{m}$ and a solvent layer forming between coating and glass; drying can shrink the fiber by roughly $2\,\mu\mathrm{m}$ and reduce stripping ease, while vapor and capillary effects extend ease beyond the soaked length. This low-cost, low-risk method offers a practical alternative to burning, caustic chemistry, or commercial stripping machines for labs.

Abstract

We present a simple method for removing polyimide coatings from optical fibers using inexpensive and readily available solvents. Impacts of solvent mixing ratios, soak temperature, material expansion, wicking, and drying are described to provide empirical context for the method. We find that soaking fibers for six hours in a 2:1 mixture of methanol to acetone at room temperature enables easy stripping of a length slightly greater than the soak length.

Simple Method for Stripping Polyimide-Coated Optical Fiber

TL;DR

Polyimide coatings on optical fibers are difficult to strip using conventional thermal, chemical, or mechanical methods and risk fiber damage. A simple chemical–mechanical approach soaks the fiber end in a methanol: bath (room temperature, ≳6 h) to swell and detach the coating, with heating to about shortening the soak to ≈4 h. The 2:1 mix consistently yields the easiest stripping, with radial coating expansion up to about and a solvent layer forming between coating and glass; drying can shrink the fiber by roughly and reduce stripping ease, while vapor and capillary effects extend ease beyond the soaked length. This low-cost, low-risk method offers a practical alternative to burning, caustic chemistry, or commercial stripping machines for labs.

Abstract

We present a simple method for removing polyimide coatings from optical fibers using inexpensive and readily available solvents. Impacts of solvent mixing ratios, soak temperature, material expansion, wicking, and drying are described to provide empirical context for the method. We find that soaking fibers for six hours in a 2:1 mixture of methanol to acetone at room temperature enables easy stripping of a length slightly greater than the soak length.

Paper Structure

This paper contains 5 sections, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. Description of Method
  3. Testing Procedures
  4. Results and Discussion
  5. Conclusion

Figures (4)

  • Figure 1: An example of shredding typically encountered when attempting to strip an untreated polyimide-coated fiber. Note the glass fiber has also already cracked where indicated by the red arrow.
  • Figure 2: Fiber tips were soaked in a solvent mixture within a beaker. Any excess length of fiber passed through a pinhole in an aluminum foil covering to the beaker. The length of fiber submerged in the solvent and the length within the air gap are both much easier to strip after soaking.
  • Figure 3: Examples of a visible layer of solvent between the polyimide coating and glass fiber. These images were taken in succession over the course of about 30 seconds. The glass fiber is on the right side of each image. The left side shows the distended length of the polyimide coating. Note the iridescence that becomes clear in the last two images.
  • Figure 4: Two fibers pulled from the same 28-hour soak in 2:1 mixture. The upper image shows distention of about 2 mm, while the lower image shows distention below 1.4 mm, demonstrating the inconsistent nature of distention.