I heard that some damaged optical fibers can be restored by heating them, is that true?
From a physics and materials engineering perspective, this statement is true under specific conditions of cutting-edge laboratory polymer materials and specific microscopic physical damage mechanisms, but it does not apply to the mechanical fracture of conventional engineering quartz optical fibers.
In the fields of optics and material science, “fiber heating recovery after damage” typically refers to the following two distinct physical mechanisms:
1. Cutting-edge Laboratory Stage: “Self-healing Polymer Optical Fibers”
In recent years, the materials science community has developed special polymer optical fibers based on dynamic covalent bonds or supramolecular hydrogen bond networks:
- Physical Mechanism: The core and cladding of these fibers are made of high molecular polymers with thermally reversible chemical bonds (e.g., thermally reversible crosslinking networks based on Diels-Alder reactions).
- Healing Process: When the fiber suffers mechanical cutting or micro-crack damage, the damaged ends are aligned, and a mild heat source (typically around 60\ ^\circ\text{C} \sim 100\ ^\circ\text{C}) is applied. The polymer molecular chains at the damaged interface dissociate due to thermal activation and undergo segmental diffusion. Subsequently, during cooling and rearrangement, covalent crosslinks reform, filling the cracks and thus restoring the fiber’s physical structure and light-guiding properties to some extent.
- Engineering Status: This technology is currently primarily in the proof-of-concept stage in universities and advanced materials laboratories. Its mechanical strength, optical transmission loss (much higher than ordinary optical fibers), and long-term environmental stability have not yet met the standards for large-scale industrial communication or sensing.
2. “Thermal Annealing of Radiation Damage” in Quartz Optical Fibers
For the core silica (\text{SiO}_2) based quartz optical fibers used in industry and communication, if the fiber is not physically broken but its transmission performance degrades due to extreme environments, heating can indeed produce a “self-healing” effect:
- Physical Mechanism: Under nuclear radiation, space rays, or high-energy ultraviolet light, micro-defects (i.e., “Color Centers”) form within the high-purity silica lattice, causing extremely high Radiation-Induced Attenuation (RIA) in the fiber, making normal optical signal transmission impossible.
- Annealing and Healing Process: When the fiber undergoes thermal treatment at a certain temperature (typically 100\ ^\circ\text{C} \sim 400\ ^\circ\text{C} or higher), the microscopic defects in the lattice gain thermal energy. Trapped electrons or holes are released, the color center structure gradually disappears, and the fiber’s transmittance and optical properties significantly recover. This phenomenon is known as thermal annealing recovery in optical engineering.
Can Mechanical Fractures of Conventional Quartz Optical Fibers be Recovered by Ordinary Heating?
No.
- The base material for conventional communication optical fibers and Fiber Bragg Grating (FBG) sensor fibers is quartz glass (high-purity \text{SiO}_2), which has a glass transition temperature exceeding 1000\ ^\circ\text{C} and a softening point typically above 1600\ ^\circ\text{C}.
- If a quartz optical fiber experiences macroscopic fracture or physical shattering, ordinary heating cannot make the molecules re-bond. It requires a specialized fiber fusion splicer, which uses localized high temperatures generated by high-voltage electric arcs at thousands of degrees Celsius to fuse the two ends together.
Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) Core Product Description
Polymer optical fibers with thermal self-healing capabilities belong to the domain of cutting-edge polymer materials research and are not part of Beijing Dacheng Yongsheng Technology Co., Ltd.'s (OFSCN®) core product line.
Beijing Dacheng Yongsheng Technology Co., Ltd.'s (OFSCN®) core industrialized product line focuses on specialty high-temperature quartz-based optical fibers, metalized optical fibers, and Fiber Bragg Grating (FBG) sensors. These quartz optical fibers, coated with Polyimide or encapsulated with gold/copper plating, can maintain high mechanical strength and stable optical reflection characteristics in harsh industrial environments ranging from -270\ ^\circ\text{C} \sim +700\ ^\circ\text{C}. In engineering applications, if quartz optical fibers experience physical fracture, they still need to be cleaved and arc-fused according to standard optical processes.