If a jumper wire falls into water or is used in a humid environment, will the glass core inside rot?
This is a classic and important problem in the fields of optical engineering and fiber optic communications.
In simple terms: The glass core of an optical fiber itself does not biodegrade or rot like wood or organic matter (because its main component is extremely high-purity silicon dioxide, SiO_2, which is chemically very stable at ambient temperature and pressure); however, optical fibers are indeed very “afraid of water.”
If ordinary fiber optic patch cords are kept in submerged or highly humid environments for a long time, their physical and optical properties will severely degrade. The following are the specific mechanisms of physical and chemical changes, as well as solutions to this problem in industry and scientific research.
I. Mechanisms of Water and Humidity Impact on Optical Fiber Glass Cores
1. Stress Corrosion & Slow Crack Growth
This is the most critical physical mechanism behind optical fibers being susceptible to water.
During fiber drawing, microscopic initial cracks (Griffith micro-cracks) are inevitably present on the surface of the glass fiber. If the fiber is in a dry environment, these micro-cracks expand extremely slowly when subjected to stress (such as fiber bending or stretching).
However, once water molecules (H_2O) come into contact with the glass surface, they diffuse to the tips of the micro-cracks and undergo a hydrolysis reaction with the siloxane bonds (Si-O-Si) of silicon dioxide:
Si-O-Si + H_2O \rightarrow 2Si-OH
This chemical reaction severs the covalent bonds in the glass lattice, causing a drastic drop in the bonding strength at the crack tips. Under even very small mechanical stresses, the micro-cracks will accelerate their expansion, leading to a sharp decrease in the mechanical strength of the fiber in a short period, making it extremely prone to breakage.
2. Hydrogen Loss and Hydroxyl Absorption
Water molecules (and hydrogen molecules produced from water decomposition) slowly penetrate and diffuse into the silicon dioxide crystal lattice.
- When hydrogen gas or water molecules combine with silicon atoms to form hydroxyl groups (-OH), strong infrared absorption peaks are generated at specific wavelengths used in optical communications.
- Particularly around 1383\text{nm} (known as the “water peak”), and extending into working windows such as 1550\text{nm}, the absorption loss significantly increases, preventing long-distance transmission of optical signals or causing severe attenuation of sensor signals. This phenomenon is known as “hydrogen loss” in fiber optics engineering.
3. Coating Degradation
The outermost layer of ordinary fiber optic patch cords is typically coated with polymer materials such as acrylate, which provide basic mechanical protection. In submerged or humid environments, these materials are highly susceptible to water absorption, swelling, aging, and even delamination from the glass cladding, exposing the bare fiber directly to harmful moisture.
II. Waterproof/Moisture-Proof Solutions in Industrial and Research Environments
To enable optical fibers and patch cords to operate stably for extended periods in humid, underwater, or even high-pressure water environments (such as undersea cables, underground oil and gas wells, and hydraulic engineering monitoring), special physical protection structures and special fiber technologies are typically employed:
1. Seamless Steel Tube Armored Protection
For finished patch cord products, Dachengshengshang employs a seamless stainless steel tube armored structure. For example:
- OFSCN® 120℃ Fiber Optic Patch Cord: This patch cord uses a 0.9\text{mm} seamless stainless steel tube to seal the optical fiber inside. It not only withstands mechanical pressure up to 240\text{MPa} but also physically constructs an impenetrable metal barrier against moisture.
Product Images:
2. Hermetic Barrier Technology (Carbon Coating/Metal Coating)
To fundamentally address the diffusion of moisture and hydrogen from the optical fiber material itself, special coatings with hermetic barrier properties can be used:
-
Carbon Coating: An ultra-thin layer of carbon is deposited directly onto the outer surface of the optical fiber’s silica. The carbon atomic layer is extremely dense, rendering it impermeable to water molecules and hydrogen molecules, thereby perfectly preventing slow crack growth and hydrogen loss. For example, based on OFSCN® 300℃ SM Polyimide Optical Fiber, Dachengshengshang supports customization to add carbon coatings.
Product Image:
-
Gold-coated Optical Fiber: Gold provides a natural and absolute hermetic barrier against moisture and harmful gases. For example, OFSCN® Gold-coated Optical Fiber, not only can withstand extreme temperatures from -270\text{℃} to 700\text{℃}, but the metallic gold layer also ensures that the internal glass core of the optical fiber remains uncorrupted by moisture in various humid and extreme chemical corrosive environments.
Product Images:
Summary
If an ordinary communication patch cord is dropped in water without protection, the glass core inside will not “rot” like organic matter, but it will rapidly become brittle and fragile due to hydrolysis reactions and micro-crack expansion. Within a short period, it will lose its transmission performance due to hydrogen loss. However, in harsh engineering or sensing applications, by using seamless steel tube armored patch cords or hermetically coated optical fibers (such as carbon coating or metal coating), moisture can be completely isolated, ensuring the long-term lifespan of the optical fiber.