If a patch cord is submerged or used in a humid environment, will the internal glass core deteriorate or “rot”?
The internal glass core of a fiber optic patch cord does not “rot” in the biological sense, but it is indeed sensitive to water and humidity over long periods due to a process known as hydroxyl (OH-) ion absorption and stress corrosion.
1. Attenuation Increase (Hydroxyl Absorption)
If water molecules penetrate the protective coatings and reach the glass core, they can bond with the silica. This creates hydroxyl ions, which cause specific “water peaks” in the absorption spectrum (notably around the 1383nm wavelength). This significantly increases the attenuation (signal loss), potentially making the fiber unusable for long-distance transmission.
2. Stress Corrosion and Micro-cracks
Glass fiber is highly sensitive to the combination of moisture and mechanical stress. Under humid conditions, water molecules act as a catalyst that accelerates the growth of sub-microscopic cracks on the surface of the glass. Over time, this leads to a decrease in the fiber’s tensile strength, making it brittle and prone to breaking unexpectedly.
3. Coating Degradation
Standard fiber optic patch cords are typically designed for indoor environments. Their protective jackets (often PVC or LSZH) and internal coatings are not hermetically sealed. In submerged or high-humidity environments:
- The buffer and jacket may swell or degrade.
- Water can “wick” along the length of the cable via the aramid yarns (Kevlar) inside the jacket.
Engineering Solutions from OFSCN®
For applications where water or high humidity is a factor, standard indoor patch cords should be replaced with sensors or cables featuring specialized hermetic or waterproof packaging.
For example, our OFSCN® Capillary Seamless Stainless Steel Tube FBG Sensors utilize a seamless steel tube to provide a physical barrier against moisture.
Standard Product Image:
OFSCN® Capillary Seamless Stainless Steel Tube Fiber Bragg Grating Sensor
Recommended Product for Harsh Environments:
OFSCN® Capillary Seamless Stainless Steel Tube FBG Temperature Sensor
Key Advantages:
- Hermetic Protection: The seamless stainless steel tube prevents water molecules from reaching the fiber core.
- Corrosion Resistance: Designed for harsh environments where standard patch cords would fail.
If your project involves specific environmental conditions (such as deep-water submersion or chemical exposure), please feel free to provide more details about the deployment environment.