Will extreme water pressure crush the grating? How should it be packaged?
Extreme water pressure can indeed affect the grating if it’s not adequately protected. Unpackaged Fiber Bragg Gratings (FBGs) are sensitive to both axial strain and temperature. In a high-pressure environment like the deep sea, the pressure can induce strain on the bare fiber, causing a shift in the Bragg wavelength, which can be misinterpreted as a measurement or lead to damage.
To prevent the grating from being crushed and to ensure accurate measurements, specialized packaging is essential. The most effective method for deep-sea high-pressure applications is to encase the FBG within a robust, pressure-resistant material, such as a seamless metal tube. This type of packaging isolates the FBG from direct external pressure, protecting the grating and allowing it to measure the intended parameter (e.g., strain or temperature) without interference from hydrostatic pressure.
For applications requiring protection against high pressure, we recommend solutions that utilize alloy tube packaging. For example, the OFSCN® Alloy Tube Packaged Fiber Bragg Grating strain sensor employs this type of robust metallic encapsulation. While primarily a strain sensor, its packaging demonstrates the necessary protective measures against external pressures.
Here are some standard images illustrating such packaging:
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