How does the bending radius under tension differ from the static bending radius during installation?
The bending radius of an optical fiber is a critical parameter, and its behavior differs significantly between static conditions and conditions under tension.
-
Static Bending Radius (during installation): This refers to the minimum radius an optical fiber can be bent without inducing significant optical loss or physical damage when the fiber is not under any substantial external tensile load. It is primarily determined by the fiber’s material properties, core/cladding diameter, and coating. Exceeding this limit can lead to increased macro-bending losses and potential long-term reliability issues due to accumulated stress.
-
Bending Radius Under Tension: When an optical fiber is subjected to tensile stress, its mechanical properties are altered. Bending the fiber while it is under tension introduces additional, often concentrated, strain on the fiber’s structure. This combined stress state (tension + bending) significantly reduces the fiber’s tolerance to bending. Consequently, the minimum permissible bending radius for a fiber under tension will be larger (meaning a less severe bend) than its static bending radius to prevent micro-fractures, catastrophic failure, or increased optical attenuation. The pre-existing tensile strain makes the fiber more susceptible to the additional strain from bending.
For OFSCN® Fiber Bragg Gratings (FBG), maintaining the appropriate bending radius is crucial to ensure the FBG’s spectral integrity (central wavelength, reflectivity, bandwidth) and measurement accuracy are not compromised by bend-induced stress. This is especially important for bare FBGs or when sensors are installed in applications involving dynamic loading or pre-tension.
An example of an FBG sensor is shown below:
You can find more technical specifications on our international website.
1 Like