Can signals from sensors with adjacent wavelengths interfere with each other?
Yes, signals from fiber Bragg grating (FBG) sensors with adjacent wavelengths can indeed interfere with each other, a phenomenon often referred to as crosstalk.
This occurs if the Bragg wavelengths of closely spaced sensors are too near, or if the spectral width (3dB bandwidth) of the individual FBGs is too broad. In such cases, their reflected spectral peaks can overlap. When an interrogator attempts to read these signals, it may struggle to accurately distinguish between the overlapping peaks, leading to errors in the demodulated strain or temperature readings.
To mitigate this, proper FBG system design involves:
- Sufficient Wavelength Spacing: Allocating enough spectral separation between adjacent FBGs to prevent their reflection peaks from overlapping.
- Appropriate Bandwidth: Ensuring that the FBGs have a narrow enough 3dB bandwidth for the application, which is influenced by parameters like the grating length and reflectivity.
OFSCN® FBG products, such as the OFSCN® Alloy Tube Packaged Fiber Bragg Grating strain sensor, offer customizable grating lengths and wavelength ranges (e.g., 1510 nm to 1590 nm) to allow for precise system design that minimizes crosstalk.
Here is a standard image illustrating a fiber Bragg grating structure:
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