What is FBG Multiplexing Capability?

[frostweaver]

Why can dozens of sensors be connected in series on a single fiber? How is Wavelength Division Multiplexing (WDM) implemented?

[ofscn_presale_en]

Multiple Fiber Bragg Grating (FBG) sensors can be connected in series on a single fiber through a technique called Wavelength Division Multiplexing (WDM). This capability is one of the significant advantages of FBG sensing technology.

Here’s how WDM is implemented:

1. Wavelength Specificity: Each FBG in the series is designed to reflect a specific, unique wavelength or a narrow wavelength band, while allowing other wavelengths to pass through. These assigned wavelengths are non-overlapping.
2. Broadband Light Source: A broadband light source injects light covering a wide spectrum into the optical fiber.
3. Selective Reflection: As the broadband light travels along the fiber, each FBG it encounters reflects its pre-assigned wavelength back towards the source, while the remaining wavelengths continue to propagate past that FBG.
4. Interrogator Detection: An OFSCN® Fiber Bragg Grating Interrogator (demodulator) is connected to the fiber. It detects and analyzes the distinct reflected wavelengths from each FBG.
5. Parameter Measurement: When an FBG is subjected to changes in physical parameters like temperature or strain, its reflected wavelength shifts (Bragg wavelength shift). The interrogator precisely measures these shifts, thereby determining the change in the sensed parameter at each FBG location.

This method allows a single optical fiber to host multiple sensing points, with each point monitored independently by its unique reflected wavelength. The number of sensors that can be connected in series is primarily limited by the total available wavelength spectrum of the interrogator and the wavelength bandwidth required for each sensor.

The OFSCN® Fiber Bragg Grating Interrogator is a key component for implementing WDM, offering various channel configurations to support multiple sensors.

Here is a standard picture of our interrogator:

You can find more details about our interrogators here:
OFSCN® Fiber Bragg Grating Interrogator