FBG Sensor Array Using Raman Amplification for Extended Distance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional fiber optic sensor systems, particularly those using WDM and TDM based on FBG arrays, face limitations in accommodating large numbers of sensing points over extended distances, with WDM systems constrained by wavelength range and TDM systems struggling with accurate reconstruction of high-frequency pulse responses.
Innovation Solution
A TDM- and WDM-based FBG sensor array system that employs Raman amplification to enhance signal quality, allowing for the use of multiple wavelength-defined groups of gratings, enabling the system to handle tens of thousands or hundreds of thousands of sensing points by improving signal-to-noise ratio and reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If WDM-based sensor system is used to accommodate multiple sensing points, then the number of sensing points can be increased within wavelength range, but the system becomes incapable of providing large numbers of sensing points (thousands over 10 km) due to wavelength range constraints
Solution Approach 1:
The patent segments the sensing system into multiple wavelength-defined groups of FBGs. Each group operates at a distinct wavelength, allowing the total number of sensing points to exceed the capacity of a single wavelength range by dividing the sensing array into manageable segments across multiple wavelengths.
Solution Approach 2:
The patent transitions from single-dimensional WDM to multi-dimensional multiplexing by combining WDM (wavelength dimension) with TDM (time dimension). This allows sensing points to be organized in groups across wavelengths, with each group further multiplexed in time, dramatically expanding the total number of accessible sensing points beyond what single-wavelength systems can provide.
2Quantity of substance
If TDM-based sensor system is used to increase sensing points beyond wavelength limits, then the number of sensing points can be increased, but the output processing stage must robustly and accurately reconstruct high-frequency pulse responses (10^8 Hz or faster) which becomes problematic
Solution Approach 1:
The patent segments the high-frequency TDM signal reconstruction task into manageable frequency bands using optical filtering. By dividing the broad wavelength range into multiple narrower bands, each processed separately, the system can accurately reconstruct pulse responses without being overwhelmed by the full 10^8 Hz spectrum, maintaining measurement precision while supporting thousands of sensing points.
Solution Approach 2:
The patent combines TDM with WDM to create a two-dimensional multiplexing scheme. This allows the system to distribute sensing points across both wavelength and time dimensions, reducing the temporal sampling rate requirements compared to pure TDM while still accommodating thousands of sensing points. The wavelength dimension provides an additional degree of freedom that eases the burden on pulse response reconstruction.
3Ease of manufacture
If conventional WDM system is used, then implementation is straightforward and easy, but the system cannot accommodate thousands of sensing points over extended distances due to wavelength range constraints
Solution Approach 1:
The patent maintains implementation simplicity by segmenting the FBG array into wavelength groups, where each group can be processed using conventional WDM techniques. This segmentation approach allows the system to scale to thousands of sensing points while retaining the ease of manufacture and implementation characteristics of conventional WDM systems, as each wavelength group can be independently managed.
Solution Approach 2:
The patent merges conventional WDM and TDM approaches into a hybrid system. This combination leverages the implementation simplicity and established technology of WDM while incorporating TDM's ability to expand sensing point capacity beyond wavelength limits. The merged system achieves both ease of manufacture and the capability to accommodate thousands of sensing points over extended distances.
Data Source
AI summary
In a TDM- and WDM-based FBG sensor array system, a source emits a light covering a selected wavelength range. The light is amplified and then used to generate a series of pulses that are fed into an array of sensor gratings. The propagation of a pulse through the sensor array results in a time-domain-multiplexed output, comprising a series of output pulses in which each output pulse comprises a reflection of the input pulse at a respective grating in the sensor array. Raman amplification is used to amplify both the pulse input into and the time-domain multiplexed output from the sensor array, which is then coupled into an output processing stage for receiving the sensor output and for reconstructing the wavelength output of each grating in the sensor array. The wavelength change for each grating is then used to calculate a physical parameter(s) to be measured, such as temperature and/or strain.