FBG Demodulation Device Stabilizing Wavelength Scanning via Interferometer
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Solution Overview
Problem
Fiber Bragg Grating (FBG) demodulation systems face accuracy issues due to fluctuations in the wavelength-scanning nonlinear curve caused by rapid temperature changes, particularly in tunable F-P filter systems, which affect the precision of measurements in variable temperature environments.
Innovation Solution
The introduction of an optical fiber assisted interferometer subdivides the optical frequency between adjacent interference spectral lines of an F-P etalon, providing additional local optical frequency references to calibrate the wavelength-scanning nonlinear curve of the tunable filter, thereby stabilizing the demodulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a tunable F-P filter is used for FBG demodulation, then high-speed and high-accuracy demodulation in a wide spectral range is achieved, but the hysteresis, creep, and nonlinearity of the PZT cause poor linearity and repeatability between transmission wavelength and driving voltage, reducing demodulation accuracy
Solution Approach 1:
The patent introduces an F-P etalon as an intermediary component to provide reference wavelengths at uniform intervals across the spectral range. This etalon acts as a mediator between the broadband light source and the detection system, enabling calibration of the nonlinear wavelength-scanning curve of the tunable F-P filter. The reference wavelengths from the etalon serve as fixed reference points that correct for PZT nonlinearity, hysteresis, and creep effects, thereby improving demodulation accuracy while maintaining high-speed operation.
Solution Approach 2:
The patent changes the parameter of using fixed reference wavelengths from the F-P etalon to calibrate the varying transmission wavelengths from the tunable filter. By establishing a mapping relationship between the etalon's stable reference wavelengths and the filter's scanning wavelengths, the system compensates for PZT parameter variations (hysteresis, creep, nonlinearity) and achieves accurate wavelength demodulation throughout the scanning range.
2Measurement precision
If an F-P etalon is used to calibrate the wavelength-scanning nonlinear curve, then absolute wavelength demodulation at different stable temperatures is achieved, but when ambient temperature changes rapidly, the PZT increases random fluctuation of the wavelength-scanning nonlinear curve, causing large fluctuation in demodulation results
Solution Approach 1:
The patent implements a feedback mechanism where the F-P etalon provides continuous reference wavelengths that feedback to the demodulation system. During rapid temperature changes, these reference wavelengths serve as a stable reference frame, allowing the system to detect and correct deviations in the tunable filter's scanning curve caused by PZT fluctuations. The feedback from the etalon's stable spectral lines enables real-time compensation for temperature-induced nonlinearities and maintains demodulation stability.
Solution Approach 2:
The patent prepares beforehand by introducing the F-P etalon as a pre-established reference system with stable, temperature-insensitive wavelengths. This reference system is in place before temperature changes occur, providing a cushioning effect that protects the demodulation accuracy from rapid temperature variations. The etalon's reference wavelengths act as a buffer against PZT fluctuations, ensuring continuous accurate measurement even during rapid environmental changes.
3Measurement precision
If the optical fiber assisted interferometer is introduced to subdivide optical frequency intervals, then additional local optical frequency references are obtained, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the broad spectral range into smaller segments using the optical fiber assisted interferometer. The interferometer subdivides the optical frequency intervals between F-P etalon transmission peaks, creating multiple local reference points within each spectral segment. This segmentation provides higher precision local frequency references while keeping each segment manageable, balancing improved measurement precision with controlled system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses large fluctuations in wavelength demodulation, significantly improving the stability and accuracy of FBG sensor measurements, even under rapid temperature changes, as demonstrated by a 5.9-fold reduction in wavelength demodulation fluctuation from ±24 pm to ±3.5 pm.
Implementation Method 1
an optical fiber assisted interferometer 13 consisting of a second optical fiber isolator 42, an optical fiber coupler 14, Faraday polarizers 15 and a second photoelectric detector array 162... subdivides the optical frequency between adjacent interference spectral lines of an F-P etalon
Implementation Method 2
An F-P etalon can introduce, within a range matched with the light source band, a plurality of optical frequency reference points at uniform intervals
Implementation Method 3
light emitted from the broadband light source 1 is processed by the optical attenuator 2... enters the tunable F-P filter 3... enters the erbium-doped optical fiber amplifier 5 for optical power amplification
Implementation Method 4
Faraday polarizers 15... reflected light from two interference arms are reflected by the Faraday polarizers 15 and then form interference fringes
Data Source
AI summary
The present invention discloses a Fiber Bragg Grating demodulation device with a suppressed fluctuation at a variable ambient temperature and a demodulation method. The device comprises a broadband light source (1), an optical attenuator (2), a tunable F-P filter (3), a first optical fiber isolator (41), an erbium-doped optical fiber amplifier (5), an optical fiber first-stage beam splitter (6), a first optical fiber second-stage beam splitter (71), optical fiber circulators (8), FBG sensor arrays (9), a first photoelectric detector array (161), an optical fiber gas cell (10), a second optical fiber second-stage beam splitter (72), an optical fiber F-P etalon (11), a notch filter (12), an optical fiber assisted interferometer (13), a data acquisition card (17) and a processor (18).