Optical Fiber Characteristic Measurement Using Modulated Brillouin Scattering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical-fiber-characteristic measuring methods using Brillouin scattering have limited spatial resolution and measurement time, making them inadequate for dynamically managed constructions, and struggle to separate the probe light signal from noise effectively, especially when increasing the measurement range while maintaining high spatial resolution.
Innovation Solution
The method involves modulating both the pump and probe lights with different intensity modulation frequencies, allowing for the separation of the probe light's change due to stimulated Brillouin scattering from the outgoing light using synchronous detection, eliminating the need for an optical wavelength filter and enabling a wider measurement range with maintained high spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical wavelength filter is used to separate the probe light from the pump light, then the probe light signal can be separated from noise, but the measurement range is limited and the device complexity increases
Solution Approach 1:
The patent changes the frequency parameter of the probe light and pump light by applying different intensity modulation frequencies to each. This frequency differentiation allows the probe light signal to be separated from the pump light noise through synchronous detection at the probe light's modulation frequency, eliminating the need for optical wavelength filters and extending the measurement range.
Solution Approach 2:
The patent replaces the optical wavelength filter (optical system) with an electronic synchronous detection system that uses frequency modulation and demodulation. This substitution allows for extended measurement range while maintaining signal separation capability through electronic rather than optical means.
2Area of stationary object
If the measurement range is extended by increasing the amplitude of frequency modulation, then the measurement range increases, but the spatial resolution deteriorates
Solution Approach 1:
The patent applies different intensity modulation frequencies to the probe light and pump light, creating a frequency difference that enables signal separation through synchronous detection. This parameter change allows the measurement range to be extended without increasing the frequency modulation amplitude, thereby maintaining high spatial resolution while achieving extended measurement range.
3Device complexity
If conventional time-resolving measurement method with light pulses is used, then the measurement setup is simple, but the measurement time is long and spatial resolution is limited
Solution Approach 1:
The patent employs periodic intensity modulation of the probe light and pump light at different frequencies. This periodic action enables continuous wave measurement instead of pulsed measurement, significantly reducing measurement time while maintaining spatial resolution through synchronous detection of the modulated signals.
Solution Approach 2:
The patent replaces the pulsed light measurement method with a continuous wave method using intensity modulation and synchronous detection. This substitution eliminates the need for time-gating and reduces measurement time from several minutes to much shorter durations while improving spatial resolution.
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 separates the probe light signal from noise, extending the measurement range while maintaining high spatial resolution, and reduces measurement time and signal accuracy deterioration, providing a more efficient and accurate method for strain detection in optical fibers.
Implementation Method 1
a light source unit which outputs an oscillation light undergone frequency modulation
Implementation Method 2
performing modulations on both probe light and pump light
Implementation Method 3
separating only a change in the probe light originating from stimulated Brillouin scattering from an outgoing light from the measurement-target optical fiber
Implementation Method 4
separating only a change in the probe light originating from stimulated Brillouin scattering from an outgoing light from the measurement-target optical fiber, using the two modulations performed by the modulation means
Data Source
AI summary
A measurement range is extended while maintaining the spatial resolution high by completely separating the increment of a probe light from noises. Modulations are performed on both probe light and pump light to differentiate both lights. Using the modulations, only the change in the probe light necessary for measuring the characteristic of a measurement-target optical fiber FUT can be separated. Accordingly, unlike the conventional technology, an optical wavelength filter becomes unnecessary. Further, in a case where an amplitude Δf of the frequency modulation of a light source 1 is made wide to some extent to make the measurement range wide while maintaining a spatial resolution Δz high, the amplitude Δf does not affect to detection of the change in the probe light. Therefore, the increment of the probe light can be completely separated from noises, thereby extending the measurement range while maintaining the spatial resolution Δz high.