Optical Modulator Demodulator Spatial Temperature Resolution
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Solution Overview
Problem
Current spatially resolved temperature measurement systems using optical fibers face limitations in achieving high spatial resolution, with known technologies typically providing resolutions of around 0.5 meters or worse, which is insufficient for many industrial and environmental applications requiring resolutions of 0.1 meters or better.
Innovation Solution
The use of optical techniques for demodulation and modulation in Distributed Temperature Sensing (DTS) devices, including the employment of high-frequency optical modulators and demodulators, such as Mach-Zehnder modulators, to achieve frequencies in the GHz range, enabling spatial resolutions of 0.1 meters or better by modulating the laser light with direct current and using photodiodes for detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electrical modulation and demodulation techniques are used in DTS devices, then the device can operate with conventional electronics, but the spatial resolution is limited to around 0.5 meters due to frequency limitations
Solution Approach 1:
The patent replaces electrical modulation and demodulation systems with optical modulation and demodulation systems. Specifically, it uses optical modulators to modulate the laser light and optical demodulators (such as photodiodes with direct current coupling) to detect the modulated light. This substitution of electrical systems with optical systems enables operation at frequencies in the GHz range, achieving spatial resolutions of 0.1 meters or better, while maintaining ease of manufacture through the use of standard optical components.
2Manufacturing precision
If higher modulation frequencies are used to improve spatial resolution, then spatial resolution improves, but the required modulation currents become very high (approx. 1A) and inductances limit the achievable frequencies
Solution Approach 1:
The patent substitutes electrical modulation with optical modulation, where the laser light itself is modulated at high frequencies without requiring high electrical currents. The optical modulator directly modulates the light intensity or phase at GHz frequencies without being constrained by electrical inductances or requiring large modulation currents, thus achieving high spatial resolution with manageable power requirements.
Solution Approach 2:
The patent changes the modulation parameter from electrical current modulation to optical intensity or phase modulation. By modulating the optical properties of the laser light directly rather than varying electrical currents, the system achieves high-frequency operation (GHz range) without the limitations of electrical inductances and without requiring high modulation currents of approximately 1A.
3Ease of operation
If electrical demodulation with transimpedance amplifiers is used, then detection can be achieved, but frequencies above 250 MHz are difficult to realize due to direct current coupling requirements
Solution Approach 1:
The patent replaces electrical demodulation using transimpedance amplifiers with optical demodulation using photodiodes with direct current coupling. The photodiodes directly convert the optical modulation signals to electrical signals without requiring high-gain amplifiers, enabling operation at frequencies in the GHz range. This substitution removes the frequency limitation of 250 MHz that exists in electrical demodulation systems due to direct current coupling requirements and amplifier bandwidth limitations.
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 allows for significantly improved spatial resolution in temperature measurement along optical fibers, enabling precise monitoring in applications like industrial and environmental monitoring, surpassing the limitations of existing technologies.
Implementation Method 1
optical modulator means for modulating the light from the laser light source with a frequency in a range allowing for spatial resolutions of 0.1 meters or better
Implementation Method 2
sensor means for detecting the portions of the modulated light
Implementation Method 3
demodulator means comprising sensor means and means for generating an additional light signal which can be detected by the sensor means together with the portions of the light
Data Source
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AI summary
Apparatus for spatially resolved temperature measurement, comprising at least one optical fibre (4) for spatially resolved temperature measurement, at least one laser light source (1), the light (11) from which can be coupled into the optical fibre (4), wherein those components (12, 12a, 12b) of the light (11) produced by the laser light source (1) which are scattered back in the optical fibre (4) can be coupled out of the optical fibre (4) and detected, modulator means (2) permitting the modulation of the light (11) that is to be coupled into the optical fibre (4), and also demodulator means (5, 6) which permit a demodulation of those components (12, 12a, 12b) of the light (11) which are coupled out of the optical fibre (4), wherein the demodulator means (5, 6) are designed as optical demodulator means (5, 6) and/or wherein the modulator means (2) are designed as optical modulator means (2).