Frequency Synthesis Optical Frequency Domain Reflectometry
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Solution Overview
Problem
Current optical frequency domain reflectometers face limitations in spatial resolution and detection distance due to hardware complexity, high cost, and phase noise interference, with existing solutions like single-sideband modulators and radio frequency sweep signal sources offering limited improvements.
Innovation Solution
A frequency synthesis-based optical frequency domain reflectometry method using an electro-optic modulator and acousto-optic modulator to generate optical pulse signals with simultaneous frequency sweeping, breaking through limitations of modulator and RF source performances, achieving improved spatial resolution and detection distance without increasing hardware or software complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow optical pulse is used in OTDR technology to improve spatial resolution, then the spatial resolution increases, but the detection distance decreases due to limitations of laser device performance and optical fiber non-linear effects
Solution Approach 1:
The patent replaces the traditional mechanical/optical pulse narrowing approach with electro-optic modulation. By using an electro-optic modulator to generate frequency-swept optical signals, the system achieves high spatial resolution without requiring extremely narrow optical pulses, thereby maintaining long detection distance capability.
Solution Approach 2:
The patent changes the fundamental parameter from optical pulse width to frequency sweeping range. By sweeping the optical frequency over a wide range and processing the reflected signals in the frequency domain, the system achieves high spatial resolution through frequency discrimination rather than temporal pulse narrowing, resolving the contradiction between resolution and detection distance.
2Measurement precision
If a single-sideband modulator is used in OFDR technology to achieve high spatial resolution, then the frequency tuning range increases, but the device complexity and cost increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex single-sideband modulator from the system. Instead, it uses a simpler electro-optic modulator combined with frequency sweeping of the laser source to achieve the same frequency discrimination effect, thereby reducing device complexity and cost while maintaining high spatial resolution.
Solution Approach 2:
The patent creates a simplified version of the frequency sweeping mechanism. Rather than using a complex single-sideband modulator to generate frequency-swept signals, it employs a straightforward electro-optic modulator with frequency-swept laser input, achieving equivalent functionality with simpler components.
3Measurement precision
If a single-sideband modulator is used to expand frequency tuning range, then spatial resolution improves, but insertion loss increases and the modulator cannot completely suppress other sidebands
Solution Approach 1:
The patent substitutes the single-sideband modulator with an electro-optic modulator operating in a different mode. This replacement eliminates the sideband suppression problem and reduces insertion loss, as the electro-optic modulator can achieve clean frequency modulation without the complications of single-sideband generation.
4Length of stationary object
If an auxiliary interferometer is used for phase noise compensation to increase detection distance, then the detection distance extends, but the hardware complexity and data processing time increase significantly
Solution Approach 1:
The patent removes the auxiliary interferometer from the system architecture. By using frequency-swept optical signals and processing the reflected signals in the frequency domain, the system achieves long detection distance without requiring complex phase noise compensation hardware, thereby reducing hardware complexity while maintaining extended detection capability.
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
The method achieves enhanced spatial resolution and detection distance with lower insertion loss and stable performance, effectively suppressing phase noise and extending detection capabilities beyond coherence distance limitations.
Implementation Method 1
an electro-optic modulator performs modulation by a single frequency signal to generate an optical frequency comb signal
Implementation Method 2
an acousto-optic modulator performs frequency sweeping and pulse cutting on the optical frequency comb signal to obtain a multi-frequency sweep optical pulse signal
Implementation Method 3
Rayleigh backscattered light
Data Source
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AI summary
Frequency synthesis-based optical frequency domain reflectometry method and system are disclosed. The method is to implement optical frequency reflectometer and comprises: performing an electro-optic modulation (3) and an acousto-optic modulation (4) on a local light to obtain an optical pulse; inputting the optical pulse as a detection pulse optical signal (15) to a test optical fiber (9); and detecting an obtained Rayleigh backscattered optical signal (16) under coherent detection with the local light, and then performing a photoelectric conversion and a demodulation, wherein: the electro-optic modulation (3) is performed by using a single frequency signal (11); the acousto-optic modulation (4) is performed by using a pulse signal (12); and the optical pulse is obtained by simultaneously sweeping multiple frequency components of an optical comb signal which is obtained by the electro-optic modulation (3). The optical frequency domain reflectometry method and system have a large detection range, a high spatial resolution, a low hardware cost, and a low software complexity.