Optical Fiber Path Testing with Two-Stage Modulation
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Solution Overview
Problem
Existing optical path testing methods face challenges in accurately measuring both physical vibration and loss of an optical fiber using the same light source due to differing requirements for phase noise reduction and fading noise suppression.
Innovation Solution
An optical path testing device and method that divides output light into a probe and local optical path, performs multiple frequency modulations, and generates a beat signal to analyze backscattered light, allowing for simultaneous measurement of fiber loss and vibration using a single light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the line width of the light source is narrowed to reduce phase noise for vibration measurement, then measurement accuracy of vibration is improved, but the frequency variation width becomes insufficient for suppressing fading noise in loss measurement
Solution Approach 1:
The patent segments the measurement process into two distinct modulation stages: first modulation applies multiple frequencies within a single pulse duration for vibration measurement, while second modulation applies frequency shifts across different pulse periods for loss measurement. This segmentation allows each modulation stage to be optimized for its specific measurement type, resolving the contradiction between narrow line width requirements for vibration measurement and wide frequency variation requirements for loss measurement.
Solution Approach 2:
The patent dynamically adjusts the frequency characteristics of the light source through two-stage modulation. The first modulation dynamically changes frequency within pulse duration based on vibration detection needs, while the second modulation dynamically shifts frequency across pulse periods for loss measurement. This dynamic frequency control allows the system to adapt to different measurement requirements without being constrained by a fixed light source line width.
2Measurement precision
If frequency is changed to suppress fading noise for loss measurement, then measurement accuracy of loss is improved, but measurement time increases due to multiple frequency measurements
Solution Approach 1:
The patent employs periodic frequency modulation where the second modulation applies frequency shifts at regular pulse periods. This periodic action allows the system to efficiently sweep through multiple frequencies for fading noise suppression while maintaining a structured measurement rhythm that optimizes measurement time. The periodic nature of the modulation enables systematic data collection across frequency bands without unnecessary delays.
Solution Approach 2:
The patent changes the frequency parameter of the light source through two-stage modulation to simultaneously address vibration and loss measurements. By modifying frequency characteristics in a controlled manner through parameter changes, the system achieves fading noise suppression for loss measurement while the integrated modulation approach maintains measurement efficiency, reducing the time penalty associated with multi-frequency measurements.
3Measurement precision
If FSAV is used to suppress fading noise and improve loss measurement accuracy, then measurement accuracy of loss is improved, but the effect is insufficient without additional frequency variation
Solution Approach 1:
The patent combines two modulation techniques (first modulation with multiple frequencies and second modulation with frequency shifts) into a composite modulation approach. This composite method integrates the fading noise suppression capability of FSAV with additional frequency variation, creating a synergistic effect that enhances loss measurement accuracy while maintaining measurement efficiency through the coordinated action of both modulation stages.
Solution Approach 2:
The two-stage modulation system serves multiple functions: the first modulation handles vibration measurement while the second modulation enables loss measurement with fading noise suppression. This multi-functional approach allows a single measurement system to perform both vibration and loss measurements effectively, improving productivity by eliminating the need for separate measurement systems or additional frequency variation techniques.
4Device complexity
If a single light source is used for both vibration and loss measurement, then device complexity is reduced, but measurement accuracy for both parameters cannot be simultaneously optimized
Solution Approach 1:
The patent makes a single light source universal by implementing two-stage modulation that enables both vibration and loss measurements with optimized accuracy. The first modulation stage optimizes the light source for vibration detection, while the second modulation stage optimizes it for loss measurement with fading noise suppression. This multi-functional modulation approach allows one light source to perform multiple measurement functions with high precision, eliminating the need for multiple specialized light sources.
Solution Approach 2:
The patent changes the operational parameters of the single light source through two-stage modulation to adapt it for different measurement types. By dynamically adjusting frequency characteristics through parameter changes, the same light source can be optimized for vibration measurement (narrow effective line width) and loss measurement (wide frequency variation) sequentially, achieving simultaneous measurement accuracy without requiring multiple light sources with different characteristics.
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
Enables accurate measurement of both optical fiber loss and vibration by suppressing fading noise and phase noise, improving measurement speed and accuracy with reduced calculation load.
Implementation Method 1
output light from a laser light source
Implementation Method 2
perform first modulation in which a plurality of modulations based on at least two or more different first frequencies is sequentially performed and second modulation in which modulation is performed based on a second frequency
Implementation Method 3
acquire a signal indicating backscattered light in the optical fiber
Implementation Method 4
generate a beat signal by causing signal light emitted from one end of an optical fiber when the probe light enters into the one end and input light of the local optical path to interfere with each other
Implementation Method 5
measuring physical vibration around a measurement target optical fiber by detecting a change in phase caused by a minute change in an optical fiber length due to vibration
Data Source
AI summary
An optical path testing device and an optical path testing method divide output light from a laser light source into a probe optical path and a local optical path and convert modulated light obtained by modulating input light of the probe optical path into probe light including pulsed light, generate a beat signal by causing signal light and input light of the local optical path to interfere with each other, acquire a signal indicating backscattered light in the optical fiber on the basis of the beat signal, and analyzes a loss distribution, when generating the modulated light, perform first modulation and second modulation, and generate an analysis signal by averaging the backscattered light in each different frequency band included in the beat signal between the different frequency bands and acquire the loss distribution by analyzing an intensity of the backscattered light included in the analysis signal.