Non-linear Frequency Scan Optical Fiber Reflectometry
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Solution Overview
Problem
Existing fiber-optic reflectometry techniques face challenges in generating optical signals with instantaneous frequencies that vary linearly with time, particularly in dynamic sensing applications requiring high bandwidth and fast scan repetition rates, making it difficult to derive spatial information effectively.
Innovation Solution
The use of a non-linearly-scanning optical interrogation signal, such as a sinusoidally-scanning signal, whose instantaneous optical frequency is a non-linear function of time, is implemented, allowing for improved analysis of the beat signal using a predefined function that compensates for the effects of non-linear scanning, enabling effective sensing of events in optical fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linearly-scanning optical interrogation signal is used, then spatial information can be derived effectively, but it is difficult to generate signals with high bandwidth and fast scan repetition rates
Solution Approach 1:
The patent changes the scanning law parameter from linear to non-linear (sinusoidal) frequency scanning. This parameter change allows the system to achieve both high bandwidth and fast scan repetition rates while maintaining the ability to derive spatial information through appropriate signal processing with predefined functions.
2Productivity
If non-linear frequency scanning is used, then high bandwidth and fast scan repetition rates are achieved, but the beat signal analysis becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing predefined functions that correspond to the non-linear scanning law before the actual measurement. These predefined functions are used during signal processing to simplify the analysis of the beat signal, converting a complex non-linear analysis problem into a more manageable form through pre-computation.
3Productivity
If non-linear frequency scanning is used, then high bandwidth and fast scan repetition rates are achieved, but the beat signal phase varies non-linearly making spatial derivation difficult
Solution Approach 1:
The patent implements feedback by using the known non-linear scanning law to generate predefined functions that compensate for the non-linear phase variation in the beat signal. The signal processing uses these predefined functions to correct the non-linear phase effects, enabling accurate spatial information derivation despite the non-linear scanning approach.
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 accurate estimation of the backscattering profile and detection of events in optical fibers, maintaining performance measures like resolution and update rate, and can be applied in various sensing applications including optical network monitoring and perimeter security.
Implementation Method 1
generate a non-linearly-scanning optical interrogation signal having an instantaneous optical frequency that is a non-linear function of time
Implementation Method 2
mix the optical backscattering signal with a reference replica of the optical interrogation signal, so as to produce a beat signal
Data Source
AI summary
A system (20) for fiber-optic reflectometry includes an optical source (28, 40), a beat detection module (44, 48, 52, 56A, 56B) and a processor (36). The optical source is configured to generate a non-linearly-scanning optical interrogation signal having an instantaneous optical frequency that is a non-linear function of time. The beat detection module is configured to transmit the optical interrogation signal into an optical fiber (24), to receive from the optical fiber an optical backscattering signal in response to the optical interrogation signal, and to mix the optical backscattering signal with a reference replica of the optical interrogation signal, so as to produce a beat signal. The processor is configured (i) to hold a predefined function that is indicative of an expected phase of the beat signal resulting from the non-linearly-scanning optical interrogation signal as a function of position along the optical fiber and time, (ii) to estimate a backscattering profile of the optical fiber by applying the predefined function to the beat signal, and (iii) to sense one or more events affecting the optical fiber by analyzing the backscattering profile.