Broadband Optical Sensor Multiplexing via Wavelength-Time Conversion
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Solution Overview
Problem
Current code division multiplexing (CDM) sensor systems face limitations in the number of sensors that can be measured and have a low response rate due to the need for variable lasers and synchronization delays, as well as challenges in measuring wavelength deviations.
Innovation Solution
A broadband optical source is used for high-speed modulation, with pseudorandom number generators and a wavelength-time converter to convert wavelength variations into time shifts, allowing for simultaneous monitoring of multiple sensors without delay through autocorrelation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable laser is used to increase the operation range in CDM sensor system, then the measurement range is improved, but the scanning time increases and synchronization delay occurs
Solution Approach 1:
The patent changes the fundamental parameter of the light source from a variable wavelength laser to a broadband light source with fixed wavelength. This parameter change enables simultaneous measurement of multiple sensors across different wavelengths without requiring wavelength tuning, thereby eliminating scanning time and synchronization delays while maintaining extended measurement range through the broadband spectrum coverage.
2Productivity
If the center wavelength of a sensor is changed by an external factor, then the sensor responds to environmental changes, but the center wavelength may overlap with neighboring sensors causing measurement interference
Solution Approach 1:
The patent transitions from wavelength-domain multiplexing (WDM) where wavelength overlap causes interference to time-domain multiplexing using autocorrelation. By converting the wavelength spectrum into a time-domain autocorrelation function, sensors with overlapping center wavelengths can be distinguished through their unique temporal correlation signatures, thereby resolving the measurement interference problem while maintaining environmental sensitivity.
3Quantity of substance
If TDM method uses sensors having the same center wavelength, then the number of sensors is increased, but the signal processor design becomes complicated and response rate decreases
Solution Approach 1:
The patent uses autocorrelation of the pseudorandom code to create a unique temporal fingerprint for each sensor without requiring complex signal processing. The system copies the same broadband light source and pseudorandom code to all sensors, but the optical path differences create distinct autocorrelation patterns that can be easily distinguished, simplifying the signal processor while enabling multiple sensor measurement.
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 increases the number of measurable sensors and enhances scanning rates, enabling real-time monitoring of multiple sensors with improved measurement range and reduced crosstalk.
Implementation Method 1
a first pseudorandom number generator generating a first pseudorandom number code string to modulate the broadband optical source
Implementation Method 2
at least one sensor reflecting an output of the first pseudorandom number generator at a wavelength corresponding to a center wavelength thereof
Implementation Method 3
a wavelength-time converter converting an output of the sensor by wavelength-time conversion
Implementation Method 4
a mixer mixing an output signal of the wavelength-time converter with an output signal of the second pseudorandom number generator
Implementation Method 5
an integrator integrating an output of the mixer
Data Source
AI summary
A sensing apparatus includes: a broadband optical source; a first pseudorandom number generator generating a first pseudorandom number code string to modulate the broadband optical source; at least one sensor reflecting an output of the first pseudorandom number generator at a wavelength corresponding to a center wavelength thereof when the output of the first pseudorandom number generator is inputted; a wavelength-time converter converting an output of the sensor by wavelength-time conversion; a second pseudorandom number generator generating a second pseudorandom number code string which is different in frequency from and is the same in bit length and code string as the first pseudorandom number code string; a mixer mixing an output signal of the wavelength-time converter with an output signal of the second pseudorandom number generator; and an integrator integrating an output of the mixer.