Optical Amplitude-to-Time Mapping for High-Resolution Signal Digitizing
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Solution Overview
Problem
Conventional electronic analog-to-digital converters (ADCs) face limitations in high-speed and high-precision applications due to amplitude resolution constraints, noise sources like thermal noise and sampling jitter, and introduce distortions in photonic methods, limiting their effectiveness in wideband communication and scientific research.
Innovation Solution
A signal digitizing system and method utilizing amplitude-to-time optical mapping, which converts analog signal amplitude information into temporal information through optical pulse spectral changes and wavelength-to-time conversion, followed by digital signal processing to produce a high-resolution digital reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electronic ADCs are used for high-speed digitization, then sampling speed can be achieved, but amplitude resolution and measurement precision deteriorate due to quantization noise and sampling jitter
Solution Approach 1:
The patent replaces the electronic amplitude quantization mechanism with an optical time-domain mapping mechanism. Instead of using electronic ADCs that quantize amplitude directly, the system uses optical pulses whose arrival times encode the amplitude information of the input signal, thereby substituting electronic measurement with optical measurement to avoid electronic noise and jitter limitations
Solution Approach 2:
The patent changes the domain parameter from amplitude to time. By mapping the amplitude information to temporal delays of optical pulses, the system transforms the measurement parameter that the ADC must resolve, allowing high-speed sampling without sacrificing resolution since time-domain measurements are not subject to the same noise limitations as amplitude-domain quantization
2Measurement precision
If photonic time-stretch ADC is used to improve amplitude resolution, then measurement precision is improved, but system complexity and distortion increase due to linearization requirements and chromatic dispersion compensation
Solution Approach 1:
The patent extracts and eliminates the problematic MZ modulator component from the photonic time-stretch architecture. By using direct optical pulse generation with programmable delays instead of MZ modulation, the system removes the source of sinusoidal nonlinearity and the associated linearization complexity while maintaining the time-stretch advantage
Solution Approach 2:
The patent uses a simplified optical copying approach where amplitude information is directly copied onto temporal positions of optical pulses without requiring complex modulation and demodulation processes. This direct mapping copies the signal information in a form that is naturally suited for high-resolution digitization without introducing the distortions inherent in MZ-based systems
3Measurement precision
If optically-sampled ADCs are used to reduce jitter noise, then sampling speed and precision are improved, but performance is limited by photodetector noise, laser amplitude fluctuations, and nonlinear distortions
Solution Approach 1:
The patent substitutes the photodetector-based amplitude detection with a time-domain detection scheme. Instead of detecting optical amplitude with noisy photodetectors and RF amplifiers, the system detects the temporal positions of optical pulses, which are inherently more precise and not subject to the same noise mechanisms, thereby replacing a noisy electronic detection system with a precise optical timing system
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 enables high dynamic range, wideband, and continuous time digitization beyond conventional ADCs, achieving higher resolution and reduced noise, suitable for applications like wideband communication and scientific research.
Implementation Method 1
an amplitude tunable filter (ATF) adapted to optically map the amplitude information of the analog signal to wavelength information by impressing on the train of optical pulses spectral changes induced by the amplitude information of the analog signal
Implementation Method 2
a dispersive element adapted to optically map the wavelength information to temporal information by broadening the train of optical pulses in the time domain received from the ATF
Data Source
AI summary
A signal digitizing system and method based on analog-to-time optical mapping, optically maps amplitude information of an analog signal of interest first into wavelength information using an amplitude tunable filter (ATF) to impress spectral changes induced by the amplitude of the analog signal onto a carrier signal, i.e. a train of optical pulses, and next from wavelength information to temporal information using a dispersive element so that temporal information representing the amplitude information is encoded in the time domain in the carrier signal. Optical-to-electrical conversion of the optical pulses into voltage waveforms and subsequently digitizing the voltage waveforms into a digital image enables the temporal information to be resolved and quantized in the time domain. The digital image may them be digital signal processed to digitally reconstruct the analog signal based on the temporal information with high fidelity.