Monolithic Optically Sampled ADC for Low-Jitter High-Speed Conversion
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Solution Overview
Problem
Current analog-to-digital converters, particularly those using electro-optic devices, face challenges in achieving high sampling rates and low jitter due to nonlinearities in photonic components, leading to increased costs and complexity, and existing designs struggle to fully exploit the advantages of optical sampling.
Innovation Solution
The integration of all electrical and photonic components on a single chip using a single continuous wave laser and a multi-wavelength generator with a chromatic dispersion element, along with a pre-distortion stage to compensate nonlinearities, enables a monolithic high sampling rate ADC with reduced jitter and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electro-optic devices are used to achieve high sampling rates, then sampling rate is improved, but device complexity and cost increase due to nonlinearities in photonic components
Solution Approach 1:
The patent integrates multiple photonic components (multi-wavelength generator, chromatic dispersion element, electro-optic modulator, demultiplexer, and photodetectors) onto a single photonic integrated circuit chip. This merging eliminates the need for separate discrete components, reducing overall device complexity while maintaining high sampling rates through optical sampling.
Solution Approach 2:
The photonic integrated circuit performs multiple functions within a single device: wavelength generation, pulse shaping, optical sampling, signal demultiplexing, and electrical conversion. This multi-functionality reduces the number of separate components needed, thereby reducing device complexity and cost while achieving high sampling rates.
2Speed
If multiple discrete photonic components are used, then high sampling rates can be achieved, but manufacturing cost and fabrication complexity increase
Solution Approach 1:
The patent combines multiple discrete photonic components into a single photonic integrated circuit chip, enabling high-volume fabrication using standard semiconductor manufacturing processes. This integration dramatically reduces manufacturing cost compared to assembling multiple discrete components, while maintaining the high sampling rates enabled by optical sampling.
Solution Approach 2:
The patent replaces mechanical assembly of discrete photonic components with monolithic photonic integrated circuit fabrication. This substitution enables scalable, high-volume manufacturing with consistent performance, reducing both cost and complexity compared to traditional discrete component assembly methods.
3Speed
If optical sampling is used to exceed electronic ADC limits, then sampling rate is improved, but jitter increases due to nonlinearities in photonic components
Solution Approach 1:
The patent incorporates a pre-distortion stage that compensates for nonlinearities in the photonic components before the signal undergoes optical sampling. By correcting distortion in advance, the system maintains low jitter performance even at high sampling rates, overcoming the limitation of using optical sampling to exceed electronic ADC limits.
4Speed
If time-interleaving technique is used with multiple ADC cores, then sampling rate is improved, but device complexity increases due to tight time alignment requirements
Solution Approach 1:
The patent replaces the complex electronic time-interleaving architecture with optical sampling followed by electrical demultiplexing. The optical sampling stage naturally provides the required time alignment through the properties of light propagation, eliminating the need for complex electronic synchronization circuits and reducing overall device complexity while achieving high sampling rates.
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 results in a more efficient, cost-effective, and scalable ADC with improved sampling rates and reduced jitter, enabling higher SNR and easier fabrication in high volumes.
Implementation Method 1
an electro-optic modulator sampling an analogue signal provided at an electrical input
Implementation Method 2
at least one photodetector converting the sampled signal into an electrical signal
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to an optically sampled Analog-to-Digital Converter comprising an optical source (1) providing radiation of one single wavelength, an electro-optic modulator (4) sampling an analogue signal provided at an electrical input (42), a de-multiplexer (5) de-multiplexing the optically sampled signal, at least one photodetector (7), transimpedance amplifiers (8) amplifying the signals and at least one analogue-to-digital converter (9) converting the analogue signal into a digital signal. The invention relates also to a method for using the ADC. One object of the invention is to overcome problems in compensating the nonlinearities in the photonic parts and to simplify and reduce the overall cost for optically sampled ADCs. This is solved by a multi wavelength generator (2) and a chromatic dispersion element (3) that provide generating several wavelengths and delays of the single wavelength radiation of the optical source and that except to the optical source all electrical and photonic components are integrated on one chip.