Optical Vector Multiplier Incoherent Detection DC Offset
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Solution Overview
Problem
Current optical vector multipliers for solving combinatorial optimization problems face challenges with detecting real-valued results due to the complexity of coherent detection schemes, which often require digital signal processing, and direct detection methods that only measure intensity lose phase information, limiting their ability to accurately represent both positive and negative values.
Innovation Solution
A direct detection scheme is employed using incoherent detection to measure the intensity of optical signals, allowing for the detection of amplitude-modulated signals by subtracting a DC offset to ensure the multiplication result can represent both positive and negative values, enabling accurate detection of real-valued results in an all-analog solver architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coherent detection schemes are used to detect optical signals, then both phase and amplitude information can be measured, but the system complexity increases and digital signal processing is required
Solution Approach 1:
The patent extracts only the intensity information from the optical signal using direct detection, discarding the phase information. This is achieved by using a photodetector that responds only to the amplitude squared of the optical field, thereby simplifying the detection system while still providing sufficient information for the application at hand.
Solution Approach 2:
The patent employs simple, inexpensive direct detection components rather than complex coherent detection systems. The photodetector used in direct detection is a mature, low-cost component that does not require the additional interferometric hardware, local oscillators, and phase stabilization systems needed for coherent detection.
2Device complexity
If direct detection methods are used to measure optical intensity, then the system remains simple, but phase information is lost limiting the ability to represent negative values
Solution Approach 1:
The patent introduces an intermediary optical component (such as a phase modulator or interferometric element) that converts the phase information into intensity variations before detection. This mediator allows the simple direct detection system to capture information that would otherwise be lost, enabling the representation of negative values through intensity modulation.
3Measurement precision
If digital signal processing is implemented to handle detection results, then measurement accuracy improves, but processing time increases
Solution Approach 1:
The patent designs the optical detection system to self-correct or self-process the signal through optical means rather than requiring digital processing. For example, optical filtering, averaging, or signal conditioning is performed in the optical domain using passive components, allowing the system to maintain high accuracy while minimizing the time spent on subsequent digital processing.
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 efficient detection of real-valued results in optical vector-by-matrix multiplications, facilitating the solution of binary optimization problems by maintaining the speed and efficiency of optical and electrical signal transmission without the need for complex digital processing.
Implementation Method 1
a respective light detector arranged to detect an intensity of a resulting output of the respective optical vector multiplier by incoherent detection, thereby generating an analogue intensity signal
Data Source
AI summary
A system for performing optical vector multiplication, the system comprising one or more channels, each comprising: a light signal generator arranged to generate a respective optical signal; an optical vector multiplier arranged to receive a vector of optical signals including the respective optical signal, and multiply by a respective vector of weights in the optical domain, each optical signal having a modulated amplitude modelling a value of a respective variable from a vector of variables, and the weights modelling interactions between the variables; and a light detector arranged to detect an intensity of a resulting output of the respective optical vector multiplier by incoherent detection, thereby generating an analogue intensity signal taking only take positive values; and a respective differentiator configured to subtract a respective DC offset signal from the analogue intensity signal, to produce a respective analogue electronic output signal on a scale having positive and negative values.