Differential Optical Receiver Circuit for Supply Noise Cancellation
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Solution Overview
Problem
Conventional optical receivers are susceptible to noise from voltage supplies and dark currents produced by photodetectors, which reduces the signal-to-noise ratio and affects the accuracy of optical signal detection.
Innovation Solution
The development of optical receivers that perform optical-to-electric conversion and amplification in a differential fashion, involving multiple levels of signal subtraction to cancel noise, including photocurrent subtraction and differential amplification, thereby reducing noise susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical receivers are used, then the structure is simple, but noise from voltage supplies and dark currents reduces the signal-to-noise ratio
Solution Approach 1:
The optical receiver is divided into multiple photodetectors (first, second, third, and fourth photodetectors) arranged in a differential configuration. Each photodetector processes specific optical signals, and their outputs are combined through differential amplification to cancel noise components while preserving the desired signal.
Solution Approach 2:
The patent converts the harmful effect of dark currents and voltage supply noise into a beneficial cancellation mechanism. By using differential photodetectors and differential amplification, the noise and dark currents affecting both channels are subtracted from each other, transforming what would be harmful interference into a noise-cancellation benefit.
2Object-affected harmful factors
If differential photodetectors and differential amplification are used, then noise susceptibility is reduced, but the device complexity increases
Solution Approach 1:
Multiple photodetectors and amplification stages are merged into a unified differential receiver architecture. The first and second photodetectors receive and process optical signals, while the third and fourth photodetectors process reference signals, with all outputs fed into differential amplifiers that combine the signals to achieve noise cancellation.
Solution Approach 2:
The patent introduces intermediate differential amplification stages that act as mediators between the photodetectors and the final output. These amplifiers process the differential signals from multiple photodetectors, performing subtraction and amplification to eliminate noise while preserving the optical signal information.
3Reliability
If multiple photodetectors are used for differential detection, then the signal-to-noise ratio increases, but the area occupied on the substrate increases
Solution Approach 1:
The patent integrates multiple photodetectors and their associated circuitry into a compact monolithic structure on a common substrate. The first, second, third, and fourth photodetectors are arranged in a space-efficient configuration where their functional blocks are nested or closely integrated, reducing the overall area while maintaining the differential architecture.
Solution Approach 2:
The photodetectors and amplifiers are designed with multi-functionality, where the same structural components serve multiple purposes in the differential detection process. The common substrate integrates both signal detection and reference detection functions, as well as multiple amplification stages, into a unified compact structure.
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 wider dynamic range, increased signal-to-noise ratio, larger output swing, and improved supply-noise immunity, enhancing the performance of optical receivers in various applications.
Implementation Method 1
Photodetectors are sensors configured to generate electric signals responsive to reception of light. In optical communications, photodetectors are often used to detect optical signals.
Implementation Method 2
an optical receiver comprising a differential amplifier having first and second inputs and first and second outputs; first and second photodetectors coupled to the first input of the differential amplifier; and third and fourth photodetectors coupled to the second input of the differential amplifier
Data Source
AI summary
Low-noise optical differential receivers are described. Such differential receivers may include a differential amplifier having first and second inputs and first and second outputs, and four photodetectors. A first and a second of such photodetectors are coupled to the first input of the differential amplifier, and a third and a fourth of such photodetectors are coupled to the second input of the differential amplifier. The anode of the first photodetector and the cathode of the second photodetector are coupled to the first input of the differential amplifier. The cathode of the third photodetector and the anode of the fourth photodetector are coupled to the second input of the differential amplifier. The optical receiver may involve two stages of signal subtraction, which may significantly increase noise immunity.