Receiver Photodiode Biasing Circuit Noise Reduction
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Solution Overview
Problem
Existing optical transceivers face performance degradation due to noise introduced in the supply voltage used to bias the receiver photodiode, especially as components are integrated on the same chip, making power supply and ground line isolation challenging.
Innovation Solution
The optical circuit employs one or more biasing photodiodes to generate a bias voltage using a source optical signal, rather than relying on the supply voltage, thereby reducing noise and improving performance. Additionally, a compensation photodiode is used to remove the DC component from the electrical signal, generating a fully differential electrical signal that allows direct coupling to a differential TIA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If supply voltage is used to bias the receiver photodiode, then the circuit is simple, but noise is introduced that degrades performance
Solution Approach 1:
The photodiode array is divided into multiple individual photodiodes, each generating a portion of the bias voltage. This segmentation allows the biasing function to be separated from the main supply voltage, isolating the receiver photodiode biasing from noise in the shared power supply while maintaining circuit simplicity through modular design.
Solution Approach 2:
The biasing photodiodes generate the bias voltage autonomously by converting optical signals directly into electrical bias voltage through the photovoltaic effect. This self-service mechanism eliminates the need for external voltage regulators or complex noise filtering circuits, providing a clean bias voltage source that is inherently isolated from supply voltage noise.
2Object-affected harmful factors
If regulators are used to filter noise from supply voltage, then noise is reduced, but the regulators are not ideal and some noise remains
Solution Approach 1:
The electrical regulation mechanism is replaced with an optical-to-electrical conversion mechanism. Instead of using electrical regulators to filter noise from the supply voltage, the patent uses photodiodes to directly convert optical signals into clean bias voltage, fundamentally substituting the noise-prone electrical regulation approach with an optical-based generation approach that inherently produces low-noise output.
3Productivity
If components are integrated on the same chip, then productivity increases, but isolation of power supply and ground lines becomes challenging
Solution Approach 1:
Optical signals serve as an intermediary medium between the light source and the receiver photodiode. By using optical signals rather than direct electrical connections for biasing, the patent creates an isolation barrier that prevents noise and cross-talk from propagating between integrated components on the same chip, enabling high-density integration without compromising signal integrity.
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 reduces noise and cross-talk in the optical circuit, leading to improved performance and faster response times for the receiver photodiode, especially in high-speed applications.
Implementation Method 1
The first biasing photodiode generates a bias voltage for the receiver photodiode based on a first portion of the first optical signal
Implementation Method 2
The receiver photodiode converts a second optical signal into an electrical signal
Data Source
AI summary
The present disclosure describes an optical system that uses a source optical signal to bias a receiver photodiode. The system includes an optical source, a receiver photodiode, a first biasing photodiode, a variable optical attenuator, and a compensation photodiode. The optical source produces a first optical signal. The receiver photodiode converts a second optical signal into an electrical signal. The first biasing photodiode generates a bias voltage for the receiver photodiode based on a first portion of the first optical signal. The variable optical attenuator produces a third optical signal based on (i) a second portion of the first optical signal and (ii) a portion of the electrical signal. The compensation photodiode passes the portion of the electrical signal based on the third optical signal.