Optical Receiver Gain Control for Bandwidth Without Ringing
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Solution Overview
Problem
In 10G PON and other optical communication networks, there is a challenge to reduce the cost of optical components without compromising performance, particularly due to the high cost and complex process of avalanche photon diodes (APDs) used in optical receivers.
Innovation Solution
The proposed solution is an optical receiver design that utilizes a cost-effective photodetector, such as a photodiode, coupled with a trans-impedance amplifying unit, a control unit, and automatic gain controllers. The control unit includes inductors and field-effect transistors, which work together to adjust the current conduction capability of the field-effect transistor based on the output voltage signal from the automatic gain controller, thereby reducing drain-source resistance and alleviating signal deterioration and ringing phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If avalanche photon diode (APD) is used as receiving front end, then performance is improved, but cost and process complexity increase
Solution Approach 1:
The patent replaces the expensive APD with a cheaper photodiode, accepting that the photodiode alone cannot achieve the same performance. Instead, it uses a cost-effective combination of photodiode + trans-impedance amplifier + peak adjustment mechanism to achieve the desired performance at lower cost.
Solution Approach 2:
The patent introduces a trans-impedance amplifier as an intermediary component between the photodiode and the output. This amplifier compensates for the lower performance of the photodiode by providing signal amplification and impedance transformation, enabling the cheap photodiode to achieve performance comparable to expensive APD.
2Speed
If inductor is added to control unit, then bandwidth is improved, but signal peak may become excessive causing deterioration
Solution Approach 1:
The patent implements a feedback mechanism where the automatic gain controller continuously monitors the signal and dynamically adjusts the gain of the trans-impedance amplifier. When the signal peak becomes excessive due to the inductor's bandwidth enhancement, the feedback loop reduces the amplifier gain to prevent signal deterioration and oscillation.
Solution Approach 2:
The patent makes the system dynamic by allowing the trans-impedance amplifier gain to vary automatically based on signal conditions. The variable gain capability enables the system to adapt to different signal levels, preventing excessive peaks while maintaining high bandwidth performance.
3Ease of manufacture
If photodiode is used instead of APD, then cost is reduced, but signal performance may deteriorate
Solution Approach 1:
The patent merges multiple components (photodiode, trans-impedance amplifier, automatic gain controller) into a coordinated system. The combination of these components compensates for the photodiode's lower inherent performance, achieving signal quality comparable to APD while maintaining cost advantages.
Solution Approach 2:
The patent changes the operating parameters of the trans-impedance amplifier dynamically through automatic gain control. By adjusting the amplifier gain based on signal conditions, the system optimizes the overall performance of the photodiode-based receiver, compensating for the photodiode's lower sensitivity and bandwidth limitations.
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 design ensures the performance of the optical receiver while reducing costs by using a cost-effective photodetector and optimizing the signal transmission bandwidth, thereby avoiding signal deterioration and reducing the occurrence of ringing or oscillation phenomena in high input signal scenarios.
Implementation Method 1
at least a photodiode... an input end of the first branch circuit receives an output signal from the photodiode
Implementation Method 2
a field-effect transistor coupled in parallel to the one or more inductors... the automatic gain controller is configured to output a voltage signal to the gate of the field-effect transistor, where the output voltage signal is used to change a current conduction capability of the field-effect transistor
Data Source
AI summary
This application relates to an optical receiver. The optical receiver includes a photodiode, a trans-impedance amplifying unit, a control unit, and one or more automatic gain controllers. The control unit includes one or more control subunits. The control subunit includes one or more inductors, and a field-effect transistor coupled in parallel to the one or more inductors. An input end of each automatic gain controller is coupled to an output end of a corresponding control subunit, and an output end of the automatic gain controller is coupled to a gate of a field-effect transistor included in the corresponding control subunit. The automatic gain controller is configured to output a voltage signal to the gate of the field-effect transistor, where the output voltage signal is used to change a current conduction capability of the field-effect transistor.