Optical Receiver Fast Recovery Time via High Voltage Reduction
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Solution Overview
Problem
Prior art photodetector circuits face challenges in recovering quickly from high power optical pulses, which can saturate and damage the transimpedance amplifier and photodetector, leading to prolonged recovery times and potential damage due to reliance on the amplifier's output for protection mechanisms.
Innovation Solution
The proposed solution involves a photoelectric receiver circuit with a transimpedance amplifier, a photodetector, a high voltage supply variation sensing element, and a current limiter, which reduces the high voltage supply and limits photocurrent saturation, thereby improving recovery time without affecting the amplifier's bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transimpedance amplifier is used to convert photocurrent to voltage, then the optical receiver can process the signal, but the amplifier saturates and takes a long time to recover from high power optical pulses
Solution Approach 1:
The circuit proactively reduces the high voltage supply before the transimpedance amplifier saturates, preventing the saturation condition from occurring in the first place. This preliminary protective action eliminates the need for recovery time entirely, as the amplifier never enters the saturated state that would require recovery.
Solution Approach 2:
The circuit applies a counter-action by reducing the high voltage supply when high optical power is detected, which opposes the tendency of the amplifier to saturate. This preliminary anti-action prevents the harmful saturation effect before it can occur, protecting the amplifier and eliminating recovery time loss.
2Loss of time
If variable feedback impedance is used to reduce input impedance during saturation, then recovery time is improved, but capacitance is added to the feedback path impacting frequency response and noise
Solution Approach 1:
The invention extracts the protection function from the feedback path entirely. Instead of modifying the feedback path with variable impedance elements, the high voltage supply reduction mechanism operates independently in the bias voltage path, eliminating the need for complex feedback modifications while achieving the same protective effect.
Solution Approach 2:
The circuit separates the protection mechanism from the signal processing path. The high voltage supply reduction operates independently in the bias path, while the feedback path remains simple and unchanged. This segmentation allows recovery time improvement without adding complexity to the feedback path.
3Ease of operation
If the output of the transimpedance amplifier is used to apply protection, then the circuit can respond to high photocurrent, but damage occurs before the output can respond
Solution Approach 1:
The circuit detects high optical power at the photodetector level and proactively reduces the high voltage supply before the transimpedance amplifier can saturate or be damaged. This preliminary action occurs upstream in the signal path, enabling protection before damage can occur, rather than waiting for the amplifier output to respond.
Solution Approach 2:
The high voltage supply reduction acts as a cushioning mechanism that prepares the system in advance against potential damage from high optical power pulses. By reducing the bias voltage before the amplifier is exposed to damaging conditions, the circuit provides beforehand protection that prevents damage rather than responding after damage occurs.
4Reliability
If a resistance is used in series with the photodetector to reduce impact of high power pulse, then low frequency signals are protected, but bandwidth is impacted and photocurrent is maintained during saturation
Solution Approach 1:
The circuit changes the parameter of high voltage supply dynamically based on optical power conditions. When high optical power is detected, the high voltage supply is reduced, which changes the operating point of the photodetector and limits photocurrent saturation. This parameter change provides protection without requiring a series resistance that would continuously limit bandwidth.
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
The circuit achieves fast recovery times by reducing the high voltage supply and limiting photocurrent saturation, protecting the transimpedance amplifier and maintaining bandwidth during recovery, thus preventing damage from high optical power pulses.
Implementation Method 1
a photoelectric receiver circuit for converting an optical signal to an electrical signal
Data Source
AI summary
A photoelectric receiver circuit for converting an optical signal to an electrical signal is presented. The receiver includes a photodetector connected between a transimpedance amplifier input and a high voltage supply providing a bias voltage to the photodetector. A high voltage supply variation sensing element is connected between the high voltage supply and a current controlled current source, where the current controlled source output is connected to the input of the transimpedance amplifier. A current limiter is connected between the high voltage supply and a high voltage source. The photocurrent passing through the current limiter lowers the high voltage supply and is detected by the sensing element. Current from the sensing element is processed at the input of the transimpedance amplifier to minimize the current into the transimpedance amplifier, limiting the saturation of the amplifier, thus improving recovery time when a high optical power pulse impinges the photodetector.