Optical Receiver Gain Control for Burst Signal Level Switching
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Solution Overview
Problem
Existing optical receivers in PON systems face challenges in maintaining high-speed responsiveness and identical code continuation resistance due to transient level variations and dependence on signal patterns, leading to erroneous gain switching and degraded code continuation resistance.
Innovation Solution
An optical receiver with a light receiving element, preamplifier, level detecting means, and time constant switching control means that adjusts the time constant and conversion gain based on the number of consecutive identical digits in a packet, switching between short and long time constants to stabilize signal reproduction across varying light levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a short time constant is used in the level detecting circuit, then high-speed responsiveness is improved, but identical code continuation resistance deteriorates
Solution Approach 1:
The patent applies dynamics by making the time constant of the level detecting circuit variable rather than fixed. The time constant is dynamically adjusted based on the reception level of the optical signal - using a short time constant for high reception levels to achieve fast response, and a long time constant for low reception levels to maintain stability during identical code continuation. This dynamic adaptation resolves the contradiction between speed and reliability.
Solution Approach 2:
The patent changes the parameter of time constant based on reception level conditions. By switching between different time constant values (short for high level, long for low level), the system optimizes both high-speed responsiveness and identical code continuation resistance according to the actual signal conditions, thereby resolving the technical contradiction.
2Reliability
If a long time constant is used in the level detecting circuit, then identical code continuation resistance is improved, but high-speed responsiveness deteriorates
Solution Approach 1:
The system dynamically selects the appropriate time constant based on reception level. When reception level is high, a short time constant is used for fast response. When reception level is low, a long time constant is used for stable identical code continuation. This dynamic selection resolves the contradiction between reliability and speed.
Solution Approach 2:
The time constant parameter is changed according to reception level conditions. The system switches between long and short time constants to optimize performance for different signal conditions, thereby achieving both high-speed responsiveness and identical code continuation resistance in appropriate scenarios.
3Reliability
If automatic gain control is implemented to handle wide dynamic range, then stable reproduction of packets with different light receiving levels is achieved, but device complexity increases
Solution Approach 1:
The patent segments the AGC function into two independent parts: a variable gain amplifier for dynamic range adaptation and a level detecting circuit with switchable time constants for stable level detection. This segmentation allows each component to be optimized independently, achieving stable reproduction without excessive overall complexity.
Solution Approach 2:
The level detecting circuit dynamically switches between short and long time constants based on reception level, enabling the AGC system to handle wide dynamic range efficiently. This dynamic behavior improves stability across different light receiving levels while keeping the circuit design manageable through targeted complexity only where needed.
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 optical receiver achieves a wide-dynamic range characteristic, ensuring stable reproduction of burst signals with different light receiving levels and excellent high-speed responsiveness and identical code continuation resistance.
Implementation Method 1
a light receiving element for outputting a current corresponding to a light receiving level of a received light signal
Data Source
AI summary
An optical receiver of wide-dynamic range characteristic that stably reproduces a burst signal having different light receiving levels. A preamplifier converts an output from a light receiving element into a voltage signal. A level detecting circuit includes: a first level detecting unit having a shorter time constant; and a second level detecting unit having a longer time constant and switching over to any of the level detecting units in response to a time constant switching signal to detect a voltage level of an output voltage signal output from the preamplifier. An amplifier variably controls conversion gain of the preamplifier based on the detecting result. A time constant switching control outputs the time constant switching signal to the level detecting unit based on the output voltage signal from the preamplifier, to select the first level detecting unit or the second detecting unit based on a number of consecutive identical digits being equal to, smaller, or larger than the predetermined number.