Optical Receiver Dynamic Capacitance Switching
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Solution Overview
Problem
Conventional optical receivers face challenges in measuring the received signal intensity of multiplexed optical signals with high precision and speed, particularly in high-speed and large-capacity communication networks like 100G form-factor pluggable (CFP), where the increased size and power consumption of measurement circuits and wiring hinder downsizing efforts.
Innovation Solution
An optical receiver design that includes a plurality of photo detectors, a detecting circuit with both low-gain and high-gain amplifying circuits, and an MCU that selects and amplifies current signals from the photo detectors, allowing for precise measurement of signal intensity by switching in ascending order of intensity, thereby reducing measurement time and avoiding waveform bluntness issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one monitor circuit is configured to measure received signal intensity by sequentially switching the four optical signals in a time division method, then the total size of measurement circuits and wiring lines is reduced, but a large capacitance capacitor is needed to improve measurement precision by restricting frequency band, which causes rising edge and falling edge of output waveform to become blunt, increasing measurement time
Solution Approach 1:
The patent applies dynamics by making the capacitance value of the capacitor variable rather than fixed. The capacitance switching circuit switches between a first capacitor with a first capacitance value and a second capacitor with a second capacitance value based on signal intensity. This dynamic adjustment allows the measurement circuit to adapt to different signal conditions, reducing measurement time while maintaining precision without requiring consistently large capacitance values that would blunt waveforms.
Solution Approach 2:
The patent changes the parameter of capacitance from a fixed value to a variable value that can be switched between at least two different capacitance values. By changing the capacitance parameter dynamically based on signal intensity, the system achieves both circuit downsizing and reduced measurement time while maintaining measurement precision, resolving the contradiction between device complexity and time loss.
2Measurement precision
If a large capacitance capacitor is used to restrict frequency band and improve measurement precision, then measurement precision is improved, but rising edge and falling edge of output waveform become blunt, requiring increased switching period and thus increasing measurement time
Solution Approach 1:
The patent uses dynamic capacitance switching to adjust the frequency band restriction level according to signal intensity. For strong signals, a smaller capacitance is used to maintain fast waveform edges and short measurement time. For weak signals, a larger capacitance is used to ensure sufficient measurement precision. This dynamic adaptation resolves the contradiction between measurement precision and measurement time.
Solution Approach 2:
The patent changes the capacitance parameter based on signal intensity conditions. By switching between different capacitance values, the system optimizes the trade-off between measurement precision and measurement time, avoiding the need to always use large capacitance that would blunt waveforms and increase measurement time.
3Measurement precision
If the switching period is increased to measure continuous received signals with required precision, then measurement precision is maintained, but measurement time increases and measurement result may not be transmitted to upper layer in time defined by MSA
Solution Approach 1:
The patent dynamically adjusts the capacitance value based on signal intensity to optimize measurement speed. By using smaller capacitance values for stronger signals, the measurement circuit can complete measurements faster while maintaining precision, thereby increasing productivity and meeting MSA transmission time requirements.
Solution Approach 2:
The patent changes the capacitance parameter dynamically to match signal conditions, enabling faster measurements for strong signals and maintaining precision for weak signals. This parameter adaptation resolves the contradiction between measurement precision and measurement speed, improving overall productivity.
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 enables fast and precise measurement of received signal intensity without increasing switching time, ensuring measurement precision and reducing the overall measurement time while maintaining a compact design.
Implementation Method 1
a plurality of photo detectors each converting an optical signal to a current signal
Data Source
AI summary
The integrated optical receiver module includes a plurality of PDs each converting an optical signal to a current signal, and outputs a current signal selected from a plurality of current signals. The RSSI circuit converts the current signal into a voltage signal, outputs a first amplified signal obtained by amplifying the voltage signal by a first gain, and outputs a second amplified signal obtained by amplifying the voltage signal by a second gain larger than the first gain. The MCU outputs a first selection signal to the integrated optical receiver module to acquire intensity of the first amplified signal with respect to all of the current signals in a predetermined order, outputs a second selection signal to the integrated optical receiver module to acquire intensity of the second amplified signal with respect to all of the current signals in the ascending order of the acquired intensity of the first amplified signal, and derives intensity of each of the optical signals from the acquired intensity of the respective second signals.