Optical Transceiver Coupling Circuit for Common-Mode Shift
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Solution Overview
Problem
Existing methods for coupling optical transceivers and processing modules in communication devices, such as optical line terminations, face challenges in handling different common mode voltage levels, leading to signal amplitude reduction, jitter introduction, and inadequate DC response, especially in burst mode operations.
Innovation Solution
A coupling module that uses high-pass and low-pass filters in parallel, along with a feedback circuit, to adjust and maintain the common mode voltage level, ensuring jitter-free communication and preserving signal integrity and bandwidth across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a resistor divider is used to couple the optical transceiver to the processing module, then common mode voltage level shifting is achieved, but signal amplitude is reduced
Solution Approach 1:
The patent introduces a capacitor as an intermediary coupling element between the optical transceiver and processing module. This capacitor blocks DC voltage while allowing AC signal passage, thereby achieving common mode voltage isolation without the signal amplitude reduction inherent in resistor divider approaches. The capacitor serves as a mediator that enables voltage level incompatibility while preserving signal integrity.
2Adaptability or versatility
If capacitive coupling is used to obtain the desired level shift, then common mode voltage compatibility is achieved, but DC response is inadequate and burst mode operation is compromised
Solution Approach 1:
The patent merges two previously separate coupling approaches (resistor divider for DC voltage handling and capacitor for AC signal coupling) into a unified hybrid coupling circuit. This combination allows the circuit to simultaneously achieve DC voltage level shifting through the resistor network and AC signal coupling through the capacitor, thereby resolving the DC response deficiency of pure capacitive coupling while maintaining common mode voltage compatibility.
3Adaptability or versatility
If bus transceivers are used to couple the optical transceiver to the processing module, then common mode voltage compatibility is achieved, but jitter is introduced into the signal
Solution Approach 1:
The patent employs a capacitor as an intermediary coupling element that blocks DC voltage while allowing AC signal passage. This approach achieves common mode voltage isolation without introducing the jitter that characterizes bus transceiver-based coupling. The capacitor mediates the connection in a way that preserves signal timing integrity while handling voltage level incompatibility.
4Device complexity
If a single-type coupling design is used, then simplicity is maintained, but adaptability to different optical transceiver types is lost
Solution Approach 1:
The patent designs a hybrid coupling circuit that functions universally with different types of optical transceivers. By combining resistor and capacitor elements in a specific configuration, the circuit achieves multi-functionality: it handles DC voltage level shifting, AC signal coupling, and impedance matching in a single integrated design that adapts to various transceiver types without requiring redesign.
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 solution enables efficient communication of high-speed signals by maintaining signal amplitude and providing the required common mode voltage, while minimizing jitter and ensuring appropriate DC coupling, thus addressing the limitations of previous methods.
Implementation Method 1
The split signals for both the positive differential signal path and the negative differential signal path can then be provided to a high-pass filter and a low-pass filter that are connected in parallel
Implementation Method 2
a feedback circuit, to adjust and maintain the common mode voltage level
Data Source
AI summary
A coupling module can be used to communicate high speed signals between an optical transceiver and a processing module of an optical communication device, such as an optical line termination (OLT) or an optical network unit (ONU). The coupling module can adjust the common mode voltage level of a differential signal output by the optical transceiver to the common mode voltage level required by the processing module. In addition, the coupling module splits each of the differential output signals from the optical transceiver and passes the split signals to both a high-pass filter and a low-pass filter that are connected in parallel. An adapter module can be connected to the coupling module such that the coupling module can receive different differential signals from different optical transceivers.