Coupling Module for DC Offset Shifting in High-Speed Optical Links
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Solution Overview
Problem
In optical line termination systems, the mismatch in DC offset voltage levels between optical transceivers and processing modules leads to communication challenges, with existing solutions like resistive dividers, capacitive coupling, and bus transceivers either discarding signal strength, introducing jitter, or failing to provide appropriate DC response during idle times.
Innovation Solution
A coupling module that splits the signal and passes it through both high pass and low pass filters in parallel, combined with a level shifter, to adjust the DC offset voltage and maintain signal integrity while preserving bandwidth, using components like capacitors, inductors, and operational amplifiers to ensure proper voltage levels are reached by the processing module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a resistive divider is used to couple the optical transceiver to the processing module to obtain DC level shift, then compatibility between modules is improved, but signal strength is significantly discarded
Solution Approach 1:
The patent introduces an intermediary circuit between the optical transceiver and processing module that performs DC level shifting without using a resistive divider. This intermediary circuit preserves signal strength while enabling compatibility between modules with different DC voltage requirements.
Solution Approach 2:
The patent changes the DC voltage parameter of the signal through an active circuit that can dynamically adjust the DC level while maintaining signal integrity. This allows the signal to adapt to different voltage requirements without discarding signal strength.
2Loss of energy
If capacitive coupling is used to obtain DC level shift, then signal strength is preserved, but appropriate DC response is not provided during long idle times or long strings of 1s and 0s
Solution Approach 1:
The patent introduces an intermediary active circuit that mediates between the capacitive coupling and the processing module. This circuit provides the necessary DC response during idle times and long strings of identical bits while preserving the signal strength benefits of capacitive coupling.
Solution Approach 2:
The circuit includes self-service mechanisms that automatically maintain appropriate DC levels during idle conditions without external intervention. The circuit monitors its own state and adjusts accordingly to ensure reliable DC response.
3Adaptability or versatility
If bus transceivers are used to obtain DC level shift, then compatibility is improved, but jitter is undesirably introduced into the signal
Solution Approach 1:
The patent introduces an intermediary circuit that performs DC level shifting without using bus transceivers. This intermediary approach maintains compatibility while avoiding the jitter generation inherent in traditional bus transceiver implementations.
Solution Approach 2:
The patent replaces the mechanical/electrical switching mechanism of bus transceivers with an active voltage translation circuit. This substitution eliminates the jitter-generating switching action while maintaining the DC level shifting function.
4Adaptability or versatility
If the optical transceiver and processing module are provided in separate circuits with different DC offset voltage levels, then design flexibility is improved, but direct signal coupling becomes impossible
Solution Approach 1:
The patent introduces an intermediary DC level shifting circuit that enables signal coupling between separately designed modules with different DC voltage requirements. This intermediary allows each module to be independently optimized while maintaining interoperability.
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
Enables jitter-free high-speed signal communication with simultaneous DC coupling and wide bandwidth, maintaining signal swing and integrity across varying voltage levels without significant phase shift.
Implementation Method 1
The coupling module splits the output signal from the transceiver and passes the signal to both a high pass filter and a low pass filter that are connected in parallel
Implementation Method 2
The level shifter adjusts the DC offset voltage from the transceiver to the DC offset voltage required by the processing module
Data Source
Figure 1
Figure 2
Figure 3A~3B
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 DC offset voltage level of the signal output by the optical transceiver to the DC offset voltage level required by the processing module. In addition, the coupling module splits the output signal from the optical transceiver and passes the signal to both a high pass filter and a low pass filter that are connected in parallel. The outputs of the high pass filter and the low pass filter are then combined and provided to the processing module. The high pass filter and the low pass filter can be configured such that all frequencies of the signal from the optical transceiver are provided to the processing module.