Single Fiber Bidirectional Optical Module Noise Isolation
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Solution Overview
Problem
Conventional bidirectional optical modules suffer from forward radiated noise, LD/PD crosstalk, and outer noise due to the integration of laser diodes and photodiodes in metal packages, which increases component count and costs, and generates electromagnetic interference.
Innovation Solution
A single-fiber bidirectional optical module design where the metal chassis is insulated from the receptacle using an insulative pipe, with separate grounds for the transmitter and receiver to prevent electromagnetic interference, and the LD pins are floated from the chassis to prevent antenna effects, while the receptacle is isolated from the chassis using zirconia insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the LD and PD are integrated in a metal package, then the component count is reduced and cost is lowered, but electromagnetic noise and LD/PD crosstalk increase
Solution Approach 1:
The patent divides the grounding system into two separate grounds: a FG (frame ground) connected to the metal package and an RG (receiver ground) connected to the receiver circuitry. This segmentation prevents the LD driving current from coupling into the PD through the ground path, thereby reducing electromagnetic noise and LD/PD crosstalk while maintaining component integration
Solution Approach 2:
The patent introduces an insulating structure (such as an insulating layer or insulating stand-off) between the LD anode and the metal package to prevent direct electrical connection. This intermediary blocks the electromagnetic noise and driving current from coupling into the package, reducing harmful electromagnetic radiation while allowing the LD and PD to remain integrated
2Device complexity
If the LD driving current flows through the metal package, then the structure is simplified, but forward radiated noise increases
Solution Approach 1:
The patent introduces an insulating structure between the LD anode and the metal package to prevent direct electrical connection. This intermediary blocks the electromagnetic noise and driving current from coupling into the package, reducing harmful electromagnetic radiation while maintaining structural simplicity
Solution Approach 2:
The patent extracts the harmful electrical connection between the LD driving current and the metal package by implementing electrical isolation. This removes the source of forward radiated noise while preserving the structural benefits of integration
3Device complexity
If the LD and PD are connected through the same ground, then the circuit is simplified, but LD/PD crosstalk increases
Solution Approach 1:
The patent divides the grounding system into two separate grounds: FG (frame ground) connected to the metal package and RG (receiver ground) connected to the receiver circuitry. This segmentation prevents the LD driving current from coupling into the PD through the ground path, thereby reducing electromagnetic noise and LD/PD crosstalk while maintaining component integration
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 design reduces electrical and electromagnetic crosstalk between the LD and PD, suppresses forward radiated noise, and minimizes the impact of outer noise on the receiver, enhancing the module's performance and cost-effectiveness by integrating components without increasing noise interference.
Implementation Method 1
an insulative pipe connects a metal chassis including a transmitter and a receiver to a receptacle for removing an optical fiber. Thereby, the receptacle and the chassis are insulated from each other
Implementation Method 2
As a powerful driving current of the LD generates electromagnetic waves, intense radio waves are generated with the container acting as an antenna
Implementation Method 3
a bidirectional optical module including a transmitter, a receiver, and a receptacle for bidirectionally transmitting a signal through a single optical fiber
Data Source
AI summary
A metal chassis including a laser diode (LD) and a photodiode (PD) is held at a receiver ground RG, which is the potential of the anode or the cathode of the PD. Meanwhile, a receptacle for removing an optical fiber is held at a frame ground FG of a separate frame. Lead pins of the LD are insulated from the metal chassis. The receiver ground RG and the frame ground FG are insulated from each other by an insulative member. Since the receiver ground RG is insulated from the LD and the frame, a receiver is not easily affected by inner noise and outer noise. Accordingly, a bidirectional optical module having reduced influence of forward radiated noise, LD/PD crosstalk, and the outer noise is provided.