Tri-plexer Optical Subassembly for CATV Signal Isolation
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Solution Overview
Problem
Current optical modules in CATV systems are inadequate for handling three types of optical signals, specifically requiring a configuration that can transmit digital signals at 1.31 μm and 1.48 μm wavelengths and an analog signal at 1.55 μm wavelength, while maintaining electrical isolation between analog and digital circuits to reduce crosstalk and noise.
Innovation Solution
An optical module with a tri-plexer optical subassembly, comprising an analog module, a bi-directional module with semiconductor light-receiving and transmitting devices, and a WDM filter, where the analog module receives the 1.55 μm signal, and the bi-directional module handles the 1.48 μm and 1.3 μm signals, with a ground plate for electrical isolation and heat dissipation, ensuring the analog and digital circuits are electrically isolated and thermally stable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three types of optical signals are handled in a single optical module, then the functionality and versatility are improved, but the device complexity increases
Solution Approach 1:
The optical module is divided into distinct functional sub-assemblies: a bi-directional module handling digital signals and an analog module handling video signals. These modules are electrically isolated from each other, allowing independent optimization and reducing overall system complexity while maintaining multi-functionality.
Solution Approach 2:
The bi-directional module is designed to handle both upstream and downstream digital optical signals through integrated semiconductor light-receiving and light-transmitting devices. This multi-functional design reduces the total number of components needed while achieving the required versatility.
2Volume of moving object
If analog and digital circuits are integrated in the same module, then the compactness is improved, but the crosstalk and noise increase
Solution Approach 1:
The module is segmented into electrically isolated analog and digital sections. The bi-directional module and analog module are separated with independent electrical connections, preventing crosstalk and noise while maintaining physical compactness through integrated packaging.
3Device complexity
If semiconductor light-receiving and light-transmitting devices are housed in a single package, then the device complexity is reduced, but the heat dissipation becomes more difficult
Solution Approach 1:
A ground plate is introduced as a thermal intermediary between the semiconductor devices and the external environment. This ground plate provides a dedicated heat dissipation path that separates thermal management from electrical connections, allowing efficient heat removal while maintaining the integrated package structure.
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 effectively reduces crosstalk and noise, improving bit error rates and noise power spectrum, enabling efficient transmission of digital signals up to 2.5 Gbps and analog signals with reduced electromagnetic interference.
Implementation Method 1
The WDM filter discriminates the optical signal with the wavelength of 1.55 μm from the other optical signals with wavelengths of 1.48 μm and 1.31 μm, respectively
Implementation Method 2
The ground plate is fixed to the bi-directional module and to the printed circuit board... (3) supporting the rear portion of the tri-plexer optical subassembly with respect to the printed circuit board; and (4) dissipating heat generated in the bi-directional module directly to the printed circuit board
Data Source
AI summary
An optical module that implements with a tri-plexer assembly is disclosed. The tri-plexer module comprises a bi-directional module for transmitting digital input and output signals and an analogue optical assembly for receiving analog optical signals. The bi-directional module installs both a light-emitting device and a light-receiving device in a signal package. The analogue optical assembly is assembled such that the optical axis thereof makes a substantially right angle with the optical axis of the bi-directional module. The signal ground of the module is common to the analogue module and to a section for receiving the digital data; while, the chassis ground or the frame ground in the module is isolated from the signal ground.