Optical Module Impedance Matching Resistor
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Solution Overview
Problem
Conventional optical modules for radio over fiber (ROF) technology face challenges in impedance matching, leading to signal loss and limited bandwidth, requiring additional trimming processes and larger module sizes due to the use of open stubs and separate bias tees, which are inefficient and difficult to adjust.
Innovation Solution
An optical module design incorporating a microstrip signal line with a filter and a separately disposed resistor for impedance matching, eliminating the need for additional trimming and bias tees, allowing for efficient delivery of RF signals across a wide frequency band without loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If open stubs are used for impedance matching in conventional optical modules, then impedance matching can be achieved at a specific frequency, but the bandwidth is limited and additional trimming processes are required
Solution Approach 1:
The patent changes the impedance matching approach from using open stubs with specific geometric parameters (requiring trimming) to using a resistor with a specific resistance value (50Ω) that provides broadband impedance matching without requiring additional trimming processes, thus resolving the contradiction between manufacturing precision and bandwidth
2Manufacturing precision
If open stubs are trimmed to match impedance, then impedance matching is improved, but the module requires additional processes and the operating frequency band cannot be adjusted
Solution Approach 1:
The patent extracts the trimming process from the manufacturing flow by using a resistor-based impedance matching solution that does not require post-fabrication trimming, thereby simplifying the fabrication process while maintaining impedance matching capability
Solution Approach 2:
The patent uses a simple resistor component for impedance matching instead of complex trimmed stub structures, making the solution easier to manufacture and more adaptable to frequency changes
3Ease of operation
If bias tee is added to supply bias voltage separately, then bias voltage can be supplied to optical device, but the module size increases
Solution Approach 1:
The patent merges the bias voltage supply function with the existing signal line structure by using the same ground reference and integrating the bias tee functionality into the existing layout, thereby supplying bias voltage without significantly increasing module size
Data Source
AI summary
Provided is an optical module used in a communication system employing a radio over fiber (ROF) technology delivering a radio frequency (RF) signal through an optical fiber. The optical module includes: an optical device; a signal line for transporting a radio frequency (RF) signal input from an external circuit to the optical device; and a resistor separately disposed from the signal line and having one end connected with the optical device, wherein the input impedance seen from the signal line is matched by the resistor. A bias voltage supplied to operate the optical device is applied through an inductor connected to the signal line between the optical device and a filter. Here, the filter formed by a pattern of the signal line prevents the bias voltage from being supplied to the external circuit. In order to amplify the RF signal input from the external circuit, an amplifier may be connected between the external circuit and the filter.