Optical Waveguide Relay Line With Gradual Impedance Matching
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Solution Overview
Problem
Optical waveguide elements face impedance mismatch issues between modulation electrodes and external signal lines, leading to signal reflection and attenuation, which existing solutions like resistors or filters fail to fully address.
Innovation Solution
An optical waveguide element module with a relay line on a substrate, where the impedance varies stepwise or consecutively to connect the connector to the modulation electrode, using a coplanar line configuration with adjustable electrode gaps and dielectric constant changes to suppress signal reflection and attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is disposed in the relay substrate to adjust impedance, then impedance mismatch is reduced, but signal attenuation increases
Solution Approach 1:
The patent changes the impedance parameter of the relay line from a fixed value to a variable value that varies stepwise or consecutively along the signal path. This allows the impedance to be optimized at different positions to match both the external signal line (50Ω) and the modulation electrode (40Ω) without using resistive elements that cause signal attenuation.
Solution Approach 2:
The relay line is divided into multiple segments with different impedance values. By segmenting the transmission path and assigning different impedance characteristics to each segment, the patent creates a gradual transition that reduces reflection and improves impedance matching without energy loss from resistors.
2Reliability
If the impedance of the modulation electrode is changed to match the external signal line, then signal reflection is reduced, but the electro-optical conversion efficiency is degraded
Solution Approach 1:
The patent introduces a relay line as an intermediary transmission path between the external signal line and the modulation electrode. This intermediary structure with varying impedance serves as a bridge that allows the modulation electrode to maintain its optimal 40Ω impedance for electro-optical conversion while the external interface maintains 50Ω impedance, thus resolving the conflict between signal transmission efficiency and conversion efficiency.
3Reliability
If a filter circuit is mounted on the relay substrate to improve frequency response, then electro-optical conversion response becomes flat, but device complexity increases
Solution Approach 1:
The relay line with varying impedance serves multiple functions simultaneously: it provides impedance matching between different impedance levels, reduces signal reflection, and improves frequency response characteristics. This multi-functionality eliminates the need for separate filter circuits, thereby improving frequency response without increasing device complexity.
Data Source
AI summary
Provided is an optical waveguide element module which suppresses reflection of a modulation signal and attenuation of a modulation signal, even when an impedance of a modulation electrode of an optical waveguide element and an impedance of a transmission line for inputting the modulation signal from the external of the optical waveguide element are different from each other. The optical waveguide element module is provided with an optical waveguide element, which has a substrate (1) composed of a material having electro-optical effects, an optical waveguide (2) formed on the substrate, and a modulation electrode (3) which modules optical waves propagating in the optical waveguide; a connector (8), wherein an external signal line which inputs the modulation signal to the modulation electrode is connected to the modulation electrode; and a relay line which connects the connector and the modulation electrode and is formed on a relay substrate (7). Impedance of the relay line changes stepwise or continuously, and reflection of the modulation signal in the optical waveguide element module is suppressed.