Optical Modulator Wiring Substrate for Low-Loss High-Frequency Drive
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Solution Overview
Problem
Existing optical modulators face challenges in maintaining high-frequency characteristics due to increased inductance from wire bonding, leading to transmission loss and noise susceptibility, especially when using differential signals for modulation.
Innovation Solution
The optical modulator design includes a wiring substrate that connects the driver circuit element and modulation electrode via flip-chip bonding, converting differential signals to single-ended signals and terminating the other signal, with heat radiation to minimize transmission loss and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect driver circuit element and modulation substrate, then electrical connection is achieved, but inductance increases and high-frequency characteristics deteriorate
Solution Approach 1:
The patent extracts and eliminates the wire bonding connection method that causes high inductance. Instead, it uses a printed circuit board (PCB) with trace wiring to directly connect the driver circuit element and modulation substrate, removing the harmful inductance component while maintaining electrical connection functionality.
Solution Approach 2:
The patent introduces a printed circuit board (PCB) as an intermediary carrier that provides low-inductance trace wiring connections between the driver circuit element and modulation substrate. This intermediary structure replaces the problematic wire bonding method and enables high-frequency signal transmission with minimal inductance.
2Reliability
If differential signal wiring is used to improve noise resistance, then signal quality improves, but wiring length increases and transmission loss increases
Solution Approach 1:
The patent uses a single-ended signal as a simplified copy or equivalent of the differential signal for high-frequency modulation applications. This single-ended signaling approach maintains the essential function of driving the modulation electrode while eliminating the need for long differential pair wiring, thus reducing transmission loss.
Solution Approach 2:
The patent changes the signal type parameter from differential signaling to single-ended signaling specifically for the high-frequency modulation path. This parameter change optimizes the wiring length and transmission characteristics for high-frequency operation while maintaining adequate noise resistance through proper grounding and shielding techniques.
3Volume of moving object
If miniaturization of modulation substrate is implemented, then device size reduces, but wiring design restrictions increase
Solution Approach 1:
The patent transitions from planar wiring layouts to three-dimensional vertical stacking architecture. The driver circuit element and modulation substrate are stacked vertically with direct PCB trace connections, enabling miniaturization while maintaining simple wiring design through the vertical integration approach.
Solution Approach 2:
The patent merges the driver circuit element and modulation substrate into a compact integrated assembly using PCB mounting. This merging approach reduces overall device size while simplifying wiring design by providing direct trace connections between components, eliminating the need for complex external wiring arrangements.
Data Source
AI summary
It is possible to provide an optical modulator in which a transmission loss from a driver circuit element to a modulation substrate is reduced. An optical modulator includes a modulation substrate (1) that includes an optical waveguide (200) and a modulation electrode (10) for modulating a light wave propagating through the optical waveguide, a driver circuit element (2) that generates a modulation signal to be applied to the modulation electrode (10), and a case (3) that accommodates the modulation substrate (1) and the driver circuit element (2), in which an output terminal (20′) that outputs the modulation signal is provided on an upper surface side of the driver circuit element (2), and a wiring substrate (4) including a wiring that electrically connects the output terminal (20′) and the modulation electrode (10) is disposed above the driver circuit element (2) and the modulation substrate (1) to straddle both the driver circuit element (2) and the modulation substrate (1).