Optical Module Capacitor Placement for High Frequency
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Solution Overview
Problem
In digital coherent systems, the direct optical connection between a lens and a photodiode (PD) increases the length of electric wiring between the PD and a capacitor, leading to deteriorated high-frequency characteristics.
Innovation Solution
An optical module configuration where a spacer is used to maintain a predetermined distance between the optical transmission path and the PD, with the capacitor electrically connected to the PD and positioned on the same side as the PD on the spacer, thereby shortening the electric wiring length and improving high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a lens and a PD are optically and directly connected to each other to miniaturize the optical system, then the optical system size is reduced, but the length of electric wiring between the capacitor and PD increases causing high frequency characteristics to deteriorate
Solution Approach 1:
The capacitor is disposed on the same side as the PD on the spacer surface, utilizing the two-dimensional space available on the spacer rather than being constrained to a linear arrangement. This dimensional reconfiguration allows the capacitor to be positioned close to the PD without increasing the optical path length or requiring additional wiring distance, thus maintaining high frequency characteristics while achieving optical system miniaturization.
2Reliability
If the capacitor is disposed far from the PD to maintain stable impedance, then high frequency characteristics are improved, but the optical system cannot be miniaturized
Solution Approach 1:
The capacitor and PD are merged onto the same spacer structure, with the capacitor disposed on the same side as the PD on the spacer surface. This integration allows both components to be positioned in close proximity without requiring separate mounting areas or additional wiring paths, enabling miniaturization of the optical system while maintaining the electrical connection stability needed for high frequency operation.
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 configuration reduces the impedance of the wiring, stabilizes high-frequency operations, and efficiently removes AC noise, enhancing the overall performance of the light receiving element.
Implementation Method 1
a high-speed optical signal is converted by photoelectric conversion with a light receiving element
Data Source
AI summary
To shorten the length of an electric wiring between a capacitor and a PD, and to improve high frequency characteristics. An optical module of the present invention includes a light receiving element disposed at such a position that light from an optical transmission path is received on a light receiving surface in a state that the light receiving surface faces the optical transmission path; a spacer jointed to the optical transmission path and to the light receiving element in such a manner that a gap between the optical transmission path and the light receiving element is kept at a predetermined distance that light from the optical transmission path is allowed to enter the light receiving surface; and a capacitor electrically connected to the light receiving element, and disposed along with the light receiving element on a surface of the spacer on the same side as that joined to the light receiving element.