Optical Transmission Module Lead Pin and Ground Configuration
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Solution Overview
Problem
The CAN-package-type optical transmission module faces challenges in size reduction due to increased lead pins with multiple EML elements, complex manufacturing, and unstable signal impedance, particularly with the GND not located at the outermost coaxial layer.
Innovation Solution
The optical transmission module features a metal stem with a plate shape, a block, a sub-mount for semiconductor lasers, and a cap with lead pins penetrating through holes in the stem, allowing single-phase electrical signals to be applied directly for modulation and oscillation, reducing the number of lead pins and stabilizing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple EML elements are provided in one CAN package to output laser beams with multiple wavelengths, then the functionality is improved, but the number of lead pins increases, hampering size reduction of the module
Solution Approach 1:
Multiple EML elements are integrated into a single CAN package with shared lead pin structures. The patent combines multiple semiconductor lasers and their control circuits into one compact module, reducing the total number of lead pins required compared to separate packages for each wavelength.
Solution Approach 2:
The CAN package is designed as a universal platform that can accommodate multiple EML elements with different wavelengths through a single set of lead pins. The package structure and control circuit are configured to support multiple functions (multiple wavelengths) through a unified interface.
2Device complexity
If wires for connection with power supply and control signal are provided coaxially at one lead pin, then the number of lead pins is decreased, but the GND wire cannot be electrically connected directly to the package, causing impedance variation and unstable characteristics
Solution Approach 1:
A ground connection structure is introduced as an intermediary element that provides a direct electrical path from the GND wire to the package body. This mediator resolves the impedance issue by creating a dedicated reference potential path without requiring additional external lead pins.
Solution Approach 2:
The ground connection is established through a different spatial dimension - using the package body and internal structures as the return path rather than relying on the outermost coaxial layer. This dimensional approach allows GND connection without increasing lead pin count.
3Reliability
If a multilayer coaxial structure is formed for the lead pin, then the electrical connection capability is improved, but the manufacturing becomes complicated and cost increases
Solution Approach 1:
The patent adopts a simpler, more cost-effective lead pin structure that sacrifices some of the complexity of multilayer coaxial designs in favor of easier manufacturing. The design uses practical, manufacturable structures that achieve sufficient electrical performance without the high cost and complexity of precision multilayer coaxial construction.
Data Source
AI summary
This optical transmission module includes: a plurality of semiconductor lasers provided on a sub-mount fixed to a side surface of a block fixed on a plate-shaped stem made of metal; and a cap with a lens fixed thereto, the cap covering all members placed above the stem. The same number of lead pins as the semiconductor lasers are provided so as to respectively penetrate through a plurality of holes formed in the stem. The lead pins and the semiconductor lasers are electrically connected to each other, respectively. Single-phase electrical signals with the stem as a ground potential are respectively applied to the semiconductor lasers from an external power supply, through the lead pins, respectively, so as to cause modulation and oscillation of the semiconductor lasers.