Optical Module Stem Restriction Body for Thermal Tracking Error
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Solution Overview
Problem
The TO-CAN-type optical module packages face increased assembly costs due to the need for precise lens positioning to reduce tracking error, and the use of a plastic plate within the package can elongate the optical axis direction, complicating thermal management and efficiency.
Innovation Solution
Incorporating a restriction body with a linear thermal expansion coefficient smaller than the stem, either attached to the second surface or positioned closer to it, to sandwich the stem between the thermoelectric cooler and the restriction body, thereby reducing thermal deformation and tracking error at a lower cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional lens is provided between the semiconductor laser element and the lens to generate collimated light, then tracking error is reduced, but assembly cost increases due to the need for accurate lens positioning
Solution Approach 1:
The invention changes the thermal expansion parameter by introducing a restriction body made of material with a linear thermal expansion coefficient smaller than that of the stem. This parameter change compensates for thermal deformation without requiring additional optical components or precise positioning, thereby reducing tracking error while maintaining low assembly cost
Solution Approach 2:
The invention uses a simple restriction body (a basic structural component) instead of complex optical components like additional lenses. This inexpensive component effectively addresses the tracking error problem without increasing assembly cost, embodying the principle of using simple, cheap objects to solve problems
2Reliability
If a plastic plate is provided between the semiconductor laser element and the lens, then tracking error is reduced, but the package length in the optical axis direction increases
Solution Approach 1:
The invention changes the thermal expansion parameter by using a restriction body with a linear thermal expansion coefficient smaller than that of the stem. This approach reduces tracking error without requiring additional space in the optical axis direction, thereby maintaining a compact package length
Solution Approach 2:
Instead of adding components along the optical axis direction (lengthening the package), the invention addresses tracking error by introducing a restriction body that acts in the thermal expansion dimension. This dimensional shift allows tracking error reduction without increasing package length
3Ease of manufacture
If the stem is made of cold milling steel with high thermal expansion, then ease of manufacture is improved, but thermal deformation increases causing tracking error
Solution Approach 1:
The invention applies local quality by introducing a restriction body with specific material properties (smaller linear thermal expansion coefficient) at the critical location where thermal deformation occurs. This localized solution maintains the ease of manufacturing the stem while compensating for its high thermal expansion特性 in the specific region affecting optical alignment
Solution Approach 2:
The invention creates a composite structure by combining the stem (cold milling steel) with a restriction body made of different material having smaller thermal expansion. This composite approach allows the stem to maintain its manufacturing advantages while the restriction body compensates for thermal deformation, reducing tracking error
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 effectively reduces tracking error by controlling thermal expansion, maintaining high-quality optical signal transmission while minimizing assembly costs and package length.
Implementation Method 1
a Peltier element configured to control the temperature of the semiconductor laser to be constant to stabilize characteristics
Implementation Method 2
The stem has a side surface in contact with an optical transceiver housing so that heat generated due to the operation of the TEC is released to the optical transceiver housing
Implementation Method 3
Front-surface light from the semiconductor laser element is condensed to an end face of an optical fiber through the lens
Data Source
AI summary
An optical module includes: a stem including a first surface and a second surface opposite to the first surface; a thermoelectric cooler including a heat-releasing substrate fixed to the first surface; a semiconductor laser element attached to the thermoelectric cooler; a cap fixed to the first surface and covering the thermoelectric cooler and the semiconductor laser element; a lens fixed to the cap; and a restriction body fixed to the second surface. The linear thermal expansion coefficients of the heat-releasing substrate and the restriction body are smaller than the linear thermal expansion coefficient of the stem.