Optical Transmitter Wire Layout for Stable Frequency Response
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Solution Overview
Problem
Conventional optical transmitters suffer from fluctuations in frequency response characteristics due to fabrication errors in wire length and require larger subcarrier sizes due to the presence of parasitic inductance and increased wire lengths.
Innovation Solution
The optical transmitter design integrates a terminating resistor on the RF wiring board, arranges the RF wiring board and ground pad to sandwich the modulated laser chip, and uses wires with lengths ranging from 0.5 to 1.5 mm or inductance of 0.4 to 1.2 nH, with an output optical waveguide emitting at a non-90 degree angle, and optionally includes a capacitor in series.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire length is extended to reduce parasitic inductance effect, then frequency response stability improves, but subcarrier size increases
Solution Approach 1:
The patent merges the terminating resistor with the RF wiring board by integrating it directly onto the board. This consolidation eliminates the need for separate wire connections between the resistor and the board, thereby reducing the overall wire length and parasitic inductance while maintaining frequency response stability without increasing subcarrier size.
Solution Approach 2:
The patent changes the spatial arrangement by placing the RF wiring board and ground pad to sandwich the modulated laser chip in the width direction. This dimensional reorganization optimizes the electric path geometry, reducing wire length and parasitic inductance effects while keeping the subcarrier compact.
2Reliability
If terminating resistor is separated from laser chip to reduce parasitic inductance, then frequency response characteristics improve, but subcarrier size increases
Solution Approach 1:
The terminating resistor is integrated directly onto the RF wiring board, merging multiple functions into a single component. This eliminates the need for separate wire connections and reduces parasitic inductance while maintaining compact subcarrier dimensions.
3Ease of manufacture
If parts are arranged side by side in width direction, then assembly simplicity improves, but subcarrier width increases
Solution Approach 1:
The patent reorganizes the spatial arrangement by placing the RF wiring board and ground pad to sandwich the modulated laser chip in the width direction rather than arranging all parts side by side. This dimensional change optimizes space utilization, reduces subcarrier width, and maintains manufacturing simplicity.
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 design significantly suppresses fluctuations in frequency response characteristics and reduces the subcarrier size by improving mounting yield and stability, achieving comparable or improved frequency bands with reduced width.
Implementation Method 1
an output optical waveguide of the modulated laser chip emits light at an angle of not 90 degrees to an emitting face of the modulated laser chip
Implementation Method 2
since a portion of the wire 10 that connects the EA modulator 5 and the terminating resistor 6 to each other has parasitic inductance (parasitic inductance) in accordance with a length of the wire 10
Data Source
AI summary
An optical transmitter capable of significantly suppressing a fluctuation in frequency response characteristics due to a fabrication error in internal wire length while reducing a subcarrier size of a module of the optical transmitter is provided. The optical transmitter includes a subcarrier on which an RF wiring board, a modulated laser chip, and a terminating resistor are mounted. A ground pad is on an upper surface of the subcarrier. A wire electrically connects at least the RF wiring board and the modulated laser chip to each other. The RF wiring board and the modulated laser chip are arranged in a width direction of the subcarrier. A length of the wire in an electric path which starts at the RF wiring board, passes through the terminating resistor, and reaches the ground pad is 0.5 to 1.5 mm or has an inductance of 0.4 to 1.2 nH.