Optical Receiver Bias Pad Resistor Layout for Resonance Suppression
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Solution Overview
Problem
High-speed optical receiver modules face challenges in maintaining high-quality transmission characteristics, particularly at speeds of 25 Gbps, 40 Gbps, or 50 Gbps, due to resonance issues caused by the insertion of resistance elements in series with signal lines, which leads to cutoff frequency drops and signal deterioration.
Innovation Solution
Incorporating a thin film resistor in parallel with the bias pad, positioned on the carrier or light receiving element, with a higher resistance value than the bias pad, to suppress resonance and noise, thereby maintaining a flat transmission characteristic across the frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistance thin film or resistance element is inserted in series between signal lines to suppress resonance and flatten transmission characteristic, then transmission characteristic quality is improved, but cutoff frequency drops due to CR time constant
Solution Approach 1:
Instead of inserting resistance in series with signal lines (conventional approach), the patent connects resistance in parallel to the bias pad. This inverted configuration allows resistance to suppress resonance without being part of the signal path, thereby avoiding cutoff frequency reduction while still improving transmission characteristic quality.
2Reliability
If resistance is added to suppress resonance and reduce peaking/dipping, then transmission characteristic flatness is improved, but high-frequency signal transmission is attenuated
Solution Approach 1:
The resistance element acts as an intermediary connected to the bias pad rather than directly to signal lines. It provides resonance suppression functionality while being electrically isolated from the high-frequency signal path, thus eliminating harmful high-frequency attenuation while maintaining transmission flatness.
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
The solution effectively reduces peaking and dipping, ensuring a high-quality transmission characteristic by attenuating high-frequency signals and reducing resonance, thus enhancing the performance of optical receiver modules in high-speed applications.
Implementation Method 1
resonance causing malfunction is suppressed
Implementation Method 2
electric resistance of the thin film resistor is larger than electric resistance of the bias pad
Implementation Method 3
a light signal input through a fiber is converted into an electric signal through an absorption layer (light receiving portion) of the light receiving element by photoelectric conversion
Data Source
AI summary
An optical receiver module includes a light receiving element that converts a received light signal into an electric signal, a bias pad supplied with a bias power. The bias pad is included in the light receiving element and/or a carrier on which the light receiving element is mounted. The optical receiver module also includes a thin film resistor arranged in contact with the bias pad so as to connect in parallel to the bias pad. An electric resistance of the thin film resistor is larger than an electric resistance of the bias pad. The optical receiver module further includes an amplifier that amplifies the electric signal.