Optical Modulator Bias Shift Compensation via Light Intensity Ratio Adjustment
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Solution Overview
Problem
Existing optical modulators face challenges in accurately adjusting the bias point for multi-level modulation formats like DQPSK, leading to bias shifts and reduced signal quality due to phase differences and mixing of unnecessary lights, especially in thin-plate structures, which complicates the structure and increases component size and cost.
Innovation Solution
An optical modulator design that includes a Mach-Zehnder type optical waveguide with light collecting means and light intensity ratio adjusting mechanisms, allowing for the simultaneous reception of two radiated lights by a single optical receiving element, which compensates for bias shifts and improves monitoring characteristics by adjusting the light intensity ratio and positioning of the optical receiving element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single optical receiving element is used to detect monitoring light, then device complexity is reduced, but measurement precision deteriorates due to bias shifts and phase differences in multi-level modulation formats
Solution Approach 1:
The patent divides the monitoring light detection into two separate detection paths: one for ON light and another for OFF light. Each path has its own optical receiving element, allowing independent optimization of detection parameters and eliminating bias shifts that occur when using a single receiving element for both types of light.
Solution Approach 2:
The patent introduces a beam splitter and optical switch as intermediary components to selectively direct ON light and OFF light to appropriate receiving elements. This intermediary system enables precise separation of detection paths while maintaining a compact overall structure.
2Measurement precision
If two OFF lights are used for monitoring, then measurement precision improves for bias control, but device complexity increases due to additional optical components and alignment requirements
Solution Approach 1:
The patent merges the detection of ON light and OFF light into a unified monitoring system where both light types are processed through shared optical components. The beam splitter and optical switch serve dual purposes, reducing the total number of components while maintaining precise monitoring capability.
Solution Approach 2:
The optical receiving elements are designed to be universal, capable of detecting both ON light and OFF light through the beam splitter configuration. This multi-functionality eliminates the need for separate dedicated receiving elements for each light type, reducing device complexity.
3Measurement precision
If light collecting means is added to collect radiated lights, then measurement precision improves for monitoring, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The beam splitter and optical switch components are designed to automatically separate and direct ON light and OFF light based on their inherent optical properties (phase and intensity differences). This self-service mechanism eliminates the need for complex manual alignment procedures during assembly, simplifying manufacturing while maintaining precise light collection.
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 enables precise bias control with reduced component size and cost, enhancing the monitoring output's accuracy and frequency responsiveness by compensating for bias shifts and optimizing the light intensity ratio, thus maintaining high signal quality.
Implementation Method 1
a substrate (1) that has an electro-optical effect
Implementation Method 2
an optical receiving element (5)
Data Source
AI summary
An optical modulator is provided which can compensate for a bias shift between an output light and a monitoring light of the optical modulator and which has a configuration capable of being reduced in size with a simple structure. The optical modulator comprises a substrate that has an electro-optical effect, an optical waveguide that includes a Mach-Zehnder type optical waveguide formed in the substrate, a modulation electrode that modulates light waves propagating in the optical waveguide, an optical fiber that guides an output light from the optical waveguide, light collecting means for collecting two radiated lights from the Mach-Zehnder type optical waveguide toward a single optical receiving element, and light intensity ratio adjusting means for adjusting a light intensity ratio of the two radiated lights received by the optical receiving element.