Light Modulator Bias Control via Segmented Waveguide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In thin substrate light modulators, out-phase interfering light is not easily separated from the main output waveguide, leading to biased control issues and degradation of modulation signal quality due to incorporation of radiated light with main output, causing phase difference and wavelength dependency problems.
Innovation Solution
A light modulator with a Mach-Zehnder waveguide and monitoring means, incorporating a leaked light-removing means such as a slab waveguide or light-absorbing material to remove radiated light from the output waveguide, ensuring accurate bias control by maintaining appropriate relationships between main and monitor output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin substrate (20 μm or less) is used to improve modulation characteristics, then modulation performance is improved, but out-phase interfering light cannot be easily separated from the main output waveguide
Solution Approach 1:
The output waveguide is divided into two functional segments: a first output waveguide for transmitting the main signal light, and a second output waveguide for extracting and monitoring the out-phase interfering light (radiated light). This segmentation allows the harmful radiated light to be separated and utilized for bias monitoring without degrading the main signal transmission.
Solution Approach 2:
The patent introduces an intermediary structure (the second output waveguide) that mediates between the thin substrate waveguide and the monitoring function. This intermediary allows the radiated light to be extracted and directed to a monitor photodetector, enabling bias control without directly affecting the main signal path.
2Ease of operation
If radiated light is incorporated into main output light for monitoring, then bias control is enabled, but phase difference characteristics are significantly changed and bias points shift
Solution Approach 1:
The monitoring function is segmented into a separate second output waveguide that extracts radiated light independently from the main signal path. This allows the monitor to detect bias conditions without the incorporated radiated light affecting the main output's phase characteristics, maintaining measurement precision while enabling ease of operation.
Solution Approach 2:
The second output waveguide acts as an intermediary that provides monitoring capability without allowing radiated light to contaminate the main output signal. This intermediary structure enables bias control through separate monitoring while preserving the integrity of the main signal's phase characteristics.
3Object-generated harmful factors
If three branch structure or guide for out-phase interfering light is used to separate radiated light, then separation capability is improved, but fine radiated light remains in the vicinity of the output waveguide
Solution Approach 1:
The waveguide structure is segmented into distinct first and second output waveguides, with the second specifically designed to extract and channel radiated light away from the main output path. This segmentation ensures that fine radiated light is completely removed from the vicinity of the main output waveguide, preventing any residual contamination.
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 enables highly accurate bias control by effectively removing radiated light, stabilizing bias points against temperature and wavelength changes, and maintaining high-quality modulation signal output.
Implementation Method 1
an optical waveguide which guides signal light from a multiplexing portion of the Mach-Zehnder waveguide and outputs the signal light outside the substrate
Implementation Method 2
leaked light-removing means for removing some of the radiated light propagating through the output waveguide from the output waveguide
Data Source
AI summary
An object is to provide a light modulator capable of highly accurate bias control by maintaining main output characteristics and monitor characteristics in an appropriate relationship and matching a bias point determined using monitor output and an optimal bias point of main output. The light modulator includes an optical waveguide formed in a substrate having a thickness of 20 μm or less, in which the optical waveguide includes a Mach-Zehnder waveguide and an output waveguide for guiding signal light from a multiplexing portion of the Mach-Zehnder waveguide and outputting the signal light outside the substrate and monitoring means that monitors signal light or radiated light. Leaked light-removing means for removing some of the radiated light propagating through the output waveguide from the output waveguide and emitting the radiated light outside the substrate is provided in the light modulator.