Scanning Spectral Filter Layout for Optical Ghost Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Grating-based optical spectrum analyzers suffer from optical ghosts, which are spurious spectral features generated at different spectral locations from the main signals, especially in compact designs, complicating accurate wavelength measurement.
Innovation Solution
Implementing a tunable spectral filter that synchronizes with the scanning spectral window of the OSA, using band-pass, low-pass, or high-pass filters to eliminate optical ghosts by filtering out secondary paths before they reach the detection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a grating-based optical spectrum analyzer is used, then spectral analysis capability is provided, but optical ghosts appear as spurious spectral features
Solution Approach 1:
The patent extracts and removes the harmful optical ghosts from the optical path by introducing a spectral filter that selectively blocks ghost wavelengths while allowing main signal wavelengths to pass through. This separates the harmful spectral components from the useful signal path.
Solution Approach 2:
The patent introduces a spectral filter as an intermediary component between the diffraction grating and the detector. This mediator selectively transmits or blocks specific wavelengths, preventing optical ghosts from reaching the detector while maintaining the integrity of the main spectral signal.
2Volume of moving object
If the OSA is made compact, then device size is reduced, but optical ghost elimination becomes more challenging
Solution Approach 1:
The patent combines the spectral filtering function with the existing spectral analysis function in a unified optical path. The spectral filter is integrated into the compact OSA design, merging ghost elimination with wavelength selection without requiring separate bulky elimination subsystems.
Solution Approach 2:
The patent changes the spectral transmission parameters of the optical path by introducing a tunable spectral filter. This filter dynamically adjusts its transmission characteristics to block ghost wavelengths while maintaining transmission of main signal wavelengths, enabling effective ghost elimination in a compact form factor.
3Volume of moving object
If propagation paths are shortened for compact design, then device size is reduced, but stray light reflections increase
Solution Approach 1:
The patent extracts stray light reflections from the optical path by using a spectral filter to identify and block reflected ghost wavelengths. Even though propagation paths are shortened, the filter removes the harmful stray light components before they can interfere with the detection.
Solution Approach 2:
The patent converts the potentially harmful stray light reflections into identifiable spectral features that can be filtered. By understanding the spectral characteristics of the stray light, the system uses the spectral filter to selectively block these reflections, turning a design challenge into a manageable filtering problem.
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 or eliminates optical ghosts without compromising the optical performance, allowing for a smaller OSA form factor by shortening propagation paths and reducing stray light reflections.
Implementation Method 1
a spectral filter to transmit or block specific wavelengths
Implementation Method 2
grating-based optical spectrum analyzers
Data Source
AI summary
A monochromator apparatus in a grating-based optical spectrum analyzer (OSA) includes a diffraction grating element, a reflector element, and a tunable spectral filter. The tunable spectral filter may be placed in a ghost signal path between the diffraction grating element and the reflector element, or between the diffraction grating element and an output element to prevent an optical ghost signal from passing to the output element. The tunable spectral filter may include a band-pass filter, a low-pass filter, a high-pass filter, or a linear variable filter. A spectral window of the tunable spectral filter may move synchronously with a scanning spectral window of the OSA to reduce or eliminate the optical ghost signal.