Wavelength Selective Filter Using Interference and Reflection
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Solution Overview
Problem
The existing wavelength selective filters, particularly those using Fiber Bragg Grating elements, are costly to manufacture and sensitive to strain, leading to incorrect wavelength selection due to environmental changes, which can result in false detection of optical transmission line abnormalities.
Innovation Solution
A wavelength selective filter comprising an optical fiber collimator, an interference filter, and a reflective plate, where the interference filter is formed with a dielectric thin film on a glass substrate, and the reflective plate includes an optical attenuator, allowing for adjustable rotation of the interference filter to optimize wavelength selection properties, reducing manufacturing costs and environmental sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FBG elements are used for wavelength selection, then wavelength selectivity is achieved, but manufacturing cost increases and sensitivity to strain causes wavelength deviation
Solution Approach 1:
The patent replaces expensive FBG elements with a cost-effective interference filter assembly consisting of a glass substrate with dielectric thin films, reflective plates, and optical fibers. This substitution significantly reduces manufacturing cost while maintaining wavelength selection functionality through the interference filter's selective transmission and reflection properties.
Solution Approach 2:
The invention employs a composite structure combining glass substrate, dielectric thin films (high and low refractive index layers), reflective plates, and optical fibers. This composite approach enables wavelength selection through interference effects while reducing sensitivity to strain compared to FBG elements.
2Reliability
If FBG elements are used for wavelength selection, then wavelength filtering is achieved, but sensitivity to environmental changes causes false detection of abnormalities
Solution Approach 1:
By replacing strain-sensitive FBG elements with an interference filter assembly, the patent eliminates the harmful strain sensitivity that causes wavelength deviation. The interference filter structure with rigid glass substrate and fixed dielectric layers maintains stable wavelength selection under environmental variations, preventing false abnormality detections.
Solution Approach 2:
Instead of using FBG elements that reflect specific wavelengths through periodic refractive index variations (which are strain-sensitive), the patent inverts the approach by using interference filters that transmit specific wavelengths through constructive interference while reflecting others. This inverted mechanism with fixed geometric structure reduces sensitivity to strain and environmental changes.
3Measurement precision
If interference filter is rotated at predetermined angle, then wavelength selection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces angular orientation as a new dimension for wavelength control. By rotating the interference filter at a predetermined angle relative to the optical axis, the device achieves precise wavelength selection. This angular dimension complements the spectral dimension, enabling accurate wavelength filtering while maintaining a relatively simple physical structure.
Solution Approach 2:
The invention utilizes rotation angle as a controllable parameter to optimize wavelength selection. By adjusting the interference filter's rotational angle, the device fine-tunes the wavelength characteristics. This parameter change approach provides precise control without significantly increasing device complexity, as it involves simple rotational adjustment rather than complex mechanical mechanisms.
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 provides a cost-effective wavelength selective filter with improved stability and accuracy in selecting specific wavelengths, reducing the need for expensive FBG elements and minimizing false alarms due to environmental changes, thus enabling stable operation in optical communication networks.
Implementation Method 1
an interference filter, wherein two surfaces opposing each other with their xy-planes rotated about a y-axis at a predetermined rotation angle are defined as a light incident surface and a light emitting surface
Implementation Method 2
an interference filter, wherein two surfaces opposing each other with their xy-planes rotated about a y-axis at a predetermined rotation angle are defined as a light incident surface and a light emitting surface
Implementation Method 3
a reflective plate having a reflective surface on a front surface, the reflective plate being configured to reflect, toward the front side, light incident from the front side through the interference filter along the z-axis
Implementation Method 4
the optical fiber collimator is configured to cause the input light propagating through the optical fiber from the front side to be incident onto the interference filter, and converge the reflected light transmitted through the interference filter to the optical fiber
Data Source
AI summary
In a wavelength selective filter, an optical fiber collimator, an interference filter, and a reflective plate are arranged in this order from front to rear along a z-axis. The collimator has a collimator lens disposed on the rear side of an optical fiber that is opened. The interference filter includes light incident and emitting surfaces, opposed with their xy-planes rotated about a y-axis at a predetermined rotation angle. The reflective plate has a front reflective surface having a normal direction along a z-axis direction, and reflects, toward the front, light incident from the front through the interference filter, to be incident onto the interference filter. The optical fiber collimator causes the input light propagating through the optical fiber from the front to be incident onto the interference filter, and converges the reflected light transmitted through the interference filter to the optical fiber and outputs the light.