Elliptical Resonator Optical Filter for Compact Double Filtering
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Solution Overview
Problem
Optical filters with insufficient quality factors lead to increased phase noise, and coupling additional filters to enhance quality factor results in doubled space consumption, which is undesirable in space-constrained applications.
Innovation Solution
An optical filter design that includes an optical resonator optically coupled to a reflector, allowing an optical signal to be filtered twice within the same resonator without significantly increasing the filter's size, achieved by using a first optical waveguide, a second optical waveguide, and an optical reflector to reflect the filtered signal back into the resonator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If another filter is optically coupled to an output of the optical filter to increase the quality factor, then the quality factor is improved, but the space consumed by the combined filters practically doubles
Solution Approach 1:
The patent merges the function of a second filter into the existing optical filter structure by adding an optical reflector that redirects the filtered signal back through the same resonator. This combining approach achieves double filtering (improving quality factor) without requiring a separate physical filter, thus avoiding the space doubling problem
Solution Approach 2:
The optical reflector acts as an intermediary element that takes the filtered optical signal from the output port and redirects it back into the resonator. This mediator enables the signal to undergo filtering again without requiring additional filter components, resolving the contradiction between quality factor improvement and space consumption
2Reliability
If the quality factor of the optical filter is increased, then the phase noise is reduced, but the filter size increases
Solution Approach 1:
The patent combines multiple filtering operations within a single filter volume by using the optical reflector to recycle the optical path. The same resonator performs filtering multiple times, achieving enhanced phase noise reduction without proportionally increasing the filter's physical volume
Solution Approach 2:
The optical reflector creates a continuous filtering action by redirecting the output signal back through the resonator. This continuous useful action allows the same filter structure to perform repeated filtering, improving phase noise reduction while maintaining compact size
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 design reduces phase noise by about half while maintaining the filter's size, enabling accurate determination of rotation rates in devices like resonant fiber optical gyroscopes.
Implementation Method 1
an optical resonator including a first portion of a third surface and a second portion of the third surface
Implementation Method 2
an optical reflector optically coupled to the third port
Data Source
AI summary
An optical filter twice filters an optical signal. The optical filter includes a first optical waveguide, an elliptical optical resonator, and a second optical waveguide. The optical signal is coupled from an input/output port of the optical filter which is a port of the first optical waveguide. A portion of the optical signal is coupled through and filtered by the elliptical optical resonator. The filtered optical signal is emitted from another port of the optical filter which is a port of the second optical waveguide. A reflector reflects the filtered optical signal back into the other port. The filtered optical signal is coupled through and filtered by the elliptical optical resonator to the input/output port. A twice filtered optical signal is emitted from the input/output port.