Wavelength Meter Using Asymmetric Interferometers for Temperature-Independent Measurement
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Solution Overview
Problem
Existing wavelength meters face challenges in accurately measuring the wavelength of optical signals, particularly in tunable lasers, due to stability and temperature dependence issues, requiring control to differentiate wavelength changes from temperature changes.
Innovation Solution
The use of two asymmetric Mach-Zehnder interferometers with different thermo-optic properties, allowing for wavelength determination independent of temperature, by configuring at least one arm of the second interferometer to have a different thermo-optic coefficient and group index ratio than the first interferometer, and optionally incorporating a third interferometer with shorter arms for enhanced measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature control is implemented to differentiate wavelength changes from temperature changes, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs two Mach-Zehnder interferometers with asymmetric arm configurations. The first interferometer has arms with different lengths, and the second interferometer has arms with different lengths in a non-symmetric arrangement. This asymmetry creates distinct temperature response characteristics for each interferometer, allowing the system to differentiate between wavelength changes and temperature changes through mathematical processing of the two output signals, thereby eliminating the need for active temperature control while maintaining measurement precision
Solution Approach 2:
The patent changes the physical parameters of the interferometer arms by configuring them with different length differences. Specifically, the first interferometer has a path length difference of ΔL1 between its arms, while the second interferometer has a different path length difference of ΔL2. This parameter variation creates different sensitivity responses to temperature changes, enabling the system to decouple wavelength and temperature effects through signal processing without requiring active temperature stabilization
2Reliability
If multiple interferometers with different configurations are used, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent uses two Mach-Zehnder interferometers with asymmetric arm configurations where the path length differences are deliberately made different (ΔL1 ≠ ΔL2). This asymmetric design ensures that each interferometer responds differently to the same optical signal, providing redundant but independent measurement data that enhances reliability through diversity while maintaining a relatively simple integrated structure
Solution Approach 2:
The patent implements a multi-functional interferometer system where two interferometers serve multiple purposes: they simultaneously measure wavelength, provide temperature compensation, and enable determination of optical signal characteristics such as linewidth and coherence length. This universal approach increases reliability by making the system capable of multiple measurements without proportionally increasing complexity, as the same hardware structure performs multiple functions
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 approach enables accurate and temperature-independent wavelength measurement, eliminating the need for temperature control and providing a robust, stable solution for wavelength determination, while also allowing for linewidth and coherence measurement.
Implementation Method 1
a first interferometer means for receiving the optical signal from the input means and outputting a first output signal, the first interferometer means comprising a first reference arm and a first delay arm
Implementation Method 2
at least one of the second reference and the second delay arms of the second interferometer means being configured to have a different thermo-optic property than the corresponding first reference arm and the first delay arm of the first interferometer means
Data Source
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AI summary
An apparatus is disclosed, comprising an input means for receiving an optical signal from an optical source. The apparatus may also comprise a first interferometer means for receiving the optical signal from the input means and outputting a first output signal, the first interferometer means comprising a first reference arm and a first delay arm and a second interferometer means for simultaneously receiving the optical signal from the input means and outputting a second output signal, the second interferometer means comprising a second reference arm and a second delay arm. At least one of the second reference and the second delay arms of the second interferometer means being configured to have a different thermo-optic property than the corresponding first reference and the first delay arm of the first interferometer means. The apparatus may also comprise means for determining a wavelength of the optical signal based on the first and second output signals.