PIC Optical Wavemeter Using Dual MZI Interferometers
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Solution Overview
Problem
Existing optical wavemeters based on bulk optical components are expensive, space-consuming, and have limited update rates, while photonic integrated circuit (PIC) wavemeters have a short usable wavelength range and suffer from optical power losses and accuracy penalties due to birefringence.
Innovation Solution
A photonic integrated circuit (PIC) optical wavemeter design that uses a combination of optical splitters and Mach-Zehnder Interferometers (MZIs) with different free spectral ranges (FSRs) to accurately measure the wavelength of optical signals over a wide range, while avoiding polarization-related accuracy penalties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bulk optical components are used for wavemeter construction, then measurement accuracy can be achieved, but device size and cost increase significantly
Solution Approach 1:
The patent replaces bulk mechanical optical components with a photonic integrated circuit (PIC) based system. The PIC integrates multiple optical functions (interferometers, waveguides, couplers) onto a single chip, eliminating the need for large-scale mechanical assembly while maintaining measurement accuracy through precise optical path control within the integrated structure.
Solution Approach 2:
The patent combines multiple optical functions (multiple interferometers, waveguides, couplers, and detection elements) into a single integrated photonic chip. This merging of previously separate bulk optical components into one compact unit achieves both size reduction and functional integration while preserving measurement capabilities.
2Area of stationary object
If photonic integrated circuit wavemeters are used, then device size is reduced, but usable wavelength range becomes limited
Solution Approach 1:
The patent divides the wavelength measurement function across multiple interferometer units with different free spectral ranges (FSRs). Each interferometer segment handles a specific wavelength sub-range, and the system combines results from all segments to achieve broad overall wavelength coverage while maintaining compact PIC integration.
Solution Approach 2:
The patent designs the PIC wavemeter to perform multiple wavelength measurement functions simultaneously across different wavelength bands. The integrated structure supports universal operation from visible to infrared ranges by incorporating multiple interferometer types and detection channels that can handle diverse wavelength requirements within a single device.
3Adaptability or versatility
If long waveguide lengths are used in PIC wavemeters, then wavelength measurement range increases, but optical power losses become unacceptable
Solution Approach 1:
The patent uses tunable interferometer designs where the optical path difference can be dynamically adjusted. This allows the system to achieve broad wavelength range coverage by varying the measurement conditions rather than requiring permanently long waveguides, thereby maintaining low insertion losses while extending measurable wavelength ranges through dynamic reconfiguration.
4Device complexity
If photonic integrated waveguides are used, then device integration is improved, but birefringence causes accuracy penalties
Solution Approach 1:
The patent incorporates polarization diversity detection that measures both orthogonal polarization states simultaneously. By detecting and comparing the interference patterns from both polarization modes, the system can identify and compensate for birefringence-induced phase differences, thereby maintaining measurement accuracy despite the integrated waveguide structure's inherent polarization sensitivity.
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 PIC optical wavemeter provides stable and accurate wavelength measurements over a wide range, including the optical communications wavelength band, with improved power measurement accuracy and reduced space and cost requirements compared to bulk-optic solutions.
Implementation Method 1
A first Mach-Zehnder Interferometer (MZI) having a first free spectral range (FSR); a second MZI having a second FSR
Data Source
AI summary
An apparatus for determining a wavelength and a power of an input signal is described. The apparatus comprises a memory which stores instructions, which when executed by the processor, cause the processor to: recover a first phase for a first Mach-Zehnder Interferometer MZI; recover a second phase for a second MZI; subtract the first phase from the second phase to provide a phase difference; determine an unwrapped phase difference as a function of wavelength; determine a coarse wavelength; and determine a first wavelength for the first FSR and a second wavelength from the second FSR; and average the first and second wavelengths to determine the wavelength of the input signal.