Optical sensor for measuring physical parameters in harsh environments and methods of making and using same

Abstract

An optical sensor for measuring physical parameters in harsh environments and methods of making and using the same are disclosed. An optoelectronic system for measuring a physical parameter includes two narrowband light sources having different peak frequencies coupled together with a coupler into a combined light. The combined light is divided into a first Fabry-Perot interferometer and a second Fabry-Perot interferometer, the first Fabry-Perot interferometer being configured to be exposed to temperature and another physical parameter, and the second Fabry-Perot interferometer being configured to be exposed only to temperature. The system further comprises a first optical detector and a second optical detector arranged to receive light reflected from the cavities of the first and second Fabry-Perot interferometers, respectively, through a combined optical path comprising a lens and / or mirror and the Fizeau interferometer. The processor is configured to analyze data received by the first optical detector and the second optical detector and calculate temperature values and physical parameters.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202011379479.6, filed on November 30, 2020, entitled “Optical Sensor for Measuring Physical Parameters in Harsh Environments and Methods of Manufacturing and Using the Same”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 942,064, filed on November 29, 2019, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0004] The present patent document generally relates to an optical sensor. More specifically, the subject matter of the present patent document relates to an optical sensor for an aero-engine, a land-based turbine such as a gas or steam turbine, or any power generator having a combustion chamber. BACKGROUND

[0005] Optical fiber sensing technology offers some advantages over traditional electrical sensing technology for monitoring and controlling physical parameters of an aero-engine, a land-based turbine such as a gas or steam turbine, or any power generator having a combustion chamber. In particular, the following advantages have been demonstrated: (i) improved measurement accuracy and bandwidth; (ii) intrinsic insensitivity to external disturbances, i.e., electromagnetic and radio frequency interferences; (iii) long to ultra-long range measurements with negligible signal attenuation; (iv) distributed sensing: the possibility of multiplexing a large number of individually addressed point sensors; and (v) compatibility with high to very high temperatures. Therefore, replacing electrical sensors with optical fiber sensors is desirable for many applications, in particular for aerospace applications.

[0006] In aerospace applications, an aero-engine requires multiple sensing systems to operate reliably and safely. Some sensing systems provide physical parameters to an electronic engine controller (EEC) to control engine operation. Other sensing systems provide parameters to an engine monitoring unit (EMU) to monitor engine operation, to alert the pilot in case of unsafe conditions or ground-based maintenance, and when the engine needs to be overhauled. In current aero-engines, all sensors are based on electrical working principle technology, such as piezoelectric, piezoresistive, and capacitive measurement principles. For each individual sensor, an electrical readout signal is sent through an electrical wire connected to the engine electronics unit. These discrete outputs result in long cable harnesses with multiple connectors, increasing the complexity of the engine architecture and significantly increasing the weight, which in turn increases the fuel consumption of the engine.

[0007] One specific application is the measurement of pressure between the latest stage of the engine's high-pressure compressor and the combustion chamber. This measurement output is used in the control loop of engine operation. To date, no invention has been proven capable of reliably measuring absolute (static) pressure during operation at temperatures exceeding 300°C, and none can handle temperatures above 400°C or 500°C. Therefore, engine control relies on a cryogenic pressure sensor located in an electronic unit mounted on the engine's fan housing, in the engine's lowest temperature range (maximum operating temperatures are typically between 80°C and 125°C). This configuration requires routing pressure lines from the combustion chamber to the sensor and compensating for temperature differences in the measurement. Furthermore, this can lead to measurement instability under certain environmental conditions. One object of this invention is to directly measure pressure within the engine core, eliminating the pressure line, reducing weight, and improving measurement accuracy. Summary of the Invention

[0008] This invention provides an optoelectronic system for measuring physical parameters. The optoelectronic system is particularly suitable for measuring physical parameters in harsh environments, such as those found in engine compartments.

[0009] In a preferred embodiment, the optoelectronic system includes an optical sensor comprising: a first Fabry-Perot interferometer configured to receive a first portion of the combined light, wherein the first Fabry-Perot interferometer is exposed to a physical parameter of interest and a temperature; and a second Fabry-Perot interferometer configured to receive a second portion of the combined light, wherein the second Fabry-Perot interferometer is exposed to a temperature but not to the physical parameter of interest.

[0010] The system further includes an interrogator in optical communication with the optical sensor, the interrogator comprising: a first narrowband light source having a first peak frequency; a second narrowband light source having a second peak frequency different from the first peak frequency; a coupler configured to couple the first narrowband light source and the second narrowband light source into the combined light; a first Fizeau interferometer configured to receive light reflected from a first cavity of the first Fabry-Perot interferometer to a first optical detector through an optical path including a combination of lenses and / or mirrors; a second Fizeau interferometer configured to receive light reflected from a second cavity of the second Fabry-Perot interferometer to a second optical detector through an optical path including a combination of lenses and / or mirrors; and a processor configured to analyze data received by the first optical detector and the second optical detector, and to calculate a temperature value and the second physical parameter.

[0011] Although the system taught herein can be used to measure any physical parameter, in a preferred embodiment, pressure and temperature are measured.

[0012] In some embodiments, the first and second light sources are part of a transmitting module, which is physically separate from the first Fizeau interferometer, the second Fizeau interferometer, the first optical detector, and the second optical detector located in the detection module. The transmitting module and the detection module together constitute the interrogator. In other embodiments, the components of the transmitting module and the detection module can be combined into a single module.

[0013] In a preferred embodiment, the first and second Fizeau interferometers, the first and second optical detectors, and the optical elements are all mounted on a plate made of a material with a low coefficient of thermal expansion. In some embodiments, the coefficient of thermal expansion is less than 2 x 10⁻⁶ / °C. In other embodiments, the coefficient of thermal expansion is less than 1 x 10⁻⁶ / °C.

[0014] The optoelectronic systems taught herein are specifically designed for use in harsh environments. In particular, the systems taught herein are designed for use with turbofan engines. Therefore, in some embodiments, the optical sensor is mounted in the engine core of the turbofan engine. In such embodiments, the interrogator may be mounted in the fan housing of the turbofan engine and optically coupled to an optical transducer via at least one optical fiber.

[0015] In some embodiments, the first light source, the second light source, the first Fizeau interferometer, the second Fizeau interferometer, the first optical detector, and the second optical detector are all hermetically sealed in a metal box having a controlled internal atmosphere using air, vacuum, or inert gas.

[0016] In another aspect of the invention, a method for detecting physical parameters in harsh environments using optical sensors is provided. In a preferred embodiment, the method includes: coupling a first narrowband light source having a first peak frequency to a second narrowband light source having a second peak frequency different from the first peak frequency to generate combined light; receiving a first portion of the combined light in a first Fabry-Perot interferometer; exposing the first Fabry-Perot interferometer to a temperature and a second physical parameter; receiving a second portion of the combined light in a second Fabry-Perot interferometer; exposing the second Fabry-Perot interferometer to the temperature but not to the second physical parameter; receiving light reflected from a first cavity of the first Fabry-Perot interferometer to a first optical detector through an optical path including a combination of lenses and / or mirrors and a first Fizeau interferometer; receiving light reflected from a second cavity of the second Fabry-Perot interferometer to a second optical detector through an optical path including a combination of lenses and / or mirrors and a second Fizeau interferometer; and analyzing data received by the first and second optical detectors to calculate a temperature value and the second physical parameter.

[0017] Some embodiments of the method further include: measuring a first dimension of the first cavity of the first Fabry-Perot interferometer and a second dimension of the second cavity of the second Fabry-Perot interferometer by detecting the maximum value of the destructive interference pattern generated along the first and second optical circuits using a numerical method.

[0018] In other embodiments, the method further includes: detecting and tracking the maximum value of the destructive interferogram using a numerical method based on the pixel intensity of a linear or matrix photodetector, wherein the interference peak information is combined with the geometry of the first Fizeau interferometer and the second Fizeau interferometer to calculate the first dimension and the second dimension.

[0019] In some embodiments, the processor calculates the Fourier transform of the interference spectrum to determine the change in the size of the first cavity of the first Fabry-Perot interferometer.

[0020] In some embodiments, the method further includes: converting the second dimension into a temperature measurement using the physical properties of the second cavity, and converting the first dimension into a measured physical parameter using the physical properties of the first cavity and the temperature measurement.

[0021] In some methods, demodulation is used to remove non-uniform illumination from the first optical detector, and a low-pass filter is used to remove electro-optic noise.

[0022] To detect and track peaks in destructive interference, some methods utilize simulated annealing search or subpixel interpolation.

[0023] In some other embodiments, the fast Fourier transform of the fringe pattern spectrum is calculated and analyzed, and the intensities of the first and second narrowband light sources are balanced across the entire temperature range. When balance is achieved, equal optical power from each of the two light sources reaches the optical detector.

[0024] In some embodiments, the interrogator is calibrated to measure the cavity dimensions of the first Fabry-Perot interferometer independently of the second transducer. In such embodiments, the physical parameters of the second transducer can be stored in the interrogator.

[0025] Each of the foregoing aspects may be combined with the content set forth in the claims and the description relating to the embodiments summarized above and disclosed herein to form claims for the apparatus, system, method of manufacture and / or use in any manner disclosed herein without limitation.

[0026] These and other features, aspects, and advantages are described below with reference to the accompanying drawings, which are intended to illustrate rather than limit the invention. In the drawings, similar reference numerals consistently denote corresponding features throughout similar embodiments. Attached Figure Description

[0027] Figure 1 A schematic diagram illustrating a system overview of one embodiment of an optical sensor.

[0028] Figure 2 Show Figure 1 A schematic diagram showing the sub-components of the optical integrator and the optical transducer.

[0029] Figure 3 Showing what is mounted on a turbofan engine, such as Figure 1 and Figure 2 An embodiment of the optical sensor described herein.

[0030] Figure 4 The diagram shows some typical lengths of system components in the optical sensor of a high bypass ratio turbofan engine.

[0031] Figure 5 A cross-sectional view of an embodiment of an optical transducer used with the optical sensor described herein is shown.

[0032] Figure 6 A schematic diagram of an extension cable used with the optical sensor taught herein is shown.

[0033] Figure 7 An isometric view of an embodiment of a photoelectronic interrogator with a transparent housing is shown.

[0034] Figure 8 ShowFigure 7 An exploded view of the photoelectronic interrogator.

[0035] Figure 9 A schematic diagram of the optical design and optical path is shown for one embodiment of an optical detection module and an optical emission module for use with the optical interrogator disclosed herein.

[0036] Figure 10 This diagram illustrates how the system can utilize multiplexing techniques to use a single interrogator with multiple sensors.

[0037] Figure 11 A block diagram is shown of one embodiment of a modular optoelectronic interrogator LRU according to system requirements.

[0038] Figure 12 A block diagram illustrating one embodiment of the CPM architecture is shown.

[0039] Figure 13 A block diagram illustrating one embodiment of the OIM architecture is shown.

[0040] Figure 14 A schematic diagram showing an embodiment of the temperature control layer of OIM.

[0041] Figure 15 The expected interference fringe pattern with the maximum destructive interference point on the identified plot is shown.

[0042] Figure 16 Interference fringe patterns are shown with (i) geometric and fiber effects that produce “bell-shaped” modulation above the fringe shape and (ii) electro-optic noise.

[0043] Figure 17 A block diagram illustrating an example of system signal processing for calculating and compensating pressure measurements. Detailed Implementation

[0044] This invention relates to a fiber optic sensing system that mitigates problems associated with the harsh environments of machines as described in the background section. The system described herein is particularly well-suited for use in harsh environments. While harsh environments can be any adverse conditions, the term "harsh environment" as used herein refers to environments commonly found in aircraft engines. Therefore, depending on the type of measurement, the interrogator temperature ranges from -40°C to 80°C or -55°C to 125°C, while the transducer temperature ranges from -55°C to over 700°C. These temperatures are associated with severe vibrations. In one example, the system is designed for measuring the static pressure in the combustion chamber of an aircraft turbofan engine. The system is capable of measuring pressure and other physical parameters with the accuracy and reliability required for engine applications. By centralizing all data reading and processing in a single optoelectronic interrogator and / or multiplexing the outputs of multiple sensors on a single fiber, the engine sensing architecture is greatly simplified and can be significantly lighter than the electrical systems.

[0045] System Description

[0046] The following describes an exemplary embodiment of pressure and temperature measurement in the high-temperature core of an aircraft turbofan engine. Alternative embodiments may be applied to machines as described in the Background section, or may be used in any high-temperature environment; in particular, previously limited to electrical sensor environments. As an example only, the sensing system described herein can be used in a hydrogen-powered engine. Other embodiments may use the same system definition to measure other parameters such as temperature, mechanical displacement, mechanical stress, vibration, acceleration, rotational speed (e.g., shaft speed), clearance, closed / open state (e.g., valve closed / open state), airflow, and other physical parameters for controlling machine operation or monitoring machine condition.

[0047] Figure 1 A schematic diagram showing a system overview of one embodiment of the optical sensor 10. Figure 1 As can be seen, the optical sensor 10 can consist of three subsystems: a photoelectronic interrogator 12, an optional optical extension cable 14, and an optical transducer 16. These subsystems are connected together to exchange optical signals between them via optical fibers, such as... Figure 1 As shown. If the integrating cable 16A of the optical transducer 16 is directly connected to the optoelectronic interrogator 12, the optical extension cable 14 can be removed.

[0048] Figure 2 Show Figure 1A schematic diagram of the optical sensor 10 is shown, illustrating sub-components of an optical interrogator and an optical transducer. The optoelectronic interrogator 12 includes a light source 20, an optical module 21, a digital processing unit 22, a communication unit 23, and a power management unit 24. An optical extension cable 14 includes and protects at least two optical fibers connecting the optoelectronic interrogator 12 to the optical transducer 16. The transducer 16 consists of two sensing elements: a pressure sensing element 31 and a temperature sensing element 32. Each sensing element includes a Fabry-Perot interferometer cavity sensitive to the measured physical parameter. Both elements are connected to an optical fiber protected by an integrating cable 33.

[0049] In a preferred embodiment, system 10 is mounted on aircraft turbofan engine 30. Figure 3 Showing what is mounted on a turbofan engine, such as Figure 1 and Figure 2 One embodiment of the optical sensor described herein. An optoelectronic interrogator 12 is mounted on the external portion of the fan housing of engine 30, near other electronic units of the engine, where the engine temperature is relatively cool (typically between 80°C and 125°C, or, depending on the engine, even hotter). The interrogator 12 is connected to an optical extension cable 14, which is routed to the engine's hot zone where the ambient temperature is typically between 125°C and 250°C. The end of the optical extension cable 14 is linked to... A transducer 16 is mounted on the engine core in a manner capable of sensing the pressure and temperature of engine air in the high-pressure compressor, combustion chamber, and turbine zone, where temperatures can exceed 300°C, 400°C, or even 500°C.

[0050] Despite Figure 3 In this embodiment, the transducer is mounted on the engine core, but in other embodiments, the sensor may be mounted in other locations. Typical transducer mounting locations may include, but are not limited to, the location where the current pressure and temperature sensors are mounted (an optical transducer will replace the conventional pressure and temperature sensors in the aforementioned general area). The transducer body 16 is typically fixed to an engine mounting structure, such as a compressor housing (on the high-pressure compressor side), a combustion chamber, and / or a turbine housing. The transducer head (the area extending beyond flange 40 to the end of radiation shield 43) itself will be immersed in the airflow via an associated duct or direct insertion into the housing.

[0051] Figure 4 The diagram illustrates some typical lengths of system components in the optical sensor of a high bypass ratio turbofan engine. It is understood that these dimensions are for reference only to a particular embodiment, and other embodiments may use different lengths for the same type of engine or different types of engines or other devices.

[0052] In operation, the interrogator 12 transmits an optical signal to the optical transducer 16 via optical extension cables 14 and 16A. The light is modulated according to the applied external pressure through a Fabry-Perot cavity embedded in the pressure sensing element 16. The reflected light signal is analyzed by the optoelectronic interrogator 12. The pressure is then calculated by the processing unit of the interrogator 12. Temperature is measured in a similar manner and used to compensate for the effects of temperature variations on the sensing element. The temperature and pressure data are then digitally output to other engine electronics units.

[0053] Optical transducer design

[0054] Figure 5 A cross-sectional view of one embodiment of an optical transducer 16 used with the optical sensor 10 described herein is shown. The optical transducer includes a fiber optic Fabry-Perot temperature sensing element 41 and a pressure sensing element 42. As... Figure 5 As can be seen, both temperature sensor 41 and pressure sensor 42 are located at the front end of transducer 16. Figure 5 In the illustrated embodiment, the pressure sensor 42 is located directly in front of the temperature sensor 41. It is contained within a compartment in a hollowed-out body formed at the front end of the transducer. The Fabry-Perot temperature sensor 41 and the pressure sensor 42 each have a cavity 45.

[0055] In a preferred embodiment, sensing elements 41 and 42 are made of a nickel-based superalloy that exhibits a low coefficient of thermal expansion (CTE) and high mechanical resistance at ambient temperatures above 300°C. Depending on the application, the housing 40 of transducer 16 is preferably made of stainless steel (AISI 316L) or a nickel-based superalloy. A specific radiation shield 43 made of a nickel-based superalloy is assembled at the end of transducer 16. During manufacturing, a vacuum is applied to the internal volume of housing 40, and an inert gas is introduced.

[0056] Extension cable design

[0057] Figure 6 A schematic diagram of an extension cable 14 used in conjunction with the optical sensor 10 taught herein is shown. The optical extension cable 14 connects the optical transducer 16 and the optoelectronic interrogator 12. In a preferred embodiment, depending on the system configuration, the optical extension cable 14 comprises two optical fibers and can accommodate wires. The optical fibers are protected by a braided stainless steel layer and a PTFE layer. The braided stainless steel provides mechanical resistance. Connectors at each end are crimped onto the braided stainless steel. PTFE sleeves protect against all corrosive fluids. Therefore, the optical fibers themselves are not subjected to any mechanical forces and are not exposed to any contamination. To operate in the preferred application, the optical cable 14 must withstand temperatures exceeding the temperature of its hottest end (i.e., the connection to the optical transducer, typically 150°C to 250°C).

[0058] In a preferred embodiment, depending on the application, the optical extension cable is approximately 5 meters long, and each connector is approximately 79 mm long. As will be understood by those skilled in the art, variations in these dimensions may be made without departing from the scope of the invention, which is provided only as an example.

[0059] Photoelectronic Interrogator Design

[0060] Preferably, the photoelectronic interrogator 12 is designed as a line replacement unit (LRU). In a preferred embodiment, the photoelectronic interrogator 12 is designed to be mounted on the fan housing of the engine, such as... Figure 3 As shown. In other embodiments, the electronic and optical modules (unpackaged) of the optical interrogator can be directly implemented as the electronic units of existing engines (e.g., FADEC, EMU, etc.).

[0061] Figure 7 An isometric view of one embodiment of a photoelectronic interrogator 12 with a transparent housing 50 is shown. The housing 50 of the interrogator includes a base 51, a central frame 52, and a cover 53. In a preferred embodiment, the entire housing 50 is made of black anodized aluminum alloy. Figure 7 In the illustrated embodiment, the base 51 has four legs and a mounting adapter 54, which includes a custom-designed shock absorber for securing the unit to the engine and suppressing engine vibrations.

[0062] In some embodiments, the optical module is hermetically sealed in a metal or plastic housing with a controlled internal atmosphere using air, vacuum, or an inert gas. In other embodiments, the entire optoelectronic interrogator housing may be hermetically sealed.

[0063] Figure 8 Show Figure 7 An exploded view of the optoelectronic interrogator 12. In a preferred embodiment of the optical interrogator 12, all electronic boards, connectors, and optical modules are assembled on a central frame 52. Additionally, in a preferred embodiment, the central frame 52 is made of a single unit. This architecture is particularly suitable for high-vibration environments and provides great flexibility in system configuration. For example, an additional frame can be assembled on top of the first frame without compromising system robustness. This configuration provides flexibility to add functionality or sensing channels to the system according to application requirements.

[0064] The interrogator 12 includes a light source, an optical detection module, a multiplexing stage, a temperature regulation stage, a central processing module (CPM) electronic board, and an optoelectronic interrogator module (OIM) electronic board.

[0065] In a preferred embodiment, the optical detection module and the optical emission module are physically separated within the interrogator 12. "Physically separated" means that at least two modules are mounted on different mounting bases. In a preferred embodiment, physical separation may refer to mechanical isolation from each other using dampers or other mechanical isolation methods.

[0066] Optical module

[0067] Figure 9 A schematic diagram of the optical design and optical path is shown for one embodiment of an optical detection module 60 and an optical emission module 61 for use with the optical interrogator 12 disclosed herein. The optical detection module 60 within the optical interrogator 12 comprises optical circuitry components enclosed in a sealed enclosure. The optical circuitry includes discrete passive optical components (and / or micro-optical elements) and optoelectronic components, such as incandescent lamps, light-emitting diodes (LEDs), superluminescent LEDs (SLEDs), laser diodes, vertical-cavity surface-emitting lasers (VCSELs), lasers, tunable lasers, supercontinuum lasers, photodiodes, charge-coupled device (CCD) image sensors, and complementary metal-oxide-semiconductor (CMOS) image sensors. The optical and optoelectronic components are precisely aligned and fixed to a low-thermal-expansion substrate mounted on a substrate enclosed in the enclosure. An optical fiber is coupled to the system for external optical communication. Optionally, some or all of the functions of the discrete optical elements may be integrated into a photonic integrated circuit (photonic chip).

[0068] Depending on the application, the emitting module 61 includes one or more LEDs 62. In a configuration including two LEDs 62, a central emission wavelength is selected to maximize the effect of destructive interference measured by the detection module 60. For example, in one embodiment, the first LED may emit in the visible spectrum and the second LED may emit in the infrared spectrum. In other embodiments, other wavelengths may be used. The light emitted by the two or more LEDs is coupled into an optical fiber using an optical coupler 63.

[0069] The optical detection module 60 has two main functions. The first is to collect light from the emission module 61 and split it via an optical coupler or beam splitter 64 to distribute it to one or more transducers 66 and 67. The second function is to collect and analyze the light signals reflected from the Fabry-Perot cavities of the transducers 66 and 67. This signal passes through the same beam splitter 64 as the emission module. However, in this case, the light is directed to the optical analysis system 68. The optical analysis system 68 includes a series of lenses and mirrors for shaping the light beam. In a preferred embodiment, the mirrors and / or lenses in the optical path are designed to improve the uniformity of the light intensity distribution throughout the Fiso wedge 69.

[0070] The last optical element is a cylindrical mirror or lens, which reflects light toward the photodetector 70. A Fizeau interferometer 69 is attached to the front of the detector 70. This fixed and stable interferometer 69 has well-known characteristics, so the size of the Fabry-Perot cavity of transducers 66 and 67 can be inferred by cross-correlation between the signal from the sensor and the characteristic features of the Fizeau interferometer 69 itself.

[0071] Reuse

[0072] Figure 10 A schematic diagram illustrates how the system can utilize multiplexing techniques with a single interrogator 12 that has multiple sensors. The system is designed to provide the opportunity to measure more than one Fabry-Perot sensing element. As described above, the system uses a single source module that can be segmented and sent to multiple sensors. This method enables the interrogation of multiple sensing elements with the same optoelectronic engineering based on multiplexing methods such as temporal multiplexing, spatial multiplexing, and wavelength multiplexing.

[0073] Electronic unit

[0074] Figure 11 A block diagram of an embodiment of a modular optoelectronic interrogator LRU is shown, based on system requirements. This is the electronic part of the interrogator. The LRU is decomposed into two subsystems. The first subsystem is a standardized motherboard assembly 72, called the Central Processing Module 72 (CPM), which includes: 1) a processing layer of supervisor software (SW) and programmable logic; 2) a communication layer for interacting with other LRUs 73; 3) a configurable controller for acquiring pressure and temperature data; and 4) a power management and power conversion layer 74.

[0075] The second subsystem is the optoelectronic interrogator module (OIM) 80, which includes: 1) at least two optical modules 81; 2) a configurable power supply for the light source 82; 3) a configurable interface for acquiring pressure signal 83 and temperature signal 84; and 4) a thermal management layer 85.

[0076] Due to the modularity and scalability of the system, the LRU can be optionally modularized according to system requirements. For example, an additional fetch module can be included to extend fetch functionality without changing existing subsystems or shell components.

[0077] Central Processing Module (CPM)

[0078] Figure 12 The diagram illustrates one embodiment of the CPM72 architecture. At the heart of the CPM72 is a fully programmable system-on-a-chip (SoC), which includes a central processing unit (CPU) that manages a specific switch application, and highly flexible programmable logic (or FPGA) that enables connection to a wide range of different peripherals simply by being reprogrammed.

[0079] The CPU and programmable logic provide system processing capabilities and support for various communication interfaces. Alternatively, all processing functions of the CPM can also be handled by an FPGA without the need for a CPU.

[0080] A communication layer is provided for communication with other LRUs or ground stations. In this embodiment, the LRU provides ARINC-429, Ethernet, and RS-232 interfaces. Alternative and additional interfaces (e.g., CAN, RS-422, RS-485, etc.) can be provided by replacing the wire-removable submodule of the CPM72.

[0081] In a preferred embodiment, the CPM72 includes a mezzanine connector that provides available communication, control, and feedback signals to any other subsystems of the LRU, thereby providing a highly modular structure. In this embodiment, these internal signals are used to program and control the acquisition of pressure and temperature signals and to control the system's thermal management. The CPM72 also includes a power management layer 74 that interacts with the aircraft power input and provides stable power to other subsystems of the LRU.

[0082] Optical Interrogator Module (OIM)

[0083] Figure 13 A block diagram illustrating one embodiment of the OIM80 architecture is shown. Figure 13 The OIM80 includes an interface for regulating and acquiring pressure signals 84 and temperature signals 83 from the optical detection module 81. This allows the CPM72 to independently control the acquisition parameters of each input signal. This includes independent control of the gain and sampling frequency of each channel. Two independent current sources provide power to the light source of the optical emission module 81. The CPM72 dynamically adjusts the current supplied to each source based on internal parameters such as the temperature of internal components or the actual light intensity received on the optical detection module 81. Multiple temperature sensors 85 are also provided to monitor and report the temperature values ​​of various system components to the CPM72. This temperature data may include board temperature, CCD temperature, LED temperature, and any other temperatures in the OIM80 that will benefit the CPM72. When exposed to temperatures different from room temperature, the temperature data from the OIM80 can be used to further compensate for potential changes in the components.

[0084] Thermal regulation design

[0085] To mitigate temperature-induced changes in the characteristics of optical components, particularly the loss of optical power at high temperatures, a temperature management layer is implemented in the OIM80. This layer consists of active temperature control of the optical modules. The temperature of the light emission and detection modules is measured by temperature sensors and controlled by thermoelectric regulators. Figure 14 shows a schematic diagram of one embodiment of the temperature control layer 85 of the OIM80. Thermoelectric coolers 91 and 92 (TEC or Peltier elements) are used to cool or heat the optical components. TEC91 is attached to the optical emission module 61, and another TEC92 is attached to the optical detection module 65 to extract heat from the device and redirect it to a heat sink. The LRU housing 50 is used to absorb heat and acts as a heat sink, preventing heat from entering the LRU. Therefore, this embodiment preferably uses a standard heat sink placed inside the LRU, as those would cause a more significant increase in internal temperature. Conversely, TEC91 and TEC92 can be used to heat the modules if needed. A thermal sensor is attached to the module to provide a measurement of the module temperature, allowing the TEC controller to adjust the power supplied to TEC91 and TEC92 based on the temperature. During the digital processing of the data, the temperature information of the optoelectronic components (if not or partially stored for thermal regulation) can be further used to compensate for thermal effects / shifts on the output signal.

[0086] Signal processing

[0087] The minimum position of the fringe interference read by the optical detector is directly related to the size of the Fabry-Perot cavity of the transducer. The pressure and temperature stimuli it was exposed to can then be reconstructed from this information. The processing objective is to identify the maximally destructive interference signal. Figure 15 The expected interference fringe pattern with the maximum destructive interference point on the identified plot is shown.

[0088] Interference is not the only actor that determines the shape of a signal. Two other actions can also affect the shape of the signal. Figure 16 An interference fringe pattern is shown, exhibiting (i) geometric and fiber effects that produce "bell-shaped" modulation above the fringe shape and (ii) electro-optic noise. Both effects should be eliminated or compensated for in order to perform detection correctly.

[0089] Figure 17A block diagram illustrating an example of system signal processing for calculating and compensating for pressure measurements is shown. The input to this process is an optical interference signal acquired by optical detector 102, one for each channel (e.g., temperature and pressure). Intermediate output blocks 103-106 are measurements of the dimensions of the two cavities. As previously described, these are sent to respective conversion blocks 107 to generate the measured temperature and a first estimate of the pressure. This estimate is then converted to the final value within the temperature correction block 108. The noise cancellation block consists of a low-pass frequency FIR filter. The low-pass cutoff frequency is related to the interferogram fringe period. Bell demodulation consists of a high-pass filter implemented by average subtraction. The magnitude of the average is determined by the interferogram fringe period.

[0090] The point of maximum destructive interference (minimum of the fringe signal) is determined on the filtered / demodulated signal. The search strategy consists of a local minimum search centered on the time-tracking location. False minimum discoveries (e.g., noise peaks at local extrema) are mitigated by implementing a minimum jump strategy controlled by threshold annealing. Once determined, standard parabolic subpixel interpolation of the pixel location is performed to improve the accuracy of the results.

[0091] Once the minimum pixel location (called the pixel index) is determined with sub-pixel precision, it is converted into nanometers representing the size of the corresponding Fabry-Perot cavity using a Fiso wedge lookup table determined through pre-calibration. The cavity size can then be converted to a pressure measurement using additional lookup tables representing the cavity's physical properties as functions of temperature (thermal coefficients and membrane sensitivity).107

[0092] To this end, the processor uses a numerical method to measure the size of each of the two Fabry-Perot cavities by detecting the maximum value of the destructive interference pattern generated along each of the two optical circuits. The processor detects and tracks the maximum value of the destructive interference pattern based on the pixel intensity of a linear or matrix photodetector generated by the optical circuitry. The method combines interference peak information with the geometry of a Fizeau interferometer to calculate the Fabry-Perot cavity size. The processor can also convert the size of the second Fabry-Perot cavity into temperature using the physical properties of the second Fabry-Perot cavity. Using the physical properties of the first cavity and the temperature measurement of the second cavity, the size of the first Fabry-Perot cavity is converted into a measured physical parameter (e.g., pressure).

[0093] In other embodiments, the processor calculates the Fast Fourier Transform (FFT) of the interference spectrum to determine the size variations of the Fab-Perot interferometer.

[0094] In some embodiments, the processor uses numerical methods to calculate and analyze the FFT of the fringe pattern spectrum and balance the intensities of the two light sources across the entire temperature range. The FFT information from the interferogram can be additionally used to continuously determine the integrity of the optical circuitry (BIT).

[0095] Finally, in some embodiments, the system is calibrated in a manner where the interrogator and transducer are interchangeable. The interrogator is calibrated to measure the Fabry-Perot cavity size independently of the transducer. The physical parameters of the transducer are stored in the interrogator and converted into measured physical parameters (e.g., pressure) using the Fabry-Perot cavity size.

[0096] Optoelectronic component control

[0097] Balanced control of the light source and CCD levels has been introduced to improve measurement capabilities. If this control fails to meet predetermined conditions, a fault signal is sent to the BIT (Block In-System Test) block. The BIT will detect and classify different faults in the optical circuitry, such as temperature or pressure CCD saturation, temperature or pressure CCD low signal, low level of source 1 or source 2 or any other source.

[0098] First, the system verifies whether the CCD is functioning correctly by analyzing pixel-level values. Saturation and low-light conditions are determined based on the maximum and average pixel values, respectively. In saturation conditions, the CCD's integration time decreases until the saturation disappears. In low-light conditions, the CCD's integration time increases until the average level meets the acceptance criteria. If these conditions cannot be met, a signal is sent to the BIT.

[0099] When the CCD operates within a predetermined acceptance range, its signal is analyzed independently. For each CCD, a Fourier transform is performed on the interference signal, and two local peaks in the spectrum are identified. Each local peak corresponds to the contribution of an individual light source. Local peak detection is performed using the corresponding source peak wavelength λ, the slope of the Fizeau interferometer α, and the CCD pixel size P. size It operates within a range centered on a defined frequency F.

[0100] F=tg(α)*P size / λ

[0101] For each CCD, if the difference between the two peaks is below a predefined threshold, it means that the source levels are balanced. Otherwise, the current flowing to the source corresponding to the weaker peak will increase, and the current flowing to the source corresponding to the stronger peak will decrease, until the two peak levels reach a predetermined acceptable level. If the acceptable level cannot be reached, a signal is sent to the BIT.

[0102] Although the patent document has specifically discussed the use of Fabry-Perot interferometers in general, other sensors can be used. For example, sensors based on fiber Bragg gratings (FBGs) can be used.

[0103] While various aspects of the invention have been disclosed herein in the context of certain preferred embodiments, implementations, and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses of the invention and their obvious modifications and equivalents. Furthermore, although various variations of aspects of the invention have been shown and described in detail, other modifications within the scope of this disclosure will be apparent to those skilled in the art. It should also be understood that the scope of this disclosure includes various combinations or sub-combinations of the specific features and aspects of the embodiments disclosed herein, such that various features, implementations, and aspects of the disclosed subject matter may be combined with or replaced by another. Therefore, it is intended that the scope of the invention disclosed herein should not be limited to the specific embodiments or implementations disclosed above, but should be determined only through a proper interpretation of the claims.

[0104] Similarly, this disclosure should not be construed as reflecting an intention that any claim requires more features than those expressly recited in that claim. Rather, as reflected in the appended claims, the inventive aspect lies in a combination of fewer than any single foregoing disclosed embodiment. Therefore, the claims following this detailed description are intentionally incorporated into it, each claim existing independently as a separate embodiment.

[0105] Furthermore, all claim terms should be interpreted in their broadest form to provide the applicant with the widest legally permissible coverage. Although embodiments have been described with reference to the accompanying drawings and specific examples, it will be readily understood by those skilled in the art that various modifications and adaptations can be made to the processes, methods, and apparatus described herein without departing from the spirit and scope of the embodiments claimed herein. Therefore, it should be clearly understood that this description is by way of example only and is not intended to limit the scope of the following claimed embodiments.

Claims

1. An optoelectronic system for measuring a physical parameter, comprising: an optical sensor; and an interrogator in optical communication with the optical sensor, wherein the optical sensor comprises: a first Fabry-Perot interferometer configured to receive a first portion of combined light, wherein the first Fabry-Perot interferometer is exposed to a temperature and a physical parameter of interest; and a second Fabry-Perot interferometer configured to receive a second portion of the combined light, wherein the second Fabry-Perot interferometer is exposed to the temperature and not exposed to the physical parameter of interest; the interrogator comprising: a first narrowband light source having a first peak frequency; a second narrowband light source having a second peak frequency different from the first peak frequency; a coupler configured to couple the first and second narrowband light sources into the combined light, wherein the first portion of the combined light and the second portion of the combined light each include light from the first and second narrowband light sources; a first Fizeau interferometer configured to receive the first portion of the combined light reflected from a first cavity of the first Fabry-Perot interferometer to a first optical detector via an optical path including a lens or a mirror; a second Fizeau interferometer configured to receive the second portion of the combined light reflected from a second cavity of the second Fabry-Perot interferometer to a second optical detector via an optical path including a lens or a mirror; and a processor configured to analyze data received by the first and second optical detectors and to calculate a temperature value and the physical parameter of interest.

2. The optoelectronic system of claim 1, wherein, The physical parameter is pressure.

3. The optoelectronic system of claim 1, wherein, The first and second narrowband light sources are part of an emission module mounted on a first base plate and physically separated from the first and second Fizeau interferometers, the first and second optical detectors in a detection module mounted on a second base plate.

4. The optoelectronic system of claim 1, wherein, The first and second Fizeau interferometers, the first and second optical detectors are each mounted on a plate made of a material having a coefficient of thermal expansion lower than 2 x 10"6 / °C.

5. The optoelectronic system of claim 1, wherein, The optical sensor is mounted on an engine core.

6. The optoelectronic system of claim 1, wherein, The optical sensor is mounted on an engine core of a turbofan engine.

7. The optoelectronic system of claim 6, wherein, The interrogator is mounted on a fan case of the turbofan engine and is in optical communication with the optical sensor via at least one optical fiber.

8. The optoelectronic system of claim 1, wherein, The first and second narrowband light sources, the first and second Fizeau interferometers, the first and second optical detectors are each hermetically sealed in a metal box having a controlled internal atmosphere using air, vacuum or an inert gas.

9. A method for detecting a physical parameter in a harsh environment using an optical sensor, comprising: coupling a first narrowband light source having a first peak frequency with a second narrowband light source having a second peak frequency different from the first peak frequency to produce combined light; receiving a first portion of the combined light in a first Fabry-Perot interferometer, the first portion of the combined light including light from the first narrowband light source and the second narrowband light source; exposing the first Fabry-Perot interferometer to a temperature and a physical parameter of interest; receiving a second portion of the combined light in a second Fabry-Perot interferometer, the second portion of the combined light including light from the first narrowband light source and the second narrowband light source; exposing the second Fabry-Perot interferometer to the temperature and not to the physical parameter of interest; receiving the first portion of the combined light reflected from a first cavity of the first Fabry-Perot interferometer into a first optical detector through an optical path including a lens or a mirror and a first Fizeau interferometer; receiving the second portion of the combined light reflected from a second cavity of the second Fabry-Perot interferometer into a second optical detector through an optical path including a lens or a mirror and a second Fizeau interferometer; and analyzing data received by the first optical detector and the second optical detector to calculate a temperature value and the physical parameter of interest. The physical parameter of interest is pressure.

10. The method of claim 9, wherein, A numerical method is used to measure a first dimension of a first cavity of the first Fabry-Perot interferometer and to measure a second dimension of a second cavity of the second Fabry-Perot interferometer by detecting maxima of a destructive interference pattern of the combined light generated along first and second optical circuits.

11. The method of claim 9, further comprising: A numerical method is used to detect and track the maxima of the destructive interference pattern based on pixel intensity of a linear or matrix light detector, wherein interference peak information is combined with geometry of the first and second Fizeau interferometers to calculate the first and second dimensions.

12. The method of claim 11, further comprising: A Fourier transform of an interference spectrum is calculated to determine a change in the dimension of the first cavity of the first Fabry-Perot interferometer.

13. The method of claim 9, further comprising: The second dimension is converted to a temperature measurement using physical properties of the second cavity and the first dimension is converted to a measured physical parameter using physical properties of the first cavity and the temperature measurement.

14. The method of claim 11, further comprising: Demodulation is used to remove non-uniform illumination of the first optical detector and a low-pass filter is used to remove electro-optical noise.

15. The method of claim 9, further comprising: Analogous to annealing search or sub-pixel interpolation is used to detect and track peaks of destructive interference.

16. The method of claim 9, further comprising: A fast Fourier transform of a spectrum of a fringe pattern is calculated and analyzed and intensities of the first and second narrowband light sources are balanced over an entire temperature range.

17. The method of claim 9, further comprising: A interrogator is calibrated to measure a cavity dimension of the first Fabry-Perot interferometer independently of the Fabry-Perot interferometer.

18. The method of claim 9, further comprising: A physical parameter of a second transducer is stored in the interrogator.

19. The method of claim 18, further comprising: Temperatures in an optical emission module and an optical detection module are measured using sensors and temperatures in the optical emission module and the optical detection module are actively controlled using thermoelectric coolers or Peltier elements.

20. The method of claim 9, further comprising: ​

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