Optoelectronic system for measuring physical parameter

Abstract

To provide an optoelectronic system for measuring a physical parameter under a severe environment.SOLUTION: An optoelectronic system comprises: a light emitting module including a first light source, a second light source, and an optical coupler that couples light from the first light source and light from the second light source to an optical fiber, wherein the light sources and the optical fiber are coupled to a first mounting baseplate; a light detection module that receives light from the optical fiber and splits the light into a first portion directed to a first sensor and a second portion directed to a second sensor, wherein each portion includes light from the first light source and light from the second light source, and wherein the first sensor, the second sensor, and one or more spectrometers are coupled to a second mounting baseplate; a housing, a chassis, and a baseplate that enclose the light emitting module and the light detection module; a shock absorber coupled to the chassis; a first or second thermoelectric cooler that enables heat transfer between the light emitting module and the housing or between the detection module and the housing; and one or more transducers optically coupled to the light detection module.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 942,064, filed November 29, 2019, which is incorporated by reference in its entirety and is hereby made a part of this specification.

[0002] This patent document relates generally to optical sensors. More particularly, the subject matter of this patent document relates to optical sensors for use in aircraft engines, land-based turbines such as gas turbines or steam turbines, or any electrical generator having a combustion chamber. [Background technology]

[0003] Fiber optic sensing technology offers several advantages over traditional electrical sensing techniques for monitoring and controlling physical parameters of machines such as aircraft engines, land-based turbines like gas or steam turbines, or any generator with a combustion chamber. In particular, the following advantages have been demonstrated: (i) improved measurement accuracy and bandwidth; (ii) inherent insensitivity to external perturbations, i.e., electromagnetic and radio frequency interference; (iii) long- to ultra-long-range measurements with negligible signal attenuation; (iv) distributed sensing: the possibility of multiplexing many individually addressed point sensors; and (v) compatibility with high to very high temperatures. Therefore, replacing electrical sensors with fiber optic sensors is desirable for many applications, especially aerospace applications. Summary of the Invention [Problem to be solved by the invention]

[0004] Among aerospace applications, aircraft engines require 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, alerting pilots if an unsafe condition occurs or alerting ground maintenance if the engine needs to be overhauled. In current aircraft engines, all sensors are based on electrical operating principle technologies, such as piezoelectric, piezoresistive, or capacitive measurement principles. For each individual sensor, an electrical readout signal is transmitted via electrical wires connected to the engine's electronic unit. These discrete outputs lead to long cable harnesses with multiple connectors, adding complexity to the engine architecture and significantly increasing weight and engine fuel consumption.

[0005] One specific application is measuring the pressure between the final stage of an engine's high-pressure compressor and the combustion chamber. The measurement output is used in a control loop for engine operation. To date, no invention has been shown to be able to reliably measure absolute (static) pressure at temperatures exceeding 300°C during operation, and certainly none can handle temperatures exceeding 400°C or 500°C. Therefore, engine control relies on a low-temperature pressure sensor located on an electronics unit mounted in the engine's fan case, the engine's coldest temperature zone (typically its maximum operating temperature between 80°C and 125°C). This configuration requires a pressure pipe to run from the combustion chamber to the sensor, compensating for temperature differences in the measurement. Furthermore, under certain environmental conditions, the measurement can be unstable. One objective of the present invention is to measure pressure directly within the engine core, eliminating the pressure pipe, reducing weight, and improving measurement accuracy. [Means for solving the problem]

[0006] An optoelectronic system for measuring a physical parameter is provided, which is particularly suited for measuring the physical parameter in harsh environments such as those found in engine compartments.

[0007] In a preferred embodiment, the optoelectronic system comprises an optical sensor including a first Fabry-Perot interferometer positioned to receive a first portion of the coupled light and exposed to temperature and the physical parameter of the subject, and a second Fabry-Perot interferometer positioned to receive a second portion of the coupled light and exposed to temperature but not the physical parameter of the subject.

[0008] 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 first Fizeau interferometer arranged to receive light reflected from a first cavity of the first Fabry-Perot interferometer at a first photodetector via an optical path including a coupler, lens, or mirror arranged to couple the first narrowband light source and the second narrowband light source into a combined light; a second Fizeau interferometer arranged to receive light reflected from a second cavity of the second Fabry-Perot interferometer at a second photodetector via an optical path including a lens or mirror; and a processor arranged to analyze data received by the first photodetector and the second photodetector and calculate values ​​of a temperature and a second physical parameter.

[0009] Although any physical parameter may be measured using the systems taught herein, in preferred embodiments, pressure and temperature are measured.

[0010] In some embodiments, the first light source and the second light source are part of a light emission module that is physically separate from the first Fizeau interferometer, the second Fizeau interferometer, the first photodetector, and the second photodetector that are present on the detection module. Together, the light emission module and the detection module comprise an interrogator. In still other embodiments, the components of the light emission module and the detection module may be combined into one module.

[0011] In preferred embodiments, the first and second Fizeau interferometers, the first and second photodetectors, and the optical elements are all mounted on a plate made from a material with a low coefficient of thermal expansion. In some embodiments, the coefficient of thermal expansion is less than 2×10 -6 / °C or less. In yet another embodiment, the coefficient of thermal expansion is 1×10 -6 / ℃ or less.

[0012] The optoelectronic systems taught herein are specifically designed for use in harsh environments. In particular, the systems taught herein are designed for use in turbofan engines. To this end, in some embodiments, an optical sensor is mounted to the engine core of the turbofan engine. In such embodiments, an interrogator may be mounted to the fan case of the turbofan engine and optically coupled to the optical transducer via at least one optical fiber.

[0013] In some embodiments, the first light source, the second light source, the first Fizeau interferometer, the second Fizeau interferometer, the first photodetector, and the second photodetector are all sealed in a metal box with a controlled internal atmosphere using air, vacuum, or an inert gas.

[0014] In another aspect of the present invention, a method for detecting a physical parameter in a harsh environment using an optical sensor is provided. In a preferred embodiment, the method includes combining 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 generate combined light, receiving a first portion of the combined light with a first Fabry-Perot interferometer, exposing the first Fabry-Perot interferometer to temperature and a second physical parameter, receiving a second portion of the combined light with a second Fabry-Perot interferometer, exposing the second Fabry-Perot interferometer to temperature but not to the physical parameter of interest, and using a lens. receiving light reflected from a first cavity of the first Fabry-Perot interferometer at a first photodetector via an optical path consisting of a lens or mirror and a first Fizeau interferometer, receiving light reflected from a second cavity of the second Fabry-Perot interferometer at a second photodetector via an optical path consisting of a lens or mirror and a second Fizeau interferometer, and analyzing data received by the first photodetector and the second photodetector to calculate values ​​of a temperature and a second physical parameter.

[0015] Some embodiments of the method further include using a numerical method to measure 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 a maximum in a destructive interference pattern generated along a first optical circuit and a second optical circuit.

[0016] Additionally, in other embodiments, the method further includes using a numerical method to detect and track maxima of the destructive interference pattern based on pixel intensities of a linear or matrix photodetector, where 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.

[0017] In some embodiments, the method further comprises calculating a Fourier transform of the interference spectrum to determine a change in a dimension of the first cavity of the first Fabry-Perot interferometer.

[0018] In some embodiments, the method further includes converting the second dimension into a temperature measurement using a physical property of the second cavity, and converting the first dimension into a measured physical parameter using a physical property of the first cavity and a temperature measurement.

[0019] Some methods further include using demodulation to remove uneven illumination of the first photodetector and using a low pass filter to remove electro-optical noise.

[0020] It further includes detecting and tracking destructive interference peaks using simulated annealing search or sub-pixel interpolation.

[0021] Additionally, in another embodiment, a Fast Fourier Transform of the spectrum of the fringe pattern is calculated to balance the intensities of the first narrowband light source and the second narrowband light source over a temperature range, such that equal light from each of the two light sources reaches the photodetector.

[0022] In some embodiments, the method further includes calibrating an interrogator to measure a cavity dimension of the first Fabry-Perot interferometer independently of the second Fabry-Perot interferometer, and in such embodiments, the physical parameters of the second transducer may be stored in the interrogator.

[0023] Each of the various aspects described above, together with those summarized above and described in connection with the embodiments disclosed herein, can be used in combination to form a claim directed to an apparatus, system, method of manufacture, or use in any manner disclosed herein, without limitation.

[0024] These and other features, aspects, and advantages are described below with reference to the drawings, which are intended to illustrate, but not limit, the invention, in which like reference characters indicate corresponding features consistently throughout like embodiments. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram showing a system overview of one embodiment of an optical sensor. [Figure 2] FIG. 2 is a schematic diagram of FIG. 1 showing the subcomponents of the optical integrator and optical transducer. [Figure 3] FIG. 3 is a diagram illustrating one embodiment of the optical sensor described in FIGS. 1 and 2 mounted on a turbofan engine. [Figure 4] FIG. 4 is a diagram illustrating typical lengths of system components of an optical sensor for a high bypass ratio turbofan engine. [Figure 5] FIG. 5 is a diagram illustrating a breakout cross section of one embodiment of an optical transducer for use with the optical sensors described herein. [Figure 6] FIG. 6 shows a schematic diagram of an extension cable for use with the optical sensor taught herein. [Figure 7] FIG. 7 illustrates an isometric view of one embodiment of an optoelectronic interrogator having a transparent housing. [Figure 8] FIG. 8 shows an exploded view of the optoelectronic interrogator of FIG. [Figure 9] FIG. 9 is a schematic diagram of the optical design and optical paths for one embodiment of an optical detection module and an optical emission module for use with the optical interrogator disclosed herein. [Figure 10] FIG. 10 is a schematic diagram of how the system uses multiplexing to use one interrogator for multiple sensors. [Figure 11]FIG. 11 is a block diagram of one embodiment of an optoelectronic interrogator LRU that is sub-modularized according to system needs. [Figure 12] FIG. 12 is a block diagram of one embodiment of an architecture for CPM. [Figure 13] FIG. 13 is a block diagram of one embodiment of the OIM architecture. [Figure 14] FIG. 14 is a schematic diagram of one embodiment of a thermal control layer of an OIM. [Figure 15] FIG. 15 is the expected fringe interference pattern with the point of maximum destructive interference on the identified pattern. [Figure 16] FIG. 16 illustrates a fringe interference pattern with (i) geometric and fiber optic effects that result in a "bell" modulation on the fringe shape, and (ii) electro-optic noise. [Figure 17] FIG. 17 is a block diagram of an example of system signal processing for calculating and correcting pressure measurements. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention is an optical fiber sensing system that alleviates problems associated with harsh machine environments, such as those described in the background. The system herein is particularly adapted for use in harsh environments. While a harsh environment can be any hostile environment, as used herein, harsh environments typically refer to environments found within aircraft engines. Thus, depending on the measurement type, interrogator temperatures range from -40°C to 80°C or -55°C to 125°C, while transducer temperatures range from -55°C to 700°C and above. These temperatures are coupled with severe vibrations. In one embodiment, the system is designed for static pressure measurements 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 readout and processing in a single optoelectronic interrogator or multiplexing the outputs of multiple sensors over a single fiber, the engine sensing architecture can be significantly simplified and significantly lighter than electrical systems.

[0027] (System Description) The following describes one exemplary embodiment for measuring pressure and temperature within the high-temperature core of an aircraft turbofan engine. Alternative embodiments can be adapted to other machines, such as those described in the background section, or can be used in any high-temperature environment, especially those previously limited to electrical sensors. By way of example only, the sensing system herein may be used on a hydrogen-powered engine. In other embodiments, the same system definition may be used to measure additional parameters, such as temperature, mechanical displacement, mechanical stress, vibration, acceleration, rotational speed (e.g., of a shaft), clearance, open / closed state (e.g., of a valve), gas flow rate, and other physical parameters used to control the operation of or monitor the condition of the machine.

[0028] Figure 1 is a schematic diagram showing a system overview of one embodiment of an optical sensor 10. As can be seen in Figure 1, the optical sensor 10 may be composed of three subsystems: an optoelectronic interrogator 12, an optional optical extension cable 14, and an optical transducer 16. These subsystems are connected to each other so that optical signals are exchanged between them via optical fibers, as shown in Figure 1. The optical extension cable 14 can be removed if the integral cable 16A of the optical transducer 16 is connected directly to the optoelectronic interrogator 12.

[0029] Figure 2 is a schematic diagram of the optical sensor 10 of Figure 1, showing the subcomponents of the optical interrogator and optical transducer. The optoelectronic interrogator 12 includes a light source 20, an optical module 21, a digital processing unit 22, a communications unit 23, and a power management unit 24. An optical extension cable 14 houses and protects at least two optical fibers connecting the optoelectronic interrogator 12 to the optical transducer 16. The optical transducer 16 consists of two pressure and temperature sensor elements 31 and 32. Each sensor element contains a Fabry-Perot interferometric cavity sensitive to the physical parameter being measured. Both elements are connected to optical fibers protected by an integral cable 33.

[0030] In a preferred embodiment, the system 10 is mounted on an aircraft turbofan engine 30. Figure 3 shows one embodiment of an optical sensor such as that described in Figures 1 and 2 mounted on a turbofan engine. The optoelectronic interrogator 12 is mounted on the exterior portion of the fan case of the engine 30, close to the engine's other electronic units, in a location on the engine where temperatures are reasonably low (maximum temperatures are typically between 80°C and 125°C, or even higher depending on the engine). The interrogator 12 is connected to an optical extension cable 14 routed to the engine hot zone, where ambient temperatures are typically between 125°C and 250°C. The end of the optical extension cable 14 links to an optical transducer 16. The transducer 16 is mounted in the engine core so that it can sense the pressure and temperature of the engine air in the high-pressure compressor, combustion chamber, and turbine zones, where temperatures can exceed 300°C, 400°C, or 500°C.

[0031] In FIG. 3 , the transducer(s) are mounted to the engine core, but in other embodiments, the transducer(s) may be mounted elsewhere. Typical transducer mounting locations may be, but are not limited to, locations where current pressure and temperature sensors are mounted (the optical transducer would replace conventional pressure and temperature sensors in the general areas described above). The transducer body 16 would typically be secured to an engine mounting structure such as the compressor case (high-pressure compressor side), combustion case, or turbine case. The transducer head (the area beyond the flange 40 to the end of the radiation shield 43) would itself be directly immersed in the airflow via associated piping or a direct plug in the case.

[0032] 4 shows some typical lengths of system components in an optical sensor for a high bypass ratio turbofan engine. It may be understood that these dimensions are for reference to a particular embodiment, and other embodiments may use different lengths for the same type of engine or for different types of engines or other devices.

[0033] During operation, the interrogator 12 sends an optical signal to the optical transducer 16 via optical extension cables 14 and 16a. The light is modulated as a function of the applied external pressure by a Fabry-Perot cavity embedded in the pressure sensor element 16. The reflected optical signal is analyzed by the optoelectronic interrogator 12. The pressure is then calculated via the processing unit of the interrogator 12. Temperature is measured in a similar manner and used to compensate for the effects of temperature fluctuations in the sensing element. Both temperature and pressure data are then digitally output to other engine electronic units.

[0034] (Optical Transducer Design) FIG. 5 is a breakout cross-sectional view of one possible embodiment of an optical transducer 16 for use with the optical sensor 10 described herein. The optical transducer consists of fiber optic Fabry-Perot temperature and pressure sensing elements 41, 42. As can be seen in FIG. 5, both the temperature sensor 41 and the pressure sensor 42 are located at the tip of the transducer 16. In the embodiment shown in FIG. 5, the pressure sensor 42 is located directly in front of the temperature sensor 41. They are housed within compartments created within the hollow body of the tip of the transducer. Each of the Fabry-Perot temperature sensor 41 and the pressure sensor 42 has a cavity 45.

[0035] In a preferred embodiment, the sensor elements 41, 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. The housing 40 of the transducer 16 is preferably made of stainless steel (AISI316L) or a nickel-based superalloy, depending on the application. A specific radiation shield 43 made of a nickel-based superalloy is assembled to the end of the transducer 16. During the fabrication process, a vacuum is applied to the internal volume of the housing 40 and an inert gas is introduced.

[0036] (Extension cable design) Figure 6 is a schematic diagram of an extension cable 14 for use with the optical sensor 10 taught herein. The optical extension cable 14 connects the optical transducer 16 and the optoelectronic interrogator 12. In a preferred embodiment, the optical extension cable 14 incorporates two optical fibers and can accommodate electrical wires, depending on the system configuration. 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. The PTFE sleeve provides protection from all aggressive fluids. Therefore, the optical fiber itself is not exposed to any mechanical forces or contaminants. To operate in the preferred application, the optical cable 14 must withstand temperatures exceeding those of its warmest end (i.e., the connection to the optical transducer, typically 150°C to 250°C).

[0037] In a preferred embodiment, and depending on the application, the optical extension cable is approximately 5 meters long and each connector is approximately 79 mm long. As will be appreciated by those skilled in the art, these dimensions may be varied without departing from the scope of the present invention and are provided as a reference embodiment only.

[0038] (Optoelectronic Interrogator Design) The optical-electronic interrogator 12 is preferably designed to be a line replaceable unit (LRU). In a preferred embodiment, the optical-electronic interrogator 12 is designed to be mounted to the engine fan case, as shown in Figure 3. In other embodiments, the optical interrogator electronic and optical module (without packaging) can be implemented directly into an existing engine electronic unit (e.g., FADEC, EMU, etc.).

[0039] Figure 7 is an isometric view of one embodiment of an optoelectronic interrogator 12 having a transparent housing 50. The interrogator housing 50 is comprised of a chassis 51, a center frame 52, and a cover plate 53. In the preferred embodiment, the entire housing 50 is constructed from a black anodized aluminum alloy. In the embodiment shown in Figure 7, the chassis 51 has four legs and a mounting adapter 54 that secure the unit onto the engine and include custom shock absorbers to dampen engine vibrations.

[0040] In some embodiments, the optical module is sealed in a metal or plastic box with a controlled internal atmosphere using air, vacuum, or inert gas, hi other embodiments, the complete optoelectronic interrogator box is sealed.

[0041] FIG. 8 is an exploded view of the optoelectronic interrogator 12 of FIG. 7. In a preferred embodiment of the optoelectronic interrogator 12, all electronic boards, connectors, and optical modules are assembled on a central frame 52. Furthermore, in a preferred embodiment, the central frame 52 is formed as a single unit. This architecture is particularly well suited for high-vibration environments and provides great flexibility in configuring the system. For example, additional frames can be assembled on top of the first frame without compromising the robustness of the system. This configuration provides flexibility to add functionality or sensing channels to the system depending on the application requirements.

[0042] The interrogator 12 includes a light source, a light detection module, a multiplexing stage, a temperature control stage, a central processing module (CPM) electronics board, and an optoelectronic interrogator module (OIM) electronics board.

[0043] In a preferred embodiment, the optical detection module and the optical emission module are physically separated within the interrogator 12. By "physically separated" it is meant that at least two are mounted on different mounting base plates. In a preferred embodiment, physically separated may also mean that they are mechanically separated from each other using dampers or other mechanical separation means.

[0044] (Optical module) FIG. 9 is a schematic diagram of the optical design and optical path of 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 in the optical interrogator 12 consists of an optical circuit assembly enclosed in a pressure-tight box. The optical circuit consists of discrete passive optical (or micro-optical) and optoelectronic components, such as filament 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 positioned and fixed on a low-thermal expansion base plate attached to the base plate of the box. Optical fibers are coupled to the system for external optical communication. Alternatively, some or all of the functions of the discrete optical elements can be integrated onto a photonic integrated circuit (photonic chip).

[0045] The light emitting module 61 includes one or more LEDs 62, depending on the application. In a configuration including two LEDs 62, the central emission wavelengths are selected to maximize the effect of destructive interference as measured by the light 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 combined in an optical fiber using an optical coupler 63.

[0046] The optical detection module 60 has two main functions. First, it collects light from the emission module 61 and splits the light via an optical coupler or splitter 64 for distribution to one or more transducers 66, 67. Second, it collects and analyzes the optical signal reflected from the Fabry-Perot cavities of the transducers 66, 67. This signal traverses the same optical splitter 64 as for emission. However, in this case, the light is directed to an optical analysis system 68. This optical analysis system 68 consists of a series of lenses and mirrors to shape the light beam. In a preferred embodiment, the mirrors or lenses in the optical path are designed to improve the uniformity of the distribution of light intensity across the Fizeau wedge 69.

[0047] The final optical element is a cylindrical mirror or lens that reflects the light beam towards an optoelectronic detector 70. Mounted in front of the detector 70 is a Fizeau interferometer 69. This fixed and stable interferometer 69 has well-known properties such that by cross-correlation of the signal coming from the sensor with its own sign in the Fizeau interferometer 69, the size of the Fabry-Perot cavity of the transducers 66, 67 can be inferred.

[0048] (Multiplexing) Figure 10 is a schematic diagram of how the system may be multiplexed to use a single interrogator 12 with multiple sensors. This system design provides the opportunity to measure one or more Fabry-Perot sensing elements. As mentioned above, the system uses a single source module that can be split and sent to multiple sensors. This method allows for the interrogation of multiple sensing elements using the same optoelectronics, based on multiplexing methods such as time multiplexing, spatial multiplexing, and wavelength multiplexing.

[0049] (Electronic Unit) Figure 11 shows a block diagram of one embodiment of an optoelectronic interrogator LRU, submodularized according to system needs. This is the electronic portion of the interrogator, and this LRU is broken down into two subsystems. The first subsystem is a standardized motherboard assembly 72 called the Central Processing Module (CPM) 72, which consists of: 1) a processing layer that hosts the software (SW) and programmable logic; 2) a communications layer for interfacing with other LRUs 73; 3) a configurable acquisition controller for pressure and temperature data; and 4) a power management and power conversion layer 74.

[0050] The second subsystem is an optoelectronic interrogator module (OIM) 80 consisting of: 1) at least two optical modules 81, 2) a configurable power supply 82 for the light source, 3) configurable acquisition interfaces 83, 84 for temperature and pressure signals, and 4) a thermal management layer 85.

[0051] The LRU can be alternatively modularized depending on system requirements thanks to the modular and scalable features of the system. For example, additional acquisition modules can be added to expand acquisition functionality without modifying existing subsystems or housing components.

[0052] (Central Processing Module (CPM)) Figure 12 shows a block diagram of one embodiment of the architecture of the CPM72. At the heart of the CPM72 is an all-programmable system on a chip (SoC) that contains a central processing unit (CPU) to host specific SW applications and programmable logic (or FPGA) to achieve high flexibility by providing the ability to connect to many different peripherals with just a reprogramming.

[0053] The CPU and programmable logic provide the processing functions for the system as well as the functionality to support various communication interfaces. Alternatively, all of the processing functions of the CPM can be handled by the FPGA without using the CPU.

[0054] A communications layer is provided to enable communication with other LRUs and ground stations. In this embodiment, the LRU provides Airlink-429, Ethernet, and RS-232 interfaces. Alternate and additional interfaces (e.g., CAN, RS-422, RS-485, etc.) can be provided by replacing line-removable submodules in the CPM72.

[0055] In a preferred embodiment, the CPM 72 includes a mezzanine connector that provides communication, control, and feedback signals available to any other subsystems of the LRU, providing a truly 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 thermal management of the system. The CPM 72 also includes a power management layer 74 to interface with the aircraft's power inputs and provide regulated power to the other subsystems of the LRU.

[0056] (Optical Interrogator Module (OIM)) FIG. 13 is a block diagram of one embodiment of the OIM architecture 80. The OIM 80 of FIG. 13 is comprised of temperature and pressure signal conditioning and acquisition interfaces 83, 84 coming from the light detection module 81. It allows the CPM 72 to independently control the acquisition parameters of each input signal. This includes independent control of the gain and sampling frequency of each individual channel. Two independent current sources power the light sources of the light emission module 81. The CPM 72 dynamically adjusts the current supplied to each light source as a function of internal parameters, such as the temperature of internal components or the actual light intensity received by the light detection module 81. Multiple temperature sensors 85 are also provided to monitor and report temperature values ​​of various system components to the CPM 72. This temperature data can include substrate temperature, CCD temperature, LED temperature, and any other temperature data within the OIM 80 that may be useful to the CPM 72. The temperature data from the OIM 80 can be used to further correct for potential component variations when exposed to temperatures different from room temperature.

[0057] (heat regulation design) To mitigate temperature-dependent variations in optical element characteristics, particularly loss of optical power at high temperatures, the OIM 80 implements a thermal management layer. This consists of active temperature control of the optical modules. The temperatures of the optical emission and detection modules are measured by temperature sensors and controlled by thermoelectric regulators. Figure 14 is a schematic diagram of one embodiment of the thermal control layer 85 for the OIM 80. Cooling or heating of the optical elements is achieved using thermoelectric coolers 91, 92 (TEC or Peltier elements). A TEC 91 is attached to the emission module 61, and a separate TEC 92 is attached to the optical detection module 65. These pump heat from the elements and reject it to a heat sink. The LRU housing 50 is used to absorb heat and act as a heat sink, allowing the heat to be rejected outside the LRU. This embodiment is preferable to using a standard heat sink placed within the LRU, as this results in a larger increase in internal temperature. Conversely, the TECs 91, 92 can be used to heat the modules if desired. A temperature sensor is attached to the module and measures its temperature, allowing the TEC controller to adjust the power supplied to the TECs 91, 92 as a function of temperature. The temperature information of the optoelectronic elements can be used to correct for thermal effects / shifts on the output signal during digital processing of the data (if not thermally regulated or if partially thermally regulated).

[0058] (Signal Processing) The location of the fringe interference minimum, as read by the photodetector, is directly correlated with the dimensions of the transducer's Fabry-Perot cavity. The exposed pressure and temperature stimuli may then be reconstructed from this information. The goal of processing is to identify the maximum destructive interference signal. Figure 15 shows the expected fringe interference pattern with the maximum destructive interference point on the identified pattern.

[0059] Interference is not the only actor that determines the signal shape. Two other effects can influence the signal shape. Figure 16 illustrates a fringe interference pattern: (i) geometric and fiber optic effects that result in a "bell" modulation on the fringe shape, and (ii) electro-optic noise. Both effects must be removed or compensated for for proper detection.

[0060] FIG. 17 is a block diagram of an example of system signal processing for calculating and correcting pressure measurements. The input to the processing is the optical interference signals (e.g., temperature and pressure) acquired by the photodetector 102, one for each channel. The intermediate output blocks 103-106 are measurements of the two cavity dimensions. As previously explained, these are sent to respective conversion blocks 107 to generate measurements of temperature and first estimates of pressure. These estimates are then converted to final values ​​in the temperature correction block 108. The noise cancellation block consists of a low-pass frequency FIR filter. The low-pass cutoff frequency is correlated with the fringe period of the interference pattern. Bell demodulation consists of a high-pass filter implemented via averaging subtraction. The magnitude of the averaging is determined by the interference pattern fringe period.

[0061] The point of maximum destructive interference (minimum of the fringe signal) is determined on the filtered / demodulated signal. The search strategy consists of searching for a local minimum around the tracked position in time. The discovery of a false minimum (e.g., a noise peak on a local extremum) is mitigated by implementing a minimum hopping strategy controlled by threshold annealing. Once identified, standard parabolic subpixel interpolation of the pixel position is implemented to improve the accuracy of the results.

[0062] Once the pixel minimum position (called pixel index) is determined with sub-pixel accuracy, it is converted to the corresponding Fabry-Perot cavity dimension in nanometers using a Fizeau wedge lookup table determined by forward calibration. Other lookup tables representing the cavity's physical properties as a function of temperature (thermal coefficients and membrane sensitivity) allow the conversion from cavity dimension to pressure measurement.

[0063] For these purposes, the processor uses a numerical method to measure the dimensions of each of the two Fabry-Perot cavities by detecting maxima in the destructive interference pattern generated along each of the two optical circuits. The processor detects and tracks maxima in the destructive interference pattern generated by the optical circuits based on pixel intensities of a linear or matrix photodetector. This method combines the interference peak information with the geometry of the Fizeau interferometer to calculate the Fabry-Perot cavity dimensions. The processor can further convert the second Fabry-Perot cavity dimensions to temperature using physical properties of the second Fabry-Perot cavity. The first Fabry-Perot cavity dimensions are converted to a measured physical parameter (e.g., pressure) using the physical properties of the first cavity and the temperature measurement of the second cavity.

[0064] In another embodiment, the processor calculates a fast Fourier transform (FFT) of the interference spectrum to determine the change in the dimension of the Fabry-Perot interferometer.

[0065] In some embodiments, the processor uses numerical methods to calculate and analyze the FFT of the spectrum of the fringe pattern to balance the intensities of the two light sources over a temperature range. The FFT information of the interference pattern can additionally be used to continuously determine the integrity of the optical circuit (Built-In-Test - BIT).

[0066] Finally, in some embodiments, the system is calibrated in such a way that the interrogator and transducer are interchangeable. The interrogator is calibrated to measure the dimensions of the Fabry-Perot cavity independently of the transducer. The physical parameters of the transducer are stored in the interrogator, which converts the Fabry-Perot cavity dimensions into measured physical parameters (e.g., pressure).

[0067] (Optoelectronic component control) To improve the measurement capability, balancing control of the light source and CCD levels has been introduced. If the control fails to achieve a predefined condition, a fault signal is sent to the BIT (Built-In Test) block. The BIT detects and classifies various faults in the optical circuit, such as saturation of the temperature or pressure CCD, low signal of the temperature or pressure CCD, low level of Light Source 1 or Light Source 2, or other light sources.

[0068] First, the system verifies that the CCD is operating properly by analyzing pixel-level values. Saturation and low-light conditions are determined based on the maximum and average pixel values, respectively. In the case of saturation, the CCD integration time is decreased until saturation is eliminated. In the case of low light, the CCD integration time is increased until the average value reaches an acceptable condition. If these conditions are not met, a signal is sent to the BIT.

[0069] If the CCDs are operating within a predetermined acceptance range, the signals of those CCDs are analyzed independently. For each CCD, the interference signal is Fourier transformed to identify two local peaks in the spectrum. Each local peak corresponds to the contribution of an individual light source. The detection of the local peaks involves determining the corresponding light source peak wavelength λ, the Fizeau interferometer slope α, and the CCD pixel size P. size It operates over a range centered on a frequency F determined by F=tg(α)*P size / λ

[0070] For each CCD, if the difference between the two peak values ​​is less than a predefined threshold, this means the source levels are sufficiently balanced. If not, the current to the source corresponding to the weak peak is increased and the current to the source corresponding to the strong peak is decreased until the levels of the two peaks reach a predefined acceptable level. If the acceptable level cannot be reached, a signal is sent to the BIT.

[0071] Generally, this patent document only discusses the use of Fabry-Perot interferometers, but other sensors may also be used, for example, fiber Bragg grating (FBG) based sensors.

[0072] While various inventive aspects have been disclosed herein in the context of certain preferred embodiments, embodiments, 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 or uses of the invention, as well as obvious modifications and their equivalents. Moreover, while several variations of inventive aspects have been shown and described in detail, other modifications within the scope thereof will be readily apparent to those skilled in the art based on this disclosure. It should also be understood that the scope of the present disclosure includes various combinations or subcombinations of the specific features and aspects of the embodiments disclosed herein, and that various features, embodiments, and aspects of such disclosed subject matter may be combined with or substituted for one another. Accordingly, it is intended that the scope of the invention disclosed herein should not be limited by the particular disclosed embodiment or embodiments described above, but should be determined solely by a fair reading of the claims.

[0073] Likewise, this disclosure is not to be interpreted as reflecting an intention that any claim require more features than are expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of a single foregoing disclosed embodiment. Accordingly, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment.

[0074] Furthermore, all claim terms should be interpreted in the broadest possible manner so that the applicant can have the broadest scope legally permitted. While the embodiments have been described with reference to drawings and specific examples, those skilled in the art will readily appreciate that many modifications and adaptations of the processes, methods, and apparatus described herein are possible without departing from the spirit and scope of the embodiments as described herein. Accordingly, it will be clearly understood that the present specification has been made by way of example only, and not as a limitation on the scope of the embodiments as claimed below. [Explanation of symbols]

[0075] 10 Optical sensors, systems, 12 Optoelectronic interrogator, interrogator, optical interrogator 14 Optical cables, extension cables, optical extension cables 16 Optical transducer, transducer 16 Pressure sensor element, transducer body 16A integrated cable 20 light source 21 Optical Module 22 Processing 23 Communications 24 Power supply 30 engine, aircraft turbofan engine 31 Pressure sensor element 32 Temperature sensor element 33 Integrated cable 40 Housing 40 flange 41 Temperature sensor element 42 Pressure sensor element 43 Radiation Shield 45 cavity 50 LRU housing 51 chassis 52 Center Frame 53 Cover plate 54 Mounting adapter 60 Photodetection Module 61 Light-emitting module 62 LED 63 Coupler 64 Splitter 65 Detection Module 66 Pressure Sensor 67 Temperature Sensor 68 Optical Components Lenses / Mirrors (Optical Analysis Systems) 69 Fizeau wedge, Fizeau interferometer 70 Photoelectron Detector 72 Central Processing Module, Motherboard Assembly 74 CPM power management, power conversion layer, power management layer 80 OIM Architecture 81 Optical modules, photodetection modules, light-emitting modules 82 OIM Power Management 83 Temperature control and acquisition 84 Pressure adjustment and acquisition 85 Thermal management layer, temperature sensor, temperature control layer 91, 92 Thermoelectric cooler 102 Photodetector 103 Noise Cancellation 104 Demodulation 105 Minimum Value Determination 106 Minimum Tracking 107 Length-pressure conversion, length-temperature conversion, pressure conversion block 108 Temperature Compensation Block

Claims

1. 1. An optoelectronic system for measuring a physical parameter, comprising: a light emitting module including a first light source and a second light source, and an optical coupler arranged to couple light from the first light source and light from the second light source into an optical fiber, the first light source, the second light source, and the optical coupler being coupled to a first mounting base plate; a light detection module including a first sensor, a second sensor, and one or more splitters configured to receive light from the optical fiber and split the light from the optical fiber into a first portion directed to a first sensor and a second portion directed to a second sensor, both of which contain light from the first light source and the second light source, and the first sensor, the second sensor, and one or more spectrometers coupled to a second mounting base plate that is physically separated from the first base plate; a housing, a chassis, and a base plate arranged to be coupled together and enclose the light-emitting module and the light-detecting module therein; a plurality of shock absorbers coupled to the chassis; a first thermoelectric cooler disposed to enable heat transfer between the light emitting module and the housing; a second thermoelectric cooler positioned to allow heat transfer between the detection module and the housing; one or more transducers optically coupled to the light detection module; An optoelectronic system comprising:

2. The optoelectronic system of claim 1 , further comprising a central frame, the light emitting module and the light detecting module being coupled to the central frame.

3. 2. The optoelectronic system of claim 1, wherein the light emitting module comprises a first Fabry-Perot interferometer and a second Fabry-Perot interferometer.

4. 10. The optoelectronic system of claim 1, wherein said first light source and said second light source are narrow band.

5. 10. The optoelectronic system of claim 1, wherein the one or more transducers include a pressure sensor element and a temperature sensor element.

6. 2. The optoelectronic system of claim 1, wherein the first light source has a first peak frequency and the second light source has a second peak frequency different from the first peak frequency.

7. 10. The optoelectronic system of claim 1, further comprising a processor arranged to analyze data received by the first and second sensors and calculate temperature and pressure values.

8. 10. The optoelectronic system of claim 1, wherein said one or more transducers are mounted to an engine core.

9. The optoelectronic system of claim 8, wherein the engine is a turbofan engine.

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