Low-cost sensing system using functionalized fiber and transimpedance amplifier with wireless interrogation

Abstract

The fiber optic sensing system and method includes a functionalized fiber optic sensor including a designed sensing layer, a light source configured to generate light and couple the light to an input of the functionalized fiber optic sensor, and an interrogator including a photodetector coupled to the functionalized fiber optic sensor to receive transmitted or reflected light, a transimpedance amplifier (TIA) circuit coupled to an output of the photodetector, a controller coupled to an output of the TIA circuit, and a transmitter (e.g., a wired or wireless transmitter) coupled to the controller.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 63 / 306,330, filed February 3, 2022, entitled "Low-Cost Sensing System Based on Functionalized Fiber and Transimpedance Amplifier Circuit with Wireless Interrogation Capability," the disclosure of which is incorporated herein by reference.

[0002] The present invention relates to sensing systems for detecting various parameters (such as, but not limited to, temperature, gas concentration, or magnetic field levels) in industrial / commercial or residential systems / environments, and more particularly to sensing systems utilizing functionalized optical fiber based sensors and transimpedance amplifier circuitry with wireless interrogation capability to measure one or more parameters of interest. [Background technology]

[0003] Temperature monitoring has become a vital component for both optimizing the normal operation of power equipment and detecting potential failures. In addition to thermal monitoring, gas phase chemistry within electrical assets (including above or in the insulating oil, in battery cells, near insulating paper, etc.) can also provide early indicators of asset health. For this reason, dissolved gas analysis sampling and real-time monitoring is commonplace in today's large power transformers. Finally, there is also interest in monitoring electrical parameters such as magnetic and electric fields to allow direct measurement of power flow in the form of current or stored charge within an asset or electrical system. It is well-known that fiber optic sensors overcome the challenges of traditional electrical sensors posed by the compact, chemically harsh, and electromagnetic interference conditions of electrical assets. These advantages of fiber optics enable internal measurements with high sensitivity and more accurate results.

[0004] Previously, fiber Bragg Grating (FBG) sensors and Fabry-Perot interferometers have been embedded in Li-ion cells to probe the internal temperature rise during charging / discharging. The internal measurements reduce the uncertainties associated with estimating the internal state of the battery, thus avoiding oversizing of the battery module and maximizing the useful capacity of a single cell. Besides point temperature sensing, thermal mapping at module level has also been demonstrated using quasi-distributed FBG networks to identify anomalous hot spots that may be the cause of thermal runaway. However, the fabrication of FBG sensors requires expensive equipment such as excimer lasers and CO2 lasers, making the cost of this kind of sensor relatively high.

[0005] In addition, the cost of optical interrogation systems is substantial due to the need for good wavelength resolution of the detector and narrowband high intensity light source at tuned wavelength. Meanwhile, distributed fiber temperature sensors, such as optical frequency domain reflectometry (OFDR) based on Rayleigh backscattering, have been deployed to monitor the internal temperature distribution of utility power transformers. However, existing fiber optic technologies for both distributed and quasi-distributed fiber sensors are economically burdensome due to the high manufacturing costs of the sensors and the need for expensive interrogation systems, which may inhibit their adoption except for very expensive assets and systems. For example, the cost of these distributed / quasi-distributed interrogators typically ranges from $15,000 to $50,000. Justifying these costs for low and medium voltage electrical assets is difficult. Unless utility-scale energy systems support extremely large capital investments and can spread the costs over a large number of spatially distributed sensing points, this is highly unlikely given the economic and regulatory realities within the power transmission and distribution system. Summary of the Invention

[0006] In one embodiment, a sensing system includes a functionalized optical fiber sensor including an engineered sensing layer, a light source configured to generate light and couple the light to an input of the functionalized optical fiber sensor, and an interrogator including a photodetector coupled to the functionalized optical fiber sensor to receive transmitted or reflected light, a transimpedance amplifier (TIA) circuit coupled to an output of the photodetector, a controller coupled to an output of the TIA circuit, and a transmitter coupled to the controller.

[0007] In another embodiment, a method of fiber optic sensing is provided that includes generating and coupling incident light to an input of a functionalized fiber optic sensor that includes a designed sensing layer, receiving the transmitted or reflected light with a photodetector coupled to the functionalized fiber optic sensor, receiving an output of the photodetector with a TIA circuit, and generating and transmitting (e.g., wirelessly) a parameter signal indicative of a parameter being monitored by the functionalized fiber optic sensor based on and in response to the output of the TIA circuit. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a fiber optic sensing system according to an exemplary embodiment of the disclosed concepts.

[0009] [Figure 2A] FIG. 2A illustrates the optical temperature response of a particular exemplary embodiment of the disclosed concepts. [Figure 2B] FIG. 2B illustrates the optical temperature response of a particular exemplary embodiment of the disclosed concepts. [Figure 2C] FIG. 2C illustrates the optical temperature response of a particular exemplary embodiment of the disclosed concepts.

[0010] [Figure 3A] FIG. 3A is a schematic diagram of an example TIA circuit that may be used in conjunction with the disclosed concepts. [Figure 3B] FIG. 3B is a schematic diagram of an example TIA circuit that may be used in conjunction with the disclosed concepts. [Figure 3C] FIG. 3C is a schematic diagram of an example TIA circuit that may be used in conjunction with the disclosed concepts.

[0011] [Figure 4A] FIG. 4A is a schematic diagram of an example energy harvesting circuit that may be used in connection with the disclosed concepts. [Figure 4B]FIG. 4B is a schematic diagram of an example energy harvesting circuit that may be used in connection with the disclosed concepts.

[0012] [Figure 5A] FIG. 5A is a schematic diagram of an exemplary approach for self-collimation of an LED and coupling to a fiber optic member that may be employed in connection with the disclosed concepts. [Figure 5B] FIG. 5B is a schematic diagram of an alternative exemplary approach for self-collimation of an LED and coupling to a fiber optic member that may be employed in connection with the disclosed concepts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As used herein, the singular forms "a" and "the" include plural references unless the context clearly dictates otherwise.

[0014] As used herein, a description of two or more parts or components being "coupled" means that the parts are coupled or operate together, either directly or indirectly, i.e., through one or more intermediate parts or components, to the extent that a connection occurs.

[0015] As used herein, "directly coupled" means that two elements are in direct contact with each other.

[0016] As used herein, the term "several" means one or an integer greater than one (ie, a plurality).

[0017] As used herein, the term "controller" refers to a programmable analog and / or digital device (including its associated memory portion) that can store, retrieve, execute, and process data (such as software routines and / or information used by such routines), including, but not limited to, a field programmable gate array (FPGA), complex programmable logic device (CPLD), programmable system on chip (PSOC), application specific integrated circuit (ASIC), microprocessor, microcontroller, programmable logic controller, or other suitable processing device or apparatus. The memory portion may be any one or more of various types of internal and / or external storage media, such as, but not limited to, RAM, ROM, EPROM, EEPROM, FLASH, etc., which provide storage registers, i.e., non-transitory machine-readable media, for storing data and program code, such as an internal storage area of ​​a computer, and may be volatile or non-volatile memory.

[0018] As used herein, the term "engineered sensing layer" refers to a layer of material coupled to an optical fiber that has optical properties that depend on a parameter (e.g., temperature, gas concentration, magnetic field level, or some other external sensing parameter) that causes the intensity level change of an optical fiber-based sensor that includes the engineered sensing layer to vary depending on and in response to the level of the parameter. Such engineered sensing layers may include, but are not limited to, layers made of nanocomposite materials. Additionally, such sensing layers may include a localized surface plasmon resonance (LSPR) peak.

[0019] As used herein, the term "nanocomposite" refers to a multiphase solid material in which one of the phases has at least one dimension less than or equal to 100 nanometers (nm), such as, but not limited to, a bulk (e.g., oxide) matrix with a plurality of dispersed nanoparticles (e.g., Au nanoparticles).

[0020] As used herein, the term "nanoparticle" refers to an object that behaves as a whole unit with respect to transport and properties and has a size (eg, diameter or width) in the range of 1 to 100 nm.

[0021] Directional terms used herein, such as top, bottom, left, right, upper, lower, front, back, and derivatives thereof, refer to the orientation of the elements illustrated in the drawings and do not limit the scope of the claims, unless expressly stated.

[0022] In the following, for purposes of explanation, the disclosed concepts are described in numerous specific details in order to provide a thorough understanding of the disclosed concepts, however, it will be apparent that the disclosed concepts can be practiced without these specific details without departing from the spirit and scope of the present invention.

[0023] As described in detail herein, the disclosed concepts provide cost-effective fiber optic sensors and simplified designs of interrogation systems employing the same. The fiber sensor is coated with one or more engineered sensing layers, such as layers made of plasmonic nanocomposite thin film materials in an exemplary embodiment. The fiber sensor is implemented in combination with a low-cost light source, such as a low-cost collimated LED, and is interrogated by a photodetector / transimpedance amplifier (TIA) / wireless communication circuit to measure the level of one or more parameters of interest (such as, but not limited to, temperature, gas concentration, magnetic field level, etc.). As two examples of existing wireless communication circuits, both nRF24L01+RF (along with an ATmega328P microcontroller) and LoRa RF chips / technology may be used as part of the wireless communication circuit. Of these two, LoRa RF has been proven by existing research to date to increase range capability and wireless transmission stability in terms of overcoming obstacles.

[0024] The low cost of the disclosed concept is made possible in an exemplary embodiment by the use of functionalized multimode silica fiber, off-the-shelf electrical component assembly circuitry on a printed circuit board (PCB), and the properties of the light intensity-based sensor that does not require a high wavelength resolution spectrometer. In addition to the cost advantage, the fiber interrogation system of the disclosed concept is compact using a PCB design and therefore can be easily adapted to commercial energy control systems such as battery management systems in electric vehicles or grid storage. The fiber sensor may be configured in a reflective sensing geometry as a temperature probe for ease of installation in the energy system. Another advantage is the wireless communication between the interrogator and the signal monitor, enabled by wireless communication hardware such as the nRF24L01+ or LoRa RF module, with communication distances up to 3 miles, making it ideal for remote monitoring of safety-conscious medium-voltage transformers and utility-scale energy storage devices. This can also be extended to cloud-based sensor data communication and analysis, such as a LoRaWAN gateway as an example.

[0025] Finally, in contrast to existing wavelength-modulated sensors that rely on spectral wavelength shifts, the nanocomposite thin-film functionalized fiber sensors used in the disclosed concept are characterized by intensity changes of characteristic localized surface plasmon resonance (LSPR) peaks in the visible spectrum. Targeted applications range from low to high voltage inductors, resistors, and transformers under sinusoidal and square wave excitation, as well as Li-ion batteries from cell to module level under normal and heavy duty charge / discharge conditions. Although temperature sensing signals are shown for illustrative purposes, other parameters can also be monitored, including gas phase species (e.g., H2, CO, CO2, C2H2, C2H4, O2, etc.), magnetic fields, electric fields, etc., with appropriate selection of functional sensing layers.

[0026] 1 is a schematic diagram of a fiber optic sensing system 5 according to an exemplary embodiment of the disclosed concepts. As described in detail herein, in a non-limiting exemplary embodiment, the sensing system 5 is configured to be deployed in a residential or commercial / industrial system and, when so deployed, measures several parameters of interest (such as temperature, gas concentration, and / or magnetic field strength) and wirelessly transmits the parameter measurements to a monitoring computer system that forms part of the fiber optic sensing system 5. In the non-limiting exemplary embodiment shown in FIG. 1, the fiber optic sensing system 5 is configured in a reflectance sensing geometry. However, it will be understood that this is merely exemplary and that other sensing geometries (e.g., transmission geometries) are also contemplated within the scope of the disclosed concepts.

[0027] As shown in FIG. 1, the optical fiber sensing system 5 includes a functionalized optical fiber sensor 10. The functionalized optical fiber sensor 10 includes an optical fiber member 15, such as a multimode silica fiber having a core, and a broadband MM circulator 12 to enable a reflection geometry. An engineered sensing layer 20 is provided (e.g., by a suitable coating method) on at least a portion of the outer surface of the optical fiber member 15. In an exemplary embodiment, the engineered sensing layer 20 includes a nanocomposite material. In one particular embodiment, the engineered sensing layer 20 includes a plasmonic nanocomposite material including a bulk matrix having a plurality of nanoparticles dispersed throughout. In the illustrated embodiment, the bulk material is an oxide material and the nanoparticles are Au nanoparticles, although other types of bulk and / or nanocomposite materials, such as other plasmon-active particles (e.g., Ag, Pd, Pt, alloys, core-shell, non-spherical, etc.), are contemplated within the scope of the disclosed concepts. As described elsewhere herein, the functionalized optical fiber-based sensor 10 exhibits parameter (e.g., temperature, gas concentration, magnetic field level) dependent optical properties and changes the intensity level of the sensor depending on and in response to the level of the parameter of interest.

[0028] The fiber optic sensing system 5 also includes a light source 25 coupled to a first end of the functionalized fiber optic sensor 10. The light source 25 is configured to generate light of a selected specific wavelength and direct the light to the first end of the functionalized fiber optic sensor 10. In a non-limiting exemplary embodiment, the light source 25 includes a light emitting diode (LED) 30, which is coupled to a lens system 35 comprising one or more lenses 40 for collimation. In a specific exemplary embodiment (described and shown elsewhere herein), the one or more lenses 40 are ball lenses, such as fused silica or polymer-based ball lenses. Additionally, in an exemplary embodiment, the LED 30 and lens system 35 are covered with heat shrink tubing for packaging.

[0029] The optical fiber sensing system 5 further includes a wireless interrogator device 45. The wireless interrogator device 45 is configured to measure the intensity of light transmitted through the functionalized optical fiber sensor 10 and wirelessly transmit the intensity information to a remote destination, such as a remotely located computer system 65 (e.g., a PC). This allows the remotely located computer system 65 to monitor any shifts in the intensity of the functionalized optical fiber sensor 10 caused by the measured parameter. As shown in FIG. 1, in an exemplary embodiment, the wireless interrogator device 45 includes a photodiode 50 coupled to the output of the functionalized optical fiber sensor 10, a transimpedance amplifier (TIA) circuit 55 coupled to the output of the photodiode 50, and a controller / wireless transmitter module 60 coupled to the output of the TIA circuit 55. The photodiode 50 is configured to receive light from the output of the functionalized optical fiber sensor 10 and convert the light into a corresponding electrical current. The TIA circuit 55 is a current-to-voltage converter, typically implemented with one or more operational amplifiers, configured to amplify the received current and convert the current into a usable voltage. The usable voltage values / signals are then provided to the wireless controller / transmitter module 60 and transmitted to the computer system 65 using the control logic and one or more transceiver devices of the wireless controller / transmitter module 60 .

[0030] According to one particular exemplary embodiment of the disclosed concept, the wireless interrogator device 45 comprises a photodiode, a TIA circuit, a microcontroller, a transmitter, several indicator LEDs, a battery connection, and a voltage regulator mounted on a single printed circuit board (PCB). This embodiment thus provides a photodiode transimpedance amplifier circuit integrated with a programmed wireless transceiver and microcontroller functionality, and the voltage output from the transimpedance amplifier is connected to an analog input pin of the microcontroller. A minimum threshold voltage is set for the indicator LED on one of the output pins to flash. This is to ensure that the baseline intensity of the LED at the source end is interrogatable, meaning "interrogable with the fiber sensor". In an exemplary embodiment, the sensor interrogator should make a baseline measurement (signal should indicate zero and should be linked to absolute temperature). For example, the temperature change ΔT(x)=T(x)abs-Tbase, where T(x)abs is the absolute temperature along the fiber and Tbase is the baseline temperature. The output pins of the microcontroller send amplified voltage signals to a transmitter which wirelessly communicates them to a computer system 65 where real-time voltage fluctuations can be displayed using appropriate programming commands (e.g., Arduino IDE).

[0031] In one exemplary embodiment, the designed sensing layer 20 is in the form of an Au / TiO2 layer with Au nanoparticles dispersed throughout a TiO2 matrix. The optical temperature response of such an exemplary embodiment is shown in FIG. 2A. In another exemplary embodiment, the designed sensing layer 20 is in the form of an Au / SiO2 layer with Au nanoparticles dispersed throughout a SiO2 matrix. The optical temperature response of such an exemplary embodiment is shown in FIG. 2B. These embodiments mitigate cross-sensitivity and allow for differentiation of multiple parameters with different spectral features when compared to wavelength shift-based sensors. The response of these exemplary embodiments to temperature can be seen in FIG. 2C. Such nanocomposite embodiments include an oxide matrix with Au nanoparticles dispersed throughout and can be fabricated by standard physical vapor deposition techniques followed by heat treatment of the coated fiber at temperatures ranging from 100 to 900°C depending on the matrix selected. The change in optical intensity with increasing temperature is attributed to the increase in the resistivity of gold with increasing temperature. As a result, the reflectance of the sensing film changes due to an increase in the damping frequency associated with the drift velocity of the free electrons and a decrease in the LSPR absorption peak. Theoretically, the position of the LSPR peak can be tuned by the annealing temperature or Au concentration, both of which change the Au grain size. Targeted applications range from low to high voltage inductors, resistors, and transformers under sinusoidal and square wave excitation, as well as Li-ion batteries from cell to module level under normal and heavy duty charge / discharge conditions. In addition to temperature sensing, if appropriate sensing layers are utilized, the same sensing architecture can be applied to monitor other parameters including gases / species (H2, CO2, CH4, other vapors, etc.), humidity, magnetic fields, electric fields, and others. Multi-parameter sensing is also possible by using multiple sensing layers, or even by interrogating a single sensing layer with multiple wavelengths. This can be done with only a moderate increase in sensor complexity, e.g., by increasing the number of photodiodes and applying multiple light sources or filters to enable wavelength discrimination.In some cases, the sensor may be combined with analysis methods or additional self-referencing hardware platforms that allow for multiple wavelength discrimination and correction for source drift or other noise / error sources.

[0032] As mentioned above, in an exemplary embodiment, the wireless interrogator 45 includes a collimated LED (light source 25), a pigtailed photodiode (photodiode 50), a TIA circuit 55, and a transmitter and receiver (with respective microcontrollers) (controller / wireless transmission module 60). As the incident light from the LED 30 propagates through the fiber optic based sensor 10, changes in the reflected light intensity result in changes in the photocurrent generated by the diode 50. That current is then picked up by the TIA circuit 55 and converted and amplified into a voltage output. Operation of the TIA circuit 55 in photovoltaic mode eliminates the need for a reverse bias voltage, thus increasing the signal-to-noise ratio by avoiding dark current. Both resistive and capacitive feedback topologies can be used to control and stabilize the output by adjusting the gain, signal-to-noise ratio (SNR), and bandwidth of an operational amplifier (op-amp).

[0033] FIG. 3A is a schematic diagram of a basic TIA circuit 55 that may be used in system 5 according to an exemplary embodiment, where the TIA gain is defined by the ratio between the maximum difference in output voltage and the maximum difference in input photocurrent. As shown in FIG. 3A, the TIA circuit 55 includes a feedback resistor and a compensation capacitor to control the gain. FIG. 3B is a schematic diagram of an alternative dual-stage TIA circuit 55 that may be employed in system 5 according to another exemplary embodiment. In the design of FIG. 3B, the TIA circuit 55 is provided with a high-gain amplifier and a low-gain amplifier used to control the DC offset, so that the minimum photocurrent can correspond to the minimum input voltage range at the analog-to-digital converter (ADC) of the wireless module. A low-pass filter with a cutoff frequency defined by a resistor is included to capture the low-frequency optical response from the sensor. FIG. 3C is a schematic diagram of another alternative TIA circuit 55 according to yet another exemplary embodiment. The design of FIG. 3C is a multi-amplifier design for higher SNR performance. For each of these exemplary designs, the microcontroller output pin sends an amplified voltage signal to a transmitter that communicates with a receiver in computer system 65 that can display real-time voltage fluctuations using appropriate programming commands (e.g., Arduino IDE). Also, several additional modifications, enhancements, and improvements to the TIA concepts presented herein can be envisioned for adjusting the signal-to-noise ratio, minimizing noise, integrating multiple signals of multi-parameter sensors, and for other methods and techniques.

[0034] Furthermore, in an exemplary embodiment, the disclosed concept provides energy harvesting to power the components of the optical fiber sensing system 5. Two options for the energy harvesting power supply have been investigated to power the light source 25, the TIA circuit 55, and the controller / wireless transmission module 60, among others. FIG. 4A is a schematic diagram of an energy harvesting circuit 70 according to a specific embodiment that harvests energy from sunlight. The energy harvesting circuit 70 may also be operatively coupled to the components of FIG. 1 that require power. As shown in FIG. 4A, the energy harvesting circuit 70 includes two photovoltaic (PV) cells integrated with a Li-ion battery and controlled by a battery protection unit. The PV cells are placed in series to maximize the voltage that can be delivered. The maximum value of the current is 8.8V with direct sunlight incident on both cells. A battery charging IC is included in the circuit design to safely charge and discharge the Li-ion battery. Finally, a Zener diode and a PMOS transistor are used in the switching circuit. The switching circuitry allows the PV cells to power the TIA circuitry 55 when the PV cells reach a certain voltage, and allows the battery to power the circuitry when there is insufficient sunlight incident on the cells. FIG. 4B is a schematic diagram of an energy harvesting circuitry 75 according to another specific embodiment for harvesting energy from the monitored electrical appliance. The energy harvesting circuitry 75 may be operatively coupled to the components of FIG. 1 that require power. The energy harvesting circuitry 75 is a set of current transformers (CTs) designed to obtain redundant power from the energy system monitored by the fiber-optic sensor 10. CTs are typically used to measure the current in the line by generating a current proportional to the transformer windings. The induced current is then analyzed to determine current disturbances. However, in this case, the current may be harvested and conditioned using the proposed CT circuitry to power the system 5.While the energy harvesting method is preferred, an alternative power supply technique could instead utilize a standard battery-based power supply circuit operably coupled to the components of FIG. 1 that require power.

[0035] Additionally, the disclosed concepts provide two alternative exemplary approaches for self-collimation of the LED 30 and coupling to the fiber optic member 15. The first approach is shown in FIG. 5A and uses a threaded mount, a plano-convex lens, a slotted lens tube, and an SMA fiber adapter plate as part of the light source 25 as shown. This first approach also uses an SMA fiber adapter plate, a lens tube, and a threaded mount for coupling to the photodiode 50. The second approach is shown in FIG. 5B and uses heat shrink tubing, a ball lens, and a fiber patch cable as shown.

[0036] Thus, the concepts described and disclosed herein provide several novel features and advantages. For example, in the case of LSPR-based sensing layers, the wavelength tunability of the characteristic LSPR peak in the transmission spectrum of the proposed fiber sensor is unique and thus potentially exploitable for simultaneous multi-parameter sensing. One possible method is by cascading different sensing materials with customized wavelength locations of the individual LSPR peaks, and multiple parameters can be resolved by monitoring the real-time intensity changes of the different peaks. As an example, in the case of gas and temperature sensing, one segment of the sensor may be coated with a temperature-sensitive material that is non-absorbing to the gas molecules of interest, and the other segment may be coated with a gas-sensitive porous nanocomposite material. The light intensity responses induced by temperature and gas concentration can be distinguished in this way. Data-driven approaches such as Principal Component Analysis (PCA) or Support Vector Machine (SVM) may also be implemented to distinguish the convolved multiple parameters. In addition to LSPR-based sensing layers, other types of sensing layers with sufficiently large optical responses, especially when they are wavelength-selective, may also be considered.

[0037] Furthermore, the wireless interrogation-to-monitoring feature makes it ideal for practical implementation of optical fiber sensors in residential and utility-scale field trials. The resulting remote monitoring capability allows for distant signal communication over hundreds of meters to kilometers. The additional feature of integration with cloud services such as LoRaWAN allows sensing data from multiplexed optical fiber point sensors to be stored in the cloud and analyzed in real time. Alternative communication methods are considered possible, including wired communication and even standard wired or optical fiber-based communication methods.

[0038] In addition, energy harvesting using current transformers, photovoltaic, thermoelectric, vibration energy harvesting circuits, or other suitable techniques that minimize the need for local battery energy storage may provide a particularly attractive embodiment of the solution. The low power requirements and simplicity of the circuit interrogation hardware required make such low-cost energy harvesting methods practical.

[0039] Finally, the total cost of a fiber sensing system of the disclosed concepts can be less than $500-600, or even as low as $100 or less. Exemplary system components include multimode silica fiber, material costs associated with thin film fabrication, TIA and power circuit components (capacitors, resistors, op amps, voltage regulators), diodes and LEDs, wireless communication setup, etc. Current estimated costs are at least 10-50 times lower than the cost of existing fiber optic sensor interrogator systems used in laboratory environments. The total cost can be further reduced to less than about $100 with careful design and selection.

[0040] In the claims, signs placed between parentheses shall not be interpreted as limiting the scope of the claim. The word "comprises" or "includes" does not exclude the presence of elements or steps other than those listed in the claim. In a device claim enumerating several means, several of these means may be embodied by one and the same hardware. The word "a" preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination.

[0041] While the present invention has been described in detail for the purpose of illustrating the embodiments presently considered to be the most practical and preferred embodiments, it is to be understood that such detail is for the purposes of illustration only, and that the present invention is not limited to the disclosed embodiments, but on the contrary, is intended to include modifications and equivalent arrangements within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that one or more features of any embodiment can be combined with one or more features of any other embodiment, to the extent possible.

Claims

1. In the sensing system, a functionalized optical fiber sensor including the designed sensing layer; a light source configured to generate light and couple the light to an input of a sensor using the functionalized optical fiber; an interrogator including a photodetector coupled to the functionalized optical fiber sensor to receive transmitted or reflected light, a transimpedance amplifier (TIA) circuit coupled to an output of the photodetector, a controller coupled to an output of the TIA circuit, and a transmitter coupled to the controller for sending a parameter signal indicative of a parameter being monitored by the functionalized optical fiber sensor based on and in response to an output of the TIA circuit; A system comprising:

2. The system of claim 1 , wherein the light detector is a photodiode.

3. The system of claim 1 , wherein the light source comprises an LED coupled to a lens system.

4. The system of claim 3 , wherein the lens system comprises a ball lens.

5. The system of claim 1 , wherein the engineered sensing layer is comprised of a nanocomposite material.

6. The system of claim 5 , wherein the nanocomposite material comprises a matrix having nanoparticles dispersed throughout.

7. The system of claim 6 , wherein the matrix is ​​an oxide matrix.

8. The system of claim 7 , wherein the nanoparticles are plasmonically active nanoparticles.

9. The system of claim 7 , wherein the nanoparticles are Au nanoparticles.

10. The system of claim 1 , wherein the photodetector, the TIA circuit, the controller, and the wireless transmitter are provided on a single printed circuit board.

11. 2. The system of claim 1, wherein a voltage output from the TIA circuit is connected to an analog input pin of the controller, an output pin of the controller is configured to provide a digitally amplified voltage signal based on the voltage output to the wireless transmitter, and the wireless transmitter is configured to wirelessly transmit the digitally amplified voltage signal.

12. The system of claim 1 , wherein the transmitter is a wireless transmitter.

13. The system of claim 12 , wherein the wireless transmitter is an nRF24L01+ RF transmitter or a LoRa RF transmitter.

14. The system of claim 1 , wherein the system is configured in a reflectance sensing geometry and the functionalized optical fiber based sensor includes a circulator.

15. 2. The system of claim 1, wherein in the TIA circuit, a TIA gain is defined by a ratio between a maximum difference in output voltages and a maximum difference in input photocurrents, and the TIA circuit includes a feedback resistor and a compensation capacitor for controlling the TIA gain.

16. 2. The system of claim 1, wherein the TIA circuit includes a high gain amplifier and a low gain amplifier for controlling a DC offset of the TIA circuit, and a low pass filter having a cutoff frequency defined by a resistor for capturing a low frequency optical response from a sensor using the functionalized optical fiber.

17. The system of claim 1 , wherein the TIA circuitry includes multiple operational amplifiers for providing improved signal-to-noise ratio (SNR) performance.

18. 10. The system of claim 1, further comprising an energy harvesting circuit for powering the light source and the interrogator.

19. 20. The system of claim 18, wherein the energy harvesting circuit is integrated with several batteries and battery charging integrated circuits and includes a plurality of photovoltaic (PV) cells connected in series and a switching circuit configured to enable the plurality of PV cells to power the TIA circuit when the plurality of PV cells reach a certain voltage, the switching circuit including a Zener diode and a PMOS transistor.

20. 20. The system of claim 18, wherein the energy harvesting circuitry comprises a set of current transformers (CTs) configured to obtain redundant power from an energy system being monitored by the functionalized optical fiber-based sensor.

21. 2. The system of claim 1, wherein the functionalized optical fiber based sensor includes a second designed sensing layer, the designed sensing layer and the second designed sensing layer having different wavelength positions of their respective LSPR peaks.

22. 10. The system of claim 1, wherein the designed sensing layer is configured to have a plurality of different LSPR peaks corresponding to different wavelength positions.

23. In a sensing method using an optical fiber, generating incident light and coupling the incident light to an input of a functionalized optical fiber based sensor, the functionalized optical fiber based sensor including an engineered sensing layer; receiving the transmitted or reflected light at a photodetector coupled to the functionalized optical fiber sensor; inputting the output of the photodetector into a TIA circuit; generating and transmitting a parameter signal based on and in response to an output of the TIA circuit, the parameter signal being indicative of a parameter being monitored by the functionalized optical fiber sensor; A method comprising:

24. 24. The method of claim 23, wherein the step of generating and sending the parameter signal comprises wirelessly transmitting the parameter signal.

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