Optical sensor and optical sensing system

Abstract

An optical sensor includes a probe fiber Bragg grating (FBG) coupleable to a light source, the probe fiber Bragg grating defining a probe spectrum and arranged to provide a probe light signal corresponding to the probe spectrum. A sensing fiber Bragg grating (FBG) defines a sensing spectrum. A spectral shift in the sensing spectrum is responsive to a change in at least one external parameter acting on the sensing fiber Bragg grating. The optical coupler couples the probe optical signal with the sensing fiber Bragg grating to output a spectrally overlapped optical signal. An intensity level of the spectrally overlapping light signal corresponds to an overlap between the detection spectrum and the sensing spectrum. And an optical power regulator coupled to the optical coupler, the optical power regulator arranged to adjust a baseline of the intensity level to change a sensitivity of the optical sensor.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Singapore application No. 10202301073R, filed on April 18, 2023, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0003] This application relates to optical sensing, and more specifically, to optical sensors and optical sensing systems. Background Technology

[0004] Fiber optic sensors have gained attention across various industries due to their unique advantages, such as light weight, small size, immunity to electromagnetic interference, high sensitivity, rapid detection, real-time monitoring, flexibility, robustness, and the ability to perform multiplexing or distributed sensing. Fiber optics generally refer to waveguides in which optical signals can propagate through total internal reflection within their core. In some implementations, grating structures can be formed or "written" within the core of the fiber to create fiber bragg grating (FBG) sensors.

[0005] However, practical implementations of fiber Bragg grating (FBG) sensors are often limited by the size and cost of commercial detectors. Since FBG sensors are wavelength-based, the optical spectrum analyzer (OSA), which forms part of the demodulation subsystem of the detector or sensing system, is typically bulky and expensive. This limits the potential applications of FBG sensors and FBG sensing systems, as the integrated demodulation system involving multiple components introduces additional complexity. Furthermore, the large size of the demodulator also restricts the practical application of optical sensing systems for remote monitoring or implementation in complex terrain. Summary of the Invention

[0006] According to one aspect, this document discloses an optical sensor according to several embodiments. The optical sensor includes: a probe fiber Bragg grating coupled to a light source, the probe fiber Bragg grating defining a probe spectrum and configured to provide a probe optical signal corresponding to the probe spectrum; a sensing fiber Bragg grating defining a sensing spectrum, wherein a spectral shift in the sensing spectrum responds to a change in at least one external parameter acting on the sensing fiber Bragg grating; an optical coupler coupling the probe optical signal to the sensing fiber Bragg grating to output a spectrally overlapping optical signal, wherein the intensity level of the spectrally overlapping optical signal corresponds to the overlap between the probe spectrum and the sensing spectrum; and an optical power modulator coupled to the optical coupler, the optical power modulator configured to adjust a baseline of the intensity level to change the sensitivity of the optical sensor.

[0007] According to another aspect, an optical sensing system is disclosed herein. This optical sensing system includes the aforementioned optical sensor and a light receiver, the light receiver being configured to receive the intensity level of a spectrally overlapping light signal from the optical sensor. Attached Figure Description

[0008] Several embodiments of this disclosure are described with reference to the following figures:

[0009] Figure 1 This is a schematic diagram of an optical sensing system according to an embodiment of the present disclosure;

[0010] Figure 2 A schematic diagram of an optical sensor according to several embodiments;

[0011] Figure 3A for Figure 2 The example optical sensor shown illustrates the spectral overlap between the probe spectrum (including spectral valleys) and the sense spectrum (including spectral peaks) in the initial state.

[0012] Figure 3B for Figure 2 Another example of the spectrum of the optical sensor shown has unequal measurement ranges;

[0013] Figure 3C for Figure 2 This is yet another example of the spectrum of the optical sensor shown, with unequal measurement ranges;

[0014] Figure 4A As another example of the spectrum of an optical sensor according to several embodiments, the spectral overlap between the probe spectrum and the sense spectrum in the initial state is shown;

[0015] Figure 4B for Figure 4AAnother example of the spectrum of the optical sensor shown has unequal measurement ranges;

[0016] Figure 4C for Figure 4A This is yet another example of the spectrum of the optical sensor shown, with unequal measurement ranges;

[0017] Figure 5 The measurement range in the first direction only is shown for the spectrum of an optical sensor according to several embodiments;

[0018] Figure 6 For another spectrum of an optical sensor according to several embodiments, the measurement range is shown only in the second direction;

[0019] Figure 7 An example of the spectrum of the light source is shown;

[0020] Figure 8 This is a schematic diagram illustrating an implementation of an optical sensing system according to several embodiments;

[0021] Figure 9 This is a schematic diagram of another implementation of an optical sensing system according to several embodiments;

[0022] Figure 10 This is a schematic diagram of yet another implementation of an optical sensing system according to several embodiments;

[0023] Figure 11 This is a schematic diagram of an optical sensor comprising multiple sensing nodes (sensing fiber Bragg gratings) according to various embodiments;

[0024] Figure 12 This is a schematic diagram of an optical sensor according to several embodiments, including a pair of sensing nodes (sensing fiber Bragg gratings) and using a circulator;

[0025] Figure 13A Show Figure 11 The intensity of the light signal of the optical sensor shown during operation;

[0026] Figure 13B Show Figure 12 The intensity of the light signal of the optical sensor shown during operation;

[0027] Figure 14 A schematic diagram of an optical sensor according to several embodiments;

[0028] Figure 15A for Figure 14 The example optical sensor shown illustrates the spectral overlap between the probe spectrum (including spectral peaks) and the sense spectrum (including spectral peaks) in the initial state.

[0029] Figure 15B for Figure 14 Another example of the spectrum of the optical sensor shown has unequal measurement ranges;

[0030] Figure 15C for Figure 14 This is yet another example of the spectrum of the optical sensor shown, with unequal measurement ranges;

[0031] Figure 16 For a plurality of embodiments, including a plurality of sensing nodes (sensing fiber Bragg gratings), Figure 14 A schematic diagram of the optical sensor shown;

[0032] Figure 17 A schematic diagram of an optical sensor according to several embodiments;

[0033] Figure 18 This is a schematic diagram of another optical sensor according to several embodiments;

[0034] Figure 19A for Figure 18 The example optical sensor shown illustrates the spectral overlap between the probe spectrum (including spectral peaks) and the sense spectrum (including spectral valleys) in the initial state.

[0035] Figure 19B for Figure 18 Another example of the spectrum of the optical sensor shown has unequal measurement ranges;

[0036] Figure 19C for Figure 18 This is yet another example of the spectrum of the optical sensor shown, with unequal measurement ranges;

[0037] Figure 20 For a plurality of embodiments, including a plurality of sensing nodes (sensing fiber Bragg gratings), Figure 18 A schematic diagram of the optical sensor shown;

[0038] Figure 21 This is a schematic diagram illustrating an implementation of an optical sensing system according to several embodiments;

[0039] Figure 22 This is a schematic diagram of another implementation of an optical sensing system according to several embodiments;

[0040] Figure 23 This is a schematic diagram of yet another implementation of an optical sensing system according to several embodiments;

[0041] Figure 24This is a schematic diagram of an optical sensor and optical sensing system with multiple measurement ranges for multiplex sensing, according to several embodiments.

[0042] Figure 25 for Figure 24 The example optical sensor shown illustrates the spectral overlap between the probe spectrum (including multiple spectral valleys) and the sensing spectrum (including multiple spectral peaks) in the initial state.

[0043] Figure 26 For those with multiple measurement ranges Figure 24 Another example of the spectrum of the optical sensor shown.

[0044] Figure 27 for Figure 24 A schematic diagram of an implementation of the optical sensing system shown;

[0045] Figure 28 for Figure 24 A schematic diagram of another implementation of the optical sensing system shown;

[0046] Figure 29 for Figure 24 A schematic diagram of another embodiment of the optical sensing system shown;

[0047] Figure 30 An example spectrum of a light source with varying drive current is shown;

[0048] Figure 31 Examples of probing and sensing the spectrum of a chirped fiber bragg grating (CFBG) are shown.

[0049] Figure 32 The spectral response under the applied strain is shown;

[0050] Figure 33 The strain response of the first group is shown, illustrating strain sensing behavior at baseline optical powers of 2.4 nanowatts, 5.9 nanowatts, 8.5 nanowatts, 15.1 nanowatts, and 22.5 nanowatts;

[0051] Figure 34 The strain response of the second group is shown, illustrating strain sensing behavior at relatively high baseline optical powers (i.e., 31.3 nanowatts, 55.6 nanowatts, and 101.7 nanowatts).

[0052] Figure 35 This illustrates the relationship between strain sensitivity and baseline optical power;

[0053] Figures 36 to 38The response of the optical sensing system to applied strain is shown for three different data sets (represented as the first segment 2301, the second segment 2302, and the third segment 2303, respectively).

[0054] Figure 39 This demonstrates the effect on strains up to approximately 3000 microstrains ( The response of the optical sensing system in the first segment 2401 was measured by the tensile strain of the sensor.

[0055] Figure 40 This shows the effect on approximately 2300 microstrains ( The optical sensing system response of the second segment 2402 measured below;

[0056] Figure 41 and Figure 42 An example dataset of strain sensitivity recorded for a given voltage baseline range is shown;

[0057] Figure 43 The image shows vibration data captured in the time domain, where the Y-axis represents the amplitude of the applied vibration.

[0058] Figure 44 This demonstrates the analysis of time-domain data through Fourier transformation in the frequency domain. Figure 43 Vibration data;

[0059] Figure 45 The optical sensor's response to temperature variations ranging from room temperature to approximately 75 degrees Celsius is shown. Detailed Implementation

[0060] The following detailed description, with reference to the accompanying drawings, illustrates the details and embodiments of this disclosure for illustrative purposes. Features described in the context of one embodiment may be adapted accordingly to the same or similar features in other embodiments, even if not explicitly described in those other embodiments. Additional and / or combinations and / or substitutions described for features in the context of one embodiment may be adapted accordingly to the same or similar features in other embodiments.

[0061] In the context of various embodiments of this disclosure, the articles “a,” “an,” and “the” used with respect to features or elements include references to one or more features or elements.

[0062] In the context of various embodiments of this disclosure, the terms “about” or “approximately” applied to numerical values ​​cover the exact value and reasonable difference as commonly understood in the relevant art, such as within 10% of a specified value.

[0063] The term “and / or” as used herein includes any and all combinations of one or more of the relevant listed items.

[0064] For the sake of brevity, the term “spectrum” may be used to refer to any one or more of the following: “wavelength spectrum,” “wavelength band,” “frequency spectrum,” “frequency band,” “wavelength spectrum,” “frequency spectrum,” “optical wavelength spectrum,” “optical frequency spectrum,” “optical spectrum,” “optical signal spectrum,” “power spectrum,” etc., as understood from the context.

[0065] For the sake of brevity, the term "overlap" may include partial overlap between a first wavelength spectrum and a second wavelength spectrum, wherein a portion of the first wavelength spectrum lies within the second wavelength spectrum, or vice versa. Furthermore, the term "overlap" may also include complete overlap between a first wavelength spectrum and a second wavelength spectrum, wherein the entire spectrum of the first wavelength spectrum lies within the second wavelength spectrum, or vice versa.

[0066] As used in this document, the term "optical sensor" can refer to any of the following: fiber bragg grating (FBG) sensor, integrated sensor, interrogator, integrated sensing device, photonic sensor, etc. Similarly, the term "optical sensing system" can refer to any of the following: fiber bragg grating sensing system, integrated sensing system, detection system, integrated sensing system, data acquisition system, detector, optical sensing module, etc. Fiber bragg grating sensors can include, but are not limited to, uniform fiber bragg gratings (uFBG), chirped fiber bragg gratings (CFBG), and apodised fiber bragg gratings.

[0067] In fiber Bragg gratings (FBGs), the term "external parameter" typically refers to one or more external influences / effects / perturbations / changes acting on the FBG, causing a change in the FBG's spectrum or a portion of its spectrum. Spectral changes can include, but are not limited to: shifts in the center wavelength of the spectrum, changes in the spectral band / bandwidth, changes in the shape / curvature / fit of the spectrum, spectral attenuation or enhancement, or any combination of one or more of the above. Spectral changes can be determined by evaluation, measurement, calculation, estimation, or otherwise, and can correspond to one or a combination of multiple external parameters acting on the FBG. External parameters can also refer to any measurable quantity that can cause a shift in the FBG's spectrum, such as strain, temperature, humidity, refractive index, etc.

[0068] This disclosure includes intensity-based optical sensors and intensity-based optical sensing systems according to various embodiments. The optical sensors / optical sensing systems can be used to measure a variety of parameters, including but not limited to strain, temperature, vibration, refractive index, etc. The sensing signals generated by the optical sensors and optical sensing systems are clean, stable, repeatable, and reliable. In several embodiments, the optical sensor may include a probe fiber bragg grating (FBG), a sensing fiber bragg grating (FBG), and an optical coupling stage that optically communicates with the probe and sensing FBGs. The optical coupling stage may be configured to couple a probe light signal from the probe FBG to the sensing FBG to output a spectrally overlapping light signal or a sensing signal corresponding to the measured quantity. For example, the reflection spectrum from the sensing FBG may interfere with the input probe light signal at the optical coupling stage, thereby outputting a spectrally overlapping light signal. Reflection-based sensors or sensing systems are typically robust and less sensitive to external interference due to the reduction in leading cables and wiring.

[0069] The spectrally overlapped optical signal corresponds to the overlap between the individual spectra of the probe fiber Bragg grating and the sensing fiber Bragg grating. In response to an external parameter (e.g., strain) acting on the sensing fiber Bragg grating, the sensing fiber Bragg grating undergoes a spectral shift or change, resulting in a change in the intensity of the spectrally overlapped optical signal. This intensity change corresponds to a change in the bandwidth of the spectrally overlapped optical signal. A larger overlap width corresponds to a larger overlap area and higher power or intensity. The arrangement between the probe and sensing fiber Bragg gratings allows for the detection of the spectrally overlapped optical signal corresponding to the measured quantity through the overlap of their respective spectra. Furthermore, an optical power regulator coupled to the optical coupling stage can be provided to adjust the baseline of the spectrally overlapped optical signal intensity. This enables dynamically adjustable sensitivity and dynamically adjustable measurement or sensing range of the optical sensor for a given set of electronic components.

[0070] The proposed setup "transforms" spectral-based sensor / sensing systems into intensity-based systems, thereby reducing the need for spectral analyzers and associated complex demodulation systems. This enables reliable, compact, and scalable sensing solutions for continuous and real-time monitoring. The proposed sensors and sensing systems can be used in a wide range of industries, such as energy, transportation, aerospace and marine, civil engineering, oil and gas, defense, and scientific research, targeting structural health monitoring applications and sensing static and dynamic strain, temperature, vibration, and refractive index.

[0071] For ease of understanding and not for limitation, several embodiments of the optical sensing system 50 and the optical sensor 100 will be described below with reference to the accompanying drawings. Figure 1This is a schematic diagram of an optical sensing system 50. The optical sensing system 50 may include an optical sensor 100 optically coupled to a light source 80 and a light receiver 90. The light receiver 90 may output a sensing signal, which may be acquired by or combined with a data acquisition (DAQ) device or system. The optical sensor 100 may include a probe segment 101 optically communicating with one or more sensing nodes 120 / 220 / 320. The sensing nodes 120 / 220 / 320 may be sensing fiber Bragg gratings coupled to the probe segment 101 in a parallel arrangement. In some embodiments, the probe segment 101 may be located at a probe end 51, away from the sensing nodes 120 / 220 / 320 located at a sensing end 53. Because the sensing fiber Bragg grating at the sensing end 53 is typically small and compact, the optical sensing system 50 can be used for remote monitoring and challenging terrain, such as leak detection, railway, bridge, tunnel or track monitoring, in-vivo oximetry, scintillation counting, intravascular pressure sensing, etc.

[0072] Fiber Bragg gratings can take many forms, including but not limited to uniform fiber Bragg gratings, chirped fiber Bragg gratings, windowed fiber Bragg gratings, or combinations thereof. Fiber Bragg gratings can be sensitive to external parameters or their effects, such as temperature, strain, vibration, and refractive index. The sensing response caused by physical or external parameters is detected in the form of changes in the spectral overlap of the optical sensor 100 (e.g., wavelength, intensity, or spectral shift). Optical sensors can be used in a variety of applications, such as temperature sensing, strain sensing, vibration monitoring, refractive index monitoring, chemical sensing, and pressure monitoring, and exist in various structures with different sizes and shapes across multiple industries.

[0073] Figures 2 to 3CAn optical sensing system 50 and an optical sensor 100 according to several embodiments are illustrated. The optical sensing system 50 may include a light source 80 optically coupled to the optical sensor 100. In some embodiments, the light source 80 may provide a source optical signal 81 that defines a reference spectrum. In some examples, the reference spectrum may be a Gaussian spectrum or a broadband spectrum of the source optical signal 81. In other examples, the reference spectrum may be a predetermined or selected spectrum. In some embodiments, the light source 80 may be a broadband light source, a tunable light source, a light-emitting diode (LED), a super luminescent diode (SLED), or a combination thereof.

[0074] Optical sensor 100 may include a probe segment 101 coupled to or in optical communication with a sensing fiber Bragg grating (FBG) 120. The probe segment 101 may be located at a different position from the sensing FBG 120. The probe segment 101 may include a probe FBG 110 in optical communication with an optical coupling stage (e.g., optical coupler 130). In some examples, the optical coupler 130 may be a 2×2 3dB optical coupler. In some embodiments, the probe FBG 110 and the sensing FBG 120 may be spectrally correlated with each other, for example, with aspects related to their respective center wavelengths, bandwidths, etc. In several examples, the probe FBG 110 may be coupled to a first arm of the optical coupler 130, the sensing FBG 120 may be coupled to a second arm of the optical coupler 130, the optical power modulator 140 may be coupled to a third arm of the optical coupler 130, and the reference monitor (R') may be coupled to a fourth arm of the optical coupler 130. In some embodiments, the fourth arm of the optical coupler 130 may remain unconnected. In several other embodiments, the optical coupling stage may be replaced by an optical circulator.

[0075] refer to Figure 3AThe probe fiber Bragg grating 110 can define a probe spectrum (S1), which includes a first spectral band (B1). The first spectral band (B1) can serve as a characteristic of the probe spectrum (S1). The first spectral band (B1) can be symmetrical about a first center wavelength (F1). The incident light signal in the first spectral band (B1) can be reflected or attenuated by the probe fiber Bragg grating 110. In some embodiments, the probe fiber Bragg grating can be a chirped fiber Bragg grating (CFBG). In some embodiments, in response to receiving a source light signal 81 from the light source 80, the probe fiber Bragg grating 110 can provide a probe light signal 111 corresponding to the probe spectrum (S1). It is understood that the probe fiber Bragg grating 110 can be used as a filter for the input source light signal 81 from the light source 80, while the sensing fiber Bragg grating 120 is installed in the field as a sensing node or sensitive element for monitoring or measurement purposes.

[0076] like Figure 2 and Figure 3A As shown, the probe fiber Bragg grating 110 can be configured for transmission, such that the probe spectrum (S1) includes a spectral valley (S1a) corresponding to the first spectral band (B1). Therefore, the probe spectrum (S1) is a transmission spectrum. The probe spectrum (S1) allows transmission of sub-spectrums outside the first spectral band (B1) and reflection / attenuation of sub-spectrums within the first spectral band (B1). Therefore, a portion of the source optical signal 81 corresponding to the first spectral band (B1) is reflected by the probe fiber Bragg grating 110, while allowing transmission of the remaining sub-spectrums. In other words, a portion of the source optical signal 81, as the probe optical signal 111, passes through the probe fiber Bragg grating 110, wherein at least a portion of the first spectral band (B1) is reflected back to the light source 80. Therefore, the probe optical signal 111 provided by the probe fiber Bragg grating 110 can be considered as the source optical signal 81 after optical filtering. In some embodiments, a reference monitor (R') coupled to the optical coupler 130 can be configured to monitor fluctuations in the probe optical signal 111 or the source optical signal 81.

[0077] In some embodiments, an optical isolator 82 may be provided between the light source 80 and the detector section 101 to optically couple the source optical signal 81 to the detector section 101 or the detector fiber Bragg grating 110. In some embodiments, the optical isolator 82 may be optically coupled between the light source 80 and the detector fiber Bragg grating 110 to absorb light reflections or other forms of light reflections from the detector section 101, the detector fiber Bragg grating 110, thereby preventing such reflections from interfering with the light source 80. For strongly chirped fiber Bragg grating (CFBG) structures, the reflection spectrum can be considered to be dominant within the full width at half maximum (FWHM) bandwidth, and the reflection spectrum can be considered as a rectangular distribution for ease of understanding.

[0078] Continue to refer to Figure 3A The sensing fiber Bragg grating 120 can also define a sensing spectrum (S2), which includes a second spectral band (B2). The second spectral band (B2) can be a characteristic of the sensing spectrum (S2). The second spectral band (B2) can be symmetrical about a second center wavelength (F2). Similarly, the incident light signal in the second spectral band (B2) can be reflected or attenuated by the sensing fiber Bragg grating 120. The sensing fiber Bragg grating 120 can also be a chirped fiber Bragg grating (CFBG).

[0079] The sensing fiber Bragg grating 120 can be configured to cause a spectral shift or change in the sensing spectrum (S2) or the second spectral band (B2) in response to a change in at least one external parameter acting on the sensing fiber Bragg grating 120. In some examples, the external parameter may include at least one of strain, temperature, vibration, and refractive index. The aforementioned spectral shift mainly refers to a shift in the sensing spectrum (S2) towards a shorter wavelength direction (along the second direction 74) or towards a longer wavelength direction (along the first direction 72), respectively referred to as a blue shift or a red shift.

[0080] In several embodiments, the sensing fiber Bragg grating 120 can be configured for reflection, such that the sensing spectrum (S2) includes a spectral peak (S2a) corresponding to the second spectral band (B2). Therefore, the sensing spectrum (S2) is a reflection spectrum. The sensing spectrum (S2) allows for reflection of sub-spectrums corresponding to the second spectral band (B2), as well as attenuation of sub-spectrums outside the second spectral band (B2). In other words, the optical signal reflected by the sensing fiber Bragg grating 120 includes at least a portion of the second spectral band (B2).

[0081] Operating the sensing fiber Bragg grating 120 in reflective configuration or reflective mode significantly reduces the amount of lead fiber optic cable required during field deployment. This reduces deployment complexity and operating costs, especially in large-scale installations requiring extensive cabling infrastructure. Compared to operation in transmissive configuration / transmissive mode, this configuration allows the optical sensing system 50 to be integrated with multiple channels within a given (or limited) space or form factor without adversely affecting measurements. This provides scalability and robust measurements. Furthermore, this architecture or arrangement of the sensing fiber Bragg grating 120 advantageously enables relatively simple or less complex optical sensing system structures or infrastructures to acquire data from hard-to-reach locations.

[0082] In several embodiments, the optical coupler 130 can optically couple the probe optical signal 111 from the probe fiber Bragg grating 110 to the sensing fiber Bragg grating 120 to output a spectrally overlapping optical signal 131 with an intensity level (I12). Figure 3A It can be understood that the sub-spectrum of the probe optical signal 111 corresponding to the second spectral band (B2) can be reflected by the sensing fiber Bragg grating 120 and output by the optical coupler 130 as the spectral overlap optical signal 131. The spectral overlap optical signal 131 can correspond to the overlap between the probe spectrum (S1) and the sensing spectrum (S2).

[0083] like Figure 3B In the example shown, when the sensing fiber Bragg grating 120 is subjected to a change in external parameters (e.g., tension or tensile strain), the sensing spectrum (S2) is along the first direction 72 (from... Figures 3A to 3B This results in a shift or redshift. This leads to increased overlap between the probe spectrum (S1) and the sensing spectrum (S2), which in turn increases the intensity (I12a) of the spectral overlap light signal 131a. In cases such as... Figure 3C In another example shown, when the sensing fiber Bragg grating 120 is subjected to a change in another external parameter (e.g., compression or compressive strain), the sensing spectrum (S2) is along the second direction 74 (from... Figures 3A to 3C The optical fiber Bragg grating 120 is subjected to an external disturbance, which may cause a blue shift or a change in the intensity of the optical signal 131b. This results in a reduction in the overlap between the probe spectrum (S1) and the sensing spectrum (S2), and consequently a decrease in the intensity (I12b) of the spectral overlap signal 131b. Therefore, it can be understood that the intensity level (I12b) of the spectral overlap signal 131 corresponds to the degree of overlap between the probe spectrum (S1) and the sensing spectrum (S2). When the sensing fiber Bragg grating 120 is subjected to an external disturbance, the spectral overlap signal 131 can change; therefore, the spectral overlap signal 131 can be used to measure any measurand that can alter the sensing spectrum (S2).

[0084] like Figure 3A As shown, in the initial or neutral state where the sensing fiber Bragg grating 120 is not affected by external factors, the first spectral band (B1) may be spaced apart from or offset relative to the second spectral band (B2). This initial state may correspond to a state where no external parameters act on the sensing fiber Bragg grating 120. Furthermore, in the initial state, the first spectral band (B1) may overlap with the second spectral band (B2), such that the spectrally overlapped optical signal 131 may have an initial intensity level I12. In some embodiments, the second spectral band (B2) may include a longer wavelength range compared to the first spectral band (B1). For example, the first spectral band (B1) may be between the spectral limits of 1544 nanometers (nm) and 1550 nanometers, with its first center wavelength (F1) centered at 1547 nanometers or (λ–BW / 2, where λ is the center wavelength of the second spectral band at 1550 nanometers, and BW corresponds to a bandwidth of 6 nanometers). The second spectral band (B2) can be located between the spectral limits of 1547 nm and 1553 nm, which overlaps with the first spectral band (B1), and its second center wavelength (F2) is at 1550 nm (λ).

[0085] In some embodiments, the first spectral band (B1) and the second spectral band (B2) may have the same bandwidth (BW), for example, 6 nanometers. In several embodiments, in the initial state, the second center wavelength (F2) located at 1550 nanometers may be aligned with the spectral limit (1550 nanometers) of the first spectral band (B1). Similarly, the first center wavelength (F1) located at 1547 nanometers may be aligned with the spectral limit (1547 nanometers) of the second spectral band (B2).

[0086] Refer again Figure 2In several embodiments, the optical coupler 130 can output the spectrally overlapped optical signal 131 to the optical power regulator 140. The optical power regulator 140 can be configured to adjust the baseline of the intensity level (I12) of the spectrally overlapped optical signal 131 to change the sensitivity of the optical sensor 100. The optical power regulator 140 can be a variable optical attenuator (VOA) 140, which is configured to adjust the initial optical power baseline (defined intensity level) of the spectrally overlapped optical signal 131. The output of the variable optical attenuator 140 can be an optical output signal 141, wherein any change in any external parameter applied to the sensing fiber Bragg grating 120 is encoded as a change in the intensity level or light intensity of the optical output signal 141. The optical output signal 141 can be output to or received by the optical signal channel (CH1) of the optical receiver 90. In other examples, the light output signal 141 can be regarded as the first channel output (CH 1) of the optical sensor 100 or the optical sensing system 50.

[0087] In several embodiments, reference is made to Figure 3A The overlap range (B121 and B122) or overlap wavelength range between the first spectral band (B1) of the detection spectrum (S1) and the second spectral band (B2) of the sensing spectrum (S2) can correspond to the measurement range of the optical sensor 100. For example, when the optical sensor 100 is in a position such as Figure 3A In the initial state shown, the optical sensor 100 may have a first measurement range (B121) in a first direction 72 and a second measurement range (B122) in a second direction 74. The first measurement range (B121) and the second measurement range (B122) may be equal, therefore, the optical sensor 100 may have equal measurement ranges (B121 and B122) along the first and second directions 72 / 74. In other examples, the first measurement range (B121) and the second measurement range (B122) may not be equal, but may depend on the spectral characteristics of the probe fiber Bragg grating 110 and the sense fiber Bragg grating 120 selected during the implementation of the optical sensor or system.

[0088] In some examples, the first measurement range (B121) and the second measurement range (B122) may correspond to the respective limits of stretching and compression that the optical sensor 100 can measure. For example, a further shift (or further stretching) of the sensed spectrum (S2) beyond the first measurement range (B121) in the first direction 72 causes the intensity (I12) of the spectral overlap light signal 131 and the light output signal 141 to no longer change or to reach saturation. Alternatively, a further shift (or further compression) of the sensed spectrum (S2) beyond the second measurement range (B122) in the second direction 74 causes the intensity (I12) of the spectral overlap light signal 131 and the light output signal 141 to be non-unique.

[0089] In some embodiments, the measurement range (B121 / B122) may be predetermined or set based on the optical sensor application. In such cases... Figure 3B and Figure 3C In other examples shown, the first measurement range (B121) and the second measurement range (B122) may not be equal in the initial state, and therefore the respective limits of their measurement ranges along directions 72 / 74 may also be unequal. This can be applicable to applications where changes in external parameters are biased in a certain direction. For example, when the optical sensor 100 is configured to measure unidirectional compression strain in a compression-dominant structure. In yet another example, when the optical sensor 100 is configured to measure the temperature of a processor to monitor overheating, a larger measurement range is required in the high-temperature region.

[0090] In several embodiments, the sensitivity of the optical sensor 100 (e.g., its response to applied strain) may depend on the baseline or initial baseline (defined intensity level) of the optical output signal 141. The sensitivity of the optical sensor 100 may be adjusted by a variable optical attenuator 140. For a higher baseline, a small change (or a small strain) in the external parameters acting on the sensing fiber Bragg grating 120 will result in a relatively large change in the intensity of the spectrally overlapping optical signal 131.

[0091] In other embodiments, reference is made to Figures 4A to 4C In the initial state of sensing the fiber Bragg grating 120, the second spectral band (B2) can include a shorter wavelength range compared to the first spectral band (B1). For example, as Figure 4AAs shown, the first spectral band (B1) can be located between the spectral limits of 1547 nm and 1553 nm, with its first center wavelength (F1) centered at 1550 nm or (λ + BW / 2). The second spectral band (B2) can be located between the spectral limits of 1544 nm and 1550 nm, overlapping with the first spectral band (B1), with its second center wavelength (F2) at 1547 nm (λ). Similarly, the overlap range (B121 and B122) between the detection spectrum (S1) and the sensing spectrum (S2) can correspond to the measurement range of the optical sensor 100. In some examples, the first measurement range (B121) and the second measurement range (B122) can correspond to the respective limits of stretching and compression that the optical sensor 100 can measure. Figure 4B and Figure 4C In other examples shown, the first measurement range (B121) and the second measurement range (B122) may not be equal in the initial state, and therefore the respective limits of their measurement ranges along directions 72 / 74 are also not equal.

[0092] In such Figure 5 In other embodiments shown, in the initial state of sensing the fiber Bragg grating 120, the second spectral band (B2) may not overlap with the first spectral band (B1). This arrangement allows the optical sensor 100 to perform unidirectional measurements, in other words, measurements with a single measurement range (B121) along a single direction 72. This arrangement is suitable for use cases where changes in external parameters are dominant in a single direction. For example, when the optical sensor 100 is used to measure unidirectional tensile strain in a building structure where the load is predominantly tensile. Figure 6 In yet another embodiment shown, in the initial state of sensing the fiber Bragg grating 120, the second spectral band (B2) can completely overlap with the first spectral band (B1). A further addition to this configuration is that the first spectral band (B1) and the second spectral band (B2) do not share a common overlap bandwidth. This type of configuration can be applied to applications where changes in external parameters are not directional, such as when monitoring or measuring vibrations.

[0093] Figure 7An example reference spectrum 810 of the source light signal 81 of a light source 80 driven at an input current of 100 mA is shown, and another example reference spectrum of the light source 80 at an input current of 50 mA is also shown. The reference spectrum 810 may include a rising side 811, a falling side 813, and an inflection wavelength 815 or inflection point. The rising side 811 may correspond to a low-to-high transition in the spectrum. The falling side 813 may correspond to a high-to-low transition in the spectrum. In several embodiments, a first spectral band (B1) of the probe fiber Bragg grating 110 may be located on the rising side 811 of the reference spectrum 810. Similarly, a second spectral band (B2) of the sense fiber Bragg grating 120 may also be located on the rising side 811 of the reference spectrum 810. In some examples, the first spectral band (B1) and the second spectral band (B2) do not overlap. In other embodiments, both the first spectral band (B1') and the second spectral band (B2') may lie on the falling side 813 of the reference spectrum 810 of the light source 80. This ensures that the intensity or power of the probe light signal 111 changes linearly, thus preventing inaccuracies during sensing. In some examples, the first spectral band (B1') may overlap with the second spectral band (B2'). In other examples, the inflection point wavelength 815 or inflection point of the reference spectrum 810 may be located outside the first spectral band (B1) of the probe spectrum (S1). In other words, the first spectral band (B1) does not cross the inflection point wavelength 815. Similarly, the inflection point wavelength 815 may also be located outside the second spectral band (B2) of the sensing spectrum (S2).

[0094] Figure 8An integration of an optical sensing system 50 according to several embodiments is illustrated. A light output signal 141, including sensing data encoded in the form of light intensity modulation, can be received by an optical signal channel (CH1) of a light receiver 90. In some embodiments, the light receiver 90 may include a photodiode 91. The photodiode 91 may convert the light output signal 141, or in some embodiments, the spectral overlap signal 131, into an equivalent current signal. The photodiode 91 may be a light-sensitive semiconductor diode that generates a current after absorbing photons of light received from its respective input channel (e.g., CH1). Typically, the current amplitude generated by the photodiode 91 may be small, making direct and accurate measurement using conventional devices challenging. In various embodiments of the light receiver, a transimpedance amplifier 93 may be coupled to or connected in series with the photodiode 91 to amplify or convert the current signal generated by the photodiode 91 into an equivalent measurable voltage signal or analog voltage signal. In some examples, the transimpedance amplifier 93 may be an operational amplifier or operational amplifier circuit configured to convert an input source current into an equivalent voltage. In some embodiments, the photodiode 91 and the transimpedance amplifier 93 can be integrated into a single electronic circuit, semiconductor chip, or printed circuit board (PCB). In various embodiments, the voltage signal generated by the output stage of the transimpedance amplifier 93 can be analog in nature (continuous waveform), also referred to as an analog voltage signal. The optical receiver 90 may also include an analog-to-digital converter (ADC) 95 for converting the analog voltage signal into an equivalent digital signal. The digital signal output by the ADC 95 can be considered as a digital equivalent sensing signal or digital sensing signal corresponding to the optical output signal 141 or, in some embodiments, the spectral overlap signal 131, in response to external parameters (e.g., strain, temperature, vibration, etc.) acting on the sensing fiber Bragg grating 120. The ADC 95 converts the analog signal with continuous amplitude and continuous time into a digital signal with discrete amplitude and discrete time using key conversion parameters such as sampling rate, bandwidth, and resolution.

[0095] In various implementations, the digital sensing signals or digital sensing data generated by the analog-to-digital converter 95 can be stored in a computer-readable medium, a microcontroller, or a server, such as a Raspberry Pi, a single-board computer on a chip, which has a server application (computer instruction code) pre-installed to store the digital equivalent sensing signals. For example, the server could be a virtual network computing (VNC) server 97. User 60 can communicate remotely with the server using a corresponding client application 99 (e.g., a VNC client) to remotely access the sensing data based on client-server technology. In some examples, data access may include, but is not limited to, viewing, saving, visualizing, downloading, preprocessing, analyzing, or filtering data. Other examples of media that can be used for remote access to sensing data may include, but are not limited to, long-range radio (LoRa) protocols, the Internet (a wireless network protocol based on the IEEE 802.11 standard), Bluetooth, and the ZigBee protocol.

[0096] Figure 9 An integration of an optical sensing system 50 according to several embodiments is illustrated. Digital sensing signals or digital sensing data provided by an analog-to-digital converter (ADC) 95 of the light receiver 90 can be considered as an equivalent representation of an optical output signal 141, or in some embodiments, a spectral overlap signal 131, received by a photodiode 91. This digital sensing signal can be provided as input to a wireless data logger 96 or wireless recorder communicating with the light receiver 90. The wireless data logger 96 can communicate with one or more remote devices. The wireless data logger 96 can be an Internet of Things (IoT) monitoring node, a sensing node, or an edge device configured to transmit, view, or record data in real time. The wireless data logger 96 can also be configured to apply edge processing or related operations to the recorded data or real-time sensing data, such as filtering, cleaning, smoothing, machine learning, dataset training, visualization, etc. The wireless data logger 96 may also include functionality for sending or transmitting data to a remote location via a gateway, TCP / IP protocol, cloud, etc.

[0097] Figure 10Another integration of the optical sensing system 50 according to several embodiments is illustrated. Digital sensing signals or digital sensing data provided by the analog-to-digital converter (ADC) 95 of the optical receiver 90 can be directly transmitted to the cloud platform 98 (telemetrically), for example, via a base station, internet connection, etc. The cloud platform 98 may include cloud servers, such as AWS, Azure, Google, etc., where data is stored or processed. The cloud server 98 may also be configured to communicate with or be accessed through a smartphone 62 or mobile device, a metric application 64, a workstation 66, a mobile application 68, etc. Users can access the sensing data residing in the cloud server 98 via a smartphone, set the sensing data to public or private, use mobile applications (Android, iOS, Windows), visualize sensor performance using metric groups or dashboard applications, or simply take necessary actions or decisions based on the sensing data on a personal computer (workstation) in the office. The cloud infrastructure can also be configured to execute computer instruction sets based on insights from the sensing data. In several embodiments, the base station may also be configured to perform edge processing on the digital signals before sending them to the cloud platform 98.

[0098] The integration of components or modules, such as photodiode 91, transimpedance amplifier 93, analog-to-digital converter 95, wireless data transmission module 96, data acquisition, etc., can be integrated into a single printed circuit board (PCB), which enables on-chip remote optical sensing.

[0099] In various embodiments, the optical sensor 100 and the optical sensing system 50 can be extended or expanded to multiple channels or multiple independent sensing fiber Bragg gratings (FBGs) for multi-channel sensing. The provision of the optical coupler 130 facilitates the scalability of the optical sensor 100. In various embodiments, the optical sensor 100 may include multiple optical couplers 130 / 230 / 330 optically coupled to their respective multiple sensing fiber Bragg gratings 120 / 220 / 320. Each of the multiple optical couplers 130 / 230 / 330 may be coupled in parallel.

[0100] See Figure 11 In various embodiments, based on Figure 2In the illustrated embodiment, the detection segment 101 of the sensor 100 may further include a second optical coupler 230 optically coupled to the first optical coupler 130 to receive a second detection optical signal 211. For example, the first arm of the second optical coupler 230 may be coupled to the fourth arm of the first optical coupler 130. In various embodiments, the second detection optical signal 211 may correspond to the detection optical signal 111. In various embodiments, the second detection optical signal 211 may be a power branch of the detection optical signal 111, but with a lower power intensity relative to the detection optical signal 111. For example, the second detection optical signal 211 may include the same first spectral band (B1) corresponding to the detection spectrum (S1) of the detection optical signal 111, but with lower optical power or intensity.

[0101] Sensor 100 may further include a second sensing fiber Bragg grating (FBG) 220 coupled to a second optical coupler 230 and thus indirectly coupled to a first optical coupler 130. The second sensing FBG 220 may be configured for reflection. Similarly, the second sensing FBG 220 may define a second sensing spectrum, which includes a third spectral band. The third spectral band may be a characteristic of the second sensing spectrum. The second sensing spectrum is a reflection spectrum. The second sensing FBG 220 may also be a chirped fiber Bragg grating (CFBG). The second sensing FBG 220 may be configured to undergo a spectral shift or change in the second sensing spectrum in response to a change in at least one external parameter acting on the second sensing FBG 220.

[0102] In various embodiments, the second optical coupler 230 can optically couple the second probe optical signal 211 from the optical coupler 130 to the second sensing fiber Bragg grating (FBG) 220 to output a second spectral overlap optical signal 231 with an intensity level. Figure 11The sub-spectrum of the second probe optical signal 211 can be reflected by the second sensing fiber Bragg grating 220 and output as a second spectral overlap optical signal 231 by the second optical coupler 230. The second optical coupler 230 can output the second spectral overlap optical signal 231 to the second optical power regulator 240. The second optical power regulator 240 can be set as a baseline to adjust the intensity level of the second spectral overlap optical signal 231 to change the sensitivity of the second sensing fiber Bragg grating 220 (CH 2). The second optical power regulator 240 can be a variable optical attenuator (VOA) 140, which provides the second optical output signal 241 to the second optical signal channel (CH 2). In other examples, the second optical output signal 241 can be regarded as the second channel output (CH2) of the optical sensor 100 or the optical sensing system 50.

[0103] Similarly, a third sensing fiber Bragg grating (FBG) 320 and a third optical coupler 330 may also be provided to the sensor 100. Similarly, the third optical coupler 330 can optically couple the third probe optical signal 311 from the second optical coupler 230 to the third sensing fiber Bragg grating 320 to output a third spectral overlap optical signal 331 with an intensity level. Multiple sensing fiber Bragg gratings and their respective multiple optical couplers may be added to the sensor 100 in a parallel arrangement. In some cases, the first optical power regulator 140 and the second optical power regulator 240 may be implemented using a single optical power regulator with multiple channels. In some embodiments, a reference signal R' from the third optical coupler 330 (or the last coupling stage in some embodiments) may be used to monitor the effects of fluctuations present in the probe optical signal 311 and / or the light source 80.

[0104] In various embodiments, a dual-channel optical sensor 100 (or optical sensing system 50) may be provided, comprising one channel (e.g., channel 1) for strain sensing and another channel (e.g., channel 2) for temperature sensing. This arrangement allows the user to interpret temperature-compensated strain sensing, such as for strain caused by pressure, force, torque, etc., suitable for a variety of applications across industries. Similarly, temperature-compensated vibration monitoring or vibration sensing under conditions free from thermal interference can also be performed. However, it should be understood that with an additional second optical coupler, the power intensity of the respective probe optical signals may be reduced or decreased.

[0105] Figure 12An optical sensor 100 with a dual-channel sensing configuration according to several embodiments is shown. For power budget considerations, the optical sensor 100 includes an optical circulator 232 optically coupled to an optical coupler 130, thereby replacing... Figure 11 The second optical coupler 230 is used. In several embodiments, the circulator 232 can optically couple the second probe optical signal 211 from the optical coupler 130 to the second sensing fiber Bragg grating (FBG) 220 to output a second spectral overlap optical signal 231 with an intensity level. Figure 12 The sub-spectrum of the second probe optical signal 211 can be reflected by the second sensing fiber Bragg grating 220 and output by the circulator 232 as a second spectral overlap optical signal 231. The intensity level of the second spectral overlap optical signal 231 can correspond to the overlap between the second probe spectrum 211 and the second sensing spectrum, or to the spectral characteristics of the probe fiber Bragg grating 110 and the second sensing fiber Bragg grating 220. The circulator 232 can output the second spectral overlap optical signal 231 to the second optical power regulator 240 to change the sensitivity of the second sensing fiber Bragg grating 220 and provide a second optical output signal 241 to the second optical signal channel (CH2). By providing the circulator 232, the optical power of the second probe optical signal 211 is not split by the optical coupler, thus having higher power or intensity. This results in the second optical output signal 241 having higher power or intensity. In this setup, both the first sensing fiber Bragg grating 120 and the second sensing fiber Bragg grating 220 can receive incident light signals with approximately the same intensity.

[0106] Figure 13A The power intensity distribution is shown in an example of using a second optical coupler 230 for a second sensing fiber Bragg grating 220. Figure 13B Another example of using an optical circulator for the second sensing fiber Bragg grating 220 is shown. (Reference) Figure 13AThe probe optical signal 172 (100% power intensity) from the probe fiber Bragg grating 110 is split into a first optical signal 174 (50% power intensity) towards the sensing fiber Bragg grating 120 and a second optical signal 176 (50% power intensity) towards the second optical coupler 230 by using a first optical coupler 130 (assuming a coupling ratio of 3 dB and negligible insertion / coupling loss). The first optical signal 174 (50% power intensity) is reflected by the sensing fiber Bragg grating 120 (assuming a reflectivity of 100%), passes through the first optical coupler 130 again, and forms an optical signal 178 (25% power intensity), which is output to the optical power conditioner 140. For the second optical coupler 230, the second optical signal 176 (50% power intensity) is provided as the second probe optical signal 272 (50% power intensity), and is further split into a third optical signal 274 (25% power intensity) and a fourth optical signal 276 (25% power intensity) by using the second optical coupler 230 (assuming a coupling ratio of 3 dB and negligible insertion / coupling loss). The third optical signal 274 (25% power intensity) is reflected by the second sensing fiber Bragg grating 220 (assuming a reflectivity of 100%), passes through the second optical coupler 230 again, and forms an optical signal 278 (12.5% ​​power intensity), which is output to the second optical power conditioner 240. It can be seen that the optical signal 278 (12.5% ​​power intensity) reflected by the second sensing fiber Bragg grating 220 has half the power intensity of the optical signal 178 (25% power intensity) reflected by the sensing fiber Bragg grating 120. However, with the addition of each additional optical coupler, the reduction in optical power allows the optical sensor 100 to be further extended to multiple sensing fiber Bragg gratings. In this setup, the first optical signal 174 (50% power intensity) input to the first sensing fiber Bragg grating 120 and the third optical signal 274 (25% power intensity) input to the second sensing fiber Bragg grating 220 can have unequal power intensities (or be outside similar ranges). In contrast, in Figure 13B In the dual-channel setup shown, the optical input signals received by the two sensing fiber Bragg gratings can have similar power intensities, as described below.

[0107] refer to Figure 13BThe probe optical signal 172 (100% power intensity) from the probe fiber Bragg grating 110 is split by the first optical coupler 130 (assuming a coupling ratio of 3 dB and negligible insertion / coupling loss) into a first optical signal 174 (50% power intensity) directed toward the sensing fiber Bragg grating 120 and a second optical signal 176 (50% power intensity) directed toward the circulator 232. The first optical signal 174 (50% power intensity) is reflected by the sensing fiber Bragg grating 120 (assuming a reflectivity of 100%), passes through the first optical coupler 130 again, and forms an optical signal 178 (25% power intensity), which is output to the optical power conditioner 140. For circulator 232, a second optical signal 176 (50% power intensity) is provided as a second probe optical signal 272 (50% power intensity). This second probe optical signal 272 is directed toward circulator 232 and coupled to the second sensing fiber Bragg grating 220 as a third optical signal 274 (50% power intensity, assuming negligible coupling loss of the circulator). Optical signal 274 (50% power intensity) is reflected by the second sensing fiber Bragg grating 220 (assuming 100% reflectivity) to form optical signal 278 (50% power intensity), which is output to the second optical power conditioner 240. It can be seen that the optical signal 278 (50% power intensity) reflected by the second sensing fiber Bragg grating 220 has twice the power intensity of the optical signal 178 (25% power intensity) reflected by the sensing fiber Bragg grating 120. In this setup, the first optical signal 174 (50% power intensity) input to the sensing fiber Bragg grating 120 has equal power intensity (or at least within a similar range) to the third optical signal 274 (50% power intensity) input to the second sensing fiber Bragg grating 220. However, this setup does not support further expansion. It should be understood that the above regarding Figure 13A and Figure 13B The description is provided to help understand the flow or distribution of optical power and does not constitute any limitation or constraint on this disclosure.

[0108] Figures 14 to 15C An optical sensing system 50 and an optical sensor 100 according to several other embodiments are illustrated. The optical sensing system 50 may include a light source 80 optically coupled to the optical sensor 100 to provide a source light signal 81. In some embodiments, an optical isolator 82 optically coupled to the light source 80 may be provided.

[0109] The optical sensor 100 may include a probe segment 101 coupled to or in optical communication with a sensing fiber Bragg grating (FBG) 120. The probe segment 101 may include a probe fiber Bragg grating (FBG) 110 in optical communication with a probe optical coupler 132. (Reference) Figure 15AThe probe fiber Bragg grating 110 can define a probe spectrum (S1) that includes a first spectral band (B1). The first spectral band (B1) can be a characteristic of the probe spectrum (S1). The first spectral band (B1) can be symmetrical about a first center wavelength (F1). In some embodiments, the probe fiber Bragg grating can be a chirped fiber Bragg grating (CFBG).

[0110] Still referencing Figure 15A The sensing fiber Bragg grating 120 can also define a sensing spectrum (S2), which includes a second spectral band (B2). The second spectral band (B2) can be a characteristic of the sensing spectrum (S2). The second spectral band (B2) can be symmetrical about a second center wavelength (F2). The sensing fiber Bragg grating 120 can also be a chirped fiber Bragg grating (CFBG). The sensing fiber Bragg grating 120 can be configured to cause a spectral shift or change in the sensing spectrum (S2) or the second spectral band (B2) in response to a change in at least one external parameter acting on the sensing fiber Bragg grating 120.

[0111] In some embodiments, in response to receiving a source optical signal 81 from the probe optical coupler 132, the probe fiber Bragg grating 110 can provide a probe optical signal 111 corresponding to the probe spectrum (S1). The probe fiber Bragg grating 110 can be configured for reflection such that the probe spectrum (S1) includes a spectral peak (S1a) corresponding to the first spectral band (B1). Therefore, the probe spectrum (S1) is a reflectance spectrum. The probe spectrum (S1) allows for reflection of sub-spectrums corresponding to the first spectral band (B1) and attenuation of sub-spectrums outside the first spectral band (B1).

[0112] In some embodiments, the probe optical coupler 132 may also be coupled to the optical coupler 130. The probe optical signal 111 may be provided to the optical coupler 130, which is optically coupled to the sensing fiber Bragg grating 120. In some embodiments, a reference monitor (R') coupled to the optical coupler 130 may be configured to monitor fluctuations in the probe optical signal 111 or the source optical signal 81.

[0113] The sensing fiber Bragg grating 120 can be configured for reflection such that the sensing spectrum (S2) includes a spectral peak (S2a) corresponding to the second spectral band (B2). Therefore, the sensing spectrum (S2) is a reflection spectrum. The sensing spectrum (S2) allows for reflection of the sub-spectrum corresponding to the second spectral band (B2) and attenuation of the sub-spectrum outside the second spectral band (B2).

[0114] In various embodiments, the optical coupler 130 can optically couple the probe optical signal 111 from the probe fiber Bragg grating 110 to the sensing fiber Bragg grating 120 to output a spectrally overlapping optical signal 131 with an intensity level (I12). Figure 15A The spectral overlap signal 131 can correspond to the overlap between the probe spectrum (S1) and the sensing spectrum (S2). The spectral overlap signal 131 can depend on the spectral characteristics of the selected probe fiber Bragg grating 110 and sensing fiber Bragg grating 120. Unlike the previous embodiment, the spectral overlap signal 131 is the overlap between two spectral peaks (S1a and S2a).

[0115] In various embodiments, reference is made to Figure 15A The overlap range (B121 and B122) or the range of overlapping wavelengths between the first spectral band (B1) of the detection spectrum (S1) and the second spectral band (B2) of the sensing spectrum (S2) can correspond to the measurement range of the optical sensor 100. For example, when the optical sensor 100 is in a position such as Figure 15A In the initial state shown, the optical sensor 100 may have a first measurement range (B121) in the first direction 72 and a second measurement range (B122) in the second direction 74, or vice versa. The first measurement range (B121) and the second measurement range (B122) may be equal or substantially equal, therefore the optical sensor 100 may have equal (or similar) measurement ranges (B121 and B122) in both directions 72 / 74. Figure 15B and Figure 15C In other examples of the optical sensor 100 in the initial state shown, the first measurement range (B121) and the second measurement range (B122) may not be equal measurement ranges, and therefore the respective limits of the measurement ranges in both directions 72 / 74 are also not equal.

[0116] refer to Figure 16 The sensor 100's detection segment 101 may further include a second optical coupler 230 optically coupled to the first optical coupler 130 to receive a second detection optical signal 211. In various embodiments, the second detection optical signal 211 may correspond to the detection optical signal 111, but has a lower intensity level. The sensor 100 may also include a second sensing fiber Bragg grating 220 coupled to the second optical coupler 230. In various embodiments, the second optical coupler 230 may optically couple the second detection optical signal 211 from the optical coupler 130 to the second sensing fiber Bragg grating 220 to output a second spectral overlap optical signal 231 with a higher intensity level. Figure 16The second optical coupler 230 can output the second spectral overlap optical signal 231 to the second optical power regulator 240. Similarly, a third sensing fiber Bragg grating 320 and a third optical coupler 330 can also be provided to the sensor 100. Similarly, the third optical coupler 330 can optically couple the third probe optical signal 311 from the second optical coupler 230 to the third sensing fiber Bragg grating 320 to output a third spectral overlap optical signal 331 with an intensity level. The third optical coupler 330 can output the third spectral overlap optical signal 331 to the third optical power regulator 340. Therefore, multiple sensing fiber Bragg gratings and their respective multiple optical couplers can be added to the sensor 100 in parallel arrangement. In other embodiments, all individual optical power regulators (140 / 240 / 340) can be implemented or replaced by a single optical power adjustment unit having multiple channels to connect individual spectral overlap optical signals (131 / 231 / 331), etc.

[0117] Figure 17 Another optical sensor 100 according to several embodiments is shown. The optical sensing system 50 may include a light source 80 optically coupled to the optical sensor 100 to provide a source light signal 81. In some embodiments, an optical isolator 82 optically coupled to the light source 80 may be provided. The optical sensor 100 may include a probe segment 101 coupled to or in optical communication with a sensing fiber Bragg grating (FBG) 120. The probe segment 101 may include a probe fiber Bragg grating (FBG) 110 in optical communication with an optical coupler 130. In some embodiments, in response to receiving the source light signal 81 from the optical coupler 130, the probe fiber Bragg grating 110 may provide a probe light signal 111 corresponding to a probe spectrum. The probe fiber Bragg grating 110 may be configured for reflection such that the probe spectrum includes spectral peaks with a specific bandwidth. Therefore, the probe spectrum is a reflectance spectrum.

[0118] In some embodiments, the optical coupler 130 may also be coupled to the sensing fiber Bragg grating 120. The sensing fiber Bragg grating 120 may be configured to undergo a spectral shift or change in the sensing spectrum in response to a change in at least one external parameter acting on the sensing fiber Bragg grating 120. The sensing fiber Bragg grating 120 may be configured in a transmission configuration such that the sensing spectrum includes spectral valleys with a specific bandwidth. Therefore, the sensing spectrum is a transmission spectrum. In various embodiments, the optical coupler 130 may optically couple a probe light signal 111 from the probe fiber Bragg grating 110 to the sensing fiber Bragg grating 120 to output a spectrally overlapped light signal 131 with an intensity level. In various embodiments, the spectrally overlapped light signal 131 may be provided to an optical power regulator 140 to output an optical output signal 141. The optical power regulator 140 may be configured to adjust the baseline (I12) of the intensity level of the spectrally overlapped light signal 131 to change the sensitivity of the optical sensor 100.

[0119] Figures 18 to 19C Another optical sensing system 50 and another optical sensor 100 according to several other embodiments are illustrated. The optical sensing system 50 may include a light source 80 optically coupled to the optical sensor 100 to provide a source light signal 81. In some embodiments, an optical isolator 82 optically coupled to the light source 80 may be provided.

[0120] The optical sensor 100 may include a probe segment 101 coupled to or in optical communication with a sensing fiber Bragg grating (FBG) 120. The probe segment 101 may include a probe fiber Bragg grating (FBG) 110 in optical communication with a probe optical coupler 132. The probe fiber Bragg grating 110 may define a probe spectrum (S1) including a first spectral band (B1). The first spectral band (B1) may be characteristic of the probe spectrum (S1). The first spectral band (B1) may be symmetrical about a first center wavelength (F1). In some embodiments, the probe fiber Bragg grating may be a chirped fiber Bragg grating (CFBG).

[0121] The sensing fiber Bragg grating 120 can also define a sensing spectrum (S2), which includes a second spectral band (B2). The second spectral band (B2) can be a feature of the sensing spectrum (S2). The second spectral band (B2) can be symmetrical about a second center wavelength (F2). The sensing fiber Bragg grating 120 can also be a chirped fiber Bragg grating (CFBG). The sensing fiber Bragg grating 120 can be configured to cause a spectral shift or change in the sensing spectrum (S2) or the second spectral band (B2) in response to a change in at least one external parameter acting on the sensing fiber Bragg grating 120.

[0122] In some embodiments, in response to receiving a source optical signal 81 (or a portion of the source optical signal 81) from the probe optical coupler 132, the probe fiber Bragg grating 110 can provide a probe optical signal 111 corresponding to the probe spectrum (S1). Figure 18 and Figure 19A As shown, the probe fiber Bragg grating 110 can be configured for reflection such that the probe spectrum (S1) includes a spectral peak (S1a) corresponding to the first spectral band (B1). The probe spectrum (S1) is a reflection spectrum. The probe spectrum (S1) allows for reflection of the sub-spectrum corresponding to the first spectral band (B1) and attenuation of the sub-spectrum outside the first spectral band (B1). A portion of the source optical signal 81 corresponding to the first spectral band (B1) is reflected by the probe fiber Bragg grating 110 as the probe optical signal 111.

[0123] The sensing fiber Bragg grating 120 can be configured for transmission such that the sensing spectrum (S2) includes a spectral valley (S2a) corresponding to the second spectral band (B2). Therefore, the sensing spectrum (S2) is a transmission spectrum. The sensing spectrum (S2) allows transmission of sub-spectrums outside the second spectral band (B2) and reflection / attenuation of sub-spectrums within the second spectral band (B2). Thus, a portion of the probe light signal 111 corresponding to the second spectral band (B2) is reflected by the sensing fiber Bragg grating 120, while allowing transmission of the remaining sub-spectrums.

[0124] In some embodiments, the probe optical coupler 132 may also be coupled to the optical coupler 130. The probe optical signal 111 may be provided to the optical coupler 130, which is optically coupled to the sensing fiber Bragg grating 120. In various embodiments, the optical coupler 130 may optically couple the probe optical signal 111 from the probe fiber Bragg grating 110 to the sensing fiber Bragg grating 120 to output a spectrally overlapping optical signal 131 with an intensity level (I12). Figure 19A The spectral overlap signal 131 can correspond to the overlap between the probe spectrum (S1) and the sensing spectrum (S2). Unlike the previous embodiment, the spectral overlap signal 131 is the overlap between the spectral peak (S1a) from the probe spectrum (S1) and the spectral valley (S2a) from the sensing spectrum (S2).

[0125] In several embodiments, reference is made to Figure 19A The overlap range (B121 and B122) or overlap wavelength range between the first spectral band (B1) of the detection spectrum (S1) and the second spectral band (B2) of the sensing spectrum (S2) can correspond to the measurement range of the optical sensor 100. For example, when the optical sensor 100 is in Figure 19AIn the initial state shown, i.e., F1 = F2 ± BW / 2 (assuming the two fiber Bragg gratings have similar bandwidths BW), the optical sensor 100 can have a first measurement range (B121) in the first direction 72 and a second measurement range (B122) in the second direction 74. The first measurement range (B121) and the second measurement range (B122) can be equal or substantially equal, therefore, the optical sensor 100 can have equal measurement ranges (B121 and B122) in both directions 72 and 74. Figure 19B and Figure 19C In other examples of the optical sensor 100 in the initial state shown, the first measurement range (B121) and the second measurement range (B122) may not be equal measurement ranges, and therefore the respective limits of the measurement ranges of the two along the first and second directions 72 / 74 are not equal.

[0126] refer to Figure 20 The sensor 100's detection segment 101 may further include a second optical coupler 230 optically coupled to the optical coupler 130 to receive a second detection optical signal 211. In various embodiments, the second detection optical signal 211 may correspond to the detection optical signal 111, but has a lower intensity level. The sensor 100 may also include a second sensing fiber Bragg grating 220 coupled to the second optical coupler 230. In various embodiments, the second optical coupler 230 may optically couple the second detection optical signal 211 from the optical coupler 130 to the second sensing fiber Bragg grating 220 to output a second spectral overlap optical signal 231 with an intensity level. Similar to the first optical power regulator 140, the second optical power regulator 240 may be configured to receive the second spectral overlap optical signal 231 from the second sensing fiber Bragg grating 220 to change / adjust the sensitivity of the second sensing fiber Bragg grating 220 and provide a second optical output signal 241 to the second optical signal channel (CH 2). Similarly, a third sensing fiber Bragg grating 320 and a third optical coupler 330 can also be provided to the sensor 100. Similarly, the third optical coupler 330 can optically couple the third probe optical signal 311 from the second optical coupler 230 to the third sensing fiber Bragg grating 320 to output a third spectral overlap optical signal 331 with an intensity level. A third optical power regulator 340 can be configured to receive the third spectral overlap optical signal 331 from the third sensing fiber Bragg grating 320 to change / adjust the sensitivity of the third sensing fiber Bragg grating 320 and provide the third optical output signal 341 to the third optical signal channel (CHN). Therefore, multiple sensing fiber Bragg gratings and their respective multiple optical couplers can be added to the sensor 100 in a parallel arrangement.

[0127] Figure 21The integration of a sensing system 50 according to various embodiments is illustrated. Each optical output signal 141 / 241, or alternatively, spectrally overlapping optical signals 131 / 231, can be received by the respective optical signal channel (CH 1 / CH 2) of the respective optical receiver. In some embodiments, each of the optical receivers may include a photodiode 91, a transimpedance amplifier 93, and an analog-to-digital converter 95. The transimpedance amplifier 93 may be configured to convert an input source current into an equivalent voltage. The analog-to-digital converter 95 from each optical receiver may be replaced by a single analog-to-digital converter unit with a multi-channel configuration, wherein the voltage output from the respective transimpedance amplifier 93 is connected to the single analog-to-digital converter unit. In various embodiments, the analog-to-digital converter 95 may also be coupled to a virtual network computing (VNC) server 97. A user 60 may communicate remotely with the server using a corresponding client application 99 (e.g., a virtual network computing client) to remotely access the sensed data based on client-server technology. In other embodiments, analog-to-digital converter 95 (or a single analog-to-digital conversion unit) may be coupled to a wireless data logger 96 or a wireless recorder capable of communicating with one or more remote devices, such as... Figure 22 As shown. In a further embodiment, the analog-to-digital converter 95 (or a single analog-to-digital conversion unit) may be coupled to the cloud platform 98, such as... Figure 23 As shown. Cloud platform 98 can include cloud servers, such as AWS, Azure, Google, etc., where data is stored or processed.

[0128] In several embodiments, the optical sensor 100 may be configured to be multiplexed. Figure 24 and Figure 25 An optical sensor 100 and an optical sensing system 50 according to several embodiments are illustrated. The optical sensing system 50 may include a light source 80 optically coupled to the optical sensor 100 to provide a source light signal 81. In some embodiments, an optical isolator 82 optically coupled to the light source 80 may be provided.

[0129] Optical sensor 100 may include a detector section 101. Detector section 101 may include multiple detector fiber Bragg gratings (FBGs) coupled in series to form a detector fiber Bragg grating array (FBGA) 160. The detector fiber Bragg grating array 160 may be optically communicated with or coupled to an optical coupler 130. Detector section 101 may be coupled to, or optically communicate with, multiple sensor fiber Bragg gratings coupled in series to form a sensor fiber Bragg grating array (FBGS) 170.

[0130] refer to Figure 25 A probe fiber Bragg grating array 160 or more probe fiber Bragg gratings can define a probe spectrum (S1) comprising a plurality of first spectral bands (B1 / B1'). The plurality of first spectral bands (B1 / B1') can be characteristics of the probe spectrum (S1). A first spectral band (B1) can be symmetrical about a first center wavelength (F1). Another first spectral band (B1') can be symmetrical about another first center wavelength (F1'). In some embodiments, each of the plurality of probe fiber Bragg gratings can be a chirped fiber Bragg grating (CFBG).

[0131] Still referencing Figure 25 The sensing fiber Bragg grating array 170 can also define a sensing spectrum (S2), which includes a plurality of second spectral bands (B2 / B2'). The plurality of second spectral bands (B2 / B2') can be features of the sensing spectrum (S2). A second spectral band (B2) can be symmetrical about a second center wavelength (F2). Another second spectral band (B2') can be symmetrical about another second center wavelength (F2'). Each of the plurality of sensing fiber Bragg gratings can also be a chirped fiber Bragg grating (CFBG). The sensing fiber Bragg grating array 170 or the plurality of sensing fiber Bragg gratings can be configured to cause a spectral shift or change in the sensing spectrum (S2) in response to a change in at least one external parameter acting on at least one of the plurality of sensing fiber Bragg gratings.

[0132] In some embodiments, in response to receiving a source optical signal 81 from the optical coupler 130, the probe fiber Bragg grating array 160 can provide a probe optical signal 111 corresponding to the probe spectrum (S1). The probe optical signal 111 can be provided to the optical coupler 130, which is optically coupled to the sensing fiber Bragg grating array 170. In some embodiments, a reference monitor (R') coupled to the optical coupler 130 can be configured to monitor fluctuations in the probe optical signal 111 or the source optical signal 81.

[0133] In some embodiments, the optical sensor 100 and the optical sensing system 50 can be configured as multiplexed sensing or multiplexing. Therefore, multiple fiber Bragg gratings can be provided on a single optical fiber for multiple measurements along the fiber. For example... Figure 24 and Figure 25As shown, the probe fiber Bragg grating array 160 can be configured for transmission, such that the probe spectrum (S1) includes multiple spectral valleys (S1a / S1a') corresponding to the plurality of first spectral bands (B1 / B1'). Therefore, the probe spectrum (S1) is a transmission spectrum. Similarly, the sensing fiber Bragg grating array 170 can be configured for reflection, such that the sensing spectrum (S2) includes multiple spectral peaks (S2a / S2a') corresponding to the plurality of second spectral bands (B2 / B2'). Therefore, the sensing spectrum (S2) is a reflection spectrum.

[0134] In several embodiments, the optical coupler 130 can optically couple the probe optical signal 111 from the probe fiber Bragg grating array 160 to the sensing fiber Bragg grating array 170 to output a spectrally overlapping optical signal 131 with an intensity level. Figure 25 The spectral overlap optical signal 131 can correspond to multiple overlaps (133 / 133') between the probe spectrum (S1) and the sensing spectrum (S2), such as... Figure 25 As shown.

[0135] In several embodiments, reference is made to Figure 25 Multiple overlapping ranges (B12 / B12') between the first spectral band (B1 / B1') in the probe spectrum (S1) and their respective second spectral bands (B2 / B2') in the sensing spectrum (S2) can determine multiple different measurement ranges of the optical sensor 100 for sensing multiple fiber Bragg gratings in the fiber Bragg grating array 170. In several embodiments, adjacent measurement ranges (B12 and B12') among the multiple different measurement ranges can be separated by a guard band (GB). The guard band is provided for multiplexing of the optical sensor. This allows all channels to exist optically in a single fiber without interfering with each other and can be separated into individual fibers or channels by optical demultiplexing or filtering.

[0136] like Figure 25As shown, in the initial or neutral state where the sensing fiber Bragg grating array 170 is unaffected by external influences, the first spectral bands (B1 / B1') may be spaced apart relative to their respective second spectral bands (B2 / B2'). Furthermore, in the initial state, the first spectral bands (B1 / B1') may overlap with their respective second spectral bands (B2 / B2'). In some embodiments, the second spectral bands (B2 / B2') may include a longer wavelength range compared to their respective first spectral bands (B1 / B1'). For example, the first spectral band (B1) may be between the spectral limits of 1517 nm and 1523 nm, with a first center wavelength (F1) of 1520 nm. The corresponding second spectral band (B2) may be between the spectral limits of 1520 nm and 1526 nm, with a second center wavelength (F2) of 1523 nm. Similarly, the first spectral band (B1') can be between the spectral limits of 1544 nm and 1550 nm, with another first center wavelength (F1') at 1547 nm. The corresponding second spectral band (B2') can be between the spectral limits of 1547 nm and 1553 nm, with another second center wavelength (F2') at 1550 nm.

[0137] In several embodiments, the first spectral band (B1 / B1') and each of the respective second spectral bands (B2 / B2') may have the same bandwidth (BW), i.e., 6 nanometers. In several embodiments, in the initial state, the second center wavelength (F2) at 1523 nanometers may be aligned with the spectral limit (1523 nanometers) of the first spectral band (B1). Similarly, another second center wavelength (F2') at 1550 nanometers may be aligned with the spectral limit (1550 nanometers) of the first spectral band (B1').

[0138] Figure 26Another example of an optical sensor 100 for multiplexing is shown, which has three distinct overlapping spectra or three distinct overlaps between a first spectral band and a second spectral band between the probe spectrum (S1) and the sensing spectrum (S2). For example, the three probe fiber Bragg gratings in the probe fiber Bragg grating array 160 may have center wavelengths (F1, F1', F1'') at 1520 nm, 1532 nm, and 1544 nm, i.e., adjacent probe fiber Bragg gratings are spaced 12 nm apart. The three sensing fiber Bragg gratings in the sensing fiber Bragg grating array 170 for sensing / monitoring purposes may have center wavelengths (F2, F2', F2'') at 1523 nm, 1535 nm, and 1547 nm, i.e., adjacent sensing fiber Bragg gratings are also spaced 12 nm apart. In this example, the spectral width or bandgap (BW) of all fiber Bragg gratings is considered to be the same, i.e., 6 nanometers, and the center wavelength of the probe fiber Bragg grating array is selected relative to the sensing fiber Bragg grating array (F1 = F2 - BW / 2) to allow the sensor 100 to have a symmetrical measurement range, such as for the measurement of tensile and compressive strain. In the above description, the set of center wavelengths (F1, F1', F1'') of the fiber Bragg grating array can be selected to be on the shorter wavelength side of the set of center wavelengths (F2, F2', F2'') of the sensing fiber Bragg grating array, so that, in their respective initial states, these three distinct overlapping spectra can extend from (F1 + BW / 2) nanometers to (F2 + BW / 2) nanometers. In other embodiments, the set of center wavelengths (F1, F1', F1'') of the probe fiber Bragg grating array can be selected to be on the longer wavelength side of the set of center wavelengths (F2, F2', F2'') of the sensing fiber Bragg grating array, i.e., F1 = F2 + BW / 2. In this case, for the same example, the center wavelengths F1, F1', and F1'' of the probe fiber Bragg grating array can be located at 1526 nm, 1538 nm, and 1550 nm, respectively. Furthermore, in their respective initial states, these three distinct overlapping spectra can extend from (F2-BW / 2) nm to (F1-BW / 2) nm. In other embodiments, the selection of the center wavelength and bandwidth (spectral characteristics) of the individual fiber Bragg gratings in the probe fiber Bragg grating array 160 or the sense fiber Bragg grating array 170 is not limited and can be determined according to the measurement range required for a specific application, and subsequent sensor demodulation can be performed accordingly.

[0139] exist Figure 26In the initial state shown, the first overlap 1311 (CH 1) between the probe fiber Bragg grating and the sense fiber Bragg grating extends from 1523 nm to 1526 nm. Similarly, the second overlap 1312 (CH 2) extends from 1535 nm to 1538 nm, and the third overlap 1313 (CH 3) extends from 1547 nm to 1550 nm. In the example, when channel 1 (CH 1) is used to measure tensile strain, the spectrum of the first sense fiber Bragg grating (1520 nm to 1526 nm) can be shifted or redshifted towards longer wavelengths, with the first overlap region 1311 increasing to a maximum of 6 nm, i.e., between 1523 nm and 1529 nm, before saturating. Simultaneously, when channel 2 (CH 2) is used to measure compressive strain, the spectrum of the second sensing fiber Bragg grating (1532 nm to 1538 nm) can be shifted (blue shift) towards shorter wavelengths, with the second overlap region 1312 decreasing to a minimum of 0 nm with increasing compression, i.e., at 1529 nm to 1535 nm (the maximum measurement compression range). It is noteworthy that a threshold wavelength spacing (SP1), such as 12 nm, may be required between adjacent sensing fiber Bragg gratings to avoid unnecessary interference. Similarly, a threshold wavelength spacing (SP2), such as 12 nm, may also be required between adjacent sensing fiber Bragg gratings to avoid unnecessary interference. Therefore, by providing their respective threshold wavelength spacings, the demultiplexing process can be simplified. However, a larger wavelength spacing limits the maximum number of channels that can be accommodated within a given spectrum. Therefore, there is a trade-off between the wavelength spacing between adjacent fiber Bragg gratings and the maximum number of channels that can be set.

[0140] refer to Figure 27 A spectrometer 92 coupled to the optical coupler 130 may be provided. The spectrometer 92 may be configured as a light receiver to extract or access the spectrum from the spectrally overlapping light signal 131 and analyze the different spectral overlaps present in the spectrally overlapping light signal 131 for processing as individual or separate optical channels. In several embodiments, an optical power modulator may be coupled between the spectrometer 92 and the optical coupler 130 to adjust the intensity baseline of the spectrally overlapping light signal 131, thereby altering the sensitivity of the optical sensor 100.

[0141] In such Figure 28In a further embodiment shown, an optical passive device 94 may be provided as an optical receiver, optically coupled to an optical coupler 130 to receive the spectrally overlapping optical signal 131. The optical passive device 94 may include at least one or a combination of the following: an optical demultiplexer (DEMUX), an arrayed waveguide grating (AWG), a wavelength selective switch (WSS), and an optical bandpass filter (OBPF). The optical passive device 94 may be configured to receive and separate different wavelengths (or corresponding mini spectrum overlap bands) of the spectrum from the spectrally overlapping optical signal 131, thereby extracting multiple optical channels from the spectrally overlapping optical signal 131. Each of the optical channels, after demultiplexing, may be optically coupled to its respective optical power regulator 140 / 240 / 340, such as its respective variable optical attenuators (VOAs). Each of the resulting optical channels can be used as an independent channel for measuring the measurand, or each of the resulting optical channels can be combined with each other, that is, a measurand measured in one channel can be compensated for another measurand measured in another channel, for example, temperature fluctuations, general parameter compensation, vibration, or any other unwanted signal present at the mounting location. In other embodiments, the spectrally overlapping optical signal 131 can be coupled to an optical power regulator before entering an optical demultiplexing (or filtering) stage to separate the small spectral overlap bands as their respective optical channels.

[0142] Figure 29The integration of a sensing system 50 according to several embodiments is illustrated. Each optical signal channel (CH 1 / CH 2 / CH 3) may also be coupled to a respective photodiode 91 to convert the optical input signal into an electrical (current) signal, which is then converted into an equivalent voltage by a transimpedance amplifier 93, and finally converted into an equivalent digital signal by an analog-to-digital converter 95. The transimpedance amplifier 93 may be implemented using an operational amplifier. The photodiode 91 and the transimpedance amplifier 93 may be integrated into a single electronic circuit, a semiconductor chip, or a printed circuit board (PCB). In other embodiments, a single analog-to-digital converter may be configured to receive the outputs from multiple transimpedance amplifiers 93 in parallel channels. In some cases, the analog-to-digital converter may also be integrated with other components (photodiodes, transimpedance amplifiers) into a single circuit and used as a single unit of a demodulation component. In several embodiments, the analog-to-digital converter 95 may be further coupled to a virtual network computing (VNC) server 97. A user 60 may use a corresponding client application 99 (e.g., a virtual network computing client) to remotely access the sensing data based on client-server technology.

[0143] Sensing data and measurement

[0144] The following sections present some of the data collected during the experiments. Multiple experiments were performed to obtain data under strain, temperature, and vibration test conditions. For each experiment, corresponding to... Figure 2 and Figure 8 The sensor used in the illustrated embodiment is shown.

[0145] Figure 30 and Figure 31 The diagrams show spectral measurements of the light source, the chirped fiber Bragg grating being detected, and the chirped fiber Bragg grating being sensed using a spectrometer. (Reference) Figure 30 Figure 1901 illustrates two spectra of a typical light source. As the drive current increases (from 50 mA to 100 mA), the light output power of the light source increases, and the peak wavelength (or inflection point wavelength) of the spectrum shifts towards shorter wavelengths. Therefore, the light source, drive current, and their respective spectra can be selected or adjusted according to application requirements to set the desired optical power and peak wavelength. Preferably, the parameters of the fiber Bragg grating or chirped fiber Bragg grating, such as their respective spectral bands and spectral overlap, can be located on the rising or falling side of the spectrum.

[0146] refer to Figure 31Figure 1902 shows the spectra of the probed and sensed chirped fiber Bragg gratings. The probed chirped fiber Bragg grating (CFBG1) used for probed purposes is set to transmission mode, and its probed spectrum is shown in Figure 1902-01, including the spectral peaks. The sensed chirped fiber Bragg grating (CFBG1') used for sensed purposes is set to reflection mode, and its sensed spectrum is shown in Figure 1902-02, including the spectral valleys.

[0147] After the optical components are arranged accordingly, the resulting spectrally overlapping optical signal is expected to respond in the form of intensity modulation according to the external parameters acting on the sensing chirped fiber Bragg grating (CFBG1'). Figure 32 This illustrates the phenomenon of spectral (spectral overlap light signal) shift or movement under different applied tensile strain values. Figure 32 The first section 2001 represents the spectral evolution without power adjustment (without a variable optical attenuator). Spectral broadening was observed as the applied tensile strain increased from 0 microstrain to 450 microstrain. Figure 32 Section 2002 illustrates a similar trend in the spectrum (spectrally overlapping light signal) with a variable optical attenuator, where the initial baseline intensity of the spectral overlapping signal is reduced by the variable optical attenuator, resulting in a spectral shift under applied tensile strain. Therefore, the sensor sensitivity can be easily adjusted according to the measurement-related application.

[0148] Figure 33 and Figure 34 This diagram illustrates an exemplary optical response of an optical sensor obtained under a range of strain applied. Optical responses were recorded for optical sensors with different baseline optical power values ​​(adjusted by a variable optical attenuator) for spectrally overlapping optical signals. The data graph shows the variation in optical output power (or intensity level) over the applied strain (tension) range for optical sensors with different baseline optical powers. The baseline optical power represents the initial spectral overlap between the probe chirped fiber Bragg grating and the sense chirped fiber Bragg grating. Figure 33 As shown, the first group 2301 of the optical response illustrates strain sensing behavior at baseline optical powers of 2.4 nanowatts (nW), 5.9 nanowatts, 8.5 nanowatts, 15.1 nanowatts, and 22.5 nanowatts. Figure 34 As shown, the second set 2302 of the optical response illustrates strain sensing behavior at relatively high baseline optical powers, namely 31.3 nanowatts, 55.6 nanowatts, and 101.7 nanowatts. Since the measurement is based on the spectral overlap of two fiber Bragg gratings (i.e., a probe and a sense chirped fiber Bragg grating), the measurement range depends on the spectral bands of the fiber Bragg gratings involved.

[0149] Figure 35The diagram shows the linear relationship between sensor sensitivity (the change in optical output power per unit microstrain) and the sensor's baseline optical power. Observations reveal that for every 1 nanowatt increase in the optical sensor's baseline optical power, the corresponding strain sensitivity increases by approximately 0.72 picowatts per microstrain. After optical characterization, the optical sensor is configured to function as an optical sensing and detection unit (or detector), such as... Figure 8 As shown, this is for use in strain, vibration, and temperature measurements as described in subsequent chapters. The analog-to-digital converter and transimpedance amplifier are powered by a +5 volt (V) supply voltage.

[0150] Figures 36 to 38 This diagram illustrates the response of an optical sensing system or detector to strain, with three distinct data sets collected, denoted as Segment 2701, Segment 2702, and Segment 2703. The strain test was conducted in a laboratory setting using a cantilever beam, with reference strain readings collected via an electrical strain gauge. Segment 2701 represents the response of the integrated optical sensing system (or detector) to tensile strain 2701-01 and compressive strain 2701-02, exhibiting a moderate baseline. The strain range covered by this test reaches approximately 400 microstrains. Segment 2702 then represents the response of the integrated optical sensing system to tensile strain 2702-01 and compressive strain 2702-02, exhibiting a relatively low baseline. The test revealed a decrease in the strain sensitivity of the integrated optical sensing system. Furthermore, the third section 2703 represents the strain response of the integrated optical sensing system set at three different baselines (denoted as 2703-01, 2703-02, and 2703-03, respectively). Observations revealed that the higher baseline voltage of the optical sensor corresponds to higher strain sensitivity.

[0151] Figure 39 and Figure 40 The response of the optical sensing system is shown for an extended range of applied strain. Section 2401 tests tensile strain up to approximately 3000 microstrains, and section 2402 tests a range of approximately 2300 microstrains, including both tensile and compressive strains. Both plots demonstrate a good linear response to strain within the given range.

[0152] Choosing a relatively high baseline power makes the sensor more sensitive to strain, but it limits the overall measurement range of the optical sensing system (given a given set of electronic components). This is because the analog-to-digital converter and transimpedance amplifier are set to use a fixed DC supply voltage (e.g., +5V), which may lead to saturation during sensing. Therefore, lowering the power or intensity baseline provides a larger or longer measurement range before saturation occurs. Thus, the proposed optical sensor and optical sensing system can achieve an adjustable trade-off between sensitivity (strain) and measurement range (for a given set of electronic components) during sensing. Furthermore, appropriate algorithms can be implemented through edge processing to improve the measurement resolution of the optical sensor, which depends on the parameters of the electronic components involved and the responsivity of the photodiode, etc.

[0153] In several embodiments, based on a series of sensing data collected under multiple test measurements, such as a series of optical sensing data under a given strain condition, the sensitivity of the sensor under different baseline conditions can be determined, and thus can be used to construct one or more datasets. Figure 41 and Figure 42 An example is shown, where a strain sensitivity dataset is recorded over a certain range of sensor baseline voltages (corresponding to light intensity baselines). It can be seen that for relatively high baseline voltages, the strain sensitivity begins to saturate (forming an inflection point or plateau) near the supply voltage (i.e., +5 volts). As an example, the sensor baseline is maintained between 1 and 3 volts to provide sufficient range for tensile and compressive strain measurements. After completing the dataset, a machine learning model can be trained to predict the sensor sensitivity under new baseline conditions. This is for illustrative purposes only. Figure 41 The first segment 2501 in the text shows the logarithmic fit in the recorded dataset, while Figure 42 The second section 2502 in the figure shows a polynomial fit of the same dataset.

[0154] The proposed optical sensor and optical sensing system are also applicable to vibration measurement. In vibration experiments, a sensing chirped fiber Bragg grating is attached to a cantilever beam, which is subjected to external vibrations (artificially applied) at different timestamps. Vibrations 1 through 5 are applied one after another or sequentially, and compared with the initial condition without vibration. Continuous data is acquired in real time using the optical sensing system at a fixed sampling frequency, where the sampling frequency (i.e., the number of samples per second) depends on the resolution (i.e., the number of bits) of the analog-to-digital converter.

[0155] Figure 43 The first segment 2601 is shown, which represents vibration data captured in the time domain, where the Y-axis represents or corresponds to the amplitude of the applied vibration. Figure 44The second section, 2602, is shown, representing the vibration data analyzed in the frequency domain by performing a Fourier transform on the time-domain data. Observations reveal that all frequency-domain spectra resonate at approximately 3.3 Hz, which can represent the resonant frequency of the cantilever beam. The measurable or detectable resonant frequency depends on the sampling rate, which is limited by the Nyquist criterion. Therefore, the feasibility of using optical sensors for vibration measurement is demonstrated, which is highly valuable for dynamic strain measurement in a variety of industrial applications.

[0156] The proposed optical sensor and optical sensing system can also be used for temperature measurement. In temperature experiments, a chirped fiber Bragg grating sensor encapsulated in a loose tube is placed together with a thermocouple sensor inside a heating chamber. The thermocouple records the actual temperature readings around the chirped fiber Bragg grating inside the heating chamber, while the optical sensing system continuously captures real-time data and encodes the temperature information as its intensity changes. Figure 45 This illustrates the response of the optical sensor to temperature changes (in both heating and cooling directions, within the range of room temperature to approximately 75 degrees Celsius). In other applications, optical sensors and optical sensing systems can also be used to measure and characterize a variety of parameters, including but not limited to strain, temperature, vibration, pressure, and refractive index.

[0157] All examples described herein, whether apparatus, method, material, or product, are shown for illustrative and understanding purposes and are not intended to be limiting or exhaustive. Modifications can be made by those skilled in the art without departing from the scope of the claims.

Claims

1. An optical sensor, comprising: A probe fiber Bragg grating, which can be coupled to a light source, defines a probe spectrum, and is configured to provide a probe light signal corresponding to the probe spectrum; A sensing fiber Bragg grating, the sensing fiber Bragg grating defining a sensing spectrum, wherein a spectral shift in the sensing spectrum responds to a change in at least one external parameter acting on the sensing fiber Bragg grating; An optical coupler that couples the probe optical signal to the sensing fiber Bragg grating to output a spectrally overlapping optical signal, wherein the intensity level of the spectrally overlapping optical signal corresponds to the overlap between the probe spectrum and the sensing spectrum; An optical power regulator coupled to the optical coupler, the optical power regulator being configured to adjust the baseline of the intensity level to change the sensitivity of the optical sensor.

2. The optical sensor of claim 1, wherein the probe fiber Bragg grating is in a transmission configuration to provide the probe optical signal, wherein the probe optical signal includes spectral valleys.

3. The optical sensor of claim 1, wherein the probe fiber Bragg grating is in a reflective configuration to provide the probe optical signal, and wherein the probe optical signal includes spectral peaks.

4. The optical sensor according to claim 2 or 3, wherein the sensing fiber Bragg grating is in a reflective configuration, and wherein the sensing spectrum includes spectral peaks.

5. The optical sensor of claim 3, wherein the sensing fiber Bragg grating is in a transmission configuration, and wherein the sensing spectrum includes spectral valleys.

6. The optical sensor according to any one of claims 1 to 5, wherein the detection spectrum includes a first spectral band symmetrical about a first center wavelength, and wherein the sensing spectrum includes a second spectral band symmetrical about a second center wavelength, and wherein the first center wavelength is spaced apart from the second center wavelength.

7. The optical sensor of claim 6, wherein, in the initial state, the second center wavelength of the sensing fiber Bragg grating is aligned with the spectral boundary of the first spectral band.

8. The optical sensor according to any one of claims 6 to 7, wherein the first spectral band has the same bandwidth as the second spectral band.

9. The optical sensor according to any one of claims 6 to 8, wherein the first spectral band and the second spectral band are located on one of the rising side and the falling side, wherein the rising side and the falling side are sides of the reference spectrum of the light source.

10. The optical sensor according to any one of claims 6 to 9, wherein the overlap between the first spectral band and the second spectral band corresponds to the measurement range of the optical sensor.

11. The optical sensor according to any one of claims 6 to 10, wherein when the sensing fiber Bragg grating is in its initial state, the first spectral band overlaps with the second spectral band.

12. The optical sensor according to any one of claims 1 to 11, further comprising a second sensing fiber Bragg grating coupled to the optical coupler, the second sensing fiber Bragg grating defining a second sensing spectrum, wherein a spectral shift in the second sensing spectrum responds to a change in at least one external parameter acting on the second sensing fiber Bragg grating.

13. The optical sensor of claim 12 further includes a circulator that couples a second probe optical signal from the optical coupler to the second sensing fiber Bragg grating to output a second spectral overlap optical signal, wherein the intensity level of the second spectral overlap optical signal corresponds to the overlap between the probe spectrum and the second sensing spectrum.

14. The optical sensor of claim 12, further comprising a second optical coupler, the second optical coupler coupling a second probe optical signal from the optical coupler to the second sensing fiber Bragg grating to output a second spectral overlap optical signal, wherein the intensity level of the second spectral overlap optical signal corresponds to the overlap between the probe spectrum and the second sensing spectrum.

15. The optical sensor of claim 14, wherein the second detection optical signal includes a branch of the detection optical signal, the branch of the detection optical signal having a lower power intensity than the detection optical signal.

16. The optical sensor according to any one of claims 1 to 15, further comprising a plurality of optical couplers coupled to a plurality of sensing fiber Bragg gratings, each of the plurality of optical couplers being coupled to the optical coupler in a parallel arrangement.

17. The optical sensor according to any one of claims 1 to 16, wherein the optical coupler is a 2×2 optical coupler.

18. The optical sensor according to any one of claims 1 to 17, further comprising: Multiple probe fiber Bragg gratings are coupled in series to form a probe fiber Bragg grating array; and a plurality of sensing fiber Bragg gratings, the plurality of sensing fiber Bragg gratings being coupled in series to form a sensing fiber Bragg grating array, wherein the spectral shift in the sensing spectrum is in response to a change in at least one external parameter acting on at least one of the plurality of sensing fiber Bragg gratings.

19. The optical sensor of claim 18, wherein the detection spectrum includes a plurality of first center frequencies and a plurality of respective first spectral bands, and the sensing spectrum includes a plurality of second center frequencies and a plurality of respective second spectral bands.

20. The optical sensor of claim 19, wherein the plurality of overlapping ranges between the probe spectrum and the sensing spectrum correspond to a plurality of different measurement ranges of the optical sensor.

21. The optical sensor of claim 20, wherein adjacent measurement ranges in the plurality of different measurement ranges are separated by their respective protective bands.

22. The optical sensor according to any one of claims 1 to 20, further comprising a reference monitor coupled to the optical coupler, the reference monitor being configured to monitor fluctuations in the probe light signal.

23. The optical sensor according to any one of claims 1 to 21, wherein at least one or both of the probe fiber Bragg grating and the sensing fiber Bragg grating comprise a chirped fiber Bragg grating.

24. The optical sensor according to any one of claims 1 to 22, wherein the external parameters acting on the sensing fiber Bragg grating include at least one of strain, temperature, vibration, and refractive index.

25. An optical sensing system, comprising: The optical sensor according to any one of claims 1 to 24; as well as A light receiver, configured to receive the intensity level of the spectrally overlapping light signal from the optical sensor.

26. The optical sensing system of claim 25, wherein the sensing fiber Bragg grating is located away from the detection section, and the detection section includes the optical coupler and the sensing fiber Bragg grating.

27. The optical sensing system of any one of claims 25 or 26 further comprises a light source defining a reference spectrum, wherein the inflection point wavelength of the reference spectrum is located outside a first spectral band of the detection spectrum, and wherein the inflection point wavelength of the reference spectrum is located outside a second spectral band of the sensing spectrum.

28. The optical sensing system according to any one of claims 25 to 27, further comprising an optical isolator coupled between the light source and the probe fiber Bragg grating.

29. The optical sensing system according to any one of claims 25 to 28, wherein the light receiver comprises: A photodiode configured to convert the intensity of the spectrally overlapping light signal into a current signal; A transimpedance amplifier, configured to amplify the current signal and convert the current signal into a voltage signal; as well as An analog-to-digital converter, configured to convert the voltage signal into an equivalent digital signal.

30. The optical sensing system according to any one of claims 25 to 29 further includes a server, the server being in signal communication with the optical receiver.

31. The optical sensing system according to any one of claims 25 to 30, further comprising a wireless data logger, the wireless data logger being in signal communication with the optical receiver, the wireless data logger being capable of communicating with at least one remote device.

32. The optical sensing system according to any one of claims 25 to 31 further includes a base station, the base station being in signal communication with the optical receiver, and the base station being capable of communicating with a cloud server.

33. The optical sensing system according to any one of claims 25 to 32, wherein the optical receiver comprises any one of: an optical demultiplexer, an arrayed waveguide grating, a wavelength selective switch, and an optical bandpass filter.

34. The optical sensing system according to any one of claims 25 to 33, wherein the light receiver comprises a spectrometer.

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