Active microphones improve DAS acoustic sensing capabilities

Abstract

Aspects of the present disclosure describe DFOS / DAS systems, methods, and structures that employ active microphones to enhance DAS operational capabilities by using active circuitry to amplify acoustic signals, including voice. The circuitry includes a microphone that collects acoustic signals derived from audio signals in the environment, and a speaker or vibration device driven by an amplifier. The circuitry can be clipped to the fiber and directly contacted via the speaker or vibration device. A microcontroller can be advantageously employed to control the circuitry to reduce power consumption by locally detecting activity and enabling the speaker only when needed. The microcontroller can also transmit other information, such as battery status, in vibration code to the DFOS interrogator.

Description

[Technical field]

[0001] This disclosure relates generally to distributed fiber optic sensing (DFOS), and more particularly to the use of active microphones to enhance distributed acoustic sensing (DAS) capabilities. [Background technology]

[0002] As those skilled in the art will appreciate, (DFOS) systems and techniques are employed in many applications due to their ability to sense vibration and acoustic signals in the vicinity of fiber optic cables and generate a time-stamped data stream of the sensed signals to provide valuable information to decision makers. Given this importance, any techniques and structures that improve the capabilities of DFOS / DAS are welcome additions to the technology. Summary of the Invention

[0003] In accordance with aspects of the present disclosure, an advancement is made in the art toward DFOS / DAS systems, methods, and structures that advantageously find application in a wide variety of sensing applications. In contrast to the prior art, DFOS / DAS systems, methods, and structures in accordance with aspects of the present disclosure employ active microphones to enhance DAS operational capabilities.

[0004] Another aspect of DFOS / DAS systems is the use of active circuitry to amplify acoustic signals, including voice. The circuitry includes a microphone to collect acoustic signals in the environment, and a speaker or vibration device driven by an amplifier. The circuitry can be clipped to the fiber and directly contacted via the speaker or vibration device. A microcontroller can be advantageously employed to control the circuitry to reduce power consumption by detecting activity locally and enabling the speaker only when needed. The microcontroller can also transmit other information, such as battery status, in vibration code to the DFOS interrogator. [Brief description of the drawings]

[0005] A more complete understanding of the present disclosure may be realized by reference to the accompanying drawings herein.

[0006] [Figure 1] FIG. 1 is a schematic diagram of an exemplary arrangement according to an aspect of the present disclosure.

[0007] [Figure 2(A)] FIG. 13 illustrates example thresholds for enabling / disabling speakers according to aspects of the disclosure. [Figure 2(B)] FIG. 13 illustrates example thresholds for enabling / disabling speakers according to aspects of the disclosure. [Figure 2(C)] FIG. 13 illustrates example thresholds for enabling / disabling speakers according to aspects of the disclosure.

[0008] [Figure 3(A)] 1A-1C show a schematic diagram and a flow diagram illustrating the operation of an exemplary on / off switch controlled by an MCU, respectively, in accordance with aspects of the present disclosure. [Figure 3(B)] 1A-1C show a schematic diagram and a flow diagram illustrating the operation of an exemplary on / off switch controlled by an MCU, respectively, in accordance with aspects of the present disclosure.

[0009] [Figure 4] FIG. 13 is a schematic diagram illustrating an MCU controlling amplifier gain using ADC data, according to an aspect of the present disclosure.

[0010] [Diagram 5] 1 is a schematic diagram illustrating an MCU for controlling amplifier gain using multiple thresholds, according to an aspect of the disclosure.

[0011] Exemplary embodiments are more fully described in the drawings and detailed description, however, embodiments in accordance with the present disclosure may be embodied in various forms and are not limited to the specific or exemplary embodiments set forth in the drawings and detailed description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The following is merely illustrative of the principles of the present disclosure, and it will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the present disclosure and are within its spirit and scope.

[0013] Furthermore, all examples and conditional language referenced herein are for educational purposes only to aid the reader in understanding the principles of the present disclosure and concepts contributed by the inventors to further the present technology, and are intended to be construed as not being limited to such specifically referenced examples and conditions.

[0014] Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, such equivalents are intended to include both currently known equivalents as well as equivalents developed in the future, that is, all elements developed that perform the same function, regardless of structure, are included.

[0015] Thus, for example, it will be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the disclosure.

[0016] Unless expressly specified herein, the figures making up the drawings are not drawn to scale.

[0017] It would be reiterated here that in recent years, distributed fiber optic sensing (DFOS) systems, including distributed vibration sensing (DVS) and distributed acoustic sensing (DAS), have gained widespread acceptance in many applications, including but not limited to infrastructure monitoring, intrusion detection, and earthquake detection.

[0018] Those skilled in the art will understand and appreciate that Rayleigh backscattering distributed optical fiber sensing can advantageously perform simultaneous detection of activity occurring at any location along the length of the sensing fiber. Such operation allows detection of sound as well as supersonic speeds depending on the fiber length. This property is advantageously employed to detect acoustic signals along the fiber length. In the prior art, several solutions for collecting acoustic signals have been reported, such as using linear fibers to directly detect acoustic signals or fiber coils to enhance the vibrations resulting from acoustic events. However, linear fibers have a very weak response to sound signals and fiber coils require special handling in fiber processing and layout, sacrificing sensing reach.

[0019] As shown and described in systems, methods, and structures according to aspects of the present disclosure, active circuitry is employed to amplify audio signals so that they can be reliably and reproducibly detected using DOFS. Exemplary active circuitry according to the present disclosure includes microphones that collect acoustic signals in the environment, and speakers or vibrating devices driven by amplifiers.

[0020] Advantageously, such a circuit can be clipped onto the optical sensing fiber with direct contact via a speaker or vibration device. In this embodiment, a microcontroller is employed to locally detect activity and control the circuit to conserve power by enabling the output speaker only when needed. The microcontroller can also transmit other information, such as battery status, to the interrogator via the vibration signal.

[0021] As will now be described, the present disclosure describes systems, methods, and structures that enhance DFOS / DAS operation by using a microphone, amplifier, and speaker to sense or amplify or transmit audio vibration signals to a sensing optical fiber. Mechanical vibrations generated by the speaker are transferred to the sensing optical fiber by direct contact with the optical fiber, resulting in a DFOS reproduction of the audio signal at the interrogator, allowing for clear reception. Advantageously, a microcontroller may be employed that turns on the speaker only when an audio signal is detected, thereby providing low power operation. Finally, such a microcontroller may be advantageously configured to report circuit status or other information to the DFOS interrogator for analysis and action.

[0022] As previously discussed, aspects of the present disclosure are directed to distributed fiber optic sensing systems, methods, and structures that advantageously recover acoustic signals simultaneously at any location along a sensing optical fiber, including an interrogator that actively launches a probe signal into an optically coupled sensing fiber and processes reflected and backscattered signals received from the fiber.

[0023] In one exemplary embodiment, Rayleigh backscattering can be employed for distributed acoustic sensing (DAS) using either direct or coherent detection. The signal from the fiber contains environmental information from every location it travels, especially vibration and acoustic information. The DAS interrogator processes the received signal to extract the vibration signal at each location on the fiber down to the pulse or code repetition rate, and uses the "sampled" acoustic signal for playback or further processing.

[0024] FIG. 1 is a schematic diagram of an exemplary arrangement according to an aspect of the present disclosure. As can be seen from this figure, such an exemplary arrangement includes a DAS interrogator, its optically coupled sensing fiber, and an active microphone. In an exemplary embodiment, the active microphone may include one or more microphones, an amplifier, and a speaker, depending on the needs of the application. In operation, the microphone receives an acoustic signal from the environment, which is amplified by the effect of the amplifier, and a representative signal is output to drive the speaker. In a preferred embodiment, the speaker or package device directly contacts the fiber optic cable and uses the amplified output acoustic signal to mechanically stimulate the attachment point to the optical fiber. When the fiber optic cable is stimulated in this way, the resulting mechanical / vibrational signal in the sensor's fiber optic cable is detected by the interrogator using an acoustic sensing method.

[0025] Active Microphone

[0026] To reduce power consumption, an active microphone may include a threshold circuit that drives the speaker only when the detected environmental signal (i.e., voice or other sound) is greater than a threshold. In one embodiment, the threshold circuit is controlled by a signal from a fixed amplifier output to drive a mechanical switch or transistor. When the signal is greater than the threshold, the mechanical switch or transistor turns on, thereby activating the speaker, which outputs an acoustic signal that is directed to the sensor fiber. In one exemplary embodiment, the speaker may be driven by a dynamic gain amplifier to extend the detected signal range. Figures 2(A), 2(B), and 2(C) show exemplary threshold circuits for enabling / disabling the speaker according to aspects of the present disclosure.

[0027] In one exemplary embodiment, the active microphone includes a microcontroller unit (MCU). The MCU controls the speaker on / off operation based on the environmental signal level. The MCU may operate in low power mode or hibernation mode while detecting an interrupt. The microphone output or amplified signal passes through a threshold logic, which generates an interrupt signal to wake up the MCU when the detected acoustic signal level is higher than a predefined threshold.

[0028] Turning now to FIG. 3(A) and FIG. 3(B), which respectively show a schematic diagram and a flow diagram illustrating the operation of an exemplary on / off switch controlled by an MCU according to an embodiment of the present disclosure, it can be seen that the MCU can configure the speaker driver circuitry to turn on the speaker as shown. Once the speaker is powered on, it will remain powered on for a period of time (T1) during which the MCU may enter a sleep / low power mode. After T1, an interrupt from the threshold circuitry is possible and the MCU will again enter a timed sleep mode (up to a maximum of T2). During this time, if the MCU detects an interrupt from the threshold circuitry, indicating that an environmental signal is still detectable, it will return to sleep mode for T1 with the speaker on, otherwise, since there is no detectable signal, it will enter initial sleep mode with the speaker off. It should be noted that in a dynamic gain amplifier, the gain can also be controlled by the MCU.

[0029] FIG. 4 is a schematic diagram illustrating an MCU using ADC data to control the gain of an amplifier according to an embodiment of the present disclosure. In one illustrative example, as shown in the figure, the MCU employs an ADC (analog-to-digital converter) to sample the input or amplified signal to determine the gain. With further reference to the flow diagram of FIG. 3(B), the MCU may obtain the ADC sampled value when waking up at the interruption of the threshold circuit or after a timed sleep T1, and the timed sleep periods T1 and T2 referred to in FIG. 3(B) can be replaced with multiple sleeps of reduced length to control the gain at finer time intervals.

[0030] Advantageously, as illustratively shown in FIG. 5, which is a schematic diagram illustrating an MCU that controls amplifier gain using a plurality of threshold circuits according to aspects of the present disclosure, the MCU may use a plurality of threshold circuits for amplifier gain control.

[0031] Assume that th-1 < th-2 < ··· < th-n. In the initial state, the MCU enables the interrupt from the threshold circuit th-1 and enters the sleep mode. The MCU awakened by the interrupt turns on the power of the speaker and sets the gain of the amplifier to the maximum. At the same time, the high-threshold interrupt of th-2 is enabled. When an interrupt from th-2 is detected, the MCU sets the corresponding gain and enables the next higher interrupt. This operation continues until no interrupt is detected or the highest threshold level is enabled.

[0032] At each gain level corresponding to the threshold circuit th-i, both interrupts from th-i and th-(i + 1) (when i < n) are enabled. If no interrupt from th-i is detected within the set time, the MCU enters the gain level th-(i - 1), and if i = 1, it turns off the speaker and enters the sleep state.

[0033] In one embodiment, at the gain level th-i, both interrupts from th-1 and th-(i + 1) are enabled, and there are timeout periods T1 and T2 (T1 < T2). During the T1 period, if th-(i + 1) is detected, the MCU enters the gain level th-(i + 1), and if there is no interrupt from th-i, it enters th-(i - 1). During the T2 period, if no interrupt from th-1 is detected, the MCU turns off the speaker and enters the sleep state. That is, during the time period T1, if the detection signal is higher than th-(i + 1), it goes to the th-(i + 1) gain level, if it is lower than th-i, it goes to the th-(i - 1) level, and during the time period T2, if it is lower than th-1, it transitions to the sleep mode.

[0034] Alternatively, the MCU can use a fixed time interval T1 and change the gain only once during each time interval. After powering up the speaker, the MCU enables all interrupts th-1 to th-n. At the end of each time interval, it checks which maximum threshold has been reached and adjusts the gain to that threshold level. If the detected signal remains lower than th-1 for T2 periods, it turns off the speaker and goes to sleep.

[0035] Microphone status report

[0036] In configurations employing an MCU for its control / monitoring and a speaker for generating / playing the acoustic signal, the active microphone can transmit embedded status reports to the interrogator. In one example scenario, the MCU transmits the active microphone's status information and processed environmental information to the interrogator. Operationally, the MCU modulates the information into an acoustic signal to drive the speaker and communicates it to the interrogator by stimulating the fiber with the effect of the speaker output. The MCU generated signal can be superimposed with the detected / played signal or can be used alone by temporarily stopping the playback path to allow only status reporting. The transmitted information can include the microphone's operating status, such as the battery status, and / or can include an "active" report to inform the interrogator that the device is in a normal operating state. Advantageously, the communicated information can also include gain settings or other operating parameters to inform / allow the interrogator to determine the actual acoustic signal level.

[0037] At this point, while we have illustrated the present disclosure with some specific examples, those skilled in the art will recognize that our teachings are not so limited. Accordingly, the present disclosure should be limited only by the scope of the claims appended hereto.

Claims

1. 1. A distributed fiber optic sensing (DFOS) / distributed acoustic sensing (DAS) system, comprising: a length of optical sensing fiber; a DFOS / DAS interrogator in optical communication with the optical sensing fiber; one or more active microphone nodes in physical contact with the optical sensing fiber; DFOS / DAS system, wherein the one or more active microphone nodes include a microphone that converts environmental sound into an electrical signal, an amplifier that amplifies the power of the electrical signal, and a speaker that converts the amplified signal into a corresponding sound, the one or more active microphone nodes configured to direct sound generated by the speaker to the optical sensing fiber.

2. 2. The DFOS / DAS system of claim 1, wherein the one or more active microphone nodes include a threshold circuit configured to provide power to a speaker of the active microphone node when an electrical signal of the environmental sound exceeds a predetermined threshold.

3. 10. The DFOS / DAS system of claim 1, further comprising a microcontroller (MCU) configured to power a speaker of the active microphone node when an electrical signal of an environmental sound exceeds a predetermined threshold.

4. 4. The DFOS / DAS system of claim 3, wherein the MCU includes an analog-to-digital converter configured to determine an amplitude of the electrical signal of the ambient sound and adjust a gain of the amplifier in response to the determined amplitude.

5. 5. The DFOS / DAS system of claim 4, wherein the one or more active microphone nodes include one or more threshold circuits configured to provide an interrupt signal to the MCU when an electrical signal of the environmental sound meets a predetermined threshold, the MCU configured to adjust the gain of the amplifier upon receiving the interrupt.

6. The DFOS / DAS system of claim 5 , wherein the MCU is configured to remove power from the speaker when an electrical signal of an environmental sound is below a predetermined threshold for a predetermined period of time.

7. 4. The DFOS / DAS system of claim 3, wherein the MCU is configured to encode node status information into an acoustic signal by effect of the speaker and drive the speaker to relay the status information to the DFOS / DAS interrogator.

8. The DFOS / DAS system of claim 7 , wherein the status information includes an amplifier gain level.

9. The DFOS / DAS system of claim 7 , wherein the status information includes a battery status.

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