DETECTION OF WORK AREA INVASION USING BRAGG NETWORKS

Abstract

A work area intrusion detection device, the device comprising: - an optical fiber cable (1) comprising a plurality of Bragg gratings (2) distributed along its length, the optical fiber cable comprising a first end (11) and a second end (12); - a laser light source (3) located at the first end (11) of the optical fiber cable (1), configured to emit laser light within the cable (1); - a laser receiver (4) located at the second end (12) of the optical fiber cable (1), the laser receiver (4) being configured to receive laser light, analyze the frequency of the received laser light and emit detection data; - a control unit (5); and - a digital data transmitter (6), connected to the laser receiver to receive the detection data and connected to the control unit to send digital data containing the detection data information.

Description

DETECTION OF WORK AREA INVASION USING BRAGG NETWORKS FIELD OF INVENTION The present invention falls within the technical field of road safety systems, more specifically within the scope of devices intended for the protection of workers and work elements in road conservation and maintenance operations. BACKGROUND OF THE INVENTION Safety in road work zones represents one of the most notable challenges in road infrastructure management, since the invasion of these work zones by circulating vehicles is a direct cause of serious collisions with workers and construction equipment located in these work zones. Traditionally, security has relied on passive measures such as signage and physical barriers. However, the need to mitigate risks more effectively has driven the development of intelligent transportation systems. These systems transform work areas into "smart zones" using technologies such as radar and video sensors for real-time intrusion detection. The most significant advance to date involves Intelligent Transportation Systems (ITS) or Intelligent Transportation Cooperative Systems (ITS-C). These systems establish a wireless communication framework that enables direct interaction between the work zone infrastructure, vehicles, and workers' portable devices. The central objective is to generate immediate alerts that warn workers of an imminent intrusion into their work zone and, furthermore, inform drivers about the zone's hazards and boundaries, thus preventing the intrusion before it occurs. Despite the numerous advantages that these technologies possess, there is no effective, economical and easily deployable system that delimits the security zone and at the same time detects, in real time, the invasion of this zone, allowing identification of the exact point where the invasion occurs and activation of immediate alert protocols. BRIEF DESCRIPTION OF THE INVENTION The present invention solves the previous limitations of the prior art, by means of a detection device according to claim 1. In a first inventive aspect, the present invention relates to a device for detecting invasion of a work area, the device comprising: an optical fiber cable comprising a plurality of Bragg gratings distributed along its length, the optical fiber cable comprising a first end and a second end; a laser light source located at the first end of the fiber optic cable, configured to emit laser light inside the cable; a laser receiver located at the second end of the fiber optic cable, the laser receiver being configured to receive laser light and analyze the frequency of the laser light received; a control unit; and a digital data transmitter, connected to the laser receiver to receive detection data and connected to the control unit to send digital data containing the detection data information. This device is designed to detect when an object passes over it to enter a work area where such an object is prohibited. As the object passes over the fiber optic cable, it deforms the cable, causing the light emitted by the laser source to arrive distorted at the other end. The laser receiver is positioned to receive the laser light and generate detection data. This detection data can be as simple as the wavelength of the received laser light. Since the signal is distorted by the deformation of the Bragg grating in the section the object has passed over, simply recording the wavelength is enough to identify the deformed Bragg grating and, therefore, the location on the fiber optic cable where the intrusion occurred. In the context of the present invention, the term Bragg grating refers to a microstructure that is typically a few millimeters long and can be inscribed in the core of a telecommunications fiber, in this case an optical fiber cable. The digital data transmitter is simply an electronic circuit comprising an input, through which the detection data from the laser receiver is received, and an output, through which this data, processed digitally within the electronic circuit, is sent to the control unit in a format readable by that unit. This digital data transmitter can be integrated within the laser receiver, as its sole purpose is to send the detection data in a suitable format to the control unit. In specific embodiments, the control unit comprises a microprocessor responsible for receiving data from the digital data transmitter and converting that data into the precise location of the distorted Bragg grating. To achieve this, it includes a database that allows it to relate, for given laser light wavelength input data, which distorted Bragg grating is responsible for the variation relative to the original wavelength. Once the Bragg grating responsible for the variation is identified, its location is immediately pinpointed. In this way, the device not only allows real-time detection of the entry / exit of any element to the work area, but also provides specific information on the kilometer point where said element has entered or exited. In particular implementations, Bragg gratings are arranged uniformly along the fiber optic cable. This facilitates the manufacturing process of the fiber optic cable and also achieves high spectral accuracy. In particular implementations, the laser light source is an ultraviolet frequency laser light source. The use of ultraviolet frequency in the laser light source is not an essential requirement, but it can provide technical advantages in certain configurations: it improves sensitivity in reading small variations of deformation in the Bragg grating, reduces optical noise, and can offer greater spectral stability in specific fibers. In particular embodiments, the device further comprises a photovoltaic cell and a battery, wherein the battery is connected to the photovoltaic cell to store the energy produced by said photovoltaic cell and is configured to power the device. In this way, the device can operate autonomously, without needing to be connected to a general electrical network. In specific implementations, the laser receiver includes a global positioning system. This makes it possible to pinpoint the exact location of the device on the road. In specific embodiments, the digital data transmitter comprises a wireless transmission antenna. In specific embodiments, the wireless transmission antenna is configured to transmit data according to the Zigbee, LoRaWAN, LPWA, 4G, or 5G protocol. In the present invention, the term "Zigbee" refers to a set of high-level wireless communication protocols for use with low-power digital broadcasting. The term "LoRaWAN" ("Long Range Wide Area Network") refers to a low-power, bidirectional wireless communication technology for transmitting low data volumes over long distances. The term "LPWA" ("Low-Power Wide-Area") refers to a group of technologies whose main objective is to enable long-distance wireless communication while maintaining extremely low power consumption. Finally, the terms "4G" and "5G" refer to fourth- and fifth-generation mobile communication standards, respectively, that enable data transmission via radio waves. In this way, the digital data transmitter can be in a remote position with respect to the control unit, or the control unit can even be hosted on a cloud server. In specific embodiments, the device additionally comprises: - a radar signal transmitter module focused within the work area; - a radar signal receiver module; - a digital processing unit connected to the radar signal receiver module to receive the data produced by the radar signal receiver module; and - a display and control interface. When a radar module is added to the device of the present invention, it acquires the ability to track the offending object within the work area. Once the exact point where the infraction occurred has been identified, thanks to the laser receiver signal, the radar signal transmitter module can focus on that point to track the object within the work area, since the fiber optic cable has no element capable of providing this information. In some embodiments, the radar signal transmitter module comprises a frequency-modulated continuous-wave radar emitter. In other embodiments, the radar signal transmitter module comprises a pulse radar emitter. In this way, the most suitable type of radar system can be selected based on the desired application. In particular embodiments, the radar module comprises a circuit configured to emit electromagnetic signals in millimeter bands selected between 24-77 GHz. In particular embodiments, the radar module mentioned above additionally comprises a global positioning system. In particular embodiments, the device additionally comprises a lidar emitter focused within the work area. The lidar emitter is capable of providing more accurate information regarding the shape and position of the offending object. In particular embodiments, the present invention relates to a system comprising - a plurality of optical fiber cables, each cable comprising a plurality of Bragg gratings distributed along its length, each optical fiber cable comprising a first end and a second end; - a laser light source located at the first end of each fiber optic cable, configured to emit laser light inside the cable; - a laser receiver located at the second end of each fiber optic cable, the laser receiver being configured to receive laser light and analyze the frequency of the laser light received; where the digital data emitter is connected to each laser receiver to receive detection data. Thus, the present invention is not limited by the area that a single device can cover, but extended areas can be covered using a system comprising a plurality of cables, each with its transmitter and receiver, operating in a synchronized manner. In other particular embodiments, the invention relates to a system comprising: - a device according to the first inventive aspect; and - a plurality of portable personal protective equipment for workers; wherein the device further comprises a communicator for communicating with the portable personal protective equipment for workers. Thus, the device, which is capable of detecting the intrusion of an object into a work area, would also be able to warn those workers who are wearing connected personal protective equipment about the intrusion of said object, preventing accidents and improving their safety. All terms and embodiments described anywhere in this document are equally applicable to all aspects of the invention. It should be noted that, as used in the description and claims, the singular forms "a," "an," and "the" include their plurals unless the context clearly indicates otherwise. Similarly, the term "comprises" or "comprising," as used herein, also describes "consists of" or "consisting of" in accordance with generally accepted patent practice. BRIEF DESCRIPTION OF THE FIGURES The following is a brief description of each of the figures used to complement the description of the invention that follows, for illustrative and non-limiting purposes: Figure 1 shows a particular example of a work area invasion detection device according to the invention. Figure 2 shows an example of the operation of this device when it is installed on a road to delimit a work zone whose access is prohibited. Numerical references for the figures In order to aid a better understanding of the technical characteristics of the invention, the aforementioned figures are accompanied by a series of numerical references where, for illustrative and non-limiting purposes, the following is represented: DETAILED DESCRIPTION OF THE INVENTION The detailed description of the present invention that follows relates to specific embodiments that can be implemented. These embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention. It should be understood that various embodiments of the present invention are different from one another, but are not necessarily mutually exclusive. Accordingly, the detailed description that follows is not intended to be taken in a restrictive sense, and the scope of the present invention, if properly described, is limited only by the appended claims, in addition to all scopes equivalent to those claimed by the appended claims. Figure 1 shows a particular example of a work area invasion detection device according to the invention. This device comprises the following elements: an optical fiber cable 1 comprising a first end 11 and a second end 12; a laser light source 3 located at the first end 11 of the optical fiber cable 1, configured to emit laser light inside the cable 1; a laser receiver 4 located at the second end 12 of the optical fiber cable 1, the laser receiver 4 being configured to receive laser light and analyze the frequency of the laser light received; a control unit 5; and a digital data transmitter 6, connected to the laser receiver 4 to receive detection data and connected to the control unit 5 to send digital data containing the detection data information a photovoltaic cell 7 and a battery 8, wherein the battery 8 is connected to the photovoltaic cell 7 to store the energy produced by said photovoltaic cell 7 and to power the electrical needs of the device. In this invention, a single-mode optical fiber cable 1 is used, equipped with multiple Bragg gratings 2 distributed uniformly along its length. Each Bragg grating 2 reflects a specific range of light wavelengths. Therefore, when an object enters or leaves the work area and steps on the optical fiber cable, a local deformation is generated, producing a change in the wavelength reflected by the specific Bragg grating that has been deformed. This change in wavelength is perceived by the laser receiver as an intrusion at the exact point where the change occurred. Advantageously, fiber optic cable can be supplied on portable reels, which facilitates its transport and deployment. Furthermore, fiber optic cable is resistant to harsh weather conditions such as rain, snow, extreme temperatures, and dust. Figure 2 shows an example of the operation of this device. As can be seen in the figure, this device is installed on a road to delimit a work zone whose access is prohibited. However, if an object (such as a vehicle) enters the work area, passing over the fiber optic cable 1 distorts these Bragg gratings 2. As a result, the laser receiver 4 will receive a signal with a different wavelength, caused by this distortion. Since each Bragg grating is different, its distortion will cause a different change in wavelength, making it easy to deduce which Bragg grating has been distorted and thus identify the exact location of the intrusion. The information obtained is sent, using the digital data transmitter 6, to the control unit 5, configured to perform operations, preferably sending immediate alerts, activating variable message signs on the road, communicating with traffic systems, and logging events. In this case, the digital data transmitter 6 comprises a wireless transmission antenna 9 for transmitting data to the control unit 5. This antenna 9 is configured to transmit data according to the Zigbee, LoRaWAN, LPWA, 4G, or 5G protocol. In this way, control unit 5 can identify the exact kilometer point where this infraction took place. As can be seen in this figure, the device additionally comprises a series of elements designed to improve the tracking of the offending object: - a radar signal transmitter module 21 focused within the work area; - a radar signal receiver module 22; - a digital processing unit 23 connected to the radar signal receiver module to receive the data produced by the radar signal receiver module; and a display and control interface 24. The purpose of these elements is to track the object once it has crossed the unauthorized area. The primary function of the transmitter module is to generate a modulated carrier signal and transmit it via directional antennas or phased arrays. The reflected signals are captured by the receiver module, which converts them into digital data using analog-to-digital converters. Subsequently, the digital processing unit applies fast Fourier transforms, filtering, and spectral estimation techniques to extract the characteristics of the echoes. The visualization and control interface then displays the detected objects on a map or road model, facilitating real-time analysis and historical event storage. The processing of the data obtained by the radar system comprises the following stages: - Signal preprocessing: this stage consists of noise removal and interference compensation. - Target detection: this stage consists of identifying energy peaks in the frequency spectrum. - Tracking: This stage involves applying algorithms such as Kalman Filter or Multiple Hypothesis Tracking (MHT) to estimate trajectories. - Object classification: this stage consists of using machine learning techniques or radar signature-based models to distinguish between vehicles, pedestrians, or static obstacles. - Sensor fusion: In advanced systems, data from cameras, lidar technology, or ultrasonic sensors are integrated to improve the reliability of detection. In specific implementations, the radar signal transmitter module comprises a frequency-modulated continuous-wave radar emitter. This type of technology allows for the measurement of distance and speed by analyzing the frequency variations of the reflected signal. In other specific embodiments, the radar signal transmitter module comprises a pulse radar emitter. This is a detection system that emits pulses of electromagnetic energy and measures the time elapsed between the transmission of each pulse and the reception of the echo reflected by an object. Since the control unit can identify the kilometer marker where the intrusion occurred, the radar signal transmitter module 21 can be activated to emit radar signals in that area, allowing the object to be tracked and identified. In some cases, a camera system can also be used to provide live images of the object and its movement. Occasionally, there may be workers in the work area not authorized for vehicles, and these workers may be wearing portable personal protective equipment. Sometimes, the device of the present invention also includes a communicator for communicating with workers' personal protective equipment. In this way, when it is detected that the object has entered the work area and is approaching the workers, they can receive an alert to evacuate. In other particular embodiments, the device additionally comprises a lidar emitter, either as an additional system or instead of the radar module described in Figure 2. For the integration of the radar emitter or, alternatively, the lidar emitter with the device of claim 1 of the present invention, the control unit of said device is used. In this embodiment, both the radar sensor and the lidar sensor are connected to the same control unit of the device and use the information generated by the optical fiber—position, time, and intensity of the intrusion—to guide their detection and track the intruder. The control unit manages the data from either the radar or the lidar interchangeably and applies the same logic for interpretation, alerting, and recording. Advantageously, information about the exact location and time of the intrusion and the intensity of the impact, obtained by the change in wavelength when at least one of the Bragg gratings contained in the fiber optic cable is deformed, is sent in real time to the control unit, which applies the following defined logic: - Depending on the location of the work area, the area of ​​interest covered by the radar / lidar is obtained. - The working area on the radar is defined using cones or other physical elements on the road. - From the geographical position obtained by the detection device when an invasion occurs, the exact kilometer point where the aforementioned invasion has occurred is obtained. - With the information collected, immediate alerts are wirelessly sent from the control unit to operators via mobile application or personal protective equipment. - Activation of variable message signs to warn drivers of the detected intrusion. - Communication to traffic systems, for example, DGT 3.0. - Event logging for later analysis. In particular embodiments, the present invention relates to a system comprising a plurality of devices such as those mentioned above. In systems comprising multiple fiber optic cables, each cable incorporates its own laser light source and corresponding receiver to enable independent detection of deformations in each segment. However, all signals generated by these cables can be processed by a single control unit, which acts as the central element for interpreting and managing the system. Thus, the present invention is not limited by the area that a single device can cover, but extended areas can be covered using a system comprising a plurality of devices operating in a synchronized manner.

Claims

1. A work area intrusion detection device, the device comprising: - an optical fiber cable (1) comprising a plurality of Bragg gratings (2) distributed along its length, the optical fiber cable comprising a first end (11) and a second end (12); - a laser light source (3) located at the first end (11) of the optical fiber cable (1), configured to emit laser light within the cable (1); - a laser receiver (4) located at the second end (12) of the optical fiber cable (1), the laser receiver (4) being configured to receive laser light, analyze the frequency of the received laser light, and emit detection data; - a control unit (5); and - a digital data transmitter (6), connected to the laser receiver to receive the detection data and connected to the control unit to send digital data containing the detection data information. 2.A device according to any of the preceding claims, wherein the Bragg gratings (2) are arranged uniformly along the optical fiber cable (1).

3. A device according to any of the preceding claims, wherein the laser light source (3) is an ultraviolet frequency laser light source.

4. A device according to any of the preceding claims further comprising a photovoltaic cell (7) and a battery (8), wherein the battery (8) is connected to the photovoltaic cell (7) to store the energy produced by said photovoltaic cell (7) and is configured to power the device.

5. A device according to any of the preceding claims, wherein the laser receiver (4) comprises a global positioning system.

6. A device according to any of the preceding claims, wherein the digital data transmitter (6) comprises a wireless transmitting antenna (9). 7.Device according to claim 6, wherein the wireless transmitting antenna (9) is configured to transmit data according to the Zigbee, LoRaWAN, LPWA, 4G, or 5G protocol.

8. Device according to any of the preceding claims, further comprising: - a radar signal transmitter module (21) focused within the working area; - a radar signal receiver module (22); - a digital processing unit (23) connected to the radar signal receiver module for receiving the data produced by the radar signal receiver module; and - a display and control interface (24).

9. Device according to claim 8, wherein the radar signal transmitter module (21) comprises a frequency-modulated continuous-wave radar emitter.

10. Device according to claim 8, wherein the radar signal transmitter module (22) comprises a pulse radar emitter. 11.A device according to claims 8-10, wherein the radar signal transmitter module comprises a circuit configured to emit electromagnetic signals in millimeter wave bands selected between 24-77 GHz.

12. A device according to claim 8, wherein the radar module further comprises a global positioning system.

13. A device according to any of the preceding claims, further comprising a lidar emitter configured to be focused within the work area. 14.A device according to any of the preceding claims, comprising: - a plurality of optical fiber cables (1), each cable comprising a plurality of Bragg gratings (2) distributed along its length, each optical fiber cable comprising a first end (11) and a second end (12); - a laser light source (3) located at the first end (11) of each optical fiber cable (1), configured to emit laser light within the cable (1); - a laser receiver (4) located at the second end (12) of each optical fiber cable (1), the laser receiver (4) being configured to receive laser light and analyze the frequency of the received laser light; wherein the digital data emitter (6) is connected to each laser receiver to receive detection data. 15.System comprising: - a device according to any of the preceding claims; and - a plurality of portable personal protective equipment for workers; wherein the device further comprises a communicator for communicating with the portable personal protective equipment for workers.