SYSTEM AND METHOD FOR DETECTION AND LOCATION OF EVENTS BASED ON OPTICAL INTERFEROMETRY WITH DOUBLE DELAY COIL

Description

1 / 11 SYSTEM AND METHOD FOR DETECTION AND LOCATION OF EVENTS BASED ON OPTICAL INTERFEROMETRY WITH DOUBLE DELAY COIL FIELD OF THE INVENTION

[001] This patent application relates to a system and process for the precise detection and location of events along optical paths using two distinct interferometers and a double delay coil. The field of application is focused on optical monitoring systems, more particularly, on applications in telecommunications networks and high-precision sensing over long distances. The present invention aims to provide greater precision in the location of events along optical paths of up to 20 km, promoting cost reduction with advanced electronics by using optical delay techniques and simultaneous signal capture. In addition, the present invention ensures reliability, operational efficiency and the ability to operate in environments with high-resolution requirements. BACKGROUND OF THE INVENTION

[002] Namely, distributed interferometric sensing systems are widely employed in a variety of applications, including perimeter security, pipeline monitoring, and structural assessment. Such systems use, in some cases, interferometric technology to detect minute changes in the phase of light propagating through an optical fiber, these changes resulting from vibrations, temperature variations, or mechanical deformations along the fiber's path.

[003] Currently, the most advanced systems use external cavity lasers, characterized by a narrow linewidth and high coherence, allowing for high precision in detection. This technology enables the identification of events over long distances with high sensitivity. However, external cavity lasers have a high cost, which directly impacts the economic viability and accessibility of distributed interferometric sensing systems for various applications. Petition 870240110855, dated 12 / 27 / 2024, page 8 / 48 2 / 11

[004] Although alternative solutions have been proposed to reduce costs, such as the use of LEDs or superluminescent diodes in certain configurations, such approaches often result in losses in the sensitivity and accuracy of the systems. These effects are particularly critical in scenarios that require the detection of small disturbances along the optical fiber. PROBLEM TO BE SOLVED

[005] In view of the above, current distributed interferometric sensing systems have several limitations that hinder their widespread adoption, mainly due to high costs and implementation complexity. Below are the main problems overcome by the invention:

[006] Most interferometric sensing systems use external cavity lasers, which offer high coherence and precision, but have a high cost, making these systems inaccessible for many applications. The present invention overcomes this limitation by using a low-cost DFB (Distributed Feedback Laser), compensating for its limitations with an optimized optical configuration, including a double delay coil and a high-precision data acquisition system;

[007] Current systems that use technologies such as Rayleigh or Brillouin scattering require sophisticated equipment and frequent calibration processes to maintain measurement accuracy. The invention simplifies the system by eliminating the need for complex calibrations, thanks to the use of a simple optical configuration, based on the delay coil, which allows precise control of the phase shift in the signals.

[008] Systems that rely on expensive lasers and highly complex equipment have high maintenance costs. In addition, downtime due to maintenance needs can compromise critical operations. The invention significantly reduces maintenance costs by adopting simpler and more affordable components, such as the DFB laser, which requires fewer operational adjustments.

[009] Due to the high cost and complexity of current systems, their scalability for larger applications is limited. The present invention offers a more suitable solution. Petition 870240110855, dated 12 / 27 / 2024, page 9 / 48 3 / 11 is accessible and scalable, allowing its application in large distributed monitoring projects with reduced cost and without compromising accuracy. CURRENT STATE OF THE ART

[010] The current state of the art document US11598627B2, published on 03 / 07 / 2023, which describes a distributed interferometry system using high-quality lasers, is known. Although the accuracy of these systems is satisfactory, the high cost of optical components, such as external cavity lasers, is still a significant limitation for their large-scale implementation.

[011] Another example of distributed sensing systems uses technologies such as Rayleigh scattering and Brillouin scattering, which also require lasers with high coherence and sophisticated data acquisition equipment. These systems are used for infrastructure and security monitoring, but face challenges related to the cost and complexity of calibration and maintenance. OBJECTIVES OF THE INVENTION

[012] The objective of the present invention is to use a low-cost DFB laser to replace expensive external cavity lasers, while maintaining the coherence and precision required for distributed interferometric sensing systems.

[013] The objective of the present invention is to reduce maintenance costs by adopting simpler and more affordable components.

[014] The objective of the present invention is to ensure sensitivity and accuracy in detecting events over long distances, even when using more economical components.

[015] The objective of the present invention is to compensate for the limitations of low-cost components by means of an optimized optical configuration, including a dual delay coil and a high-precision data acquisition system.

[016] The objective of the present invention is to eliminate the need for complex calibration processes, using a simplified optical configuration based on the delay coil, which allows precise control of the phase shift in the signals.

[017] The objective of the present invention is to provide an innovative and low-cost solution for distributed interferometric sensing systems, increasing their Petition 870240110855, dated 12 / 27 / 2024, page 10 / 48 4 / 11 Accessibility for various applications, such as perimeter security, pipeline monitoring, and structural assessment. BRIEF DESCRIPTION OF THE INVENTION

[018] The present invention relates to an optical configuration for distributed interferometric sensing, composed of three main elements: a double delay coil, a high-performance data acquisition system, and a low-cost DFB laser. The invention was designed to ensure high precision in the detection and monitoring of events along optical fibers, while maintaining reduced costs. The double delay coil introduces a controlled phase shift in the signals traveling through the optical fibers. Both fibers of the coil have the same dimensions, ensuring that the optical paths are equivalent, which allows precise phase control and, consequently, more accurate detection of variations in optical signals caused by external events, such as vibrations or deformations.The DFB laser has its limitations, such as its wider linewidth, which are compensated for by its optimized optical architecture, which includes the dual delay coil and data acquisition system, thus allowing the invention to maintain accuracy comparable to conventional systems, but at a significantly lower cost. The high-performance data acquisition system is responsible for capturing subtle variations in optical signals with a sampling rate of 10 MS / s, which ensures the accuracy needed to identify rapid and small changes in the properties of light traveling through the fibers.

[019] The present system is capable of processing data at high speed, which facilitates the identification of relevant events in real time. The present optical configuration is designed for applications requiring continuous and precise monitoring, such as vibration detection, intrusions, or structural changes over long distances.The proposed solution offers a cost-effective alternative to traditional systems, while maintaining sensitivity and the ability to detect events in real time. ADVANTAGES OF THE INVENTION

[020] The present invention has the following advantages: Petition 870240110855, dated 12 / 27 / 2024, page 11 / 48 5 / 11 ^ The configuration compensates for the coherence limitations and wider linewidth of the DFB laser, while maintaining measurement accuracy through combination with the dual delay coil and data acquisition system; ^ Replaces expensive external cavity lasers with a low-cost DFB laser, without compromising accuracy and sensitivity; ^ It makes the system accessible for a wider range of applications, allowing for its large-scale implementation without the high costs associated with conventional systems; ^ It includes a dual delay coil and a high-sampling-rate data acquisition system, is relatively simple to implement and operate, eliminating the need for complex calibrations and operational adjustments required by other systems, reducing installation time and operating costs; ^ It maintains high precision in event detection thanks to the combination of the double delay coil, which ensures equivalent optical paths and precise control of signal phase shift, and the high-speed data acquisition system, which captures rapid and subtle variations; ^ It offers a more scalable solution than conventional systems, with reduced costs; ^ It has a simple system that allows it to be used in large-scale projects, such as long-distance monitoring, without proportionally increasing the cost or complexity; By adopting simpler and more affordable components, such as the DFB laser, the invention requires less maintenance, resulting in lower operating costs and less downtime compared to systems that use external cavity lasers and other more complex components. Integration with an artificial intelligence module for signal analysis and diagnosis. ^ An automatic calibration method that minimizes the need for manual intervention by adjusting the system based on environmental or operational changes. Petition 870240110855, dated 12 / 27 / 2024, page 12 / 48 6 / 11 ^ Adaptive operation capability, automatically adjusting the sampling rate based on the system's resolution needs. DESCRIPTION OF THE FIGURES

[021] The following figure is presented to better explain the patent application in an illustrative and non-limiting way:

[022] Fig. 1: Shows the configuration of the optical system, including the optical splitter, the two distinct interferometers and the double delay coil for 1530 nm and 1550 nm optical signals. DETAILED DESCRIPTION OF THE INVENTION

[023] The SYSTEM AND METHOD FOR DETECTION AND LOCATION OF EVENTS BASED ON OPTICAL INTERFEROMETRY WITH DOUBLE DELAY COIL, the subject of the present invention, relates to a system and process that allow the integration of two optical interferometers configured to operate on distinct paths with signals of wavelengths of 1530 nm and 1550 nm. The first interferometer uses Faraday mirrors to reflect and stabilize the polarization of the signal, allowing for highly accurate round-trip paths. The second interferometer is equipped with an add-drop type device, which allows the direct passage of the signal without reflection. To introduce an optical delay in the 1550 nm signal, the present invention incorporates a double delay coil composed of identical optical fibers, ensuring a length tolerance of less than 10 cm, preferably 1 to 2 cm.The system includes optical detectors associated with each interferometer to simultaneously capture the ascending and descending phases of each interferometer. In addition, a data capture board with four independent channels, configured to operate at rates of up to 10 MSPS per channel, ensures the temporal precision necessary for the analysis and correlation of the signal phases. This technical setup allows for the accurate determination of event locations along optical paths of up to 20 km, combining high precision, operational efficiency, and cost reduction.

[024] In more detail, the optical assembly consists of an optical splitter and two distinct interferometers, configured to generate a difference between the optical signals in order to determine the location of events or measurements. This difference is Petition 870240110855, dated 12 / 27 / 2024, page 13 / 48 7 / 11 obtained through a variable phase shift between the signals. Each interferometer is designed for different optical paths. One of the interferometers operates with an optical signal of wavelength 1530 nm, which is directed along a path that includes Faraday mirrors, responsible for reflecting the signal and stabilizing its polarization. The 1530 nm wavelength optical signal travels along the path to the mirrors, where it is reflected, returning along the same path. This movement characterizes the round-trip dynamics of the signal in the 1530 nm interferometer. The second interferometer operates with an optical signal of wavelength 1550 nm, which follows an alternative path.Along this path, an add-drop device is used to facilitate the separation and manipulation of signals with different wavelengths (1530 nm and 1550 nm) without the need for more complex optical components, such as wavelength division multiplexers (WDM), allowing the optical signal to pass directly through the system without reflection. Additionally, an optical delay is introduced in the 1550 nm signal path, using an optical fiber configured for a length of at least two to three kilometers.

[025] The 1550 nm wavelength optical signal is reflected by a specific mirror, configured to return the signal to the system. The location of events along the optical path is determined based on the distance traveled by the signal. In particular, where the event occurs, a time delay is introduced that varies according to the event's position on the path. For example, when the event occurs at an intermediate position on the optical path, the signal travels the entire path to the event's position, returning to the system. Similarly, the other interferometer, associated with the 1530 nm signal, travels its respective round trip path. In the case of an event located at the reference position, considered as position zero, the delay introduced in the 1550 nm signal path is proportionally smaller, resulting in a minimal difference between the phases of the signals from the two interferometers.

[026] This minimum delay is determined by the length of the additional path introduced by the fiber delay, configured to be at least two to three kilometers. In situations where the event occurs at more distant positions in the optical path, such as in a. Petition 870240110855, dated 12 / 27 / 2024, page 14 / 48 8 / 11 total path of up to 20 kilometers, the phase difference between the signals from the two interferometers directly reflects the distance proportional to the event in the system.

[027] The optical system described is configured to operate on paths with a total length of up to 20 kilometers, plus the delay introduced by a fiber delay of approximately three kilometers. Event identification in the system is based on the modulation of optical signals, which is performed by analyzing the phase relationship between the signals processed in the two interferometers. Each interferometer is designed to operate with two distinct phases, ascending and descending. The configuration includes two optical fibers, so that, upon returning along the beat path, the generated signals are directed to two detectors. Each detector is responsible for the signal from each set of interferometers, for phase determination, ensuring the separation of phase information into two distinct signals, optimized for this operation. To register the phase difference between the signals, the system faces the challenge posed by the high speed of light.

[028] Two solutions are considered to overcome this challenge: (i) the use of an extremely fast capture system, with speeds in the gigahertz range, capable of recording the time differences between the paths; or (ii) the creation of a significant delay in the signals, implemented by means of optical fibers configured for this purpose.

[029] The preferred approach is the creation of optical delay, implemented through a dual delay coil configuration composed of two fibers. This configuration ensures the accuracy of the phase difference without overloading the capture and electronic processing systems. Implementing optical delay requires only optical fiber and manufacturing time, while the alternative of increasing the capture speed would imply significantly higher costs in electronics and processing, due to the increased amount of signals to be processed.

[030] The component described is of fundamental importance to the system and has a unique configuration not found in existing technical literature. The internally developed solution includes a dual delay coil configured in conjunction with an optical channel. This configuration allows the use of a rate of Petition 870240110855, dated 12 / 27 / 2024, page 15 / 48 9 / 11 Reduced capture, resulting in a lower-cost electronic system without compromising the accurate identification of optical signals. The invention comprises a data acquisition system consisting of a data capture board designed to process the signals generated by the system. The data capture rate directly influences the temporal resolution of the system: the higher the sampling rate and the number of samples collected in a given time interval, the greater the temporal resolution obtained. For example, to achieve a spatial resolution of 100 meters, the sampling rate must be sufficient to maintain this granularity as the maximum resolution limit. The algorithm used in the system processes the modulated signals, correlating their phases to determine the time between events. These correlations are used to calculate the time with high precision.Furthermore, the system faces a technical requirement not documented in the literature: the ideal for system operation is simultaneous sampling of signals. This means that, when capturing position data, all four signals (ascending and descending from both interferometers) must be sampled at the same instant, without introducing any delay between them. This approach ensures greater accuracy in time calculations and improves the reliability of the measurements performed by the system.

[031] It has been identified that, when employing multiplexing for signal capture, even in high-speed systems, it becomes impossible to guarantee that the sampled points correspond exactly to the same time instant. To solve this limitation, a data capture board was developed, specifically designed to perform simultaneous readings on the four channels of the system. These channels correspond to the two phases of the first interferometer and the two phases of the second interferometer. With this solution, it is possible to significantly minimize the margin of error in the readings, ensuring greater precision and reliability. The solution now claimed allows the use of simpler electronics, while maximizing the performance of the developed system. The data capture board has two main operating configurations: Petition 870240110855, dated 12 / 27 / 2024, page 16 / 48 10 / 11 (i) a capture rate of 40 mega samples per second (MSPS) on a single channel; or (ii) a capture rate of up to 10 MSPS on each of the four channels simultaneously.

[032] The simultaneity feature ensures that data from all channels is captured at the same instant, eliminating the deviations associated with multiplexing. This capability guarantees more accurate and consistent readings, fundamental to the system's operation. Currently, the system operates with a capture rate of 4 MSPS on each of the four channels simultaneously, but the configuration allows this rate to be increased to up to 10 MSPS per channel, according to specific resolution and performance needs.

[033] The system operation is subject to limitations related to the transmission speed of the optical network. However, the developed components present innovative solutions that simplify the system electronics and optimize its efficiency.

[034] Among these innovations, the development of a double optical fiber delay coil specifically designed to ensure high precision and uniformity between the fibers used stands out. Although the literature acknowledges the existence of delays in fiber optic systems, there is no detailed technical description of the methods to ensure that two fibers are exactly identical in length and performance. This is particularly critical in systems that rely on the DFB laser linewidth to maintain accuracy.The solution presented in the present invention resolves this gap by ensuring that the fibers used in the system have length differences of less than 10 centimeters, preferably on the order of 1 to 2 centimeters.

[035] The present invention has two main advantages: (i) it allows the use of DFB lasers with a wider linewidth, enabling the use of more economical DFB lasers; and (ii) it reduces the costs associated with the system electronics, since the uniformity of the fibers eliminates the need for complex electronic compensation to handle discrepancies between the optical paths. Petition 870240110855, dated 12 / 27 / 2024, page 17 / 48 11 / 11

[036] The constructiveness of the dual delay coil represents a significant innovation by minimizing costs without compromising system accuracy. If the length differences between the fibers were greater, it would be necessary to use DFB lasers with narrow line width, which would substantially increase the cost of the system.

[037] The capture card developed for the system was designed to simultaneously capture the signals from all four channels at the same instant, ensuring the absence of drift or differences between readings. This configuration ensures that the maximum resolution offered by the capture rate is achieved, since the signals from all four channels are recorded in a synchronized and identical manner. The development of the data capture card represents an efficient and economical solution compared to conventional high-frequency capture systems, such as gigahertz cards.

[038] The solution described enabled the use of a capture rate that meets the system's resolution requirements without the need for more complex and expensive electronics. Furthermore, the system was designed to use DFB lasers with a wider linewidth, such as 20 MHz or 10 MHz lasers, which are significantly cheaper than 3 kHz lasers. This combination of techniques—including the optimized construction of the data capture board, the use of more affordable DFB lasers, and the implementation of identical fibers in the reels—allowed for a substantial reduction in product cost while maintaining the high standards of resolution and accuracy required by the system. Therefore, the solutions described in this invention not only meet the technical requirements for performance and reliability but also fulfill the cost reduction requirement, essential for the commercial viability of the product. Petition 870240110855, dated 12 / 27 / 2024, page 18 / 48

Claims

1 / 2 CLAIMS 1) SYSTEM FOR DETECTION AND LOCATION OF EVENTS BASED ON OPTICAL INTERFEROMETRY WITH DOUBLE DELAY COIL, consisting of two optical interferometers configured for distinct paths, characterized by a first interferometer configured to operate with optical signals of wavelength 1530 nm, composed of a path containing mirrors configured to reflect the signal and stabilize its polarization; a second interferometer configured to operate with optical signals of wavelength 1550 nm, containing an add-drop type device, configured for direct passage of the optical signal; a double delay coil composed of optical fibers identical in length, with a preferred length tolerance between 1 and 2 cm, dimensioned to introduce a minimum delay of two to three kilometers in the optical signal of the second interferometer;Optical detectors associated with APS (Active Pixel Sensor) type sensors, configured to capture the rising and falling phases of the optical signals from each interferometer; a data capture board configured to simultaneously capture signals from the detectors, with reading capability on four independent channels and an adjustable capture rate of up to 10 MSPS per channel. 2) METHOD FOR DETECTION AND LOCATION OF EVENTS BASED ON OPTICAL INTERFEROMETRY WITH DOUBLE DELAY COIL, by the system described in claim 1, being characterized by a method comprising the steps of: - Emitting two optical signals of different wavelengths, being 1530 nm and 1550 nm, to distinct optical paths in two interferometers; - Stabilizing the polarization of the 1530 nm optical signal using mirrors; - Directing the 1550 nm optical signal through an add-drop type device; - Introducing an optical delay in the 1550 nm signal using a double delay coil composed of optical fibers identical in length, with a preferred length tolerance between 1 and 2 cm; Petition 870240110855, dated 12 / 27 / 2024, p.19 / 48 2 / 2 - Simultaneously capture the ascending and descending phases of the optical signals processed in each interferometer using optical detectors associated with APS sensors; - Record the signals on a data capture board configured to perform simultaneous readings on the channels of the two interferometers; - Correlate the ascending and descending phases of the captured signals to determine the phase difference between the optical paths. Petition 870240110855, dated 12 / 27 / 2024, page 20 / 48.

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