Method and system for detecting improper protection in optical communication network

Abstract

Systems and methods for detecting improper protection in an optical communications network are disclosed, the method comprising: i) a first coherent optical time domain reflectometer (C-OTDR) receiving a first reflected optical signal from a first optical fiber; ii) the second C-OTDR receives a second reflected light signal from a second optical fiber; iii) the processor preprocesses the first reflected light signal and the second reflected light signal; iv) the processor determines the category of the first C-OTDR and the category of the second C-OTDR; v) calculating a correlation between the first pre-processed reflected light signal and the second pre-processed reflected light signal based on a first correlation calculation technique or a second correlation calculation technique according to categories of the first C-OTDR and the second C-OTDR; and vi) detecting improper protection in the optical communication network based on the calculated correlation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application No. 18 / 183,256, filed on March 14, 2023, entitled “Method and System for Detecting an Improper Protection in an Optical Communication Network,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to the field of optical communication networks, and more particularly to methods and systems for detecting improper protection in optical communication networks. Background Art

[0004] Typical implementations of optical networks, such as dense wavelength division multiplexing (DWDM) networks, involve providing working and protection paths to provide seamless communication. Therefore, in the event of a fiber link failure in the working path, traffic is routed through the protection path. Such path protection generally requires that the fiber links of the working and protection paths be disjoint, reducing the likelihood of simultaneous disruption of the protection and working paths due to a failure on the same fiber link.

[0005] However, sometimes the optical layer violates the requirement that the working path's fiber links are independent and disjoint from the protection path. Such violations include at least a portion of the working path and a portion of the protection path sharing the same fiber, or sharing different fibers within the same cable, or sharing different fiber cables that are spatially close to each other.

[0006] For this reason, there is interest in developing efficient methods and systems for detecting improper protection in optical communication networks. Summary of the Invention

[0007] Embodiments of the present disclosure were developed based on the developers' understanding of the shortcomings associated with the prior art. Typically, conventional techniques for detecting improper protection in optical communication networks rely on a coherent optical time domain reflectometer (C-OTDR), which simultaneously monitors two optical fibers under test. Conventional techniques generate a 2D waterfall plot based on the optical fibers under test. In order to determine whether two optical fibers are co-cabled, a strong event around the optical fibers is required (e.g., a vehicle passing over a buried optical fiber) that can create clear and distinct patterns / features in the 2D waterfall plot. Conventional techniques rely on image processing techniques that require strong perturbations to distinguish between the two 2D waterfall plots. In practice, where optical fibers are subject to low-impact events and conditions, the optical fiber characteristics are weakly perturbated, causing the patterns / features in the 2D waterfall plot to be hidden in the noise.

[0008] Developers of the present disclosure have designed an efficient method and system for detecting improper protection in optical communication networks. More specifically, various embodiments of the present disclosure rely on correlations between optical signals reflected from optical fibers, rather than image processing techniques.

[0009] According to a first broad aspect of the present disclosure, a method for detecting improper protection in an optical communication network is provided, the method comprising: receiving a first reflected optical signal from a first optical fiber by a first coherent-optical time domain reflectometer (C-OTDR); receiving a second reflected optical signal from a second optical fiber by a second C-OTDR; preprocessing the first reflected optical signal and the second reflected optical signal by a processor; determining categories of the first C-OTDR and the second C-OTDR; wherein, upon determining that the categories of the first C-OTDR and the second C-OTDR are distributed acoustic sensing (DAS), calculating a correlation between the first preprocessed reflected optical signal and the second preprocessed reflected optical signal based on a first correlation calculation technique; wherein, upon determining that the categories of the first C-OTDR and the second C-OTDR are distributed vibration sensing (DVS), calculating a correlation between the first preprocessed reflected optical signal and the second preprocessed reflected optical signal based on a second correlation calculation technique; and detecting improper protection in the optical communication network based on the calculated correlation.

[0010] According to any embodiment of the present disclosure, the pre-processing includes one or more of: band-pass filtering, normalizing time / frequency components, and applying a non-linear gain.

[0011] According to any embodiment of the present disclosure, the first correlation calculation technique includes calculating a one-dimensional time-domain correlation between a first pre-processed reflected light signal reflected from a first position in a first optical fiber and a second pre-processed reflected light signal reflected from a second position in a second optical fiber over a given time duration T.

[0012] According to any embodiment of the present disclosure, the one-dimensional time domain correlation is calculated as follows:

[0013]

[0014] Among them, u a (t i ,z a ) is from the first position z a The first pre-processed reflected light signal, u b (t i ,z b ) is from the second position z b The second pre-processed reflected light signal is reflected, i is from 1 to n T The index of the change, and t i is a time index.

[0015] According to any embodiment of the present disclosure, the time index t i Related to index i as follows:

[0016] According to any embodiment of the present disclosure, the first correlation calculation technique includes calculating a two-dimensional time-domain correlation between a first pre-processed reflected light signal reflected from a first position in a first optical fiber over a length L and a second pre-processed reflected light signal reflected from a second position in a second optical fiber over a length L, within a given time duration T.

[0017] According to any embodiment of the present disclosure, the two-dimensional time domain correlation is calculated as follows:

[0018]

[0019] Among them, u a (t i ,z a +l j ) is from the first position z a Experience length l j The first pre-processed reflected light signal, u b (t i ,z b +l j ) is from the second position z b Experience length l j The second pre-processed reflected light signal is reflected, i is from 1 to nT The index of the change, j is from 1 to n L The index of the change, t i is the time index, and l j is the length index.

[0020] According to any embodiment of the present disclosure, the time index t i Related to index i as follows: And the length index l j Related to index j as follows:

[0021] According to any embodiment of the present disclosure, the first correlation calculation technique includes: calculating a one-dimensional time-domain correlation between a first preprocessed reflected light signal reflected from a first set of positions in a first optical fiber and a second preprocessed reflected light signal reflected from a second set of positions in a second optical fiber within a given time duration T; and calculating an average value of the one-dimensional time-domain correlations.

[0022] According to any embodiment of the present disclosure, for a first position from the first set of positions and a second position from the second set of positions, the associated one-dimensional time-domain correlation is calculated as follows:

[0023]

[0024] Among them, u a (t i ,z a +l j ) is from the first position z a +l j The first pre-processed reflected light signal, u b (t i ,z b +l j ) is from the second position z b +l j The second pre-processed reflected light signal is reflected, i is from 1 to n T The index of the change, and t i is a time index.

[0025] According to any embodiment of the present disclosure, the second correlation calculation technique includes calculating a two-dimensional frequency-domain correlation between an absolute frequency component of a first preprocessed reflected light signal reflected from a first position in a first optical fiber over a length L and an absolute frequency component of a second preprocessed reflected light signal reflected from a second position in a second optical fiber over a length L.

[0026] According to any embodiment of the present disclosure, the two-dimensional frequency domain correlation is calculated as follows:

[0027]

[0028] Among them, |U a (f i ,z a +l j )| is from the first position z a Experience length l j The absolute frequency component of the reflected first pre-processed reflected light signal, |U b (f i ,z b +l j )| is from the second position z b Experience length l j The absolute frequency component of the reflected second pre-processed reflected light signal, i is from 1 to n f The index of the change, j is from 1 to n L The index of the change, f i is the frequency index, and l j is the length index.

[0029] According to any embodiment of the present disclosure, the frequency index f i Related to index i as follows: Among them, f max and f min is the maximum and minimum value of the absolute frequency component, and the length index l j Related to index j as follows:

[0030] According to any embodiment of the present disclosure, the second correlation calculation technique includes: calculating one-dimensional frequency domain correlations between absolute frequency components of a first preprocessed reflected light signal reflected from a first set of positions in a first optical fiber and absolute frequency components of a second preprocessed reflected light signal reflected from a second set of positions in a second optical fiber; and calculating an average value of the one-dimensional frequency domain correlations.

[0031] According to any embodiment of the present disclosure, for a first position from the first set of positions and a second position from the second set of positions, the associated one-dimensional frequency domain correlation is calculated as follows:

[0032]

[0033] Among them, |U a (f i ,z a +l j )| is from the first position z a +l j The absolute frequency component of the reflected first pre-processed reflected light signal, |U b (f i ,z b +lj )| is from the second position z b +l j The absolute frequency component of the reflected second pre-processed reflected light signal, i is from 1 to n f The index of the change, and f i is the frequency index.

[0034] According to any embodiment of the present disclosure, detecting improper protection in an optical communication network is based on a correlation threshold.

[0035] According to any embodiment of the present disclosure, when the calculated correlation is greater than a correlation threshold, it is determined that the first optical fiber and the second optical fiber are located in close proximity causing improper protection in the optical communication network.

[0036] According to a second broad aspect of the present disclosure, a system for detecting improper protection in an optical communication network is provided, the system comprising: a first coherent-optical time domain reflectometer (C-OTDR) for receiving a first reflected optical signal from a first optical fiber; a second C-OTDR for receiving a second reflected optical signal from the first optical fiber; a non-transitory memory element having instructions therein; a processor coupled to the non-transitory memory element and executing the instructions to cause the processor to: pre-process the first reflected optical signal and the second reflected optical signal; determine categories of the first C-OTDR and the second C-OTDR; wherein, upon determining that the categories of the first C-OTDR and the second C-OTDR are distributed acoustic sensing (DAS), calculating a correlation between the first pre-processed reflected optical signal and the second pre-processed reflected optical signal based on a first correlation calculation technique; wherein, upon determining that the categories of the first C-OTDR and the second C-OTDR are distributed vibration sensing (DAS), calculating a correlation between the first pre-processed reflected optical signal and the second pre-processed reflected optical signal based on a first correlation calculation technique; When performing DVS (deep visual sensing), a correlation between the first preprocessed reflected light signal and the second preprocessed reflected light signal is calculated based on a second correlation calculation technique; and improper protection in the optical communication network is detected based on the calculated correlation.

[0037] According to any embodiment of the present disclosure, the first correlation calculation technique includes one of the following operations: calculating a one-dimensional time-domain correlation between a first preprocessed reflected light signal reflected from a first position in a first optical fiber and a second preprocessed reflected light signal reflected from a second position in a second optical fiber within a given time duration T; calculating a two-dimensional time-domain correlation between the first preprocessed reflected light signal reflected from the first position in the first optical fiber over a length L and the second preprocessed reflected light signal reflected from the second position in the second optical fiber over a length L within a given time duration T; and calculating a one-dimensional time-domain correlation between the first preprocessed reflected light signal reflected from a first group of positions in the first optical fiber and the second preprocessed reflected light signal reflected from a second group of positions in the second optical fiber within a given time duration T, and calculating an average value of the one-dimensional time-domain correlations.

[0038] According to any embodiment of the present disclosure, the second correlation calculation technique includes one of the following operations: calculating a two-dimensional frequency domain correlation between an absolute frequency component of a first preprocessed reflected light signal reflected from a first position in a first optical fiber over a length L and an absolute frequency component of a second preprocessed reflected light signal reflected from a second position in a second optical fiber over a length L; and calculating a one-dimensional frequency domain correlation between an absolute frequency component of the first preprocessed reflected light signal reflected from a first group of positions in the first optical fiber and an absolute frequency component of the second preprocessed reflected light signal reflected from a second group of positions in the second optical fiber; and calculating an average value of the one-dimensional frequency domain correlations. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0040] Figure 1 Describe a block diagram of an optical network;

[0041] Figure 2 (Prior Art) shows a 2D waterfall plot corresponding to two optical fibers generated using conventional techniques;

[0042] Figure 3 illustrates a high-level functional block diagram of a C-OTDR for assisting in detecting improper protection in an optical network in accordance with various non-limiting embodiments of the present disclosure;

[0043] Figure 4 2D waterfall graph w(t i ,z i );

[0044] Figure 5 A system for detecting improper protection in an optical network according to various non-limiting embodiments of the present disclosure is shown;

[0045] Figure 6 shows the two-dimensional frequency domain correlation C calculated according to various non-limiting embodiments of the present disclosure. 2D (z a ,z b ,L) simulation results;

[0046] Figure 7 shows the average one-dimensional frequency domain correlation C calculated according to various non-limiting embodiments of the present disclosure. 2D (z a ,z b ,L) simulation results;

[0047] Figure 8 depicts a high-level block diagram of representative components for a correlation analysis processor according to various embodiments of the present disclosure; and

[0048] Figure 9 Depicted is a flow chart representing a process related to a method for detecting improper protection in an optical communication network, according to various embodiments of the present disclosure.

[0049] It should be understood that throughout the drawings and corresponding descriptions, like features are identified by like reference numerals. In addition, it should be understood that the drawings and the following descriptions are for illustration purposes only, and such disclosure is not intended to limit the scope of the claims. DETAILED DESCRIPTION

[0050] The present disclosure is directed to addressing at least some of the deficiencies of conventional techniques. In particular, the present disclosure describes efficient systems and methods for detecting improper protection in optical communication networks.

[0051] Unless defined or indicated otherwise by the context, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the described embodiments belong.

[0052] In the context of this specification, a "controller" is any computer hardware capable of running software appropriate for the relevant task at hand. In the context of this specification, the term "client device" is generally associated with the user of the client device. Thus, some (non-limiting) examples of client devices include personal computers (desktops, laptops, netbooks, etc.), smartphones and tablets, as well as network devices such as routers, switches and gateways. It should be noted that a device acting as a client device in this context does not exclude acting as a server for other client devices. Use of the expression "client device" does not exclude multiple client devices being used to receive / send, perform or cause the performance of any task or request, or the consequences of any task or request, or the steps of any method described herein.

[0053] In the context of this specification, unless otherwise expressly provided, words such as "first," "second," and "third" are used as adjectives solely for the purpose of distinguishing the nouns they modify from one another, and not for the purpose of describing any particular relationship between those nouns. Thus, for example, it will be understood that the use of the terms "first processor" and "third processor" is not intended to imply any particular order, type, chronological order, hierarchy, or ranking (for example) of / between servers, nor is their use (per se) intended to imply that any "second server" must be present in any given situation. Furthermore, as discussed herein in other contexts, reference to a "first" element and a "second" element does not preclude the two elements from being the same actual, real-world element. Thus, for example, in some cases, a "first" server and a "second" server may be the same software and / or hardware, and in other cases, they may be different software and / or hardware.

[0054] It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly or indirectly connected or coupled to the other element or to intervening elements that may exist. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.) should be interpreted in a similar manner.

[0055] In the context of this specification, when an element is referred to as being “associated with” another element, in some embodiments, the two elements may be directly or indirectly linked, related, connected, coupled, the second element employing the first element, etc., without limiting the scope of the present disclosure.

[0056] The terms used herein are intended only to describe specific representative embodiments and are not intended to limit the present technology. Unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" used herein are intended to include the plural forms as well. It should also be understood that when used in this specification, the terms "include" and / or "comprise" indicate the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0057] Implementations of the present technology all include at least one of the above-mentioned objectives and / or aspects, but not necessarily all of them. It should be understood that some aspects of the present technology proposed in an attempt to achieve the above-mentioned objectives may not satisfy such objectives and / or may satisfy other objectives not specifically described herein.

[0058] The examples and conditional language described herein are primarily intended to help the reader understand the principles of the present technology, rather than to limit its scope to such specific examples and conditions. It should be understood that those skilled in the art can design various arrangements that, although not explicitly described or shown herein, embody the principles of the present technology and are included within its spirit and scope.

[0059] In addition, the following description may describe a relatively simplified implementation of the present technology to facilitate understanding. As those skilled in the art will appreciate, various implementations of the present technology may have higher complexity.

[0060] In some cases, examples of useful modifications to the present technology may also be described. This is done solely to aid understanding and, again, is not intended to define the scope of the present technology or to describe the limits of the present technology. These modifications are not an exhaustive list, and those skilled in the art may make other modifications while remaining within the scope of the present technology. Furthermore, the absence of examples of modifications should not be interpreted as implying that modifications are impossible and / or that the described approach is the only way to implement that element of the present technology.

[0061] In addition, all descriptions herein describing the principles, aspects, and implementations of the present technology, as well as specific examples thereof, are intended to encompass structural and functional equivalents thereof, whether currently known or developed in the future. Thus, for example, those skilled in the art will understand that any block diagram herein represents a conceptual view of an illustrative circuit embodying the principles of the present technology. Similarly, it should be understood that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes that can be substantially represented in a computer-readable medium and thus executed by a computer or processor, whether or not such a computer or processor is explicitly shown.

[0062] The functions of the various elements shown in the figure (including any functional blocks marked as "processor" or "processing unit") can be provided by using dedicated hardware and hardware that can execute software in association with appropriate software. When provided by a processor, these functions can be provided by a single dedicated processor, a single shared processor, or multiple separate processors, some of which can be shared. In some embodiments of the present technology, the processor can be a general-purpose processor, such as a central processing unit (CPU), or a processor dedicated to a specific purpose, such as a graphics processing unit (GPU). In addition, the explicit use of the term "processor" or "controller" should not be interpreted as referring specifically to hardware that can execute software, and can implicitly include but are not limited to digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read-only memory (ROM), random access memory (RAM) and non-volatile memory for storing software. Other traditional and / or custom hardware may also be included.

[0063] Software modules, modules or units implied as software may be represented herein as any combination of flow chart elements or other elements indicating process steps and / or performance described in the text. Such modules may be executed by hardware shown explicitly or implicitly.

[0064] With these basic elements, the present disclosure aims to address at least some of the deficiencies of the current technology.In particular, the present disclosure describes efficient systems and methods for detecting improper protection in optical communication networks.

[0065] Referring now to the accompanying drawings, Figure 1A block diagram of an optical network 100 is depicted. As shown, the optical network 100 generally includes multiple optical nodes, which may include optical multiplexing sections (OMSs), each of which includes optical add-drop multiplexers, such as reconfigurable optical add-drop multiplexers (ROADMs) A, B, C, D, E, and F, each of which includes at least one wavelength selective switch (WSS). Each node can be used to add, delete, and / or reroute wavelengths. Each OMS-based node may also include multiple optical transport sections (OTSs), where the wavelength remains the same at each OTS.

[0066] Each node in the optical network 100 may also include one or more laser light sources configured to generate, emit, or radiate light pulses having a specific pulse duration. In some embodiments, the one or more pulsed laser light sources may include one or more laser diodes, such as, but not limited to, a Fabry-Perot laser diode, a quantum well laser, a distributed Bragg reflector (DBR) laser, a distributed feedback (DFB) laser, or a vertical-cavity surface-emitting laser (VCSEL). By way of example only, a given laser diode may be an aluminum-gallium-arsenide (AlGaAs) laser diode, an indium-gallium-arsenide (InGaAs) laser diode, or an indium-gallium-arsenide-phosphide (InGaAsP) laser diode, or any other suitable laser diode.

[0067] It is also contemplated that the emitted light may be singly polarized, dual polarized, or randomly polarized, and may have a specific polarization (eg, linear, elliptical, or circular).

[0068] In addition, each node in the optical network 100 may include multiple optical amplifiers for amplifying optical signals, such as erbium-doped fiber amplifiers (EDFAs). The optical network 100 may also employ one or more optical network elements and modules (which may include either or both active and passive elements / modules), such as, for example, optical filters, WSSs, arrayed waveguide gratings, optical transmitters, optical receivers, processors, and other suitable components. However, for the purpose of simplicity and operability, these elements have been removed from the optical network. Figure 1 omitted.

[0069] It is contemplated that nodes in optical network 100 can be communicatively connected via links comprising optical cables, wherein each optical cable can include multiple optical fibers. The optical fibers can be of any suitable type, such as, for example, single-mode fiber, multimode fiber, standard single-mode fiber (SSMF), large effective area fiber (LEAF), etc. The links can also include multiple optical amplifiers, such as EDFAs. The link between two nodes can also include optical amplifiers.

[0070] As an example, the implementation of the optical network 100 may include a working path and a protection path. For example, in the optical network 100, the starting node may be node A and the destination node may be node F. Figure 1 As depicted at 102 in FIG. 1 , working path 104 and protection path 106 can be disjoint in terms of optical fibers or cables. For example, in implementation 102, working path 104 can be implemented using the path A→C→E→F, and protection path 106 can be implemented using the path A→B→D→F. As shown, in implementation 102, working path 104 and protection path 106 are completely disjoint. Therefore, if any optical cable or fiber within a cable fails for any reason along the working path, traffic between node A and node F can be redirected to the protection path.

[0071] In other implementations, such as Figure 1As depicted in implementation 108 of FIG, at least a portion of working path 110 and a portion of protection path 112 share the same optical fiber, or share different optical fibers within the same optical cable, or share different optical fiber cables that are very close to each other. For example, in implementation 108, working path 110 can be implemented using the path A→C→E→F, while protection path 112 can be implemented using the path A→B→C→E→D→F. As shown, in implementation 108, both working path 110 and protection path 112 have a common path segment C→E. To this end, in the event that any optical fiber in the optical cable fails for any reason, traffic between node A and node F can be redirected from working path 110 to protection path 112. However, if a failure occurs along path C→E, communication between node A and node B will be completely interrupted for both working path 110 and protection path 112.

[0072] Typically, for the survivability of optical network 100, in the event of a failure in working path 104, a common practice is to retain protection path 106 to detour data traffic. For maximum protection, working path 104 and protection path 106 need to be geographically disjoint. However, numerous scenarios of improper protection exist in the art, where working path 104 and protection path 106 ultimately share at least a portion of the same optical fiber, optical cable, or pipe / trench. To proactively protect networks, systems and methods for identifying improper protection are urgently needed. Various embodiments of the present disclosure are directed to detecting improper design / allocation of protection paths in optical networks.

[0073] Traditional techniques rely on a coherent optical time domain reflectometer (C-OTDR), which simultaneously monitors two fibers under test. This technique generates a 2D waterfall plot based on the fibers under test. To determine whether two fibers are co-cabled, a strong event around the fibers (e.g., a vehicle passing over a buried fiber) is required. This strong event can create a clear and distinct pattern / signature in the 2D waterfall plot.

[0074] Figure 2 (Prior Art) shows 2D waterfall plots 200 corresponding to two optical fibers generated using conventional techniques. Conventional techniques rely on image processing techniques, which require strong perturbations to distinguish between the two 2D waterfall plots. In practice, where optical fibers are subject to low-impact events and conditions, the fiber characteristics may be weakly perturbed, causing the patterns / features in the 2D waterfall plots to be hidden in the noise. A straightforward conventional approach is to intentionally apply strong mechanical vibrations to the area containing the optical fibers to obtain clear features in the 2D waterfall plots. However, such an approach increases the operational cost and complexity of the testing process.

[0075] Various embodiments of the present disclosure rely on a coherent-OTDR (C-OTDR) to detect improper protection in the optical network 100 . Figure 3 A high-level functional block diagram of a C-OTDR 300 for assisting in detecting improper protection in an optical network 100 according to various non-limiting embodiments of the present disclosure is shown. As shown, the C-OTDR 300 may include a narrow linewidth laser 302, an optical splitter 304, an electrical function generator 306, an optical modulator 308, an input port 310, a detector 314, an analog-to-digital converter (ADC) 316, and a processor 318. It is contemplated that the illustrated components corresponding to the C-OTDR 300 are merely representative and that the C-OTDR 300 may include components not shown for simplicity. Figure 3 Additional components not shown.

[0076] Narrow linewidth laser 302 can generate a highly coherent optical signal with a long coherence time. The amplitude / phase of the coherent optical signal can be internally or externally modulated by optical modulator 308 using a modulation signal generated by electrical function generator 306. Optical modulator 308 can generate an arbitrarily modulated / coded optical signal for transmission into optical fiber under test 312. At least a portion of the optical signal can be backscattered from optical fiber under test 312. The backscattered optical signal can be reflected to input port 310. Input port 310 can redirect the backscattered optical signal to detector 314.

[0077] As described above, the optical signal launched into the fiber under test 312 may be coherent and have a long coherence time, and therefore, the backscattered optical signal may be the result of coherent interference caused by the inhomogeneity of the fiber under test 312. Such coherent optical interference may be highly sensitive to the local strain / temperature of the fiber under test 312, which itself depends on the dynamic mechanical / thermal conditions surrounding the fiber under test 312. Various embodiments of the present disclosure may benefit from the sensitivity of identifying whether the main path and the protection path are affected by similar environmental conditions due to their close proximity (meaning improper protection or proper protection, respectively).

[0078] It is contemplated that the detector 314 in the C-OTDR may be based on a distributed vibration sensing (DVS) system or a distributed acoustic sensing (DAS) system. The parameters to be monitored may be the amplitude / phase / state of polarization information in the backscattered optical signal. Typically, in a DVS system, amplitude information is collected, while in a DAS system, full-wave information (in-phase and quadrature) of the backscattered optical signal is collected. DAS and DVS systems may have single polarization or polarization diversity designs on the transmitter and / or receiver side.

[0079] The detector 314 may employ direct or coherent detection schemes corresponding to DVS or DAS systems, respectively. For coherent detection, for example, a reference oscillator may be required to beat the backscattered signal at the optical splitter 304 with the detector 314.

[0080] Typically, short optical pulses are periodically launched into the optical fiber under test 312. For each single pulse, as the optical signal propagates along the optical fiber until its end, the trajectory of the parameter of interest in the received backscattered optical signal relative to the location of the scattering origin (i.e., the fast axis, z) can be captured. The fast axis (z) can be discretized (z) corresponding to the sampling rate of the ADC 316. j ). C-OTDR 300 can i Emission T Pulses, n T The backscattered traces can be captured by the detector 314 to form a 2D waterfall graph w(t i ,z i ), which is a 2D waterfall diagram showing how the backscattered optical signal from different positions (fast axis, z) of the optical fiber under test 312 changes with time (slow axis, t).

[0081] Figure 4 A 2D waterfall graph w(t,z) 400 is shown according to various non-limiting embodiments of the present disclosure. The 2D waterfall graph w(t,z) 400 may be composed of the graphs corresponding to n T The C-OTDR 300 generates pulses, each separated by a time interval T.

[0082] Figure 5A system 500 for detecting improper protection in an optical network 100 according to various non-limiting embodiments of the present disclosure is shown. As shown, the system 500 may include a first C-OTDR 502, a second C-OTDR 504, and a correlation analysis processor 506. The C-OTDR 502 and the C-OTDR 504 may be implemented similarly to the C-OTDR 300. The system 500 may include additional components, however, for simplicity purposes, such components have been removed. Figure 5 omitted.

[0083] The first C-OTDR 502 may be configured to transmit a first optical signal to a first optical fiber under test 508. The first optical signal may include optical pulses generated at equal time intervals. The first optical signal may be reflected from the first optical fiber under test 508. The first C-OTDR 502 may receive the first reflected signal and generate a first 2D waterfall signal w a (t, z). In a similar manner, the second C-OTDR 504 can be used to transmit a second optical signal to the second optical fiber under test 510. The second optical signal can include optical pulses generated at equal time intervals. The second optical signal can be reflected from the second optical fiber under test 510. The second C-OTDR 504 can receive the second reflected signal, and the first C-OTDR 504 can generate a second 2D waterfall signal w b The first C-OTDR 502 and the second C-OTDR 504 may provide a 2D waterfall signal w to the correlation analysis processor 506. a (t,z) and w b (t,z).

[0084] The correlation analysis processor 506 may perform a first 2D waterfall signal w a (t,z) and the second 2D waterfall signal w b

[0046] A correlation operation is performed between (t, z) to determine any similarities therebetween. Based on the similarities, the correlation analysis processor 506 can determine whether the first fiber under test 508 and the second fiber under test 510 are in close proximity.

[0085] In order to further improve the performance of the system 500, the correlation analysis processor 506 may process the first 2D waterfall signal w a (t,z) and the second 2D waterfall signal w b (t,z) is preprocessed. The preprocessing may include bandpass filtering, normalization of the time / frequency components, and application of nonlinear gain.

[0086] The correlation analysis processor 506 may process the first 2D waterfall signal w a (t,z) and the second 2D waterfall signal w b(t, z) performs bandpass filtering to suppress low-frequency laser noise and high-frequency white noise outside the expected vibration range. In certain non-limiting embodiments, the bandpass filtering can be in the frequency range of 10 Hz to 500 Hz.

[0087] In certain non-limiting embodiments, the correlation analysis processor 506 may normalize the first 2D waterfall signal w over the entire length of the first optical fiber under test 508 and the second optical fiber under test 510, respectively. a (t,z) and the second 2D waterfall signal w b The frequency content of (t,z). The normalization process can provide a balance for the vibration sources at different frequencies in the correlation results.

[0088] In certain non-limiting embodiments, the correlation analysis processor 506 may apply nonlinear gains in the time domain or the frequency domain to provide higher weights to disturbance events in the correlation operation, thereby improving the performance of the system 500 .

[0089] Through pre-processing, the correlation analysis processor 506 can respectively a (t,z) and the second 2D waterfall signal w b (t, z) generates the first pre-processed reflected light signal u a (t, z) and the second pre-processed reflected light signal u b (t, z). The correlation analysis processor 506 can use the first pre-processed reflected light signal u a (t, z) and the second pre-processed reflected light signal u b (t,z) to calculate the correlation.

[0090] As described above, the first C-OTDR 502 and the second C-OTDR 504 can be based on a DAS system or a DVS system. The correlation analysis processor 506 can customize the correlation operation based on the category of the first C-OTDR 502 and the second C-OTDR 504. The correlation analysis processor 506 can determine the category of the first C-OTDR 502 and the second C-OTDR 504. In the case where the determined category is a DAS system, the correlation analysis processor 506 can calculate the first pre-processed reflected light signal u based on the first correlation calculation technique. a (t, z) and the second pre-processed reflected light signal u b In the case that the determined category is the DVS system, the correlation analysis processor 506 can calculate the first pre-processed reflected light signal u based on the second correlation calculation technology. a (t, z) and the second pre-processed reflected light signal u b The correlation between (t,z).

[0091] The DAS system may not be linear because the changes in the system output may not necessarily be linearly related to the input perturbations experienced by the first fiber under test 508 and the second fiber under test 510. Therefore, under the same input perturbation, the first fiber under test 508 and the second fiber under test 510 may produce different output signal trajectories with little correlation. Accordingly, in some embodiments, the correlation analysis processor 506 can formulate a differential phase (Φ(t,z+Δz)-Φ(t,z)) that can vary nearly linearly with fiber perturbations and can be partially immune to common noise terms.

[0092] In order to determine its longitudinal position z a Is the first optical fiber 508 under test at its longitudinal position z b The correlation analysis processor 506 can calculate the first position z in the first measured fiber 508 within a given time duration T. a The first pre-processed reflected light signal u a (t, z) and the second position z in the second measured optical fiber 510 b The reflected second pre-processed reflected light signal u b One-dimensional time-domain correlation between (t,z).

[0093] The one-dimensional time domain correlation can be calculated as:

[0094]

[0095] Among them, u a (t i ,z a ) can be from the first position z a The first pre-processed reflected light signal, u b (t i ,z b ) is from the second position z b The second pre-processed reflected light signal is reflected, i can be from 1 to n T The index of the change, and t i Can be a time index. Time index t i can be related to index i as follows: At position z a The first optical fiber under test 508 at position z b In case the second optical fiber under test 510 is in close proximity, the calculated correlation may show a peak.

[0096] It is conceivable that the first optical fiber under test 508 and the second optical fiber under test 510 can share at least a portion of the corresponding path, and calculate the first pre-processed reflected light signal u on L a (t, z) and the second pre-processed reflected light signal u b The correlation between (t, z) can provide a stronger correlation. The correlation analysis processor 506 can calculate the time duration T from the first position z in the first measured fiber 508. a The first pre-processed reflected light signal u undergoes a reflection of length L a (t, z) and the second position z in the second measured optical fiber 510 b The second pre-processed reflected light signal u undergoes a reflection of length L b In other words, the correlation analysis processor 506 can calculate the two-dimensional time domain correlation between the first measured optical fiber 508 from the position z a to z a +L reflected first pre-processed reflected light signal u a (t, z) and the second measured optical fiber 510 from position z b to z b +L reflected second pre-processed reflected light signal u b The correlation between (t,z).

[0097] The value of L may be preset based on a minimum expected value of the common length of the first tested fiber 508 and the second tested fiber 510 , considering that a longer L may support stronger correlation, which translates into higher reliability in detecting improper protection in the optical network 100 .

[0098] The two-dimensional time domain correlation can be calculated as:

[0099]

[0100] Among them, u a (t i ,z a +l j ) can be from the first position z a Experience length l j The first pre-processed reflected light signal, u b (t i ,z b +l j ) can be from the second position z b Experience length l j The second pre-processed reflected light signal is reflected, i can be from 1 to n T The variable index, j can be from 1 to n L The index of the change, t ican be a time index, and l j Can be a length index. Time index t i can be related to index i as follows: And the length index l j Related to index j as follows:

[0101] In addition, in order to improve performance, in some non-limiting embodiments, the correlation analysis processor 506 performs a two-dimensional time domain correlation C 2D (z a ,z b ,L)Averaging to improve the detectability of peaks.

[0102] Return to Figure 5 In another embodiment, the first correlation calculation technique can be used to calculate the first pre-processed reflected light signal u reflected from the first set of positions in the first measured optical fiber 508 within a given duration T. a (t, z) and the second pre-processed reflected light signal u reflected from the second group of positions in the second measured optical fiber 510 b The first set of positions in the first measured fiber 508 can be referred to as positions z. a With z a The second set of positions in the second fiber under test 510 can be referred to as positions z. b With z b +L. The correlation analysis processor 506 can calculate the first pre-processed reflected light signal u within a given duration T for each position in the first group of positions and the second group of positions. a (t, z) and the second pre-processed reflected light signal u b The correlation between (t,z).

[0103] Additionally, the correlation analysis processor 506 can calculate an average of all one-dimensional time-domain correlations. In doing so, the correlation analysis processor 506 can calculate a two-dimensional time-domain correlation based on the one-dimensional time-domain correlations. In some cases, this embodiment of the technique for calculating correlations can provide greater resistance to false detections of improper protection because this technique provides equalization of correlations.

[0104] The one-dimensional time domain correlation and the average value of the correlation can be calculated as:

[0105]

[0106]

[0107] Return to Figure 5As described above, in the case where the determined category is the DVS system, the correlation analysis processor 506 may calculate the first pre-processed reflected light signal u based on the second correlation calculation technique. a (t, z) and the second pre-processed reflected light signal u b The correlation between (t,z).

[0108] In the DVS system, when the first optical fiber under test 508 and the second optical fiber under test 510 are in close proximity, the time-invariant characteristics of the system can be obtained by a (t, z) and the second pre-processed reflected light signal u b A strong correlation is achieved in terms of the absolute frequency content between (t, z). Therefore, in some embodiments, the absolute frequency content can be used for the second correlation calculation technique.

[0109] In some embodiments, the correlation analysis processor 506 may calculate the first pre-processed reflected light signal u a (t, z) and the second pre-processed reflected light signal u b Discrete Fourier transform (DFT) of (t,z).

[0110] In the f The discrete points from f min to f max In the frequency range of the first pre-processed reflected light signal u a (t, z) and the second pre-processed reflected light signal u b The correlation between the absolute frequency content of (t,z) can be calculated as:

[0111]

[0112] Among them, |U a (f i ,z a +l j )| is from the first position z a Experience length l j The first pre-processed reflected light signal u a The absolute frequency component of (t,z), |U b (f i ,z b +l j )| is from the second position z b Experience length l j The reflected second pre-processed reflected light signal u b The absolute frequency component of (t,z), i is from 1 to n f The index of the change, j is from 1 to nL The index of the change, f i is the frequency index, and l j is the length index. The frequency index f i Related to index i as follows: Among them, f max and f min is the maximum and minimum value of the absolute frequency component, and the length index l j Related to index j as follows: f can be set by the frequency filtering process applied in the preprocessing stage min to f max The value of .

[0113] Return to Figure 5 In another embodiment, the second correlation calculation technique can be used to calculate the first pre-processed reflected light signal u reflected from the first set of positions in the first measured optical fiber 508 within a given duration T. a (t, z) and the second pre-processed reflected light signal u reflected from the second group of positions in the second measured optical fiber 510 b One-dimensional frequency domain correlation between (t,z).

[0114] Additionally, the correlation analysis processor 506 can calculate an average of all one-dimensional frequency domain correlations. In doing so, the correlation analysis processor 506 can calculate a two-dimensional frequency domain correlation based on the one-dimensional frequency domain correlations. In some cases, this embodiment of the technique for calculating correlations can provide greater resistance to false detections of improper protection because this technique provides equalization of correlations.

[0115] The one-dimensional frequency domain correlation and the average value of the correlation can be calculated as:

[0116]

[0117]

[0118] Figure 6 shows the two-dimensional frequency domain correlation C calculated according to various non-limiting embodiments of the present disclosure. 2D (z a ,z b ,L) simulation results 600. In one example, z a Fixed at 4800m, and L set to 100m, z b Scan from 0m to 9900m. b =The peak at 4805m is from 4800m to 4900m (z a +L) and the first tested optical fiber 508 from 4805m to 4905m (z b+L) is very close to the second optical fiber under test 510.

[0119] Figure 7 shows the average one-dimensional frequency domain correlation C calculated according to various non-limiting embodiments of the present disclosure. 2D (z a ,z b ,L) simulation results 700. As shown in the figure, the average one-dimensional frequency domain correlation can illustrate a higher ability to resist false detection and has greater suppression of misleading peaks at 3495m and 6460m.

[0120] Once the correlation is calculated, the correlation analysis processor 506 can detect improper protection in the optical communication network based on a correlation threshold. The correlation threshold can be set based on a peak in the calculated correlation. If the calculated correlation is greater than the correlation threshold, it can be determined that the first optical fiber under test 508 and the second optical fiber under test 510 are in close proximity, resulting in improper protection in the optical network 100.

[0121] Figure 8 A high-level block diagram of representative components for the correlation analysis processor 506 is depicted in accordance with various embodiments of the present disclosure. It should be understood that Figure 8 This provides only an illustration of one implementation of the correlation analysis processor 506 and is not intended to imply any limitations on the environments in which different embodiments may be implemented. Many modifications may be made to the depicted environment to implement the correlation analysis processor 506 without departing from the principles presented herein.

[0122] As shown, the correlation analysis processor 506 uses one or more processors 802, one or more computer-readable random access memories (RAMs) 804, one or more computer-readable read-only memories (ROMs) 806, one or more computer-readable storage media 808, device drivers 814, read / write (R / W) interfaces 816, and network interfaces 818, all of which are interconnected via a communications fabric 820. The communications fabric 820 can be implemented using any architecture designed to transfer data and / or control information between processors (such as microprocessors, communications and network processors, etc.), memories, peripheral devices, and any other hardware components within the system.

[0123] One or more operating systems 810 and one or more application programs 812 are stored on one or more of the computer-readable storage media 808 for execution by one or more of the processors 802 via one or more of the corresponding RAMs 804 (which typically include cache memory). In the embodiment shown, each of the computer-readable storage media 808 can be a magnetic disk storage device such as an internal hard drive, a CD-ROM, a DVD, a memory stick, a tape, a magnetic disk, an optical disk, a semiconductor memory device such as RAM, ROM, EPROM, flash memory, or any other computer-readable tangible storage device that can store computer programs and digital information.

[0124] The correlation analysis processor 506 may also include a R / W drive or interface 816 to read from and write to one or more portable computer-readable storage media 828. The application 812 on the device may be stored on one or more of the portable computer-readable storage media 828, read through the corresponding R / W drive or interface 816, and loaded into the corresponding computer-readable storage medium 808.

[0125] It should be understood that in certain embodiments, the application programs 812 stored on one or more of the portable computer-readable storage media 828 may configure the dependency analysis processor 506 to provide various functionalities in accordance with various embodiments of the present disclosure.

[0126] The application program 812 on the correlation analysis processor 506 can be downloaded from an external computer or an external storage device to the correlation analysis processor 506 via a communication network (e.g., the Internet, a local area network, or other wide area network or wireless network) and a network interface 818. The program can be loaded onto the computer-readable storage medium 808 from the network interface 818.

[0127] The correlation analysis processor 506 may also include a display screen 822, a keyboard or keypad 824, and a computer mouse or touchpad 826. The device driver 814 may be connected to the display screen 822 for imaging, to the keyboard or keypad 824, to the computer mouse or touchpad 826, and / or to the display screen 822 for pressure sensing for alphanumeric character entry and user selection (in the case of a touch screen display). The device driver 814, the R / W interface 816, and the network interface 818 may include hardware and software (stored on the computer-readable storage medium 808 and / or ROM 804).

[0128] The programs described herein are identified based on the applications in which they are implemented in specific embodiments of the present disclosure. However, it should be understood that any particular program nomenclature used herein is for convenience only, and thus, the present disclosure should not be limited to use solely in any specific application identified and / or implied by such nomenclature.

[0129] It should be understood that the correlation analysis processor 506 can be a server, a desktop computer, a laptop computer, a tablet computer, a smartphone, a personal digital assistant, or any device that can be used to implement the present technology, as will be understood by those skilled in the art.

[0130] Figure 9 A flow chart is depicted indicating a process 900 of a method for detecting improper protection in an optical communication network according to various embodiments of the present disclosure. As shown, the process 900 begins at step 902 where a first C-OTDR 502 receives a first reflected optical signal from a first optical fiber under test 508 .

[0131] The process 900 proceeds to step 904 where the second C-OTDR 504 receives a second reflected optical signal from the second optical fiber under test 510 .

[0132] The process 900 continues to step 906 where the correlation analysis processor 506 pre-processes the first reflected light signal and the second reflected light signal. The pre-processing may include band-pass filtering, normalization of time / frequency components, and application of nonlinear gain.

[0133] The process 900 moves to step 908, where the correlation analysis processor 506 determines the categories of the first C-OTDR 502 and the second C-OTDR 504. The first C-OTDR 502 and the second C-OTDR 504 may be based on DAS technology or DVS technology.

[0134] Process 900 proceeds to step 910 where, upon determining that the categories of the first C-OTDR 502 and the second C-OTDR 504 are DAS, the correlation analysis processor 506 calculates correlations between the first preprocessed reflected light signal and the second preprocessed reflected light signal based on a first correlation calculation technique.

[0135] Process 900 continues to step 912 where, upon determining that the categories of the first C-OTDR 502 and the second C-OTDR 504 are DVS, the correlation analysis processor 506 calculates the correlation between the first preprocessed reflected light signal and the second preprocessed reflected light signal based on a second correlation calculation technique.

[0136] Finally, in step 914 , the correlation analysis processor 506 detects improper protection in the optical communication network based on the calculated correlation.

[0137] It should be understood that the operations and functions of the various systems and methods, components and associated processes of the present disclosure can be implemented by any one or more of hardware-based, software-based or firmware-based elements. Such operational alternatives do not limit the scope of the present invention in any way.

[0138] It should also be understood that although the embodiments set forth herein have been described with reference to specific features and structures, it is clear that various modifications and combinations can be made without departing from such disclosure. Therefore, the specification and drawings are to be regarded only as illustrative of the implementations or embodiments discussed and their principles as defined by the appended claims, and are intended to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.

Claims

1. A method for detecting improper protection in an optical communication network, characterized in that The method comprises: A first coherent optical time domain reflectometer (C-OTDR) receives a first reflected optical signal from the first optical fiber; The second C-OTDR receives a second reflected light signal from the second optical fiber; The processor preprocesses the first reflected light signal and the second reflected light signal; The processor determines the categories of the first C-OTDR and the second C-OTDR; When it is determined that the categories of the first C-OTDR and the second C-OTDR are distributed acoustic sensing (DAS), a correlation between the first preprocessed reflected light signal and the second preprocessed reflected light signal is calculated based on a first correlation calculation technique; When it is determined that the categories of the first C-OTDR and the second C-OTDR are distributed vibration sensing (DVS), a correlation between the first preprocessed reflected light signal and the second preprocessed reflected light signal is calculated based on a second correlation calculation technique; and Based on the calculated correlation, the improper protection in the optical communication network is detected.

2. The method according to claim 1, characterized in that The pre-processing includes one or more of: band-pass filtering, normalizing time / frequency components, and applying a non-linear gain.

3. The method according to claim 1, characterized in that The first correlation calculation technique includes calculating a one-dimensional time domain correlation between the first pre-processed reflected light signal reflected from a first position in the first optical fiber and the second pre-processed reflected light signal reflected from a second position in the second optical fiber within a given time duration T.

4. The method according to claim 3, characterized in that The one-dimensional time domain correlation is calculated as follows: Among them, u a (t i ,z a ) is from the first position z a The first pre-processed reflected light signal, u b (t i ,z b ) is from the second position z b The second pre-processed reflected light signal of the reflection, i is from 1 to n T The index of the change, and t i is a time index.

5. The method according to claim 4, characterized in that The time index t i The index i is related as follows:

6. The method according to claim 1, characterized in that The first correlation calculation technique includes calculating a two-dimensional time-domain correlation between the first pre-processed reflected light signal reflected from a first position in the first optical fiber over a length L and the second pre-processed reflected light signal reflected from a second position in the second optical fiber over the length L within a given duration T.

7. The method according to claim 6, characterized in that The two-dimensional time domain correlation is calculated as follows: Among them, u a (t i ,z a +l j ) is from the first position z a Experience length l j The first pre-processed reflected light signal, u b (t i ,z b +l j ) is from the second position z b Experience length l j The second pre-processed reflected light signal of the reflection, i is from 1 to n T The index of the change, j is from 1 to n L The index of the change, t i is the time index, and l j is the length index.

8. The method according to claim 7, characterized in that The time index t i The index i is related as follows: The length index l j The index j is related as follows:

9. The method according to claim 1, characterized in that The first correlation calculation technology includes: calculating a one-dimensional time-domain correlation between the first pre-processed reflected light signal reflected from a first group of positions in the first optical fiber and the second pre-processed reflected light signal reflected from a second group of positions in the second optical fiber within a given time duration T; and The average value of the one-dimensional time-domain correlation is calculated.

10. The method according to claim 9, characterized in that For a first position from the first set of positions and a second position from the second set of positions, the associated one-dimensional time-domain correlation is calculated as follows: Among them, u a (t i ,z a +l j ) is from the first position z a +l j The first pre-processed reflected light signal, u b (t i ,z b +l j ) is from the second position z b +l j The second pre-processed reflected light signal of the reflection, i is from 1 to n T The index of the change, and t i is a time index.

11. The method according to claim 1, wherein The second correlation calculation technique includes calculating a two-dimensional frequency domain correlation between an absolute frequency component of the first preprocessed reflected light signal reflected from a first position in the first optical fiber over a length L and an absolute frequency component of the second preprocessed reflected light signal reflected from a second position in the second optical fiber over the length L.

12. The method according to claim 11, characterized in that The two-dimensional frequency domain correlation is calculated as follows: Among them, |U a (f i ,z a +l j )| is from the first position z a Experience length l j The absolute frequency component of the reflected light signal of the first preprocessing, |U b (f i ,z b +l j )| is from the second position z b Experience length l j The absolute frequency component of the reflected light signal of the second pre-processing is reflected, i is from 1 to n f The index of the change, j is from 1 to n L The index of the change, f i is the frequency index, and l j is the length index.

13. The method according to claim 12, characterized in that The frequency index f i The index i is related as follows: Among them, f max and f min is the maximum and minimum value of the absolute frequency component, the length index l j The index j is related as follows:

14. The method according to claim 1, wherein The second correlation calculation technique includes: calculating a one-dimensional frequency domain correlation between the absolute frequency components of the first preprocessed reflected light signal reflected from a first set of positions in the first optical fiber and the absolute frequency components of the second preprocessed reflected light signal reflected from a second set of positions in the second optical fiber; and Calculate the average value of the one-dimensional frequency domain correlation.

15. The method according to claim 14, characterized in that For a first position from the first set of positions and a second position from the second set of positions, the associated one-dimensional frequency domain correlation is calculated as follows: Among them, |U a (f i ,z a +l j )| is from the first position z a +l j The absolute frequency component of the reflected light signal of the first preprocessing, |U b (f i ,z b +l j )| is from the second position z b +l j The absolute frequency component of the reflected light signal of the second pre-processing is reflected, i is from 1 to n f The index of the change, and f i is the frequency index.

16. The method according to any one of claims 1 to 15, characterized in that Detecting the improper protection in the optical communication network is based on a correlation threshold.

17. The method according to claim 16, characterized in that When the calculated correlation is greater than the correlation threshold, it is determined that the first optical fiber and the second optical fiber are located in close proximity causing the improper protection in the optical communication network.

18. A system for detecting improper protection in an optical communication network, characterized in that The system comprises: a first coherent optical time domain reflectometer (C-OTDR), configured to receive a first reflected optical signal from the first optical fiber; a second C-OTDR, configured to receive a second reflected optical signal from the first optical fiber; a non-transitory memory element having instructions therein; a processor coupled to the non-transitory memory element and executing the instructions to cause the processor to: preprocessing the first reflected light signal and the second reflected light signal; Determining categories of the first C-OTDR and the second C-OTDR; When it is determined that the categories of the first C-OTDR and the second C-OTDR are distributed acoustic sensing (DAS), a correlation between the first preprocessed reflected light signal and the second preprocessed reflected light signal is calculated based on a first correlation calculation technique; When it is determined that the categories of the first C-OTDR and the second C-OTDR are distributed vibration sensing (DVS), a correlation between the first preprocessed reflected light signal and the second preprocessed reflected light signal is calculated based on a second correlation calculation technique; and Based on the calculated correlation, the improper protection in the optical communication network is detected.

19. The system according to claim 18, wherein: The first correlation calculation technique includes one of the following operations: calculating a one-dimensional time-domain correlation between the first pre-processed reflected light signal reflected from a first position in the first optical fiber and the second pre-processed reflected light signal reflected from a second position in the second optical fiber within a given time duration T; calculating, within a given duration T, a two-dimensional time-domain correlation between the first pre-processed reflected light signal reflected from a first position in the first optical fiber over a length L and the second pre-processed reflected light signal reflected from a second position in the second optical fiber over the length L; as well as Calculate the one-dimensional time-domain correlation between the first preprocessed reflected light signal reflected from a first group of positions in the first optical fiber and the second preprocessed reflected light signal reflected from a second group of positions in the second optical fiber within a given time duration T, and calculate the average value of the one-dimensional time-domain correlation.

20. The system according to claim 18 or 19, characterized in that The second correlation calculation technique includes one of the following operations: Calculating a two-dimensional frequency domain correlation between an absolute frequency component of the first preprocessed reflected light signal reflected from a first position in the first optical fiber over a length L and an absolute frequency component of the second preprocessed reflected light signal reflected from a second position in the second optical fiber over the length L; as well as calculating a one-dimensional frequency domain correlation between the absolute frequency components of the first preprocessed reflected light signal reflected from a first group of positions in the first optical fiber and the absolute frequency components of the second preprocessed reflected light signal reflected from a second group of positions in the second optical fiber; And the average value of the one-dimensional frequency domain correlation is calculated.

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