Optical transmission system and method

Abstract

To provide an optical transmission system and a method for determining whether the optical transmission system is functioning properly.SOLUTION: An optical transmission system includes a transceiver configured to output an optical signal to a first optical fiber core of a multicore fiber (MCF), a second optical fiber core proximate to the first optical fiber core within the MCF, configured to receive crosstalk of reflected portions of the optical signal from the first optical fiber core, a detector configured to receive the crosstalk of the reflected portions of the optical signal and generate detection data based on the crosstalk of the reflected portions of the optical signal, and a controller configured to receive information related to the detection data and determine whether the optical transmission system is functioning properly based on the detection data.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Optical transmission systems can be used to transmit data over long distances. In some cases, optical transmission systems are used for intercontinental data transmission via optical fibers laid along the ocean floor. In some cases, monitoring of optical transmission systems is performed using reflected light repeater outputs or optical time domain reflectometer (ODTR) techniques. These systems utilize circuitry to return a portion of the optical signal transmitted along the optical fiber to a detector at the source of the optical signal. The returned light is analyzed to determine whether the optical transmission system is functioning properly. [Background technology]

[0002] Some optical transmission systems use single-core fiber (SCF) to carry the optical signal. Some optical transmission systems use multi-core fiber (MCF) to carry the optical signal. In some cases, optical transmission systems that use MCF to implement circuitry for returning a portion of the optical signal to a detector use a fan-in-fan-out (FIFO) structure. Summary of the Invention [Problem to be solved by the invention]

[0003] Improved techniques for determining whether an optical transmission system is functioning properly are desirable. [Means for solving the problem]

[0004] One aspect of the present specification is an optical transmission system comprising: a transceiver configured to output an optical signal to a first optical fiber core; a repeater connected to the first optical fiber core and configured to increase the intensity of the optical signal; a second optical fiber core proximate to the first optical fiber core and configured to receive crosstalk from the first optical fiber core and to reflect a portion of the crosstalk of the optical signal back to the transceiver; a detector configured to receive the reflected portion of the crosstalk of the optical signal and to receive detection data based on the reflected portion of the crosstalk of the optical signal; and a controller configured to receive information related to the detection data, to determine whether the optical transmission system is functioning properly based on the detection data, and to determine a location of a fault in the optical transmission system in response to determining that the optical transmission system is not functioning properly.

[0005] One aspect of the present specification is an optical transmission system comprising: a transceiver configured to output an optical signal to a first optical fiber core of a multi-core fiber (MCF), the first optical fiber core being configured to reflect a portion of the optical signal back to the transceiver; a second optical fiber core proximate to the first optical fiber core, located within the MCF, and configured to receive crosstalk of the reflected portion of the optical signal from the first optical fiber core; a detector configured to receive the crosstalk of the reflected portion of the optical signal and to generate detection data based on the crosstalk of the reflected portion of the optical signal; and a controller configured to receive information regarding the detection data, to determine whether the optical transmission system is functioning properly based on the detection data, and to determine a location of a fault in the optical transmission system in response to determining that the optical transmission system is not functioning properly.

[0006] One aspect of the present specification is a method for determining performance of an optical transmission system, the method including transmitting an optical signal along a first optical fiber core, reflecting a portion of the optical signal, delivering the reflected portion of the optical signal to a second optical fiber core via crosstalk between the first optical fiber core and the second optical fiber core, detecting the crosstalk in the reflected portion of the optical signal to generate detection data, determining the performance of the optical transmission system based on the detection data, and identifying a location of a fault in the optical transmission system in response to determining that the optical transmission system is not performing properly. [Brief explanation of the drawings]

[0007] Aspects of the present disclosure are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, according to standard industry practice, various features have not been drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of illustration. [Figure 1] 1 is a flowchart of a method of using an optical transmission system, according to some embodiments. [Figure 2A] 1 is a schematic diagram of an optical transmission system according to some embodiments. [Figure 2B] 1 is a graph of the output of a detector in an optical transmission system according to some embodiments. [Figure 3A] 1 is a schematic diagram of an optical transmission system according to some embodiments. [Figure 3B] 1 is a graph of the output of a detector in an optical transmission system according to some embodiments. [Figure 4] 1 is a schematic diagram of a fan-in fan-out (FIFO) device according to some embodiments. [Figure 5A] 1 is a schematic diagram of an optical transmission system according to some embodiments. [Figure 5B] 1 is a graph of the output of a detector in an optical transmission system according to some embodiments. [Figure 6A] 1 is a schematic diagram of an optical transmission system according to some embodiments. [Figure 6B] 1 is a graph of the output of a detector in an optical transmission system according to some embodiments. [Figure 7] FIG. 1 is a block diagram of a controller usable in an optical transmission system, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. To simplify the disclosure, specific examples of components, values, operations, materials, arrangements, etc. are described below. Of course, these are merely examples and are not intended to be limiting. Other components, values, operations, materials, arrangements, etc. are contemplated. For example, the formation of a first feature above or on a second feature in the following description may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which an additional feature may be formed between the first and second features such that the first and second features are not in direct contact. Furthermore, the disclosure may repeat reference numerals and / or letters in various examples. This repetition is for simplicity and clarity and does not, in itself, dictate a relationship between the various embodiments and / or configurations described.

[0009] Additionally, spatially relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein for ease of description to describe the relationship of one element or feature to another, as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be oriented otherwise (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be similarly interpreted accordingly.

[0010] Optical transmission systems are often used in difficult-to-access locations, such as underground or subsea locations, to repair or replace optical transmission system components. Because the ability to access portions of the optical transmission system is reduced, minimizing the number of components within the optical transmission system helps reduce operational costs while also reducing signal degradation associated with unsuccessful repair or replacement of a failed component within the optical transmission system. Furthermore, minimizing the number of components in an optical transmission system helps reduce the overall footprint of the optical transmission system and reduces initial installation costs.

[0011] To help reduce components such as circuits in optical transmission systems, the present description utilizes core-to-core crosstalk to monitor the performance of the optical transmission system. Crosstalk is the transmission of a portion of an optical signal in one core of an optical fiber to another core in the optical fiber. When an optical fiber includes multiple optical fiber cores, some degree of crosstalk is unavoidable. In some embodiments, crosstalk is enhanced using a fan-in-fan-out (FIFO) device.

[0012] In some embodiments, the present description utilizes backward crosstalk to monitor the performance of an optical system. Backward crosstalk is the reflection of a portion of an optical signal back to the source of the optical signal, where this reflected portion is transmitted to another optical fiber core within the optical fiber. In some embodiments, the reflection is the result of Rayleigh scattering of the optical signal as it propagates along the optical fiber core. In some embodiments, the reflection is the result of a grating introduced into the optical fiber core to cause reflection of a portion of the optical signal.

[0013] Utilizing crosstalk signals to monitor the performance of an optical transmission system reduces the number of components in the optical transmission system. The use of crosstalk signals also helps minimize or eliminate circuits in the optical transmission system. Due to the difficulty of accessing underground or undersea portions of an optical transmission system, the costs associated with repairing or replacing portions of an optical transmission system are significant. Reducing the number of components, particularly circuits, in an optical transmission system helps reduce the costs associated with repairing or replacing components in an optical transmission system. Reducing the number of components also reduces the number of potential points of failure in the optical transmission system, which helps minimize or reduce degradation of the optical signal transmitted by the optical transmission system when a component fails or begins to fail. Additionally, reducing the number of components reduces the overall size of the optical transmission system, reducing installation and manufacturing costs.

[0014] FIG. 1 is a flowchart of a method 100 for using an optical transmission system, according to some embodiments. The method 100 can be used in optical transmission systems installed in various locations, such as underground, along the seabed, or other suitable locations. The method 100 is configured to use crosstalk between cores in optical fibers to determine whether the optical transmission system is operating properly and to generate instructions to repair the optical transmission system in situations where the optical transmission system is not operating properly. The method 100 can be used in optical transmission systems including single-core fibers (SCFs) and multi-core fibers (MCFs). The method 100 can be used in optical transmission systems utilizing Rayleigh scattering, gratings, or other suitable reflective devices. The method 100 can be used in optical transmission systems that include fan-in-fan-out (FIFO) devices and optical transmission systems that do not include FIFO devices.

[0015] In operation 105, an optical signal is transmitted along a first optical fiber core of an optical transmission system. In some embodiments, the first optical fiber core is in an SCF. In some embodiments, the first optical fiber core is in an MCF. In some embodiments, a transmitter converts an electrical signal to an optical signal. In some embodiments, the optical signal is usable to deliver data along the optical fiber core. In some embodiments, the optical signal comprises a pulsed signal. In some embodiments, the optical signal comprises random pulses. In some embodiments, the optical signal is transmitted from a transmitter that does not include a detector. In some embodiments, the optical signal is transmitted from a transmitter that includes a detector.

[0016] In operation 110, a portion of the transmitted signal is reflected. This portion is less than the entire signal propagating along the optical fiber core. In some embodiments, this portion represents between about 5% and about 20% of the intensity of the signal propagating along the optical fiber core. In some embodiments, this portion represents about 10% of the intensity of the signal propagating along the optical fiber core. In some embodiments, the reflection is the result of Rayleigh scattering within the optical fiber core. In some embodiments, if the reflection is the result of Rayleigh scattering, this portion is about 0.05%. In some embodiments, the reflection is the result of the signal propagating through a FIFO device. In some embodiments, the reflection is the result of the signal encountering a grating, such as a Bragg grating, within the optical fiber core.

[0017] In operation 115, the reflected portion of the signal is transmitted to a second optical fiber core within the optical transmission system. The second optical fiber core is different from the first optical fiber core. The second optical fiber core is part of the same optical fiber as the first optical fiber core. In some embodiments, the second optical fiber core is within an SCF. In some embodiments, the second optical fiber core is within an MCF. In some embodiments, the second optical fiber core is adjacent to the first optical fiber core. In some embodiments, the second optical fiber core is in physical contact with the first optical fiber core. In some embodiments, the transmission of the reflected portion is a result of crosstalk between the first and second optical fiber cores. In some embodiments, the transmission is a result of the reflected portion passing through a FIFO device.

[0018] In operation 120, the reflected portion of the signal from the second optical fiber core is detected. A detector converts the detected reflected portion of the signal into an electrical signal for processing and analysis. In some embodiments, the reflected portion is detected using a detector integrated into the same device as the transmitter. In some embodiments, the reflected portion is detected using a detector separate from the transmitter.

[0019] In operation 125, the detected reflected portion of the signal is analyzed to determine the status of the optical transmission system. Analysis of the intensity of the reflected portion of the signal over time can be used to determine whether the optical transmission system is performing within design specification tolerances. Analysis of the intensity of the reflected portion can also be used to identify potential locations of faults within the optical transmission system. By comparing the time of detection of the intensity peak of the reflected portion to the time since the optical signal was initially transmitted into the first optical fiber core, it can be determined how far the optical signal has traveled along the optical transmission system. The distance traveled can be used to identify the location of potential faults within the optical transmission system. In some embodiments, optical time domain reflectometry (OTDR) is used to identify the location of potential faults. In some embodiments, coherent OTDR (COTDR) is used to identify the location of potential faults. In some embodiments, the detected reflected portion of the signal is used to generate a graph for analysis of the status of the optical transmission system. In some embodiments, the analysis is performed using a controller to automatically identify potential faults in the optical transmission system. In some embodiments, the controller uses a trained neural network (NN) to analyze the detected reflected portion of the signal to determine the status of the optical transmission system. In some embodiments, the controller is configured to automatically generate a notification to an operator of the optical transmission system in response to detecting a potential fault in the optical transmission system. In some embodiments, the notification includes an audio or visual notification to the operator. In some embodiments, the notification is transmitted to a terminal device accessible to the operator using a wireless or wired connection. In some embodiments, the notification includes information related to recommendations for addressing the potential fault in the optical transmission system. In some embodiments, the controller is configured to receive instructions from the operator for further analysis of the detected reflected portion of the signal.In some embodiments, the additional analysis includes a review of historical data, a review of environmental factors surrounding the optical transmission system, a review of repair options for the optical transmission system, or other suitable analysis.

[0020] In operation 130, a determination is made as to whether the optical transmission system is functioning properly. Functioning properly means operating within the error tolerance of the optical transmission system. The determination of proper functioning is made based on an analysis of the intensity of the reflected portion of the detected signal. In some embodiments, a threshold is used to determine whether an anomaly in the detected reflected portion of the signal is likely to be a fault in the optical transmission system. In some embodiments, the identification of the potential fault is transmitted via a wireless or wired connection to an operator of the optical transmission system for verification before completing a determination of non-functioning. In some embodiments, the determination of non-functioning is made automatically without verification from the operator of the optical transmission system.

[0021] In response to determining that the optical transmission system is functioning properly, method 100 returns to operation 105 and continues transmitting the optical signal and monitoring the performance of the optical transmission system. In response to determining that the optical transmission system is not functioning properly, method 100 proceeds to operation 135. In some embodiments, if the optical transmission system is not functioning properly by less than a second threshold of variance from expected operation, method 100 both proceeds to operation 135 and returns to operation 105, allowing the optical transmission system to continue operating while the fault is repaired or corrected. Utilizing the second threshold helps avoid situations where the optical transmission system is prevented from continuing to operate with reduced accuracy or precision while still being usable.

[0022] In operation 135, repair instructions are generated to repair the optical transmission system. The repair instructions include information related to a recommendation on how to resolve or mitigate one or more faults determined to affect performance of the optical transmission system. In some embodiments, operation 135 is performed using the same controller as at least one of operation 125 or operation 130. In some embodiments, operation 135 is performed using a different controller than that used in both operation 125 and operation 130. In some embodiments, the repair instructions include respective locations of the one or more faults. In some embodiments, the repair instructions include a recommendation on whether a component of the optical transmission system should be repaired or replaced. In some embodiments, the repair instructions are transmitted to an operator of the optical transmission system via a wireless or wired connection for verification before transmitting the repair instructions to a repair technician. In some embodiments, the repair instructions are transmitted to a repair technician without verification by the operator. In some embodiments, verification by the operator is required based on the type of repair recommended by the repair instruction. For example, in some embodiments, where the type of repair includes a restart or reboot of a component of the optical transmission system, the repair instruction is transmitted without verification to a repair technician or directly to the component of the optical transmission system to be restarted or rebooted. In some embodiments where the type of repair involves physical interaction with the optical transmission system, for example, by repairing or replacing a component, the repair instruction is verified prior to transmitting the repair instruction to a repair technician.

[0023] Those skilled in the art will recognize that modifications of method 100 are within the scope of this description. In some embodiments, at least one operation of method 100 is omitted. For example, in some embodiments, operation 135 is omitted, and an operator determines a type of repair for the optical transmission system in response to the identified fault. In some embodiments, at least one additional operation is included in method 100. For example, in some embodiments, in response to identifying a potential fault, the optical transmission system transmits a probe signal to further diagnose the potential fault. In some embodiments, the order of the operations of method 100 is changed. For example, in some embodiments, operation 115 is performed before operation 110. In optical transmission systems that include FIFO devices, the FIFO devices may induce crosstalk between optical fiber cores. As a result, crosstalk induced by the FIFO devices may occur before the reflection of a portion of the optical signal.

[0024] The method 100 can be used to monitor the performance of an optical transmission system. Compared to other approaches, the optical transmission system can avoid introducing additional components, such as optical circuitry for returning reflected portions of the optical signal to a detector. As a result, the complexity of the optical transmission system is reduced compared to other approaches. Furthermore, the number of potential points of failure in the optical transmission system is reduced, and the costs for repairing and installing the optical transmission system are reduced compared to other approaches.

[0025] 2A is a schematic diagram of an optical transmission system 200 according to some embodiments. In some embodiments, the optical transmission system 200 is usable to perform method 100 (FIG. 1). In some embodiments, the optical transmission system 200 is usable to perform methods other than method 100. The optical transmission system 200 includes a transceiver 205 configured to transmit an optical signal along an optical fiber 210 and to receive a reflected signal from the optical fiber 210. The optical transmission system 200 further includes a plurality of repeaters 215 spaced along the optical fiber 210 to increase the strength of the optical signal. The optical transmission system 200 further includes a transceiver 225 at an end of the optical fiber 210 opposite the transceiver 205. In some embodiments, the transceiver 225 has the same or similar structure as the transceiver 205. In some embodiments, at least one of the transceiver 205 or the transceiver 225 is configured to communicate with a controller, such as controller 700 (FIG. 7), for analyzing the performance of the optical transmission system 200. For simplicity, the direction of propagation from transceiver 205 to transceiver 225 will be referred to as the forward direction, and the direction of propagation from transceiver 225 to transceiver 205 will be referred to as the reverse direction. Those skilled in the art will understand that this description applies to either transceiver 205 or transceiver 225, whichever is the source of the optical signal, and that the above directions are used merely for clarity of explanation.

[0026] Transceiver 205 includes a transmitter configured to output an optical signal received by optical fiber 210. The transmitter is configured to convert an electrical signal to an optical signal. In some embodiments, the optical signal is a pulsed signal. In some embodiments, the transmitter is configured to perform operation 105 of method 100 (FIG. 1). Transceiver 205 further includes a detector configured to receive a reflected portion of the optical signal from optical fiber 210. The detector is configured to convert the received reflected portion of the optical signal to an electrical signal. In some embodiments, the detector is configured to perform operation 120 of method 100 (FIG. 1). Transceiver 205 is configured to provide the electrical signal from the detector to a controller, such as controller 700 (FIG. 7), to analyze performance of optical transmission system 200. In some embodiments, the controller is integrated into transceiver 205. In some embodiments, the controller is separate from transceiver 205.

[0027] Optical fiber 210 is configured to deliver an optical signal from transceiver 205 to transceiver 225. Optical fiber 210 includes multiple optical fiber cores housed within optical fiber 210. In some embodiments, optical fiber 210 includes two optical fiber cores. In some embodiments, the optical fiber includes three or more optical fiber cores. In some embodiments, optical fiber 210 includes an SCF optical fiber core. In some embodiments, optical fiber 210 includes an MCF optical fiber core. The optical fiber cores within optical fiber 210 are in close proximity to one another, allowing for crosstalk between the optical fiber cores. In some embodiments, at least two of the optical fiber cores within optical fiber 210 are in direct physical contact.

[0028] The optical transmission system 200 further includes repeaters 215 spaced along the optical fiber 210. The repeaters 215 are configured to increase the strength of the optical signals propagating along the optical fiber 210. As the optical signals propagate along the optical fiber 210, the strength of the optical signals decreases due to reflections, crosstalk, scattering, or other interactions that reduce the strength of the optical signals. If the strength of the optical signals is too low when the optical signals reach the transceiver 225, the transceiver 225 will have difficulty accurately converting the optical signals into electrical signals. The repeaters 215 are configured to increase the strength of the optical signals toward the initial strength of the optical signals so that, upon reaching the transceiver 225, the transceiver 225 can reliably detect the optical signals and convert them into usable electrical signals.

[0029] The repeater 215 includes multiple optical amplifiers 220a, 220b. In some embodiments, each of the optical amplifiers 220a and 220b includes an erbium-doped fiber (EDF). In some embodiments, each of the optical amplifiers 220a and 220b includes a multi-core EDF when the first optical fiber core 212 and the second optical fiber core 214 are MCFs. In some embodiments, each of the optical amplifiers 220a and 220b includes a single-core EDF when the first optical fiber core 212 and the second optical fiber core 214 are SCFs. The repeater 215 of FIG. 2A includes one optical amplifier 220a for forward propagation and one optical amplifier 220b for backward propagation. Those skilled in the art will recognize that additional optical amplifiers are within the scope of this description.

[0030] Optical transmission system 200 further includes a transceiver 225. Transceiver 225 is configured to receive the optical signal output by transceiver 205. In some embodiments, transceiver 225 includes the same or similar structure as transceiver 205.

[0031] 2A includes enlarged portions of optical fiber 210 and repeater 215. These enlarged portions provide additional details of optical fiber 210 and repeater 215 to aid in understanding the present description. Optical fiber 210 includes a first optical fiber core 212 configured to carry an optical signal during forward propagation. Optical fiber 210 includes a second optical fiber core 214 configured to carry an optical signal during backward propagation. Those skilled in the art will understand that more than two optical fiber cores in optical fiber 210 are contemplated by the present description. Optical amplifier 220a is connected to first optical fiber core 212 to increase the strength of the optical signal as it propagates along first optical fiber core 212. Optical amplifier 220b is connected to second optical fiber core 214 to increase the strength of the optical signal as it propagates along second optical fiber core 214.

[0032] During operation of the optical transmission system 200, a portion of the optical signal propagating along the first optical fiber core 212 is reflected back toward the transceiver 205. In some cases, this reflection is the result of Rayleigh scattering. In some embodiments, this reflection is the result of the optical signal encountering an interface between the first optical fiber core 212 and the optical amplifier 220a. The reflected portion of the optical signal is conceptually illustrated in FIG. 2A by an arrow indicating a change in direction but remaining within the first optical fiber core 212.

[0033] Furthermore, during operation of the optical transmission system 200, a portion of the reflected optical signal propagating backward through the first optical fiber core 212 is transferred to the second optical fiber core 214 due to crosstalk. Crosstalk occurs between the first optical fiber core 212 and the second optical fiber core 214 due to the proximity of the optical fiber cores and optical coupling between the optical fiber cores. The crosstalk portion of the optical fiber cores is conceptually illustrated in Figure 2A by the arrows exiting the first optical fiber core 212 and entering the second optical fiber core 214.

[0034] A detector within transceiver 205 is configured to detect the crosstalk portion of the reflected optical signal from second optical fiber core 214. Analyzing the output of the detection of the crosstalk portion of the reflected optical signal helps determine the performance of optical transmission system 200. In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed as described above with respect to method 100 (FIG. 1). In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed using a method other than method 100 (FIG. 1).

[0035] FIG. 2B is a graph 250 of the output of a detector in an optical transmission system, according to some embodiments. Graph 250 includes a plot 255 of the intensity of the crosstalk portion of the reflected optical signal versus distance from the transceiver 205 of the optical transmission system 200. Plot 255 shows a spike in intensity followed by a drop in intensity until the next spike in intensity. The spike indicates the position of the repeater 215 along the optical fiber 210. The drop in intensity shows how the intensity of the optical signal drops as it propagates along the optical fiber 210 between the repeaters 215. Plot 255 illustrates the design performance of the optical transmission system 200. Plot 255 includes peaks with consistent heights that indicate adequate performance of the repeaters 215. Plot 255 further includes a steady drop in intensity between the repeaters 215, indicating the expected power loss due to propagation of the optical signal along the optical fiber 210.

[0036] Graph 250 further includes a potential fault plot 260, which is a sudden drop in intensity that indicates a potential fault within optical transmission system 200. This sudden drop in intensity indicates a possible break in optical fiber 210. Graph 250 can be used to identify the presence of a potential fault and its location as a distance from transceiver 205. Other potential faults that can be identified using graph 250 include repeater faults, where the intensity peaks have a lower amplitude or the peaks have a u- or n-shape, indicating that the intensity change occurs over a longer distance.

[0037] By analyzing the data in graph 250, both the type and location of potential faults can be identified. In some embodiments, a controller, such as controller 700 (FIG. 7), can then generate recommendations for resolving the potential faults, as described above with respect to method 100 (FIG. 1).

[0038] The optical transmission system 200 can detect the performance of the optical transmission system 200 without including components such as optical circuits or FIFO devices. Furthermore, being able to determine not only the presence of a fault but also the type of fault along with the location of the fault helps determine what repairs, if any, can be performed to improve the performance of the optical transmission system 200. This helps reduce the complexity of the optical transmission system 200 compared to other approaches, as well as the cost of installing and maintaining the optical transmission system 200 compared to other approaches.

[0039] 2A includes optical transmission system 200 transmitting optical signals between two transceivers 205 and 225, those skilled in the art will understand that optical transmission system 200 may include additional components in some embodiments, including features such as gratings, multiplexers, optical couplers, or other suitable components, or components that direct the optical signals to their intended locations throughout the optical transmission network.

[0040] 3A is a schematic diagram of an optical transmission system 300 according to some embodiments. In some embodiments, the optical transmission system 300 is usable to perform method 100 (FIG. 1). In some embodiments, the optical transmission system 300 is usable to perform methods other than method 100. The optical transmission system 300 includes a transceiver 305 configured to transmit an optical signal along an optical fiber 210 and to receive a reflected signal from the optical fiber 210. In some embodiments, the optical fiber 210 is an MCF. The optical transmission system 300 further includes a plurality of repeaters 315 spaced along the optical fiber 210 to increase the strength of the optical signal. The optical transmission system 300 further includes a transceiver 325 at an end of the optical fiber 210 opposite the transceiver 305. In some embodiments, the transceiver 325 has the same or a similar structure as the transceiver 305. In some embodiments, at least one of transceiver 305 or transceiver 325 is configured to communicate with a controller, such as controller 700 (FIG. 7), for analyzing performance of optical transmission system 300. For simplicity, the propagation direction from transceiver 305 to transceiver 325 is referred to as the forward direction, and the propagation direction from transceiver 325 to transceiver 305 is referred to as the reverse direction. Those skilled in the art will understand that this description applies to either transceiver 305 or transceiver 325, whichever is the source of the optical signal, and that the above directions are used merely for clarity of explanation.

[0041] Transceiver 305 is similar to transceiver 205 (FIG. 2A) and will not be described in detail for the sake of brevity. Optical fiber 210 is similar to optical fiber 210 (FIG. 2A) and will not be described in detail for the sake of brevity.

[0042] The optical transmission system 300 further includes repeaters 315 spaced along the optical fiber 210. The repeaters 315 are configured to increase the power of the optical signals propagating along the optical fiber 210. Compared to the repeater 215 (FIG. 2A), the repeater 315 includes a FIFO device 330 at the interface between the repeater 315 and the optical fiber 210. Details of the FIFO device 330 are described below in FIG. 4, according to some embodiments. The FIFO device 330 serves to connect the MCF of the optical fiber 210 to the single-core EDF of the repeater 315. By including the FIFO devices 330 on both sides of the repeater 315, the optical signals are transitioned from the MCF of the optical fiber 210 to the single-core EDF of the repeater 315 for both forward and backward propagation.

[0043] Repeater 315 includes multiple optical amplifiers 320a, 320b. Optical amplifiers 320a and 320b are similar to optical amplifiers 220a and 220b (FIG. 2A) and will not be described in detail for the sake of brevity. Repeater 315 of FIG. 3A includes one optical amplifier 320a for forward propagation and one optical amplifier 320b for backward propagation. Those skilled in the art will recognize that additional optical amplifiers are within the scope of this description.

[0044] The optical transmission system 300 further includes a transceiver 325. The transceiver 325 is configured to receive the optical signal output by the transceiver 305. In some embodiments, the transceiver 325 includes the same or similar structure as the transceiver 305.

[0045] FIG. 3A includes enlarged portions of optical fiber 210 and repeater 315. These enlarged portions provide additional details of optical fiber 210 and repeater 315 to aid in understanding the present description. Optical fiber 210 includes a first optical fiber core 212 configured to carry an optical signal during forward propagation. Optical fiber 210 includes a second optical fiber core 214 configured to carry an optical signal during backward propagation. Those skilled in the art will understand that more than two optical fiber cores in optical fiber 210 are contemplated by the present description. Optical amplifier 320a is connected to first optical fiber core 212 to increase the strength of the optical signal as it propagates along first optical fiber core 212. Optical amplifier 320b is connected to second optical fiber core 214 to increase the strength of the optical signal as it propagates along second optical fiber core 214. FIFO device 330 can be used to optically connect first optical fiber core 212 to optical amplifier 320a and second optical fiber core 214 to optical amplifier 320b.

[0046] During operation of the optical transmission system 300, a portion of the optical signal propagating along the first optical fiber core 212 is reflected back toward the transceiver 305. In some cases, this reflection is the result of Rayleigh scattering. In some embodiments, this reflection is the result of the optical signal encountering an interface between the first optical fiber core 212 and the optical amplifier 320a. In some embodiments, this reflection is the result of the optical signal encountering an interface between the first optical fiber core 212 and the FIFO device 330. The reflected portion of the optical signal is conceptually illustrated in FIG. 3A by an arrow indicating a change in direction but remaining within the first optical fiber core 212.

[0047] Furthermore, during operation of the optical transmission system 300, a portion of the reflected optical signal propagating backward through the first optical fiber core 212 is transferred to the second optical fiber core 214 due to crosstalk. Crosstalk occurs between the first optical fiber core 212 and the second optical fiber core 214 due to the proximity of the optical fiber cores and optical coupling between the optical fiber cores. The crosstalk portion of the optical fiber cores is conceptually illustrated in FIG. 3A by the arrows exiting the first optical fiber core 212 and entering the second optical fiber core 214. Furthermore, in some cases, crosstalk is introduced by the FIFO device 330 at the interface between the FIFO device 330 and the optical fiber 210.

[0048] A detector within the transceiver 305 is configured to detect the crosstalk portion of the reflected optical signal from the second optical fiber core 214. Analyzing the output of the detection of the crosstalk portion of the reflected optical signal helps determine the performance of the optical transmission system 300. In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed as described above with respect to method 100 (FIG. 1). In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed using a method other than method 100 (FIG. 1).

[0049] 3B is a graph 350 of the output of a detector in an optical transmission system, according to some embodiments. Graph 350 includes a plot 355 of the intensity of the crosstalk portion of the reflected optical signal versus distance from transceiver 305 of optical transmission system 300. Graph 350 further includes a potential fault plot 360. Analysis of graph 350 is similar to that of graph 250 (FIG. 2B) and will not be described in detail for the sake of brevity.

[0050] The optical transmission system 300 can detect the performance of the optical transmission system 300 without including components such as optical circuits. Furthermore, being able to determine not only the presence of a fault but also the type of fault along with the location of the fault helps determine what repairs, if any, can be performed to improve the performance of the optical transmission system 300. This helps reduce the complexity of the optical transmission system 300 compared to other approaches, as well as the cost of installing and maintaining the optical transmission system 300 compared to other approaches.

[0051] 3A includes optical transmission system 300 transmitting optical signals between two transceivers 305 and 325, those skilled in the art will understand that optical transmission system 300 may include additional components in some embodiments, including features such as gratings, multiplexers, optical couplers, or other suitable components, or components that direct the optical signals to their intended locations throughout the optical transmission network.

[0052] FIG. 4 is a schematic diagram of a fan-in-fan-out (FIFO) device 400 according to some embodiments. The FIFO device 400 is configured to receive a signal from a first optical fiber core 405 and transmit the optical signal to a second optical fiber core 420. The FIFO device 400 is further configured to receive an optical signal from a third optical fiber core 425 and transmit the optical signal to a fourth optical fiber core 410. The FIFO device 400 includes a spatial multiplexer or demultiplexer 415. In some embodiments, the spatial multiplexer or demultiplexer 415 is configured to facilitate transitions between SCFs and MCFs for bidirectional optical signal propagation. In some embodiments, the spatial multiplexer or demultiplexer 415 is configured to multiplex or demultiplex optical signals based on the frequency of the optical signals. In some embodiments, the spatial multiplexer or demultiplexer 415 is configured to multiplex or demultiplex optical signals based on time. In some cases, during multiplexing or demultiplexing, the spatial multiplexer or demultiplexer 415 generates crosstalk 430 due to some of the optical signals being directed to an unintended output. The FIFO device 400 can be used in different embodiments of the present description to enable connections between SCF and MCF components of an optical transmission system.

[0053] 5A is a schematic diagram of an optical transmission system 500 according to some embodiments. In some embodiments, the optical transmission system 500 can be used to perform method 100 (FIG. 1). In some embodiments, the optical transmission system 500 can be used to perform methods other than method 100. The optical transmission system 500 includes a transceiver 505 configured to transmit an optical signal along the optical fiber core 312 and to receive a reflected signal from the optical fiber core 314. The optical transmission system 500 further includes a plurality of repeaters 215 spaced along the optical fiber core 312 and the optical fiber core 314 to increase the strength of the optical signal. The optical transmission system 500 further includes a transceiver 525 at an end of the optical fiber 312 opposite the transceiver 505. In some embodiments, the transceiver 525 has the same or a similar structure as the transceiver 505. In some embodiments, at least one of transceiver 505 or transceiver 525 is configured to communicate with a controller, such as controller 700 (FIG. 7), for analyzing performance of optical transmission system 500. For simplicity, the direction of propagation from transceiver 505 to transceiver 525 is referred to as the forward direction, and the direction of propagation from transceiver 525 to transceiver 505 is referred to as the reverse direction. Those skilled in the art will understand that this description applies to either transceiver 505 or transceiver 525, whichever is the source of the optical signal, and that the above directions are used merely for clarity of explanation.

[0054] Transceiver 505 is similar to transceiver 205 (FIG. 2A) and will not be described in detail for the sake of brevity. Optical fiber core 212 and optical fiber core 214 are similar to optical fiber core 210 of optical transmission system 300 (FIG. 3A) and will not be described in detail for the sake of brevity.

[0055] The optical transmission system 500 further includes a repeater 215 spaced along the optical fiber core 312 and the optical fiber core 314. The repeater 215 is described above with respect to the optical transmission system 200 (FIG. 2A). Compared to the optical transmission system 200 (FIG. 2A) and the optical transmission system 300 (FIG. 3A), the optical transmission system 500 includes a FIFO device 330 between the repeater 215 and the optical fiber core 312. The FIFO device 330 is also present between the repeater 215 and the optical fiber core 314. Details of the FIFO device 330 are described above in FIG. 4, according to some embodiments. The FIFO device 330 serves to connect the SCF, i.e., the optical fiber core 312 or the optical fiber core 314, to the multi-core EDF of the repeater 215. By including FIFO devices 330 on either side of repeater 215, optical signals transition from the SCFs of optical fiber cores 312 and 314 to the multi-core EDF of repeater 215 for both forward and backward propagation.

[0056] The optical transmission system 500 further includes a transceiver 525. The transceiver 525 is configured to receive the optical signal output by the transceiver 505. In some embodiments, the transceiver 525 includes the same or similar structure as the transceiver 505.

[0057] FIG. 5A includes enlarged portions of optical fiber cores 312 and 314 and repeater 215. These enlarged portions provide additional details of optical fiber cores 312 and 314 and repeater 215 to aid in understanding the present description. Optical fiber core 312 is configured to carry an optical signal during forward propagation. Optical fiber core 314 is configured to carry an optical signal during backward propagation. Those skilled in the art will understand that more than two optical fiber cores are contemplated by the present description. Optical amplifier 220a is connected to first optical fiber core 312 to increase the strength of the optical signal as it propagates along first optical fiber core 312. Optical amplifier 220b is connected to second optical fiber core 314 to increase the strength of the optical signal as it propagates along second optical fiber core 314. FIFO device 330 can be used to optically connect first optical fiber core 312 to optical amplifier 220a and second optical fiber core 314 to optical amplifier 220b.

[0058] During operation of the optical transmission system 500, a portion of the optical signal propagating along the first optical fiber core 312 is reflected back toward the transceiver 505. In some cases, this reflection is the result of Rayleigh scattering. In some embodiments, this reflection is the result of the optical signal encountering an interface between the first optical fiber core 312 and the optical amplifier 220a. In some embodiments, this reflection is the result of the optical signal encountering an interface between the first optical fiber core 312 and the FIFO device 330. The reflected portion of the optical signal is similar to that described above and is not conceptually shown in FIG. 5A for clarity of the drawing.

[0059] Furthermore, during operation of optical transmission system 500, in some instances, crosstalk is introduced by FIFO device 330 at the interface between FIFO device 330 and optical fiber cores 312 and 314. The crosstalk portion of the optical signal is similar to that described above and is not conceptually shown in FIG. 5A for clarity of the drawing.

[0060] A detector within the transceiver 505 is configured to detect the crosstalk portion of the reflected optical signal from the second optical fiber core 314. Analyzing the output of the detection of the crosstalk portion of the reflected optical signal helps determine the performance of the optical transmission system 500. In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed as described above with respect to method 100 (FIG. 1). In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed using a method other than method 100 (FIG. 1).

[0061] 5B is a graph 550 of the output of a detector in an optical transmission system, according to some embodiments. Graph 500 includes a plot 555 of the intensity of the crosstalk portion of the reflected optical signal versus distance from a transceiver 505 of optical transmission system 500. In comparison to graph 250 (FIG. 2B), plot 555 does not include the drop in intensity between repeaters. Identification of potential faults in optical transmission system 500 is possible based on the peaks of plot 555 being n-shaped or U-shaped. Potential defects can also be identified based on the magnitude of peaks of plot 555 being smaller than other peaks of plot 555.

[0062] The optical transmission system 500 can detect the performance of the optical transmission system 500 without including components such as optical circuits. Furthermore, being able to determine not only the presence of a fault but also the type of fault along with the location of the fault helps determine what, if any, repairs can be performed to improve the performance of the optical transmission system 500. This helps reduce the complexity of the optical transmission system 500 compared to other approaches, as well as the cost of installing and maintaining the optical transmission system 500 compared to other approaches.

[0063] 5A includes an optical transmission system 500 transmitting optical signals between two transceivers 505 and 525, those skilled in the art will understand that optical transmission system 500 may include additional components in some embodiments, including features such as gratings, multiplexers, optical couplers, or other suitable components, or components that direct the optical signals to their intended locations throughout the optical transmission network.

[0064] 6A is a schematic diagram of an optical transmission system 600 according to some embodiments. In some embodiments, the optical transmission system 600 can be used to perform method 100 (FIG. 1). In some embodiments, the optical transmission system 600 can be used to perform methods other than method 100. The optical transmission system 600 includes a transceiver 205 configured to transmit an optical signal along an optical fiber 210 and to receive a reflected signal from the optical fiber 210. The optical transmission system 600 further includes a plurality of repeaters 215 spaced along the optical fiber 210 to increase the strength of the optical signal. The optical transmission system 600 further includes a transceiver 225 at an end of the optical fiber 210 opposite the transceiver 205. In some embodiments, the transceiver 225 has the same or similar structure as the transceiver 205. In some embodiments, at least one of the transceiver 205 or the transceiver 225 is configured to communicate with a controller, such as controller 700 (FIG. 7), for analyzing the performance of the optical transmission system 600. For simplicity, the direction of propagation from transceiver 205 to transceiver 225 will be referred to as the forward direction, and the direction of propagation from transceiver 225 to transceiver 205 will be referred to as the reverse direction. Those skilled in the art will understand that this description applies to either transceiver 205 or transceiver 225, whichever is the source of the optical signal, and that the above directions are used merely for clarity of explanation.

[0065] Transceiver 205 is described above with respect to optical transmission system 200 (FIG. 2A). Optical fiber 210 is described above with respect to optical transmission system 200 (FIG. 2A). Repeater 215 is described above with respect to optical transmission system 200 (FIG. 2A). Transceiver 225 is described above with respect to optical transmission system 200 (FIG. 2A).

[0066] Compared to optical transmission system 200 (FIG. 2A), optical transmission system 600 includes grating 630. In some embodiments, grating 630 is in first optical fiber core 212. In some embodiments, grating 630 is in second optical fiber core 214. In some embodiments, grating 630 is in both first optical fiber core 212 and second optical fiber core 214. FIG. 6A includes grating 630 at a single location along optical fiber 210. In some embodiments, grating 630 is positioned at various locations along optical fiber 210, in any of the optical fiber cores within optical fiber 210.

[0067] FIG. 6A includes multiple enlarged sections of optical fiber 210 and repeater 215. These enlarged sections provide additional details of optical fiber 210 and repeater 215 to aid in understanding the present description. Optical fiber 210 includes a first optical fiber core 212 configured to carry an optical signal during forward propagation. Optical fiber 210 includes a second optical fiber core 214 configured to carry an optical signal during backward propagation. Those skilled in the art will understand that more than two optical fiber cores in optical fiber 210 are contemplated by the present description. Optical amplifier 220a is connected to first optical fiber core 212 to increase the intensity of the optical signal as it propagates along first optical fiber core 212. Optical amplifier 220b is connected to second optical fiber core 214 to increase the intensity of the optical signal as it propagates along second optical fiber core 214. The enlarged sections include example locations of grating 630. Those skilled in the art will understand that these locations are merely examples and that other locations and additional gratings 630 are within the scope of the present description.

[0068] During operation of the optical transmission system 600, a portion of the optical signal propagating along the first optical fiber core 212 is reflected back to the transceiver 205. In some cases, this reflection is the result of Rayleigh scattering. In some embodiments, this reflection is the result of the optical signal encountering an interface between the first optical fiber core 212 and the optical amplifier 220a. In some embodiments, this reflection is the result of the optical signal encountering the grating 630. The reflected portion of the optical signal is conceptually illustrated in FIG. 6A by the arrows that indicate a change in direction but remain within the first optical fiber core 212. In some embodiments, forward crosstalk occurs as the optical signal propagates along the first optical fiber core 212, and this forward crosstalk is reflected by the grating 630 in the second optical fiber core 214 back to the transceiver 205.

[0069] Furthermore, during operation of the optical transmission system 600, a portion of the reflected optical signal propagating backward through the first optical fiber core 212 is transferred to the second optical fiber core 214 due to crosstalk. Crosstalk occurs between the first optical fiber core 212 and the second optical fiber core 214 due to the proximity of the optical fiber cores and optical coupling between the optical fiber cores. The crosstalk portion of the optical fiber cores is conceptually illustrated in Figure 6A by the arrows exiting the first optical fiber core 212 and entering the second optical fiber core 214.

[0070] A detector within transceiver 205 is configured to detect the crosstalk portion of the reflected optical signal from second optical fiber core 214. Analyzing the output of the detection of the crosstalk portion of the reflected optical signal helps determine the performance of optical transmission system 600. In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed as described above with respect to method 100 (FIG. 1). In some embodiments, the analysis of the crosstalk portion of the reflected optical signal is performed using a method other than method 100 (FIG. 1).

[0071] 6B is a graph 650 of the output of a detector in an optical transmission system, according to some embodiments. Graph 650 includes a plot 655 of the intensity of the crosstalk portion of the reflected optical signal versus distance from transceiver 205 of optical transmission system 600. Graph 650 further includes a potential fault plot 660. Analysis of graph 650 is similar to that of graph 250 (FIG. 2B) and will not be described in detail for the sake of brevity.

[0072] The optical transmission system 600 can detect the performance of the optical transmission system 600 without including components such as optical circuits or FIFO devices. Furthermore, being able to determine not only the presence of a fault but also the type of fault along with the location of the fault helps determine what repairs, if any, can be performed to improve the performance of the optical transmission system 600. This helps reduce the complexity of the optical transmission system 600 compared to other approaches, as well as the cost of installing and maintaining the optical transmission system 600 compared to other approaches.

[0073] 6A includes optical transmission system 600 transmitting optical signals between two transceivers 205 and 225, those skilled in the art will understand that optical transmission system 600 may include additional components in some embodiments, including features such as gratings, multiplexers, optical couplers, or other suitable components, or components that direct the optical signals to their intended locations throughout the optical transmission network.

[0074] Additionally, although optical transmission system 600 includes similar elements to optical transmission system 200 (FIG. 2A), those skilled in the art will recognize that the inclusion of grating 630 or similar structure is also applicable to optical transmission system 300 (FIG. 3A) and optical transmission system 500 (FIG. 5A).

[0075] 7 is a block diagram of a controller 700 usable in an optical transmission system, according to some embodiments. The controller 700 includes a hardware processor 702 and a non-transitory computer-readable storage medium 704 encoded with, i.e., storing, computer program code 706, i.e., a set of executable instructions. The computer-readable storage medium 704 is also encoded with instructions 707 for interfacing with external devices. The processor 702 is electrically coupled to the computer-readable storage medium 704 via a bus 708. The processor 702 is also electrically coupled to an input / output (I / O) interface 710 by the bus 708. A network interface 712 is also electrically connected to the processor 702 via the bus 708. The network interface 712 is connected to a network 714 such that the processor 702 and the computer-readable storage medium 704 can connect to external elements via the network 714. The processor 702 is configured to execute computer program code 706 encoded on the computer-readable storage medium 704 to enable the controller 700 to perform some or all of the operations described in the method 100 (FIG. 1), the optical transmission system 200 (FIG. 2A), the optical transmission system 300 (FIG. 3A), the optical transmission system 500 (FIG. 5A), or the optical transmission system 600 (FIG. 6A).

[0076] In some embodiments, processor 602 is a central processing unit (CPU), a multiprocessor, a distributed processing system, an application specific integrated circuit (ASIC), and / or any suitable processing device.

[0077] In some embodiments, computer-readable storage medium 704 is an electronic, magnetic, optical, electromagnetic, infrared, and / or semiconductor system (or apparatus or device). For example, computer-readable storage medium 704 includes semiconductor or solid-state memory, magnetic tape, removable computer diskette, random access memory (RAM), read-only memory (ROM), rigid magnetic disk, and / or optical disk. In some embodiments using an optical disk, computer-readable storage medium 504 includes a compact disk read-only memory (CD-ROM), compact disk read / write (CD-R / W), and / or digital video disk (DVD).

[0078] In some embodiments, storage medium 704 stores computer program code 706 configured to cause controller 700 to perform some or all of the operations described in method 100 ( FIG. 1 ), optical transmission system 200 ( FIG. 2A ), optical transmission system 300 ( FIG. 3A ), optical transmission system 500 ( FIG. 5A ), or optical transmission system 600 ( FIG. 6A ). In some embodiments, storage medium 704 also stores information used to perform some or all of the operations described in method 100 ( FIG. 1 ), optical transmission system 200 ( FIG. 2A ), optical transmission system 300 ( FIG. 3A ), optical transmission system 500 ( FIG. 5A ), or optical transmission system 600 ( FIG. 6A ), and information used to perform some or all of the operations described in method 100 ( FIG. 1 ), optical transmission system 200 ( FIG. 2A ), optical transmission system 300 ( FIG. 3A ), optical transmission system 500 ( FIG. 5A ), or optical transmission system 600 ( FIG. 6A ). 1, optical transmission system 200 (FIG. 2A), optical transmission system 300 (FIG. 3A), optical transmission system 500 (FIG. 5A), or optical transmission system 600 (FIG. 6A).

[0079] In some embodiments, storage medium 704 stores instructions 707 for interfacing with an external device, such as a terminal device accessible by an operator or repair technician. Instructions 707 enable processor 702 to generate manufacturing instructions readable by the external device to effectively implement some or all of the operations described in method 100 (FIG. 1), optical transmission system 200 (FIG. 2A), optical transmission system 300 (FIG. 3A), optical transmission system 500 (FIG. 5A), or optical transmission system 600 (FIG. 6A).

[0080] Controller 700 includes an I / O interface 710. I / O interface 710 is coupled to external circuitry. In some embodiments, I / O interface 710 includes a keyboard, keypad, mouse, trackball, trackpad, and / or cursor direction keys for communicating information and commands to processor 702.

[0081] The controller 700 also includes a network interface 712 coupled to the processor 702. The network interface 712 enables the controller 700 to communicate with a network 714 to which one or more other computer systems are connected. The network interface 712 includes a wireless network interface, such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA, or a wired network interface, such as ETHERNET, USB, or IEEE-1394. In some embodiments, some or all of the operations described in method 100 ( FIG. 1 ), optical transmission system 200 ( FIG. 2A ), optical transmission system 300 ( FIG. 3A ), optical transmission system 500 ( FIG. 5A ), or optical transmission system 600 ( FIG. 6A ), are implemented in two or more controllers 700, and information, such as position data, thresholds, detector data, and repair instructions, is exchanged between the different controllers 700 via the network 714.

[0082] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0083] (Appendix 1) An optical transmission system, comprising: a transceiver configured to output an optical signal to a first optical fiber core; a repeater connected to the first optical fiber core and configured to increase the intensity of the optical signal; a second optical fiber core adjacent to the first optical fiber core and configured to receive crosstalk from the first optical fiber core and configured to reflect a portion of the crosstalk of the optical signal back to the transceiver; a detector configured to receive the reflected portion of the crosstalk of the optical signal and to receive detection data based on the reflected portion of the crosstalk of the optical signal; receiving information about the detection data; determining whether the optical transmission system is functioning properly based on the detected data; and and determining a location of a fault in the optical transmission system in response to determining that the optical transmission system is not functioning properly. with the configured controller An optical transmission system comprising:

[0084] (Appendix 2) 2. The optical transmission system of claim 1, further comprising a repeater connected to the first optical fiber core and the second optical fiber core, the repeater configured to increase the intensity of the optical signal.

[0085] (Appendix 3) 3. The optical transmission system according to claim 2, wherein the repeater is a multi-core erbium-doped fiber (EDF).

[0086] (Appendix 4) 3. The optical transmission system according to claim 2, wherein the repeater is a single-core erbium-doped fiber (EDF).

[0087] (Appendix 5) 3. The optical transmission system according to claim 1, further comprising a grating in at least one of the first optical fiber core or the second optical fiber core.

[0088] (Appendix 6) 6. The optical transmission system of claim 2, further comprising a fan-in fan-out (FIFO) device between the first optical fiber core and the repeater.

[0089] (Appendix 7) 7. The optical transmission system of claim 2, wherein the interface between the first optical fiber core and the repeater is configured to reflect the portion of the optical signal.

[0090] (Appendix 8) 8. The optical transmission system according to claim 1, wherein the first optical fiber core and the second optical fiber core are within a multi-core fiber (MCF).

[0091] (Appendix 9) 4. The optical transmission system according to claim 3, wherein the first optical fiber core is in a single-core fiber (SCF).

[0092] (Appendix 10) 10. The optical transmission system of claim 1, wherein the intensity of the reflected portion is less than about 20% of the intensity of the optical signal.

[0093] (Appendix 11) 11. The optical transmission system of any one of claims 1 to 10, further comprising a grating within the first optical fiber core, the grating configured to reflect the portion of the optical signal.

[0094] (Appendix 12) 12. The optical transmission system according to any one of claims 1 to 11, wherein the optical transmission system does not include an optical circuit.

[0095] (Appendix 13) 14. The optical transmission system according to any one of appendices 1 to 13, wherein the optical transmission system is a submarine optical transmission system.

[0096] (Appendix 14) 2. The optical transmission system of claim 1, wherein the first optical fiber core is part of a multi-core fiber (MCF) and the repeater is a multi-core erbium-doped fiber (EDF).

[0097] (Appendix 15) 2. The optical transmission system of claim 1, wherein the first optical fiber core is part of an MCF and the repeater is a single-core EDF.

[0098] (Appendix 16) 2. The optical transmission system according to claim 1, wherein the first optical fiber core is a single-core fiber (SCF) and the repeater is a multi-core EDF.

[0099] (Appendix 17) 16. The optical transmission system of any one of appendixes 1, 14, and 15, further comprising a fan-in fan-out (FIFO) device between the first optical fiber core and the repeater.

[0100] (Appendix 18) 17. The optical transmission system of any one of claims 1 and 14 to 16, wherein an interface between the first optical fiber core and the repeater is configured to reflect the portion of the optical signal.

[0101] (Appendix 19) 18. The optical transmission system of any one of appendixes 1 and 14 to 17, further comprising a grating in the first optical fiber core, the grating configured to partially reflect the optical signal.

[0102] (Appendix 20) 19. The optical transmission system of any one of appendixes 1 and 14 to 18, further comprising a grating in the second optical fiber core, the grating configured to reflect the portion of the crosstalk of the optical signal.

[0103] (Appendix 21) 1. A method for determining performance of an optical transmission system, comprising: transmitting an optical signal along a first optical fiber core; reflecting a portion of the optical signal; delivering the reflected portion of the optical signal to a second optical fiber core via crosstalk between the first optical fiber core and the second optical fiber core; detecting the crosstalk in the reflected portion of the optical signal to generate detected data; determining the performance of the optical transmission system based on the detected data; identifying a location of a fault in the optical transmission system in response to determining that the optical transmission system is not performing properly; and A method comprising:

[0104] The foregoing outlines features of some embodiments so that those skilled in the art may better understand aspects of the present disclosure. Those skilled in the art will appreciate that they can readily use this disclosure as a basis for designing or modifying other processes and structures to carry out the same purposes and / or achieve the same advantages as the embodiments introduced herein. Those skilled in the art will also appreciate that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the present disclosure.

[0105] This application claims priority to U.S. Patent Application No. 18 / 616,059, filed March 25, 2024, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0106] 200 Optical Transmission System 205 Transceiver 210 Optical Fiber 212 First optical fiber core 214 Second optical fiber core 215 Repeater 220a Optical Amplifier 220b Optical Amplifier 225 Transceiver 300 Optical Transmission System 305 Transceiver 312 Optical Fiber Core 314 Optical Fiber Core 315 Repeater 320a Optical Amplifier 320b Optical Amplifier 325 Transceiver 330 FIFO Device 400 Fan-in Fan-out (FIFO) devices 405 First optical fiber core 410 Fourth Optical Fiber Core 415 Spatial Multiplexer or Demultiplexer 420 Second optical fiber core 425 Third Optical Fiber Core 500 Optical Transmission System 505 Transceiver 525 transceiver 600 Optical Transmission System 602 processor 630 Grating 700 Controller 702 Hardware Processor 704 Non-transitory computer-readable storage medium 706 Computer Program Code 707 Command 708 Bus 710 Input / Output (I / O) Interface 712 Network Interface 714 Network 716 Position Data Parameters 718 Threshold Parameter 720 detector data parameters 722 Repair Instruction Parameters

Claims

1. An optical transmission system, comprising: a transceiver configured to output an optical signal to a first optical fiber core; a repeater connected to the first optical fiber core and configured to increase the intensity of the optical signal; a second optical fiber core adjacent to the first optical fiber core and configured to receive crosstalk from the first optical fiber core and to reflect a portion of the crosstalk of the optical signal back to the transceiver; a detector configured to receive the reflected portion of the crosstalk of the optical signal and to receive detection data based on the reflected portion of the crosstalk of the optical signal; receiving information about the detection data; determining whether the optical transmission system is functioning properly based on the detected data; and and determining a location of a fault in the optical transmission system in response to determining that the optical transmission system is not functioning properly. with the configured controller An optical transmission system comprising:

2. The optical transmission system of claim 1 , further comprising a repeater connected to the first optical fiber core and the second optical fiber core, the repeater configured to increase the intensity of the optical signal.

3. 3. The optical transmission system according to claim 2, wherein the repeater is a multi-core erbium-doped fiber (EDF).

4. 3. The optical transmission system according to claim 2, wherein the repeater is a single-core erbium-doped fiber (EDF).

5. 3. The optical transmission system according to claim 1, further comprising a grating in at least one of the first optical fiber core and the second optical fiber core.

6. The optical transmission system according to claim 2 , further comprising a fan-in fan-out (FIFO) device between the first optical fiber core and the repeater.

7. 5. An optical transmission system according to claim 2, wherein an interface between the first optical fiber core and the repeater is configured to reflect the portion of the optical signal.

8. The optical transmission system of claim 1 , wherein the first optical fiber core and the second optical fiber core are in a multi-core fiber (MCF).

9. The optical transmission system of claim 3 , wherein the first optical fiber core is in a single-core fiber (SCF).

10. 1. A method for determining performance of an optical transmission system, comprising: transmitting an optical signal along a first optical fiber core; reflecting a portion of the optical signal; delivering the reflected portion of the optical signal to a second optical fiber core via crosstalk between the first optical fiber core and the second optical fiber core; detecting the crosstalk in the reflected portion of the optical signal to generate detected data; determining the performance of the optical transmission system based on the detected data; identifying a location of a fault in the optical transmission system in response to determining that the optical transmission system is not performing properly; and A method comprising:

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