Submarine cable interface for connection to ground terminal

Abstract

The invention relates to a subsea cable interface for connection to a ground terminal. In an optical network having a ground terminal and an open cable interface (OCI) connecting a subsea cable to a ground cable, the OCI may include a filter positioned on an optical path between the ground cable and the subsea cable and configured to communicate a first communication signal having a first frequency band, and filtering the auxiliary signal having a second frequency band that does not overlap the first frequency band. The assistance signal may be looped back to the ground terminal. The terrestrial terminal may detect the looped-back auxiliary signal and, in response, determine the presence of the OCI and determine that the monitoring signal is rerouted by the OCI.

Description

Description of the case

[0001] This application is a divisional application of Chinese invention patent application No. 202111657374.7, with an application date of December 30, 2021. Technical Field

[0002] The present disclosure relates to a submarine cable interface for connecting to a surface terminal. Background Art

[0003] Communications networks include both terrestrial fiber optic cables that carry optical communications signals over land and submarine cables that carry them across large bodies of water between continental blocks. In typical scenarios, signals from terrestrial networks are incompatible with those from submarine networks. Signals from the respective networks may differ in frequency range, modulation format for data channels, and the type and quality of monitoring channels used for system telemetry, control, and operation.

[0004] To interface terrestrial cables with submarine cables to create an interconnected optical network, conventional optical network systems include specialized equipment. This specialized equipment used to facilitate this interface is often referred to as submarine line termination equipment (SLTE). The SLTE generates the signals transmitted across the submarine cable. For example, the SLTE includes components for multiplexing optical wavelengths, adjusting the power level of the optical signal, filtering portions of the optical spectrum, and loading the submarine cable with noise in certain spectral regions.

[0005] However, using specialized and dedicated SLTEs to interface submarine networks with terrestrial networks is expensive and cumbersome. Having to produce specialized terrestrial equipment significantly increases the cost of the overall system compared to simply producing standard terrestrial equipment. Furthermore, while standard terrestrial equipment is cheap and simple to install, SLTEs are expensive to install because they require skilled technicians to manually calibrate the equipment's power levels for proper operation, such as by inserting jumpers or creating offset connectors to increase the desired residual attenuation. Furthermore, the differences between standard terrestrial equipment and SLTEs necessitate assigning different stock keeping units (SKUs) to each type of terminal. This, in turn, requires tracking and managing additional SKUs to maintain the network, adding unnecessary time and cost to the maintenance process. Summary of the Invention

[0006] The present disclosure avoids the need for a specialized SLTE at the interface with the submarine cable. This is achieved by providing an optical cable interface (OCI) between the submarine cable and the standard terrestrial cable, with a filter to filter out signals with frequencies outside the frequency range allowed by the submarine system. The OCI can also be configured to loop the filtered signal back toward the terrestrial cable network, which can be used to indicate the presence of an interface between the terrestrial and submarine optical cables to control circuits in the terrestrial optical network.

[0007] One aspect of the present disclosure relates to an open cable interface (OCI) configured to connect a submarine cable to a terrestrial cable of an optical network, the open cable interface comprising: a first optical path configured to provide a first communication signal from the optical network to the submarine cable; and a second optical path configured to provide a second communication signal from the submarine cable to the optical network, wherein the first communication signal and the second communication signal are within a first frequency band; and a first filter positioned on the first optical path and configured to pass the first communication signal and filter out an auxiliary signal from the terrestrial cable, wherein the auxiliary signal is within the second frequency band that does not overlap with the first frequency band.

[0008] In some examples, the second frequency band may include at least one of 1510 nm or 1610 nm.

[0009] In some examples, the first filter may be a wavelength division multiplexing (WDM) filter.

[0010] In some examples, the auxiliary signal may include an optical supervisory channel signal.

[0011] In some examples, the auxiliary signal may include an optical time domain reflectometer signal.

[0012] In some examples, the OCI may include a second filter positioned on the second optical path and configured to pass a second communication signal from the submarine cable to the surface cable, and the first filter and the second filter may be configured to loop back an auxiliary signal received from the surface cable to the surface cable.

[0013] In some examples, the OCI may include a first variable optical attenuator (VOA) positioned on a first optical path between the first filter and the submarine cable and configured to adjust the power level of the first communication signal without affecting the power level of the auxiliary signal.

[0014] In some examples, the OCI may include a second VOA positioned on a second optical path between the second filter and the submarine cable.

[0015] In some examples, the OCI can be configured to connect to terrestrial transmission equipment that has the same stock keeping unit (SKU) as other equipment included in the optical network that does not interface with the submarine cable.

[0016] In some examples, the terrestrial cable can have the same SKU as other terrestrial cables included in the optical network.

[0017] Another aspect of the present disclosure relates to a system comprising: one or more processors; and a memory in communication with the one or more processors and containing instructions configured to cause the one or more processors to: transmit a monitoring signal from a terminal of a terrestrial fiber optic cable of a terrestrial network; detect the monitoring signal reflected back to the terminal; and, in response to detecting that the monitoring signal is reflected back to the terminal, determine that the monitoring signal is rerouted by the fiber optic cable interface to a submarine cable.

[0018] In some examples, the instructions may also be configured to cause the one or more processors to initiate a power reduction procedure in response to determining that the monitoring signal is rerouted by the optical cable interface to the submarine cable, the power reduction procedure configured to maintain a transmission power level to the submarine cable at or below a predetermined power level.

[0019] In some examples, the instructions may also be configured to cause the one or more processors to: monitor a power level of a communication signal passing through a WDM filter of the OCI; and in response to determining that the monitoring signal is being rerouted by the optical cable interface to the submarine cable, adjust the power level of the communication signal to be equal to or below a predetermined submarine cable power level.

[0020] In some examples, the instructions may also be configured to cause one or more processors, in response to determining that the monitoring signal is rerouted by the optical cable interface to the submarine cable: set the travel distance of the monitoring signal from the terminal to the optical cable interface and back to the first terminal to be twice the distance between the terminal and the optical cable interface; and evaluate the travel time of the monitoring signal transmitted from the terminal to the optical cable interface based on the set travel distance.

[0021] In some examples, the instructions may also be configured to cause the one or more processors, in response to determining that the monitoring signal is rerouted by the optical cable interface to the submarine cable: determine a loss of the monitoring signal transmitted from the terminal to the OCI and back to the first terminal; and estimate the actual loss of the monitoring signal transmitted from the terminal to the OCI to be half of the determined loss.

[0022] Another aspect of the present disclosure relates to an optical network comprising: a plurality of terrestrial optical cable terminals, including a first terrestrial optical cable terminal that interfaces the optical cable to a submarine cable and a second terrestrial optical cable terminal that does not interface the optical cable to the submarine cable; and a system as described in any of the embodiments herein.

[0023] In some examples, the first terrestrial cable terminal and the second terrestrial cable terminal can have a common SKU.

[0024] Another aspect of the present disclosure relates to a method comprising: transmitting, by one or more processors, a monitoring signal from a terminal of a terrestrial fiber optic cable of a terrestrial network; detecting, by the one or more processors, the monitoring signal reflected back to the terminal; and determining, by the one or more processors, in response to detecting that the monitoring signal is reflected back to the terminal, that the monitoring signal is rerouted by a fiber optic cable interface to a submarine cable.

[0025] In some examples, the method may be performed during initialization of a monitoring program for monitoring signals transmitted over a terrestrial network.

[0026] In some examples, the method may further include initiating a submarine cable use case in response to determining that the monitoring signal is rerouted to the submarine cable by the optical cable interface. The submarine cable use case may include one or more of the following: reducing the power level of the communication signal transmitted from the terminal to the OCI to or below a predetermined submarine cable power level; evaluating the travel time of the monitoring signal transmitted from the terminal to the OCI as a round-trip time; or evaluating the loss of the monitoring signal transmitted from the terminal to the OCI as half of the loss measured at the terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of an optical network according to aspects of the present disclosure.

[0028] Figure 2A and Figure 2B is a schematic diagram of an example open cable interface (OCI) according to aspects of the present disclosure.

[0029] Figure 3 is an example block diagram of ground terminal equipment (TE) according to aspects of the present disclosure.

[0030] Figure 4 is a flow diagram of an example routine according to aspects of the present disclosure. DETAILED DESCRIPTION

[0031] The present disclosure generally relates to devices and methods for interfacing terrestrial and submarine optical networks without a dedicated SLTE. Specifically, an optical fiber interconnect (OCI) including a filter is positioned along a first optical communication path from a terrestrial cable to the OCI of a submarine cable. The filter is capable of passing communication signals within a first frequency band within the permitted frequency range of the submarine cable while filtering out other signals, such as monitoring signals, outside the permitted frequency range of the submarine cable.

[0032] In some examples, the OCI can include a second filter positioned along a second optical communication path of the OCI from the submarine cable to the terrestrial cable. The first filter and the second filter may be capable of looping back other filtered signals toward the terrestrial cable network. In the terrestrial cable network, the loopback signals can be detected by standard terminal equipment, and their detection can be interpreted as indicating that an interface exists between the terrestrial cable and the submarine cable. Because the presence of the interface can be detected using the loopback signal, the standard terminal equipment within the terrestrial system can control the power level of the communication signal within the first frequency band based on the detection. Therefore, by including the first filter and the second filter and the loopback path within the OCI, both frequency control and power control using standard terrestrial terminal equipment are enabled.

[0033] In some further examples, the OCI may also include at least one variable optical attenuator (VOA) positioned along the first optical communication path between the first filter and the submarine cable. The VOA may be responsible for adjusting the power level of the communication signal transmitted by the first filter before it is received at the submarine cable. As opposed to positioning the attenuating element on the "ground side" of the first filter within the terrestrial network or within the OCI, using a VOA positioned on the "seaside" of the first filter may help avoid attenuation of other signals looped back to the terrestrial network, especially considering that positioning the attenuating element on the "ground side" of the filter would double attenuate the signal (once along each path) and may make detecting the looped signal more difficult.

[0034] Including the OCI of the present disclosure at the interface between the terrestrial optical network and the submarine optical network avoids the need for a specialized SLTE on the terrestrial side of the interface. This achieves cost reduction due to the relatively low cost of standard terrestrial optical cables compared to SLTE. In addition, no hardware changes to the terrestrial equipment are required. Software updates can be provided to standard terrestrial terminal equipment to detect the location of the terrestrial network interfaced with the submarine cable based on monitoring signals looped back to the standard terrestrial terminal. In addition, when all terrestrial / submarine interfaces in the optical network are equipped with the OCI of the present disclosure, a single SKU can be used for all terminal equipment for the entire network. Example System

[0035] Figure 1 is a schematic diagram of an optical network 100 including a first terrestrial optical network 102 and a second terrestrial optical network 104 connected to each other via a submarine optical network 106. For example, each of the terrestrial optical networks 102, 104 may be located at a landmass A and a landmass B separated by a body of water, such as an ocean S, and the submarine network may be located primarily in ocean S. The respective terrestrial networks of landmasses A, B may be communicatively connected to each other via one or more submarine cables across ocean S.

[0036] Each of the terrestrial optical networks 102, 104 is shown as including at least one respective terminal, including terminal equipment (TE) 112, 114, for receiving and transmitting communication signals over the optical network and for monitoring the operation of the optical network. The terminal equipment 112 of the first terrestrial optical network 102 is connected to a first optical cable 122, while the terminal equipment 114 of the second terrestrial optical network 104 is connected to a second optical cable 124. The first and second optical cables are connected to each other via a submarine optical network 106. Additional terminals and optical cables (not shown) may be included in each optical network.

[0037] The submarine optical network 106 may include one or more submarine optical cables 130 connected at opposite ends to the first terrestrial optical network 102 and the second terrestrial optical network 104, respectively. Figure 1 In the example of FIG, a first end of one or more submarine optical cables 130 is connected to a first optical cable 122 via a first open cable interface (OCI) 132, and an opposite second end of one or more submarine optical cables 130 is connected to a second optical cable 124 via a second OCI 134. In addition, compared to SLTE, each of the terminal equipment 112 and 114 can be a standard terrestrial terminal equipment. To this end, both ends of the one or more submarine optical cables 130 can be connected to the standard terrestrial terminal equipment via corresponding optical cables.

[0038] Each of the OCIs 132 , 134 may be adapted to support compatibility between the cables of the submarine optical network 106 and the cables of the terrestrial optical networks 102 , 104 . Figure 2A is a schematic diagram of an example OCI 230 for interfacing a submarine optical network with a terrestrial optical network using standard terrestrial terminal equipment 212. Figure 2A In the example of FIG, optical cable 214 is shown as including two optical paths: a first optical path originating at point 222, from which terminal equipment 212 is configured to transmit optical signals; and a second optical path terminating at point 224, at which terminal equipment 212 is configured to receive optical signals. The first and second optical paths of optical cable 214 together facilitate bidirectional communication between terminal equipment 212 and OCI 230.

[0039] The optical signals transmitted and received by the terminal equipment 212 may include each of a communication signal and an auxiliary signal. The communication signal may include communication data, such as messages transmitted between end terminals of the optical network. The communication signal may have a first wavelength λ1 within a first frequency band supported by the submarine optical network. Thus, the communication signal can be transmitted between land masses A and B via the submarine optical network. The auxiliary signal may include telemetry signals used to monitor the operation and performance of the terrestrial optical network, such as optical supervisory channel (OSC) signals, optical time domain reflectivity (OTDR) signals, etc. The submarine optical network may not support the auxiliary signal. Therefore, to prevent the auxiliary signal from being transmitted or relayed via the submarine optical network, the auxiliary signal may have a second wavelength λ2 within a second frequency band that does not overlap with the first frequency band. In one example arrangement, the first frequency band may include wavelengths less than 1510 nm, while the second frequency band may include wavelengths between 1510 nm and 1610 nm. In a different example arrangement, the second frequency band may include a wavelength of 1625 nm, such as to support terrestrial OTDR signals.

[0040] Using non-overlapping frequency bands for the communication signal and the auxiliary signal allows the signals to be separated from each other using one or more filtering techniques including, but not limited to, high-pass filtering, low-pass filtering, band-pass filtering, notch filtering, etc. Figure 2A In the example shown, filter 232 is positioned at OCI 230 on the first optical path. Communication signals from the first terrestrial optical network λ1(A) and auxiliary signals from the first terrestrial optical network λ2(A) are transmitted from point 222 toward OCI 230. At the OCI, filter 232 can be a wavelength division multiplexing (WDM) filter and can be configured to pass communication signals λ1(A) and filter out auxiliary signals λ2(A). Consequently, only communication signals λ1(A), which are supported by the submarine optical network, are passed to point 242 and transmitted through the submarine optical network, while unsupported auxiliary signals λ2(A) are prevented from reaching the submarine optical network.

[0041] In another example configuration, also Figure 2A , the second filter 234 is positioned at the OCI 230 on the second optical path, and an optical ring loop 236 is provided between the first filter 232 and the second filter 234. The first filter 232 can be configured to transmit the filtered auxiliary signal λ2(A) to the second filter 234 via the optical ring loop 236, and the second filter can be configured to reflect the auxiliary signal λ2(A) received from the first filter 232 back to the terminal equipment 212 along the second optical path. The reflected or looped auxiliary signal λ2(A) can be transmitted from the OCI 230 along the second optical path.

[0042] Figure 2AAlso shown are communication signals from the second terrestrial network λ1(B) received by OCI 230 at point 244 of the second optical path. These communication signals can have the same wavelength as the communication signals from the first terrestrial optical network λ1(A), or can fall within the same first frequency band. Furthermore, second filter 234 can be configured in the same or similar manner as first filter 232 and, therefore, can be configured to pass the communication signals from the second terrestrial network λ1(B), thereby generating the communication signals and the loopback auxiliary signal λ2(A).

[0043] exist Figure 2A In the example of FIG, power level control can be performed on the ground side of OCI 230, such as at terminal equipment 212, for a communication signal originating from a first terrestrial optical network λ1(A). Adjusting the power level of the signal can involve adding a predetermined attenuation to the signal, and this operation can be performed so that the signal meets the power requirements of the submarine optical network. However, by performing power level control on the ground side of OCI 230, the power level of the auxiliary signal λ2(A) is also affected. Because the auxiliary signal λ2(A) is not routed through the submarine optical network, the power level of the auxiliary signal λ2(A) does not need to be adjusted in the same manner.

[0044] Figure 2B FIG. 1 is a schematic diagram of another example OCI for selective power adjustment of communication signals without affecting auxiliary signals. Figure 2A The example OCI is the same as, Figure 2B The OCI uses standard ground terminal equipment to connect the submarine optical network with the ground optical network. In addition to adding one or more variable optical attenuators (VOAs) along the first and second optical paths, Figure 2B Features and Figure 2A Along the first optical path, first VOA 252 is positioned between first filter 232 and the submarine optical network. First VOA 252 can be configured to adjust the power level of the communication signal from the first terrestrial optical network λ1(A), such as by reducing the power level to meet the power requirements of the submarine optical network. By positioning first VOA 252 on the first optical path after filter 232, first VOA 252 can control the power level of communication signal λ1(A) without affecting the power level of auxiliary signal λ2(A).

[0045] In some examples, the attenuation introduced by first VOA 252 can be a fixed value. For example, the value can be set manually or automatically during installation of OCI 230. A manual method for setting the attenuation value involves a remote operator assigning the value through a network management software interface. An automated method for setting the attenuation value involves assigning the value according to an automated script or software controller. In either method, VOA 252 can include a sensor to monitor the power at VOA 252 by routing a predetermined small portion of the transmitted signal to a photodetector. The measurement results from the photodetector can then be provided to a remote operator or automated program and, in turn, can be used to determine and set the fixed attenuation for VOA 252.

[0046] In other examples, the attenuation introduced by the first VOA 252 can be a variable amount that is continuously adjusted based on feedback from the VOA 252. For example, a local control loop can be provided within the OCI. The local control loop can include a photodetector for sensing the amount of power output by the VOA 252 and a control mechanism, such as a microcontroller, for controlling the VOA 252 in a manner that reduces and minimizes over time the difference between the current power level of the VOA 252 and a preset target power level. In such an example, the preset target power level can be determined and programmed during the installation process.

[0047] In some examples, a second VOA 254 may also be included in OCI 230. Second VOA 254 may be positioned along the second optical path between second filter 234 and the submarine optical network. Second VOA 254 may be configured to control the power level of communication signal λ1(B). For example, second VOA 254 may reduce the power level of communication signal λ1(B) to a preset level suitable for terminal equipment 212. Such power adjustment may be necessary if terminal equipment 212 is located close to OCI 230, meaning that little attenuation occurs from OCI 230 to terminal equipment 212.

[0048] Figure 2A and Figure 2B The two example arrangements allow communication signals to pass to the submarine optical network while blocking the auxiliary signals from passing. The two example arrangements also allow the power level of the communication signals to be controlled before they enter the submarine optical network. The two example arrangements also allow the loopback of the monitoring signal, which has the effect of conveying the presence of the OCI to adjacent terminal equipment included in the terrestrial optical network - such as, Figure 1In the example of the first optical network 102, a TE 112 of the first optical network 102 is provided. For example, if a given terrestrial terminal transmits a monitoring signal to a neighboring node within the optical network, and the monitoring signal is received back at the same given terrestrial terminal, it can be inferred that the monitoring signal is looped back toward the given terrestrial terminal through the optical loopback path of the filter and the OCI, thereby indicating the presence of the OCI and, by extension, the presence of the submarine optical network interfaced to the terrestrial optical network via the OCI. The presence of the transmitted OCI may be beneficial in enabling neighboring terminal equipment to adjust one or more settings to accommodate the nearby interface with the submarine optical network, without requiring specialized and dedicated hardware for the SLTE.

[0049] Figure 3 FIG2 is an example block diagram of a standard ground terminal equipment (TE). A standard ground TE includes one or more computing devices 300 programmed with data and instructions sufficient to transmit monitoring signals and detect when monitoring signals are rerouted or looped back toward their origin. The one or more computing devices 300 may include a processor 310, a memory 320, and one or more communication devices 350 for receiving input and transmitting output.

[0050] Processor 310 may be a well-known processor or other lesser-known processor type. Alternatively, the processor may be a dedicated controller, such as an ASIC.

[0051] The memory 320 can store information accessible by the processor 310, including data that can be retrieved, manipulated, or stored by the processor, instructions that can be executed by the processor, or a combination thereof. The memory can be a type of non-transitory computer-readable medium capable of storing information accessible by the processor, such as a hard drive, solid-state drive, tape drive, optical storage device, memory card, ROM, RAM, DVD, CD-ROM, writable and read-only memory.

[0052] Although Figure 3 Each of the processor 310 and the memory 320 is functionally illustrated as a respective single block, but the processor and memory may actually include multiple processors, multiple memories, or any combination thereof, which may or may not be stored in a common location or within the same physical enclosure. For example, some or all of the data and instructions may be stored on a removable CD-ROM, while others may be stored within a read-only computer chip. Further, for example, some or all of the data and instructions may be stored in a location physically remote from the processor but still accessible to the processor. Similarly, the processor may actually include a collection of processors that may or may not operate in parallel.

[0053] One or more communication devices can facilitate communication between the terminal and other remote terminals and components of the optical network that communicates with the terminal. The remote terminals and components can include ground nodes of a terrestrial optical network and an OCI that connects the terrestrial optical network to one or more submarine optical networks. The communication device can be capable of transmitting data to and from other computers, such as modems (e.g., dial-up, cable, or fiber optic) and wireless interfaces. For example, each node can receive communications via network connection 130, such as through the Internet, the World Wide Web, an intranet, a virtual private network, a wide area network, a local area network, a private network using one or more company-specific communication protocols, Ethernet, WiFi (e.g., 702.71, 702.71b, g, n or other such standards) and RPC, HTTP, and various combinations thereof.

[0054] Memory 320 may include instructions 340 and may also include data 330 that can be retrieved, stored, or modified by processor 310 according to instructions 340. For example, although the computing device 300 disclosed herein is not limited to a particular data structure, data 330 may be stored in a computer register, in a data repository, as a structure having a plurality of different fields and records or files or buffers. Data 330 may also be formatted in a computer-readable format, such as, but not limited to, binary values, ASCII, or Unicode. In addition, data 330 may include information sufficient to identify the relevant information, such as numbers, descriptive text, proprietary codes, indicators, references to data stored in other memories, including other network locations, or information used by a function to calculate the relevant data.

[0055] Instructions 340 may be a set of instructions directly executed by processor 310, such as machine code, or a set of instructions indirectly executed, such as a script. In this regard, the terms "instructions," "steps," and "program" may be used interchangeably herein. Instructions 340 may be stored in an object code format for direct processing by processor 310, or in other types of computer languages, including scripts or sets of independent source code modules that are interpreted on demand or pre-compiled.

[0056] exist Figure 3In the example of FIG, the data 330 stored in the memory 320 may include monitoring signal data 332 indicating information about the remote conditions of the communication signals and one or more optical terminals included in the network. The monitoring signal data 332 may be used to remotely determine whether the nodes and terminals of the network are operating normally. For example, the monitoring signal data 332 may be used to detect losses, delays, or interruptions within the network based on monitoring data, such as feedback from remote nodes, round-trip time, etc. Examples of monitoring signals include, but are not limited to, OSC signals and OTDR signals. The monitoring signal data 332 may also be used to facilitate remote management of the network based on detected problems within the network, such as by resending or rerouting optical signals.

[0057] Data 330 may also include power level data 334, which indicates prescribed power levels for optical signals transmitted to various terminals and nodes included in the network. For example, the power level data may indicate a first power level at which communication signals should be transmitted to adjacent terrestrial terminals, and a second power level, lower than the first power level, at which communication signals should be transmitted to adjacent OCIs.

[0058] Data 330 may also include adjacent terminal status 336 indicating the corresponding status of adjacent nodes of the network. For example, for adjacent terrestrial terminals, the adjacent terminal status of these nodes may indicate that they are terrestrial terminals. Alternatively, for an OCI connected to terminal equipment via an optical cable, the adjacent terminal status of such a node may indicate the presence of an OCI connected to an adjacent submarine optical network.

[0059] Instructions 340 stored in the memory may include a supervisory signal transmission routine 342 for transmitting supervisory signals from remote nodes of the network and collecting supervisory signal data.

[0060] Instructions 340 may also include a terminal status check routine 344 for checking the status of a given terminal, such as an adjacent terminal within the network. For example, terminal status check routine 344 may involve transmitting an optical signal having a wavelength within a given range, the given range corresponding to a wavelength band filtered by a filter of an OCI included in the network. If the transmitted optical signal is then received at the transmitting terminal, it may be determined that the signal was looped back toward the terminal by the OCI, thereby indicating the presence of an interface with an adjacent submarine optical network.

[0061] The instructions 340 may also include a submarine cable use case routine 346 for configuring a use case of the terminal in response to detecting an interface with an adjacent submarine optical network. The submarine cable use case routine 346 may involve changing one or more configurations of the terminal including one or more computing devices 300 so that the terminal adapts to communication with an OCI that interfaces the submarine optical network to the terminal. The configuration may include, but is not limited to, a power level configuration, a monitoring signal evaluation configuration, or any combination thereof. Figure 4 Some example submarine cable use cases are provided. Example Method

[0062] Combine Figure 4 FIG100 further describes an example routine 400 executed by a processor of one or more computing devices of a ground terminal. The routine may include a terminal status check routine, a submarine cable use case routine, etc. It should be understood that the routines described herein are merely examples, and in other examples, certain steps may be added, reduced, replaced, or reordered.

[0063] At block 410, a monitoring signal is transmitted from a first terminal of a terrestrial optical network. The monitoring signal may be transmitted via an optical cable to one or more neighboring nodes of the first terminal. The monitoring signal may be an OSC signal, an OTDR signal, or another signal by which the first terminal can monitor the performance of the optical network.

[0064] At block 420, the first terminal determines whether the monitoring signal has been transmitted back to the first terminal. This may involve receiving a signal at one or more input communication ports of the first terminal, processing the received signal, and identifying one or more of the received signals as being identical to a previously transmitted monitoring signal. If the monitoring signal is not received at the first terminal, such as after a predetermined duration has elapsed, or after receiving an acknowledgment signal indicating that the transmitted monitoring signal was received at another node in the optical network, it may be determined that the monitoring signal has not been transmitted back to the first terminal.

[0065] If it is determined that the monitoring signal was not transmitted back to the first terminal, operations continue at block 430, where the first terminal determines that the monitoring signal was transmitted to a second terminal, which may be another terminal of the terrestrial optical network connected to the first terminal. In this case, it may be determined that future optical signals transmitted to the same node may be configured as terrestrial optical signals. For example, this may involve transmitting the optical signal at a predetermined power level or not attenuating the optical signal prior to transmission.

[0066] Alternatively, if it is determined that the monitoring signal is transmitted back to the first terminal, operations continue at block 440 where the first terminal determines that the monitoring signal is rerouted or looped back to the first terminal by the OCI of a submarine cable connecting the terrestrial optical network to a nearby submarine optical network.

[0067] In response to the determination at block 440, the first terminal may initiate a submarine cable use case at block 450. Initiating the submarine cable use case may involve setting or changing one or more configurations of the first terminal to accommodate communication between the first terminal and a nearby submarine optical network over the OCI.

[0068] In some examples, initiating a submarine cable use case may involve initiating a power reduction procedure 452. The power reduction procedure may maintain the power level of transmissions to the OCI and the submarine cable at or below a predetermined power level. The predetermined power level may be determined based on specifications and guidelines, such as safety guidelines, for submarine cables. In the case of telecommunications, optical networks typically adhere to safety guidelines for Class 1M lasers. In the event that the power level of the communication signal is above the predetermined power level, the power reduction procedure may cause the power level of the communication signal to be reduced.

[0069] In some examples, initiating a submarine cable use case can involve updating the travel distance between the first terminal and the OCI 454. Typically, a monitoring signal transmitted between nodes of a terrestrial network travels between a transmitting node and different receiving nodes, and the travel distance between the transmitting node and the receiving nodes can be derived from the elapsed time of the signal's travel. However, in the case where the monitoring signal is transmitted to the OCI and then looped back to the transmitting node, the travel distance of the signal is actually twice the distance between the transmitting node and the OCI. Therefore, in order to correctly derive the travel time between the transmitting node and the OCI, the distance between the transmitting node and the OCI may be halved. Determining to halve the distance can be accomplished by a configuration at the first terminal, whereby when the configuration is effective, the travel time of the monitoring signal transmitted from the first terminal to the OCI can be evaluated based on the halved travel distance.

[0070] In some examples, initiating a submarine cable use case can involve updating the actual loss or attenuation of a monitoring signal between the first terminal and the OCI 456. Typically, for monitoring signals transmitted between nodes of a terrestrial network, the amount of signal loss experienced between a transmitting node and a receiving node can be detected by determining a signal property at each of the transmitting node and the receiving node, such as the power level of the signal. However, where a monitoring signal is transmitted to the OCI and then looped back to the transmitting node, the signal may experience double the loss during transmission because it travels twice the distance. Therefore, in order to correctly derive the actual loss experienced by the monitoring signal between the transmitting node and the OCI, the loss measured at the transmitting node may be halved. Determining to halve the measured loss can be accomplished by a configuration at the first terminal, whereby, when the configuration is effective, the measured loss is halved in order to derive an estimate of the actual loss experienced in a single trip from the first terminal to the OCI.

[0071] Can be done during the installation of OCI Figure 4 4. In other words, the first terminal may initially determine the presence of the OCI upon installation of the OCI or the first terminal, and may initialize its settings to properly monitor the OCI to transmit communication signals to the OCI in compliance with submarine cable guidelines, or a combination thereof. After this initialization, operations may continue based on the initialized configuration. In some instances, the first terminal may be able to periodically or continuously monitor the loopback of the monitoring signal, meaning that if the signal does not loop back or if a confirmation signal is received at a future time, the first terminal may determine to update its settings based on the detected presence of the second ground terminal replacing the OCI.

[0072] Because the configuration operation is performed from a terrestrial terminal remote from the OCI, rather than at the OCI itself, it should be appreciated that installation of the terrestrial terminal can be performed by a skilled technician, even if the terminal is installed adjacent to the OCI that interfaces with the submarine optical network. In contrast, when an SLTE needs to be installed adjacent to the OCI to interface the terrestrial and submarine optical networks, a specially trained technician is required to install the SLTE.

[0073] Therefore, the terrestrial optical network and the submarine optical network can be connected to each other through standard "terrestrial-grade" ground terminal equipment without the need for specialized or dedicated terminal equipment. In addition, the installation of standard ground terminal equipment can be performed by ordinary "terrestrial-grade" service technicians. This avoids the high costs usually associated with both specialized SLTE hardware and "white glove" professional technicians to install it.

[0074] In addition, using standard terrestrial terminal equipment instead of SLTE means that all terminals included in the optical network have the same terminal equipment. This allows a single SKU to be used to track all terminal equipment, which in turn saves a lot of time, trouble and expense for those responsible for tracking and maintaining optical network hardware.

[0075] Although the technology herein has been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the technology. It should be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the technology as defined by the appended claims.

[0076] Most of the aforementioned alternative examples are not mutually exclusive, but can be implemented in various combinations to achieve unique advantages. Because these and other variations and combinations of the features discussed above can be utilized without departing from the subject matter defined by the claims, the foregoing description of the embodiments should be understood by way of illustration rather than limitation of the subject matter defined by the claims. As an example, the preceding operations do not have to be performed in the exact order described above. Instead, the various steps can be handled in a different order, such as, reversed or simultaneously. Unless otherwise indicated, steps may also be omitted. In addition, the provision of the examples described herein and the terms expressed as "such as," "including," etc. should not be interpreted as limiting the subject matter of the claims to specific examples; on the contrary, the examples are intended to illustrate only one of many possible embodiments. In addition, the same reference numerals in different figures may identify the same or similar elements.

Claims

1. A system comprising: one or more processors; as well as a memory in communication with the one or more processors, wherein the memory contains instructions that, when executed by the one or more processors, cause the one or more processors to perform operations comprising: transmitting a monitoring signal from a terminal of a ground optical fiber cable of a ground network; detecting the monitoring signal reflected back to the terminal; In response to detecting that the monitoring signal is reflected back to the terminal, it is determined that the monitoring signal is rerouted by the optical cable interface to the submarine cable.

2. The system according to claim 1, wherein: The operations further include initiating a power reduction procedure in response to determining that the monitoring signal is rerouted to a submarine cable by the fiber optic cable interface, the power reduction procedure configured to maintain a transmission power level to the submarine cable at or below a predetermined power level.

3. The system according to claim 2, wherein: The operations further include: monitoring a power level of a communication signal passed through a WDM filter of the open cable interface; and In response to determining that the monitoring signal is rerouted to the submarine cable by the fiber optic cable interface, the power level of the communication signal is adjusted to be equal to or below a predetermined submarine cable power level.

4. The system according to claim 1, wherein: The operations further include, in response to determining that the monitoring signal is rerouted by the optical cable interface to the submarine cable: setting the monitoring signal's travel distance from the terminal to the optical cable interface and back to the terminal to be twice the distance between the terminal and the optical cable interface; and A travel time of a monitoring signal transmitted from the terminal to the optical cable interface is evaluated based on the set travel distance.

5. The system according to claim 1, wherein: The operations further include, in response to determining that the monitoring signal is rerouted by the optical cable interface to the submarine cable: determining a loss of a supervisory signal transmitted from the terminal to the open cable interface and back to the terminal; and The actual loss of the supervisory signal transmitted from the terminal to the open cable interface is estimated to be half of the determined loss.

6. An optical network comprising: a plurality of terrestrial optical cable terminals, the plurality of terrestrial optical cable terminals comprising a first terrestrial optical cable terminal for docking an optical cable interface to a submarine cable and a second terrestrial optical cable terminal for not docking an optical cable interface to the submarine cable; as well as The system according to claim 1.

7. The optical network according to claim 6, wherein: The first terrestrial cable terminal and the second terrestrial cable terminal have a common SKU.

8. A method comprising: transmitting, by one or more processors, a monitoring signal from a terminal end of a terrestrial fiber optic cable of a terrestrial network; detecting, by the one or more processors, the monitoring signal reflected back to the terminal; as well as In response to detecting that the monitoring signal is reflected back to the terminal, the one or more processors determine that the monitoring signal is rerouted by the fiber optic cable interface to the submarine cable.

9. The method according to claim 8, wherein The method is performed during initialization of a monitoring program for monitoring signals transmitted over the terrestrial network.

10. The method of claim 9, further comprising initiating a submarine cable use case in response to determining that the monitoring signal is rerouted to a submarine cable by the optical cable interface, wherein the submarine cable use case comprises one or more of the following: reducing the power level of a communication signal transmitted from the terminal toward the open cable interface to a predetermined submarine cable power level or below; evaluating a travel time of a monitoring signal transmitted from the terminal toward the open cable interface as a round trip time; as well as The loss of the supervisory signal transmitted from the terminal toward the open cable interface is assessed to be half the measured loss at the terminal.

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