Adaptive loss of signal marker for self-tuning process in amplified optical systems

Abstract

A first optical transceiver can enable loss of optical signal ("LOS") detection by transmitting (810) an optical signal including an optical marker toward a second optical transceiver via an optical communication path. The first optical transceiver can further receive (820) an indication that the second optical transceiver failed to receive the optical marker. The first optical transceiver can further determine (830) that a LOS associated with the optical signal occurred based on the indication that the second optical transceiver failed to receive the optical marker.

Description

ADAPTIVE LOSS OF SIGNAL MARKER FOR SELF-TUNING PROCESS IN AMPLIFIED OPTICAL SYSTEMSTECHNICAL FIELD

[0001] The present disclosure is related to wireless communication systems and more particularly to an adaptive loss of signal (“LOS”) maker for a self-tuning process in an amplified optical system.BACKGROUND

[0002] FIG. 1 illustrates an example of a new radio (“NR”) network (e.g., a 5th Generation (“5G”) network) including a 5G core (“5GC”) network 130, network nodes 120a-b (e.g., 5G base station (“gNB”)), multiple communication devices 110 (also referred to as user equipment (“UE”)).

[0003] Self-tuning is a procedure that allows two tunable transceivers to automatically find a correct optical path between themselves (e.g., passing through an optical system that includes optical filters). The two transceivers can transmit tuning data to each other, which can indicate the transmitted frequency and the subsequent received frequency. This transmission of data can be obtained by adding an overmodulated signal (sometimes referred to herein as an optical communication channel) to transmitted high-speed traffic.

[0004] There can be different ways to transmit the tuning data. In one example, a laser of a transceiver is over modulated and this very small signal is detected by a receiver photodiode of the other transceiver. In order to keep the disturbance of the over modulated optical signal for the high-speed traffic as low as possible, very low modulation (e.g., deep and low rates) are used. In another example, an ON-OFF modulation of the laser is used instead of a very small modulation signal overmodulated with respect to the high speed signals. In this example, there could be only the self-tuning signals (the modulation of laser is ON-OFF).

[0005] It is desirable to enable self-tuning of amplified optical systems. However, errors can arise in either of the above examples of a self-tuning process if the optical path includes a power amplifier.SUMMARY

[0006] According to some embodiments, a method of operating a first optical transceiver to enable loss of signal (“LOS”) detection is provided. The method includes transmitting an optical signal including an optical marker toward a second optical transceiver via an optical communication path. The method further includes receiving an indication that the second optical transceiver failed to receive the optical marker. The method further includes determiningthat a LOS associated with the optical signal occurred based on the indication that the second optical transceiver failed to receive the optical marker.

[0007] According to other embodiments, a method of operating a first optical transceiver to perform a self-tuning procedure is provided. The method includes transmitting a first optical signal toward a second optical transceiver using a first bit rate. The method further includes receiving an indication of a loss of signal (“LOS”) associated with the first optical signal from the second optical transceiver. The method further includes, responsive to receiving the indication of the LOS, transmitting a second optical signal toward the second optical transceiver using a second bit rate that is greater than the first bit rate. The method further includes, responsive to determining that the second optical signal was successfully received by the second optical transceiver, selecting the second bit rate to be used for transmission of subsequent optical signals.

[0008] According to other embodiments, a method of operating a second optical transceiver to enable loss of signal (“LOS”) detection is provided. The method includes receiving an optical signal from an optical communication path associated with a first optical transceiver. The method further includes determining whether the optical signal includes an optical marker. The method further includes transmitting an indication of whether the optical signal includes the optical marker to the first optical transceiver.

[0009] According to other embodiments, a method of operating a second optical transceiver to perform a self-tuning procedure is provided. The method includes receiving a first optical signal from an optical communication path associated with a first optical transceiver using a first bit rate. The method further includes transmitting an indication of a loss of signal (“LOS”) associated with the first optical signal to the first optical transceiver. The method further includes, responsive to transmitting the indication of the LOS, receiving a second optical signal from the optical communication path using a second bit rate that is greater than the first bit rate. The method further includes, responsive to determining that the second optical signal was successfully received, selecting the second bit rate to be used for reception of subsequent optical signals.

[0010] According to other embodiments, a network node, an optical transceiver, a computer program, a computer program product, a non-transitory readable medium, optical system, or host is provided to perform one of the above methods.

[0011] Certain aspects of these embodiments may provide technical advantages. In some embodiments, the use of an optical marker is independent from the absence or presence of highspeed traffic (e.g., it works with all speeds of traffic). In additional or alternative embodiments, the use of an optical marker can be implemented inside the transceiver and may not require anyactions from the host. In additional or alternative embodiments, the use of an optical marker is compatible with optical systems without amplifiers (e.g., it works in non-amplified and amplified optical systems).BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate certain non-limiting embodiments of inventive concepts. In the drawings:

[0013] FIG. 1 is a schematic diagram illustrating an example of a 5thgeneration (“5G”) network;

[0014] FIG. 2 is a schematic diagram illustrating an example of a Tx-Rx optical system connected by optical fiber in an amplified system in accordance with some embodiments;

[0015] FIG. 3 is a block diagram illustrating an example of an optical transceiver in accordance with some embodiments;

[0016] FIG. 4 is a diagram illustrating an example of a communication channel being distorted by a power amplifier in accordance with some embodiments;

[0017] FIG. 5 is a graph illustrating an example of how an increase in communication bitrate (modulation frequency) effects a sensitivity penalty of high-speed traffic in accordance with some embodiments;

[0018] FIG. 6 is flow chart illustrating an example of operations performed by an optical system during startup of a SFP in accordance with some embodiments;

[0019] FIG. 7 is flow chart illustrating an example of operations performed by an optical system in response to a LOS marker being detected in accordance with some embodiments;

[0020] FIGS. 8-9 are flow charts illustrating examples of operations performed by a first optical transceiver in accordance with some embodiments;

[0021] FIGS. 10-11 are flow charts illustrating examples of operations performed by a second optical transceiver in accordance with some embodiments;

[0022] FIG. 12 is a block diagram of a communication system in accordance with some embodiments;

[0023] FIG. 13 is a block diagram of a user equipment in accordance with some embodiments;

[0024] FIG. 14 is a block diagram of a network node in accordance with some embodiments;

[0025] FIG. 15 is a block diagram of a host, which may be an embodiment of the host of FIG. 12, in accordance with some embodiments;

[0026] FIG. 16 is a block diagram of a virtualization environment in accordance with some embodiments; and

[0027] FIG. 17 shows a communication diagram of a host communicating via a network node with a user equipment over a partially wireless connection in accordance with some embodiments.DETAILED DESCRIPTION

[0028] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art, in which examples of embodiments of inventive concepts are shown. Inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of present inventive concepts to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. Components from one embodiment may be tacitly assumed to be present / used in another embodiment.

[0029] FIG. 2 illustrates an example of a Tx-Rx optical system 200 including a pair of small form pluggable, SFP, optical modules 210a-b connected by optical fiber in an amplified subsystem. In some examples, the SFP optical modules 210a-b are referred to herein as optical transceivers. In additional or alternative examples, each of the SFP optical modules 210a-b are included in separate optical transceivers. The amplified subsystem includes a pair of optical filters 212a-b and amplifiers 214a-b. A first optical communication path (including one or more optical fibers) couples a transmitter associated with the SFP optical module 210a with a receiver associated with the SFP optical module 210b via optical filters 212a-b and amplifier 214a. A second optical communication path (including one or more optical fibers) couples a transmitter associated with the SFP optical module 210b with a receiver associated with the SFP optical module 210a via optical filters 212a-b and amplifier 214b.

[0030] FIG. 3 illustrates an example of an optical transceiver 300 (e.g., that may be or include one of the SFP optical modules 210a-b). In this example, the optical transceiver 300 includes a transmitter 310, a receiver 320, processing circuitry 330, and memory 340. The memory 340 can include instructions that are executable by processing circuitry 330 to cause the optical transceiver 300 to transmit, via transmitter 310, or receive, via receiver 320, optical signals.

[0031] Two optical transceivers (e.g., associated with SFP optical modules 210a-b) to automatically find a correct optical path between themselves (e.g., passing through the opticalsubsystem that includes optical filters 212a-b). The two optical transceivers can transmit data, e.g. tuning data or control channel data, to each other, which can indicate the transmitted frequency and the subsequent received frequency. This transmission of data can be obtained by adding an overmodulated signal (sometimes referred to herein as an optical signal or optical communication channel) to transmitted high-speed traffic being transmitted between the optical transceivers.

[0032] There currently exist certain challenges with extending the self-tuning procedure to optical systems that include an optical power amplifier (e.g., as illustrated in FIG. 2). Suppression of transient algorithms applied from amplifiers to the optical signals may be present in in transport networks. These algorithms can interfere with the low-speed communication channels preventing good communication between the two optical transceivers and compromising the convergence of the self-tuning procedures. For example, a power amplifier may receive an optical signal with a slope of 3dB in 50us as input and provide an optical signal with a slope of 0.6 dB as output. Independently from the modulation format used by the communication channel of the self-tuning procedure, once the self-tuning has converged and the optical power of the transceivers is stable at the correct frequencies to pass through the optical filters, the only way to start the self-tuning is if the optical path is disconnected (e.g., because the channel is changed in the optical filters). In some examples, the optical power amplifier comprises a transient suppression mechanism, or operates using a transient suppression mechanism. The transient suppression mechanism suppresses variations in the optical signal which have a relatively low frequency, e.g. suppress variations in the optical signal below a threshold. The suppression, or reduction in power, of the optical signal may be entirely below a threshold frequency or a gradual reduction in power which, for example, may be defined by a reduction amount below a threshold frequency. Thus, the optical signal comprising the control channel data may be unintentionally reduced in power if the frequency of the optical signal is too low, e.g. below the threshold of the amplifier transient suppression mechanism. In some examples, the frequency of the optical signal is tuned to have a frequency which is not substantially suppressed by the transient suppression mechanism, i.e. has a frequency above the threshold of the transient suppression mechanism.

[0033] In some examples, the disconnection of the optical path is revealed by the optical loss of input power to the transceivers if a loss of signal (“LOS”) is detected for an amount of time, the self-tuning process is started again to find the eventual new optical path. An issue of this approach is that in amplified systems, the optical noise of amplifiers can be enough to prevent the transceivers from detecting the LOS of the channel. The transceivers may not distinguish between laser light or optical noise of amplifiers. This issue can be identical in anyconfiguration of the amplifier. If the amplifier is after the filters (amplification channel by channel) all the noise is detected form the transceivers. In the case the amplifier is before the optical filters (amplification for many channels), the noise passing thought the filters (e.g., 100GHz or 50GHz passband / grid) is much higher than LOS thresholds (e.g., real measured numbers are -19 dBm of noise against a LOS threshold of -27 dBm).

[0034] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. In some embodiments, the distortion of the messages of the service channel can be managed (ignored) based on increasing the bit rate or speed of the messages. In some examples, increasing the bit rate of the communication channel of the optical signal can enable optical amplifiers to distinguish between the optical signal and the optical transient from the power amplifier. As such, the bit rate, or modulation frequency, of the optical signal is above threshold of the transient suppression mechanism of the amplifier. Thus, the optical amplifier is distinguishing the optical signal (i.e. not suppressing the power of the optical signal) from low frequency optical transients (i.e. noise variations in optical power). This allows the optical signal, comprising the LOS marker or pattern, to not be suppressed or blocked by the amplifier.

[0035] In additional or alternative embodiments, an optical transceiver can detect a LOS based on absence of an optical marker in the optical signal rather than a than loss of power. This different trigger can be used to ensure self-tuning starts (and ends) appropriately regardless of optical noise produced by the optical amplifiers. In some examples, absence of this optical marker for an amount of time (e.g., persistency) will raise the LOS alarm and will start the selftuning process.

[0036] FIG. 4 illustrates an example of measurements taken from an optical signal being communicated between two optical transceivers. In this example, the communication signal 410 (being communicated at lOKb / s (one bit = 100us)) between the optical transceivers is errored because the bits of the communication channel are distorted (especially the 1-1 sequence) by the transient suppression mechanism of an amplifier (which here has a minimum transient speed of 50us). This can be observed by comparing the bits of the self-tuning amplified signal 420 and not amplified signal 430. Reducing the frequency of a communication channel (e.g., reducing the period of time it takes for a message to be transmitted) so that it reaches a time below the minimum speed (or time slot) that the amplifier is able to suppress (or reduce) can allow an optical signal to avoid distortion. Therefore, increasing the bitrate (reducing the time period it takes for a message to be transmitted) can allow an optical signal to be transmitted (and received) without error. In some examples, repeated modulation symbols, e.g. a 1-1 sequence, effectively have a lower modulation frequency than symbols which include a transition, e.g. a 1-0 sequence. As such, repeated modulation symbols are more at risk of being suppressed by the amplifier transient suppression mechanism.

[0037] FIG. 5 illustrates an example of how increasing communication bitrate of the optical signal impacts a sensitivity penalty of corresponding high-speed traffic. In this example, increasing the modulation frequency of an optical signal to above e.g. 125 KHz can result in a penalty of over IdB to the actual data being communicated (e.g., high-speed traffic). A potential loss of IdB in an optical system can shorten the maximum distance between the optical transceivers by several kilometers. Therefore, it can be important to optimize between increasing the bit rate of a communication channel (e.g., modulation frequency of the optical signal) and ensuring that absence of an optical marker in the communication channel can be detected despite distortion from power amplifiers in the optical communication path. Examples provide for an optimization of a frequency for an optical signal carrying control data (e.g. a LOS marker or tuning data). The frequency for the optical signal is determined to be a frequency which is high enough to not be suppressed by the optical amplifier (e.g. above the threshold for the transient suppression mechanism) and low enough frequency to achieve the required transmission distance of optical signal (e.g. below a threshold for optical transmission over a pre-determined distance).

[0038] FIG. 6 illustrates an example of a possible state machine associated with initialization of a communication path between a pair of optical transceivers (a first optical transceiver and a second optical transceiver) including determining an appropriate communication bit rate. In this example, the optical system is preconfigured with the following features: minimum bit rate (minBitRate) is 5Kb / s;; maximum bit rate (maxBitRate) is 200Kb / s; a bit rate increment value (Step) of 5Kb / s; a trial pulse duration of 2 seconds; a persistency time of 10 seconds; and an unknown appropriate bit rate (BitRateFinal). In other examples, the optical system may be preconfigured with different features.

[0039] At block 610, a first optical transceiver enters a powered state. In some examples, the first optical transceiver enters the powered state and begins an initial startup based on transitioning from an OFF state. In additional or alternative examples, either or both of the first optical transceiver and the second optical transceiver transition from an OFF state. In this example, the initial startup proceeds by moving the optical system to a state associated with block 640.

[0040] At block 640, the first optical transceiver transmits data over the communication channel toward the second optical transceiver at the minBitRate. In some examples, the first optical transceiver transmits the data for a length of time equal to the trial pulse duration time.In additional or alternative examples, the first optical transceiver notifies the second optical transceiver of the bit rate being used (the minBitRate). After transmitting the data (e.g., at the end of the trial pulse duration time or in response to an error being reported), the optical system moves to a state associated with block 650.

[0041] At block 650, the optical system determines whether the second optical transceiver received the data without errors. In some examples, the optical system determines whether the second optical transceiver received the data without errors for a threshold amount of time (e.g., the persistency time). In some embodiments, the second optical transceiver transmits an indication to the first optical transceiver of any errors or LOS. If the optical system determines that there were errors, it moves to a state associated with block 660. Otherwise, the optical system determines there were no errors and moves to a state associated with block 680.

[0042] At block 660, the optical system determines whether a bit rate used to transmit the data is equal to the maxBitRate. If the bit rate used to transmit the data is equal to the maxBitRate, the optical system may decide to restart this process by returning to the state associated with block 640. If the bit rate used to transmit the data is not equal to the maxBitRate, the optical system may decide to iterate this process with a larger bit rate by moving to the state associated with block 670.

[0043] At block 670, the optical system transmits data over the communication channel toward the second optical transceiver at a new bit rate (BitRateActual) that is equal to the bit rate that was previously being used incremented by the Step. In some examples, the first optical transceiver transmits the data for a length of time equal to the trial pulse duration time. In additional or alternative examples, the first optical transceiver notifies the second optical transceiver of the new bit rate being used (the BitRateActual). After transmitting the data (e.g., at the end of the trial pulse duration time), the optical system returns to a state associated with block 650 to determine whether the data transmitted using BitRateActual was received without any errors.

[0044] At block 680 (after the data was transmitted without error), the optical system determines BitRateFinal to be the bit rate used to transmit the data without error (the minBitRate or BitRateActual). Furthermore, the first optical transceiver continues transmitting data in the communication channel at BitRateFinal.

[0045] At block 690, the optical system continues to communicate between the optical transceivers using BitRateFinal without errors. In some embodiments, when an error occurs the optical system moves to a state associated with block 710 of FIG. 7.

[0046] FIG. 7 illustrates an example of a possible state machine associated with operation of an optical system (e.g., that includes a first optical transceiver and a second opticaltransceiver) in response to detecting a LOS due to absence of an optical marker in an optical signal received by the second optical transceiver. In some examples, the state machine includes operations to allow the optical system to determine a new appropriate bit rate. In this example, the optical system is preconfigured with the following features: minimum bit rate (minBitRate) is 5Kb / s;; maximum bit rate (maxBitRate) is 200Kb / s; a bit rate increment value (Step) of 5Kb / s; a first access time of 5 minutes; a trial pulse duration of 2 seconds; a persistency time of 10 seconds; and an unknown appropriate bit rate (BitRateFinal). In other examples, the optical system may be preconfigured with different features.

[0047] At block 710, the optical system determines that there are errors in a communication channel of an optical signal received at the second optical transceiver. In some examples, the second optical transceiver determines that there are errors in the communication channel based on an absence of an optical marker in the received communication channel. The second optical transceiver can then notify the first optical transceiver that there is a LOS based on the absence of the optical marker. In some examples, this notification is a LOS alarm that enables the restart of a self-tuning process.

[0048] In some embodiments, the optical marker can be included in optical signals transmitted by the first optical transmitter. In some examples, the optical marker includes a specific message included in the communication channel . For example, the message is continuously or continually transmitted by the first optical transmitter, e.g. after a first convergence of the self-tuning procedure (e.g., after the operations in FIG. 6). In some examples, the optical marker is a pattern of bits which is transmitted, e.g. a pre-determined pattern of bits which is identified by the receiver as the LOS marker. Ceasing of detection of the LOS marker will indicate that there is a loss of signal. In additional or alternative examples, the communication channel is a failure alarm of the communication channel, e.g. when the communication channel is used for remote diagnostic monitoring. For example, the marker used as the failure alarm may be used to indicate LOS. In additional or alternative examples, the LOS marker may be a predetermined frequency of transitions of the line coding. For example, the communication channel is used for remote diagnostic monitoring implemented with a line coding creating transitions at a fixed rate (e.g., Manchester coding). The optical marker can be defined as the presence of the transitions at the fixed rate (e.g., detected from a narrow bandwidth electrical filter). Thus, the LOS marker is identified as the ceasing of modulation at the fixed rate.

[0049] In additional or alternative embodiments, each of the optical markers described above can be adapted to be used with amplified optical systems. An amplifier can have a transient suppression mechanism with a minimum transient speed (e.g., low frequency variation and / or noise suppression). Therefore, it can be beneficial to increase the communicationchannel frequency to use a frequency outside of the amplifier suppression mechanism. The operations in FIG. 7 can enable an optical system to scan all possible frequencies (for the single tone or for the communication channel). For example, the scan may start from a low frequency and increasing the frequency, until the optical signal is received in a acceptable manner, e.g. an error free LOS marker notification (encoded in the communication channel) is received from the second optical transceiver. Then the scan is stopped, and the notified frequency is used for the LOS marker by the first optical transceiver. In some examples, the scan may find the minimum possible frequency for the communication channel (and then, for the LOS marker) in order to minimize the penalty on the high-speed traffic as discussed above in regards to FIG. 5. In other examples, the scan may start from a high frequency and reduce the frequency until the frequency is in the suitable range, e.g. not suppressed by the transient suppression mechanism and with enough power to be transmitted the distance between the transceivers. Other tuning arrangements may be used to determine the frequency for the optical signal.

[0050] At block 720, the first optical transmitter transmits data on the communication channel at a first bit rate. In some examples, the first bit rate is the BitRateFinal (as determined at the end of startup in FIG. 6). In additional or alternative examples, the first bit rate is an incremented version of the BitRateFinal (e.g., incremented by the Step value). The data can be transmit for a first access time and the first optical transceiver may notify the second optical transceiver of the bit rate that is used to transmit the data. After transmitting the data (e.g., at the end of the trial pulse duration time or in response to an error being reported), the optical system moves to a state associated with block 730.

[0051] At block 730, the optical signal determines whether the data was received without errors for a persistency time. For example, the persistency time is a time period over which the LOS marker is determined to be received. If the data was received without error during this time period, the optical system may move to a state associated with block 680. If there were errors (e.g., a LOS was determined by the second optical transceiver), the optical system may move to a state associated with block 640.

[0052] Blocks 640, 650, 660, 670, 680, and 690 of FIG. 7 are substantially the same as blocks 640, 650, 660, 670, 680, and 690 of FIG. 6 and involve incrementing the bit rate until data can be transmitted without error. Then the bit rate that is used to transmit the data without error is set as the new BitRateFinal for subsequent transmission of optical signals.

[0053] In additional or alternative embodiments, independently from the implementation of this new LOS alarm, there can be a suitable persistency to avoid erroneous restarting of the selftuning process.

[0054] In additional or alternative embodiments, an additional single tone can be transmitted from one optical transceiver to the other optical transceiver. In this example, the notification of the received frequency may not be possible, so the frequency of the single tone may be set by the host, knowing the amplifiers characteristics, or fixed to a value as higher as possible (e.g., 200 KHz) in a compatible way with the specification about the sensitivity penalty (as illustrated in FIG. 5).

[0055] Operations of the network node 1400 (implemented using the structure of FIG. 14) will now be discussed with reference to the flow chart of FIGS. 8-11 according to some embodiments of inventive concepts. For example, modules may be stored in memory 1406 of FIG. 14, and these modules may provide instructions so that when the instructions of a module are executed by respective network node processing circuitry 1402, network node 1400 performs respective operations of the flow charts. Although the operations are described as being performed by network node 1400 similar operations may be performed by optical transceiver 300.

[0056] FIG. 8 illustrates an example of operations performed by a first optical transceiver to enable loss of signal (“LOS”) detection.

[0057] At block 810, processing circuitry 1402 transmits, via communication interface 1406, an optical signal including an optical marker. In some examples, the optical signal is transmitted via an optical communication path that includes an optical power amplifier. In some embodiments, transmitting the optical signal includes periodically transmitting a predetermined message as part of a communication channel. In additional or alternative embodiments, transmitting the optical signal includes transmitting the optical signal using line coding to create transitions at a fixed rate. In some examples, the communication channel is associated with remote diagnostic monitoring and the optical marker is a failure alarm of the communication channel.

[0058] At block 820, processing circuitry 1402 receives, via communication interface 1406, an indication that the optical marker was not received.

[0059] At block 830, processing circuitry 1402 determines that a LOS associated with the optical signal occurred.

[0060] At block 840, processing circuitry 1402 performs a self-tuning procedure. In some embodiments, the self-tuning procedure includes adjusting a bit rate of subsequent optical signal transmissions.

[0061] In additional or alternative embodiments, the optical power amplifier is configured with a transient suppression mechanism with a minimum transient speed. Performing the self-tuning procedure further includes adjusting the bit rate of subsequent optical signal transmissions to account for the transient suppression mechanism.

[0062] FIG. 9 illustrates an example of operations performed by a first optical transceiver to perform a self-tuning procedure.

[0063] At block 910, processing circuitry 1402 transmits, via communication interface 1406, a first optical signal toward a second optical transceiver using a first bit rate.

[0064] At block 920, processing circuitry 1402 receives, via communication interface 1406, an indication of a LOS associated with the first optical signal (e.g., an indication that the second optical transceiver failed to receive the optical marker).

[0065] At block 930, processing circuitry 1402 transmits, via communication interface 1406, a second optical signal using a second bit rate that is greater than the first bit rate. In some embodiments, transmitting the second optical signal includes: transmitting a plurality of optical signals, each optical signal of the plurality of optical signals being transmitted at a bit rate that is higher than a bit rate of an immediately previously transmitted optical signal; and receiving an indication of a LOS associated with each optical signal of the plurality of optical signals except for the second optical signal.

[0066] In additional or alternative embodiments, the first bit rate is a predetermined minimum bit rate. Transmitting the first optical signal includes transmitting the first optical signal toward the second optical transceiver in response to at least one of: the first optical transceiver and the second optical transceiver entering an ON state.

[0067] At block 940, processing circuitry 1402 selects the second bit rate to be used for transmission of subsequent optical signals based on the second optical signal being successfully received.

[0068] In some embodiments the operations of FIGS. 8-9 are interchangeable. For example, the operations of FIG. 9 may occur as part of a self-tuning procedure in response to detecting the LOS in FIG. 8. In other examples, the optical marker of FIG. 8 may be used to detect error in optical signals transmitted in FIG. 9.

[0069] FIG. 10 illustrates an example of operations performed by a second optical transceiver to enable loss of signal (“LOS”) detection.

[0070] At block 1010, processing circuitry 1402 receives, via communication interface 1406, an optical signal. In some examples, the optical signal is received via an optical communication path that includes an optical power amplifier.

[0071] At block 1020, processing circuitry 1402 determines whether the optical signal includes an optical marker. In some embodiments, determining whether the optical signal includes the optical marker includes determining whether the optical signal comprises apredetermined message as part of a communication channel. In additional or alternative embodiments, determining whether the optical signal includes the optical marker comprises determining whether the optical signal includes transitions at a predetermined rate in a communication channel. In some examples, the communication channel is associated with remote diagnostic monitoring. The optical marker is a failure alarm of the communication channel. In additional or alternative examples, the optical communication path includes an optical power amplifier.

[0072] At block 1030, processing circuitry 1402 transmits, via communication interface 1406, an indication of whether the optical signal includes the optical marker to a source of the optical signal.

[0073] At block 1040, processing circuitry 1402 performs a self-tuning procedure in response to the optical signal failing to include the optical marker. In some examples, performing the self-tuning procedure includes receiving subsequent optical signals from the first optical transceiver at an adjusted bit rate. In additional or alternative examples, an optical power amplifier (in the optical communication path) is configured with a transient suppression mechanism with a minimum transient speed. Performing the self-tuning procedure further includes receiving subsequent optical signals from the first optical transceiver at a bit rate adjusted for the transient suppression mechanism.

[0074] FIG. 11 illustrates an example of operations performed by a second optical transceiver to perform a self-tuning procedure.

[0075] At block 1110, processing circuitry 1402 receives, via communication interface 1406, a first optical signal using a first bit rate. In some embodiments, the first bit rate is a predetermined minimum bit rate. Receiving the first optical signal includes receiving the first optical signal in response to at least one of: the first optical transceiver and the second optical transceiver entering an ON state.

[0076] At block 1120, processing circuitry 1402 transmits, via communication interface 1406, an indication of a LOS associated with the first optical signal.

[0077] At block 1130, processing circuitry 1402 receives, via communication interface 1406, a second optical signal using a second bit rate that is greater than the first bit rate. In some embodiments, receiving the second optical signal includes: receiving a plurality of optical signals, each optical signal of the plurality of optical signals using a bit rate that is higher than a bit rate of an immediately previously received optical signal; and transmitting an indication of a LOS associated with each optical signal of the plurality of optical signals except for the second optical signal.

[0078] At block 1140, processing circuitry 1402 selects the second bit rate to be used for subsequent optical signals based on the second optical signal being successfully received.

[0079] In some embodiments the operations of FIGS. 10-11 are interchangeable. For example, the operations of FIG. 11 may occur as part of a self-tuning procedure in response to detecting the LOS in FIG. 10. In other examples, the optical marker of FIG. 10 may be used to detect error in optical signals transmitted in FIG. 11.

[0080] Various operations from the flow charts of FIGS. 8-13 may be optional with respect to some embodiments of network nodes and related methods.

[0081] FIG. 12 shows an example of a communication system 1200 in accordance with some embodiments.

[0082] In the example, the communication system 1200 includes a telecommunication network 1202 that includes an access network 1204, such as a radio access network (RAN), and a core network 1206, which includes one or more core network nodes 1208. The access network 1204 includes one or more access network nodes, such as network nodes 1210a and 1210b (one or more of which may be generally referred to as network nodes 1210), or any other similar 3rd Generation Partnership Project (3GPP) access node or non-3GPP access point. Moreover, as will be appreciated by those of skill in the art, the network nodes 1210 are not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that the network nodes 1210 may include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network 1202 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 1202 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 1202, including one or more network nodes 1210 and / or core network nodes 1208.

[0083] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU- CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time RAN control application (e.g., xApp) or a non-real time RAN automation application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Intents and content-awarenotifications described herein may be communicated from a 3GPP network node or an ORAN network node over 3GPP-defined interfaces (e.g., N2, N3) and / or ORAN Alliance-defined interfaces (e.g., Al, 01). Moreover, an ORAN network node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the 0-RAN Alliance. The network nodes 1210 facilitate direct or indirect connection of user equipment (UE), such as by connecting wireless devices 1212a, 1212b, 1212c, and 1212d (one or more of which may be generally referred to as UEs 1212) to the core network 1206 over one or more wireless connections. The network nodes 1210 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 1212a, 1212b, 1212c, and 1212d (one or more of which may be generally referred to as UEs 1212) to the core network 1206 over one or more wireless connections.

[0084] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1200 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system 1200 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0085] The UEs 1212 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes 1210 and other communication devices. Similarly, the network nodes 1210 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 1212 and / or with other network nodes or equipment in the telecommunication network 1202 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network 1202.

[0086] In the depicted example, the core network 1206 connects the network nodes 1210 to one or more hosts, such as host 1216. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1206 includes one more core network nodes (e.g., core network node 1208) that are structured with hardware and software components. Features ofthese components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1208. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0087] The host 1216 may be under the ownership or control of a service provider other than an operator or provider of the access network 1204 and / or the telecommunication network 1202, and may be operated by the service provider or on behalf of the service provider. The host 1216 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0088] As a whole, the communication system 1200 of FIG. 12 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low- power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0089] In some examples, the telecommunication network 1202 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 1202 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1202. For example, the telecommunications network 1202 may provide Ultra Reliable Low Latency Communication (URLLC) services tosome UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC)ZMassive loT services to yet further UEs.

[0090] In some examples, the UEs 1212 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 1204 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1204. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved- UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0091] In the example, the hub 1214 communicates with the access network 1204 to facilitate indirect communication between one or more UEs (e.g., UE 1212c and / or 1212d) and network nodes (e.g., network node 1210b). In some examples, the hub 1214 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 1214 may be a broadband router enabling access to the core network 1206 for the UEs. As another example, the hub 1214 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1210, or by executable code, script, process, or other instructions in the hub 1214. As another example, the hub 1214 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1214 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 1214 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1214 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 1214 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy loT devices.

[0092] The hub 1214 may have a constant / persistent or intermittent connection to the network node 1210b. The hub 1214 may also allow for a different communication scheme and / or schedule between the hub 1214 and UEs (e.g., UE 1212c and / or 1212d), and between the hub 1214 and the core network 1206. In other examples, the hub 1214 is connected to the core network 1206 and / or one or more UEs via a wired connection. Moreover, the hub 1214 may be configured to connect to an M2M service provider over the access network 1204 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1210 while still connected via the hub 1214 via a wired orwireless connection. In some embodiments, the hub 1214 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 1210b. In other embodiments, the hub 1214 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1210b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0093] FIG. 13 shows a UE 1300 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0094] A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller).Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0095] The UE 1300 includes processing circuitry 1302 that is operatively coupled via a bus 1304 to an input / output interface 1306, a power source 1308, a memory 1310, a communication interface 1312, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in FIG. 13. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0096] The processing circuitry 1302 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1310. The processing circuitry 1302 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 1302 may include multiple central processing units (CPUs).

[0097] In the example, the input / output interface 1306 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1300. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0098] In some embodiments, the power source 1308 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 1308 may further include power circuitry for delivering power from the power source 1308 itself, and / or an external power source, to the various parts of the UE 1300 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1308. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1308 to make the power suitable for the respective components of the UE 1300 to which power is supplied.

[0099] The memory 1310 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1310 includes one or more application programs 1314, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1316. The memory 1310 may store, for use by the UE 1300, any of a variety of various operating systems or combinations of operating systems.

[0100] The memory 1310 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory 1310 may allow the UE 1300 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 1310, which may be or comprise a device-readable storage medium.

[0101] The processing circuitry 1302 may be configured to communicate with an access network or other network using the communication interface 1312. The communication interface 1312 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1322. The communication interface 1312 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1318 and / or a receiver 1320 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1318 and receiver 1320 may be coupled to one or more antennas (e.g., antenna 1322) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0102] In the illustrated embodiment, communication functions of the communication interface 1312 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, near-field communication, location-basedcommunication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / intemet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0103] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1312, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0104] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

[0105] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the formof an loT device comprises circuitry and / or software in dependence of the intended application of the loT device in addition to other components as described in relation to the UE 1300 shown in FIG. 13.

[0106] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3 GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0107] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0108] FIG. 14 shows a network node 1400 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs), NR NodeBs (gNBs)), O-RAN nodes, or components of an O-RAN node (e.g., intelligent controller, O-RU, O-DU, O-CU).

[0109] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0110] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0111] The network node 1400 includes a processing circuitry 1402, a memory 1404, a communication interface 1406, and a power source 1408. The network node 1400 may be composed of multiple physically separate components (e.g., aNodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 1400 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 1400 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1404 for different RATs) and some components may be reused (e.g., a same antenna 1410 may be shared by different RATs). The network node 1400 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1400, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1400.

[0112] The processing circuitry 1402 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 1400 components, such as the memory 1404, to provide network node 1400 functionality.

[0113] In some embodiments, the processing circuitry 1402 includes a system on a chip (SOC). In some embodiments, the processing circuitry 1402 includes one or more of radio frequency (RF) transceiver circuitry 1412 and baseband processing circuitry 1414. In some embodiments, the radio frequency (RF) transceiver circuitry 1412 and the baseband processing circuitry 1414 may be on separate chips (or sets of chips), boards, or units, such as radio unitsand digital units. In alternative embodiments, part or all of RF transceiver circuitry 1412 and baseband processing circuitry 1414 may be on the same chip or set of chips, boards, or units.

[0114] The memory 1404 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 1402. The memory 1404 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 1402 and utilized by the network node 1400. The memory 1404 may be used to store any calculations made by the processing circuitry 1402 and / or any data received via the communication interface 1406. In some embodiments, the processing circuitry 1402 and memory 1404 is integrated.

[0115] The communication interface 1406 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface 1406 comprises port(s) / terminal(s) 1416 to send and receive data, for example to and from a network over a wired connection. The communication interface 1406 also includes radio front-end circuitry 1418 that may be coupled to, or in certain embodiments a part of, the antenna 1410. Radio front-end circuitry 1418 comprises filters 1420 and amplifiers 1422. The radio front-end circuitry 1418 may be connected to an antenna 1410 and processing circuitry 1402. The radio front-end circuitry may be configured to condition signals communicated between antenna 1410 and processing circuitry 1402. The radio front-end circuitry 1418 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1418 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1420 and / or amplifiers 1422. The radio signal may then be transmitted via the antenna 1410. Similarly, when receiving data, the antenna 1410 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1418. The digital data may be passed to the processing circuitry 1402. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0116] In certain alternative embodiments, the network node 1400 does not include separate radio front-end circuitry 1418, instead, the processing circuitry 1402 includes radio front-end circuitry and is connected to the antenna 1410. Similarly, in some embodiments, all or some ofthe RF transceiver circuitry 1412 is part of the communication interface 1406. In still other embodiments, the communication interface 1406 includes one or more ports or terminals 1416, the radio front-end circuitry 1418, and the RF transceiver circuitry 1412, as part of a radio unit (not shown), and the communication interface 1406 communicates with the baseband processing circuitry 1414, which is part of a digital unit (not shown).

[0117] The antenna 1410 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 1410 may be coupled to the radio front-end circuitry 1418 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 1410 is separate from the network node 1400 and connectable to the network node 1400 through an interface or port.

[0118] The antenna 1410, communication interface 1406, and / or the processing circuitry 1402 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna 1410, the communication interface 1406, and / or the processing circuitry 1402 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0119] The power source 1408 provides power to the various components of network node 1400 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1408 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1400 with power for performing the functionality described herein. For example, the network node 1400 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 1408. As a further example, the power source 1408 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0120] Embodiments of the network node 1400 may include additional components beyond those shown in FIG. 14 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 1400 may include user interface equipment to allow input of information into the network node 1400 and to allowoutput of information from the network node 1400. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1400.

[0121] FIG. 15 is a block diagram of a host 1500, which may be an embodiment of the host 1216 of FIG. 12, in accordance with various aspects described herein. As used herein, the host 1500 may be or comprise various combinations hardware and / or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 1500 may provide one or more services to one or more UEs.

[0122] The host 1500 includes processing circuitry 1502 that is operatively coupled via a bus 1504 to an input / output interface 1506, a network interface 1508, a power source 1510, and a memory 1512. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as FIGS. 13 and 14, such that the descriptions thereof are generally applicable to the corresponding components of host 1500.

[0123] The memory 1512 may include one or more computer programs including one or more host application programs 1514 and data 1516, which may include user data, e.g., data generated by a UE for the host 1500 or data generated by the host 1500 for a UE. Embodiments of the host 1500 may utilize only a subset or all of the components shown. The host application programs 1514 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs 1514 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 1500 may select and / or indicate a different host for over-the-top services for a UE. The host application programs 1514 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

[0124] FIG. 16 is a block diagram illustrating a virtualization environment 1600 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relatesto an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1600 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1600 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an 0-2 interface.

[0125] Applications 1602 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0126] Hardware 1604 includes processing circuitry, memory that stores software and / or instructions executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1606 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1608a and 1608b (one or more of which may be generally referred to as VMs 1608), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 1606 may present a virtual operating platform that appears like networking hardware to the VMs 1608.

[0127] The VMs 1608 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1606. Different embodiments of the instance of a virtual appliance 1602 may be implemented on one or more of VMs 1608, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0128] In the context of NFV, a VM 1608 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 1608, and that part of hardware 1604 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, formsseparate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1608 on top of the hardware 1604 and corresponds to the application 1602.

[0129] Hardware 1604 may be implemented in a standalone network node with generic or specific components. Hardware 1604 may implement some functions via virtualization. Alternatively, hardware 1604 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1610, which, among others, oversees lifecycle management of applications 1602. In some embodiments, hardware 1604 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1612 which may alternatively be used for communication between hardware nodes and radio units.

[0130] FIG. 17 shows a communication diagram of a host 1702 communicating via a network node 1704 with a UE 1706 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE 1212a of FIG. 12 and / or UE 1300 of FIG. 13), network node (such as network node 1210a of FIG. 12 and / or network node 1400 of FIG. 14), and host (such as host 1216 of FIG. 12 and / or host 1500 of FIG. 15) discussed in the preceding paragraphs will now be described with reference to FIG. 17.

[0131] Like host 1500, embodiments of host 1702 include hardware, such as a communication interface, processing circuitry, and memory. The host 1702 also includes software, which is stored in or accessible by the host 1702 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 1706 connecting via an over-the-top (OTT) connection 1750 extending between the UE 1706 and host 1702. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection 1750.

[0132] The network node 1704 includes hardware enabling it to communicate with the host 1702 and UE 1706. The connection 1760 may be direct or pass through a core network (like core network 1206 of FIG. 12) and / or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

[0133] The UE 1706 includes hardware and software, which is stored in or accessible by UE 1706 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE 1706 with the support of the host 1702. In the host 1702, an executing host application may communicate with the executing client application via the OTT connection 1750 terminating at the UE 1706 and host 1702. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 1750 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 1750.

[0134] The OTT connection 1750 may extend via a connection 1760 between the host 1702 and the network node 1704 and via a wireless connection 1770 between the network node 1704 and the UE 1706 to provide the connection between the host 1702 and the UE 1706. The connection 1760 and wireless connection 1770, over which the OTT connection 1750 may be provided, have been drawn abstractly to illustrate the communication between the host 1702 and the UE 1706 via the network node 1704, without explicit reference to any intermediary devices and the precise routing of messages via these devices.

[0135] As an example of transmitting data via the OTT connection 1750, in step 1708, the host 1702 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 1706. In other embodiments, the user data is associated with a UE 1706 that shares data with the host 1702 without explicit human interaction. In step 1710, the host 1702 initiates a transmission carrying the user data towards the UE 1706. The host 1702 may initiate the transmission responsive to a request transmitted by the UE 1706. The request may be caused by human interaction with the UE 1706 or by operation of the client application executing on the UE 1706. The transmission may pass via the network node 1704, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 1712, the network node 1704 transmits to the UE 1706 the user data that was carried in the transmission that the host 1702 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1714, the UE 1706 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 1706 associated with the host application executed by the host 1702.

[0136] In some examples, the UE 1706 executes a client application which provides user data to the host 1702. The user data may be provided in reaction or response to the data received from the host 1702. Accordingly, in step 1716, the UE 1706 may provide user data, which maybe performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input / output interface of the UE 1706. Regardless of the specific manner in which the user data was provided, the UE 1706 initiates, in step 1718, transmission of the user data towards the host 1702 via the network node 1704. In step 1720, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 1704 receives user data from the UE 1706 and initiates transmission of the received user data towards the host 1702. In step 1722, the host 1702 receives the user data carried in the transmission initiated by the UE 1706.

[0137] One or more of the various embodiments improve the performance of OTT services provided to the UE 1706 using the OTT connection 1750, in which the wireless connection 1770 forms the last segment. More precisely, the teachings of these embodiments may enable selftuning procedures to be performed by amplified optical systems.

[0138] In an example scenario, factory status information may be collected and analyzed by the host 1702. As another example, the host 1702 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host 1702 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host 1702 may store surveillance video uploaded by a UE. As another example, the host 1702 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host 1702 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and / or transmitting data.

[0139] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1750 between the host 1702 and UE 1706, in response to variations in the measurement results. The measurement procedure and / or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host 1702 and / or UE 1706. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 1750 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1750 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter theoperation of the network node 1704. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host 1702. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 1750 while monitoring propagation times, errors, etc.

[0140] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0141] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to theprocessing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

Claims

CLAIMSWhat is claimed is:

1. A method of operating a first optical transceiver to enable loss of signal, LOS, detection, the method comprising: transmitting (810) an optical signal including an optical marker toward a second optical transceiver via an optical communication path; receiving (820) an indication that the second optical transceiver failed to receive the optical marker; and determining (830) that a LOS associated with the optical signal occurred based on the indication that the second optical transceiver failed to receive the optical marker.

2. The method of Claim 1, wherein transmitting the optical signal comprises periodically transmitting a predetermined message as part of a communication channel.

3. The method of Claim 1, wherein transmitting the optical signal comprises transmitting the optical signal using line coding to create transitions at a fixed rate.

4. The method of any of Claims 2-3, wherein the communication channel is associated with remote diagnostic monitoring, and wherein the optical marker is a failure alarm of the communication channel.

5. The method of any of Claims 1-4, wherein the optical communication path includes an optical power amplifier.

6. The method of Claim 5, further comprising: responsive to determining that the LOS associated with the optical signal occurred, performing (840) a self-tuning procedure that includes adjusting a bit rate of optical signal transmissions.

7. The method of Claim 6, wherein the optical power amplifier is configured with a transient suppression mechanism with a minimum transient speed, and wherein performing the self-tuning procedure further includes adjusting the bit rate of subsequent optical signal transmissions to account for the transient suppression mechanism.

8. A method of operating a first optical transceiver to perform a self-tuning procedure, the method comprising: transmitting (910) a first optical signal toward a second optical transceiver using a first bit rate; receiving (920) an indication of a loss of signal, LOS, associated with the first optical signal from the second optical transceiver; responsive to receiving the indication of the LOS, transmitting (930) a second optical signal toward the second optical transceiver using a second bit rate that is different than the first bit rate; and responsive to determining that the second optical signal was successfully received by the second optical transceiver, selecting (940) the second bit rate to be used for transmission of subsequent optical signals.

9. The method of Claim 8, wherein transmitting the second optical signal comprises: transmitting a plurality of optical signals, each optical signal of the plurality of optical signals being transmitted at a bit rate that is higher than a bit rate of an immediately previously transmitted optical signal; and receiving an indication of a LOS associated with each optical signal of the plurality of optical signals except for the second optical signal.

10. The method of any of Claims 8-9, wherein the first bit rate is a predetermined minimum bit rate, and wherein transmitting the first optical signal comprises transmitting the first optical signal toward the second optical transceiver in response to at least one of: the first optical transceiver and the second optical transceiver entering an ON state.

11. The method of any of Claims 8-10, further comprising any of the operations of Claims 1- 7.

12. A method of operating a second optical transceiver to enable loss of signal, LOS, detection, the method comprising: receiving (1010) an optical signal from an optical communication path associated with a first optical transceiver; determining (1020) whether the optical signal includes an optical marker; andtransmitting (1030) an indication of whether the optical signal includes the optical marker to the first optical transceiver.

13. The method of Claim 12, wherein determining whether the optical signal includes the optical marker comprises determining whether the optical signal comprises a predetermined message as part of a communication channel.

14. The method of Claim 12, wherein determining whether the optical signal includes the optical marker comprises determining whether the optical signal comprises transitions at a predetermined rate in a communication channel.

15. The method of any of Claims 13-14, wherein the communication channel is associated with remote diagnostic monitoring, and wherein the optical marker is a failure alarm of the communication channel.

16. The method of any of Claims 12-15, wherein the optical communication path includes an optical power amplifier.

17. The method of Claim 16, further comprising: responsive to transmitting an indication that the optical signal fails to include the optical marker, performing (1040) a self-tuning procedure that includes receiving subsequent optical signals from the first optical transceiver at an adjusted bit rate.

18. The method of Claim 17, wherein the optical power amplifier is configured with a transient suppression mechanism with a minimum transient speed, wherein performing the self-tuning procedure further includes receiving subsequent optical signals from the first optical transceiver at a bit rate adjusted for the transient suppression mechanism.

19. A method of operating a second optical transceiver to perform a self-tuning procedure, the method comprising: receiving (1110) a first optical signal from an optical communication path associated with a first optical transceiver using a first bit rate; transmitting (1120) an indication of a loss of signal, LOS, associated with the first optical signal to the first optical transceiver;responsive to transmitting the indication of the LOS, receiving (1130) a second optical signal from the optical communication path using a second bit rate that is greater than the first bit rate; and responsive to determining that the second optical signal was successfully received, selecting (1040) the second bit rate to be used for reception of subsequent optical signals.

20. The method of Claim 19, wherein receiving the second optical signal comprises: receiving a plurality of optical signals, each optical signal of the plurality of optical signals using a bit rate that is higher than a bit rate of an immediately previously received optical signal; and transmitting an indication of a LOS associated with each optical signal of the plurality of optical signals except for the second optical signal.

21. The method of any of Claims 19-20, wherein the first bit rate is a predetermined minimum bit rate, and wherein receiving the first optical signal comprises receiving the first optical signal in response to at least one of: the first optical transceiver and the second optical transceiver entering an ON state.

22. The method of any of Claims 19-21, further comprising any of the operations of Claims 12-18.

23. A network node (300, 1400), the network node comprising: processing circuitry (330, 1402); and memory (340, 1404) coupled to the processing circuitry and having instructions stored therein that are executable by the processing circuitry to cause the network node to perform operations comprising any of the operations of Claims 1-22.

24. A computer program comprising program code to be executed by processing circuitry (330, 1402) of a network node (300, 1400), whereby execution of the program code causes the network node to perform operations comprising any operations of Claims 1-22.

25. A computer program product comprising a non-transitory storage medium (340, 1404) including program code to be executed by processing circuitry (330, 1402) of a network node (300, 1400), whereby execution of the program code causes the network node to performoperations comprising any operations of Claims 1-22.

26. A non-transitory computer-readable medium having instructions stored therein that are executable by processing circuitry (330, 1402) of a network node (300, 1400) to cause the network node to perform operations comprising any of the operations of Claims 1-22.

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