Methods and appartuses for controlling power consumption in an optical network

Abstract

Apparatus and methods performed by a first network node and a second network node in an optical network for switching on again the first network node that has previously been fully switched off and put in a second mode of operation, wherein the power consumption of the first network node is reduced to zero, are disclosed herein. A first network node a power supply circuit for supplying power to a network node in an optical network, the power supply circuit comprising an output (155) configured to provide power to the network node, a first switch control element (702) configured to selectively couple a first voltage, V1, to the output (155), wherein the first switch control element (702) is configured to couple the first voltage V1 to the output (155) when a second voltage, V2, is applied to the first switch control element (702), and a Near Field Communication, NFC, device (160), wherein the NFC device (160) is configured to, responsive to a first signal being induced in the NFC device (160), apply the second voltage V2 to the first switch control element (702).

Description

[0001] METHODS AND APPARTUSES FOR CONTROLLING POWER CONSUMPTION IN AN OPTICAL NETWORK

[0002] TECHNICAL FIELD

[0003] The present disclosure relates, in general, to wireless communications and, more particularly, systems and methods for transitioning a network node between a first mode of operation which utilises non-zero power and a second mode of operation which utilises zero power.

[0004] BACKGROUND

[0005] Energy consumption in mobile networks has increased over time. Each new mobile generation has resulted in a similar increase in energy consumption to the previous mobile generation. A well-known challenge is to improve the planning, deployment and operation of mobile networks to break the upgoing trajectory of energy consumption.

[0006] Current radio units (RUs) have many different energy saving modes, wherein radio units may use the energy saving modes to save energy for short periods. For example, radio units may use energy saving modes to save energy for periods with less traffic during normal operation.

[0007] Energy saving modes may include, for example, MIMO / Massive-MIMO Sleep, Booster Carrier Sleep, Micro Sleep and Milli Sleep modes. A further example of an energy saving mode is a Deep Sleep (DS) mode, wherein the radio unit may be in a mode of operation that is near to turned off (e.g. close to, but not zero power) over a longer period.

[0008] SUMMARY

[0009] There currently exist certain challenges.

[0010] A wake-up procedure comprises returning the radio unit to a normal operating mode from an energy saving mode. When radio units are in Deep Sleep mode, they are still active enough, in other words still consuming some power, in order to be able to wake-up when a remote BaseBand (BB) function requires. This consumes energy even when the radio unit is in Deep Sleep. This energy consumption may, for example, be in the range of 20- 30W.

[0011] One proposal is a timer based Deep Sleep mode, wherein the power consumption may be reduced to approximately 5W. However, the radio unit may only wake-up after a predefined time, wherein this pre-defined time is set when the radio unit goes into Deep Sleep. In this proposal, therefore, the radio unit cannot be woken-up before the timer has expired.

[0012] Thus, there is a need for a solution which can at any time wake-up a radio unit that is using an energy saving mode, wherein the power consumption of the radio unit during the energy saving mode is reduced to zero.

[0013] According to some embodiments there is therefore provided a first network node comprising a power supply circuit for supplying power to the first network node, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilizing zero power. The first network node comprising an optical connector socket configured to receive an optical connector. The power supply circuit comprises an output (155) configured to provide power to the first network node in the first mode of operation; and a Near Field Communication, NFC, device (160), wherein the NFC device (160) is configured to, responsive to a first signal being induced in the NFC device (160) from the optical connector, initiate the power supply circuit to provide power to the first network node.

[0014] According to some embodiments there is provided an optical connector for initiating a power supply circuit in a first network node to provide power to the first network node, the optical connector configured for input into an optical connector socket of the first network node. The optical connector comprises a power control circuit. The power control circuit comprises an input (601) configured to receive a first optical signal (106); an energy conversion apparatus (602) selectively coupled to the input (601), wherein the energy conversion apparatus (602) is configured to convert the first optical signal (106) into electrical energy; and a Near Field Communication, NFC, device (190), wherein the power control circuit is configured to utilise the electrical energy to generate a first signal across the NFC device (190). According to some embodiments there is provided a method performed by a first network node in an optical network, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The first network node requires a threshold amount of energy to perform a transition from the second mode of operation to the first mode of operation. The method comprises when the first network node is operating in the second mode of operation, receiving (210) a first signal comprising a first amount of energy greater than or equal to the threshold amount of energy; and entering (220) the first mode of operation using the first amount of energy to perform the transition from the second mode of operation to the first mode of operation.

[0015] According to some embodiments there is provided a method performed by a second network node in an optical network, wherein the second network node is in communication with a first network node configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The method comprises when the first network node is operating in the second mode of operation, responsive to obtaining an indication that the first network node is required to operate in the first mode of operation, transmitting (420), to the first network node, a first optical signal comprising a first amount of optical energy.

[0016] According to some embodiments there is provided a first network node in an optical network, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The first network node comprises processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the first network node is operable to: when the first network node is operating in the second mode of operation, receive a first signal comprising a first amount of energy; and enter the first mode of operation using the first amount of energy to perform the transition from the second mode of operation to the first mode of operation.

[0017] According to some embodiments there is provided a second network node in an optical network, wherein the second network node is in communication with a first network node configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The second network node comprises processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the second network node is operable to: when the first network node is operating in the second mode of operation, and responsive to obtaining an indication that the first network node is required to operate in the first mode of operation, transmit (420), to the first network node, a first optical signal comprising an first amount of optical energy.

[0018] According to some embodiments there is provided computer program, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out any of the methods described above.

[0019] According to some embodiments there is provided a computer-readable medium comprising instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods described above.

[0020] According to some embodiments there is provided a computer program product comprising non transitory computer readable media having stored thereon a computer program as described above.

[0021] Analogous computer programs, carriers, computer-readable media and computer program products are provided in other embodiments.

[0022] Certain embodiments may provide one or more of the following technical advantages. For example, a technical advantage may be that the radio unit consumes zero energy while the radio unit is using an energy saving mode. As another example, a technical advantage may be that the radio unit may be woken-up at any time during the period in which the radio unit is using the energy saving mode. As another example, a technical advantage may be that the embodiments provide a simple adaptation to current equipment practice and no additional cabling may be required.

[0023] Other advantages may be readily apparent to one having skill in the art. Certain embodiments may have none, some, or all of the recited advantages.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1a illustrates an example architecture of a radio unit in communication with a Baseband unit in an optical network. Figure 1 b illustrates an example implementation of parts of the example architecture of Figure 1a.

[0026] Figure 1 c illustrates an example of a radio unit, wherein the radio unit comprises 4 optical connector sockets.

[0027] Figure 2 is a flow diagram showing an example method performed by a first network node in an optical network for transitioning from a second mode of operation to a first mode of operation..

[0028] Figure 3 is a flow diagram illustrating steps in another example method performed by a first network node in an optical network for switching from the second mode of operation to the first mode of operation..

[0029] Figure 4 is a flow diagram showing an example method performed by a second network node in an optical network for switching a first network node from a second mode of operation to a first mode of operation.

[0030] Figure 5 is a flow diagram illustrating steps in another example method performed by a second network node in an optical network for switching a first network node from a first mode of operation to a second mode of operation.

[0031] Figure 6a illustrates a first network node according to some embodiments;

[0032] Figure 6b illustrates an optical connector according to some embodiments;

[0033] Figure 7 illustrates an example of a power supply circuit.

[0034] Figure 8 illustrates a functional working diagram of the behaviour of a Power Supply Unit (power supply circuit 150) in a Radio Unit (RU).

[0035] Figure 9 illustrates a network node comprising processing circuitry (or logic);

[0036] Figure 10 is a block diagram illustrating a first network node according to some embodiments;

[0037] Figure 11 is a block diagram illustrating a second network node according to some embodiments.

[0038] DETAILED DESCRIPTION

[0039] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0040] The following sets forth specific details, such as particular embodiments or examples for purposes of explanation and not limitation. It will be appreciated by one skilled in the art that other examples may be employed apart from these specific details. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and / or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc.) and / or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Nodes that communicate using the air interface may have suitable radio communications circuitry. Moreover, where appropriate the technology can additionally be considered to be embodied entirely within any form of computer- readable memory, such as (ROM, EEPROM, Flash memory, a memory disc, RAM etc.) solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

[0041] Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analogue) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and / or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

[0042] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. Although particular problems and solutions may be described using new radio (NR) terminology, it should be understood that the same solutions apply to long term evolutions (LTE) and other wireless networks as well, where applicable.

[0043] Figure 1a illustrates an example network architecture 100 wherein certain embodiments may be applied. The example network architecture 100 of Figure 1a comprises a radio unit (RU) 110 connected to a main site through an optical fiber 140. In the example network architecture 100, the main site is a Baseband (BB) unit 120 which controls the RU 110 using an optical fiber interconnection 140. The remote RU 110 is managed by a Network Manager (NM) 130, connected to the BB unit 120, wherein the NM 130 may be connected to the BB unit 120, for example, through an Embedded Control Signal (ECS) which is embedded into a data stream to the RU 110.

[0044] In some examples, the network architecture may further comprise a relay node 145 coupled between the BB unit 120 and the RU 110.

[0045] In this example architecture, the BB unit 120 may determine that a specific RU 110 is no longer needed or not needed for at least a threshold period of time. For example, the BB unit 120 may determine that a specific RU 110 is no longer needed according to a certain period of the day, wherein radio coverage from the RU 110 is not needed for that certain period of the day. In other examples, the BB unit 120 may determine that a specific RU 110 is no longer needed according to a certain period of the week, wherein radio coverage from the RU 110 is not needed for that certain period of the week. For example, the BB unit 120 may determine that radio coverage is not needed for a period of the day or week wherein traffic is reduced, e.g. radio coverage for a mall during nighttime or sporting events during the weekend. Hence, the BB unit 120 may determine that the RU 110 may be switched off for a particular time period, wherein, for example, the time period is a number of hours in a day, a number of days in a month or another time period. The BB unit 120 may send a Power-Off command to the RU 110 via the ECS (in some examples via the relay node 145) . Consequently, the RU 110 may autonomously, without manual intervention, execute a complete power off commutation. Hence, a Power Supply Unit (power supply circuit 150) of the RU 110 may disconnect from the power supply. The RU 110 may then be considered to be operating in a Power-Off mode of operation.

[0046] As discussed above, a challenge is how to wake up the RU 110 when the BB unit 120 decides that the RU 110 is once again required in the network, since any optical transceivers belonging to the RU 110 are also switched off and cannot receive any control signal. Certain aspects of the present disclosure and their embodiments may provide solutions to these challenges mentioned above or other challenges.

[0047] Certain embodiments disclosed herein describe methods and apparatuses for switching on again a radio unit that has previously been fully switched off and Power-Off mode, wherein the power consumption of the radio unit is reduced to zero. In some embodiments, downlink optical power is used to implement a wake-up mechanism, wherein a continuous optical signal may be sent from the BB unit 120 toward the RU 110 consequently providing, in conjunction with the wake-up command itself, the energy required to activate the RU 110 wake up process.

[0048] Herein, a Power-Off mode of operation, in which the power consumption of a network node is reduced to zero may be referred to as a second mode of operation. Any other mode of operation, for example a full power or any suitable sleep mode, in which at least some power consumption is required by a network node may be referred to herein as a first mode of operation.

[0049] Figure 1b illustrates an example implementation of parts of the network architecture 100 in more detail. As can be seen in Figure 1 b, the RU 110 may comprise a power supply circuit 150 which comprises a first NFC device 160. An optical connector 170 (e.g. a Full AXS Connector) may connect the RU 110 to optical fiber that couples to the BB unit 120. The optical connector 170 may comprise a power control circuit 180 comprising a second NFC 190.

[0050] Example embodiments of the power supply circuit 150 and the power control circuit 180 will be described in more detail with reference to Figures 6b and 7.

[0051] Figure 1c illustrates an example of a radio unit comprising 4 optical connector sockets 109a to 109b. Each optical connector socket 109a to 109b is associated with a power supply circuit having an associated first NFC device 160a to 160d. Each optical connector socket may then be configured to receive a respective optical connector 170a to 170d wherein each optical connector 170a to 170d comprises a power control circuit having a respective second NFC device 190a to 190d.

[0052] In particular, the right hand side of Figure 1c illustrates where the first NFC devices 160a to 160d and second NFC devices 190a to 190d (one for each data connector, and wherein only second NFC devices 190c and 190d are visible in Figure 1c) need to be physically accommodated to enter into the near field range (within 5 / 10 cm) foreseen by the NFC radio signal. In this example, the first NFC devices 160a to 160d are positioned above each FullAXS connector (four in the example of the picture), just beside the RU box (which is usually made of aluminum and does not disturb the NCF inductive coupling). The connector positioning is constrained and so the two coupled solenoids (reader and tag) can be positioned on the plug and above the RU socket so to guarantee the maximum inductive coupling and the maximum energy transfer. Figure 2 depicts a flow diagram showing an example method 200 performed by a first network node in an optical network wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The first network node may require a threshold amount of energy to perform a transition from the second mode of operation to the first mode of operation. The method of Figure 2 may be performed to transition the first network node from operating in the second mode of operation to operating in the first mode of operation.

[0053] For example, the method 200 of Figure 2 may be performed by the RU 110 illustrated in Figures 1a and 1 b and 1c.

[0054] The first network node may comprise a physical or virtual node, and may be implemented in a computing device or server apparatus and / or in a virtualized environment, for example in a cloud, edge cloud or fog deployment.

[0055] As illustrated in Figure 1 b and 1 c, the RU 110 may comprise a power supply circuit 150, wherein the power supply circuit 150 supplies power to the RU 110. For example, when the RU 110 is operating in the first mode of operation, the RU 110 may be connected to receive power from the power supply circuit 150, and when the RU 110 is operating in the second mode of operation, the RU 110 may be disconnected from the power supply circuit 150.

[0056] As illustrated in Figure 1 b, the power supply circuit 150 may comprise the first NFC device 160, wherein the first NFC device 160 is configured to receive and transmit signals. In some embodiments, the first NFC device is configured to receive signals from the second NFC device 190 and to transmit signals to the second NFC device 190. In some embodiments, the first NFC device 160 receiving a signal from the second NFC device 190 comprises the signal being induced in the first NFC device 160 (and vice versa). In some embodiments, the second NFC device 190 is configured to be within a near field range of the first NFC device 160. For example, the near field range may be a range of 5 cm to 10 cm. In some embodiments, the threshold energy to transition between the second mode of operation and the first mode of operation corresponds to a minimum voltage required to switch on the power supply circuit 150.

[0057] The method 200 begins at step 210 wherein, when the first network node is operating in the second mode of operation, the first network node receives a first signal comprising a first amount of energy. The first amount of energy may be greater than or equal to the threshold amount of energy.

[0058] It will be appreciated that the first signal may be received via the first NFC device 160 comprised within the power supply circuit 150 In some embodiments, the first signal is induced in the first NFC device (e.g. by the second NFC device 190 in the optical connector 180 connected to the RU 110). For example, the first signal may be induced as illustrated by the arrow 105 in Figure 1 b.

[0059] In step 220, the first network node enters the first mode of operation using the first amount of energy to perform the transition from the second mode of operation to the first mode of operation.

[0060] For example, the first NFC device 160 may be configured to use the energy of first signal 105 to switch on the power supply circuit 150. For example, the first NFC device 160 may be configured to apply the minimum voltage to the 150 power supply circuit 150 using the first amount of energy contained in the first signal 105.

[0061] An example of how the power supply circuit 150 may be designed to enable performance of step 220 is described later with reference to Figure 7.

[0062] Figure 3 depicts a flow diagram illustrating an example of a method 300 performed by a first network node in an optical network for transitioning the first network node from operating in the first mode of operation to operating in the second mode of operation.

[0063] The method 300 of Figure 3 may be performed by a first network node in an optical network, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. For example, the method 300 of Figure 3 may be performed by the RU 110 illustrated in Figures 1a and 1 b. The first network node may comprise a physical or virtual node, and may be implemented in a computing device or server apparatus and / or in a virtualized environment, for example in a cloud, edge cloud or fog deployment.

[0064] It will be appreciated that the first network node may be configured to perform the method of Figure 2 to switch from the second mode of operation to the first mode of operation, and the method of Figure 3 to switch from the first mode of operation to the second mode of operation.

[0065] In step 310, when the first network node is operating in the first mode of operation, the first network node receives a first optical signal, wherein the first optical signal comprises an indication to enter the second mode of operation.

[0066] In some embodiments, the RU 110 receives the first optical signal of step 310 from the BB unit 120, for example, as illustrated by the arrow 106 in Figure 1 b. The first optical signal 106 may comprise a control signal from the BB unit 120 to switch off the RU 110. For example, the first optical 106 signal of step 310 may be received from a second network node 120 via an optical connector 170.

[0067] In step 320, responsive to receiving the indication to enter the second mode of operation, the first network node enters the second mode of operation. For example, the second mode of operation may be entered at least in part by the RU generating a second signal in the NFC device 160, as will be described in more detail below with reference to Figure 7.

[0068] Figure 4 depicts a flow diagram showing an example method 400 performed by a second network node in an optical network for enabling a first network node that is operating in a second mode of operation, wherein the power consumption of the first network node is reduced to zero, to transition to operating in a first mode of operation (e.g. a non-zero power mode of operation) according to certain embodiments.

[0069] The method 400 of Figure 4 may be performed by a second network node in an optical network, wherein the second network node is in communication with a first network node configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The first network node may require a threshold amount of energy perform a transition between the first mode of operation and the second mode of operation.

[0070] In some embodiments, the second network node may be a controller node (e.g. controller node 130), a base station unit (e.g. BB unit 120) or a relay node (e.g. relay node 145) coupled between the RU 110 and BB unit 120. It will be appreciated that the second network node may comprise a physical or virtual node, and may be implemented in a computing device or server apparatus and / or in a virtualized environment, for example in a cloud, edge cloud or fog deployment.

[0071] It will be appreciated that the first network node in communication with the second network node may be configured to perform the method of Figure 2 and / or Figure 3.

[0072] On commencing the method of Figure 4 it will be appreciated that the first network node may be operating in the second mode of operation.

[0073] The method 400 may begin at step 410 in which the first network node may obtain an indication that the first network node is required to operate in a first mode of operation. In some examples, step 410 comprises receiving the indication that the first network node is required to operate in the first mode of operation from a controller network node. In these examples, the second network node may comprise a relay node (e.g. relay node 145) coupled between the RU 110 and the BB unit 120 (which in this example may comprise a controller node).

[0074] In other examples, step 410 comprises determining that the first network node is required to operate in the first mode of operation. In this example, the second network node may comprise the BB unit 120.

[0075] In step 420, responsive to obtaining an indication that the first network node is required to operate in the first mode of operation, the second network node transmits, to the first network node, a first optical signal comprising a first amount of optical energy, for example, greater than or equal to the threshold amount of energy. By transmitting the first optical signal with enough energy (e.g. greater than equal to the threshold amount of energy) to the first network node, performing step 420 provides the first network node with the required energy to transition from the second mode of operation to the first mode of operation, without the first network node requiring any power from its own power source.

[0076] In some examples, of step 420 transmits the first optical signal is transmitted by the second network node until the energy transmitted is greater than or equal to a predetermined threshold energy.

[0077] In some examples of step 420, the second network node transmits the first optical signal until it receives a second optical signal (e.g. as indicated by the arrow 107 in Figure 1 b) from the first network node comprising an indication that the first network node has transitioned into the first mode of operation. It will be appreciated that the first network node would not be able to generate an optical signal when operating in the second mode of operation, and so therefore the presence of the second optical signal 107 in itself may indicate implicitly to the second network node that the first network node has entered the first mode of operation.

[0078] In examples in which the second network node comprises a relay node, the second network node may receive a command from the controller network node in step 410, and this command may in some circumstances comprise less than the threshold amount of energy. However, in performing step 420, the relay node may ensure that the threshold amount of energy is provided to the first network node in order to enable the first network node to make the transition from the second mode of operation to the first mode of operation.

[0079] Figure 5 is a flow diagram illustrating steps in another example method 500 performed by a second network node in an optical network for enabling a first network node that is operating in a first mode of operation to transition to operating in a first mode of operation according to certain embodiments.

[0080] The method 500 of Figure 5 may be performed by a second network node in an optical network, wherein the second network node is in communication with a first network node configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power.

[0081] In some embodiments, the second network node may be a controller node (e.g. controller node 130), a base station unit (e.g. BB unit 120) or a relay node (e.g. relay node 145) coupled between the RU 110 and BB unit 120. It will be appreciated that the second network node may comprise a physical or virtual node, and may be implemented in a computing device or server apparatus and / or in a virtualized environment, for example in a cloud, edge cloud or fog deployment.

[0082] It will be appreciated that the first network node in communication with the second network node may be configured to perform the method of Figure 2 and / or Figure 3. It will also be appreciated that the second network node may be configured to perform the method of Figure 4 to transition the first network node from the second mode of operation to the first mode of operation, and the method of Figure 5 to transition the first network node from the first mode of operation to the second mode of operation.

[0083] On commencing the method of Figure 5 it will be appreciated that the first network node will be operating in the first mode of operation.

[0084] In step 510 the second network node obtains an indication that the first network node is required to operate in the second mode of operation. In some examples, step 510 comprises receiving the indication that the first network node is required to operate in the second mode of operation from a controller network node. In these examples, the second network node may comprise a relay node (e.g. relay node 145) coupled between the RU 110 and the BB unit 120 (which in this example may comprise a controller node).

[0085] In other examples, step 510 comprises determining that the first network node is required to operate in the second mode of operation. In this example, the second network node may comprise the BB unit 120.

[0086] In step 520, responsive to obtaining the indication in step 510, the second network node transmits, to the first network node, an indication that the first network node is to enter the second mode of operation.

[0087] In step 530, after transmitting the indication, the second network node refrains from transmitting any optical signal to the first network node until obtaining an indication that the first network node is required to operate in the first mode of operation (e.g. until step 410 of Figure 4 occurs). By refraining from transmitting any optical signal to the first network node, the method may ensure that the second network node doesn’t inadvertently transition the first network node back to the first mode of operation (e.g. by providing energy to the power supply circuit 150 via the NFC devices 190 and 160).

[0088] Figure 6a illustrates a first network node 110 according to some embodiments. The first network node may comprise the RU 110 illustrated in Figures 1 a and 1 b. Corresponding features have been given corresponding reference numbers.

[0089] The first network node comprises a power supply circuit 150 for supplying power to the first network node. The first network node is configured to operate in a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. An example implementation of the power supply circuit 150 is described with reference to Figure 7.

[0090] The first network node 110 comprises an optical connector socket 165 configured to receive an optical connector (e.g. optical connector 170).

[0091] The power supply circuit 150 comprises, an output 155 configured to provide power to the first network node in the first mode of operation. The power supply circuit 150 further comprises a Near Field Communication, NFC, device 160, wherein the NFC device 160 is configured to, responsive to a first signal 105 being induced in the NFC device 160 from the optical connector, initiate the power supply circuit 150 to provide power to the first network node 110.

[0092] It will be appreciated that the NFC device 160 may be positioned within the first network node adjacent to the optical connector socket (for example as illustrated in Figure 1e). It will be appreciated that the NFC device 160 may be positioned close enough to the optical connector socket that it will be able to communicate with the NFC device 190 of the optical connector 170. In other words, the NFFC device 160 may b e positioned with in the first network node such that the first signal 105 can be induced by a second NFC device 190 in the optical connector 170.

[0093] Figure 6b illustrates an example implementation of an optical connector 170 comprising a power control circuit 180 according to some embodiments. The optical connector may be for initiating a power supply circuit (e.g. power supply circuit 150 illustrated in Figure 6a) in a first network node to provide power to the first network node.

[0094] The optical connector 170 is configured to be input into an optical connector socket (e.g. optical connector socket 165 of Figure 6a) of the first network node.

[0095] The example of Figure 6b illustrates the power control circuit 180 for a single fiber scenario, however, it will be appreciated that the same concepts may be applied for a dual fiber scenario (e.g. utilising a double switch). The optical connector 170 is configured to be coupled to an optical connector point of a radio unit.

[0096] It will however be appreciated that, whilst the elements of the power control circuit 180 are small, and could be accommodated within an optical connector, the power control circuit 180 may also be implemented as an adaptation interposed between the RU optical socket and the optical connector.

[0097] The power control circuit 180 comprises an input 601 configured to receive a first optical signal 106.

[0098] The power control circuit 180 further comprises an energy conversion apparatus 602 selectively coupled to the input 601. In this example, the energy conversion apparatus comprises a photodetector 602, and is selectively coupled to the input 601 by the switch 603. The energy conversion apparatus 602 is configured to convert the first optical signal 106 into electrical energy (when coupled to the input 601). It will be appreciated that the optical energy may be converted by the energy conversion apparatus 602 into electrical energy and stored in an energy storage apparatus (not illustrated), for example, a capacitor, as stored energy.

[0099] The power control circuit 180 may also comprise an output 605 selectively coupled to the input, wherein the output is configured to transmit an output optical signal to the radio unit, RU. It will be appreciated, that when the switch 603 is in position A, the output is configured to pass the first optical signal 106 to the radio unit. It will be appreciated that when switch 603 is in position B, the energy conversion apparatus 602 is coupled to the input 601 and is therefore configured to receive the first optical signal 106 such that the energy of the first optical signal 106 can be converted.

[0100] The power control circuit 180 may also comprise a switch control element 606, wherein the switch control element 606 is configured to control the switch 603 to selectively couple the input 601 to either the energy conversion apparatus 602 or the output 605. In other words the switch control element 606 may be configured to control the commutation of the switch from positions A to B and vice versa, and to maintain the position status of the switch.

[0101] The power control circuit 180 comprises a Near Field Communication, NFC, device 190. The power control circuit 180 is configured to utilise the electrical energy (e.g. stored by the energy storage apparatus) to generate a first signal across the NFC device 190. It will be appreciated that the NFC standard foresees an operating frequency of an NFC device of 13.56 MHz, which would not interfere with the frequencies utilised by a RU.

[0102] When the RU is in the second mode of operation, the power control circuit may be configured such that the switch is in position B. If the RU is then switched on by a BB unit, this may occur by the BB unit transmitting a first optical signal to the RU (e.g. as described above with reference to step 420 of Figure 4), via the power control circuit 180.

[0103] When the switch is in position B, the energy of the first optical signal may be converted by the energy conversion apparatus 602.

[0104] In some examples, responsive to the stored energy in the capacitor meeting a threshold condition, the power control circuit may be configured to provide the stored energy to the NFC to generate the first signal. It will be appreciated that the first signal being generated in the NFC device 190 may be used to induce the first signal in an NFC device 160 of the RU. This first signal may therefore be considered the first signal of step 210 of Figure 2.

[0105] The switch control circuit 606 may be coupled to the NFC device 190 such that when the first signal is detected across the NFC device 190 (e.g. responsive to the stored energy in the capacitor meeting a threshold condition), the switch control element 606 may be configured to control the switch 603 to be in position A. Position A of the switch 603 couples the input 601 to the output 605 and decouples the energy conversion apparatus 602 from the input 601 .

[0106] In other words, when the first signal is provided across the NFC device 190, it is understood that the RU is to operate in the first mode of operation, and that the optical signals to be received on the fiber should now be coupled to the output 605 so that they can be provided to the RU for processing.

[0107] As described above with reference to step 320, the RU may obtain an indication to enter a second mode of operation, and may then enter the second mode of operation at least in part by generating a second signal in the NFC device 160. This generation of a second signal in the NFC device 160 may then induce the second signal in the NFC device 190.

[0108] The switch control element 606 may then by configured to, responsive to the second signal being induced in the NFC device 190 control the switch to be in position B. Position B of the switch 603 decouples the input 601 from the output 605 and couples the energy conversion apparatus 602 to the input 601 .

[0109] In other words, when the second signal is induced across the NFC device 190, it is understood that the RU is to operate in the second mode of operation. The switch control element 606 therefore couples the input to the energy conversion apparatus 602 so that the RU may be effectively switched back to the first mode of operation when required.

[0110] In some scenarios, the switch 603 may inadvertently be in the wrong position. For example, when the RU is operating in the first mode of operation the switch may be inadvertently in position B, the RU may detect an induced first signal across the NFC device 160. In these circumstances, the RU may generate a third signal in the NFC device 160. This third signal may then be generated in the NFC device 190. Responsive to the third signal being induced in the NFC device 190, the switch control element may be configured to is configured to commutate the switch into position A.

[0111] As will be described in more detail below, it may be sufficient for at least one of the optical connections to induce the first signal in the NFC device 190 to restart the RU. When the RU is transitioned into the first mode of operation it may be configured to commutate the switches in the other connector plugs (connected to that RU) to position A again. Figure 7 illustrates an example of a power supply circuit 150 according to some embodiments.

[0112] It will be appreciated that the power supply circuit 150 is an example implementation, and that various elements may be interchanged with alternative circuitry elements or the configuration of the elements may be adjusted. The power supply circuit 150 may be implemented within a network node, for example, a radio unit (e.g. RU 110)

[0113] The power supply circuit 150 comprises an output 155 configured to provide power to the network node. The power supply circuit 150 further comprises a first voltage V1 (e.g. where V1 is derived from a power supply of the RU). During normal operation (e.g. the first mode of operation), the first voltage V1 is coupled to the output 155 such that power is provided to the RU.

[0114] The resistance R8 represents the radio unit power load (e.g. 1 ohm means 54 A of current, almost 3kW of electrical power consumption). It will be appreciated that the actual voltage provided across R8 may be lower than V1 (due to the potential divider caused by R8 and M1), however, the voltage across R8 is derived from the first voltage V1. It will also be appreciated that M1 may be configured such that the value of the voltage drop across M1 is small.

[0115] In Figure 7, V1 may be for example, 48V, which may be representative of the RU power supply after filters, line disturbances protections and polarity protection circuits.

[0116] In particular it will be appreciated that the power supply circuit 150 has been designed such that is it possible to disconnect the first voltage V1 from the output 155.

[0117] As described with reference to Figure 2, the power supply circuit 150 comprises an NFC device 160. The NFC device 160 is represented in Figure 7 by the voltage V4.

[0118] V4 represents the voltage generated in at least one NFC device 160 when the first signal is induced in the NFC device 160. It will be appreciated that V4 may represent the voltage produced by all of the NFC devices 160a to 160d (as illustrated in Figure 2c) mounted on all the optical data ports of the RU. In other words, the inducted current in all of the NFC devices of the RU contribute to V4 (that is all contributes must be ORed on V4). In this way the transition of the RU from the second mode of operation to the first mode of operation is possible when the current is induced on at least one NFC tag of the connectors.

[0119] The power supply circuit 150 further comprises a first switch control element 702 configured to selectively couple the first voltage V1 to the output 155, wherein the first switch control element 702 is configured to couple the first voltage V1 to the output 155 when a second voltage, V2, is applied to the first switch control element 702. In the example of Figure 7, the first switch control element 702 is implemented as a power MOSFET M1. In particular, the power MOSFET M1 may be considered to couple the first voltage V1 to the output 155 when the second voltage V2 applied to the gate of M1 is high. It will be appreciated that an alternative may be to utilise a plurality of MOSFETs in parallel to deal with a maximum current.

[0120] In some examples, the power supply circuit 150 further comprises an initiator switch RL1 . RL1 may be utilised to set the power supply circuit such that it is providing a voltage across R8 at the first instance, e.g. without requiring any voltage at V4. RL1 may therefore be set to the “close” position when, for example, the RU leaves the factory, after assembling. This guarantees the power on during the first installation even in absence of any optical power from the BaseBand.

[0121] When the RU is then first switched off, e.g. the network node comprising the power supply circuit 150 receives an indication to transition the network node into second mode of operation, the network node may commute the initiator switch RL1 into the open position in order to allow the power supply circuit 150 to switch off. In other examples, the initiator switch RL1 may only initially shut temporarily, e.g. for long enough to enable the power supply circuit 150 to turn on, and it may then be permanently off (or only used to manually restart the power supply circuit 150). For example, RL1 may comprise a bistable relay.

[0122] Consider when the RU is in the second mode of operation, when the gate voltage of M1 is 0V, there will be no voltage across R8 or M1 , and no voltage will be provided to at the gate of M1 as, when no signal is induced in the NFC device, V4 is also 0V so Q4 will not be saturated, Q1 is also not saturated as there is no voltage across R2 and R3, and RL1 will be open. In this mode of operation, if a first signal is induced in the NFC device, then V4 will be high. At this point, the second voltage V2 will also be pushed high by V4, and M1 will then couple the output 155 to the first voltage V1. For example, if V4 is high, then Q4 will saturate meaning that voltage is also dropped across R1 and D1 , with D1 ensuring that V4 reaches a threshold voltage before allowing the current to pass.

[0123] In other words, responsive to the first signal being induced in the NFC device 160, the power supply circuit 150 is configured to apply the second voltage V2 to the first switch control element 702. By having the first switch control element 702 being configured to selectively couple the output 155 to the first voltage V1 based on the voltage V4 provided by the NFC device 160, the power supply circuit 150 is enabled to switch on the RU utilising the power provided by the NFC device 160, which, as described with reference to Figure 6b, originates in the optical signal transmitted by the BB unit. The power supply circuit 150 can therefore transition the RU to the first mode of operation without utilising any power supply within the RU, e.g. without relying on V1 .

[0124] It will be appreciated that when the RU is in the first mode of operation, the gate voltage of M1 is high. For example, the gate voltage of M1 may be high by means of closing RL1. In other examples, the gate voltage of M1 is high without closing RL1 , wherein the gate volage of M1 is high by means of saturating Q1 after M1 has been closed (as, once Q1 is saturated, through the diode D2 the voltage V1 is applied to the resistor divider R6 and R7 which saturates Q3 and consequently Q2 is also saturated, as there is also a voltage across the couple R4 and R5).

[0125] In this example, the power supply circuit 150 further comprises a second switch control element 703 configured to, when a third voltage V3 is applied to the second switch control element 703, prevent the second voltage V2 from being applied to the first switch control element 702. The second switch control element 703 in this example comprises a second signal MOSFET M2. Applying the third voltage V3 may therefore act to transition the RU into the second mode of operation (e.g. into the Power-Off mode).

[0126] If the network node comprising the power supply circuit 150 receives an indication to transition the network node into second mode of operation, the power supply circuit 150 may be configured to pulse the third voltage V3. When V3 is high, the second MOSFET M2 is put into a conducting state, which means that the gate voltage of the M1 is drawn down to 0V. At this point, M1 is no longer conducting, which means that no power is drawn across the output 155. There will also be no voltage drawn across R3 and R2 which means that Q1 will not be saturated. Therefore, even when V3 is no longer high, the gate of M1 will remain at 0V until V4 is pushed high again. It is therefore preferable to pulse V3 in order to transition the network node into the second mode of operation, without then leaving V3 high (e.g. drawing power) when in the second mode of operation.

[0127] If the network node comprising the power supply circuit 150 receives an indication to transition the network node into second mode of operation, the power supply circuit is configured to generate a second signal through the NFC device 160 (this may be performed by means of circuitry not illustrated in Figure 7).

[0128] It will be appreciated that the energy required to transition the RU into the first mode of operation, and at the same time the command to initiate the transition, comes from the BB in terms of optical power. If the BB that wants to reactivate a RU, the BB unit may initiate transmission of optical power towards the RU on the connected fiber, thereby transitioning the relevant RU into the first mode of operation.

[0129] Just as an example, supposing that such the NFC device 190 emits 1 dBm of power and assuming a path of 5 dB of attenuation (due to fiber / connectors, or also filters or couplers according to the architecture), when the switch 603 is in position B the whole received energy (-4 dBm) is sent to the photodetector 602 which converts the optical energy into electrical energy. If we account for a realistic conversion efficiency of 33%, the resulting power, converted in mW, is about 0.13 mW.

[0130] Assuming, for example, 3 minutes of recharging time, on the capacitor it is possible to store about 24 mJ of energy. This amount of energy may then be utilised to commutate the switch 603 from B to A (about 4 mJ are enough, i.e. ~10ms x 400mW required by the switch 603 to commutate, and to the logic of the switching circuit to store the status) and for the first signal transmission using the NFC device 190 towards the coupled RU NFC device 160.

[0131] Commercially available NFC reader providers claim a power consumption of about 0.5W (at around 3V). In our specific case we only need to switch on the NFC device 190 for long enough that a current is induced in the corresponding NFC device 160 (interpreted by RU as the ‘wake up’ signal). A current of tens of A is enough in the NFC device 160 to feed the base of Q4 transistor and thereby couple the output 155 to the first voltage V1 . In this example the energy required to come out of the second mode of operation is very low, for example, 1.5 may be enough on V4 to generate a current of 100 pA (equivalent to 0.15 mW) for 100 ms, that is 0.015 mJ.

[0132] All in all, in the power control circuit after for example 3 mins of charging, there may be an available energy of 20 mJ which is enough to keep on the power control circuit for about 40 ms, and is sufficient to reach the wanted signal / power transfer to RU to the first mode of operation utilising the NFC devices 190 and 160.

[0133] Figure 8 illustrates an example implementation of a state diagram illustrating of the behaviour of a Power Supply Circuit (power supply circuit 150) in a Radio Unit (RU) 110. As illustrated in Figure 8, the RU 110 may operate in at least 4 modes of operation: Normal Mode 10, Pre-Power-Off Mode 820, Power-Off Mode 830 and Pre-Normal Mode 840. The RU 110 may comprise an NFC device 160, wherein the NFC device 160 is configured to receive and transmit signals. The RU may comprise the power supply circuit 150 illustrated in Figure 7. An optical connector coupling the RU to the BB unit may comprise the power control circuit 180 illustrated in Figure 6b.

[0134] When the RU 110 is operating the Normal Mode 810 (e.g. the first mode of operation), the switch 603 is in position A and M1 is conducting. In step 810a, if no Power-Off command is received by the RU 110 from the BB unit 120 then RU 110 remains in the Normal Mode 810.

[0135] When the BB unit 120 requires the RU 110 to completely power off, the RU 110 receives an indication from the from the BB unit 120 to transition into the Power-Off mode (e.g. the second mode of operation), for example, as described with reference to step 330 or step 520. At this point, the RU may transition 850 into a Pre-Power-Off mode 820.

[0136] The Pre-Power-Off Mode 820 may be considered a transition state of the RU 110 to allow the RU 110 to transition from operating in the Normal Mode 810 to operating in the Power-Off Mode 830. During this Pre-Power-Off mode, the second signal may be induced in the NFC device 160 which may then commute the switch 630 into position B, thus transitioning 860 the RU into the Power-Off Mode 830. As long as no signal is received at the NFC device 160 then the RU remains in the Power-Off Mode 830. When the BB unit 120 requires the RU 110 to power on, the BB unit may transmit the first optical signal to the RU (e.g. as described with reference to step 420).

[0137] If, the first signal is received at the RU (e.g. as described with reference to step 210) e.g. if the power control circuit receives enough power in the first optical signal from the BB unit, then the RU may transition 870 into the Pre-Normal Model 840. During the transition 870, the energy converted from the optical energy may also be used to commute the switch 630 to position A.

[0138] In this example, in the Pre-Normal mode 840, the RU and BB unit may attempt handshake signalling. If the handshake signalling is successful, the RU may transition 680 into the Normal mode 810. However, if the handshaking is not successful, the RU may transition back to the Pre-Power Off mode 820.

[0139] Figure 9 illustrates an network node 900 comprising processing circuitry (or logic) 901. The processing circuitry 901 controls the operation of the network node 900 and can implement the method described herein in relation to an network node 900. The processing circuitry 901 can comprise one or more processors, processing units, multicore processors or modules that are configured or programmed to control the network node 900 in the manner described herein. In particular implementations, the processing circuitry 901 can comprise a plurality of software and / or hardware modules that are each configured to perform, or are for performing, individual or multiple steps of the method described herein in relation to the network node 900. It will be appreciated that the network node 900 may comprise one or more virtual machines running different software and / or processes. The network node 900 may therefore comprise, or be implemented in or as one or more servers, switches and / or storage devices and / or may comprise cloud computing infrastructure that runs the software and / or processes.

[0140] Optionally, the network node 900 may comprise a memory 903. In some embodiments, the memory 903 of the network node 900 can be configured to store instructions (e.g. program code) executable by the processing circuitry 901 of the network node 900 whereby the apparatus is operable to perform the method as described with reference to any one or more of Figures 4 to 7. Alternatively or in addition, the memory 903 of the network node 900, can be configured to store any requests, resources, information, data, signals, or similar that are described herein. The processing circuitry 901 of the network node 900 may be configured to control the memory 903 of the network node 900 to store any requests, resources, information, data, signals, or similar that are described herein.

[0141] In some embodiments, the network node 900 may optionally comprise a communications interface 902. The communications interface 902 of the network node 900 can be for use in communicating with other nodes, such as other virtual nodes. For example, the communications interface 902 of the network node 900 can be configured to transmit to and / or receive from other nodes requests, resources, information, data, signals, or similar. The processing circuitry 901 of network node 900 may be configured to control the communications interface 902 of the network node 900 to transmit to and / or receive from other nodes requests, resources, information, data, signals, or similar. The communications interface 902 can use any suitable communication technology.

[0142] The network node 900 may be configured operate in the manner described herein in respect of a first network node or a second network node.

[0143] Figure 10 is a block diagram illustrating a first network node 1000 according to some embodiments. The first network node 1000 can operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The first network node 1000 comprises a receiving module 1002 configured to, when the first network node is operating in the second mode of operation, receive a first signal comprising a first amount of energy . The first network node 1000 comprises a entering module 1004 configured to enter the first mode of operation using the first amount of energy to perform the transition from the second mode of operation to the first mode of operation. The first network node 1000 may operate in the manner described herein in respect of an first network node.

[0144] Figure 11 is a block diagram illustrating a second network node 1100 according to some embodiments. The second network node 1100 is configured to communicate with a first network node that can operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power. The second network node 1100 comprises a transmitting module 1102 configured to, when the first network node is operating in the second mode of operation, and responsive to obtaining an indication that the first network node is required to operate in the first mode of operation, transmit, to the first network node, a first optical signal comprising a first amount of optical energy.

[0145] There is also provided a computer program comprising instructions which, when executed on a least one processor (such as the processing circuitry 901 of the network node 900 described earlier), cause the processor to carry out at least part of the method(s) described herein. According to some embodiments there is provided a carrier containing the computer program. In some embodiments, the carrier can be any one of an electronic signal, an optical signal, an electromagnetic signal, an electrical signal, a radio signal, a microwave signal, or a computer-readable medium. There is also provided a (for example, tangible and / or non-transient) computer-readable medium comprising instructions which, when executed by at least one processor, cause the at least one processor to perform at least part of the method(s) described herein.

[0146] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

CLAIMS1 . A first network node comprising a power supply circuit for supplying power to the first network node, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilizing zero power, the first network node comprising an optical connector socket configured to receive an optical connector, and the power supply circuit comprising: an output (155) configured to provide power to the first network node in the first mode of operation; and a Near Field Communication, NFC, device (160), wherein the NFC device (160) is configured to, responsive to a first signal being induced in the NFC device (160) from the optical connector, initiate the power supply circuit to provide power to the first network node.

2. The first network node as claimed in claim 1 wherein the NFC device is positioned within the first network node adjacent to an optical connector socket.

3. The first network node as claimed in claim 2 wherein the optical connector socket is configured to receive an optical connector as claimed in any one of claims 11 to 17.

4. The first network node as claimed in any one of claims 2 to 3 wherein the NFC is positioned within the first network node such that the first signal can be induced by a second NFC device in the optical connector.

5. The first network node as claimed in any one of the preceding claims, wherein the first network node requires a threshold amount of energy to perform the transition from the second mode of operation to the first mode of operation, and the first signal induced in the NFC device comprises a first amount of energy greater than or equal to the threshold amount of energy.

6. The first network node as claimed in any one of claims 1 to 5 wherein the power supply circuit comprises:a first switch control element (702) configured to selectively couple a first voltage, V1 , to the output (155), wherein the first switch control element (702) is configured to couple the first voltage V1 to the output (155) in the first mode of operation when a second voltage, V2, is applied to the first switch control element (702).

7. The first network node as claimed in claim 6, the power supply circuit further comprising:- a second switch control element (703) configured to, when a third voltage V3 is applied to the second switch control element (703) prevent the second voltage V2 from being applied to the first switch control element (702) to decouple the first voltage from the output in the second mode of operation.

8. The first network node as claimed in claim 7, wherein, responsive to an indication to the first network node into the second mode of operation, the power supply circuit is configured to pulse the third voltage V3; and the power supply circuit is configured to generate a second signal through the NFC device (160).

9. The first network node as claimed in any one of claims 5 to 8, wherein the power supply circuit is configured to: responsive to detecting the first signal when the first voltage is coupled to the output, generate a third signal in the NFC.

10. The first network node as claimed in claim 5 to 9, wherein the first network node is configured to: receive an optical input signal; and responsive to the optical input signal comprising an indication to transition into the second mode of operation, pulse the third voltage, and control the power supply circuit to generate the second signal through the NFC device.11 . The first network node as claimed in any one of claims 1 to 10, wherein the first network node comprises a radio unit.

12. An optical connector for initiating a power supply circuit in a first network node to provide power to the first network node, the optical connector configured for input into an optical connector socket of the first network node, the optical connector comprising a power control circuit comprising: an input (601) configured to receive a first optical signal (106); an energy conversion apparatus (602) selectively coupled to the input (601), wherein the energy conversion apparatus (602) is configured to convert the first optical signal (106) into electrical energy; and a Near Field Communication, NFC, device (190), wherein the power control circuit is configured to utilise the electrical energy to generate a first signal across the NFC device (190).

13. The optical connector of claim 12 wherein the power control circuit further comprises an output (605) selectively coupled to the input (601).

14. The optical connector of claim 12 or 13, wherein the power control circuit further comprises a switch control element (606), wherein the switch control element (606) is configured to selectively couple the energy conversion apparatus (602) to either the input (601) or to the output (605).

15. The optical connector of any one of claims 12 to 14, further comprising: an energy storage apparatus configured to store the energy and, responsive to the stored energy meeting a threshold condition, provide the energy to the NFC device (190) to generate the first signal.

16. The optical connector as claimed in claim 15, wherein the switch control element (606) is configured to, responsive to the stored energy meeting the threshold condition: couple the input (601) to the output (605); and decouple the energy conversion apparatus (602) from the input (601).

17. The optical connector as claimed in claims 15 or 16, wherein the switch control element (606) is configured to, responsive to a second signal being induced in the NFC device (190) indicating that the radio unit is to be turned off: couple the energy conversion apparatus (602) to the input (601); and decouple the input (601) from the output (605).

18. The optical connector as claimed in claim 14, responsive to a third signal being induced in the NFC device (190) indicating that the radio unit is turned on, the switch control element (606) is configured to: couple the input (601) to the output (605); and decouple the energy conversion apparatus (602) from the input (601).

19. The optical connector as claimed in any one of claims 12 to 18 wherein the optical connector is configured to be received by an optical connector socket of a first network node as claimed in any one of claims 1 to 11 .

20. A method performed by a first network node in an optical network, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power, the method comprising: when the first network node is operating in the second mode of operation, receiving (210) a first signal at a NFC device (160); and entering (220) the first mode of operation using the energy from the NFC device to perform the transition from the second mode of operation to the first mode of operation.21 . The method as claimed in claim 20, further comprising: when the first network node is operating in the first mode of operation, receiving (310) an indication that the first network node is to enter the second mode of operation; and responsive to receiving the indication, entering (320) the second mode of operation.

22. The method as claimed in claim 20 or 21 , further comprising receiving the first signal at a Near Field Communication device via an optical connector.

23. The method as claimed in claim 22, when dependent on claim 21 , further comprising receiving the indication from a second network node via the optical connector.

24. A method performed by a second network node in an optical network, wherein the second network node is in communication with a first network nodeconfigured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power, wherein the first network node uses a first amount of energy to perform the transition from the second mode of operation to the first mode of operation; the method comprising: when the first network node is operating in the second mode of operation, transmitting (420), to the first network node, a first optical signal comprising at least the first amount of energy.

25. The method as claimed in claim 24, further comprising: when the first network node is operating in the first mode of operation, responsive to obtaining an indication that the network node is required to operate in the second mode of operation, transmitting (520), to the first network node, an indication to enter the second mode of operation.

26. The method as claimed in claim 24 or 25, further comprising: transmitting the first signal until receiving an indication from the first network node that the first network node has transitioned into the first mode of operation.

27. The method as claimed in claim 24 or 25, further comprising: transmitting the first signal until the energy transmitted is greater than or equal to a predetermined threshold energy.

28. The method as claimed in any one of claims 24 to 27, further comprising: receiving the indication that the first network node is required to operate in the first mode of operation from a controller network node.

29. The method as claimed in any one of claims 24 to 28, further comprising: determining that the first network node is required to operate in the first mode of operation.

30. A first network node in an optical network, wherein the first network node is configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power, the first network node comprising processing circuitry and memory, the memory containinginstructions executable by the processing circuitry whereby the first network node is operable to: when the first network node is operating in the second mode of operation, receive a first signal induced in an NFC device (160) to enter the first mode of operation to perform the transition from the second mode of operation to the first mode of operation.31 . The first network node as claimed in claim 30 wherein the memory contains further instructions executable by the processing circuitry whereby the first network node is operable to perform the method as claimed in any one of claims 19 to 22.

32. A second network node in an optical network, wherein the second network node is in communication with a first network node configured to operate in at least a first mode of operation utilising non-zero power and a second mode of operation utilising zero power, wherein the first network node uses a first amount of energy to perform the transition from the second mode of operation to the first mode of operation; the second network node comprising processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the second network node is operable to: when the first network node is operating in the second mode of operation, transmit (420), to the first network node, a first optical signal comprising at least the first amount of optical energy.

33. The second network node as claimed in claim 32, wherein the memory contains further instructions executable by the processing circuitry whereby the second network node is operable to perform the method as claimed in any one of claims 24 to 29.

34. A computer program, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out a method according to any of claims 20 to 29.

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