System and method for power supply monitoring using high-power light

Abstract

The present invention relates to a system and method for monitoring multicore fibres (MCF). The system comprises a unit that generates the optical signal; a unit that processes and monitors this original signal; and the crosstalk and backscattering signals that are generated when the generated optical signal is transmitted through a fibre connecting two FIFOs. The method analyses these signals produced at different powers and determines a threshold defining a malfunction that switches off the laser in addition to transmitting radio signals over fibre without affecting data traffic quality, as assessed by the Error Vector Magnitude (EVM).

Description

[0001] SYSTEM AND METHOD FOR MONITORING POWER SUPPLY USING HIGH-POWER LIGHT

[0002] DESCRIPTION

[0003] OBJECT OF THE INVENTION

[0004] The present invention relates to the field of electrical power supply by means of optical fibers, more specifically, by means of multicore fibers (MCF).

[0005] The main object of the present invention is a system and a method for monitoring the power supply of a remote node using high power laser (HPL) through multicore fibers (MCF).

[0006] BACKGROUND OF THE INVENTION

[0007] Current and future mobile networks must meet a series of demanding requirements regarding data transmission rate, latency, and energy efficiency. To meet these requirements, the use of optical fibers has been proposed as the fundamental transmission medium for these networks. More specifically, the use of multicore fibers (MCF) in fronthauls is presented as a possible solution to increase data transmission rate and decrease latency in mobile networks. The fronthaul is the portion of the mobile network that connects the radio units and / or antennas, RRH / RAU (Remote Radio Head / Radio Access Unit), to the baseband unit(s) (BBU).In centralized 5G mobile networks, current infrastructure deployment proposals focus on centralization to achieve cost savings, greater energy efficiency, and a smaller carbon footprint. The BBU (Basic Business Unit) is located in a central office that may be several kilometers away from the RRH / RAU (Remote Access Unit). It is in the latter that the antenna or array of antennas providing wireless connectivity to the end user / terminal is located.

[0008] To leverage existing optical infrastructure, as well as future infrastructure, the proposal also includes using fiber optics for remote power transmission to centrally supply full or partial power to these RRH / RAU systems. Technologies such as Power over Fiber (PoF) propose transmitting energy via high-power optical signals, which can be converted into electrical energy using Photovoltaic Power Converters (PPCs).

[0009] The need for remote and secure power supply to communication networks is well known, and there are patents describing this need, with proposals on how to supply power safely with fault protection systems, but in the context of power supply in the electrical domain.

[0010] Power over Ethernet (PoF) also requires these protection systems, which help prevent potential risks due to the high optical power transmitted. If the optical fibers through which the PoF signal is transmitted are damaged, some of the high-intensity optical radiation will not be contained and could cause material or even personal damage. For this reason, it is necessary to include monitoring systems that can detect transmission errors such as fiber breaks or any abnormal phenomenon that could damage the fiber. It is also important that the technique does not impose additional power consumption on the remote node, since the initial goal is to minimize its power requirements.

[0011] However, the state of the art in monitoring techniques for these types of systems is quite limited. The few commercial systems that implement monitoring in their products rely on auxiliary communication channels to link the PoF signal transmitter with the receiver. This is the case with systems using a high-power laser and a receiver connected by a multimode fiber (MMF). These systems have an additional communication channel through which the receiver constantly reports its status. This technique, while effective, is not energy efficient, as it requires a laser, a photodetector, and the associated electronics in the receiver, meaning that both these components and the communication itself must be powered, making it incompatible with current and future mobile networks.

[0012] Techniques have also been proposed that utilize phenomena occurring in the optical domain during signal transmission, such as MCF fiber crosstalk, to calculate the transmitted optical power. However, in this case, a Wavelength Division Multiplexer (WDM) is required at the receiving end to filter the crosstalk signal from the other transmitted signals. In other cases, backscattering generated in one of the cores of an MCF fiber is used to infer the transmitted power. This technique requires a circulator at the transmitting end to collect and direct the reflected optical power to a photodetector for measurement. This circulator will reduce the efficiency of optical power transmission due to insertion losses.

[0013] Another similar proposal uses a specific OTDR (Optical Time Domain Reflectometer) to estimate crosstalk and backscattering in MCF fibers by emitting a light pulse (not operating in continuous wave mode). The light emitted at the fiber end is of no use. Fiber designs with vapor cores and a single cladding have even been proposed to detect transmission malfunctions using the returned signal, but these require the addition of passive optical elements such as couplers at the fiber end, which have high insertion losses.

[0014] The use of wavelength-selective semi-reflective mirrors etched into one or more of the MCF fiber cores where power distribution will occur has also been proposed. In this case, an additional passive optical element is required in the optical link, which also partially reduces the delivered optical power.

[0015] In light of the current state of the art, a solution and / or technique is needed to monitor and prevent failures in spatially multiplexed fiber optic networks due to the injection of high-power optical signals for remote power-by-light (PoF) operation. This solution must efficiently overcome the drawbacks of existing prior art systems without affecting existing data traffic on the network and with minimal power penalty compared to the PoF signal sent for remote power-by-light operation. The present invention is proposed to achieve this objective.

[0016] SUMMARY OF THE INVENTION

[0017] The present invention relates to a high-power light monitoring system for a remote node using multicore fibers (MCF) comprising: at least one high-power light emitter (HPL) configured to power the remote node with a high-power light beam; a first Fan-In-Fan-Out (FIFO) device connected to the high-power light emitter (HPL); a second Fan-In-Fan-Out (FIFO) device connected to the remote node; at least one MCF fiber connected to the first FIFO device and the second FIFO device, preferably by means of an FC / LIPC connector adapter, and comprising at least two cores, a first core configured to transmit high-power light from the first FIFO device to the second FIFO device, and a second core configured to receive and transmit backscatter reflected light to the first FIFO device;a feedback photodetector connected to the first FIFO device and configured to receive backscattered reflected light from the first FIFO device and capable of generating a feedback signal; a control and processing module connected to the feedback photodetector and the HPL light emitter and configured to monitor the feedback signal.

[0018] Preferably, the processing module connected to the feedback photodetector and the HPL light emitter is also configured to control the HPL light emitter based on the feedback signal obtained from the feedback photodetector.

[0019] Thus, the monitoring system of the invention is based on the detection of residual optical signals of crosstalk and backscattering generated when transmitting an optical signal through a core of the MCF.

[0020] In order to electrically power the remote node, the system of the invention may further comprise: a Photovoltaic Power Converter (PPC), connected to the second FIFO device, a DC-DC converter, connected to the PPC and the remote node, and configured to adapt the voltage levels of the PPC.

[0021] In preferred embodiments, the monitoring system of the invention may further comprise: an optical splitter, connected to the high-power light emitter and the MCF fiber, and configured to split the high-power light beam into a feed beam and a reference beam; an additional photodetector connected to the optical splitter and configured to detect the reference beam; and a Lock-in amplifier connected to the additional photodetector and the feedback photodetector and configured to amplify the signal received from each photodetector.

[0022] For its part, the MCF fiber may preferably comprise at least 2 cores, a first core configured to transmit high-power light and sometimes a communications signal; a second core configured to transmit light reflected by backscattering.

[0023] The monitoring system of the invention can also transmit communications data, for which purpose it may comprise: a light emitter configured to generate an optical carrier for the communications signal; a vector signal generator configured to generate signals representative of the communications signal; and a Mach-Zehnder modulator (MZM) connected to the light emitter and the vector signal generator, and to the first FIFO device, and configured to modulate the optical carrier generated by the light emitter according to the modulation signals and formats representative of the communications signal and transmit it to the first FIFO device.

[0024] In a preferred embodiment, the light emitter configured to generate an optical carrier for the communications signal is a laser, and in this case, the system may further comprise an isolator element or circulating device connected to the light emitter to provide protection and isolation of the emitted light.

[0025] The invention also relates to a method for monitoring the power supply of a remote node with high-power light using multi-core fibers (MCF) that makes use of the described system, and comprising the steps of: a) generating a high-power light beam using the high-power light emitter (HPL); b) sending the high-power light beam to the remote node to power it through the MCF fiber using FIFO devices; c) obtaining backscatter reflected light; d) sending the backscatter reflected light to the feedback photodetector through the MCF fiber using FIFO devices; and e) detecting and monitoring the backscatter reflected light using the feedback photodetector, which generates a first voltage representative of the detected reflected light, and the control and processing module.

[0026] More specifically, the stage of detecting and monitoring backscatter reflected light may further comprise the sub-stages of: a) setting a threshold for the first feedback photodetector voltage above which, if the backscatter reflected light is greater, a fault is considered to have occurred; and b) switching off the HPL light emitter when the determined threshold is exceeded.

[0027] In preferred embodiments, the method may further comprise the steps of: splitting the HPL light beam into a feed beam and a reference beam using the optical splitter; detecting the reference beam using the additional photodetector, which generates a second voltage representative of the reference beam; amplifying the first voltage and the second voltage using the Lock-ln amplifier; and calculating the power supplied to the remote node.

[0028] Preferably, the monitoring method of the invention further comprises a step of transforming optical energy from the high-power light beam into electrical energy using the PPG.

[0029] In the monitoring method of the invention, preferably, the high-power light is emitted by performing a power sweep from +23 dBm to +33 dBm.

[0030] More preferably, an analysis stage can be carried out of the first voltage, representative of the light reflected by backscattering, compared to the power sweep emitted when the first FIFO device is connected; the second FIFO device and the two FIFO devices simultaneously.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To complement the description being made and in order to help a better understanding of the characteristics of the invention, according to a preferred embodiment thereof, a set of drawings is included as an integral part of said description, in which, for illustrative and non-limiting purposes, the following has been represented:

[0033] Figure 1.- Shows a diagram of the system and method with the main elements and processes that comprise it.

[0034] Figure 2.- Shows a schematic of a preferred embodiment of the system, which includes a Lock-ln amplifier to improve sensitivity and resolution.

[0035] Figures 3a) and 3b). - Show a sinusoidal tone of the HPL a) in the time domain and b) in the frequency domain.

[0036] Figure 4.- Shows a detailed diagram describing one of the preferred embodiments of the invention.

[0037] Figures 5a) and 5b). - Show the graphs of the voltage received by the photodetector over time for variations of the HPL laser from +23 dBm to +33 dBm a) in increments of 0.1 dB, b) in increments of 0.5 dB.

[0038] Figures 6a), 6b), and 6c) show graphs of the voltage received by the photodetector for HPL powers of +23, +26, +29, and +32 dBm in different configurations: a) FIFO 1 connector disconnected from the MCF. b) FIFO 2 connector disconnected from the MCF. c) All connectors in place to connect FIFO 1 + MCF + FIFO 2.

[0039] Figure 7.- Shows a graph of received voltage with the same laser power (+23 dBm) when a cut occurs in the system at two different points.

[0040] Figure 8.- Shows a graph of the Error Vector Magnitude (EVM) as a measure of the correct transmission of data, measured for each HPL laser power.

[0041] PREFERRED EMBODIMENTS OF THE INVENTION

[0042] The invention comprises a system and method for monitoring the power supply of a remote node (3) with high-power light (HLP) using multi-core fibers (MCF) (1) based on the detection of residual optical signals generated by the transmission itself through the MCF fiber (1).

[0043] This system and method are based on the fact that when an optical signal is transmitted through one of the cores (101) of the MCF fiber (1), part of its power couples to the other cores (102, 103), generating a crosstalk signal that travels in the same direction as the original signal. This crosstalk signal is subject to Rayleigh scattering, which generates a backscatter signal proportional to the crosstalk signal, but propagating in the fiber core in the opposite direction. This backscatter signal is used in the technique to infer the optical power being transmitted through the MCF fiber (1), thus enabling network monitoring.

[0044] Figure 1 graphically illustrates the monitoring technique and a possible implementation thereof. The system comprises a high-power light source (HPL) (2) for powering a remote node (3). The system also includes a photodetector (5) and a control and processing module (4), in this case consisting of a data acquisition module (6) and a computer (7), all integrated into a central unit. The control and processing module (4) can also control the high-power light source (HPL) (2).

[0045] The system comprises for transmission, a multicore fiber (MFC) (1) and two Fan In-Fan Out (FIFO) devices (8, 9) connected by said MCF fiber (1).

[0046] The emitted high-power light, also called the monitored signal, is injected through a first core (101) of the MCF fiber (1), by means of a first Fan In-Fan Out (FIFO) device (8), and is extracted from said MCF fiber (1) by means of a second Fan In-Fan Out (FIFO) device (9).

[0047] The monitored signal is used to power the remote node (3). For this purpose, the system also includes a photovoltaic power converter (PPC) (13) to transform the optical energy into electrical energy and a DC-DC converter (14) to adapt the voltage levels of the PPC (13) to the requirements of the receiving node. The monitoring signal resulting from backscattering, also called backscatter reflected light, is extracted from the MCF fiber (1) through a port separate from the first FIFO device (8), where it is measured and digitized by the control and processing module (4). In the specific case of the prototype shown in Fig. 1, the HPL used exhibits a sinusoidal frequency close to 130 kHz for optical powers around +30 dBm, as shown in Fig. 3.This tone can be used as a reference for the Lock-ln (12) by extracting a small portion of the signal (or beam) using an optical splitter (10) before it is sent through the MCF fiber (1). Additionally, an extra photodetector (11) must be included to detect the reference signal (or beam).

[0048] In a preferred embodiment, which allows the system to be used in long-distance links or with lower power levels, the system further comprises a Lock-ln amplifier (12) connected to the photodetectors (5, 11) to amplify the received signal, as shown in Fig. 2.

[0049] In a preferred embodiment, described in Fig. 4, the system comprises two FIFO devices (8, 9) for interconnecting multiple inputs and multiple outputs at both ends of the MCF fiber (1). In this case, the MCF fiber (1) has four 100 m long cores, and each core performs the following function: the monitored signal is transmitted through the first core (101), where a PPC (13) can be located at the receiver for powering the remote node (similar to Fig. 2); backscatter detection is performed with the second core (102); data transmission is carried out using the third core (103), although this data transmission could also be performed on any of the other cores (102) and (101).This third core (103) allows us to demonstrate that the proposed monitoring technique does not significantly affect data transmission while maintaining the same quality of service and high transmission rates, which is evaluated by measuring the EVM (Error Vector Magnitude).

[0050] The proposed configuration includes the first input FIFO device (8) comprising a 1 m pigtail of 4-core MCF fiber (1), terminated with an FC / UPC connector. This pigtail is connected to a 100 m section of 4-core MCF fiber (1) with connectors at both ends and is linked to the second output FIFO device (9) via an FC / UPC connector adapter.

[0051] The high-power light emitter (HPL) (2) operates at 1480 nm, generating a monitored PoF power signal of up to 2 W (+33 dBm). This implementation also includes a light emitter (15) configured to generate an optical carrier for the 5G NR analog fiber over radio signal (ARoF), which is a laser diode (LD) at 1552.8 nm. An isolator or circulator device (16) is also included for the protection and isolation of this laser (15). The optical carrier is modulated using a Mach-Zehnder modulator (MZM) (17). To generate the 5G NR baseband signal and the electrical carrier, an SMW200A vector signal generator (VSG) (18) is used as the input signal to the Mach-Zehnder modulator (MZM) (17).

[0052] In a preferred embodiment, the monitoring method of the invention performs a power sweep of the HPL light emitter (2), in this case a laser, in the range of +23 dBm to +33 dBm.

[0053] In this way, it is possible to determine the received response using the backscatter signal, and to determine the power supplied to the remote node (3). Knowing the value of the supplied power a priori, the resolution of the system can be estimated by determining this supplied power.

[0054] Figure 5 shows graphs of the voltage received by the photodetector over time in two sweeps with different steps of the HPL laser (1).

[0055] In Fig. 5a, with a resolution of 0.1 dB, peaks and some irregularities affecting the sensing system are observed. On the other hand, in Fig. 5b, with a separation between the HPL powers of 0.5 dB, it is shown that in this case the supplied power can be accurately discerned. The measurement time for each laser power was set to 1 minute in both cases.

[0056] Different system configurations are then analyzed in which the connections of the FIFO devices are varied (8, 9).

[0057] Figure 6a) shows the voltage received by the photodetector (5) for different HPL powers when the first FIFO device (8) is disconnected from the MCF fiber (1). Figure 6b) shows the voltage received by the photodetector (5) for different HPL powers when the second FIFO device (9) is disconnected from the MCF fiber (1). Figure 6c) shows the voltage received by the photodetector (5) for different HPL powers when both FIFO devices (8, 9) are correctly connected to the MCF fiber (1).

[0058] Thus, by analyzing the average value of each graph, it can be observed that, at the maximum power of the HPL laser (1), the voltage levels received by the photodetector (5) when the FIFO devices (8, 9) are correctly connected (Fig. 6c) are significantly lower compared to the voltage levels received when transmitting the minimum laser power in any of the other cases (Fig. 6a) and 6b). This allows us to establish a threshold above which, if the detected voltage is higher, there would be a fault; otherwise, the power supplied to the remote node (3) can be determined.

[0059] The method of the invention also allows for the analysis of performance in the event of interruptions, as shown in Fig. 7, where two interruption scenarios are analyzed following an interval without interruptions. The interruption sequence includes: a first interruption between the MCF fiber (1) and the second FIFO device (9), simulating an interruption at the end of the MCF fiber (1) and very close to the remote node (3); and a second interruption between the first FIFO device (8) and the MCF fiber (1), simulating an interruption at the beginning of the MCF fiber (1) and very close to the HPL light emitter (1). These interruptions each last 60 seconds.

[0060] When analyzing the first cut, it is observed that the average detected voltage level fluctuates around 6.2 V.

[0061] According to Figure 5b, the threshold has been set at 1.75 V. Thus, as long as the system does not detect a voltage level above this threshold, it is possible to calculate the power supplied to the remote node (3) based on the detected voltage level. As explained earlier, the voltage threshold is determined through a prior characterization of the system.

[0062] On the other hand, if the voltage threshold is exceeded, it is considered that there is a problem and the laser is turned off (1) for protection, as would happen in the case of the first and second cuts.

[0063] In a preferred embodiment, the method of the invention allows data transmission while maintaining adequate signal quality, which is standardized as a requirement of an EVM value of 4.5% for a 5G NR signal with a bandwidth of 100 MHz, a subcarrier spacing of 30 kHz, and a 256 QAM modulation format. According to Fig. 8, it can be observed that this requirement is met at all the power levels described above.

[0064] Thus, the system and method of the invention allow the monitoring of the power supply of a remote node (3) with high-power light without the need to implement additional elements such as semi-reflective and selective mirrors; the use of filters in the node; or the use of additional cores for the associated return signal.

Claims

AMENDED CLAIMS received by the International Bureau on 25 March 2026 (25.03.2026) 1. A remote node (3) power monitoring system using high-power light via multi-core fibers (MCF) (1) comprising: at least one high-power light emitter (HPL) (2) configured to power the remote node (3) via a high-power light beam; a first Fan-In-Fan-Out (FIFO) device (8) connected to the high-power light emitter (HPL) (2); a second Fan-In-Fan-Out (FIFO) device (9) connected to the remote node (3); at least one MCF fiber (1) connected to the first FIFO device (8) and the second FIFO device (9), comprising at least two cores (101, 102), a first core (101) configured to transmit high-power light from the first FIFO device (8) to the second FIFO device (9), a second core (102); a feedback photodetector (5) connected to the first FIFO device (8);and a control and processing module (4) connected to the feedback photodetector (5) and the HPL light emitter (2) and configured to monitor a feedback signal; and characterized in that the second core (102) is configured to receive and transmit backscattered reflected light to the first FIFO device (8) and the feedback photodetector (5) is configured to receive backscattered reflected light from the first FIFO device (8) and generate the feedback signal.

2. The monitoring system according to claim 1, wherein the processing module (4) connected to the feedback photodetector (5) and the HPL light emitter (2) is further configured to control the HPL light emitter (2) based on the feedback signal obtained from the feedback photodetector (5).

3. The monitoring system according to claims 1 and 2, wherein the system further comprises a photovoltaic power converter (PPC) (13), connected to the second PIFO device (9), a DC-DC converter (14), connected to the photovoltaic power converter (PPC) (13) and to the node remote (3), and configured to adapt the voltage levels of the photovoltaic power converter (PPC) (13).

4. The monitoring system according to the preceding claims, further comprising: an optical splitter (10), connected to the HPL light emitter (2) and the MCF fiber (1), and configured to split the high-power light beam into a feed beam and a reference beam; an additional photodetector (11) connected to the optical splitter (10) and configured to detect the reference beam; and a Lock-in amplifier (12) connected to the additional photodetector (11) and the feedback photodetector (5) and configured to amplify the signal received from each photodetector (5, 11).

5. The monitoring system according to the preceding claims, wherein the MFC fiber (1) is connected to the second FIFO device (9) by means of an adapter between FC / UPC connectors.

6. The monitoring system according to claims 1 and 2, wherein the MCF fiber (1) comprises at least 3 cores, a first core (101) configured to transmit high-power light; a second core (102) configured to transmit backscatter reflected light; and a third core (103) configured to transmit a communications signal.

7. The monitoring system according to claim 6, wherein the first core (101) and the second core (102) are further configured to transmit a communications signal.

8. The monitoring system according to claims 6 and 7, further comprising: a light emitter (15) configured to generate an optical carrier for the communication signal; a vector signal generator (18) configured to generate signals representative of the communication signal; and a Mach-Zehnder (MZM) modulator (17) connected to the light emitter (15) and the vector signal generator (18), and to the first FIFO device (8), and configured to modulate the optical carrier generated by the light emitter according to the representative modulation formats of the communications signal and transmit it to the first FIFO device.

9. The monitoring system according to claim 8, wherein the light emitter (15) configured to generate an optical carrier is a laser and further comprising an isolator element or circulating device (16) connected to the light emitter (15) to provide protection and isolation of the emitted light.

10. A method for monitoring the power supply to a remote node (3) with high-power light using multi-core fibers (MCF) (1) that makes use of the system according to any of claims 1 to 9, and comprising the steps of: a) generating a high-power light beam using the high-power light emitter (HPL) (2); b) sending the high-power light beam to the remote node (3) to power it through the MCF fiber (1) using the FIFO devices (8, 9), and characterized in that it comprises the steps of: c) obtaining backscatter reflected light; d) sending the backscatter reflected light to the feedback photodetector (5) through the MCF fiber (1) using the FIFO devices (8, 9), and e) detecting and monitoring the backscatter reflected light using the feedback photodetector (5), which generates a first voltage representative of the detected reflected light, and the processing module (4).

11. The monitoring method according to claim 10, further comprising the steps of: splitting the high-power light beam into a feed beam and a reference beam using the optical splitter (10); detecting the reference beam using the additional photodetector (11), which generates a second voltage representative of the reference beam; amplifying the first voltage and the second voltage using the Lock-ln amplifier (12); and calculating the power supplied to the remote node.

12. The monitoring method according to claim 10, further comprising a stage of transforming optical energy from the high-power light beam into electrical energy by means of the photovoltaic energy converter (13).

13. The monitoring method according to claim 10, wherein the step of detecting and monitoring backscatter reflected light further comprises the sub-steps of: a) setting a threshold for the first feedback photodetector voltage (5) above which, if the backscatter reflected light is greater, a fault is deemed to have occurred; and b) switching off the high-power light emitter (HPL) (2) when the determined threshold is exceeded.

14. The monitoring method according to the preceding claims, wherein the high-power light is emitted by sweeping through powers from 23 dBm to 33 dBm.

15. The monitoring method according to the preceding claims, further comprising an analysis step of the first voltage, representative of the light reflected by backscattering, compared to the emitted power sweep when the first FIFO device (8) is disconnected from the multicore fibers (MCF) (1); when the second FIFO device (9) is disconnected from the multicore fibers (MCF) (1); or when the first FIFO device (8) and the second FIFO device (9) are properly connected to the multicore fibers (MCF) (1). [0001] [0002]DECLARATION PURSUANT TO PARAGRAPH 1 OF ARTICLE 19 [0003]In accordance with Article 19.1 of the PCT, a new set of claims has been filed replacing the set of claims originally filed, in which the following modifications have been made: [0004]- Claims 1 and 10 have been amended to adopt the two-part format in the claims, in accordance with the Examiner's suggestion. [0005]- Claim 9 has been amended to be dependent on claim 8, according to the Examiner's suggestion. [0006]- Claim 15 has been amended to explain more clearly the embodiments shown in Figure 6 and in the original description page 10 lines 21 to 26, according to the Examiner's suggestion.

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