Optical communication equipment

Abstract

To provide a technology for controlling a light beam without using a motor. [Solution] The optical communication device comprises a plurality of transmitting means that transmit light beams based on input signals, a processing means configured to output a transmission signal to be transmitted to another optical communication device to each of the plurality of transmitting means, and a control means that controls the processing means so that the transmission signal is output to one or more first transmitting means among the plurality of transmitting means, and the one or more first light beams transmitted by the one or more first transmitting means include a light beam that reaches the other optical communication device.

Description

[Technical Field]

[0001] The present disclosure relates to optical communication devices used in Free Space Optics (FSO) communication systems. [Background technology]

[0002] FSO communication is a communication method that transmits optical signals through free space rather than using a fixed medium such as optical fiber. In the following description, the optical signal transmitted in free space for FSO communication is referred to as an "optical beam." Optical communication devices for FSO communication (hereinafter simply referred to as optical communication devices) can be installed on the ground or mounted on moving objects such as satellites, ships, and aircraft. An optical communication device installed on the ground can communicate with other optical communication devices installed on the ground or other optical communication devices mounted on moving objects. Furthermore, an optical communication device mounted on a moving object can communicate with other optical communication devices installed on the ground or other optical communication devices mounted on other moving objects.

[0003] When at least one of two optical communication devices performing communication is mounted on a moving object, the relative positional relationship between the two optical communication devices changes over time. For this reason, the optical communication device is configured to control the direction of the transmitted optical beam so that the transmitted optical beam reaches the other optical communication device with which the optical communication device is communicating. Non-Patent Document 1 discloses a configuration in which an optical communication device is configured to transmit light reflected by a mirror as an optical beam, and the direction of the optical beam is controlled by driving the mirror with a motor. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Martynas,et.,al.,"A Review of Mechanical Fine-Pointing Actuators for Free-Space Optical Communication",Aerospace 2024,11,5 Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration described in Non-Patent Document 1, which uses a motor as a power source to control the direction of a light beam, when the optical communication device is used in an environment where vibrations occur, the direction of the light beam is likely to deviate from the target direction due to the influence of vibrations. For example, when an optical communication device is mounted on a moving object, it is difficult to suppress vibrations, which can degrade the accuracy of the direction control of the light beam. Furthermore, when an optical communication device is mounted on a moving object, particularly an artificial satellite, a lightweight and compact optical communication device is required. However, a configuration in which the direction of the light beam is controlled using a motor as a power source results in an optical communication device that is large in size and mass.

[0006] The present disclosure provides a technique for controlling a light beam without relying on a motor. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, an optical communication device comprises a plurality of transmitting means for transmitting optical beams based on an input signal, a processing means configured to output a transmission signal to be transmitted to another optical communication device to each of the plurality of transmitting means, and a control means for controlling the processing means so that the transmission signal is output to one or more first transmitting means among the plurality of transmitting means, and the one or more first optical beams transmitted by the one or more first transmitting means include an optical beam that reaches the other optical communication device. [Effects of the Invention]

[0008] According to the present disclosure, a light beam can be controlled without relying on a motor. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic block diagram of an optical communication device, according to some embodiments. [Figure 2] FIG. 10 is a diagram showing an example of an irradiation area of ​​each of eight light beams. [Figure 3] FIG. 2 is a diagram showing an example of the arrangement of a transmitter and a receiver. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0011] First Embodiment 1 is a schematic diagram of the transmitting side of an optical communication device according to this embodiment. Note that the optical communication device also has a configuration for receiving and demodulating an optical beam transmitted by another optical communication device as a communication partner, but since this is irrelevant to the description of this embodiment, the configuration of the receiving side will be omitted.

[0012] The optical communication device has N transmitters 1-1 to 1-N that transmit optical beams based on input transmission signals. N is an integer equal to or greater than 2. The transmitters 1-n (n is an integer from 1 to N) are connected to ports P#n of a processing unit 3. The transmitters 1-1 to 1-N have the same configuration, and hereinafter, when there is no need to distinguish between the transmitters 1-1 to 1-N, they will be collectively referred to as a transmitter 1. The transmitter 1 has a light source, such as a laser diode, that generates an optical beam based on the transmission signal. The transmitter 1 may further have optical components such as lenses for adjusting the shape and transmission direction of the optical beam generated by the light source. In the following description, the optical beam transmitted by the transmitter 1-n will be referred to as an optical beam #n. Furthermore, the n in optical beam #n is defined as the "number" of the optical beam.

[0013] In this embodiment, the transmitters 1-1 to 1-N are configured so that the light beams #1 to #N they transmit are different from one another. In this embodiment, two light beams being different means that at least a portion of the spatial region through which the two light beams pass is different. In other words, if the spatial region through which the two light beams pass is exactly the same, the two light beams are the same; otherwise, the two light beams are different from one another. Therefore, the spatial region through which two different light beams pass may partially overlap. Furthermore, in this embodiment, the transmitters 1-1 to 1-N may be configured so that the spatial region through which the light beams #1 to #N pass is continuous as a whole.

[0014] As an example, Fig. 2 shows an area on the ground (hereinafter referred to as the irradiation area) irradiated by optical beams #1 to #8 transmitted by transmitters 1-1 to 1-8 of optical communication devices mounted on an artificial satellite. In Fig. 2, one circle indicates an irradiation area by one optical beam, and the number written in the center of the circle indicates the number of the optical beam. According to Fig. 2, the irradiation areas of optical beams #1 to #8 are continuous as a whole.

[0015] Returning to FIG. 1, a transmission signal is input to port P#0 of the processing unit 3. The transmission signal is a signal that carries information to be transmitted to another optical communication device as a communication partner. In this embodiment, the processing unit 3 is configured to output the transmission signal input to port P#0 to one of ports P#1 to P#N in accordance with the control of the control unit 5. Therefore, in this embodiment, at a given moment, the optical communication device transmits only one optical beam.

[0016] The control unit 5 determines the optical beam that will reach the other optical communication device, i.e., that will irradiate the other optical communication device, based on the relative positional relationship between the optical communication device (hereinafter simply referred to as "optical communication device") in which the control unit 5 is implemented and the other optical communication device (hereinafter simply referred to as "other optical communication device") that is the communication partner.Then, the control unit 5 controls the processing unit 3 so that the determined optical beam is transmitted, i.e., so that a transmission signal is input to the transmitting unit 1 that transmits the determined optical beam.

[0017] In one example, the control unit 5 determines the position of the optical communication device and the position of another optical communication device, and determines the relative position of the other optical communication device with respect to the optical communication device based on the position of the optical communication device and the position of the other optical communication device. For example, if the optical communication device is installed on the ground, the installation position of the optical communication device is known. Also, if the optical communication device is installed on a satellite, the position of the satellite, i.e., the position of the optical communication device, can be determined using orbital information. Furthermore, if the optical communication device is installed on an aircraft or a ship, the position of the aircraft or ship, i.e., the position of the optical communication device, can be obtained from a GPS or an aircraft or ship management system. The same applies to cases where the other optical communication device is installed on the ground or installed on a moving object. Note that the control unit 5 stores information necessary to determine the position of the optical communication device and the position of the other optical communication device in advance. Alternatively, the control unit 5 may be configured to acquire information necessary to determine the position of the optical communication device and the position of the other optical communication device from another device.

[0018] The control unit 5 selects the optical beam to be actually transmitted so that the optical beam irradiates the other optical communication device based on the relative position of the other optical communication device with respect to the optical communication device.

[0019] In addition, an imaging device can be provided in the optical communication device, and other optical communication devices can be identified using image recognition technology based on images captured by the imaging device, thereby determining the relative positions of the other optical communication devices in relation to the optical communication device.

[0020] The receiving units 2-1 to 2-N and the detecting unit 4 in FIG. 1 are provided in the optical communication device described in the fourth embodiment, but are not provided in the optical communication devices of the first to third embodiments.

[0021] As described above, according to this embodiment, an optical communication device is configured to transmit multiple different optical beams. The control unit 5 determines the relative position of another optical communication device with respect to the optical communication device in which the control unit 5 is implemented, and determines one optical beam that will arrive at the other optical communication device as the destination of the transmitted signal based on the determined relative position. The control unit 5 then controls the processing unit 3 so that a transmission signal is output to the transmitting unit 1, which transmits the determined one optical beam. This configuration makes it possible to electrically control the direction of the optical beam without using a motor. Therefore, the influence of vibration can be suppressed and the direction of the optical beam can be controlled with high precision, and the optical communication device can be made smaller and lighter.

[0022] In addition, in this embodiment, the optical communication device transmits only one optical beam at a given moment. For example, when the optical communication device is mounted on a moving object, it may be required to reduce power consumption. In this embodiment, the number of optical beams transmitted at a given moment is one, so that the power consumption of the optical communication device can be reduced.

[0023] Although the description has been given using an example in which there is one other optical communication device, the optical communication device can communicate with multiple other optical communication devices, for example, by time division multiplexing or the like. For example, suppose there are three other optical communication devices, a first optical communication device, a second optical communication device, and a third optical communication device, and optical beam #1 is used for the first optical communication device, optical beam #2 is used for the second optical communication device, and optical beam #1 is used for the third optical communication device. In this case, the control unit 5 controls the processing unit 3 so that, during a period in which a transmission signal to the first optical communication device and the third optical communication device is input to the processing unit 3, the transmission signal is output from port P#1, and during a period in which a transmission signal to the second optical communication device is input to the processing unit 3, the transmission signal is output from port P#2.

[0024] Second Embodiment Next, the second embodiment will be described, focusing on the differences from the first embodiment. The configuration of the optical communication device according to this embodiment is the same as that shown in FIG. 1. In the first embodiment, the number of optical beams transmitted at a given moment was one. In this embodiment, transmission of multiple optical beams is permitted. For this reason, the processing unit 3 in this embodiment is configured to be able to simultaneously output a transmission signal input to port P#0 to two or more of ports P#1 to P#N in accordance with the control of the control unit 5.

[0025] Generally, the power density of an optical beam is higher in the center and lower in the outermost portion. Therefore, if another optical communication device is located in the outermost portion of the irradiation area of ​​optical beam #1, the signal-to-noise ratio of the optical beam received by the other optical communication device may be degraded. For this reason, in this embodiment, multiple optical beams are transmitted whose irradiation areas overlap each other. Note that the area irradiated by the multiple optical beams is the outermost portion of each of the multiple optical beams. For example, if the other communication device is located in the area where the irradiation area of ​​optical beam #1 and the irradiation area of ​​optical beam #2 in Figure 2 overlap, the control unit 5 controls the processing unit 3 so that the transmission signal is output simultaneously from both port P#1 and port P#2 of the processing unit 3.

[0026] It should be noted that simultaneous transmission of multiple light beams increases the power consumption of the optical communication device. In order to suppress the increase in power consumption of the optical communication device, when multiple light beams are transmitted simultaneously, the transmission power of each light beam can be configured to be lower than the transmission power when only one transmission beam is transmitted (in the first embodiment). In this case, the control unit 5 is configured to be able to control the transmission power of the light beams by controlling the transmission unit 1.

[0027] As described above, when the control unit 5 determines, based on the relative positional relationship with the other optical communication device, that there are multiple optical beams that will reach the position of the other optical communication device, it controls the processing unit 3 so that a transmission signal to the other optical communication device is input to the transmitting unit 1, which transmits each of the multiple optical beams. The position that is commonly irradiated by each of the multiple optical beams is the outer extension of each of the multiple optical beams. Therefore, if only one of the multiple optical beams is transmitted, the quality of the signal received by the other optical communication device may deteriorate. On the other hand, by transmitting each of the multiple optical beams, deterioration in the quality of the signal received by the other optical communication device can be suppressed.

[0028] In addition, when there are three or more optical beams that reach the position of the other optical communication device, the configuration may be such that, rather than transmitting all of the optical beams that reach the position of the other optical communication device, only at least two optical beams selected from the three or more optical beams that reach the position of the other optical communication device are transmitted.

[0029] Third Embodiment Next, a third embodiment will be described, focusing on the differences from the first embodiment. The configuration of the optical communication device according to this embodiment is the same as that shown in Fig. 1. For example, if the relative position of the optical communication device with respect to the other optical communication device cannot be determined accurately due to low accuracy in determining the position of the optical communication device or the position of the other optical communication device, in the configuration of the first embodiment, a non-optimal optical beam may be selected for communication with the other optical communication device.

[0030] For example, assume that the control unit 5 determines that another optical communication device is located within the irradiation area of ​​optical beam #1 in FIG. 2. In the first embodiment, the control unit 5 controls the processing unit 3 so that a transmission signal is output from port P#1 of the processing unit 3. However, considering the accuracy of determining the relative position, the other optical communication device may actually be located within the irradiation area of ​​optical beam #2 or optical beam #5, rather than optical beam #1. If the other optical communication device is actually located within the irradiation area of ​​optical beam #2 or optical beam #5, the configuration of the first embodiment will result in a suboptimal optical beam being selected for communication with the other optical communication device. Therefore, in this embodiment, multiple optical beams are selected and transmitted in sequence. In other words, in this embodiment, scanning is performed with multiple optical beams.

[0031] For this reason, the control unit 5 determines an area where another optical communication device may exist, taking into account the accuracy of the determination of the relative position. For example, the control unit 5 determines a relative position, and based on the determined relative position and the determination accuracy, determines an area including the determined relative position as an area where another optical communication device may exist. Note that the size of the area where it is determined that another optical communication device may exist may be larger as the determination accuracy becomes lower. For example, the area where it is determined that another optical communication device may exist is a circle centered on the determined relative position, and the radius of the circle becomes larger as the determination accuracy becomes lower.

[0032] When the determined area is to be irradiated with only one light beam, the control unit 5 controls the processing unit 3 to transmit only that one light beam, as in the first embodiment. On the other hand, when there are multiple light beams irradiating the determined area, the control unit 5 controls the processing unit 3 to transmit the multiple light beams in sequence. Note that when there are multiple light beams irradiating the determined area, each of the multiple light beams irradiates only a portion of the determined area.

[0033] For example, assume that the area where other optical communication devices may exist partially includes the irradiation areas of the optical beams #1, #2, and #5 in FIG. 2. In this case, the control unit 5 first controls the processing unit 3 so that the transmission signal is output only from port P#1 of the processing unit 3. Next, the control unit 5 controls the processing unit 3 so that the transmission signal is output only from port P#2 of the processing unit 3. Next, the control unit 5 controls the processing unit 3 so that the transmission signal is output only from port P#5 of the processing unit 3. This completes the processing for one cycle. When the processing for one cycle is completed, the control unit 5 starts processing for the next cycle. Note that the transmission signals output from ports P#1, P#2, and P#5 of the processing unit 3 are the same in one cycle. For this reason, the processing unit 3 of this embodiment has a buffer that holds the transmission signal for one cycle.

[0034] In this embodiment, the transmitted optical beams are switched in sequence, but as in the second embodiment, multiple optical beams can also be transmitted simultaneously. For example, if the area where other optical communication devices may exist partially includes each of the irradiation areas of optical beams #1, #2, and #5 in Figure 2, the control unit 5 can control the processing unit 3 so that optical beams #1, #2, and #5 are transmitted simultaneously. In this case, there is no need to provide a buffer in the processing unit 3.

[0035] As described above, according to this embodiment, when the accuracy of determining the relative positional relationship with other optical communication devices is low, it is possible to prevent an appropriate light beam from being selected, thereby preventing a deterioration in communication quality.

[0036] <Fourth embodiment> Next, the fourth embodiment will be described, focusing on differences from the first and second embodiments. In this embodiment, an optical communication device is provided with receivers 2-1 to 2-N and a detector 4, as shown in FIG. 1. The optical communication device is configured to transmit an optical beacon signal separate from the optical beam. In the following description, when it is not necessary to distinguish between the receivers 2-1 to 2-N, they will be collectively referred to as a receiver 2. The receiver 2 includes a photoelectric conversion device, such as a photodiode, that receives the optical beacon signal and outputs an electrical signal. The receiver 2 may further include an optical element, such as a lens, for inputting the optical beacon signal to the photoelectric conversion device. When the receivers 2-1 to 2-N receive an optical beacon signal transmitted by another optical communication device, the receivers 2-1 to 2-N each output an electrical signal corresponding to the optical beacon signal to the detector 4 as a reception result. The detector 4 notifies the controller 5 of the receiver 2 that received the optical beacon signal based on the electrical signal from the receiver 2-1 to 2-N.

[0037] In this embodiment, the transmitter 1 and receiver 2 are configured so that an optical beacon signal transmitted by another optical communication device present within the irradiation area of ​​the optical beam #n transmitted by the transmitter 1-n is received by the receiver 2-n. Therefore, the transmitter 1-n and receiver 2-n are associated with each other and form a pair. For example, when the receiver 2-2 receives an optical beacon signal from another optical communication device, the controller 5 controls the processor 3 so that the transmission signal to the other optical communication device is output only to port #2 of the processor 3, as in the first embodiment.

[0038] Furthermore, when the receiving unit 2-1 and the receiving unit 2-2 each receive an optical beacon signal from another optical communication device, the control unit 5, as in the second embodiment, controls the processing unit 3 so that a transmission signal to the other optical communication device is output to each of the ports P#1 and P#2 of the processing unit 3. Note that even when the receiving unit 2-1 and the receiving unit 2-2 each receive an optical beacon signal from another optical communication device, the processing unit 3 may be controlled so that the transmission signal is output to only one of the ports P#1 and P#2 of the processing unit 3, and only one optical beam may be transmitted.

[0039] Fig. 3 shows an example of the arrangement of transmitters 1-1 to 1-8 and receivers 2-1 to 2-8 when N=8. Note that the unshaded circle indicates the emission surface of the light beam from transmitter 1, and the shaded circle indicates the incidence surface of the optical beacon signal to receiver 2. Also, the p in #p (p is an integer from 1 to 8) within the circle indicates transmitter 1-p or receiver 2-p. In Fig. 3, transmitters 1-1 to 1-8 and receivers 2-1 to 2-8 are arranged two-dimensionally, but they may also be arranged one-dimensionally.

[0040] 3(B) shows a case where multiple transmitters 1 are arranged close to each other and multiple receivers 2 are arranged close to each other. If the optical beam from the transmitter 1 reaches another optical communication device, and if the optical beacon signal from the other optical communication device is received by the receiver 2 that forms a pair with the transmitter 1, then the arrangement shown in FIG. 3(B) is possible.

[0041] However, if an optical beam from a transmitter 1 reaches another optical communication device, in order to ensure that an optical beacon signal from the other optical communication device is received by a receiver 2 paired with the transmitter 1, it is preferable to arrange the paired transmitters 1 and receivers 2 close to each other, as shown in Fig. 3(A). In Fig. 3(A), each transmitter 1 and each receiver 2 are arranged so that no other transmitters 1 or receivers 2 are arranged between a certain transmitter 1 and the receiver 2 paired with the certain transmitter 1. Alternatively, in Fig. 3(A), each transmitter 1 and each receiver 2 are arranged so that the minimum distance between a certain transmitter 1 and each of the other transmitters 1 and receivers 2 is the distance between the certain transmitter 1 and the receiver 2 paired with the certain transmitter 1.

[0042] As described above, according to this embodiment, the receiver 2 that receives the optical beacon signal can determine the transmitter 1 to use to transmit the optical beam without determining the relative position of other optical communication devices with respect to the optical communication device. In this embodiment, the optical communication device transmits an optical beam signal. However, it may also be configured to transmit a wireless beacon signal instead of an optical one. In this case, the receiver 2 receives a wireless beacon signal.

[0043] The above configuration makes it possible to control light beams without using a motor, which will contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization, and foster innovation." [Explanation of symbols]

[0044] 1-1 to 1-N: transmitter, 3: processor, 5: controller

Claims

1. An optical communication device, a plurality of transmitting means for transmitting light beams based on input signals; a processing means configured to be able to output a transmission signal to be transmitted to another optical communication device to each of the plurality of transmitting means; a control means for controlling the processing means so that the transmission signal is output to one or more first transmission means among the plurality of transmission means; Equipped with An optical communication device, wherein the one or more first light beams transmitted by the one or more first transmitting means include a light beam that reaches the other optical communication device.

2. 2. The optical communication device of claim 1, wherein the control means determines the relative position of the other optical communication device with respect to the optical communication device, and determines the one or more first transmitting means by determining the one or more first light beams based on the relative position.

3. 3. The optical communication device according to claim 2, wherein, when the optical communication device is mounted on a first artificial satellite, the control means determines the relative position by calculating the position of the optical communication device based on orbital information of the first artificial satellite.

4. 3. The optical communication device according to claim 2, wherein, when the other optical communication device is mounted on a second artificial satellite, the control means determines the relative position by calculating the position of the other optical communication device based on orbital information of the second artificial satellite.

5. further comprising an imaging device; 3. The optical communication device according to claim 2, wherein the control means determines the relative position based on an image including the other optical communication device captured by the imaging device.

6. The optical communication device according to claim 2 , wherein the one or more first optical beams are one first optical beam that reaches the other optical communication device.

7. The optical communication device according to claim 2 , wherein the one or more first optical beams are a plurality of first optical beams including at least two first optical beams that reach the other optical communication device.

8. The optical communication device according to claim 2 , wherein the control means determines an area including the relative position, and determines the one or more first light beams based on the area.

9. 9. The optical communication device according to claim 8, wherein the control means determines the size of the area based on the accuracy of determining the relative position.

10. The optical communication device according to claim 8 , wherein when the one or more first light beams are a plurality of first light beams, each of the plurality of first light beams illuminates a part of the region.

11. 9. The optical communication device according to claim 8, wherein, when the one or more first transmitting means are a plurality of first transmitting means, the control means controls the processing means so that the transmission signal is input to the plurality of first transmitting means in sequence.

12. 9. The optical communication device according to claim 8, wherein, when the one or more first transmitting means are a plurality of first transmitting means, the control means controls the processing means so that the transmission signal is input to each of the plurality of first transmitting means.

13. a plurality of receiving means for receiving beacon signals transmitted by the other optical communication devices; 2. The optical communication device according to claim 1, wherein the control means determines the one or more first transmission means based on one or more first reception means among the plurality of reception means that have received the beacon signal.

14. the plurality of transmitting means and the plurality of receiving means are associated one-to-one; the plurality of transmitting means and the plurality of receiving means are configured so that an optical beam transmitted by a transmitting means associated with a receiving means for receiving the beacon signal transmitted by the other optical communication device reaches the other optical communication device; 14. The optical communication device according to claim 13, wherein the control means determines that one or more transmitting means associated with the one or more first receiving means are the one or more first transmitting means.

15. 15. An optical communication device according to claim 1, wherein the control means controls the one or more first transmitting means so that the transmission power of the optical beam transmitted by each of the plurality of first transmitting means when the one or more first transmitting means are a plurality of first transmitting means is smaller than the transmission power of the optical beam transmitted by the one first transmitting means when the one or more first transmitting means are a single first transmitting means.

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