Optical wireless communication system and optical wireless communication device

Abstract

In an optical wireless communication system equipped with a pair of optical wireless communication devices (1), the optical wireless communication device (1) is equipped with a plurality of optical transmitting units (101) that transmit optical signals of a target wavelength, an optical multiplexing / demultiplexing unit (103) that multiplexes the optical signals transmitted by the optical transmitting units (101) and transmits the multiplexed optical signals to the counterpart optical wireless communication device (1) and demultiplexes the optical signals from the counterpart optical wireless communication device (1) into optical signals of a plurality of wavelengths, and a plurality of optical receiving units (102) that receive optical signals of a target wavelength from the optical signals demultiplexed by the optical multiplexing / demultiplexing unit (103), and the wavelengths that are the target of the optical transmitting units (101) and the optical receiving units (102) are wavelengths that are alternately assigned in order of length, and between the pair of optical wireless communication devices (1), the wavelengths that are the target of the optical transmitting units (101) and the optical receiving units (102) are shifted by one.

Description

[Technical field]

[0001] The present disclosure relates to an optical wireless communication system including an optical wireless communication device that transmits and receives optical signals, and to the optical wireless communication device. [Background technology]

[0002] Free-space optical communications, particularly inter-satellite optical communications, are expected to become widespread. For example, Non-Patent Document 1 indicates that, as an inter-satellite communication standard, with reference to ITU-T G.694.1, two wavelengths of 193.1+n×0.1 THz (n=−1, +20) are allocated for transmission and reception.

[0003] In addition, these wavelengths must be software-switchable, that is, the wavelengths for transmission and reception must be interchangeable, because in free-space optical communications, especially in inter-satellite optical communications, it is necessary to switch the wavelengths for transmission and reception to avoid crosstalk between communicating devices. For example, of two devices, one device assigns Tx to CH_A and Rx to CH_B, and the other device assigns Rx to CH_A and Tx to CH_B. In addition, each device can switch the wavelengths assigned to Tx and Rx.

[0004] The reason that the two wavelengths are so wide relative to the 100 GHz of the ITU-T grid is to facilitate wavelength separation. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Optical Communications Terminal (OCT) Standard Version 3.0 Summary of the Invention [Problem to be solved by the invention]

[0006] In spatial optical communications, there are two possible methods for improving the communication bandwidth: increasing the amount of information per wavelength, i.e., increasing the modulation speed, and increasing the number of wavelengths (WDM: Wavelength Division multiplexing).

[0007] Methods for increasing the modulation speed are subject to a trade-off with receiver sensitivity. In inter-satellite optical communications, which require link lengths of several thousand kilometers, beam divergence in free space is unavoidable, and the power reaching the receiver is extremely low. Therefore, this method of increasing the modulation rate is not preferable since high receiving sensitivity is essential for the system.

[0008] In contrast, the method of increasing the number of wavelengths is a technology for improving the communication bandwidth without changing the modulation speed, and is also widely used in optical fiber communications. On the other hand, in the communication disclosed in Non-Patent Document 1, as described above, it is necessary to programmatically switch between the transmission wavelength and the reception wavelength.

[0009] The most reliable method for achieving this wavelength switching is to prepare a device compatible with each wavelength. However, this method has the problem of large size and high cost of the apparatus.

[0010] On the other hand, another method for realizing wavelength switching is to prepare a wavelength-tunable light source and switch the wavelength according to demand. In this method, the wavelength filter for separating the transmission wavelength from the reception wavelength must be tunable, but it is difficult to switch wavelengths with commonly used multilayer filters.

[0011] Moreover, in the case of the wavelength grid (193.1+n×0.1 THz (n=−1, +20)) shown in Non-Patent Document 1, there are only two wavelengths for transmission and reception. However, when multiple wavelengths are used in order to realize a larger capacity in the future, the system will become very complicated no matter which of the above wavelength switching methods is used.

[0012] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical wireless communication system that can implement a larger number of wavelengths and makes it easier to switch wavelengths than conventional systems. [Means for solving the problem]

[0013] The optical wireless communication system according to the present disclosure is an optical wireless communication system including a pair of optical wireless communication devices, the optical wireless communication devices including a plurality of optical transmitting units that transmit optical signals of a target wavelength, an optical multiplexing / demultiplexing unit that multiplexes the optical signals transmitted by the optical transmitting units and transmits the multiplexed optical signals to a counterpart optical wireless communication device, and demultiplexes the optical signals from the counterpart optical wireless communication device into optical signals of a plurality of wavelengths, and a plurality of optical receiving units that receive the optical signals of the target wavelength from the optical signals demultiplexed by the optical multiplexing / demultiplexing unit. a wavelength filter provided for each optical receiving unit, which transmits optical signals of two wavelengths that can be targeted by the corresponding optical receiving unit among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; The wavelengths targeted by the optical transmitting unit and the optical receiving unit are alternately assigned in the order of length, and between a pair of optical wireless communication devices, the wavelengths targeted by the optical transmitting unit and the optical receiving unit are shifted by one, the optical multiplexing / demultiplexing unit is an AWG, and the number of ports is one more than the total number of wavelengths targeted by the optical transmitting unit and the optical receiving unit. The optical receiver receives the optical signal transmitted through the wavelength filter. It is characterized by: Effect of the Invention

[0014] According to the present disclosure, since it is configured as described above, it is possible to implement a larger number of wavelengths than in the past, and it is easy to switch between wavelengths. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram illustrating a configuration example of an optical wireless communication system according to a first embodiment. [Diagram 2] 2 is a diagram illustrating an example of an arrangement of wavelengths targeted by the optical wireless communication system according to the first embodiment. FIG. [Diagram 3] 1 is a diagram illustrating a configuration example of a first optical wireless communication device according to a first embodiment. [Figure 4] 4 is a diagram illustrating an example of the configuration of a second optical wireless communication device according to the first embodiment. [Diagram 5] 4 is a diagram illustrating an example of setting wavelengths targeted by a first optical wireless communication device and wavelengths targeted by a second optical wireless communication device according to the first embodiment. FIG. [Figure 6] FIG. 11 is a diagram illustrating a configuration example of a first optical wireless communication device according to a second embodiment. [Figure 7] FIG. 11 is a diagram illustrating a configuration example of a first optical wireless communication device according to a third embodiment. [Figure 8] FIG. 11 is a diagram showing an example of setting a band targeted by a first wavelength filter in the third embodiment. [Figure 9] FIG. 13 is a diagram illustrating a configuration example of a first optical wireless communication device according to a fourth embodiment. [Figure 10] FIG. 13 is a diagram illustrating an example of the configuration of a second optical wireless communication device according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments will be described in detail with reference to the drawings. Embodiment 1 FIG. 1 is a diagram showing an example of the configuration of an optical wireless communication system according to the first embodiment. The optical wireless communication system is a system that includes a pair of optical wireless communication devices 1 and performs communication between the pair of optical wireless communication devices 1. As shown in FIG. 1, this optical wireless communication system includes a first optical wireless communication device 1-1 and a second optical wireless communication device 1-2.

[0017] In addition, when it is necessary to distinguish between the optical wireless communication device 1 and the components included in the optical wireless communication device 1, suffixes (-1, -2) are added to the reference numerals.

[0018] In addition, the following description will be given taking as an example communication between satellites 10 on which the optical wireless communication device 1 is mounted, as an example of communication performed by the optical wireless communication device 1. However, the communication performed by the optical wireless communication device 1 is not limited to this, and may be, for example, communication for land or aircraft, and the optical wireless communication device 1 can have a similar configuration.

[0019] FIG. 2 shows an example of an arrangement of wavelengths targeted by the optical wireless communication system according to the first embodiment. Here, the wavelengths targeted by the optical wireless communication system are arranged in a 21-wavelength grid at 100 GHz intervals, as shown in Fig. 2. In the example of Fig. 2, the wavelength grid is the wavelength grid (193.1+n×0.1 THz (n=0,...,20)) specified in ITU-T G.694.1. The 100 GHz interval corresponds to approximately 0.8 nm. In FIG. 2, λ0 to λ 20 indicates the wavelengths that are targeted by the optical wireless communication system.

[0020] As shown in FIG. 1, for example, a first optical wireless communication device 1-1 is mounted on a first satellite 10-1 and communicates with a counterpart, a second optical wireless communication device 1-2. As shown in FIG. 3, the first optical wireless communication device 1-1 includes a plurality of first optical transmitters (Tx) 101-1, a plurality of first optical receivers (Rx) 102-1, and a first optical multiplexer / demultiplexer (AWG) 103-1.

[0021] The first optical transmitter 101-1 transmits an optical signal of a target wavelength to the first optical multiplexer / demultiplexer 103-1.

[0022] For example, a semiconductor laser is used as the first optical transmission unit 101-1. For example, a DML (Directly Modulated Laser) or an EML (Electro-absorption modulator integrated Laser diode) with an integrated optical modulator is used as the semiconductor laser. The oscillation wavelength of the DML and the oscillation wavelength of the EML have a temperature characteristic of, for example, about 0.08 nm / K, and the wavelength of the output optical signal can be changed by changing the temperature.

[0023] The first optical receiving section 102-1 receives an optical signal of a target wavelength from among the optical signals demultiplexed by the first optical multiplexing / demultiplexing section 103-1.

[0024] As the first optical receiving unit 102-1, for example, an APD (Avalanche Photo Diode) is used. This APD can receive light in any wavelength band it is sensitive to, regardless of temperature.

[0025] The wavelengths targeted by each of the first optical transmitting units 101-1 and each of the first optical receiving units 102-1 are wavelengths that are alternately assigned in order of length from among the multiple wavelengths targeted by the first optical wireless communication device 1-1. In the example of FIG. 3, each of the first optical transmitters 101-1 has λ0, λ2, . . . , λ 18 , λ to each of the first optical receiving units 102-1. 19 is assigned.

[0026] The first optical multiplexing / demultiplexing unit 103-1 is an optical waveguide having multiple ports for multiplexing / demultiplexing optical signals. The first optical multiplexing / demultiplexing unit 103-1 has a function of demultiplexing wavelength-multiplexed light to multiple ports, and a function of multiplexing light of a specific wavelength input to the multiple ports. That is, the first optical multiplexing / demultiplexing unit 103-1 multiplexes the optical signals transmitted by the first optical transmitting unit 101-1 and transmits them to the second optical wireless communication device 1-2, and also demultiplexes the optical signals transmitted by the second optical wireless communication device 1-2 into optical signals of multiple wavelengths.

[0027] 3, an AWG (Array Waveguide Gratings) is used as the first optical multiplexing / demultiplexing section 103-1. The AWG is an optical waveguide made of quartz, silicon, silicon nitride, or the like.

[0028] The spectral characteristics of this AWG have a temperature dependency of, for example, about 0.08 nm / K, and exhibit a behavior in which the port of the corresponding wavelength shifts to the adjacent one when the temperature is changed. When an AWG made of quartz is used as the first optical multiplexing / demultiplexing section 103-1, the first optical transmitting section 101-1 and the first optical receiving section 102-1 are alternately connected to each port such that the first optical transmitting section 101-1 is connected to the first port (port1) and the first optical receiving section 102-1 is connected to the second port (port2) as shown in Figures 3 and 5. In Figure 5, reference numeral 51 denotes a wavelength that can be used for communication in the optical wireless communication system.

[0029] When the first optical multiplexing / demultiplexing section 103-1 is an AWG, the first optical wireless communication device 1-1 may include a temperature control section that controls the temperature of the first optical multiplexing / demultiplexing section 103-1. Furthermore, when the first optical transmitting unit 101-1 is a DML or EML, the first optical wireless communication device 1-1 may include a temperature control unit that controls the temperature of the first optical transmitting unit 101-1.

[0030] As shown in FIG. 1, for example, the second optical wireless communication device 1-2 is mounted on a second satellite 10-2 and communicates with the counterpart first optical wireless communication device 1-1. As shown in FIG. 4, the second optical wireless communication device 1-2 includes a plurality of second optical transmitters (Tx) 101-2, a plurality of second optical receivers (Rx) 102-2, and a second optical multiplexer / demultiplexer (AWG) 103-2.

[0031] The second optical transmitter 101-2 transmits an optical signal of a target wavelength to the second optical multiplexer / demultiplexer 103-2.

[0032] For example, a semiconductor laser is used as the second optical transmitter 101-2. As the semiconductor laser, for example, a DML or an EML with an integrated optical modulator is used. The oscillation wavelength of the DML and the oscillation wavelength of the EML have a temperature characteristic of, for example, about 0.08 nm / K, and the wavelength of the output optical signal can be changed by changing the temperature.

[0033] The second optical receiving section 102-2 receives an optical signal of a target wavelength from among the optical signals demultiplexed by the second optical multiplexing / demultiplexing section 103-2.

[0034] The second optical receiving unit 102-2 may be, for example, an APD. This APD can receive light in any wavelength band it is sensitive to, regardless of temperature.

[0035] The wavelengths targeted by each of the second optical transmitting units 101-2 and each of the second optical receiving units 102-2 are wavelengths that are alternately assigned in order of length from among the multiple wavelengths targeted by the second optical wireless communication device 1-2. In the example of FIG. 4, the second optical transmitters 101-2 have wavelengths λ1, λ3, . . . , λ 19 , λ to each of the second optical receiving units 102-2. 20 is assigned.

[0036] The second optical multiplexing / demultiplexing unit 103-2 is an optical waveguide having multiple ports and performing multiplexing / demultiplexing of optical signals. The second optical multiplexing / demultiplexing unit 103-2 has a function of demultiplexing the wavelength-multiplexed light to multiple ports and a function of multiplexing light of a specific wavelength input to the multiple ports. That is, the second optical multiplexing / demultiplexing unit 103-2 multiplexes the optical signals transmitted by the second optical transmitting unit 101-2 and transmits them to the first optical wireless communication device 1-1, and also demultiplexes the optical signals transmitted by the first optical wireless communication device 1-1 into optical signals of multiple wavelengths.

[0037] 3, an AWG is used as the second optical multiplexing / demultiplexing section 103-2. The AWG is an optical waveguide made of quartz, silicon, silicon nitride, or the like.

[0038] The spectral characteristics of this AWG have a temperature dependency of, for example, about 0.08 nm / K, and exhibit a behavior in which the port of the corresponding wavelength shifts to the adjacent one when the temperature is changed. When an AWG made of quartz is used as the second optical multiplexing / demultiplexing section 103-2, the second optical transmitting section 101-2 and the second optical receiving section 102-2 are alternately connected to each port, such that the second optical transmitting section 101-2 is connected to the first port (port1) and the second optical receiving section 102-2 is connected to the second port (port2), as shown in Figures 4 and 5.

[0039] When the second optical multiplexing / demultiplexing section 103-2 is an AWG, the second optical wireless communication device 1-2 may include a temperature control section that controls the temperature of the second optical multiplexing / demultiplexing section 103-2. Furthermore, when the second optical transmitting unit 101-2 is a DML or EML, the second optical wireless communication device 1-2 may include a temperature control unit that controls the temperature of the second optical transmitting unit 101-2.

[0040] Furthermore, as shown in Figures 3 to 5, for example, the wavelengths targeted by the first optical transmitting unit 101-1 and the first optical receiving unit 102-1 in the first optical wireless communication device 1-1 are shifted by one from the wavelengths targeted by the second optical transmitting unit 101-2 and the second optical receiving unit 102-2 in the second optical wireless communication device 1-2. That is, in the examples of FIGS. 3 to 5, the wavelengths targeted by each of the first optical transmission units 101-1 are λ0, λ2, . . . , λ 18 Meanwhile, the wavelengths targeted by each of the second optical transmitters 101-2 are λ1, λ3, . . . , λ 19 3 to 5, the wavelengths targeted by each of the first optical receiving units 102-1 are λ1, λ3, . . . , λ 19 Meanwhile, the wavelengths targeted by each of the second optical receiving units 102-2 are λ2, λ4, . . . , λ 20 In this way, the target wavelengths are shifted by one.

[0041] In addition, if the first optical multiplexing / demultiplexing unit 103-1 and the second optical multiplexing / demultiplexing unit 103-2 are AWGs, the wavelengths are shifted as described above, and therefore, the first optical multiplexing / demultiplexing unit 103-1 and the second optical multiplexing / demultiplexing unit 103-2 each have a port that cannot be used for communication. In the examples of Figures 3 and 5, the first port (port1) of the ports of the first optical multiplexing / demultiplexing unit 103-1 is a port that cannot be used for communication. That is, the first optical wireless communication device 1-1 operates with 19 waves from the short wave side. Similarly, in the examples of Figures 4 and 5, the 20th port (port20) of the ports of the second optical multiplexing / demultiplexing unit 103-2 is a port that cannot be used for communication. That is, the second optical wireless communication device 1-2 operates with 19 waves from the long wave side.

[0042] Moreover, the wavelength settings of the first optical wireless communication device 1-1 and the second optical wireless communication device 1-2 can be programmatically reversed. That is, for example, when the optical transmitting unit 101 is a DML or EML, it is possible to adjust the wavelength of the optical signal from the optical transmitting unit 101 by adjusting the temperature setting value for the optical transmitting unit 101. Also, for example, when the optical multiplexing / demultiplexing unit 103 is an AWG, it is possible to adjust the wavelength corresponding to the port of the optical multiplexing / demultiplexing unit 103 by adjusting the temperature setting value for the optical multiplexing / demultiplexing unit 103. Therefore, by making these adjustments, it becomes possible to programmatically invert the wavelength settings of the first optical wireless communication device 1-1 and the second optical wireless communication device 1-2.

[0043] 2 to 4, among the components of the optical wireless communication device 1, only those parts related to the present disclosure are shown. However, in an actual device, beyond the input / output ports of the optical multiplexing / demultiplexing unit 103, there are provided mechanisms such as a circulator that separates the transmitted and received optical signals, a booster optical amplifier for the transmitted optical signal or a low-noise optical amplifier for the received optical signal, or an optical scanning mechanism that performs tracking between satellites 10.

[0044] Next, an operation example of the optical wireless communication system according to the first embodiment will be described. Communications are performed between the first optical wireless communication device 1-1 mounted on the first satellite 10-1 and the second optical wireless communication device 1-2 mounted on the second satellite 10-2 through the following operations. In the following, it is assumed that the optical transmitting unit 101 is a DML or EML, and the optical multiplexing / demultiplexing unit 103 is an AWG. In the following, a case is shown in which the settings for the second optical wireless communication device 1-2 are changed based on the settings for the first optical wireless communication device 1-1, but the opposite is also possible.

[0045] First, for example, the temperature setting value for the second optical multiplexing / demultiplexing unit 103-2 in the second optical wireless communication device 1-2 is set 10° C. higher than the temperature setting value for the first optical multiplexing / demultiplexing unit 103-1 in the first optical wireless communication device 1-1. As a result, the positional relationship of the port with respect to the wavelength shifts to the neighboring position by approximately 0.8 nm (0.08 nm / K×10K) due to the temperature dependency of the second optical multiplexing / demultiplexing unit 103-2. Furthermore, for example, with respect to the temperature setting value for the first optical transmitting unit 101-1 in the first optical wireless communication device 1-1, the temperature setting value for the second optical transmitting unit 101-2 in the second optical wireless communication device 1-2 is changed by 10° C. As a result, the wavelength changes by 0.8 nm due to the temperature characteristics of the second optical transmitting unit 101-2.

[0046] These adjustments make it possible to invert the wavelength allocation of the second optical transmitting unit 101-2 and the second optical receiving unit 102-2 in the second optical wireless communication device 1-2 from the initial state, thereby shifting the wavelengths targeted by the first optical transmitting unit 101-1 and the first optical receiving unit 102-1 in the first optical wireless communication device 1-1 and the wavelengths targeted by the second optical transmitting unit 101-2 and the second optical receiving unit 102-2 in the second optical wireless communication device 1-2 by one wavelength.

[0047] However, the shortest wavelength in the first optical wireless communication device 1-1 and the longest wavelength in the second optical wireless communication device 1-2 cannot be used for communication. In addition, since the wavelength dependency in the optical receiving unit 102 is small, the change in the wavelength of the optical signal caused by changing the temperature setting value for the optical multiplexing / demultiplexing unit 103 does not affect the receiving sensitivity. Therefore, there is no need to change the settings for the optical receiving unit 102.

[0048] After that, communication is performed between the first optical wireless communication device 1-1 and the second optical wireless communication device 1-2.

[0049] In the above, the temperature dependence of the AWG is 0.08 nm / K. However, the temperature dependence of the AWG is not limited to this, and can vary significantly depending on the design and material selection of the AWG. In contrast, in the optical wireless communication device 1 according to the first embodiment, even if the temperature dependency of the AWG changes, it can be dealt with simply by adjusting the temperature setting value, and the basic operation described above can be applied.

[0050] Furthermore, not only a DML or EML, whose oscillation wavelength changes depending on temperature, but also a wavelength-tunable laser may be used for the optical transmitter 101. In this case, a method normally used for wavelength manipulation of a wavelength-tunable laser, such as heating with a heater or application of an electric field, is used.

[0051] Next, effects achieved by the optical wireless communication device 1 according to the first embodiment will be described. First, in the optical wireless communication device 1 according to the first embodiment, many wavelengths can be allocated, which makes it possible to improve communication capacity.

[0052] Moreover, the optical wireless communication device 1 according to the first embodiment can be changed between two types of settings with the same configuration. In the above example, the optical wireless communication device 1 with the same configuration can be used for the first satellite 10-1 and the second satellite 10-2. Therefore, the optical wireless communication device 1 according to the first embodiment can not only be made smaller in size, but also reduce the variety of devices, and can be manufactured more cheaply than before.

[0053] In the optical wireless communication device 1 according to the first embodiment, the wavelengths of the optical transmitting units 101 and the optical receiving units 102 are alternately arranged, which facilitates changing of the wavelength. As a result, the optical wireless communication device 1 according to the first embodiment can have a simple configuration and can reduce power consumption and heat generation. For example, in wavelength multiplexing, if transmit signals with multiple wavelengths are placed on the short wave side of the ITU-T grid and receive signals with multiple wavelengths on the long wave side, switching between transmit and receive settings requires a large change in wavelength, which requires a large amount of power and a complex mechanism.

[0054] As described above, according to the first embodiment, the optical wireless communication system is an optical wireless communication system including a paired optical wireless communication device 1, the optical wireless communication device 1 including a plurality of optical transmitting units 101 that transmit optical signals of a target wavelength, an optical multiplexing / demultiplexing unit 103 that multiplexes the optical signals transmitted by the optical transmitting units 101 and transmits the multiplexed optical signals to the counterpart optical wireless communication device 1, and demultiplexes the optical signals from the counterpart optical wireless communication device 1 into optical signals of a plurality of wavelengths, and a plurality of optical receiving units 102 that receive the optical signals of the target wavelengths from the optical signals demultiplexed by the optical multiplexing / demultiplexing unit 103, the wavelengths that are the target of the optical transmitting units 101 and the optical receiving units 102 respectively are wavelengths that are assigned alternately in length order, and between the paired optical wireless communication devices 1, the wavelengths that are the target of the optical transmitting units 101 and the optical receiving units 102 respectively are shifted by one. Moreover, according to the first embodiment, the optical multiplexing / demultiplexing unit 103 is an AWG. Furthermore, according to the first embodiment, the optical wireless communication system includes a temperature control section that controls the temperature of the optical multiplexing / demultiplexing section 103 . As a result, the optical wireless communication system according to the first embodiment can implement a larger number of wavelengths than conventional systems, and can easily switch between wavelengths.

[0055] Furthermore, according to this embodiment 1, the optical wireless communication device 1 includes a plurality of optical transmitting units 101 that transmit optical signals of target wavelengths, an optical multiplexing / demultiplexing unit 103 that multiplexes the optical signals transmitted by the optical transmitting units 101 and transmits the multiplexed optical signals to the counterpart optical wireless communication device 1, and demultiplexes the optical signal from the counterpart optical wireless communication device 1 into optical signals of multiple wavelengths, and a plurality of optical receiving units 102 that receive the optical signals of the target wavelengths from the optical signals demultiplexed by the optical multiplexing / demultiplexing unit 103, and the wavelengths that are the target of each of the optical transmitting units 101 and the optical receiving units 102 are wavelengths that are assigned alternately in length order. As a result, the optical wireless communication device 1 according to the first embodiment can implement a larger number of wavelengths than conventional devices, and can easily switch between wavelengths.

[0056] Embodiment 2 FIG. 6 is a diagram showing an example of the configuration of a first optical wireless communication device 1-1 according to the second embodiment. In the first optical wireless communication device 1-1 according to the second embodiment shown in Fig. 6, a first optical amplifier section (SOA) 104-1 is added to the first optical wireless communication device 1-1 according to the first embodiment shown in Fig. 3. The other configuration example of the first optical wireless communication device 1-1 according to the second embodiment shown in Fig. 6 is similar to the configuration example of the first optical wireless communication device 1-1 according to the first embodiment shown in Fig. 3, and the same reference numerals are used and only different parts will be described. Although not shown, the second optical wireless communication device 1-2 according to the second embodiment has the same configuration as the first optical wireless communication device 1-1 according to the second embodiment.

[0057] The first optical transmitting unit 101-1 in the second embodiment is a DML or an EML.

[0058] The first optical amplifying unit 104-1 is provided for each first optical transmitting unit 101-1 between the first optical transmitting unit 101-1 and the first optical multiplexing / demultiplexing unit 103-1. The first optical amplifying unit 104-1 amplifies the optical signal transmitted by the corresponding first optical transmitting unit 101-1. In FIG. 6, a SOA (Semiconductor optical amplifier) ​​is used as the first optical amplifying section 104-1.

[0059] The first optical transmitting unit 101-1 and the first optical amplifying unit 104-1 may be configured by being monolithically integrated on a single semiconductor chip, or the first optical amplifying unit 104-1 in a separate package may be configured by being spatially optically connected to the first optical transmitting unit 101-1 or by using optical fiber.

[0060] Moreover, the first optical multiplexing / demultiplexing section 103-1 in the second embodiment multiplexes the optical signals amplified by the first optical amplifying section 104-1, and transmits the multiplexed optical signals to the second optical wireless communication device 1-2.

[0061] Next, an operation example of the optical wireless communication device 1 according to the second embodiment will be described. In the optical wireless communication device 1, when coupling to an AWG or a single mode fiber is essential, a DML or EML operating in a single mode is required as the optical transmitter 101. Under such constraints, the optical transmitter 101 does not have a very high output, for example, 100 mW or less, and it is not possible to obtain an output of several hundred mW to several W required for long-distance free-space optical communication. In contrast, the optical wireless communication device 1 according to the second embodiment includes an optical amplifier 104 on the output side of the optical transmitter 101, which is a DML or EML, to amplify the light input to each port of the optical multiplexer / demultiplexer 103. As a result, the optical wireless communication device 1 according to the second embodiment can obtain an output of several hundreds of mW to several W required for long-distance free-space optical communication.

[0062] Next, the effects of the optical wireless communication device 1 according to the second embodiment will be described. In the optical wireless communication device 1 according to the second embodiment, it is possible to strengthen the light input to each port of the optical multiplexing / demultiplexing unit 103. Therefore, in the optical wireless communication device 1 according to the second embodiment, an optical amplifier, for example, a fiber amplifier such as an EDFA, is not required after the optical multiplexing / demultiplexing unit 103, or a low-gain optical amplifier can be applied after the optical multiplexing / demultiplexing unit 103. As a result, in the optical wireless communication device 1 according to the second embodiment, it is possible to simplify the device and reduce the size of the device.

[0063] As described above, according to the second embodiment, the optical transmitting unit 101 is a DML or EML, the optical wireless communication device 1 includes an optical amplifying unit 104 that amplifies the optical signal transmitted by the optical transmitting unit 101, and the optical multiplexing / demultiplexing unit 103 multiplexes the optical signal amplified by the optical amplifying unit 104 and transmits it to the destination optical wireless communication device 1. As a result, the optical wireless communication system according to the second embodiment can enhance the intensity of the output light to the optical multiplexing / demultiplexing section 103 in addition to the effect of the first embodiment.

[0064] Embodiment 3 FIG. 7 is a diagram showing an example of the configuration of a first optical wireless communication device 1-1 according to the third embodiment. In the first optical wireless communication device 1-1 according to the third embodiment shown in Fig. 7, a first wavelength filter 105-1 is added to the first optical wireless communication device 1-1 according to the first embodiment shown in Fig. 3. The other configuration example of the first optical wireless communication device 1-1 according to the third embodiment shown in Fig. 7 is similar to the configuration example of the first optical wireless communication device 1-1 according to the first embodiment shown in Fig. 3, so the same reference numerals are used and only different parts will be described. Although not shown, the second optical wireless communication device 1-2 according to the third embodiment has the same configuration as the first optical wireless communication device 1-1 according to the third embodiment.

[0065] The first wavelength filter 105-1 is provided for each first optical receiving unit 102-1 between the first optical receiving unit 102-1 and the first optical multiplexing / demultiplexing unit 103-1. The first wavelength filter 105-1 transmits optical signals of two wavelengths that the corresponding optical receiving unit 102 can target, among the optical signals demultiplexed by the first optical multiplexing / demultiplexing unit 103-1, and blocks optical signals of other wavelengths. For example, in Fig. 7, a different wavelength is input to the first optical receiving unit 102-1 connected to the second port (port2) when it functions as the first optical wireless communication device 1-1 and when it functions as the second optical wireless communication device 1-2. Specifically, an optical signal having either a wavelength of λ1 or λ2 is input. Therefore, in this case, the first wavelength filter 105-1 has a band that covers these two wavelengths as shown by the dotted lines in Fig. 8.

[0066] The first wavelength filter 105-1 may be configured by being monolithically integrated on the chip on which the first optical multiplexing / demultiplexing section 103-1 is fabricated, or may be configured by being externally connected via an optical fiber or the like.

[0067] Next, an operation example of the optical wireless communication device 1 according to the third embodiment will be described. It is known that AWGs generally generate crosstalk between ports of about 40 dB. When receiving signals with more than 10 wavelengths as in the first embodiment, the crosstalk of each wavelength is accumulated, and the total amount of crosstalk may increase by 10 dB or more. In contrast, the optical wireless communication device 1 according to the third embodiment is provided with a bandpass filter that allows specific wavelengths to pass, thereby cutting out irrelevant wavelengths.

[0068] Next, effects of the optical wireless communication device 1 according to the third embodiment will be described. In the optical wireless communication device 1 according to the third embodiment, the receiving performance can be improved by filtering the crosstalk generated in the AWG. Also, by providing a filter that covers two wavelengths as shown in Fig. 8, the switchable operation as shown in the first embodiment can be realized.

[0069] In the above, the configuration in which the wavelength filter 105 is added to the optical wireless communication device 1 according to the embodiment 1 has been shown. However, the present invention is not limited to this, and the configuration in which the wavelength filter 105 is added to the optical wireless communication device 1 according to the embodiment 2 may also be used, and the same effects as those described above can be obtained.

[0070] As described above, according to the third embodiment, the optical wireless communication device 1 includes a wavelength filter 105 provided for each optical receiving unit 102, which transmits optical signals of two wavelengths that can be targeted by the corresponding optical receiving unit 102 out of the optical signals demultiplexed by the optical multiplexing / demultiplexing unit 103, and the optical receiving unit 102 receives the optical signals that have transmitted through the wavelength filter 105. As a result, the optical wireless communication device 1 according to the third embodiment can block unnecessary wavelengths in addition to the effects achieved in the first and second embodiments.

[0071] Embodiment 4 Fig. 9 is a diagram showing a configuration example of a first optical wireless communication device 1-1 according to embodiment 4. In the first optical wireless communication device 1-1 according to embodiment 4 shown in Fig. 9, a cyclic AWG is used as a first optical multiplexing / demultiplexing section 103-1, in contrast to the first optical wireless communication device 1-1 according to embodiment 1 shown in Fig. 3. The other configuration example of the first optical wireless communication device 1-1 according to embodiment 4 shown in Fig. 9 is similar to the configuration example of the first optical wireless communication device 1-1 according to embodiment 1 shown in Fig. 3, and the same reference numerals are used and only different parts will be described. Similarly, Fig. 10 is a diagram showing a configuration example of a second optical wireless communication device 1-2 according to embodiment 4. In the second optical wireless communication device 1-2 according to embodiment 4 shown in Fig. 10, a cyclic AWG is used as a second optical multiplexing / demultiplexing section 103-2, in contrast to the second optical wireless communication device 1-2 according to embodiment 1 shown in Fig. 4. The other configuration example of the second optical wireless communication device 1-2 according to embodiment 4 shown in Fig. 10 is similar to the configuration example of the second optical wireless communication device 1-2 according to embodiment 1 shown in Fig. 4, and the same reference numerals are used and only different parts will be described.

[0072] The first optical multiplexing / demultiplexing unit 103-1 is a cyclic AWG, which has periodic wavelength characteristics.

[0073] The second optical multiplexing / demultiplexing unit 103-2 is a cyclic AWG, which has periodic wavelength characteristics.

[0074] That is, the cyclic AWG has a temperature dependency of, for example, about 0.08 nm / K, and exhibits a behavior in which the port of the corresponding wavelength shifts to the adjacent one when the temperature is changed, similar to the AWG shown in the first embodiment. On the other hand, in the cyclic AWG, as shown in Figs. 9 and 10, the two wavelengths that the final port (port 20) can target are λ 19 , λ0, that is, the final wavelength and the first wavelength among the wavelengths targeted by the optical wireless communication system according to the fourth embodiment.

[0075] In this case, among the wavelengths targeted by the optical wireless communication system shown in FIG. 2, λ 20 The wavelengths targeted by the optical wireless communication system according to the fourth embodiment are λ0 to λ 19 It becomes.

[0076] Furthermore, when the first optical multiplexing / demultiplexing unit 103-1 and the second optical multiplexing / demultiplexing unit 103-2 are cyclic AWGs, the wavelengths are shifted as described above, so that no port in the first optical multiplexing / demultiplexing unit 103-1 or the second optical multiplexing / demultiplexing unit 103-2 is unable to be used for communication.

[0077] Next, an operation example of the optical wireless communication device 1 according to the fourth embodiment will be shown. As shown in FIGS. 9 and 10, for example, in the first optical wireless communication device 1-1, 19 When this is used, an optical signal of λ0 is input to the twentieth port (port20) of the second optical wireless communication device 1-2 in which the wavelength is shifted.

[0078] Next, effects of the optical wireless communication device 1 according to the fourth embodiment will be described. In the first embodiment, there is one port that cannot be used for communication in each optical wireless communication device 1. In contrast, in the optical wireless communication device 1 according to the fourth embodiment, by imparting cyclicity to the optical multiplexing / demultiplexing unit 103, it is possible to eliminate ports that cannot be used for communication, thereby improving communication capacity.

[0079] In the above, the optical wireless communication device 1 according to the first embodiment has a configuration in which a cyclic AWG is used as the optical multiplexing / demultiplexing unit 103. However, the present invention is not limited to this, and the optical wireless communication device 1 according to the second embodiment or the optical wireless communication device 1 according to the third embodiment may have a configuration in which a cyclic AWG is used as the optical multiplexing / demultiplexing unit 103, and the same effects as those described above can be obtained.

[0080] As described above, according to the fourth embodiment, the optical multiplexing / demultiplexing section 103 is a cyclic AWG. As a result, the optical wireless communication system according to the fourth embodiment can improve communication capacity in addition to the effects of the first to third embodiments.

[0081] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted. [Industrial Applicability]

[0082] The optical wireless communication system according to the present disclosure can implement a larger number of wavelengths than conventional systems, can easily switch wavelengths, and is suitable for use in optical wireless communication systems equipped with optical wireless communication devices that transmit and receive optical signals. [Explanation of symbols]

[0083] 1 Optical wireless communication device, 1-1 First optical wireless communication device, 1-2 Second optical wireless communication device, 10 Satellite, 10-1 First satellite, 10-2 Second satellite, 101 Optical transmitting unit, 101-1 First optical transmitting unit, 101-2 Second optical transmitting unit, 102 Optical receiving unit, 102-1 First optical receiving unit, 102-2 Second optical receiving unit, 103 Optical multiplexing / demultiplexing unit, 103-1 First optical multiplexing / demultiplexing unit, 103-2 Second optical multiplexing / demultiplexing unit, 104 Optical amplification unit, 104-1 First optical amplification unit, 105 Wavelength filter, 105-1 First wavelength filter.

Claims

1. An optical wireless communication system having a pair of optical wireless communication devices, The optical wireless communication device includes: A plurality of optical transmitters for transmitting optical signals of target wavelengths; an optical multiplexing / demultiplexing unit that multiplexes the optical signals transmitted by the optical transmitting unit and transmits the multiplexed optical signals to the optical wireless communication device as a destination, and demultiplexes the optical signals from the optical wireless communication device as a destination into optical signals of a plurality of wavelengths; a plurality of optical receiving units for receiving optical signals of target wavelengths among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; a wavelength filter provided for each of the optical receiving units, the wavelength filter transmitting optical signals of two wavelengths that can be targeted by the corresponding optical receiving unit among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; the wavelengths targeted by the optical transmitting unit and the optical receiving unit are alternately assigned in order of length; between the pair of optical wireless communication devices, wavelengths targeted by the optical transmitting unit and the optical receiving unit are shifted by one, the optical multiplexing / demultiplexing unit is an AWG, and the number of ports is one more than the total number of wavelengths targeted by the optical transmitting unit and the optical receiving unit, respectively; The optical receiving unit receives an optical signal transmitted through the wavelength filter.

1. An optical wireless communication system comprising:

2. An optical wireless communication system having a pair of optical wireless communication devices, The optical wireless communication device includes: A plurality of optical transmitters for transmitting optical signals of target wavelengths; an optical multiplexing / demultiplexing unit that multiplexes the optical signals transmitted by the optical transmitting unit and transmits the multiplexed optical signals to the optical wireless communication device as a destination, and demultiplexes the optical signals from the optical wireless communication device as a destination into optical signals of a plurality of wavelengths; a plurality of optical receiving units for receiving optical signals of target wavelengths among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; a wavelength filter provided for each of the optical receiving units, the wavelength filter transmitting optical signals of two wavelengths that can be targeted by the corresponding optical receiving unit among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; the wavelengths targeted by the optical transmitting unit and the optical receiving unit are alternately assigned in order of length; between the pair of optical wireless communication devices, wavelengths targeted by the optical transmitting unit and the optical receiving unit are shifted by one, the optical multiplexing / demultiplexing unit is a cyclic AWG, and the number of ports is the same as the total number of wavelengths targeted by the optical transmitting unit and the optical receiving unit, respectively; The optical receiving unit receives an optical signal transmitted through the wavelength filter.

1. An optical wireless communication system comprising:

3. The optical wireless communication device includes: A temperature control unit is provided to control the temperature of the optical multiplexing / demultiplexing unit.

2. The optical wireless communication system according to claim 1.

4. The optical wireless communication device includes: A temperature control unit is provided to control the temperature of the optical multiplexing / demultiplexing unit.

3. The optical wireless communication system according to claim 2.

5. the optical transmitter is a DML or an EML, The optical wireless communication device includes: an optical amplifier for amplifying the optical signal transmitted by the optical transmitter; The optical multiplexing / demultiplexing unit multiplexes the optical signals amplified by the optical amplifier unit and transmits the multiplexed optical signals to the optical wireless communication device as a destination.

5. The optical wireless communication system according to claim 1, wherein the optical communication device is a semiconductor device.

6. A plurality of optical transmitters for transmitting optical signals of target wavelengths; an optical multiplexing / demultiplexing unit that multiplexes the optical signals transmitted by the optical transmitting unit and transmits the multiplexed optical signals to a destination optical wireless communication device, and demultiplexes the optical signals from the destination optical wireless communication device into optical signals of a plurality of wavelengths; a plurality of optical receiving units for receiving optical signals of target wavelengths among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; a wavelength filter provided for each of the optical receiving units, the wavelength filter transmitting optical signals of two wavelengths that can be targeted by the corresponding optical receiving unit among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; the wavelengths targeted by the optical transmitting unit and the optical receiving unit are alternately assigned in order of length; With respect to a pair of optical wireless communication devices, the wavelengths targeted by the optical transmitting unit and the optical receiving unit are shifted by one from each other, the optical multiplexing / demultiplexing unit is an AWG, and the number of ports is one more than the total number of wavelengths targeted by the optical transmitting unit and the optical receiving unit, respectively; The optical receiving unit receives an optical signal transmitted through the wavelength filter.

1. An optical wireless communication device comprising:

7. A plurality of optical transmitters for transmitting optical signals of target wavelengths; an optical multiplexing / demultiplexing unit that multiplexes the optical signals transmitted by the optical transmitting unit and transmits the multiplexed optical signals to a destination optical wireless communication device, and demultiplexes the optical signals from the destination optical wireless communication device into optical signals of a plurality of wavelengths; a plurality of optical receiving units for receiving optical signals of target wavelengths among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; a wavelength filter provided for each of the optical receiving units, the wavelength filter transmitting optical signals of two wavelengths that can be targeted by the corresponding optical receiving unit among the optical signals demultiplexed by the optical multiplexing / demultiplexing unit; the wavelengths targeted by the optical transmitting unit and the optical receiving unit are alternately assigned in order of length; With respect to a pair of optical wireless communication devices, the wavelengths targeted by the optical transmitting unit and the optical receiving unit are shifted by one from each other, the optical multiplexing / demultiplexing unit is a cyclic AWG, and the number of ports is the same as the total number of wavelengths targeted by the optical transmitting unit and the optical receiving unit, respectively; The optical receiving unit receives an optical signal transmitted through the wavelength filter.

1. An optical wireless communication device comprising:

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