Terahertz communication system

Abstract

One non-limiting and exemplary embodiment provides a terahertz communication system in which terahertz optical signals having respective frequencies are assigned to respective terahertz radio signal transmitters more flexibly when a plurality of frequency bands are stored by multiplexing.SOLUTION: In allocating the terahertz optical signals having the respective frequencies to the respective terahertz radio signal transmission units 2, the terahertz optical signal switching unit 3 switches a combination of allocation of the terahertz optical signals among a plurality of combinations.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a terahertz communication system in the range of about 0.1 to 10 THz. [Background technology]

[0002] Terahertz communication systems of around 0.1 to 10 THz generate terahertz optical signals and transmit terahertz wireless signals (see Patent Document 1 and Non-Patent Document 1, etc.). First, optical signals having different frequencies are optically coupled to generate a terahertz optical signal. Next, the terahertz optical signal is photoelectrically converted and the terahertz wireless signal is transmitted. Here, the envelope of the beat of the terahertz optical signal is in the terahertz band, but the area inside the envelope is in the optical communication band. Therefore, optical couplers and photoelectric converters that are applicable to optical communications can also be applied to terahertz communications. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-062619 [Non-patent literature]

[0004] [Non-Patent Document 1] Tadao Nagatsuma, "Special Feature Commentary - Terahertz Technology Opens New Doors to Precision Engineering," "Ultra-High-Speed ​​Wireless Communications Opened Up by Terahertz Waves - Aiming to Realize Wireless Communications at the Same Speed ​​as Optical Fiber Communications," Journal of the Japan Society for Precision Engineering, Vol. 82, No. 3, pp. 221-224, 2016. Summary of the Invention [Problem to be solved by the invention]

[0005] The configuration of a first terahertz communication system according to the prior art is shown in Fig. 1 (see Patent Document 1, etc.). The terahertz communication system S basically comprises one terahertz optical signal generation unit 1 and one terahertz radio signal transmission unit 2. The terahertz optical signal generation unit 1 comprises a signal light source 11, a local light source 12, an optical modulator 13, and an optical coupler 14. The terahertz radio signal transmission unit 2 comprises an opto-electrical converter 21, an amplifier 22, and an antenna 23.

[0006] The signal light source 11 and the local light source 12 output optical signals having different frequencies. The optical modulator 13 optically modulates the optical signal output by the signal light source 11 with a data signal. The optical coupler 14 optically couples the optical signal output by the optical modulator 13 with the optical signal output by the local light source 12. The photoelectric converter 21 photoelectrically converts the terahertz optical signal output by the optical coupler 14. The amplifier 22 amplifies the terahertz electrical signal output by the photoelectric converter 21. The antenna 23 transmits the terahertz electrical signal output by the amplifier 22 as a terahertz wireless signal.

[0007] The configuration of a second terahertz communication system according to the prior art is shown in Fig. 2 (see Non-Patent Document 1, etc.). The terahertz communication system S basically comprises one terahertz optical signal generation unit 1 and one terahertz radio signal transmission unit 2. The terahertz optical signal generation unit 1 comprises a first light source 15, a second light source 16, an optical coupler 17, and an optical modulator 18. The terahertz radio signal transmission unit 2 comprises an opto-electrical converter 21, an amplifier 22, and an antenna 23.

[0008] The first light source 15 and the second light source 16 output optical signals having different frequencies. The optical coupler 17 optically couples the optical signal output by the first light source 15 and the optical signal output by the second light source 16. The optical modulator 18 optically modulates the terahertz optical signal output by the optical coupler 17 with a data signal. The photoelectric converter 21 photoelectrically converts the terahertz optical signal output by the optical modulator 18. The amplifier 22 amplifies the terahertz electrical signal output by the photoelectric converter 21. The antenna 23 transmits the terahertz electrical signal output by the amplifier 22 as a terahertz wireless signal.

[0009] Here, there is a demand for storing multiple frequency bands by multiplexing the first and second terahertz communication systems S of the prior art. To address this, it is conceivable to simply parallelize N terahertz communication systems S. That is, it is conceivable to simply parallelize N terahertz optical signal generation units 1 and N terahertz radio signal transmission units 2. However, simply parallelizing N terahertz communication systems S alone reduces the degree of freedom in allocating terahertz optical signals having N frequencies to N terahertz radio signal transmission units 2.

[0010] Therefore, in order to solve the above-mentioned problems, the present disclosure aims to increase the degree of freedom in assigning terahertz optical signals having respective frequencies to respective terahertz wireless signal transmitters when storing multiple frequency bands by multiplexing a terahertz communication system. [Means for solving the problem]

[0011] In order to solve the above problem, when allocating terahertz optical signals having respective frequencies to respective terahertz wireless signal transmitters, a multicast switch (MCS) or the like is used to switch the allocation combination of terahertz optical signals among a plurality of combinations.

[0012] Specifically, the present disclosure provides a terahertz communication system comprising: a terahertz optical signal generation unit that, when optically coupling optical signals having different frequencies to generate terahertz optical signals, sets a plurality of combinations of different frequencies of the optical signals and generates the terahertz optical signals having a plurality of frequencies; a plurality of terahertz radio signal transmission units that photoelectrically convert the terahertz optical signals having each frequency and transmit terahertz radio signals having each frequency; and a terahertz optical signal switching unit that, when allocating the terahertz optical signals having each frequency to each of the terahertz radio signal transmission units, is capable of switching the combination of allocation of the terahertz optical signals among a plurality of combinations.

[0013] According to this configuration, by multiplexing the terahertz communication system, when storing multiple frequency bands, the terahertz optical signal switching unit can increase the degree of freedom in assigning terahertz optical signals having each frequency to each terahertz wireless signal transmitting unit.

[0014] The present disclosure also provides a terahertz communication system, characterized in that M (M is an integer equal to or greater than 2) terahertz optical signal generation units generate terahertz optical signals having each of M frequencies, and the terahertz optical signal switching unit has inputs from the M terahertz optical signal generation units and outputs to N (N is an integer equal to or greater than M) terahertz wireless signal transmission units.

[0015] This configuration increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz radio signal transmission units. When N>M, the same terahertz optical signal can be allocated to multiple terahertz radio signal transmission units.

[0016] The present disclosure also provides a terahertz communication system, wherein the terahertz optical signal generation unit includes M first light sources that output optical signals having each of M frequencies (M is an integer equal to or greater than 2), and one second light source that outputs an optical signal having a frequency different from the M frequencies, and the terahertz optical signal switching unit includes inputs from the M first light sources and outputs N (N is an integer equal to or greater than M) optical signals to an optical coupler.

[0017] This configuration increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz radio signal transmission units. Furthermore, one second light source is shared by M first light sources, and although the M frequencies of the terahertz optical signals are limited, the number of second light sources can be reduced. Furthermore, when N>M, the same terahertz optical signal can be allocated to multiple terahertz radio signal transmission units.

[0018] The present disclosure also provides a terahertz communication system, wherein the terahertz optical signal generation unit comprises M first light sources that output the optical signals having each of M frequencies (M is an integer equal to or greater than 2), and one second light source that outputs the optical signal having a frequency different from the M frequencies; and the terahertz optical signal switching unit (1) is disposed inside the terahertz optical signal generation unit and comprises M inputs from the first light sources and M outputs of the optical signals to an optical coupler, and (2) is disposed between the terahertz optical signal generation unit and N terahertz wireless signal transmission units (N is an integer greater than M) and comprises M inputs of the optical signals from the optical coupler and N outputs to the terahertz wireless signal transmission units.

[0019] This configuration increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz radio signal transmission units. Furthermore, one second light source is shared by M first light sources, limiting the M frequencies of the terahertz optical signals, but reducing the number of second light sources. Furthermore, the same terahertz optical signal can be allocated to multiple terahertz radio signal transmission units, reducing the number of optical couplers.

[0020] The present disclosure also provides a terahertz communication system, wherein the terahertz optical signal generation unit includes M first light sources that output the optical signals having each of M frequencies (M is an integer equal to or greater than 2), and M second light sources that output the optical signals having each of M frequencies different from the M frequencies, and the terahertz optical signal switching unit includes M inputs from the first light sources and the second light sources, and N (N is an integer equal to or greater than M) outputs of the optical signals to two inputs of an optical coupler.

[0021] This configuration increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz wireless signal transmission units. Furthermore, by combining M first light sources and M second light sources (provided that the optical signals generated by the terahertz optical signal generation unit are in the terahertz band and are optically modulated), the M frequencies of the terahertz optical signals can be diversified without any restrictions. Furthermore, when N>M, the same terahertz optical signal can be allocated to multiple terahertz wireless signal transmission units.

[0022] The present disclosure also provides a terahertz communication system, wherein the terahertz optical signal generation unit comprises M first light sources that output the optical signals having each of M frequencies (M is an integer greater than or equal to 2), and M second light sources that output the optical signals having each of M frequencies different from the M frequencies; and the terahertz optical signal switching unit (1) is disposed inside the terahertz optical signal generation unit, and comprises M inputs from the first light sources and the second light sources, and M outputs of the optical signals to two inputs of an optical coupler, and (2) is disposed between the terahertz optical signal generation unit and N terahertz wireless signal transmission units (N is an integer greater than M), and comprises M inputs of the optical signals from the optical coupler and N outputs to the terahertz wireless signal transmission units.

[0023] This configuration increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz wireless signal transmission units. Furthermore, by combining M first light sources and M second light sources (provided that the optical signals generated by the terahertz optical signal generation unit are in the terahertz band and are optically modulated), the M frequencies of the terahertz optical signals can be diversified without any restrictions. Furthermore, the same terahertz optical signal can be allocated to multiple terahertz wireless signal transmission units, reducing the number of optical couplers.

[0024] The present disclosure also provides a terahertz communication system, further comprising a wavelength multiplexing unit arranged between the terahertz optical signal switching unit and the plurality of terahertz radio signal transmitting units, which wavelength-multiplexes the terahertz optical signals having a plurality of frequencies.

[0025] According to this configuration, terahertz optical signals wavelength-multiplexed in a plurality of frequency bands can be assigned to each terahertz radio signal transmitter by an arrayed waveguide (AWG) or the like.

[0026] The present disclosure also provides a terahertz communication system, characterized in that the terahertz optical signal switching unit is capable of switching a combination of allocations of the terahertz optical signals among a plurality of combinations and performing time division multiplexing.

[0027] According to this configuration, terahertz optical signals that are switched over time between a plurality of frequencies by time division multiplexing can be assigned to each terahertz wireless signal transmitter.

[0028] The present disclosure also provides a terahertz communication system, wherein the terahertz optical signal generation unit (1) optically modulates the optical signal having one frequency with a data signal and optically couples the optically modulated optical signal having one frequency with an optical signal having another frequency that is not optically modulated, or (2) optically couples the optical signal having one frequency with an optical signal having another frequency and optically modulates the optically coupled optical signal with a data signal.

[0029] According to this configuration, the first or second conventional technique can be expanded, and terahertz optical signals having respective frequencies can be assigned to the respective terahertz wireless signal transmitting units.

[0030] The above-disclosed inventions can be combined as much as possible. [Effects of the Invention]

[0031] In this way, by multiplexing a terahertz communication system, the present disclosure can increase the degree of freedom in assigning terahertz optical signals having each frequency to each terahertz wireless signal transmitter when storing multiple frequency bands. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a diagram showing the configuration of a first terahertz communication system according to the prior art. [Figure 2] FIG. 10 is a diagram showing the configuration of a second terahertz communication system according to the prior art. [Figure 3] FIG. 1 is a diagram illustrating a configuration of a terahertz communication system No. 1-1 of the present disclosure. [Figure 4] FIG. 10 is a diagram illustrating a configuration of a terahertz communication system according to a first-second embodiment of the present disclosure. [Figure 5] FIG. 10 is a diagram illustrating a configuration of a first-third terahertz communication system according to the present disclosure. [Figure 6] FIG. 10 is a diagram illustrating a configuration of a first to fourth terahertz communication system according to the present disclosure. [Figure 7] FIG. 10 is a diagram illustrating the configuration of a terahertz communication system according to a first to fifth aspects of the present disclosure. [Figure 8] FIG. 10 is a diagram illustrating the configuration of a terahertz communication system according to a first to sixth aspects of the present disclosure. [Figure 9] FIG. 10 is a diagram illustrating a configuration of a terahertz communication system according to a first to seventh aspect of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating the configuration of a terahertz communication system according to a first to eighth aspect of the present disclosure. [Figure 11] FIG. 2 is a diagram illustrating a configuration of a terahertz communication system according to a second embodiment of the present disclosure. [Figure 12] FIG. 2 is a diagram illustrating a configuration of a terahertz communication system according to a second embodiment of the present disclosure. [Figure 13] FIG. 10 is a diagram illustrating a configuration of a terahertz communication system according to a second third embodiment of the present disclosure. [Figure 14] FIG. 10 is a diagram illustrating a configuration of a terahertz communication system according to a second to fourth aspect of the present disclosure. [Figure 15]FIG. 10 is a diagram illustrating the configuration of a terahertz communication system according to a second to fifth aspect of the present disclosure. [Figure 16] FIG. 10 is a diagram illustrating a configuration of a terahertz communication system according to a second sixth embodiment of the present disclosure. [Figure 17] FIG. 20 is a diagram illustrating the configuration of a terahertz communication system according to a second to seventh aspect of the present disclosure. [Figure 18] FIG. 10 is a diagram illustrating the configuration of a terahertz communication system according to a second eighth aspect of the present disclosure. [Figure 19] FIG. 1 is a diagram illustrating an example of a terahertz communication system according to a first embodiment of the present disclosure. [Figure 20] FIG. 10 is a diagram illustrating a first-second embodiment of a terahertz communication system according to the present disclosure. [Figure 21] FIG. 10 is a diagram illustrating a first-second embodiment of a terahertz communication system according to the present disclosure. [Figure 22] FIG. 10 is a diagram illustrating a first to third embodiment of a terahertz communication system according to the present disclosure. [Figure 23] 10A and 10B are diagrams illustrating examples of terahertz communication systems according to the first to fifth embodiments of the present disclosure. [Figure 24] 10A and 10B are diagrams illustrating examples of terahertz communication systems according to the first to sixth embodiments of the present disclosure. [Figure 25] FIG. 10 is a diagram illustrating an example of a terahertz communication system according to a first to eighth embodiment of the present disclosure. [Figure 26] FIG. 2 is a diagram illustrating an example of a terahertz communication system according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0033]

[0023] The following embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of implementation of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0034] (Configuration of the first terahertz communication system of the present disclosure) The first terahertz communication system of the present disclosure is an extension of the first terahertz communication system of the prior art. The first terahertz communication system of the present disclosure has different frequency characteristics of the terahertz optical signal and the terahertz radio signal compared to a second terahertz communication system of the present disclosure, which will be described later, but has the same degree of freedom in allocating the terahertz optical signal.

[0035] The configuration of a terahertz communication system according to claim 1-1 of the present disclosure is shown in Fig. 3. The terahertz communication system S includes N terahertz optical signal generation units 1 and N terahertz wireless signal transmission units 2. Each terahertz optical signal generation unit 1 includes one signal light source 11, one local light source 12, one optical modulator 13, and one optical coupler 14. Each terahertz wireless signal transmission unit 2 includes one opto-electrical converter 21, one amplifier 22, and one antenna 23.

[0036] In each terahertz optical signal generation unit 1, the signal light source 11 and the local light source 12 output optical signals having different frequencies. Here, the wavelength and frequency of the optical signal output by the signal light source 11 are expressed as (λ S1 , ···, λ SN ), (f S1 , , f SN ), and the wavelength and frequency of the optical signal output by the local light source 12 are (λ О1 , ···, λ ОN ), (f О1 , , f ОN ). The optical modulator 13 optically modulates the optical signal output by the signal light source 11 with the data signal. The optical coupler 14 optically couples the optical signal output by the optical modulator 13 with the optical signal output by the local light source 12. Then, the frequency of the terahertz optical signal output by the optical coupler 14 is expressed as (f1, . . . , f N )=(|f S1 -f О1 |, , |f SN -f ОN |).

[0037] In each terahertz radio signal transmitter 2, the photoelectric converter 21 photoelectrically converts the terahertz optical signal output by the optical coupler 14 of one terahertz optical signal generator 1 (selected by the terahertz optical signal switching unit 3 described later). The amplifier 22 amplifies the terahertz electrical signal output by the photoelectric converter 21. The antenna 23 transmits the terahertz electrical signal output by the amplifier 22 as a terahertz radio signal. Then, the frequency of the terahertz radio signal output by the antenna 23 is expressed as (f1, . . . , f N )=(|f S1 -f О1 |, , |f SN -f ОN |).

[0038] The terahertz communication system S includes a terahertz optical signal switching unit 3. Here, the terahertz optical signal switching unit 3 is a multicast switch (MCS) or the like, and includes inputs from N terahertz optical signal generation units 1 and outputs to N terahertz radio signal transmission units 2. In other words, when allocating terahertz optical signals having respective frequencies to the respective terahertz radio signal transmission units 2, the terahertz optical signal switching unit 3 is capable of switching the combination of allocation of terahertz optical signals among a plurality of combinations.

[0039] Therefore, by multiplexing the terahertz communication system S, when storing multiple frequency bands, the terahertz optical signal switching unit 3 can increase the degree of freedom in allocating terahertz optical signals having N types of frequencies to N terahertz radio signal transmission units 2.

[0040] The terahertz communication system S includes a wavelength multiplexing unit 4. The wavelength multiplexing unit 4 is disposed between the terahertz optical signal switching unit 3 and N terahertz radio signal transmission units 2, and wavelength-multiplexes terahertz optical signals having multiple frequencies. Here, the wavelength multiplexing unit 4 includes inputs from the terahertz optical signal switching unit 3 with N outputs, and outputs to the N terahertz radio signal transmission units 2.

[0041] Therefore, terahertz optical signals wavelength-multiplexed in multiple frequency bands using an arrayed waveguide (AWG) or the like can be assigned to N terahertz radio signal transmitters 2. There is no need to route multiple outputs from the terahertz optical signal switching unit 3 to each terahertz radio signal transmitter 2; it is sufficient to simply connect one output from the wavelength multiplexing unit 4.

[0042] The configuration of the terahertz communication system No. 1-2 of the present disclosure is shown in Fig. 4. The following mainly describes the differences from the terahertz communication system No. 1-1 of the present disclosure.

[0043] The terahertz communication system S includes M terahertz optical signal generation units 1. The terahertz optical signal switching unit 3 includes inputs from the M terahertz optical signal generation units 1 and outputs to N terahertz radio signal transmission units 2 (N is an integer greater than M).

[0044] This increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz radio signal transmission units 2. Furthermore, since N>M, the same terahertz optical signal can be allocated to multiple terahertz radio signal transmission units 2.

[0045] The configuration of a terahertz communication system according to a first third aspect of the present disclosure is shown in Fig. 5. The following mainly describes the differences from the terahertz communication system according to a first first aspect of the present disclosure.

[0046] The terahertz communication system S includes one terahertz optical signal generation unit 1, but does not include a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes N signal light sources 11, one local light source 12, N optical modulators 13, and N optical couplers 14, and includes a terahertz optical signal switching unit 19 instead of the terahertz optical signal switching unit 3.

[0047] N signal light sources 11 output optical signals having each of the N frequencies. One local light source 12 outputs an optical signal having a frequency different from the N frequencies, and divides the output into N signals for N optical couplers 14. Terahertz optical signal switching unit 19 has inputs from N optical modulators 13 and outputs to N optical couplers 14.

[0048] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having N kinds of frequencies to N terahertz wireless signal transmitters 2. In addition, one local light source 12 is shared by N signal light sources 11, and the N kinds of frequencies (|f Si -f О |, i=1 to N), the number of local light sources 12 can be reduced.

[0049] The configuration of a terahertz communication system according to a first-fourth aspect of the present disclosure is shown in Fig. 6. The following mainly describes the differences from the terahertz communication system according to a first-third aspect of the present disclosure.

[0050] The terahertz optical signal generation unit 1 includes M signal light sources 11 and M optical modulators 13. The terahertz optical signal switching unit 19 includes inputs from the M optical modulators 13 and outputs to N optical couplers 14 (N is an integer greater than M).

[0051] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz wireless signal transmitters 2. One local light source 12 is shared by M signal light sources 11, and the M frequencies (|f Si -f О |, i=1 to M), it is possible to reduce the number of local light sources 12. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2.

[0052] The configuration of a terahertz communication system according to a first to fifth aspect of the present disclosure is shown in Fig. 7. The following mainly describes the differences from the terahertz communication system according to a first to fourth aspect of the present disclosure.

[0053] The terahertz communication system S includes a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes M optical couplers 14 (the local light source 12 outputs in M ​​divisions). The terahertz optical signal switching unit 19 includes inputs from M optical modulators 13 and outputs to M optical couplers 14. The terahertz optical signal switching unit 3 includes inputs from M optical couplers 14 and outputs to N terahertz radio signal transmission units 2 (N is an integer greater than M).

[0054] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz wireless signal transmitters 2. One local light source 12 is shared by M signal light sources 11, and the M frequencies (|f Si -f О |, i=1 to M), it is possible to reduce the number of local light sources 12. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2, and the number of optical couplers 14 can be reduced.

[0055] The configuration of a terahertz communication system No. 1-6 of the present disclosure is shown in Fig. 8. The following mainly describes the differences from the terahertz communication system No. 1-1 of the present disclosure.

[0056] The terahertz communication system S includes one terahertz optical signal generation unit 1, but does not include a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes N signal light sources 11, N local light sources 12, N optical modulators 13, and N optical couplers 14, and includes a terahertz optical signal switching unit 19 instead of the terahertz optical signal switching unit 3.

[0057] N signal light sources 11 output optical signals having respective frequencies among N frequencies. N local light sources 12 output optical signals having respective frequencies among N frequencies different from the N frequencies. Terahertz optical signal switching unit 19 has inputs from N optical modulators 13 and local light sources 12, and outputs to two inputs of N optical couplers 14.

[0058] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having N kinds of frequencies to N terahertz wireless signal transmitters 2. Then, by combining N signal light sources 11 and N local light sources 12 (provided that the optical signal generated by the terahertz optical signal generator 1 is in the terahertz band and is optically modulated), the N kinds of frequencies (|f Si -f Оj |, i, j = 1 to N) can be diversified without any restrictions.

[0059] The configuration of a terahertz communication system according to a first to seventh aspect of the present disclosure is shown in Fig. 9. The following mainly describes the differences from the terahertz communication system according to a first to sixth aspect of the present disclosure.

[0060] The terahertz optical signal generation unit 1 includes M signal light sources 11, M local light sources 12, and M optical modulators 13. The terahertz optical signal switching unit 19 includes inputs from the M optical modulators 13 and the local light sources 12, and outputs to two inputs of N optical couplers 14 (N is an integer greater than M).

[0061] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz wireless signal transmitters 2. Then, by combining M signal light sources 11 and M local light sources 12 (provided that the optical signal generated by the terahertz optical signal generator 1 is in the terahertz band and is optically modulated), M frequencies (|f Si -f Оj|, i, j=1 to M) can be diversified without any restrictions. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2.

[0062] The configuration of a terahertz communication system according to a first eighth aspect of the present disclosure is shown in Fig. 10. The following mainly describes the differences from a terahertz communication system according to a first seventh aspect of the present disclosure.

[0063] The terahertz communication system S includes a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes M optical couplers 14. The terahertz optical signal switching unit 19 includes inputs from M optical modulators 13 and local light sources 12, and outputs to two inputs of the M optical couplers 14. The terahertz optical signal switching unit 3 includes inputs from the M optical couplers 14 and outputs to N terahertz radio signal transmission units 2 (N is an integer greater than M).

[0064] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz wireless signal transmitters 2. Then, by combining M signal light sources 11 and M local light sources 12 (provided that the optical signal generated by the terahertz optical signal generator 1 is in the terahertz band and is optically modulated), M frequencies (|f Si -f Оj |, i, j=1 to M) can be diversified without any restrictions. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2, and the number of optical couplers 14 can be reduced.

[0065] (Configuration of the second terahertz communication system of the present disclosure) The second terahertz communication system of the present disclosure is an extension of the second terahertz communication system of the prior art. In the second terahertz communication system of the present disclosure, the frequency characteristics of the terahertz optical signal and the terahertz radio signal are different from those of the first terahertz communication system of the present disclosure, but the degree of freedom in allocation of the terahertz optical signal is the same.

[0066] 11 shows the configuration of a terahertz communication system according to the second aspect of the present disclosure. The terahertz communication system S includes N terahertz optical signal generation units 1 and N terahertz radio signal transmission units 2. Each terahertz optical signal generation unit 1 includes one first light source 15, one second light source 16, one optical coupler 17, and one optical modulator 18. Each terahertz radio signal transmission unit 2 includes one photoelectric converter 21, one amplifier 22, and one antenna 23.

[0067] In each terahertz optical signal generation unit 1, the first light source 15 and the second light source 16 output optical signals having different frequencies. Here, the wavelength and frequency of the optical signal output by the first light source 15 are expressed as (λ 11 , ···, λ 1N ), (f 11 , , f 1N ), and the wavelength and frequency of the optical signal output by the second light source 16 are (λ 21 , ···, λ 2N ), (f 21 , , f 2N ). The optical coupler 17 optically couples the optical signal output by the first light source 15 and the optical signal output by the second light source 16. The optical modulator 18 optically modulates the terahertz optical signal output by the optical coupler 17 with a data signal. Then, the frequency of the terahertz optical signal output by the optical modulator 18 is expressed as (f1, . . . , f N )=(|f 11 -f 21 |, , |f 1N -f 2N |).

[0068] In each terahertz radio signal transmitter 2, the photoelectric converter 21 photoelectrically converts the terahertz optical signal output by the optical modulator 18 of one terahertz optical signal generator 1 (selected by the terahertz optical signal switching unit 3 described later). The amplifier 22 amplifies the terahertz electrical signal output by the photoelectric converter 21. The antenna 23 transmits the terahertz electrical signal output by the amplifier 22 as a terahertz radio signal. Then, the frequency of the terahertz radio signal output by the antenna 23 is expressed as (f1, . . . , f N )=(|f11 -f 21 |, , |f 1N -f 2N |).

[0069] The terahertz communication system S includes a terahertz optical signal switching unit 3. Here, the terahertz optical signal switching unit 3 is a multicast switch (MCS) or the like, and includes inputs from N terahertz optical signal generation units 1 and outputs to N terahertz radio signal transmission units 2. In other words, when allocating terahertz optical signals having respective frequencies to the respective terahertz radio signal transmission units 2, the terahertz optical signal switching unit 3 is capable of switching the combination of allocation of terahertz optical signals among a plurality of combinations.

[0070] Therefore, by multiplexing the terahertz communication system S, when storing multiple frequency bands, the terahertz optical signal switching unit 3 can increase the degree of freedom in allocating terahertz optical signals having N types of frequencies to N terahertz radio signal transmission units 2.

[0071] The terahertz communication system S includes a wavelength multiplexing unit 4. The wavelength multiplexing unit 4 is disposed between the terahertz optical signal switching unit 3 and N terahertz radio signal transmission units 2, and wavelength-multiplexes terahertz optical signals having multiple frequencies. Here, the wavelength multiplexing unit 4 includes inputs from the terahertz optical signal switching unit 3 with N outputs, and outputs to the N terahertz radio signal transmission units 2.

[0072] Therefore, terahertz optical signals wavelength-multiplexed in multiple frequency bands using an arrayed waveguide (AWG) or the like can be assigned to N terahertz radio signal transmitters 2. There is no need to route multiple outputs from the terahertz optical signal switching unit 3 to each terahertz radio signal transmitter 2; it is sufficient to simply connect one output from the wavelength multiplexing unit 4.

[0073] The configuration of a terahertz communication system according to 2-2 of the present disclosure is shown in Fig. 12. The following mainly describes the differences from the terahertz communication system according to 2-1 of the present disclosure.

[0074] The terahertz communication system S includes M terahertz optical signal generation units 1. The terahertz optical signal switching unit 3 includes inputs from the M terahertz optical signal generation units 1 and outputs to N terahertz radio signal transmission units 2 (N is an integer greater than M).

[0075] This increases the degree of freedom in allocating terahertz optical signals having M frequencies to N terahertz radio signal transmission units 2. Furthermore, since N>M, the same terahertz optical signal can be allocated to multiple terahertz radio signal transmission units 2.

[0076] The configuration of a terahertz communication system according to a second embodiment of the present disclosure is shown in Fig. 13. The following mainly describes the differences from the terahertz communication system according to a second embodiment of the present disclosure.

[0077] The terahertz communication system S includes one terahertz optical signal generation unit 1, but does not include a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes N first light sources 15, one second light source 16, N optical couplers 17, and N optical modulators 18, and includes a terahertz optical signal switching unit 20 instead of the terahertz optical signal switching unit 3.

[0078] The N first light sources 15 output optical signals having each of the N frequencies. One second light source 16 outputs an optical signal having a frequency different from the N frequencies, and divides the output into N optical couplers 17. The terahertz optical signal switching unit 20 has inputs from the N first light sources 15 and outputs to the N optical couplers 17.

[0079] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having N kinds of frequencies to N terahertz wireless signal transmission units 2. In addition, one second light source 16 is shared by N first light sources 15, and N kinds of frequencies (|f 1i −f2|, i=1 to N), the number of second light sources 16 can be reduced.

[0080] The configuration of a terahertz communication system according to a second-fourth aspect of the present disclosure is shown in Fig. 14. The following mainly describes the differences from the terahertz communication system according to a second-third aspect of the present disclosure.

[0081] The terahertz optical signal generation unit 1 includes M first light sources 15. The terahertz optical signal switching unit 20 includes inputs from the M first light sources 15 and outputs to N optical couplers 17 (N is an integer greater than M).

[0082] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M kinds of frequencies to N terahertz wireless signal transmission units 2. In addition, one second light source 16 is shared by M first light sources 15, and the M kinds of frequencies (|f 1i −f2|, i=1 to M), it is possible to reduce the number of second light sources 16. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2.

[0083] The configuration of a terahertz communication system according to a second embodiment of the present disclosure is shown in Fig. 15. The following mainly describes the differences from the terahertz communication system according to a second embodiment of the present disclosure.

[0084] The terahertz communication system S includes a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes M optical couplers 17 and M optical modulators 18 (the second light source 16 outputs in M ​​divisions). The terahertz optical signal switching unit 20 includes inputs from M first light sources 15 and outputs to M optical couplers 17. The terahertz optical signal switching unit 3 includes inputs from M optical modulators 18 and outputs to N terahertz radio signal transmission units 2 (N is an integer greater than M).

[0085] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M kinds of frequencies to N terahertz wireless signal transmission units 2. In addition, one second light source 16 is shared by M first light sources 15, and the M kinds of frequencies (|f 1i-f О |, i=1 to M), it is possible to reduce the number of second light sources 16. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2, and the number of optical couplers 17 and optical modulators 18 can be reduced.

[0086] The configuration of a terahertz communication system according to No. 2-6 of the present disclosure is shown in Fig. 16. The following mainly describes the differences from the terahertz communication system according to No. 2-1 of the present disclosure.

[0087] The terahertz communication system S includes one terahertz optical signal generation unit 1, but does not include a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes N first light sources 15, N second light sources 16, N optical couplers 17, and N optical modulators 18, and includes a terahertz optical signal switching unit 20 instead of the terahertz optical signal switching unit 3.

[0088] The N first light sources 15 output optical signals having respective frequencies from among the N frequencies. The N second light sources 16 output optical signals having respective frequencies from among the N frequencies different from the N frequencies. The terahertz optical signal switching unit 20 has inputs from the N first light sources 15 and second light sources 16, and outputs to two inputs of the N optical couplers 17.

[0089] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having N kinds of frequencies to N terahertz wireless signal transmission units 2. Then, by combining N first light sources 15 and N second light sources 16 (provided that the optical signal generated by the terahertz optical signal generation unit 1 is not only optically modulated but also in the terahertz band), it is possible to allocate N kinds of frequencies (|f 1i -f 2j |, i, j = 1 to N) can be diversified without any restrictions.

[0090] The configuration of a terahertz communication system according to No. 2-7 of the present disclosure is shown in Fig. 17. The following mainly describes the differences from the terahertz communication system according to No. 2-6 of the present disclosure.

[0091] The terahertz optical signal generation unit 1 includes M first light sources 15 and M second light sources 16. The terahertz optical signal switching unit 20 includes inputs from the M first light sources 15 and second light sources 16, and outputs to two inputs of N optical couplers 17 (N is an integer greater than M).

[0092] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M kinds of frequencies to N terahertz wireless signal transmission units 2. Then, by combining M first light sources 15 and M second light sources 16 (provided that the optical signals generated by the terahertz optical signal generation unit 1 are not only optically modulated but also in the terahertz band), M kinds of frequencies (|f 1i -f 2j |, i, j=1 to M) can be diversified without any restrictions. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2.

[0093] The configuration of a terahertz communication system according to No. 2-8 of the present disclosure is shown in Fig. 18. The following mainly describes the differences from the terahertz communication system according to No. 2-7 of the present disclosure.

[0094] The terahertz communication system S includes a terahertz optical signal switching unit 3. The terahertz optical signal generation unit 1 includes M optical couplers 17 and M optical modulators 18. The terahertz optical signal switching unit 20 includes inputs from M first light sources 15 and M second light sources 16, and outputs to two inputs of the M optical couplers 17. The terahertz optical signal switching unit 3 includes inputs from M optical modulators 18 and outputs to N terahertz radio signal transmission units 2 (N is an integer greater than M).

[0095] Therefore, it is possible to increase the degree of freedom in allocating terahertz optical signals having M kinds of frequencies to N terahertz wireless signal transmission units 2. Then, by combining M first light sources 15 and M second light sources 16 (provided that the optical signals generated by the terahertz optical signal generation unit 1 are not only optically modulated but also in the terahertz band), M kinds of frequencies (|f 1i -f 2j |, i, j=1 to M) can be diversified without any restrictions. Furthermore, since N>M, the same terahertz optical signal can be assigned to multiple terahertz radio signal transmitters 2, and the number of optical couplers 17 and optical modulators 18 can be reduced.

[0096] (First and second embodiments of the terahertz communication system according to the present disclosure) An example of the terahertz communication system No. 1-1 of the present disclosure (see FIG. 3) is shown in FIG. 19. Optical couplers 14-1 to 14-4 each couple a frequency (f S1 , f О1 ), (f S2 , f О2 ), (f S3 , f О3 ), (f S4 , f О4 ) and optically couples optical signals having frequencies f1, f2, f3, and f4. The terahertz optical signal switching unit 3 has inputs from optical couplers 14-1 to 14-4 and outputs to opto-electric converters 21-1 to 21-4. The opto-electric converters 21-1 to 21-4 perform opto-electric conversion on terahertz optical signals having frequencies f1, f2, f3, and f4, respectively. Time division multiplexing, which will be described later, is also possible in FIG. 19.

[0097] The coverage areas C1, C2, C3, and C4 store frequency bands f1, f2, f3, and f4, respectively, and may be entirely overlapping, as in intra-server communications, or may be separated by floor, as in intra-building communications. Mobile terminal T1 supports frequency band f1 and can receive signals within coverage area C1. Mobile terminal T2 supports frequency band f4 and can receive signals within coverage area C4.

[0098] An example of the first-second terahertz communication system (see FIG. 4) of the present disclosure is shown in FIG. 20. Optical couplers 14-1 and 14-2 each couple a frequency (f S1 , f О1 ), (f S2 , f О2 ) and optically couples optical signals having frequencies f1, f1, f2, and f2. The terahertz optical signal switching unit 3 has inputs from optical couplers 14-1 and 14-2 and outputs to optoelectric converters 21-1 to 21-4. The optoelectric converters 21-1 to 21-4 perform optoelectric conversion on terahertz optical signals having frequencies f1, f1, f2, and f2, respectively. Coverage ranges C1, C2, C3, and C4 store frequency bands f1, f1, f2, and f2, respectively. Portable terminal T1 corresponds to frequency band f1 and can move freely from coverage range C1 to coverage range C2. However, when multiple portable terminals receive signals in the same frequency band, it is difficult for all of the portable terminals to move freely.

[0099] FIG. 21 also shows an example of the terahertz communication system according to the first-second embodiment of the present disclosure (see FIG. 4). Furthermore, the terahertz optical signal switching unit 3 can switch among a plurality of combinations of terahertz optical signal allocations and perform time-division multiplexing. The terahertz optical signal switching unit 3 may perform switching after acquiring location information of the mobile terminal, or may perform switching randomly regardless of the location information of the mobile terminal. Therefore, the terahertz optical signals that are switched over time between a plurality of frequencies by time-division multiplexing can be allocated to each terahertz wireless signal transmission unit 2.

[0100] During a certain period of time division multiplexing shown in the left column of Figure 21, coverage areas C1, C2, C3, and C4 store frequency bands f1, f1, f2, and f2, respectively, and mobile terminal T1 corresponds to frequency band f1 and can move freely from coverage area C1 to coverage area C2, but mobile terminal T2 corresponds to frequency band f2 and cannot receive signals in coverage areas C1 and C2.

[0101] In the next period of time division multiplexing shown in the right column of Figure 21, coverage areas C1, C2, C3, and C4 store frequency bands f2, f2, f1, and f1, respectively, and mobile terminal T1 corresponds to frequency band f1 and can move freely from coverage area C2 to coverage area C3, and mobile terminal T2 corresponds to frequency band f2 and can receive in coverage areas C1 and C2.

[0102] Furthermore, even when multiple mobile terminals receive signals in the same frequency band, all of the mobile terminals can move freely. In FIG. 21, the mobile terminals do not have a frequency switching function, but as a modification, the mobile terminals may have a frequency switching function. Here, it is assumed that the frequency switching time of the mobile terminals is longer than the switching time of the terahertz optical signal switching unit 3. Therefore, when the mobile terminals are moving while receiving signals, the terahertz optical signal switching unit 3 only needs to switch, and when the mobile terminals are not receiving signals, the mobile terminals only need to switch frequencies.

[0103] An example of the first to third terahertz communication system (see FIG. 5) of the present disclosure is shown in FIG. 22. The terahertz optical signal switching unit 19 is a terahertz optical signal switching unit for switching the frequency f S1 , f S2 , f S3 , f S4 The optical couplers 14-1 to 14-4 receive, in any order, an optical signal having a frequency (f S1 , f О ), (f S2 , f О ), (f S3 , f О ), (f S4 , f О ) and optically couple optical signals having frequencies f1, f2, f3, and f4. The photoelectric converters 21-1 to 21-4 photoelectrically convert terahertz optical signals having frequencies f1, f2, f3, and f4, respectively. The coverage ranges C1, C2, C3, and C4 store frequency bands f1, f2, f3, and f4, respectively. The portable terminal T1 corresponds to the frequency band f1 and can receive signals within the coverage range C1. The portable terminal T2 corresponds to the frequency band f4 and can receive signals within the coverage range C4. Time division multiplexing is also possible in FIG. 22.

[0104] 23 shows an example of a first to fifth terahertz communication system (see FIG. 7) of the present disclosure. The terahertz optical signal switching unit 19 is a terahertz optical signal switching unit for a frequency f S1 , f S2 and outputs to optical couplers 14-1 and 14-2. The optical couplers 14-1 and 14-2 receive, in any order, an optical signal having a frequency (f S1 , f О ), (f S2 , f О ) and optically couples optical signals having frequencies f1, f1, f2, and f2. The terahertz optical signal switching unit 3 has inputs from optical couplers 14-1 and 14-2 and outputs to optoelectric converters 21-1 to 21-4. The optoelectric converters 21-1 to 21-4 perform optoelectric conversion on terahertz optical signals having frequencies f1, f1, f2, and f2, respectively. Coverage ranges C1, C2, C3, and C4 store frequency bands f1, f1, f2, and f2, respectively. The portable terminal T1 corresponds to frequency band f1 and can receive signals within the coverage range C1. The portable terminal T2 corresponds to frequency band f2 and can receive signals within the coverage range C4. Time division multiplexing is also possible in FIG. 23.

[0105] An example of the terahertz communication system according to the first to sixth embodiments of the present disclosure (see FIG. 8) is shown in FIG. 24. The terahertz optical signal switching unit 19 is a terahertz optical signal switching unit for switching the frequency f S1 , f S2 , f S3 , f S4 , f О1 , f О2 , f О3 , f О4 and outputs to two inputs of optical couplers 14-1 to 14-4. Si , f Оj ) (i, j=1 to 4) are optically coupled. Optoelectric converters 21-1 to 21-4 photoelectrically convert terahertz optical signals having frequencies f1, f2, f3, and f4, respectively. Coverage ranges C1, C2, C3, and C4 store frequency bands f1, f2, f3, and f4, respectively. Portable terminal T1 corresponds to frequency band f1 and can receive signals within coverage range C1. Portable terminal T2 corresponds to frequency band f4 and can receive signals within coverage range C4. Time division multiplexing is also possible in FIG. 24.

[0106] An example of the terahertz communication system according to the first to eighth embodiments of the present disclosure (see FIG. 10) is shown in FIG. 25. The terahertz optical signal switching unit 19 is a terahertz optical signal switching unit for switching the frequency f S1 , f S2 , f О1 , f О2 and outputs to two inputs of optical couplers 14-1 and 14-2. Si , f Оj ) (i, j=1, 2). The terahertz optical signal switching unit 3 has inputs from optical couplers 14-1 and 14-2 and outputs to optoelectric converters 21-1 to 21-4. The optoelectric converters 21-1 to 21-4 perform optoelectric conversion on terahertz optical signals having frequencies f1, f1, f2, and f2, respectively. Coverage ranges C1, C2, C3, and C4 store frequency bands f1, f1, f2, and f2, respectively. The portable terminal T1 corresponds to frequency band f1 and can receive signals within the coverage range C1. The portable terminal T2 corresponds to frequency band f2 and can receive signals within the coverage range C4. Time division multiplexing is also possible in FIG. 25.

[0107] An example of the terahertz communication system No. 2-1 (see FIG. 11) of the present disclosure is shown in FIG. 26. Optical couplers 17-1 to 17-4 each have a frequency (f 11 , f 21 ), (f 12 , f 22 ), (f 13 , f 23 ), (f 14 , f 24 ) and optically couples optical signals having frequencies f1, f2, f3, and f4. The terahertz optical signal switching unit 3 has inputs from optical couplers 17-1 to 17-4 and outputs to opto-electric converters 21-1 to 21-4. The opto-electric converters 21-1 to 21-4 perform opto-electric conversion on terahertz optical signals having frequencies f1, f2, f3, and f4, respectively. Time division multiplexing is also possible in FIG. 26.

[0108] The coverage areas C1, C2, C3, and C4 store frequency bands f1, f2, f3, and f4, respectively, and may be entirely overlapping, as in intra-server communications, or may be separated by floor, as in intra-building communications. Mobile terminal T1 supports frequency band f1 and can receive signals within coverage area C1. Mobile terminal T2 supports frequency band f4 and can receive signals within coverage area C4. [Industrial Applicability]

[0109] The terahertz communication system of the present disclosure multiplexes the terahertz communication system, thereby increasing the degree of freedom in assigning terahertz optical signals having each frequency to each terahertz wireless signal transmitter when storing multiple frequency bands. [Explanation of symbols]

[0110] S: Terahertz communication system 1: Terahertz optical signal generation unit 2: Terahertz wireless signal transmitter 3: Terahertz optical signal switching unit 4: Wavelength multiplexing section 11: Signal light source 12: Local light source 13: Optical modulator 14, 14-1~14-4, 14-1, 14-2: Optical coupler 15: 1st light source 16:Second light source 17, 17-1~17-4: Optical coupler 18: Optical modulator 19: Terahertz optical signal switching unit 20: Terahertz optical signal switching unit 21, 21-1 to 21-4: Photoelectric converter 22: Amplifier 23: Antenna C1, C2, C3, C4: Coverage T1, T2: Mobile terminal

Claims

1. a terahertz optical signal generation unit that, when optically coupling optical signals having different frequencies to generate a terahertz optical signal, sets a plurality of combinations of different frequencies that the optical signals have, and generates the terahertz optical signal having a plurality of frequencies; a plurality of terahertz radio signal transmitters that photoelectrically convert the terahertz optical signals having respective frequencies and transmit terahertz radio signals having respective frequencies; a terahertz optical signal switching unit that is capable of switching a combination of allocations of the terahertz optical signals among a plurality of combinations when allocating the terahertz optical signals having each frequency to each of the terahertz wireless signal transmission units; A terahertz communication system comprising:

2. M (M is an integer of 2 or more) terahertz optical signal generation units generate the terahertz optical signals having each of M frequencies, The terahertz optical signal switching unit has M inputs from the terahertz optical signal generating unit and N outputs to the terahertz wireless signal transmitting unit (N is an integer equal to or greater than M).

2. The terahertz communication system according to claim 1, wherein:

3. the terahertz optical signal generation unit includes M first light sources that output the optical signals having respective frequencies among M frequencies (M is an integer of 2 or more), and one second light source that outputs the optical signal having a frequency different from the M frequencies, The terahertz optical signal switching unit includes M inputs from the first light sources and N outputs (N is an integer equal to or greater than M) of the optical signals to an optical coupler.

2. The terahertz communication system according to claim 1, wherein:

4. the terahertz optical signal generation unit includes M first light sources that output the optical signals having respective frequencies among M frequencies (M is an integer of 2 or more), and one second light source that outputs the optical signal having a frequency different from the M frequencies, The terahertz optical signal switching unit is (1) disposed inside the terahertz optical signal generating unit, and includes M inputs from the first light sources and M outputs of the optical signals to an optical coupler, and (2) disposed between the terahertz optical signal generating unit and N (N is an integer greater than M) terahertz wireless signal transmitting units, and includes M inputs of the optical signals from the optical coupler and N outputs to the terahertz wireless signal transmitting units.

2. The terahertz communication system according to claim 1, wherein:

5. the terahertz optical signal generation unit includes M first light sources that output the optical signals having respective frequencies among M frequencies (M is an integer of 2 or more), and M second light sources that output the optical signals having respective frequencies among M frequencies different from the M frequencies, The terahertz optical signal switching unit includes M inputs from the first light source and the second light source, and N (N is an integer equal to or greater than M) outputs of the optical signals to two inputs of an optical coupler.

2. The terahertz communication system according to claim 1, wherein:

6. the terahertz optical signal generation unit includes M first light sources that output the optical signals having respective frequencies among M frequencies (M is an integer of 2 or more), and M second light sources that output the optical signals having respective frequencies among M frequencies different from the M frequencies, The terahertz optical signal switching unit is (1) disposed inside the terahertz optical signal generating unit, and includes M inputs from the first light source and the second light source, and M outputs of the optical signals to two inputs of an optical coupler, and (2) disposed between the terahertz optical signal generating unit and N (N is an integer greater than M) terahertz wireless signal transmitting units, and includes M inputs of the optical signals from the optical coupler and N outputs to the terahertz wireless signal transmitting units.

2. The terahertz communication system according to claim 1, wherein:

7. a wavelength multiplexing unit that is disposed between the terahertz optical signal switching unit and the plurality of terahertz wireless signal transmitting units and that wavelength-multiplexes the terahertz optical signals having a plurality of frequencies; 7. The terahertz communication system according to claim 1, wherein the terahertz communication system comprises: a first

8. The terahertz optical signal switching unit is capable of switching the combination of allocations of the terahertz optical signals among a plurality of combinations and performing time division multiplexing.

7. The terahertz communication system according to claim 1, wherein the terahertz communication system comprises: a first

9. The terahertz optical signal generation unit (1) optically modulates the optical signal having one frequency with a data signal, and optically couples the optically modulated optical signal having one frequency with an optical signal having another frequency that is not optically modulated, or (2) optically couples the optical signal having one frequency with an optical signal having another frequency, and optically modulates the optically coupled optical signal with a data signal.

7. The terahertz communication system according to claim 1, wherein the terahertz communication system comprises: a first

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