JP6960136B2 - Orthogonal frequency division multiplexing signal separation system - Google Patents

Description

The present invention relates to an Orthogonal Frequency Division Multiplexing Signal Separation System, and more particularly to an Orthogonal Frequency Division Multiplexing Signal Separation System capable of real-time separation of terahertz band Orthogonal Frequency Division Multiplexing (OFDM) signals.

Conventionally, an invention as described in Patent Document 1 is known as a circuit capable of separating orthogonal frequency division multiplexing signals. According to the present invention, by mainly realizing the optical discrete Fourier transform with a slab type star coupler, it can operate with an arbitrary number of channels and the optical circuit size can be kept small even if the number of channels increases. ..

Japanese Unexamined Patent Publication No. 2012-48172

However, in the above invention, there is a problem that the terahertz band OFDM signal that propagates at high speed cannot be supported, and therefore the terahertz band OFDM signal cannot be separated. Therefore, at present, the terahertz band OFDM signal is temporarily stored in the memory, and the stored memory data is read out at any time to separate the terahertz band OFDM signal, which is supported only by so-called offline processing. There was a problem that it could not be done.

Therefore, in view of the above problems, an object of the present invention is to provide an orthogonal frequency division multiplexing signal separation system capable of real-time separation of terahertz band OFDM signals.

The above object of the present invention is achieved by the following means. In addition, although the reference numerals of the embodiments described later are added in parentheses, the present invention is not limited thereto.

The orthogonal frequency division multiplexing signal separation system according to claim 1 separates a terahertz band orthogonal frequency division multiplexing signal having _{a plurality of subcarrier signals (d 0} , d ₁ , ..., d _n-1). Orthogonal frequency division multiplexing signal separation system for
A receiving unit (reception antenna unit 1) that receives a terahertz band orthogonal frequency division multiplexing signal, and
An RF conversion unit (2) that converts a terahertz band orthogonal frequency division multiplexing signal received by the reception unit (reception antenna unit 1) into an RF band orthogonal frequency division multiplexing signal.
An optical conversion unit (3) that converts an RF band orthogonal frequency division multiplexing signal converted by the RF conversion unit (2) into an optical orthogonal frequency division multiplexing signal.
Have a, a separation unit (demultiplexer 4) for separating the plurality of sub-carrier signals from the transformed light orthogonal frequency division multiplexed signal by the optical converter (3),
The separation unit (separation circuit 4) is
An optical branching unit (41) that branches the optical orthogonal frequency division multiplexing signal converted by the optical conversion unit (3) into a plurality of signals using a branching ratio variable directional coupler (41a).
An optical delay unit (42) that delays an optical orthogonal frequency division multiplexing signal branched by the optical branch unit (41), and an optical delay unit (42).
An optical Fourier transform unit (44) that Fourier transforms the optical orthogonal frequency division multiplex signal delayed by the optical delay unit (42) and separates it into a plurality of subcarrier signals.
An output waveguide (45-1 to 45-8) that outputs a plurality of subcarrier signals separated by the optical Fourier transform unit (44), respectively.
A phase shift imparting unit (second phase shift imparting unit 46) provided in each of the output waveguides (45-1 to 45-8), and
It has an interference unit (47) that interferes with light waves between the output waveguides (45-1 to 45-8) output via the phase shift imparting unit (second phase shift imparting unit 46). It is characterized in that it comprises.

Next, the effects of the present invention will be described with reference to the drawings. In addition, although the reference numerals of the embodiments described later are added in parentheses, the present invention is not limited thereto.

According to the invention of claim 1, the terahertz band orthogonal frequency division multiplex signal is converted (down-converted) into an RF band orthogonal frequency division multiplex signal by the RF conversion unit (2), and the RF conversion unit (2) is used. The RF band orthogonal frequency division multiplex signal converted (down-converted) is converted into an optical orthogonal frequency division multiplex signal by the optical conversion unit (3), and the converted optical orthogonal frequency division multiplex signal is converted into a separation unit (separation circuit). Since it is separated into a plurality of subcarrier signals in 4), even a terahertz band orthogonal frequency division multiplexing (OFDM) signal can be separated in real time.

Further, according to the invention of claim 1 , the optical orthogonal frequency division multiplexing signal converted by the optical conversion unit (3) is branched into a plurality of signals by using a branch ratio variable directional coupler (41a). Therefore, the separation channel characteristics can be changed. At this time, as the number of unused output waveguides (45-1 to 45-8) increases, the loss of the used output waveguides (45-1 to 45-8) does not increase, so that the output waveguides (45) do not increase. A phase shift imparting unit (second phase shift imparting unit 46) and an interference unit (47) are provided in the subsequent stages of -1 to 45-8). As a result, even if the number of output channels fluctuates, the fluctuation of the loss of the output channel used can be reduced.

It is a block diagram which shows one Embodiment of the orthogonal frequency division multiplexing signal separation system which concerns on this invention. It is a figure which shows the spectral shape of the orthogonal frequency division multiplexing (OFDM) signal of a terahertz band. It is a figure which shows the frequency characteristic of the signal separated by the conventional separation circuit (Δf ₈ = 10GHz, Δf: separation channel frequency interval, the subordinate digit of Δf is the number of separable channels). It is a figure which shows the frequency characteristic of the signal separated by the conventional separation circuit (Δf ₄ = 20GHz, Δf: separation channel frequency interval, the subordinate digit of Δf is the number of separable channels). It is a figure which shows the frequency characteristic of the signal separated by the conventional separation circuit (Δf ₂ = 40GHz, Δf: separation channel frequency interval, the subordinate digit of Δf is the number of separable channels). _{It is a figure which shows the frequency characteristic of the signal (Δf 8} = 10 GHz, Δf: separation channel frequency interval, the subscript of Δf is the number of separable channels) separated by the separation circuit which concerns on this embodiment. _{It is a figure which shows the frequency characteristic of the signal (Δf 4} = 20GHz, Δf: separation channel frequency interval, the subscript of Δf is the number of separable channels) separated by the separation circuit which concerns on this embodiment. _{It is a figure which shows the frequency characteristic of the signal (Δf 2} = 40GHz, Δf: separation channel frequency interval, the subscript digit of Δf is the number of separable channels) separated by the separation circuit which concerns on this embodiment. It is a block diagram which shows one Embodiment of the optical orthogonal frequency division multiplexing signal separation circuit.

Hereinafter, the orthogonal frequency division multiplexing signal separation system according to the present invention will be specifically described with reference to the drawings. In the following description, when the directions of up, down, left, and right are shown, it means the up, down, left, and right when viewed from the front of the illustration.

As shown in FIG. 1, the orthogonal frequency division multiplex signal separation system has a receiving antenna unit 1 capable of receiving a terahertz band orthogonal frequency division multiplex (OFDM) signal and an orthogonality of the terahertz band received by the receiving antenna unit 1. The RF conversion unit 2 that converts a frequency division multiplexing (OFDM) signal into an RF band orthogonal frequency division multiplexing (OFDM) signal and the RF band orthogonal frequency division multiplexing (OFDM) signal converted by the RF conversion unit 2 are used. It is composed of an optical conversion unit 3 that converts an optical orthogonal frequency division multiplexing (OFDM) signal and a separation circuit 4 that separates an optical orthogonal frequency division multiplexing (OFDM) signal converted by the optical conversion unit 3.

As shown in FIG. 2, the terahertz band orthogonal frequency division multiplexing (OFDM) signals are a plurality of subcarrier signals d ₀ , d ₁ , ..., d _{n-1 having different carrier frequencies (center frequencies).} By using the orthogonal relationship between them, the occupied bandwidth to be transmitted can be suppressed. The orthogonal relationship in orthogonal frequency division multiplexing (OFDM) is the symbol rate 1 / T (T is each subcarrier signal) of the modulated signal of _{each subcarrier signal d 0} , d ₁ , ..., d _n-1. When the relationship of Δf = 1 / T is established between the subcarrier signal frequency interval Δf) and the subcarrier signal frequency interval Δf, the separation and identification of each subcarrier signal even if the transmission spectra of the subcarrier signals overlap. Is possible.

Thus, the terahertz band orthogonal frequency division multiplexing (OFDM) signal as described above is transmitted from a base station, mobile station, or the like (not shown), and is received by the receiving antenna unit 1 shown in FIG. Then, the terahertz band orthogonal frequency division multiplexing (OFDM) signal received by the receiving antenna unit 1 is converted into an RF band orthogonal frequency division multiplexing (OFDM) signal by the RF conversion unit 2 shown in FIG. It becomes. More specifically, as shown in FIG. 1, the RF conversion unit 2 includes a mixer 20 and a local signal generator 21, and the receiving antenna unit 1 is used for the terahertz band orthogonal frequency division multiplexing. Upon receiving the (OFDM) signal, the mixer 20 uses the locally-generated signal output by the station-generated signal generator 21 to output the received terahertz-band orthogonal frequency-divided multiplexing (OFDM) signal to the RF-band orthogonal frequency-divided multiplexing (OFDM) signal. It is down-converted to a (OFDM) signal, and the RF band orthogonal frequency division multiplexing (OFDM) signal after down-conversion is output to the optical conversion unit 3.

The optical conversion unit 3 is composed of an optical modulator that converts an electric signal into an optical signal (E / O conversion) and outputs the signal, and is an RF band orthogonal frequency division multiplexing (OFDM) signal output from the RF conversion unit 2. Is converted into an optical orthogonal frequency division multiplexing (OFDM) signal. Then, the optical orthogonal frequency division multiplexing (OFDM) signal is output to the separation circuit 4 in this way.

The separation circuit 4 separates each subcarrier signal of the optical orthogonal frequency division multiplexing (OFDM) signal converted by the optical conversion unit 3, and is converted by the optical conversion unit 3 as shown in FIG. An input waveguide 40 into which an optical orthogonal frequency division multiplexing (OFDM) signal is input, an optical branching unit 41 that N-branches the input optical orthogonal frequency division multiplexing (OFDM) signal, and an N-branched optical orthogonal frequency division multiplexing (OFDM) signal. An optical delay section 42 that delays the (OFDM) signal, a first phase shift imparting section 43 that imparts a desired phase shift to the delayed optical orthogonal frequency division multiplexing (OFDM) signal, and a desired phase shift are imparted. An optical Fourier conversion unit 44 that performs Fourier conversion processing on an optical orthogonal frequency division multiplexing (OFDM) signal and separates it into each subcarrier signal, and an output waveguide 45-that outputs each subcarrier signal output from the optical Fourier conversion unit 44. Interference section 47 that interferes with light waves between 1-45-8, the second phase shift imparting section 46 provided so that light waves can efficiently interfere with each other in the interference section 47 described later, and the output waveguide. It is composed of and.

As shown in FIG. 1, the optical branching unit 41 sequentially connects the branching ratio variable directional coupler 41a in sequence, and transmits the optical orthogonal frequency division multiplexing (OFDM) signal input to the input waveguide 40 at an arbitrary branching ratio. It is designed to branch 2 to N. As the branch ratio variable directional coupler 41a, for example, a symmetric Mach changer type interferometer can be used.

On the other hand, the optical delay unit 42 is composed of delay lines 42-1 to 42-N, and which delay line 42-1 to 42-N is used for the N-branched optical orthogonal frequency division multiplexing (OFDM) signal. The number of channels for separating the optical orthogonal frequency division multiplexing (OFDM) signals is determined accordingly (in the present embodiment, an example of N = 8 is shown with respect to the delay lines 42-1 to 42-N. ing). Then, assuming that the waveguide length difference of the waveguide used in the delay lines 42-1 to 42-N is ΔLu, when c is the speed of light and n is the effective refractive index of the waveguide used as the light path, the free spectrum is obtained. Since the range (FSR) is expressed as FSR = c / (n · ΔLu), the difference in waveguide length of the waveguide used in the delay lines 42-1 to 42-N determines the free spectrum range. Become. Then, the delay lines 42-1 to 42-N convert the serial signal, which is an optical orthogonal frequency division multiplexing (OFDM) signal, input within the same time as the symbol time T of each subcarrier signal into a parallel signal. It becomes possible to do. It is the orthogonal relationship in orthogonal frequency division multiplexing (OFDM) that converts the serial signal, which is an optical orthogonal frequency division multiplexing (OFDM) signal input within the same time as the symbol time T, into a parallel signal. Is established because it is limited to the same time as the symbol time T.

The first phase shift imparting unit 43 is composed of a thermo-optical phase shifter or the like, and is delayed by the delay line used (light is input) among the delay lines 42-1 to 42-N. It is for compensating for the phase error of the OFDM) signal, and is provided for each of the delayed optical orthogonal frequency division multiplexing (OFDM) signals. Further, the first phase shift imparting unit 43 also sets the center frequency of the frequency characteristics (see FIGS. 3A to 4C) of the optical signal Fourier transformed by the optical Fourier transform unit 44 in the subsequent stage to a desired value. Used.

On the other hand, in order to separate the optical orthogonal frequency division multiplex (OFDM) signal directly into each subcarrier signal at high speed in the optical region, optical discrete Fourier transform (optical DFT) or optical high speed is used as a component thereof. An optical element capable of performing a Fourier transform (Optical Fast Fourier Transform: optical FFT) is indispensable. Therefore, in the present embodiment, the optical Fourier transform unit 44 is composed of an N input N output slab type star coupler. As a result, N optical orthogonal frequency division multiplexing (OFDM) signals (N = 8 in FIG. 1) to which a desired phase shift is applied are discrete Fourier transformed by an N input N output slab type star coupler. At the same time, the discrete Fourier transformed N optical signals (N = 8 in FIG. 1) are output at different positions. The principle that N optical signals are discrete Fourier transformed by an N-input N-output slab type star coupler and N optical signals are output to different positions is described in JP2012-48172. Since it is the same as the content shown, detailed description will be omitted.

By the way, the conventional separation circuit includes the above-mentioned optical branching section 41, optical delay section 42, first phase shift imparting section 43, optical Fourier transform section 44, and output waveguides 45-1 to 45-8. Each subcarrier signal that is configured and separated from the optical orthogonal frequency division multiplexing (OFDM) signal is output via the output waveguides 45-1 to 45-8. Even in this way, since the optical orthogonal frequency division multiplexing (OFDM) signal is separated, there is no problem in separating the terahertz band orthogonal frequency division multiplexing (OFDM) signal in real time. However, in the conventional separation circuit, there is a problem that the loss of the output waveguide increases when the number of delay lines used is reduced. That is, when the separable channel spacing is Δf when all the delay lines 42-1 to 42-N are used, for example, if k adjacent delay lines are used, the free spectrum range (FSR) is Since it is the same as the value when all delay lines are used, the number of separated channels is k, and the separable channel interval is Δf _k = (8 / k) Δf (in the present embodiment, a maximum of 8 channels). It is 8 / k because it shows an example of separating optical orthogonal frequency division multiplexing (OFDM) signals).

Here, since the output waveguide of the N input N output slab type star coupler in the optical Fourier transform unit 44 is arranged so as to separate the signals for each Δf, the N input N output in the optical Fourier transform unit 44 A separation signal is output every 8 / k-1 output waveguide of the slab type star coupler, and the other output waveguides are not used (useless). The values that k can take are only 2, 4, and 8. Therefore, output waveguides of other values are not used (useless).

However, since the optical signal is also output from the unused (useless) output waveguide, the loss of the used output waveguide increases as the number of unused (useless) output waveguides increases. .. In this respect, to explain by showing a specific example, if the values of the free spectrum range are 80 GHz, Δf = 10 GHz, k = _{8 , 4 , 2} , then Δf 8 = 10 GHz, Δf 4 = 20 GHz, Δf 2 = 40 GHz. , _{The frequency characteristic of Δf 8} = 10 GHz is as shown in FIG. 3A, the frequency characteristic of Δf ₄ = 20 GHz is as shown in FIG. 3B, and _{the frequency characteristic of Δf 2} = 40 GHz is as shown in FIG. 3C. Become.

Here, when the frequency characteristics shown in FIGS. 3A to 3C are compared, the frequency characteristics shown in FIG. 3B have a loss increased by 3 dB from the frequency characteristics shown in FIG. 3A, and the frequency characteristics shown in FIG. 3C are shown in FIG. 3A. It can be seen from the frequency characteristics that the loss is increased by 6 dB. From this, it can be seen that the loss of the output waveguide used increases as the number of unused (useless) output waveguides increases. In the present embodiment, the loss of the frequency characteristic shown in FIG. 3A is 0 dB, but this is set to 0 dB in order to make the fluctuation of the loss easy to understand, and is actually a component. There is some loss due to the loss of.

Thus, in order to solve the above-mentioned problems, in the present embodiment, the second phase shift imparting unit 46 and the interference unit 47 are provided after the optical Fourier transform unit 44. That is, the second phase shift imparting unit 46 is composed of a thermo-optical phase shifter or the like, and is for efficiently interfering light waves with the interference unit 47 in the subsequent stage, and is used for each of the output waveguides 45-1 to 45-8. It is provided in. Further, the interference unit 47 sequentially connects the branch ratio variable directional coupler 47a having two inputs and two outputs in sequence. As a result, the fluctuation of the loss of the output channel is reduced by interfering the light waves between the output waveguides 45-1 to 45-8. Specifically, for example, when k = 2, all the branch ratio variable directional couplers 47a are used to interfere with each other, and the two output channels (CH1, CH5) or (CH2, CH6) are used to output. Then, when k = 4, among the branch ratio variable directional couplers 47a, only the branch ratio variable directional couplers 47a arranged vertically in four rows are used to interfere with each other, and the branch ratio variable directions arranged in four rows vertically are used to interfere with each other. The four output channels (CH0, CH2, CH4, CH6), with the coupling ratio of the bifurcated ratio variable directional coupler 47a provided in two rows vertically after the sex coupler 47a set to 0 and let the light wave pass through, Alternatively, output is performed from (CH1, CH3, CH5, CH7). Further, when k = 8, the coupling ratio of all the branch ratio variable directional couplers 47a is set to 0 and the light wave is passed through, that is, the light wave is not interfered and all are passed through, and 8 output channels (CH0 to CH7) are used. ) To output. The results of this frequency output characteristic are shown in FIGS. 4A to 4C. The frequency characteristic shown in FIG. 4A shows the case of k = 8, the frequency characteristic shown in FIG. 4B shows the case of k = 4, and the frequency characteristic shown in FIG. 4C shows the case of k = 2. Similar to those shown in FIGS. 3A to 3C, the values in the free spectrum range are 80 GHz, Δf is 10 GHz, Δf ₈ is 10 GHz, Δf ₄ is 20 GHz, and Δf ₂ is 40 GHz.

Here, when the frequency characteristics shown in FIGS. 4A to 4C are compared, no loss occurs even when the frequency characteristics shown in FIG. 4A and the frequency characteristics shown in FIG. 4B are compared, and the frequency characteristics shown in FIG. 4A are not generated. Comparing the frequency characteristics shown in FIG. 4C with that of FIG. 4C, it can be seen that no loss has occurred. From this, it can be seen that if the interference unit 47 is provided so that the light waves between the output waveguides interfere with each other, the fluctuation of the loss of the output channel can be reduced even if the number of output channels fluctuates. In the present embodiment, an example in which the second phase shift imparting unit 46 is provided is shown, but it may not be provided if there is no need to efficiently interfere with the light waves in the interference unit 47.

Thus, in the separation circuit 4 configured as described above, the optical orthogonal frequency division multiplexing (OFDM) signal converted by the optical conversion unit 3 is separated into each subcarrier signal.

According to the present embodiment described above, the Terrahertz band orthogonal frequency division multiplexing (OFDM) signal is down-converted to the RF band orthogonal frequency division multiplexing (OFDM) signal by the RF conversion unit 2, and after down-conversion. Since the RF band orthogonal frequency division multiplexing (OFDM) signal is converted into an optical orthogonal frequency division multiplexing (OFDM) signal by the optical conversion unit 3, and then separated by the separation circuit 4, the terahertz band Even orthogonal frequency division multiplexing (OFDM) signals can be separated in real time.

Since the signal converted into the separable optical orthogonal frequency division multiplexing (OFDM) signal is input to the separation circuit 4, the signal is not limited to the one shown in the present embodiment, and the optical orthogonal frequency division multiplexing (OFDM) signal is not limited to the one shown in the present embodiment. As long as it can separate the OFDM) signal, it can be separated from the conventionally reported optical discrete Fourier transform integrated circuit and optical fast Fourier transform integrated circuit, regardless of whether it is for fixed or variable symbol rate subcarrier signal separation. It is possible to use a circuit.

However, it is preferable to use the separation circuit 4 shown in the present embodiment because the fluctuation of the loss of the output channel can be reduced even if the number of output channels fluctuates.

If the orthogonal frequency division multiplexing signal separation system in the present embodiment is used, it is flexible in a place where an optical fiber line cannot be physically laid, or in a place where mobile communication is required instead of a fixed line (relay venue, indoor, etc.). Large-capacity wireless communication capable of transmitting high-quality, large-capacity high-definition images such as 4K, 8K, and 3D images in real time becomes possible.

On the other hand, in the present embodiment, only an example in which the separation circuit 4 is used for real-time separation of orthogonal frequency division multiplexing (OFDM) signals for terahertz band communication is shown, but the separation circuit 4 is not limited to this, and the separation circuit 4 is optical. As an optical orthogonal frequency division multiplex signal separation circuit for communication, it can also be used for an optical orthogonal frequency division multiplex (optical OFDM) signal other than a terahertz band orthogonal frequency division multiplex (OFDM) signal. That is, as shown in FIG. 5, this optical orthogonal frequency division multiplexing signal separation circuit is configured in the same manner as the separation circuit 4 shown in FIG. 1, and an optical orthogonal frequency division multiplexing signal (optical OFDM) can be input. There is. By using such an optical orthogonal frequency division multiplexing signal separation circuit, it is possible to reduce fluctuations in the loss of the output channels used even if the number of output channels fluctuates, as described above. Since the configuration of the separation circuit 4 is the same as that shown in FIG. 1, detailed description thereof will be omitted. Further, the optical orthogonal frequency division multiplex signal (optical OFDM) is a plurality of subcarrier signals d having different carrier frequencies (center frequencies), as shown in FIG. 2, like the terahertz band orthogonal frequency division multiplex (OFDM) signal. _{By using the orthogonal relationship between 0} , d ₁ , ..., d _n-1 , the occupied bandwidth to be transmitted can be suppressed.

The optical orthogonal frequency division multiplex signal separation circuit will be described in more detail. As conventional optical orthogonal frequency division multiplex signal separation circuits, for example, an optical branching unit 41, an optical delay unit 42, and a first phase shift imparting unit 43 , The optical Fourier transform unit 44 and the output waveguides 45-1 to 45-8 are separated from the optical orthogonal frequency division multiplexing (OFDM) signal via the output waveguides 45-1 to 45-8. It is known that each subcarrier signal is output.

However, in such an optical orthogonal frequency division multiplexing signal separation circuit, as described above, there is a problem that the loss of the output waveguide increases when the number of delay lines used is reduced. This point is as described with reference to FIGS. 3A to 3C.

Therefore, as a means for solving such a problem, this problem can be solved by using an optical orthogonal frequency division multiplexing signal separation circuit having a configuration of the separation circuit 4. That is, as a specific means, the optical orthogonal frequency division multiplexing signal separation circuit is
Optical Orthogonal Frequency Division Multiplexing Signals Branching Multiple Signals (41)
An optical delay unit (42) that delays an optical orthogonal frequency division multiplexing signal branched by the optical branch unit (41), and an optical delay unit (42).
An optical Fourier transform unit (44) that Fourier transforms the optical orthogonal frequency division multiplex signal delayed by the optical delay unit (42) and separates it into a plurality of subcarrier signals.
An output waveguide (45-1 to 45-8) that outputs a plurality of subcarrier signals separated by the optical Fourier transform unit (44), respectively.
It suffices to have an interference portion (47) that interferes with light waves between the output waveguides (45-1 to 45-8).

Thus, the optical orthogonal frequency division multiplexing signal separation circuit configured as described above has the above configuration, so that a plurality of subcarrier signals separated by the optical Fourier transform unit (44) can be obtained. By interfering the light waves between the output waveguides (45-1 to 45-8) that output The fluctuation of the loss can be reduced. Therefore, the above problem can be solved. Specific examples of this point are as described with reference to FIGS. 4A to 4C.

Thus, the separation circuit 4 can be used as an optical orthogonal frequency division multiplexing signal separation circuit for optical orthogonal frequency division multiplexing (optical OFDM) signals other than terahertz band orthogonal frequency division multiplexing (OFDM) signals.

1 Receiver antenna (receiver)
2 RF conversion unit 3 Optical conversion unit 4 Separation circuit (separation unit)
41 Optical branch 42 Optical delay 44 Optical Fourier transform 45-1 to 45-8 Output waveguide 47 Interference d _{0 to d n-1} Subcarrier signal

Claims (1)

An orthogonal frequency division multiplexing signal separation system for separating terahertz band orthogonal frequency division multiplexing signals having multiple subcarrier signals.
A receiver that receives terahertz band orthogonal frequency division multiplexing signals,
An RF conversion unit that converts a terahertz band orthogonal frequency division multiplexing signal received by the reception unit into an RF band orthogonal frequency division multiplexing signal, and an RF conversion unit.
An optical conversion unit that converts an RF band orthogonal frequency division multiplexing signal converted by the RF conversion unit into an optical orthogonal frequency division multiplexing signal, and an optical conversion unit.
Have a, a separation unit that separates a plurality of sub-carrier signals from the transformed light orthogonal frequency division multiplexed signal by the optical converter,
The separation part
An optical branching unit that branches the optical orthogonal frequency division multiplexing signal converted by the optical conversion unit into a plurality of signals using a branching ratio variable directional coupler, and an optical branching unit.
An optical delay section that delays the optical orthogonal frequency division multiplexing signal branched at the optical branch section, and an optical delay section.
An optical Fourier transform unit that Fourier transforms the optical orthogonal frequency division multiplex signal delayed by the optical delay unit and separates it into a plurality of subcarrier signals.
An output waveguide that outputs a plurality of subcarrier signals separated by the optical Fourier transform unit, and an output waveguide that outputs each of the plurality of subcarrier signals.
A phase shift imparting unit provided in each of the output waveguides and
An orthogonal frequency division multiplexing signal separation system including an interference unit that interferes with light waves between the output waveguides output via the phase shift imparting unit.

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