JP4535423B2 - Optical transmitter and optical-radio fusion communication system - Google Patents

Description

The present invention relates to an optical transmitter in an optical-radio fusion communication system using broadband signal light, and more particularly, to an optical transmitter and an optical-radio fusion communication system that transmit a desired radio signal as an optical signal to a radio base station.

  1, 2, and 3 show examples of an optical transmitter, a radio base station, and a wireless subscriber terminal in a conventional optical-wireless communication system, and FIG. 4 shows a conventional optical-wireless communication. An example of the spectrum of the electrical frequency and optical frequency in a system is shown.

  An optical signal (101g) is transmitted from the optical transmitter 101 to the radio base station 109 via an optical transmission line. Here, the output signal from the electric oscillator 105 is an electric carrier signal (101c) having a frequency equal to half the frequency of the radio signal, and the optical modulator 104 is used for the output light (101b) of the single spectrum light source 103. Then, optical phase modulation is performed based on the electrical modulation signal (101c) to obtain an output optical modulation signal (101d). On the other hand, using an electric oscillator 107 and an electric modulator 108 that generate an output signal (101e) of an arbitrary intermediate frequency band based on a digital signal (101a) that can take M values inputted to the input terminal 102. The multimode light source 106 is directly modulated by the generated modulation signal (101f) in the intermediate frequency band. At the same time, the output light modulation signal (101d) is input to the multimode light source 106 and injection locking is performed. An optical signal (101g) synchronized with two modes of the output light modulation signal of the multimode light source is obtained.

  In the radio base station 109, a difference frequency component (101h) is obtained by simultaneously square-detecting such an optical signal (101g) with one light receiving element 110, but this signal is not required using the bandpass filter 111. A signal (101i) obtained by removing a simple signal is amplified as necessary and transmitted as a radio wave from the antenna 112, so that an electric signal in the millimeter wave band is not directly transmitted and the millimeter wave is transmitted to the radio base station. It is possible to transmit a millimeter-wave band radio signal without preparing a band electric oscillator.

The radio wave (101i) transmitted from the wireless base station 109 is received by the antenna 114 in the wireless subscriber terminal 113. If the optical modulator 101 performs frequency modulation or phase modulation by the electric modulator 108, Since the signal radio wave (101i) is a double sideband signal including an unmodulated carrier wave signal, square detection is performed by the multiplier 115 using a non-linear element such as a mixer diode, and the output electric signal (101j) of the multiplier 115 is further detected. Is passed through the low-pass filter 116, and an intermediate frequency band electric modulation signal (101k) can be obtained without preparing a millimeter wave band electric oscillator. In addition, since the frequency instability of the optical signal (101g) is canceled at the time of square detection in the wireless base station, the electrical modulation signal (101k) in the intermediate frequency band obtained at the wireless subscriber terminal 113 is very The frequency stability is high (see Non-Patent Document 1).
Masahiro Ogura, Keizo Inagaki, Takashi Ohira, “Study on Millimeter-Wave Multiplexed Signal Source Using Two-Mode Injection-Locked FP Laser”, Proceedings of the 2001 IEICE General Conference, The Institute of Electronics, Information and Communication Engineers, March 2001 7th, B-5-259

  1, 2, 3, and 4, an optical modulator having a frequency band of a radio signal in order to stably synchronize two modes of a multimode light source in an optical transmitter. It is necessary to prepare. In addition, in the radio base station, when square detection is performed by the light receiving element, the difference frequency component of the combination of the received optical signals is output. Since this output signal includes a plurality of signals unnecessary for signal transmission, A band-pass filter in the frequency band of the radio signal for removing unnecessary signals is required. When transmitting a wideband signal, it is expected to use the millimeter wave band that can secure a wide signal band as the frequency of the radio signal, but the optical transmitter becomes expensive because it includes an optical modulator of the millimeter wave band. In addition, since the millimeter-wave bandpass filter is difficult to design, the configuration of the base station becomes complicated.

An object of the present invention is to provide an optical transmitter and an optical-radio fusion communication system that can be realized at low cost and with a configuration of a wireless base station together with the optical transmitter itself. To do.

In the present invention, in order to achieve the above object, in claim 1, the received optical signal is square-detected, converted into an electric signal, and the desired radio signal is transmitted to the radio base station that transmits the electric signal as a radio signal. The first and second optical transmitters generate a single-spectrum optical signal in which the difference between the center frequencies f _c1 and f _c2 (f _c2 −f _c1 ) is equal to the frequency f _{RF of the} radio signal. A single spectrum light source, an optical multiplexer for combining the first and second optical signals output from the first and second single spectrum light sources, and a radio wave transmitted from the radio base station. electrical oscillator for generating an electrical carrier signal having a frequency (f _IF / 2) equal to the frequency f _IF of half of the intermediate frequency signal in the radio terminal to obtain an intermediate frequency signal by passing the square-law detection with the low-pass filter Te, electrical From the oscillator The output electric carrier wave signal is subjected to amplitude modulation or frequency modulation by an electric digital signal m (m = 1, 2,..., M) that can take M values , and f _IF / 2. An electric modulator that outputs an electric amplitude modulation signal or electric frequency modulation signal having a frequency, and an optical signal that is output from the optical multiplexer, a carrier wave using an electric amplitude modulation signal or an electric frequency modulation signal from the electric modulator provide Reinforced double sideband suppressed light _{modulation, f c1 + f IF / 2} , f c1 -f IF / 2, f c2 + f IF / 2, and outputs an optical signal having a frequency of f _c2 -f _IF / 2 An optical transmitter characterized by comprising an optical modulator is used as a solution.

  According to the first aspect of the present invention, four optical signals can be transmitted from the optical transmitter, and an amplitude modulation signal or a frequency modulation signal is output as an output of the light receiving element of the radio base station in a desired radio signal frequency band. In addition, it is possible to obtain three radio signals having different frequency intervals by the frequency of the intermediate frequency signal.

In the first aspect of the invention, the electric field E _opt of the optical signal transmitted at the time of amplitude modulation can be expressed by the following equation.

E _opt = a _m cos {2π (f _c2 + f _IF / 2) t + φ ₂ (t)}
+ A _m cos {2π (f _c2 −f _IF / 2) t + φ ₂ (t)}
+ A _m cos {2π (f _c1 + f _IF / 2) t + φ ₁ (t)}
+ A _m cos {2π (f _c1 -f _IF / 2) t + φ ₁ (t)} (1)
However, where, a _m is a field amplitude modulation component, m is (a M is 2 n (n is a natural number), M value signal is a signal of n bits) M value input digital signal (m of = 1, 2,..., M), f _c1 and f _c2 are the optical frequencies of the first and second optical signals, f _IF is the intermediate frequency, and φ ₁ (t) and φ ₂ (t) are the first and first optical signals. Let represent the phase noise of two single spectrum light sources.

The electric field E _{RF of the} radio signal obtained by square detection of this optical signal with the light receiving element can be expressed as follows.

^{_{E RF αa m 2 cos {2π}} (f RF + f IF) t + φ 2 (t) -φ 1 (t)}
_{^{+ 2a m 2 cos {2πf RF}} t + φ 2 (t) -φ 1 (t)}
^{_{+ A m 2 cos {2π (}} f RF -f IF) t + φ 2 (t) -φ 1 (t)} ... (2)
Here, f _RF represents a radio signal frequency, and f _RF = f _{c2 −c1} .

  At the wireless subscriber terminal, after receiving these high-frequency radio signal radio waves with an antenna, square detection is performed by a non-linear element such as a diode, and a low pass filter is used to prepare a local oscillator, that is, an electric oscillator in the radio signal frequency band. Without this, electrical amplitude modulation in the low frequency band can be obtained as the intermediate frequency signal.

The electric field E _IF of the intermediate frequency band signal can be expressed as:

^{_{E IF α4a m 4 cos (2πf}} IF t) ... (3)
From equation (3), the phase noise of the first and second single optical spectrum light sources is canceled during the square detection of electricity at the wireless subscriber terminal, and an intermediate frequency signal with high frequency stability can be obtained. I understand.

The optical transmitter for transmitting a desired radio signal as an optical signal to a radio base station that squarely detects the received optical signal, converts it to an electrical signal, and transmits the electrical signal as a radio signal. first and second single-spectrum light source difference frequency _{f c1, f c2 (f c2} -f c1) to generate an optical signal of a single spectrum is equal to the frequency f _RF of the radio signal, first and second An optical multiplexer that multiplexes the first and second optical signals output from two single spectrum light sources, and a radio wave that is transmitted from the radio base station, squarely detected, and passed through a low-pass filter. electrical oscillator for generating an electrical carrier signal having a frequency (f _IF / 2) equal to the frequency f _IF of half of the intermediate frequency signal in a wireless terminal to obtain a frequency signal with respect to an electrical carrier wave signal output from the electrical oscillator, input An electric phase modulator that performs phase modulation on an electric digital signal m (m = 1, 2,..., M) that can take M values, and outputs an electric phase modulation signal. m + 1) and output electrical phase modulation signal of the phase with respect to, the output electrical phase modulation signal to the electrical digital signal m and facilities phase modulation such as phase difference of [pi / M of the phase, the frequency of f _IF / 2 an electric phase modulator for outputting an electrical phase modulated signal having, with respect to the optical signal output from the optical multiplexer, and facilities the double sideband suppressed carrier light modulated by the electric phase-modulated signal from the electric modulator, and an optical modulator that outputs an optical signal having frequencies of f _c1 + f _IF / 2, f _c1 −f _IF / 2, f _c2 + f _IF / 2, and f _c2 −f _IF / 2. The optical transmitter is a solution.

  According to the second aspect of the present invention, four optical signals can be transmitted from the optical transmitter, and the output of the light receiving element of the radio base station includes the phase modulation signal in the desired radio signal frequency band, and the frequency interval However, it is possible to obtain three-wave radio signals different from each other by the frequency of the intermediate frequency signal.

In the invention of claim 2, the electric field E _opt of the optical signal to be transmitted can be expressed by the following equation.

E _opt = A cos {2π (f _c2 + f _IF / 2) t + φ _m + φ ₂ (t)}
+ A cos {2π (f _c2 −f _IF / 2) t−φ _m + φ ₂ (t)}
+ A cos {2π (f _c1 + f _IF / 2) t + φ _m + φ ₁ (t)}
+ A cos {2π (f _c1 −f _IF / 2) t−φ _m + φ ₁ (t)} (4)
Where A is the electric field amplitude, f _c1 and f _c2 are the optical frequencies of the first and second optical signals, f _IF is the intermediate frequency, and m is the M value (M is the nth power of 2 (n is a natural number)) , M value signal is an n-bit signal), input digital signals (m = 1, 2,..., M), φ ₁ (t), φ ₂ (t) are first and second single signals. It represents the phase noise of the spectrum light source, and φ _m satisfies φ = φ _{m + 1} −φ _m = π / M.

The electric field E _{RF of the} radio signal obtained by square detection of this optical signal with the light receiving element can be expressed as follows.

E _RF ∝A ² cos {2π (f _RF + f _IF ) t + 2φ _m + φ ₂ (t) −φ ₁ (t)}
+ 2A ² cos {2πf _RF t + φ ₂ (t) −φ ₁ (t)}
+ A ² cos {2π (f _RF −f _IF ) t−2φ _m + φ ₂ (t) −φ ₁ (t)} (5)
Here, f _RF represents a radio signal frequency, and f _RF = f _c2 −f _c1 .

At the wireless subscriber terminal, after receiving these high-frequency radio signal radio waves with an antenna, square detection is performed by a non-linear element such as a diode, and a low pass filter is used to prepare a local oscillator, that is, an electric oscillator in the radio signal frequency band. Without being performed, the electrical phase in the low frequency band where the phase difference φ ′ (= 2φ _{m + 1} −2φ _m ) with respect to the M-value signal of the electrical digital signal input to the input terminal is 2π / M as the intermediate frequency signal. A signal can be obtained.

The electric field E _IF of the intermediate frequency band signal can be expressed as:

E _IF ∝4A ⁴ cos (2πf _IF t + 2φ _m ) (6)
From the equation (6), the phase noise of the first and second single optical spectrum light sources is canceled during the square detection of electricity at the wireless subscriber terminal, and an intermediate frequency signal with high frequency stability can be obtained. I understand.

In an optical transmitter for transmitting an optical signal for transmitting a desired radio signal to a radio base station that squarely detects a received optical signal, converts the optical signal into an electric signal, and transmits the electric signal as a radio signal, first and second single-spectrum light source difference in the respective center frequencies _{f c1, f c2 (f c2} -f c1) to generate an optical signal of a single spectrum is equal to the frequency f _RF of the radio signal, the An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources, and a radio wave transmitted from the radio base station , squarely detected, and passed through a low-pass filter. intermediate electrical oscillator for generating an electrical carrier signal having a frequency equal to the frequency f _IF of the intermediate frequency signal in a wireless terminal to obtain a frequency signal with respect to an electrical carrier wave signal output from the electrical oscillator, is input by Electrical digital signals m (m = 1,2, ..., M) can take number of values subjected to amplitude modulation or frequency modulation or phase modulation in the electrical amplitude modulation signal or electrical frequency modulated signal having a frequency of f _IF Alternatively, an electric modulator that outputs an electric phase modulation signal and a single side wave with an electric amplitude modulation signal, electric frequency modulation signal, or electric phase modulation signal from the electric modulator with respect to the optical signal output from the optical multiplexer. provide Reinforced strip light modulation, the f _c1 + f _IF and f _c2 + f _IF frequency, or a f _c1 -f _IF and f _c2 -f _IF of the optical single sideband modulator for outputting an optical signal having a frequency An optical transmitter characterized in that the optical transmitter is provided is used as a solution.

  According to the third aspect of the present invention, four optical signals can be transmitted from the optical transmitter, and the output of the light receiving element of the wireless base station is an amplitude modulated signal or a frequency modulated signal in the desired wireless signal frequency band. It is possible to obtain three-wave radio signals including the phase modulation signal and having different frequency intervals by the frequency of the intermediate frequency signal.

In the invention of claim 3, the electric field E _opt of the optical signal transmitted when _performing phase modulation by the electric modulator and single sideband optical modulation in which the upper sideband remains by the optical single sideband modulator is given by Can be expressed as:

E _opt = A cos {2π (f _c2 + f _IF ) t + φ _m + φ ₂ (t)}
+ Acos {2π (f _c2 ) t + φ ₂ (t)}
+ A cos {2π (f _c1 + f _IF ) t + φ _m + φ ₁ (t)}
+ Acos {2π (f _c1 ) t + φ ₁ (t)} (7)
Where A is the electric field amplitude, f _c1 and f _c2 are the optical frequencies of the first and second optical signals, f _IF is the intermediate frequency, and m is the M value (M is the nth power of 2 (n is a natural number)) , M value signal is an n-bit signal), input digital signals (m = 1, 2,..., M), φ ₁ (t), φ ₂ (t) are first and second single signals. It represents the phase noise of the spectrum light source, and φ _m satisfies φ = φ _{m + 1} −φ _m = 2π / M.

The electric field E _{RF of the} radio signal obtained by square detection of this optical signal with the light receiving element can be expressed as follows.

E _RF ∝A ² cos {2π (f _RF + f _IF ) t + φ _m + φ ₂ (t) −φ ₁ (t)}
+ 2A ² cos {2πf _RF t + φ ₂ (t) −φ ₁ (t)}
+ A ² cos {2π (f _RF −f _IF ) t−φ _m + φ ₂ (t) −φ ₁ (t)} (8)
Here, f _RF represents a radio signal frequency, and f _RF = f _c2 −f _c1 .

  At the wireless subscriber terminal, after receiving these high-frequency radio signal radio waves with an antenna, square detection is performed by a non-linear element such as a diode, and a low pass filter is used to prepare a local oscillator, that is, an electric oscillator in the radio signal frequency band. Without doing so, an electrical phase signal in a low frequency band can be obtained as the intermediate frequency signal.

The electric field E _IF of the intermediate frequency band signal can be expressed as:

E _IF ∝4A ⁴ cos (2πf _IF t + φ _m ) (9)
From the equation (9), the phase noise of the first and second single optical spectrum light sources is canceled during the square detection of electricity at the wireless subscriber terminal, and an intermediate frequency signal with high frequency stability can be obtained. I understand.
In the fourth to sixth aspects, the optical-wireless communication system including the optical transmitters according to the first to third aspects is used as the solving means, and the operation and effect are the same as those in the first to third aspects.

As described above, in the optical transmitter of the broadband optical-wireless communication system that transmits the optical signal to the wireless base station by the optical transmitter and the optical-wireless communication system of the present invention, the optical modulation of the frequency band of the wireless signal is performed. It is possible to obtain an intermediate frequency modulated signal with high frequency stability without preparing a device and without preparing a filter in the frequency band of the radio signal in the radio base station. Thereby, it becomes possible to make a wireless base station into an inexpensive and simple hardware configuration together with an optical transmitter.

<Embodiment 1>
The first embodiment of the present invention will be described with reference to the block diagrams of FIGS. 5, 6, and 7, and the spectrum diagrams of the electrical frequency and optical frequency in FIG.

  FIG. 5 is a block diagram showing the configuration of the optical transmitter 1 according to the first embodiment of the present invention, in which 2 is an input terminal for inputting an electric digital signal (1a) to be transmitted, 3 and 4 are first and The second single spectrum light source 5 is an optical multiplexer that combines the first and second output optical signals (1b, 1c) from the first single spectrum light source 3 and the second single spectrum light source 4. , 6 is the output light (1f) of the optical multiplexer 5 by the electric modulation signal (1f) obtained by amplitude-modulating or frequency-modulating the output signal (1e) from the electric oscillator 7 by the electric modulator 8 based on the input electric digital signal (1a). 1d) is an optical modulator that performs optical modulation on both sides of a carrier wave.

In this optical transmitter 1, the optical frequency (f _c1 ) of the output optical signal (1 b) from the first single spectrum light source 3 and the optical frequency of the output optical signal (1 c) from the second single spectrum light source 4. the difference between _{(f c2) (f c2 -f} c1) is set to be equal to the radio signal frequency such as a millimeter wave band (f _RF), the output signal from the electric generator 7 (1e) of the intermediate frequency signal frequency made to be an electrical carrier wave signal having half the frequency (f _IF / 2) of (f _IF). Further, the occupied frequency band (B) of the output electric modulation signal (1f) of the electric modulator 8 is made smaller than the frequency (f _IF ) of the intermediate frequency signal.

  The optical signal (1g) transmitted from the optical transmitter 1 as described above is received by the radio base station 9 shown in FIG.

  The radio base station 9 includes a light receiving element 10 that squarely detects an optical signal (1g) and converts it into an electric signal, and an antenna that transmits a millimeter wave band radio signal that is an output electric signal (1h) of the light receiving element 10 as a radio wave. 11.

In the optical transmitter 1, the optical frequency (f _c1 ) of the output optical signal (1b) from the first single spectrum light source 3 and the optical frequency (f 1) of the output optical signal (1c) from the second single spectrum light source 4 the difference between _{f c2) (f c2 -f c1} ) is set to be equal to the radio signal frequency such as a millimeter wave band (f _RF), further, the output signal from the electrical oscillator 8 (1e) of the intermediate frequency signals by such that the electric carrier signal having a frequency half the frequency of _{(f IF) (f IF /} 2), the radio base station 9, the frequency of the intermediate frequency signal frequency intervals, respectively by (f _IF) different Three millimeter-wave band radio signals (1h: f _RF + f _IF , f _RF , f _RF −f _IF ) can be obtained.

  FIG. 7 is a block diagram showing the configuration of the wireless subscriber terminal 12 according to the first embodiment of this invention. The millimeter-wave band radio signal (1h) transmitted from the radio base station 9 is received by the antenna 13 and then square-detected by a multiplier 14 using a non-linear element such as a mixer diode. By passing the signal (1i) through the low-pass filter 15, an intermediate frequency band electric modulation signal (1j) having high frequency stability can be obtained without preparing a millimeter wave band electric oscillator.

<Embodiment 2>
The second embodiment of the present invention will be described with reference to the block diagrams of FIGS. 9, 10, and 11 and the spectrum diagrams of the electrical frequency and the optical frequency in FIG.

  FIG. 9 is a block diagram showing the configuration of the optical transmitter 18 according to the second embodiment of the present invention. In FIG. 9, 19 is an input terminal for inputting an electric digital signal (2a) to be transmitted, 20 and 21 are first and second input terminals. An optical multiplexer 22, which combines the first and second output optical signals (2 b, 2 c) from the first single spectrum light source 20 and the second single spectrum light source 21. , 23 indicates the output light (2d) of the optical multiplexer 5 by the electric phase modulation signal (2f) obtained by phase-modulating the output signal (2e) from the electric oscillator 24 by the electric phase modulator 25 based on the input electric digital signal (2a). ) Is an optical modulator that performs optical modulation on both sides of the carrier wave.

In this optical transmitter 18, the optical frequency (f _c1 ) of the output optical signal (2 b) from the first single spectrum light source 20 and the optical frequency of the output optical signal (2 c) from the second single spectrum light source 21. the difference between _{(f c2) (f c2 -f} c1) is set to be equal to the radio signal frequency such as a millimeter wave band (f _RF), the output signal from the electric oscillator 24 (2e) of the intermediate frequency signal frequency made to be an electrical carrier wave signal having half the frequency (f _IF / 2) of (f _IF). Further, in the electrical phase modulator 25, an output electrical phase modulation signal for the electrical digital signal (m + 1) with respect to the electrical digital signal m (m = 1, 2,..., M) that can take M values. Phase modulation is performed so that the phase difference between the phase of (2f) and the phase of the output electrical phase modulation signal (2f) with respect to the electrical digital signal m is π / M, and the output electrical phase of the electrical phase modulator 25 The occupied frequency band (B) of the modulation signal (2f) is made smaller than the frequency (f _IF ) of the intermediate frequency signal.

  The optical signal (2g) transmitted from the optical transmitter 18 as described above is received by the radio base station 26 shown in FIG.

  The radio base station 26 squarely detects the optical signal (2g) and converts it into an electric signal, and an antenna that transmits a millimeter-wave band radio signal that is an output electric signal (2h) of the light receiving element 27 as a radio wave. 28.

In the optical transmitter 18, the optical frequency (f _c1 ) of the output optical signal (2 b) from the first single spectrum light source 20 and the optical frequency (2 _c ) of the output optical signal (2 c) from the second single spectrum light source 21. the difference between _{f c2) (f c2 -f c1} ) is set to be equal to the radio signal frequency such as a millimeter wave band (f _RF), further, the output signal from the electric oscillator 24 (2e) of the intermediate frequency signals by such that the electric carrier signal having a frequency half the frequency of _{(f IF) (f IF /} 2), the radio base station 26, the frequency of the intermediate frequency signal frequency intervals, respectively by (f _IF) different Three millimeter-wave band radio signals (2h: f _RF + f _IF , f _RF , f _RF −f _IF ) can be obtained.

  FIG. 11 is a block diagram showing a configuration of the wireless subscriber terminal 29 according to the second embodiment of this invention. The millimeter-wave band radio signal (2h) transmitted from the radio base station 26 is received by the antenna 30 and then square-detected by a multiplier 31 using a non-linear element such as a mixer diode. By passing the signal (2i) through the low-pass filter 32, it is possible to obtain an electric modulation signal (2j) in an intermediate frequency band with frequency stability without preparing a millimeter-wave electric oscillator.

  Also, in the present invention, in the optical transmitter, since the phase difference φ with respect to the M-value signal of the input electrical digital signal is modulated to be π / M, as an intermediate frequency band signal in the wireless subscriber terminal 29, A modulated signal (2j) can be obtained such that the phase difference φ ′ of the input electric digital signal with respect to the M-value signal is 2π / M, and the SN characteristic of detection is optimal.

<Embodiment 3>
The third embodiment of the present invention will be described with reference to the block diagrams of FIGS. 13, 14, and 15 and the spectrum diagrams of the electrical frequency and the optical frequency in FIG.

  FIG. 13 is a block diagram showing a configuration of an optical transmitter 35 according to the third embodiment of the present invention. 36 is an input terminal for inputting an electric digital signal (3a) to be transmitted, 37 and 38 are first and A second single spectrum light source 39 is an optical multiplexer for combining the first and second output optical signals (3b, 3c) from the first single spectrum light source 37 and the second single spectrum light source 38. , 40 is an output of the optical combiner 39 by an electric modulation signal (3f) obtained by amplitude-modulating, frequency-modulating or phase-modulating the output signal (3e) from the electric oscillator 41 by the electric modulator 42 based on the input electric digital signal (3a). This is an optical single sideband modulator that modulates output light (3d) with single sideband light.

In this optical transmitter 35, the optical frequency (f _c1 ) of the output optical signal (3 b) from the first single spectrum light source 37 and the optical frequency of the output optical signal (3 _c ) from the second single spectrum light source 38. the difference between _{(f c2) (f c2 -f} c1) is set to be equal to the radio signal frequency such as a millimeter wave band (f _RF), the output signal from the electric oscillator 41 (3e) of the intermediate frequency signal frequency The electric carrier wave signal has (f _IF ). Further, the occupied frequency band (B) of the output electric modulation signal (3f) of the electric modulator 42 is set to be smaller than twice the frequency (f _IF ) of the intermediate frequency signal.

  The optical signal (3g) transmitted from the optical transmitter 35 as described above is received by the radio base station 43 shown in FIG.

  The radio base station 43 squarely detects the optical signal (3g) and converts it into an electric signal, and an antenna that transmits a millimeter-wave band radio signal that is an output electric signal (3h) of the light receiving element 44 as a radio wave. 45.

In the optical transmitter 35, the optical frequency (f _c1 ) of the output optical signal (3b) from the first single-spectrum light source 37 and the optical frequency (3c) of the output optical signal (3c) from the second single-spectrum light source 38 the difference between _{f c2) (f c2 -f c1} ) is set to be equal to the radio signal frequency such as a millimeter wave band (f _RF), further, the output signal from the electric oscillator 41 (3e) of the intermediate frequency signals By making the electric carrier wave signal having the frequency (f _IF ), the radio base station 43 has three millimeter-wave band radio signals (3h) whose frequency intervals differ from each other by the frequency of the intermediate frequency signal (f _IF ). : F _RF + f _IF , f _RF , f _RF −f _IF ).

  FIG. 15 is a block diagram showing the configuration of the wireless subscriber terminal 46 according to the third embodiment of this invention. The millimeter-wave band radio signal (3h) transmitted from the radio base station 43 is received by the antenna 47, and then square-detected by a multiplier 48 using a non-linear element such as a mixer diode. By passing the signal (3i) through the low-pass filter 49, it is possible to obtain an intermediate frequency band electric modulation signal (3j) with high frequency stability without preparing a millimeter wave band electric oscillator.

Block configuration diagram showing an example of a conventional optical transmitter Block configuration diagram showing an example of a conventional radio base station Block configuration diagram showing an example of a conventional wireless subscriber terminal The figure which shows an example of the signal spectrum in the conventional optical-wireless fusion communication system The block block diagram which shows the optical transmitter which concerns on the 1st Embodiment of this invention The block block diagram which shows the radio base station which concerns on the 1st Embodiment of this invention The block block diagram which shows the radio | wireless subscriber terminal which concerns on the 1st Embodiment of this invention The figure which shows the signal spectrum in the 1st Embodiment of this invention The block block diagram which shows the optical transmitter which concerns on the 2nd Embodiment of this invention The block block diagram which shows the radio base station which concerns on the 2nd Embodiment of this invention The block block diagram which shows the wireless subscriber terminal which concerns on the 2nd Embodiment of this invention The figure which shows the signal spectrum in the 2nd Embodiment of this invention The block block diagram which shows the optical transmitter which concerns on the 3rd Embodiment of this invention The block block diagram which shows the radio base station which concerns on the 3rd Embodiment of this invention The block block diagram which shows the wireless subscriber terminal which concerns on the 3rd Embodiment of this invention The figure which shows the signal spectrum in the 3rd Embodiment of this invention

Explanation of symbols

  1, 18, 35: optical transmitters, 2, 19, 36: input terminals, 3, 4, 20, 21, 37, 38: single spectrum light sources, 5, 22, 39: optical multiplexers, 6, 23. Optical modulator, 40 ... optical single sideband modulator, 7, 24, 41 ... electric oscillator, 8, 42: electric modulator, 25 ... electric phase modulator, 9, 26, 43: radio base station, 10, 27, 44: light receiving element, 11, 13, 28, 30, 45, 47 ... antenna, 12, 29, 46: wireless subscriber terminal, 14, 31, 48 ... multiplier, 15, 32, 49: low-pass filter, 16, 33, 50: detectors, 17, 34, 51... Output terminals.

Claims (6)

In an optical transmitter that transmits a desired radio signal as an optical signal to a radio base station that squarely detects the received optical signal, converts it to an electric signal, and transmits the electric signal as a radio signal,
First and second single-spectrum light source difference in the respective center frequencies _{f c1, f c2 (f c2} -f c1) to generate an optical signal of a single spectrum is equal to the frequency f _RF of the radio signal,
An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources;
The radio base station receives the radio wave transmitted from square-law detection and of the intermediate frequency signal in the radio terminal to obtain an intermediate frequency signal by passing the low-pass filter frequency f _IF of half the frequency equal to (f _IF / 2) An electrical oscillator for generating an electrical carrier signal having;
The electric carrier wave signal output from the electric oscillator is subjected to amplitude modulation or frequency modulation with an electric digital signal m (m = 1, 2,..., M) that can take M values , and f _IF An electrical modulator that outputs an electrical amplitude modulated signal or electrical frequency modulated signal having a frequency of / 2 ,
To the optical signal output from the optical multiplexer, and facilities the double sideband suppressed carrier light modulated by the electrical amplitude modulation signal or electrical frequency modulated signal from the electric _{modulator, f c1 + f IF / 2} , f c1 An optical transmitter comprising: an optical modulator that outputs optical signals having frequencies of −f _IF / 2, f _c2 + f _IF / 2, and f _c2 −f _IF / 2 . In an optical transmitter that transmits a desired radio signal as an optical signal to a radio base station that squarely detects the received optical signal, converts it to an electric signal, and transmits the electric signal as a radio signal,
First and second single-spectrum light source difference in the respective center frequencies _{f c1, f c2 (f c2} -f c1) to generate an optical signal of a single spectrum is equal to the frequency f _RF of the radio signal,
An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources;
The radio base station receives the radio wave transmitted from square-law detection and of the intermediate frequency signal in the radio terminal to obtain an intermediate frequency signal by passing the low-pass filter frequency f _IF of half the frequency equal to (f _IF / 2) An electrical oscillator for generating an electrical carrier signal having;
The electric carrier wave signal output from the electric oscillator is subjected to phase modulation by an electric digital signal m (m = 1, 2,..., M) that can take M values, and an electric phase modulation signal is output. And a phase difference between the phase of the output electrical phase modulation signal with respect to the electrical digital signal (m + 1) and the phase of the output electrical phase modulation signal with respect to the electrical digital signal m is π / M. and facilities modulation, and an electrical phase modulator for outputting an electrical phase-modulated signal having a frequency of f _IF / 2,
To the optical signal output from the optical multiplexer, and facilities the double sideband suppressed carrier light modulated by the electric phase-modulated signal from the electric _{modulator, f c1 + f IF / 2} , f c1 -f IF / 2 , F _c2 + f _IF / 2, and f _c2 −f _IF / 2, and an optical modulator that outputs an optical signal having a frequency of f _c2 −f _IF / 2 . In an optical transmitter that transmits an optical signal for transmitting a desired radio signal to a radio base station that squarely detects the received optical signal, converts it to an electric signal, and transmits the electric signal as a radio signal.
First and second single-spectrum light source difference in the respective center frequencies _{f c1, f c2 (f c2} -f c1) to generate an optical signal of a single spectrum is equal to the frequency f _RF of the radio signal,
An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources;
Electrical generating an electrical carrier signal having a frequency equal to the frequency f _IF of the intermediate frequency signal in the radio terminal to obtain an intermediate frequency signal by passing the low-pass filter and square-law detection by receiving radio waves transmitted from the wireless base station An oscillator,
The electric carrier wave signal output from the electric oscillator is subjected to amplitude modulation, frequency modulation, or phase modulation by an electric digital signal m (m = 1, 2,..., M) that can take M values. , An electrical modulator that outputs an electrical amplitude modulation signal or electrical frequency modulation signal or electrical phase modulation signal having a frequency of f _IF ;
To the optical signal output from the optical multiplexer, and facilities the single sideband light modulated by the electrical amplitude modulation signal or electrical frequency modulated signal or electrical phase-modulated signal from the electric modulator, f _c1 + f _IF and An optical transmitter comprising: an optical single sideband modulator that outputs an optical signal having a frequency of f _c2 + f _IF or f _c1 −f _IF and f _c2 −f _IF . A radio base station that square-detects the received optical signal, converts it to an electrical signal, and transmits the electrical signal as a radio signal; and receives a radio wave transmitted from the radio base station, square-detects it, and passes it through a low-pass filter. In an optical-radio fusion communication system comprising: a wireless terminal that obtains an intermediate frequency signal; and an optical transmitter that transmits a desired wireless signal to the wireless base station as an optical signal.
The optical transmitter is
Each center frequency f _c1 , F _c2 Difference (f _c2 -F _c1 ) Is the frequency f of the radio signal _RF First and second single spectrum light sources generating a single spectrum optical signal equal to
An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources;
The frequency f of the intermediate frequency signal in the wireless terminal _IF Equal to half the frequency (f _IF / 2) an electric oscillator for generating an electric carrier signal having
The electric carrier wave signal output from the electric oscillator is subjected to amplitude modulation or frequency modulation by an electric digital signal m (m = 1, 2,..., M) that can take M values, and f _IF An electrical modulator that outputs an electrical amplitude modulated signal or electrical frequency modulated signal having a frequency of / 2,
The optical signal output from the optical multiplexer is subjected to carrier-suppressed double-sideband optical modulation with an electric amplitude modulation signal or an electric frequency modulation signal from an electric modulator, and f _c1 + F _IF / 2, f _c1 -F _IF / 2, f _c2 + F _IF / 2 and f _c2 -F _IF An optical modulator that outputs an optical signal having a frequency of / 2.
The radio base station is
F sent from the optical transmitter _c1 + F _IF / 2, f _c1 -F _IF / 2, f _c2 + F _IF / 2 and f _c2 -F _IF Receiving an optical signal having a frequency of / 2 and square detection, f _RF , F _RF + F _IF And f _RF -F _IF Is converted into an electrical signal having a frequency of, and the electrical signal is transmitted as a radio signal,
The wireless terminal is
F transmitted from the radio base station _RF , F _RF + F _IF And f _RF -F _IF Receive a radio wave having a frequency of _IF 2f _IF 2f _RF 2f _RF + F _IF And 2f _RF -F _IF Is converted into an electric signal having a frequency of f and passed through a low-pass filter. _IF To obtain an intermediate frequency signal having a frequency of
An optical-radio fusion communication system. A radio base station that square-detects the received optical signal, converts it to an electrical signal, and transmits the electrical signal as a radio signal; and receives a radio wave transmitted from the radio base station, square-detects it, and passes it through a low-pass filter. In an optical-radio fusion communication system comprising: a wireless terminal that obtains an intermediate frequency signal; and an optical transmitter that transmits a desired wireless signal to the wireless base station as an optical signal.
The optical transmitter is
Each center frequency f _c1 , F _c2 Difference (f _c2 -F _c1 ) Is the frequency f of the radio signal _RF First and second single spectrum light sources generating a single spectrum optical signal equal to
An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources;
The frequency f of the intermediate frequency signal in the wireless terminal _IF Equal to half the frequency (f _IF / 2) an electric oscillator for generating an electric carrier signal having
The electric carrier wave signal output from the electric oscillator is subjected to phase modulation by an electric digital signal m (m = 1, 2,..., M) that can take M values, and an electric phase modulation signal is output. And a phase difference between the phase of the output electrical phase modulation signal with respect to the electrical digital signal (m + 1) and the phase of the output electrical phase modulation signal with respect to the electrical digital signal m is π / M. Modulation, f _IF An electrical phase modulator that outputs an electrical phase modulation signal having a frequency of / 2,
The optical signal output from the optical multiplexer is subjected to carrier-suppressed double-sideband optical modulation with an electric phase modulation signal from the electric modulator, and f _c1 + F _IF / 2, f _c1 -F _IF / 2, f _c2 + F _IF / 2 and f _c2 -F _IF An optical modulator that outputs an optical signal having a frequency of / 2.
The radio base station is
F sent from the optical transmitter _c1 + F _IF / 2, f _c1 -F _IF / 2, f _c2 + F _IF / 2 and f _c2 -F _IF Receiving an optical signal having a frequency of / 2 and square detection, f _RF , F _RF + F _IF And f _RF -F _IF Is converted into an electrical signal having a frequency of, and the electrical signal is transmitted as a radio signal,
The wireless terminal is
F transmitted from the radio base station _RF , F _RF + F _IF And f _RF -F _IF Receive a radio wave having a frequency of _IF 2f _IF 2f _RF 2f _RF + F _IF And 2f _RF -F _IF Is converted to an electric signal having a frequency of f and passed through a low-pass filter. _IF To obtain an intermediate frequency signal having a frequency of
An optical-wireless communication system characterized by the above. A radio base station that square-detects the received optical signal, converts it to an electrical signal, and transmits the electrical signal as a radio signal; and receives a radio wave transmitted from the radio base station, square-detects it, and passes it through a low-pass filter. In an optical-radio fusion communication system comprising: a wireless terminal that obtains an intermediate frequency signal; and an optical transmitter that transmits a desired wireless signal to the wireless base station as an optical signal.
The optical transmitter is
Each center frequency f _c1 , F _c2 Difference (f _c2 -F _c1 ) Is the frequency f of the radio signal _RF First and second single spectrum light sources generating a single spectrum optical signal equal to
An optical multiplexer that combines the first and second optical signals output from the first and second single spectrum light sources;
The frequency f of the intermediate frequency signal in the wireless terminal _IF An electrical oscillator that generates an electrical carrier signal having a frequency equal to
The electric carrier wave signal output from the electric oscillator is subjected to amplitude modulation, frequency modulation, or phase modulation by an electric digital signal m (m = 1, 2,..., M) that can take M values. , F _IF An electrical modulator that outputs an electrical amplitude modulation signal or electrical frequency modulation signal or electrical phase modulation signal having a frequency of
The optical signal output from the optical multiplexer is subjected to single sideband optical modulation with an electric amplitude modulation signal, electric frequency modulation signal, or electric phase modulation signal from an electric modulator, and f _c1 + F _IF And f _c2 + F _IF Frequency, or f _c1 -F _IF And f _c2 -F _IF An optical single sideband modulator that outputs an optical signal having a frequency of
The radio base station is
F sent from the optical transmitter _c1 + F _IF And f _c2 + F _IF Frequency, or f _c1 -F _IF And f _c2 -F _IF And squarely detect an optical signal having a frequency of f and f _RF , F _RF + F _IF And f _RF -F _IF Is converted into an electrical signal having a frequency of, and the electrical signal is transmitted as a radio signal,
The wireless terminal is
F transmitted from the radio base station _RF , F _RF + F _IF And f _RF -F _IF Receive a radio wave having a frequency of _IF 2f _IF 2f _RF 2f _RF + F _IF And 2f _RF -F _IF Is converted to an electric signal having a frequency of f and passed through a low-pass filter. _IF To obtain an intermediate frequency signal having a frequency of
An optical-wireless communication system characterized by the above.

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