JP3218325B2 - Millimeter-wave wireless / optical fiber transmission system and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber transmission technique in wireless communication and the like.

[0002]

2. Description of the Related Art A conventional millimeter-wave wireless communication system is supposed to receive a millimeter-wave wireless signal from a wireless terminal at an antenna base station and transmit the signal to a control station via an optical fiber transmission line.
FIG. 4 shows a configuration diagram of the optical fiber transmission system, divided by the frequency of the radio signal subcarrier on the optical fiber transmission line. In FIG. 4, reference numeral 31 denotes a millimeter-wave wireless terminal, 32 denotes a millimeter-wave antenna, 33 denotes a millimeter-wave band signal demodulator, 34 denotes an optical modulator, 35 denotes an optical fiber transmission line, and 36 denotes an optical detector. , 37 denotes a sub-carrier frequency converter, and 38 denotes an intermediate frequency band signal demodulator.

FIG. 4A is a configuration diagram showing a baseband transmission system, in which a millimeter-wave radio signal from a millimeter-wave radio terminal 31 is received by a millimeter-wave antenna 32, and the radio signal is transmitted to an antenna base station. The optical carrier is demodulated by the millimeter-wave band signal demodulator 33, the optical carrier is modulated by the baseband data reproduced by the optical modulator 34, and the optical signal transmitted through the optical fiber transmission line 35 is optically detected by the optical detector 36. By doing so, the information of the original radio signal is transmitted.

FIG. 4B is a block diagram showing an intermediate frequency band sub-carrier transmission system. A millimeter wave radio signal from a millimeter wave radio terminal 31 is received by a millimeter wave antenna 32, and the radio signal is transmitted to the antenna. The radio signal frequency converter 37 of the base station down-converts the signal into a microwave intermediate frequency band, modulates the optical carrier with the intermediate frequency band signal obtained in the optical modulator 34, and transmits the light transmitted through the optical fiber transmission line 35. The signal is optically detected by the optical detector 36, and the reproduced intermediate frequency band signal is decoded by the intermediate frequency band signal demodulator 38.
By performing the tuning, the information of the original wireless signal is transmitted.

FIG. 4C is a configuration diagram showing a millimeter wave band subcarrier radio signal transmission system. A millimeter wave radio signal from a millimeter wave radio terminal 31 is received by a millimeter wave antenna 32 and optical modulation is performed. The optical carrier is directly modulated by the millimeter-wave radio signal received by the detector 34, and the optical signal transmitted through the optical fiber transmission line 35 is optically detected by the optical detector 36 to convert the reproduced millimeter-wave band signal into the millimeter-wave band. By performing demodulation by the signal demodulator 33, information of the original radio signal is transmitted.

[0006]

However, among the conventional techniques, in the systems shown in FIGS. 4A and 4B, the influence of the dispersion provided in the optical fiber transmission line can be ignored, but the antenna The problem of increased costs due to the complexity of the base station is a problem, which greatly limits commercial deployment.

[0007] Among the conventional techniques, in the system shown in FIG. 4 (c), the base station is very simple and advantageous from the viewpoint of cost, but is affected by the dispersion of the optical fiber. From the viewpoint of practical use, it is necessary to reduce the influence of the dispersion of the optical fiber and to reduce the cost burden.

[0008] The present invention is an antenna base station without an increase in convenience and cost, and commercial deployment in rather <br/> such being restricted, further influenced by the dispersion which the optical fiber comprises
Providing a free millimeter-wave radio, optical fiber transmission system and apparatus are aimed.

[0009]

Means for Solving the Problems The present invention has been made in view of the above problems, feeding millimeter-wave radio, optical fiber Den
In scheme an optical carrier fc from a single-mode light source,
Carrier frequency f _{RF of} millimeter-wave wireless sub-carrier signal to be transmitted
Desired intermediate frequency below the lower microwave band
Frequency conversion up to the carrier frequency f _IF of the band signal (f _RF −
f _IF ) , the intensity of which is modulated with a sine wave signal having a frequency f _LO corresponding to the frequency f _LO . As a result, the generated pilot light is further intensity-modulated with the millimeter wave radio subcarrier signal, and the original millimeter wave A first component of one of a plurality of optical spectra having the same information f _RF as the radio sub-carrier signal
(Fc−f _RF ) and its first component (fc−f _RF )
At the difference of the carrier frequency f _IF of the desired intermediate frequency band signal.
After transmitting the contacting second component f _PL with the optical fiber,
By optical self-heterodyne detection, the first component (fc-
f _RF) and frequency difference between the second component _{f PL (f PL - (fc} -f
Converted into an intermediate frequency band signal having a frequency f _IF corresponding to _RF))), by demodulating the frequency band signals between intermediate is characterized by reproducing the information of the original millimeter-wave wireless subcarrier signals .

Further, the present invention relates to a millimeter-wave radio / optical fiber.
In a transmission device, a single-mode light source for generating a single-frequency optical carrier and a millimeter-wave wireless subcarrier signal to be transmitted.
And the millimeter wave local oscillator for generating a sine wave of a frequency corresponding to the frequency conversion amount to the carrier frequency of the desired intermediate frequency band signal lower than the microwave band following it from the carrier frequency, intensity modulation of the optical carrier by the sine wave Pilot light
A pilot light generation optical modulator for generating a millimeter wave antenna for receiving millimeter wave radio subcarrier signal, the light space by intensity modulating the pilot light in the millimeter wave <br/> radio subcarrier signals
A radio signal modulation optical modulator to obtain a vector, the optical scan
The spectrum is one of a plurality of optical spectra having the same information as the original millimeter-wave wireless subcarrier signal .
One component and a desired intermediate frequency band signal for the first component
An optical filter for extracting an adjacent second component with a difference in carrier frequency of the signal, an optical transmission line for transmitting the first component and the second component, and a transmitted first component and a second component . Optical self-heterodyne detection and the frequency corresponding to the frequency difference between the two
A photodetector for converting the intermediate frequency band signal having a wave number, original millimeter-wave wireless sub from the intermediate frequency band signal obtained by the optical detection
It was composed of a intermediate frequency band signal demodulator for reproducing information of the carrier signal, and wherein the kite.

With the optical subcarrier frequency conversion function included in the present invention, the antenna base station has a simpler configuration,
The influence of the dispersion of the optical fiber can be ignored, and the control station does not need an ultrahigh-frequency optical detector or a millimeter-wave band mixer.

[0012] The present invention is specifically, of the light spectrum obtained upon intensity modulation certain one of the optical carrier in the millimeter-wave radio sub-carrier signals, comprises the same information as the original millimeter wave radio subcarrier signals One of multiple optical spectra
(First component) and a desired intermediate frequency for the first component
Another unmodulated lightwave (second component) of different frequency and in-phase noise adjacent to the difference in carrier frequency of several band signals is transmitted on the optical fiber transmission line, optical self-heterodyne detection is performed, and the transmitted optical signal is transmitted. An optical detection signal having a frequency corresponding to the frequency difference between the first component and the second component , that is, an intermediate frequency band signal is demodulated.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific configuration of an embodiment according to the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment. FIG. 1 is a diagram showing a configuration of a millimeter wave wireless / optical fiber transmission device according to an embodiment of the present invention. In FIG. 1, reference numeral 9 denotes a control station;
0 is an antenna base station, 11 is a millimeter wave wireless terminal, 12
Is a single mode light source, 13 is a millimeter wave local oscillator, 14
Is an optical modulator for generating pilot light, 15 is an optical amplifier, 16 is an optical transmission line, 17 is a polarization controller, 18 is an optical modulator for radio signal modulation, and 19 is a millimeter-wave radio signal generation. , A millimeter wave antenna, 21 a millimeter wave band amplifier, 22 an optical bandpass filter, 23 an optical detector,
24 is an intermediate frequency band signal processing unit (intermediate frequency band signal demodulation
The vessel), 25 a spectrum of the millimeter wave local oscillator output,
26 indicates the optical spectrum of the pilot light, 27 indicates the spectrum of the millimeter-wave wireless subcarrier signal, 28 indicates the optical spectrum of the uplink modulation signal, and 29 indicates the spectrum of the optical detection signal. This device basically includes a control station 9, an antenna base station 10, a millimeter-wave wireless terminal 11, and an optical fiber transmission line 16.

First, in the control station 9, the optical carrier (fc) from the single mode light source 12 is transmitted to the millimeter-wave local oscillator 13.
The pilot light 26 is intensity-modulated by a pilot light generation optical modulator 14 with a sine wave output 25 (f _LO ) from the
After sufficient amplification at 5, the signal is transmitted to the antenna base station 10 through one optical transmission line 16. Transmitted pilot light 2
The signal 6 is amplified by another optical amplifier 15 until the required power is reached, and the polarization is adjusted by the polarization controller 17 and then input to the optical modulator 18 for modulating a radio signal.

On the other hand, in the wireless terminal 11, the information (DATA) to be transmitted is
It converts it into a millimeter wave radio signal (f _RF ) 27 of the SK modulation format,
The millimeter wave radio signal is radiated from the millimeter wave antenna 20 on the wireless terminal side to the antenna base station 10.

The millimeter wave radio signal 27 propagated through the free space is received by the millimeter wave antenna 20 on the antenna base station side, and the millimeter wave radio signal 27 is amplified by the millimeter wave band amplifier 21 until the required power is reached. The pilot signal 26 is intensity-modulated in the optical modulator 18 for radio signal modulation,
As a result, an uplink modulated signal 28 is obtained.

The uplink modulated signal 28 is amplified by another optical amplifier 15 and then the optical bandpass filter 22 _extracts only the minimum optical spectrum ( _fpL and fc-f _RF ) necessary for transmission, and then extracts it. The light is transmitted to the control station 9 through another optical transmission line 16. Here, the frequency difference between the two transmitted light waves (the first component (fc-f _RF ) and the second component f _PL ) must always match the desired frequency f _IF after optical detection.

Next, the two transmitted light waves ( _fpL and fc-f
_RF ) is subjected to optical self-heterodyne detection by the optical detector 23 in a band capable of sufficiently detecting the optical frequency difference, thereby obtaining an intermediate frequency band signal 29 ( _fIF ). Finally, the intermediate frequency band signal 29 obtained by the optical detection is subjected to DPSK demodulation in the intermediate frequency band signal processing unit 24, whereby the original information is reproduced. Here, the pilot light 26 may be generated by another method as long as it has the same phase noise and includes at least two light waves at different frequencies. For example, among the light waves output from the other wavelength light source such as a mode-locked laser by using light waves corresponding to f _pL as the reference light, may be used light wave corresponding to fc for information transmission of the millimeter-wave radio signals . At this time, the optical modulation method can be an optical analog modulation method capable of subcarrier transmission, that is, any one of intensity modulation, amplitude modulation, phase modulation, and frequency modulation.

The light wave corresponding to f _pL is a modulation component (f
c-f _RF ) may be transmitted separately, or may not be transmitted to the antenna base station 10 and may be transmitted to the control station 9 within the modulation component (f
c-f _RF ) may be combined with the optical detection, and the arrangement of each spectrum of the light source or the pilot light is not limited to either the control station or the antenna base station.

Since the optical amplifier 15 and the millimeter-wave band amplifier 21 are used for obtaining required power, they can be omitted if there is sufficient power before the amplifier.
Since the polarization controller 17 and is used to increase the modulation efficiency for the polarization dependence of the radio signal modulation optical modulator 18, or the optical transmission line is of polarization-maintaining or optical If the polarization dependence of the modulator is very low,
The polarization controller 17 can be omitted.

The millimeter wave radio signal is arbitrary, and there is no need to limit analog signals and digital signals, single signals and multiplexed signals, transmission speed, modulation format, and the like.

FIG. 2 shows an optical spectrum measured in the present embodiment. FIG. 2 (a) shows pilot light, and FIG. 2 (b) shows light before transmission of an optical fiber and a standard optical fiber. 5 shows an optical uplink signal after transmission of 50 km .

FIG. 3 shows that in this embodiment, a 59.6 GHz DPSK millimeter wave radio signal having a transmission rate of 155.52 Mb / s and received by an antenna base station 50 km away is transmitted through a standard optical fiber transmission line. Next, the result of measuring the bit error rate as one of the transmission qualities when the information is reproduced on the control station side. From the results in FIG. 3, it can be seen that almost the same characteristics are obtained as compared to the case where the measurement is performed with the optical fiber 50 km removed.

[0024]

According to the present invention, since the millimeter wave signal is directly taken into the pilot light, the configuration of the antenna base station can be simplified, the cost of the base station can be greatly improved, and the antenna can be used outdoors. Considering the case where it is placed,
It is more practical in terms of maintenance, management, and reliability, and thus can greatly contribute to commercial deployment. Further, since the frequency is converted from the millimeter wave radio signal band to the microwave intermediate frequency band in the optical domain, no component of the electrical millimeter wave down converter is required in the entire configuration. Furthermore,
By arranging the light source on the control station side, the stability and reliability of the light source can be improved, and the wavelength of the light can be easily changed, so that the network can be easily constructed. Furthermore, since the transmitted signal corresponds to the subcarrier transmission equivalent to the intermediate frequency band, it is not necessary to consider the influence of the dispersion provided in the optical fiber.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of a millimeter wave wireless / optical fiber transmission device according to the present invention.

FIG. 2 is a characteristic diagram showing an optical spectrum in the present invention.

FIG. 3 is a characteristic diagram showing a bit error rate in the present invention.

FIG. 4 is a configuration diagram showing a classification of a conventional optical signal transmission system.

[Explanation of symbols]

Reference Signs List 9 control station 10 antenna base station 11 millimeter-wave wireless terminal 12 single-mode light source 13 millimeter-wave local oscillator 14 optical modulator for pilot light generation 15 optical amplifier 16 optical transmission line 17 polarization controller 18 optical modulation for radio signal modulation 19 millimeter-wave radio signal generation unit 20 millimeter-wave antenna 21 millimeter-wave band amplifier 22 optical band-pass filter 23 optical detector 24 intermediate frequency band signal processing unit (intermediate frequency band signal recovery unit)
25 ) Spectrum of millimeter-wave local oscillator output 26 Optical spectrum of pilot light 27 Spectrum of millimeter-wave wireless subcarrier signal 28 Optical spectrum of uplink modulation signal 29 Spectrum of photodetection signal 31 Millimeter-wave wireless terminal 32 Millimeter-wave antenna 33 Millimeter-wave band signal demodulator 34 Optical modulator 35 Optical transmission line 36 Optical detector 37 Wireless signal frequency converter 38 Intermediate frequency band signal demodulator

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H04B 10/18 H04Q 7/36 (56) References JP-A-9-321700 (JP, A) JP-A 10-32563 (JP) , A) JP-A-2000-19470 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 H04B 7/26

Claims (2)

(57) [Claims] An optical carrier from a single mode light source is transmitted.
From the carrier frequency of the millimeter-wave wireless subcarrier signal to be
Of the desired intermediate frequency band signal below the lower microwave band
The intensity is modulated with a sine wave signal having a frequency corresponding to the amount of frequency conversion up to the carrier frequency, and as a result, of the optical spectrum obtained by further intensity modulating the generated pilot light with the millimeter-wave wireless sub-carrier signal, One of a plurality of optical spectra having the same information as the millimeter-wave wireless subcarrier signal
A certain first component and a desired intermediate frequency for the first component;
After transmitting the second component adjacent to the carrier signal having a difference in the carrier frequency of the several band signal through an optical fiber , the frequency corresponding to the frequency difference between the first component and the second component is detected by optical self-heterodyne detection. converted into an intermediate frequency band signal having a by demodulating the frequency band signals between intermediate, original millimeter-wave wireless Fuku搬
A millimeter-wave wireless / optical fiber transmission system for reproducing information of a transmission signal. 2. A single-mode light source for generating a single-frequency optical carrier and a carrier frequency of a millimeter-wave wireless sub-carrier signal to be transmitted.
The desired intermediate frequency band below the lower microwave band
Generating a millimeter wave local oscillator for generating a sine wave of a frequency, an intensity-modulated by a pilot light optical carrier by the sine wave corresponding to the frequency conversion amount to the carrier frequency of the No.
A pilot light generation optical modulator which, and the millimeter-wave antenna for receiving millimeter wave radio subcarrier signal, and intensity modulating the pilot light in the millimeter-wave wireless subcarrier signals
An optical modulator for modulating a radio signal for obtaining an optical spectrum, and an original millimeter-wave radio subcarrier signal of the optical spectrum;
One of multiple optical spectra with the same information as
And a desired intermediate circumference for the first component
Second components adjacent to each other with a difference in carrier frequency of a waveband signal
An optical filter for extracting the bets, corresponding to frequency difference between both of the first component and the optical transmission path for transmitting a second component, the first component and the optical self-heterodyne detection shiso and a second component which is transmitted Intermediate with frequency
An optical detector that converts the signal to a frequency band signal, and the original millimeter-wave radio signal from the intermediate frequency band signal obtained by optical detection
An intermediate frequency band signal demodulator for reproducing information subcarrier signals, configured to millimeter-wave wireless, optical fiber transmission and wherein the kite from.