JP2975457B2 - Optical transmission system for wireless link - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a case where a main base station which modulates and demodulates a baseband signal and a slave base station provided with a transmission / reception device for transmitting / receiving a terminal station via a radio line are separated. The present invention relates to an optical transmission system for a wireless link for transmitting a signal to be transmitted / received via the wireless line (hereinafter, referred to as a signal for a wireless link) using an optical fiber cable, and particularly to an automobile telephone system and a personal communication system The present invention relates to an optical transmission system for a wireless link applicable to a mobile communication system such as the above.

[0002]

2. Description of the Related Art In a conventional mobile communication system, a base station performs a signal processing of a baseband signal, so that the configuration of the base station becomes complicated and large, and a small radius of a zone requiring a large number of base stations is required. It has become difficult to install base stations in each of the cell zone or pico cell zone. In order to solve this problem, the slave base station covering the micro cell zone or the pico cell zone is not provided with a signal processing device for a baseband signal, but is provided with only a transmission / reception device for only analog signal processing related to wireless communication, and Simplification has been proposed.

Specifically, for example, after modulating a carrier with a multiplexed signal obtained by multiplexing a baseband signal in a main base station, the modulated signal is transmitted via a wireless line or a wired line using a coaxial cable. Transmit to the slave base station. Then, the slave base station frequency-converts the received modulated signal into a radio signal, transmits the radio signal to the mobile terminal station, and performs radio communication.

[0004]

However, in this conventional system, when a main base station and a sub base station are connected via a radio line, a large number of connections are made between the main base station and a plurality of sub base stations. Since it is necessary to set up a wireless line, it is difficult to effectively use radio waves, and the wireless lines connecting the main base station and the slave base station, as well as the wireless line, the slave base station, and the mobile terminal station, There is a problem that it is necessary to avoid the problem of radio wave interference with the wireless line connecting the.

In the above-mentioned conventional system, when the main base station and the subordinate base station are connected via a wired line using a coaxial cable, there is an upper limit in the carrier frequency due to the line loss of the coaxial cable. And the distance between the master base station and the slave base station is limited.

An object of the present invention is to solve the above problems, to have a simpler structure than the conventional example, and to connect a main base station and a subordinate base station without using a radio line and to transmit a radio link signal. An object of the present invention is to provide an optical transmission system for a wireless link capable of transmitting.

[0007]

According to the first aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a radio link, comprising: an optical transmission line connecting the master base station and the slave base station, wherein the master base station converts a carrier signal having a predetermined frequency into an information signal to be input. A modulating unit that modulates the modulated signal to output a modulated signal, a signal generating unit that generates a local oscillation signal having a predetermined frequency, and a modulated signal that has a non-linear electrical / optical conversion characteristic and is output from the modulating unit The local oscillation signal generated by the signal generating means is mixed with the modulation signal and the local oscillation signal by using the non-linear electrical / optical conversion characteristics, and at least the local oscillation signal is interposed between the modulation signal and the local oscillation signal. One blend Electrical-optical conversion means for performing electrical-optical conversion so as to generate a frequency component signal and outputting an optical signal including the mixed frequency component signal to the optical transmission line, wherein the slave base station comprises An optical-to-electrical conversion unit that optically / electrically converts an optical signal transmitted from the optical conversion unit via the optical transmission line and outputs an electric signal including a signal of the mixed frequency component; and Filtering means for band-filtering a signal of a predetermined mixed frequency component of the output electric signal, and transmission for wirelessly transmitting the signal of the predetermined mixed frequency component filtered by the filtering means Means.

According to a second aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; And an optical transmission line for connecting the slave base station and the slave base station, wherein the slave base station transmits a predetermined radio frequency modulated by an information signal and wirelessly transmitted by a partner station. Receiving means for receiving a transmission signal by radio and outputting a reception signal; signal generation means for generating a local oscillation signal having a predetermined frequency;
Having a light conversion characteristic, the reception signal output from the reception means and the local oscillation signal generated by the signal generation means, the reception signal and the local oscillation signal using the non-linear electrical-optical conversion characteristics And converting the received signal and the local oscillation signal into electrical and optical signals so that a signal of at least one mixed frequency component is generated. And an electric / optical conversion means for outputting.
An optical-to-electrical conversion unit that optically / electrically converts an optical signal transmitted from the optical conversion unit via the optical transmission line and outputs an electric signal including a signal of the mixed frequency component; and A filtering means for band-filtering a signal of a predetermined mixed frequency component among the output electric signals, and demodulating the signal of the mixed frequency component filtered by the filtering means to output the information signal And a demodulating means for performing the demodulation.

Further, according to a third aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; And a first and a second optical transmission line connecting the slave base station and the slave base station, wherein the master base station receives a carrier signal having a predetermined frequency. A modulating means for modulating with the first information signal and outputting a modulated signal; a first signal generating means for generating a first local oscillation signal having a predetermined frequency; and a non-linear electrical-optical conversion characteristic , A modulation signal output from the modulation means and a first signal generated by the first signal generation means.
The modulated signal and the first local oscillation signal by using the non-linear electrical-optical conversion characteristic, and mixing at least one signal between the modulated signal and the first local oscillation signal. First electrical-optical conversion means for performing electrical-optical conversion so as to generate two mixed frequency component signals and outputting a first optical signal including the mixed frequency component signal to the first optical transmission line; Wherein the slave base station comprises:
A first optical-to-electrical conversion unit for performing optical-to-electrical conversion of a first optical signal transmitted from the optical conversion unit via the first optical transmission line and outputting an electrical signal including a signal of the mixed frequency component; And first filtering means for band-filtering a signal of a predetermined first mixed frequency component of the electric signal output from the first optical-to-electrical conversion means, and the first filtering means Transmitting means for wirelessly transmitting the signal of the first mixed frequency component filtered by the means, and wirelessly receiving a transmission signal having a predetermined radio frequency which is wirelessly transmitted by being modulated by the second information signal at a partner station. Receiving means for outputting a received signal, a second signal generating means for generating a second local oscillation signal having a predetermined frequency, and a non-linear electrical-optical conversion characteristic, which is output from the receiving means. Received signal and the second
The second local oscillation signal generated by the signal generation means is mixed with the reception signal and the second local oscillation signal by using the non-linear electric / optical conversion characteristics, and the reception signal and the second local oscillation signal are mixed. And converting the second optical signal including the signal of the mixed frequency component into the second optical signal so as to generate a signal of at least one mixed frequency component with the local oscillation signal of the second optical signal.
A second electrical-optical conversion means for outputting to the optical transmission line of the first base station, and the main base station further includes a second electrical-optical conversion means for transmitting the second electrical-optical conversion means via the second optical transmission line. A second optical-to-electrical conversion unit that performs optical-to-electrical conversion on the second optical signal and outputs an electrical signal including the signal of the mixed frequency component, and an electrical signal output from the second optical-to-electrical conversion unit A second filtering means for band-pass filtering a signal of a predetermined second mixed frequency component, and demodulating the signal of the second mixed frequency component filtered by the second filtering means. And demodulating means for outputting the second information signal.

Further, the optical transmission system for a wireless link according to a fourth aspect of the present invention is the optical transmission system for a wireless link according to the third aspect, wherein the first and second optical signals are wavelength-multiplexed to form one optical signal. The transmission is performed via a transmission line.

According to a fifth aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a radio link, comprising: an optical transmission line for connecting to a slave base station; wherein the master base station modulates a carrier signal having a predetermined frequency with an input information signal, and And a signal generating means for generating a local oscillation signal having a predetermined frequency, and having a non-linear electrical / optical conversion characteristic, and in response to the local oscillation signal generated by the signal generating means, At least one harmonic signal of the local oscillation signal is generated using the non-linear electrical / optical conversion characteristics, and the modulated signal output from the modulating means and the generated harmonic signal are combined with the non-linear electric signal. Using a light conversion characteristic to mix the modulated signal and the generated harmonic signal so as to generate at least one mixed frequency component signal between the modulated signal and the generated harmonic signal; An optical-to-optical converter for optically converting and outputting an optical signal containing the signal of the mixed frequency component to the optical transmission line, wherein the slave base station transmits the optical transmission line from the electrical-optical converter Optical-to-electrical conversion means for converting an optical signal transmitted through the optical-to-electrical signal to output an electrical signal including the signal of the mixed frequency component, and a predetermined one of the electrical signals output from the optical-to-electrical conversion means And a transmitting means for wirelessly transmitting the signal of the mixed frequency component filtered by the filtering means.

According to a sixth aspect of the present invention, there is provided an optical transmission system for a radio link, comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; An optical transmission system for a wireless link, comprising first and second optical transmission lines for connecting the wireless base station and the slave base station,
The main base station, a carrier signal having a predetermined frequency,
A modulating means for modulating with an input first information signal to output a modulated signal; a signal generating means for generating a local oscillation signal having a predetermined frequency; Generating at least one harmonic signal of the local oscillation signal using the non-linear electrical / optical conversion characteristic in response to the local oscillation signal generated by the generation means; and a modulation signal output from the modulation means. The generated harmonic signal is mixed with the modulated signal and the generated harmonic signal by using the non-linear electric / optical conversion characteristic, and the modulated signal is mixed with the generated harmonic signal. The first optical signal including the generated harmonic signal and the signal of the mixed frequency component is subjected to the electro-optical conversion so that a signal of the at least one mixed frequency component is generated.
First optical-to-optical conversion means for outputting to the optical transmission line, and the slave base station transmits the first electric-to-optical signal from the first electric-to-optical conversion means via the first optical transmission line. Optical-to-electrical conversion means for optical-to-electrical conversion of the optical signal to output an electrical signal including the generated harmonic signal and the signal of the mixed frequency component; and the first optical-to-electrical conversion means First filtering means for band-pass filtering a signal of one predetermined mixed frequency component among the electric signals output from the first and second optical signals, A second filtering means for band-filtering the determined one harmonic signal, a transmitting means for wirelessly transmitting the mixed frequency component signal filtered by the first filtering means, A predetermined radio frequency modulated by the second information signal and transmitted wirelessly Receiving means for wirelessly receiving a transmission signal having the same and outputting a reception signal; and having a non-linear electrical-optical conversion characteristic, and a reception signal output from the reception means and filtered by the second filtering means. The above harmonic signal is
The reception signal and the filtered harmonic signal are mixed using the non-linear electrical-optical conversion characteristic, and at least one mixed frequency component between the reception signal and the filtered harmonic signal is mixed. A second electrical-optical conversion means for performing electrical-optical conversion to generate a signal and outputting a second optical signal including the signal of the mixed frequency component to the second optical transmission line; The station further optically / electrically converts the second optical signal transmitted from the second electric / optical conversion means via the second optical transmission line, and outputs an electric signal including the mixed frequency component signal. A second optical-to-electrical converting means for outputting, and a third filter for band-pass filtering a signal of a second predetermined mixed frequency component among the electric signals outputted from the second optical-to-electrical converting means. Wave means, and the second filter filtered by the third filter means. The signals of the mixed frequency components by demodulating and further comprising a demodulating means for outputting said second information signal.

The optical transmission system for a wireless link according to a seventh aspect of the present invention is the optical transmission system for a wireless link according to the sixth aspect, wherein the first and second optical signals are wavelength-multiplexed to form one optical transmission. It is characterized by being transmitted via a line.

[0014]

In the optical transmission system for a wireless link according to the first aspect, in the main base station, the modulating means modulates a carrier signal having a predetermined frequency with an input information signal and modulates the modulated signal. And the signal generating means generates a local oscillation signal having a predetermined frequency. Next, the electric-optical conversion means converts the non-linear electric
Having a light conversion characteristic, converting the modulation signal output from the modulation means and the local oscillation signal generated by the signal generation means into the modulation signal and the local oscillation signal by using the non-linear electric / optical conversion characteristic. And converting the modulated signal and the local oscillation signal into an electric signal and an optical signal so as to generate at least one mixed frequency component signal. The optical signal including the mixed frequency component signal is transmitted to the optical transmission line. Output.
On the other hand, in the slave base station, the optical-to-electrical conversion unit optically-to-electrically converts an optical signal transmitted from the electric-to-optical conversion unit via the optical transmission line, and includes the signal of the mixed frequency component. After outputting the electric signal, the filtering unit band-filters a signal of a predetermined mixed frequency component among the electric signals output from the optical-electrical conversion unit. Next, the transmitting means wirelessly transmits the signal of the predetermined mixed frequency component filtered by the filtering means.

In the optical transmission system for a wireless link according to the first aspect of the present invention, the main base station and the subordinate base station are connected using the optical transmission line. Radio interference from a link system to a wireless line set between the slave base station and the terminal station can be eliminated. By appropriately setting the carrier frequency of the information signal and the frequency of the local oscillation signal on the main base station side, the radio frequency in the radio line set between the slave base station and the terminal station can be set to an arbitrary value. Can be easily set, for example, in a plurality of microcell zones formed by a plurality of slave base stations, respectively. Hereinafter, this is referred to as a first operation effect. Further, since the slave base station does not include the signal processing device for the information signal, the configuration of the slave base station can be reduced in size and economy, and the slave base station is installed in a smaller space. be able to. Therefore, it is possible to install a large number of wireless devices for each wireless channel in each microcell zone in a predetermined installation space of the slave base station. Hereinafter, this is referred to as a second operation effect. Further, the stability of the frequency of the transmission signal transmitted from the slave base station includes the stability of the frequency of the carrier signal of the modulation signal input to the electro-optical conversion means and the stability of the frequency of the local oscillation signal. The stability of the carrier frequency of the carrier signal generator in the main base station and the stability of the oscillation frequency of the local oscillation signal generator can be easily increased, thereby facilitating the stability of the frequency of the transmission signal in the radio line. Can be increased. Hereafter, this is the third
The effect is called.

Further, in the optical transmission system for a wireless link according to the second aspect, in the slave base station, the receiving means has a predetermined radio frequency modulated by an information signal at a partner station and transmitted by radio. The transmission signal is wirelessly received and a reception signal is output, while the signal generation means includes:
A local oscillation signal having a predetermined frequency is generated. Next, the electric / optical conversion means has a non-linear electric / optical conversion characteristic, and converts the received signal output from the receiving means and the local oscillation signal generated by the signal generation means into the non-linear electric / optical conversion. The reception signal and the local oscillation signal are mixed using the optical conversion characteristic, and the mixing is performed by performing the electrical / optical conversion so that a signal of at least one mixed frequency component between the reception signal and the local oscillation signal is generated. An optical signal including a frequency component signal is output to the optical transmission line. On the other hand, in the main base station, the optical-to-electrical conversion unit performs optical-to-electrical conversion on an optical signal transmitted from the electric-to-optical conversion unit via the optical transmission line to convert the signal of the mixed frequency component. After outputting the electric signal including the signal, the filtering means performs band-pass filtering on a signal of a predetermined mixed frequency component among the electric signals output from the optical-electrical conversion means. Then
The demodulation means demodulates the signal of the mixed frequency component filtered by the filtering means and outputs the information signal. The optical transmission system for a wireless link according to claim 2 configured as described above has the first and second operational effects.

Further, in the optical transmission system for a wireless link according to the third aspect, the main base station includes:
The modulating means converts a carrier signal having a predetermined frequency,
The first information signal is modulated by the input first information signal to output a modulated signal, while the first signal generating means generates a first local oscillation signal having a predetermined frequency. Next, the first electrical-optical conversion means has a non-linear electrical-optical conversion characteristic, and the modulation signal output from the modulation means and the first electrical-optical conversion
The first local oscillation signal generated by the signal generation means is mixed with the modulation signal and the first local oscillation signal by using the non-linear electrical / optical conversion characteristics, and the modulation signal and the first local oscillation signal are mixed. And converting the first optical signal including the mixed frequency component signal into the first optical signal so as to generate at least one mixed frequency component signal between the first optical signal and the local oscillation signal.
To the optical transmission line. On the other hand, in the slave base station, the first optical-to-electrical conversion means includes the first electrical / electrical converter.
After the first optical signal transmitted from the optical conversion means via the first optical transmission line is optically / electrically converted and an electric signal including the mixed frequency component signal is output, the first filtering is performed. The means filters the signal of the predetermined first mixed frequency component among the electric signals output from the first optical-electrical conversion means. Next, the transmitting means wirelessly transmits the signal of the first mixed frequency component filtered by the first filtering means. Further, the receiving means wirelessly receives a transmission signal having a predetermined radio frequency which has been modulated by the second information signal and wirelessly transmitted at the partner station, and outputs a reception signal. The means generates a second local oscillation signal having a predetermined frequency. Next, the second electrical-optical conversion means has a non-linear electrical-optical conversion characteristic, and receives the received signal output from the receiving means and the second local oscillation generated by the second signal generating means. Mixing the received signal with the second local oscillation signal using the non-linear electrical-optical conversion characteristic, and mixing at least one mixed frequency between the received signal and the second local oscillation signal. The second optical signal including the signal of the mixed frequency component is output to the second optical transmission line by performing the electrical / optical conversion so that the component signal is generated. Further, in the main base station, the second optical-to-electrical converting means converts the second optical signal transmitted from the second electrical-to-optical converting means via the second optical transmission line into an optical signal. After the electrical conversion and the output of the electrical signal including the signal of the mixed frequency component, the second filtering means outputs a predetermined signal out of the electrical signals output from the second optical-electrical converting means. The band-pass filtering of the signal of the mixed frequency component 2 is performed. Next, the demodulation means:
The signal of the second mixed frequency component filtered by the second filtering means is demodulated to output the second information signal. The optical transmission system for a wireless link according to claim 3 configured as described above has the first to third effects.

Further, the optical transmission system for a wireless link according to the fourth aspect of the present invention is the optical transmission system for a wireless link according to the third aspect, wherein the first and second optical signals are preferably wavelength-multiplexed. It is transmitted via one optical transmission line.

In the optical transmission system for a wireless link according to the fifth aspect, in the main base station, the modulating means modulates a carrier signal having a predetermined frequency with an input information signal and modulates the modulated signal. And the signal generating means generates a local oscillation signal having a predetermined frequency. Next, the electric-optical conversion means has a non-linear electric-optical conversion characteristic, and uses the non-linear electric-optical conversion characteristic in response to the local oscillation signal generated by the signal generating means. Generating at least one harmonic signal of the signal, and combining the modulation signal output from the modulation means and the generated harmonic signal with the modulation signal and the generation signal using the non-linear electrical-optical conversion characteristics; And mixing the obtained harmonic signal and performing electro-optical conversion to generate a signal of at least one mixed frequency component between the modulated signal and the generated harmonic signal, including the signal of the mixed frequency component. An optical signal is output to the optical transmission line. On the other hand, in the slave base station, the optical-to-electrical conversion unit optically-to-electrically converts an optical signal transmitted from the electric-to-optical conversion unit via the optical transmission line, and includes the signal of the mixed frequency component. After outputting the electric signal, the filtering unit band-filters a signal of a predetermined mixed frequency component among the electric signals output from the optical-electrical converting unit. Next, the transmitting means wirelessly transmits the signal of the mixed frequency component filtered by the filtering means. The optical transmission system for a wireless link according to claim 5 configured as described above has the first to third effects.

In the optical transmission system for a wireless link according to claim 6, in the main base station, the modulating means modulates a carrier signal having a predetermined frequency with an input first information signal. And outputs a modulated signal, while the signal generating means generates a local oscillation signal having a predetermined frequency. Next, the first electric-optical conversion means has a non-linear electric-optical conversion characteristic, and uses the non-linear electric-optical conversion characteristic in response to a local oscillation signal generated by the signal generating means. At least one harmonic signal of the local oscillation signal is generated, and the modulation signal output from the modulation means and the generated harmonic signal are combined with the modulation signal using the non-linear electrical-optical conversion characteristics. And the generated harmonic signal, and performing electro-optical conversion to generate a signal of at least one mixed frequency component between the modulation signal and the generated harmonic signal. A first optical signal including a wave signal and the signal of the mixed frequency component is output to the first optical transmission line. On the other hand, in the slave base station, the first optical
The electrical conversion means optically / electrically converts a first optical signal transmitted from the first electrical / optical conversion means via the first optical transmission line and mixes the generated harmonic signal with the generated harmonic signal. After outputting the electric signal including the frequency component signal, the first
The filtering means performs band filtering of a signal of one predetermined mixing frequency component among the electric signals output from the first optical / electrical converting means, and the second filtering means ,
One predetermined harmonic signal among the electric signals output from the first optical-electrical conversion means is band-filtered.
Next, the transmitting means wirelessly transmits the signal of the mixed frequency component filtered by the first filtering means.
Further, the receiving means wirelessly receives a transmission signal having a predetermined radio frequency, which is modulated by the second information signal and wirelessly transmitted at the partner station, and outputs a reception signal. The conversion unit has a non-linear electrical-optical conversion characteristic, and converts the received signal output from the reception unit and the harmonic signal filtered by the second filtering unit,
The reception signal and the filtered harmonic signal are mixed using the non-linear electrical-optical conversion characteristic, and at least one mixed frequency component between the reception signal and the filtered harmonic signal is mixed. The second optical signal including the signal of the mixed frequency component is output to the second optical transmission line by performing the electrical / optical conversion so that a signal is generated. Further, in the main base station, the second optical / electrical conversion means includes the second electric / electrical conversion means.
After converting the second optical signal transmitted from the optical conversion means via the second optical transmission line into an optical signal and outputting an electric signal including the signal of the mixed frequency component, the third filtering is performed. The means band-filters a signal of a second predetermined mixed frequency component among the electric signals output from the second optical / electrical conversion means. Next, the demodulation means demodulates the signal of the second mixed frequency component filtered by the third filtering means and outputs the second information signal.

The optical transmission system for a wireless link according to the sixth aspect of the invention has the first to third effects. Further, for frequency conversion of the received radio signal, the optical signal transmitted from the main base station is converted into an optical signal.
Since the harmonic signal obtained by the electrical conversion is used as a local oscillation signal, the configuration of the slave base station is simplified as compared with a case where a generator for generating a local oscillation signal is provided in the slave base station. Accordingly, it is possible to reduce the size and cost of the slave base station. Further, since a harmonic component of a local oscillation signal generated by the main base station is used as a local oscillation signal in the first and second electric / optical conversion means, the local base station and the terminal station can communicate with each other. , The degree of freedom in setting the transmission / reception frequency of the wireless line can be increased as compared with the conventional example.

Further, in the optical transmission system for a wireless link according to the present invention, preferably, the first and second optical signals are wavelength-division multiplexed into one. Is transmitted via the optical transmission line.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 is a block diagram of an optical transmission system for a radio link according to a first embodiment of the present invention.

The optical transmission system for a wireless link according to the first embodiment includes a main base station 100, a subordinate base station 200 provided at a predetermined distance from the main base station 100, and a subordinate base station 100. It is composed of two optical fiber cables FC1 and FC2 for connecting to the base station 200, and a mobile terminal station 300 connected to the slave base station 200 via a radio line, and receives a carrier signal from an external device. A baseband signal (hereinafter abbreviated as a BB signal in the drawings)
After combining the FM signal obtained by M-modulation and the local oscillation signal, the combined signal is optically modulated using a laser diode 13 having a non-linear electrical-optical conversion characteristic, and the FM signal is frequency-converted to a radio frequency ( (Hereinafter, referred to as a wireless FM signal), and transmits the first optical signal to the slave base station 200 via the optical fiber cable FC1. After optical-to-electrical conversion of the optical signal, the above-mentioned wireless FM signal is band-filtered by the band-pass filter 31, and the band-filtered wireless F
After the M signal is amplified, it is transmitted to the mobile terminal station 300.

In the slave base station 200, after amplifying the radio FM signal received from the mobile terminal station 300, the slave base station 200 combines the signal with a local oscillation signal, and combines the combined signal with a laser diode 37 having a non-linear electrical-optical conversion characteristic. To a second optical signal including an FM signal frequency-converted to a lower frequency (hereinafter, referred to as a low-frequency-converted FM signal) using the optical fiber cable FC2, and converts the second optical signal into an optical fiber cable FC2.
To the main base station 100, and the main base station 100 optically / electrically converts the second optical signal and then band-filters the low-pass converted FM signal by the band-pass filter 21,
It is characterized in that the band-filtered low-pass converted FM signal is FM-demodulated and a baseband signal is output.

As shown in FIG. 1, the main base station 100
M modulator 10, local oscillation signal generator 11, and combiner 1
2, a laser diode 13, a photodetector 20, a band-pass filter 21, and an FM demodulator 22. On the other hand, the slave base station 200 includes an optical detector 30, a band-pass filter 31, a transmission power amplifier 32, and an antenna duplexer 3.
3, a transmitting / receiving antenna 40, a receiving amplifier 34, a combiner 35, a local oscillation signal generator 36, and a laser diode 37.

In the main base station 100, the FM modulator 10
Is FM-modulated carrier wave signal of frequency fs with a baseband signal input from an external device, and then FM-modulated FM
The signal is output to the synthesizer 12. The synthesizer 12 synthesizes the input FM signal and a local oscillation signal of a sine wave having a frequency fl (fl> fs) generated by the local oscillation signal generator 11, and outputs the synthesized signal to the laser diode 13. I do. The laser diode 13 has a non-linear electrical-optical conversion characteristic, performs an electrical-optical conversion of the input composite signal using the above-mentioned conversion characteristic, and converts the converted optical signal intensity-modulated by the composite signal into an optical signal. The optical signal is output to the fiber cable FC1, whereby the optical signal is transmitted to the optical fiber cable FC1.
Is transmitted to the optical detector 30 in the slave base station 200 via Here, since the laser diode 13 has a non-linear electrical-optical conversion characteristic as described above, the optical signal includes the FM signal of the carrier frequency fs, the local oscillation signal of the frequency fl, and the frequency (fl + fs). FM signal (hereinafter, referred to as
It is called a wireless FM signal. ) And F of the frequency (fl-fs)
Includes electrical signals such as M signals.

In the slave base station 200, the optical detector 30
Detects an optical signal transmitted and input via the optical fiber cable FC1, performs optical-to-electric conversion, and then passes the converted electric signal mainly through only a wireless FM signal component having a frequency (fl + fs). The signal is output to the transmission power amplifier 32 via the band-pass filter 31. The transmission power amplifier 32 power-amplifies the input wireless FM signal of the frequency (fl + fs), outputs the amplified signal to the transmitting / receiving antenna 40 via the antenna duplexer 33, and transmits the wireless FM signal to the transmitting / receiving antenna 41 of the mobile terminal station 300. Wireless transmission to.

Here, the FM signal of the carrier frequency fs is
The laser diode 13 of the main base station 100 can up-convert to a higher frequency wireless FM signal using the local oscillation signal of the frequency fl that has been combined and input, and converts the frequency-converted wireless FM signal to a higher frequency. The band-pass filtering by the band-pass filter 31 of the base station 200 allows the wireless FM signal to be transmitted to the mobile terminal station 30.
0 can be used as a transmission radio signal. That is, the laser diode 13 is used as a high frequency mixer as well as an electric / optical conversion element. Therefore, by appropriately setting the carrier frequency fs and the frequency fl of the local oscillation signal, it is possible to easily generate a radio FM signal having a predetermined radio frequency serving as the transmission radio signal.

On the other hand, after the radio FM signal of the frequency (fl + fs + fd) transmitted from the transmitting / receiving antenna 41 of the mobile terminal station 300 to the transmitting / receiving antenna 40 of the slave base station 200 is received by the transmitting / receiving antenna 40, the antenna duplexer 33 The signal is input to a combiner 35 via a receiving amplifier 34. Here, the radio FM transmitted from the mobile terminal station 300
The signal is obtained by FM-modulating a carrier signal having a frequency fs with a baseband signal, and then the radio frequency (fl + fs + f
d) is a signal obtained by frequency conversion to the frequency fd
Is a transmission / reception frequency interval in a wireless channel between the slave base station 200 and the mobile terminal station 300. The combiner 35 combines the input wireless FM signal and the local oscillation signal of the frequency (fl + fd) generated and input by the local oscillation signal generator 36, and outputs the synthesized signal to the laser diode 37. . The laser diode 37 has a non-linear electrical-optical conversion characteristic, performs electrical-optical conversion of the input composite signal using the above-mentioned conversion characteristic, and converts the converted optical signal intensity-modulated by the composite signal into an optical signal. Output to fiber cable FC2,
Thereby, the optical signal is transmitted to the optical fiber cable FC.
2 is transmitted to the optical detector 20 in the main base station 100. Here, since the laser diode 37 has a non-linear electrical-optical conversion characteristic as described above, the optical signal includes a wireless FM signal having a frequency (fl + fs + fd) and a local oscillation signal having a frequency (fl + fd). Frequency ｛(fl
+ Fs + fd) − (fl + fd) = fs｝ FM signal and frequency ｛(fl + fs + fd) + (fl + fd) =
2fl + fs + 2fd}, including electric signals such as wireless FM signals.

In the main base station 100, the optical detector 20
Is a band-pass filter that detects an optical signal transmitted and input through the optical fiber cable FC2, performs optical / electrical conversion, and passes the converted electrical signal mainly through only the FM signal component of the frequency fs. The signal is output to the FM demodulator 22 via 21. The FM demodulator 22 receives the input FM
The signal is subjected to FM demodulation processing to demodulate and output a baseband signal.

Here, the radio FM signal of the frequency (fl + fs + fd) is transmitted to the laser diode 37 of the slave base station 200.
At the frequency (fl +
fd) can be down-converted to a lower frequency FM signal using the local oscillation signal, and the frequency-converted FM signal can be converted to the band-pass filter 2 of the main base station 100.
After band filtering by 1 and FM demodulation,
A baseband signal can be obtained. That is, the laser diode 37 is used as a high frequency mixer as well as an electric / optical conversion element.

FIG. 4 shows a characteristic example of the power level of the electric signal included in the output optical signal with respect to the power level of the input electric signal in the laser diode 13 of the main base station 100 of the first embodiment. It is a graph. Each set value at the time of measuring this characteristic is as follows. The frequency fs of the input carrier signal fs = 0.9 GHz, the frequency f1 of the input local oscillation signal fl = 4 GHz, and the bias current Id of the laser diode 13 = 35 mA.

As is apparent from FIG. 4, after the frequency conversion, the electric signal included in the optical signal output from the laser diode 13 and output from the photodetector 30 is converted into a signal of the frequency (fl + fs) and a frequency (fl). -Fs).

In the optical transmission system for a wireless link of the first embodiment configured as described above, the main base station 100
And the slave base station 200 through the optical fiber cables FC1, FC
2, it is possible to eliminate radio wave interference from the wireless link system to a wireless line set between the slave base station 200 and the mobile terminal station 300. Main base station 1
By appropriately setting the carrier frequency fs and the local oscillation frequency fl on the side 00, the slave base station 200 and the mobile terminal station 3
Since it is possible to arbitrarily set a radio frequency in a radio line set between 00 and 00, for example, it is easy to set a radio frequency in a plurality of microcell zones formed by a plurality of slave base stations 200, respectively. There is an advantage that can be.

Further, since the slave base station 200 does not include a signal processing device for baseband signals, the configuration of the slave base station 200 can be reduced in size and economy, and the slave base station 200 can be installed in a smaller space. A station 200 can be installed. Therefore, it is possible to install a large number of wireless devices for each wireless channel in each microcell zone in a predetermined installation space of the slave base station 200.

Further, the frequency stability of the radio FM signal transmitted from the slave base station 200 depends on the stability of the frequency fs of the carrier signal generated in the FM modulator 10 and the frequency stability of the local oscillation signal generator 11. Is determined by the stability of the local oscillation signal of the frequency fl, and thus the stability of the oscillation frequency of the carrier signal generator in the FM modulator 10 and the stability of the oscillation frequency of the local oscillation signal generator 11 in the main base station 100. By increasing the frequency, it is possible to easily increase the stability of the frequency of the high-frequency signal used as the transmission signal in the wireless channel.

In the above-described first embodiment, only one slave base station 200 and one mobile terminal station 300 are shown.
And a plurality of mobile terminal stations 300 may be provided.

<Second Embodiment> FIG. 2 is a block diagram of an optical transmission system for a wireless link according to a second embodiment of the present invention.

The optical transmission system for a radio link according to the second embodiment includes a master base station 101 and a slave base station 201,
Compared to the first embodiment, the laser diode 13t in the main base station 101 generates a second harmonic signal of a local oscillation signal having a frequency of 2fl by using its nonlinear electric-optical conversion characteristic, and The second harmonic signal and the FM signal of the carrier frequency fs are mixed to obtain a frequency (2fl +
fs), and transmits an optical signal including these electric signals to the slave base station 201.
, The band width of the wireless FM signal of the frequency (2fl + fs) is filtered by the band-pass
While being used as a transmission radio signal to the local oscillation signal 00, the second harmonic signal of the local oscillation signal was band-filtered by the band-pass filter 39, and the band-filtered second harmonic signal of the local oscillation signal was received. It is characterized in that it is used as a local oscillation signal for down-converting a wireless FM signal. Hereinafter, differences from the first embodiment will be described.

The laser diode 13t has a nonlinear electric
An FM signal having a carrier frequency fs and a local oscillation signal having a frequency fl are combined, and the combined signal inputted is subjected to electrical / optical conversion using the above-described conversion characteristics, and intensity modulation is performed with the combined signal. The converted optical signal is output to the optical fiber cable FC1, so that the optical signal is transmitted to the slave base station 201 via the optical fiber cable FC1.
The light is transmitted to the optical detector 30 inside. Here, the laser diode 13t has its bias voltage and the signal level of the input composite signal so that the signal level of the second harmonic signal of the local oscillation signal in the electric signal included in the optical signal is substantially maximum. Is adjusted. Since the laser diode 13t has a non-linear electrical-optical conversion characteristic as described above, under this state, the optical signal output from the laser diode 13t is composed of the FM signal of the carrier frequency fs and the frequency fl. , A second harmonic signal of the local oscillation signal of frequency (2fl), and F of frequency (fl + fs).
An electrical signal such as an M signal, an FM signal having a frequency (fl-fs), an FM signal having a frequency (2fl + fs) (hereinafter referred to as a wireless FM signal), and an FM signal having a frequency (2fl-fs).

In the slave base station 201, the optical detector 30
Detects an optical signal transmitted and input via the optical fiber cable FC1, performs optical-to-electric conversion, and then passes the converted electric signal mainly through only a wireless FM signal component having a frequency (2fl + fs). Bandpass filter 38
, And to the combiner 35 via a band-pass filter 39 that mainly passes only the second harmonic signal component of the local oscillation signal having a frequency of 2 fl. Further, the transmission power amplifier 32 power-amplifies the input wireless FM signal of the frequency (2fl + fs) and transmits / receives the transmission / reception antenna 40
, And wirelessly transmits the wireless FM signal to the transmitting / receiving antenna 41 of the mobile terminal station 300.

Here, the FM signal of the carrier frequency fs is
Using the second harmonic signal of the local oscillation signal synthesized and input together in the laser diode 13t of the main base station 101, the frequency can be up-converted to a higher frequency wireless FM signal, and the frequency-converted wireless FM signal Is band-filtered by the band-pass filter 38 of the slave base station 201, so that the wireless FM signal can be used as a wireless signal to be transmitted to the mobile terminal station 300. That is, the laser diode 13t is used as a harmonic generator of a local oscillation signal and a high-frequency mixer as well as an electric / optical conversion element. Therefore, by appropriately setting the carrier wave frequency fs and the frequency fl of the local oscillation signal, it is possible to easily generate the radio FM signal serving as the transmission radio signal.

On the other hand, the frequency [2fl + fs ';fs' = fs + f transmitted from the transmitting / receiving antenna 41 of the mobile terminal station 300 to the transmitting / receiving antenna 40 of the slave base station 201.
d (transmission / reception frequency interval)], after being received by the transmission / reception antenna 40, is input to the combiner 35 via the antenna duplexer 33 and the reception amplifier 34. here,
The radio FM signal transmitted from the mobile terminal station 300 is a signal obtained by frequency-modulating a carrier signal having a frequency fs ′ with a baseband signal and then converting the frequency to the radio frequency (2fl + fs ′). The combiner 35 combines the input wireless FM signal with the second harmonic signal of the local oscillation signal having a frequency of 2 fl input from the band-pass filter 39, and outputs the combined signal to the laser diode 37. Further, the laser diode 37 has a non-linear electrical-optical conversion characteristic, performs an electrical-optical conversion of the input composite signal using the above-mentioned conversion characteristic, and modulates the intensity of the optical signal by the composite signal. To the optical fiber cable FC2, whereby the optical signal is transmitted to the optical detector 20 in the main base station 101 via the optical fiber cable FC2. Here, since the laser diode 37 has a non-linear electric-optical conversion characteristic as described above, the optical signal is a radio FM signal of a frequency (2fl + fs ′),
A local oscillation signal having a frequency of 2fl and a frequency ｛(2fl + f
s ′) − 2fl = fs ′}, and the frequency ｛(2
fl + fs ′) + 2fl = 4fl + fs ′｝ wireless FM
Includes electrical signals such as signals.

In the main base station 101, the optical detector 20
Is a band pass that detects an optical signal transmitted and input via the optical fiber cable FC2, performs optical / electrical conversion, and then passes the converted electrical signal mainly through only the FM signal component of the frequency fs ′. The signal is output to the FM demodulator 22 via the filter 21. The FM demodulator 22 receives the input F
An FM demodulation process is performed on the M signal to demodulate and output a baseband signal.

Here, the radio FM signal of the frequency (2fl + fs ′) is down-converted to a lower frequency FM signal using the local oscillation signal of the frequency 2fl, which is combined and inputted in the laser diode 37 of the slave base station 201. The baseband signal can be converted, and the frequency-converted FM signal can be band-filtered by the band-pass filter 21 of the main base station 101 and then FM-demodulated to obtain a baseband signal. That is, the laser diode 37 is used as a high frequency mixer as well as an electric / optical conversion element.

FIG. 5 shows a characteristic example of the power level of the electric signal included in the output optical signal with respect to the power level of the input electric signal in the laser diode 13t of the main base station 101 of the second embodiment. It is a graph. Each set value at the time of measuring this characteristic is as follows. The frequency fs of the input carrier signal fs = 0.9 GHz, the frequency f1 of the input local oscillation signal fl = 4 GHz, and the bias current Id of the laser diode 13t = 35 mA.

As is clear from FIG. 5, the optical detector 30 includes the optical signal output from the laser diode 13t and
It can be seen that, after the frequency conversion, the electric signal output from the signal includes the signal of the frequency (2fl + fs), the signal of the frequency (2fl-fs), and the signal of the frequency 2fl.

The optical transmission system for a radio link according to the second embodiment configured as described above has the same effects as those of the first embodiment, and also has a lower base station 201 than the first embodiment. Since it is not necessary to provide the local oscillation signal generator 36 in the above, the configuration of the slave base station is simplified, and its size and cost can be reduced.

In the second embodiment described above, the laser diode 13t in the main base station 101 generates the second harmonic signal of the local oscillation signal having a frequency of 2fl by using the nonlinear electric / optical conversion characteristics. At the same time, the second harmonic signal and the FM signal of the carrier frequency fs are mixed to generate a radio FM signal of a frequency (2fl + fs), and an optical signal including these electric signals is transmitted to the slave base station 201; In the slave base station 201, the frequency (2fl + f
s) The band-pass filter 38 band-pass filters the wireless FM signal and uses it as a transmission radio signal to the mobile terminal station 300. The band-pass filter 39 band-filters the second harmonic signal of the local oscillation signal. Then, the second harmonic of the local oscillation signal subjected to the band filtering is used as a local oscillation signal for down-converting the received wireless FM signal. However, the present invention is not limited to this, and instead of the second harmonic signal of the local oscillation signal, another harmonic signal such as the third, fourth, fifth or sixth harmonic signal of the local oscillation signal is used. You may.

In the above second embodiment, only one slave base station 201 and one mobile terminal station 300 are shown. However, the present invention is not limited to this, and a plurality of slave base stations 201 are provided.
And a plurality of mobile terminal stations 300 may be provided.

<Third Embodiment> FIG. 3 is a block diagram of a wireless link optical transmission system according to a third embodiment of the present invention.

The optical transmission system for a wireless link according to the third embodiment comprises a main base station 102 and three slave base stations 2 provided at predetermined distances from the main base station 102, respectively.
00a, 200b, 200c, and six optical fiber cables FC11 to FC13, F for connecting the main base station 102 to the slave base stations 200a, 200b, 200c.
C21 to FC23, a mobile terminal station 300a connected to the slave base station 200a via a wireless line, and a slave base station 20
0b and a mobile terminal station 300b connected via a wireless line
And a mobile terminal station 300c connected to the slave base station 200c via a wireless line.

In the main base station 102, each FM modulator 1
0a, 10b, 10c and each local oscillation signal generator 11
a, 11b, 11c and each of the synthesizers 12a, 12b, 12
c operates similarly to those of the first embodiment. Each of the laser diodes 10a, 10b, and 10c operates in the same manner as those of the first embodiment in response to the input composite signal, and converts each optical signal having the first to third wavelengths different from each other. It is generated and output to the light combiner 60, respectively. Next, the optical combiner 60 wavelength-multiplexes and combines the three input optical signals, and outputs the multiplexed optical signal after the multiplex combination to the optical combiner 60.
Loss and the optical fiber cables FC11, FC1
2. The signal is transmitted to an optical branch circuit 71 provided in the slave base station 200a via an optical amplifier 61 for compensating for the loss of FC13 and an optical fiber cable FC11.

In the slave base station 200a, the optical branching circuit 7
1 selects and filters an optical signal having a first wavelength from the input multiplexed optical signals and outputs the filtered optical signal to the slave base station 200a, and also converts each optical signal having the second and third wavelengths into an optical fiber cable FC12. To the optical branch circuit 72 provided in the slave base station 200b.

The slave base station 200a performs the same processing as that of the slave base station 200 of the first embodiment on the input optical signal. Here, the transmitting / receiving antenna 40 of the slave base station 200a
a and a transmission / reception antenna 41a of the mobile terminal station 300a, a wireless channel is set in the same manner as in the first embodiment. The optical signal including the information of the radio signal received by the slave base station 200a is output to the optical combiner 81. The optical combiner 81 wavelength-multiplexes the optical signal transmitted from the optical combiner 82 of the slave base station 200b via the optical fiber cable FC22 with the optical signal output from the slave base station 200a and combines the signals, as described later. The combined multiplexed optical signal is transmitted to the optical fiber cable FC2.
1, and is transmitted to the optical distributor 63 of the main base station 102 via the optical amplifier 62 for compensating for the demultiplexing loss of the optical distributor 63 and the loss of each of the optical fiber cables FC21, FC22, FC23.

In the slave base station 200b, the optical branching circuit 72 selectively filters the optical signal having the second wavelength out of the input multiplexed optical signals and outputs the filtered signal to the slave base station 200b. The optical signal having the wavelength is transmitted to the slave base station 200c via the optical fiber cable FC13.

The slave base station 200b performs the same processing on the input optical signal as the slave base station 200 of the first embodiment. Here, the transmitting / receiving antenna 40 of the slave base station 200b
As in the first embodiment, a wireless channel is set between the communication terminal b and the transmitting / receiving antenna 41b of the mobile terminal station 300b. The optical signal including the information of the radio signal received by the slave base station 200b is output to the optical combiner 82. The photosynthesizer 82 is connected to the optical fiber cable FC from the base station 200c as described later.
The optical signal transmitted via the optical fiber 23 and the optical signal output from the slave base station 200b are wavelength-multiplexed and combined, and the combined multiplexed optical signal is optically combined by the optical combiner of the slave base station 200a via the optical fiber cable FC22. Transmit to 81.

The slave base station 200c performs the same processing on the optical signal transmitted via the optical fiber cable FC13 as the slave base station 200 of the first embodiment. Here, a wireless channel is set between the transmission / reception antenna 40c of the slave base station 200c and the transmission / reception antenna 41c of the mobile terminal station 300c as in the first embodiment. The optical signal including the information of the radio signal received by the slave base station 200c is transmitted via the optical fiber cable FC23 to the optical combiner 82 of the slave base station 200b.
Is transmitted to

In the main base station 100, the optical distributor 63 distributes the transmitted optical signals having different wavelengths by wavelength and outputs the optical signals to the optical detectors 20a, 20b and 20c. Here, the optical signal output and transmitted from the slave base station 200a is output to the optical detector 20a, and the slave base station 2a
The optical signal output from 00b and transmitted is output to the optical detector 20b, and the optical signal output from the slave base station 200c and transmitted is output to the optical detector 20c. Each optical detector 20a, 20b, 20c, each bandpass filter 21a, 21b, 21c, and each FM demodulator 22a, 2
2b and 22c operate similarly to those of the first embodiment.

In the third embodiment configured as described above, in order to compensate for the above-mentioned loss, the optical amplifiers 61, 6
2, the slave base stations 200a, 200b, 2
00c can be greatly expanded.

In the above third embodiment, when each of the slave base stations 200a, 200b, 200c uses one set of transmission and reception frequencies, a plurality of baseband signals are transmitted in a time division multiplexed manner. Signal may be used. In addition, each slave base station 200a, 20
When a plurality of sets of transmission and reception frequencies are used in Ob and 200c, the baseband FM signal to be transmitted may be a signal obtained by frequency-multiplexing a plurality of baseband signals.

In the third embodiment, the main base station 1
02, the main base station 100 of the first embodiment is applied, and the slave base stations 200a, 200b, 200c have the same configuration as the slave base station 200 of the first embodiment. However, the present invention is not limited to this, and the main base station 100 of the second embodiment is applied to the main base station 102, and the sub base stations 200a, 200
00b and 200c may be configured to have the same configuration as the slave base station 200 of the second embodiment.

<Other Embodiments> In the first to third embodiments, the FM modulators 10, 10a, 10b, and 10c are used.
However, the present invention is not limited to this, and a modulator of another modulation scheme such as an FSK modulator may be used.

In the above first and second embodiments, each optical signal transmitted through the optical fiber cables FC1 and FC2 may be wavelength-multiplexed and transmitted using one optical fiber cable.

[0067]

As described above in detail, according to the optical transmission system for a radio link according to the first aspect of the present invention, the main base station and the sub-station provided at a predetermined distance from the main base station are provided. An optical transmission system for a radio link, comprising a base station and an optical transmission line connecting the master base station and the slave base station, wherein the master base station inputs a carrier signal having a predetermined frequency. A modulating means for modulating with an information signal to be outputted and a modulating signal; a signal generating means for generating a local oscillation signal having a predetermined frequency; and a non-linear electrical-optical conversion characteristic, which is output from the modulating means. The modulation signal and the local oscillation signal generated by the signal generation means are mixed with the modulation signal and the local oscillation signal by using the non-linear electrical / optical conversion characteristics, and the modulation signal and the local oscillation signal are mixed. At least in between Electrical-optical conversion means for performing optical-optical conversion so as to generate one mixed frequency component signal and outputting an optical signal including the mixed frequency component signal to the optical transmission line, wherein the slave base station comprises: An optical-to-electrical conversion unit that performs optical-to-electrical conversion of an optical signal transmitted from the electrical-to-optical conversion unit via the optical transmission line and outputs an electrical signal including a signal of the mixed frequency component; Filtering means for band-pass filtering a signal of a predetermined mixed frequency component of the electric signal output from the conversion means, and wirelessly transmitting the signal of the predetermined mixed frequency component filtered by the filtering means Transmission means for transmitting.

Therefore, since the main base station and the slave base station are connected by using the optical transmission line, the wireless link set between the slave base station and the terminal station from the wireless link system. Radio interference can be eliminated. By appropriately setting the carrier frequency of the information signal and the frequency of the local oscillation signal on the main base station side, the radio frequency in the radio line set between the slave base station and the terminal station can be set to an arbitrary value. Can be easily set, for example, in a plurality of microcell zones formed by a plurality of slave base stations, respectively.

Since the slave base station is not provided with a signal processing device for the information signal, the configuration of the slave base station can be reduced in size and economy, and the slave base station can be installed in a smaller space. Can be installed. Therefore, it is possible to install a large number of wireless devices for each wireless channel in each microcell zone in a predetermined installation space of the slave base station.

Further, the frequency stability of the transmission signal transmitted from the slave base station is determined by the frequency stability of the carrier signal of the modulated signal input to the electro-optical conversion means and the frequency of the local oscillation signal. The stability of the carrier frequency of the carrier signal generator in the main base station and the stability of the oscillation frequency of the local oscillation signal generator are increased, so that the frequency of the transmission signal in the radio line can be easily determined. Stability can be increased.

Also, According to the optical transmission system for a wireless link according to claim 6 of the present invention, a main base station, a sub base station provided at a predetermined distance from the main base station,
An optical transmission system for a radio link, comprising first and second optical transmission lines connecting the master base station and the slave base station, wherein the master base station transmits a carrier signal having a predetermined frequency. A modulating means for modulating the input first information signal to output a modulated signal, a signal generating means for generating a local oscillation signal having a predetermined frequency, and a non-linear electrical-optical conversion characteristic, Generating at least one harmonic signal of the local oscillation signal using the non-linear electrical-optical conversion characteristic in response to the local oscillation signal generated by the signal generation means, and a modulation signal output from the modulation means; And the generated harmonic signal by the nonlinear electric
The modulation signal is mixed with the generated harmonic signal by using the light conversion characteristic, and the electric signal is generated so as to generate a signal of at least one mixed frequency component between the modulation signal and the generated harmonic signal. First electrical-optical conversion means for optically converting and outputting a first optical signal including the generated harmonic signal and the signal of the mixed frequency component to the first optical transmission line; The base station optically / electrically converts a first optical signal transmitted from the first electric / optical conversion means via the first optical transmission line, and generates the generated harmonic signal and the mixed frequency. A first optical-to-electrical conversion means for outputting an electric signal including a signal of the component, and a signal of one predetermined mixed frequency component among the electric signals output from the first optical-to-electrical conversion means First filtering means for filtering;
Second filtering means for band-filtering one predetermined harmonic signal of the electric signals output from the first optical-electrical converting means, and filtering by the first filtering means; Transmitting means for wirelessly transmitting the signal of the mixed frequency component, and receiving for outputting a received signal by wirelessly receiving a transmission signal having a predetermined radio frequency modulated and transmitted by the second information signal at a partner station. Means for converting the received signal output from the receiving means and the harmonic signal filtered by the second filtering means into a nonlinear electrical-optical conversion Mixing the received signal and the filtered harmonic signal using a characteristic, wherein at least one signal between the received signal and the filtered harmonic signal is mixed;
A second optical-to-optical converter that performs electrical-optical conversion to generate two mixed-frequency component signals and outputs a second optical signal including the mixed-frequency component signal to the second optical transmission line. Wherein the main base station further optically / electrically converts a second optical signal transmitted from the second electric / optical conversion means via the second optical transmission line, and outputs a signal of the mixed frequency component. A second optical-to-electrical converting means for outputting an electric signal including: a band-pass filtering of a signal of a second predetermined mixed frequency component among the electric signals outputted from the second optical-to-electrical converting means And a demodulating means for demodulating the signal of the second mixed frequency component filtered by the third filtering means and outputting the second information signal.

Therefore, the optical transmission system for a wireless link according to the sixth aspect has the above-mentioned effects. In addition, since the harmonic signal obtained by optical-to-electrical conversion of the optical signal transmitted from the main base station is used as a local oscillation signal for frequency conversion of the received radio signal, The configuration of the slave base station can be simplified as compared with the case where a generator for generating a local oscillation signal is provided in the base station, whereby the size and cost of the slave base station can be reduced. . Further, the first and second electricity
Since the harmonic component of the local oscillation signal generated in the main base station is used as the local oscillation signal in the optical conversion means, the setting of the transmission / reception frequency of the radio line between the slave base station and the terminal station is performed. The degree of freedom can be increased as compared with the conventional example.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical transmission system for a wireless link according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an optical transmission system for a wireless link according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a wireless link optical transmission system according to a third embodiment of the present invention.

FIG. 4 is a graph illustrating a characteristic example of a power level of an electric signal included in an output optical signal with respect to a power level of an input electric signal in a laser diode of a main base station in the first embodiment.

FIG. 5 is a graph showing a characteristic example of a power level of an electric signal included in an output optical signal with respect to a power level of an input electric signal in a laser diode of a main base station in the second embodiment.

[Explanation of symbols]

 10, FM modulator, 11, 36, local oscillation signal generator, 12, 35, synthesizer, 13, 13t, 37, laser diode, 20, 30, photodetector, 22, FM demodulator, 21, 31, 38, 39: band-pass filter, 32: transmission power amplifier, 34: reception amplifier, 40, 41: transmission / reception antenna, 100, 101: master base station, 200, 201: slave base station, 300: mobile terminal station, FC1, FC2: Optical fiber cable.

Claims (7)

(57) [Claims] 1. A radio system comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; and an optical transmission line connecting the main base station and the sub base station. An optical transmission system for link, wherein the main base station modulates a carrier signal having a predetermined frequency with an input information signal to output a modulation signal, and a local oscillation signal having a predetermined frequency. And a non-linear electrical-to-optical converter that has a non-linear electrical-to-optical conversion characteristic, and converts the modulated signal output from the modulator and the local oscillation signal generated by the signal generator to the nonlinear electrical-to-optical conversion. The modulation signal and the local oscillation signal are mixed using characteristics, and the mixed frequency component is subjected to electro-optical conversion so as to generate at least one mixed frequency component signal between the modulation signal and the local oscillation signal. of Electrical / optical conversion means for outputting an optical signal including a signal to the optical transmission line, wherein the slave base station converts an optical signal transmitted from the electrical / optical conversion means via the optical transmission line into an optical / optical signal. An optical-to-electrical conversion unit that performs electrical conversion and outputs an electrical signal including the signal of the mixed frequency component, and filters a signal of a predetermined mixed frequency component among the electrical signals output from the optical-to-electrical conversion unit. An optical transmission system for a wireless link, comprising: a filtering unit that oscillates; and a transmitting unit that wirelessly transmits a signal of the predetermined mixed frequency component filtered by the filtering unit. 2. A radio comprising a main base station, a sub base station provided at a predetermined distance from the main base station, and an optical transmission line connecting the main base station and the sub base station. An optical transmission system for link, wherein the slave base station wirelessly receives a transmission signal having a predetermined radio frequency, which is modulated by an information signal and wirelessly transmitted at a partner station, and outputs a reception signal, Signal generation means for generating a local oscillation signal having a predetermined frequency; and a non-linear electrical-optical conversion characteristic, wherein the reception signal output from the reception means and the local oscillation signal generated by the signal generation means are And mixing the received signal and the local oscillation signal by using the non-linear electrical-optical conversion characteristic so as to generate at least one mixed frequency component signal between the received signal and the local oscillation signal. Electrical-optical conversion means for performing optical conversion and outputting an optical signal including the signal of the mixed frequency component to the optical transmission line, wherein the main base station is configured to transmit the optical signal from the electrical-optical conversion means via the optical transmission line. Optical-to-electrical conversion means for optically / electrically converting the transmitted optical signal to output an electric signal including the signal of the mixed frequency component, and a predetermined one of the electric signals output from the optical / electrical conversion means Filtering means for band-filtering the mixed frequency component signal, and demodulating means for demodulating the mixed frequency component signal filtered by the filtering means and outputting the information signal. Optical transmission system for wireless links. 3. A main base station, a sub base station provided at a predetermined distance from the main base station, and first and second optical transmissions connecting the main base station and the sub base station. An optical transmission system for a radio link, comprising: a transmission line; and a modulation unit that modulates a carrier signal having a predetermined frequency with an input first information signal to output a modulation signal. A first signal generating means for generating a first local oscillation signal having a predetermined frequency; a modulated signal having a non-linear electric-optical conversion characteristic, outputted from the modulating means; And the first local oscillation signal generated by the means.
The modulation signal and the first local oscillation signal are mixed using the optical conversion characteristic, and the electric power and the first local oscillation signal are mixed such that a signal of at least one mixed frequency component is generated between the modulation signal and the first local oscillation signal. First electrical-optical conversion means for performing optical conversion and outputting a first optical signal including the signal of the mixed frequency component to the first optical transmission line, wherein the slave base station comprises: A first optical-to-electrical conversion of the first optical signal transmitted from the electrical-to-optical conversion means via the first optical transmission line to output an electrical signal including the mixed frequency component signal;
Optical-to-electrical converting means, and first filtering means for band-filtering a signal of a predetermined first mixed frequency component among the electric signals output from the first optical-to-electrical converting means, Transmitting means for wirelessly transmitting the signal of the first mixed frequency component filtered by the first filtering means; and transmitting a predetermined radio frequency modulated by the second information signal and wirelessly transmitted at a partner station. Receiving means for receiving a transmission signal by radio and outputting a reception signal, second signal generation means for generating a second local oscillation signal having a predetermined frequency, and non-linear electrical-optical conversion characteristics, The received signal output from the receiving means and the second local oscillation signal generated by the second signal generating means are combined with the non-linear electric
Using the optical conversion characteristic, the received signal and the second local oscillation signal are mixed to generate an electric signal such that at least one mixed frequency component signal is generated between the received signal and the second local oscillation signal. A second optical-to-optical converter for optically converting and outputting a second optical signal including the signal of the mixed frequency component to the second optical transmission line, wherein the main base station further comprises: A second optical signal transmitted from the electrical / optical conversion means via the second optical transmission line to optical / electrical conversion to output an electrical signal including the signal of the mixed frequency component.
Optical-to-electrical converting means, and second filtering means for band-filtering a signal of a predetermined second mixed frequency component among the electric signals output from the second optical-to-electrical converting means, Demodulating means for demodulating the signal of the second mixed frequency component filtered by the second filtering means and outputting the second information signal, wherein the optical transmission for a radio link is provided. system. 4. The optical transmission system for a radio link according to claim 3, wherein said first and second optical signals are wavelength-multiplexed and transmitted via one optical transmission line. 5. A radio system comprising: a main base station; a sub base station provided at a predetermined distance from the main base station; and an optical transmission line connecting the main base station and the sub base station. An optical transmission system for link, wherein the main base station modulates a carrier signal having a predetermined frequency with an input information signal to output a modulation signal, and a local oscillation signal having a predetermined frequency. A signal generating means for generating the local oscillation signal having a non-linear electrical / optical conversion characteristic, and using the non-linear electrical / optical conversion characteristic in response to the local oscillation signal generated by the signal generating means. At least one harmonic signal is generated, and the modulated signal output from the modulating means and the generated harmonic signal are combined with the modulated signal and the generated harmonic signal using the non-linear electrical / optical conversion characteristics. High Wave signal and electro-optical conversion so as to generate at least one signal of a mixed frequency component between the modulation signal and the generated harmonic signal. An electrical-optical conversion means for outputting to the optical transmission line, wherein the slave base station optical-electrically converts an optical signal transmitted from the electrical-optical conversion means via the optical transmission line and performs the mixing. An optical-to-electrical conversion unit that outputs an electric signal including a signal of a frequency component, and a filter that band-filters a signal of a predetermined mixed frequency component among the electric signals output from the optical-to-electrical conversion unit Means, and a transmitting means for wirelessly transmitting the signal of the mixed frequency component filtered by the filtering means. 6. A main base station, a sub base station provided at a predetermined distance from the main base station, and first and second optical transmissions connecting the main base station and the sub base station. An optical transmission system for a radio link, comprising: a transmission line; and a modulation unit that modulates a carrier signal having a predetermined frequency with an input first information signal to output a modulation signal. A signal generating means for generating a local oscillation signal having a predetermined frequency; and a non-linear electro-optical converter having non-linear electrical-optical conversion characteristics in response to the local oscillation signal generated by the signal generating means. A characteristic signal is used to generate at least one harmonic signal of the local oscillation signal, and a modulation signal output from the modulating means and the generated harmonic signal are converted using the nonlinear electrical-optical conversion characteristic. Above the modulation signal Mixing the generated harmonic signal and performing electro-optical conversion to generate a signal of at least one mixed frequency component between the modulated signal and the generated harmonic signal; A first electrical / optical conversion means for outputting a first optical signal including the signal and the signal of the mixed frequency component to the first optical transmission line, wherein the slave base station comprises: The first optical signal transmitted from the optical conversion means via the first optical transmission line is optically / electrically converted to output an electric signal including the generated harmonic signal and the signal of the mixed frequency component. A first optical-to-electrical conversion unit; a first filtering unit for band-filtering a signal of one predetermined mixed frequency component among the electric signals output from the first optical-to-electrical conversion unit; Electricity output from the first optical-to-electrical conversion means Second filtering means for band-filtering one predetermined harmonic signal among signals, and transmitting means for wirelessly transmitting the mixed frequency component signal filtered by the first filtering means. Receiving means for wirelessly receiving a transmission signal having a predetermined radio frequency which has been modulated by the second information signal and wirelessly transmitted at the partner station and outputting a reception signal; and a non-linear electrical-optical conversion characteristic, The received signal output from the receiving means and the harmonic signal filtered by the second filtering means are combined with the received signal and the filtered harmonic by using the non-linear electrical / optical conversion characteristic. A second signal including a signal of the mixed frequency component by performing an electro-optical conversion so as to generate a signal of at least one mixed frequency component between the received signal and the filtered harmonic signal by mixing the received signal and the filtered harmonic signal. The second optical signal A second electrical / optical converter for outputting to a transmission line, wherein the main base station further comprises a second electrical / optical converter which transmits the second electrical / optical converter via the second optical transmission line from the second electrical / optical converter. A second optical-to-electrical conversion of the optical signal to output an electrical signal including the mixed frequency component signal;
A light-to-electric conversion means, and a third filtering means for band-filtering a signal of a predetermined second mixed frequency component among the electric signals output from the second light-to-electric conversion means, Demodulating means for demodulating the signal of the second mixed frequency component filtered by the third filtering means and outputting the second information signal. system. 7. The optical transmission system for a radio link according to claim 6, wherein said first and second optical signals are wavelength-multiplexed and transmitted via one optical transmission line.