JP2007036751A - Optical signal transmitter and optical signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a part of an optical transmission signal into carriers for transmission so that the optical transmission signal will not become wideband, in order to reduce the cost of optical components. <P>SOLUTION: When an optical interface portion 2 converts an RF signal into an optical signal of an IF signal for transmission, a combiner 25 combines an IF signal outputted from a first mixer 23 with an original signal having a control signal modulated by a modulating portion 24. An E/O portion 26 converts the combined signal into an optical signal for transmission by an optical fiber 4. When an optical advance base station 3 receives the optical signal, an O/E portion 31 converts the optical signal into an electrical signal. After demodulating portion 33 separates and extracts the control signal and the original signal, a second LO signal generating portion 34 converts the original signal into a LO signal. A second mixer 35 generates a radio-frequency signal by using the LO signal and an IF signal from a demultiplexer 32. Then, the radio frequency signal is returned to the original radio frequency signal, based on the control signal to be outputted from an antenna 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical signal transmitting apparatus and an optical signal receiving apparatus that constitute an optical signal transmission system based on an IF (Intermediate Frequency) optical transmission system that transmits and receives an optical signal in an intermediate frequency band.

  2. Description of the Related Art Conventionally, various analog optical transmission optical signal transmission systems that convert a high-frequency wireless signal (hereinafter referred to as an RF (Radio Frequency) signal) into an optical signal and transmit the optical signal are known. However, these optical signal transmission systems based on the analog optical transmission system require a wide-band optical component having excellent linearity in characteristics, and are therefore quite expensive. Therefore, in order to reduce the cost, an optical signal transmission system of an IF optical transmission system is used in which an RF signal is converted into an IF signal and then converted into an optical signal and transmitted. In this optical signal transmission system of the IF optical transmission system, it is used for up-conversion with the frequency of an LO (Local Oscillation) signal used for down-conversion in order to return to the original RF signal after transmission of the optical signal. It is necessary to match the frequency of the LO signal. Therefore, a method has been proposed in which an IF signal and an unmodulated wave are multiplexed and optically transmitted, and an LO signal is generated from the unmodulated wave using a multiplier after the optical transmission (see, for example, Patent Document 1). According to this technique, an LO signal having the same frequency can be obtained on the antenna side of each radio zone by optically transmitting an unmodulated wave having a frequency near the IF band from the radio main body to the antenna side. Therefore, even if the optical transmission device has poor linearity in the RF band, if the linearity in the IF band is good, the band frequency required for optical transmission from the radio main unit to the antenna is changed from the RF band to the IF. As a result, the cost of the optical transmission apparatus can be reduced.

In addition, in the IF optical transmission system, a system has also been proposed in which a control signal for controlling the amplification degree of the downstream signal amplifier of the optical forward base station is transmitted by being superimposed on the downstream transmission signal (see, for example, Patent Document 2). . This technology is a cell transmission system in which a radio base station call zone is divided into a plurality of microcells, an optical advance base station is provided for each microcell, and the radio base station and the optical advance base station are connected by an optical fiber. . According to this technique, a pilot signal (that is, a control signal) is superimposed on a downlink transmission signal, and the gain of the variable amplifier is controlled by detecting the level of the pilot signal, so that even if the temperature variation of the amplifier characteristic is large The downlink transmission output level and the amplification degree of the uplink reception signal can be kept constant. Therefore, since general-purpose optical components can be used, it is possible to reduce the cost of the optical communication system using the IF optical transmission method.
JP-A-6-164427 JP-A-8-149552

  However, the technique disclosed in Patent Document 2 uses a pilot signal (control signal) as a downlink signal in order to control the amplification degree of the downlink signal by using an IF optical transmission system to which inexpensive optical components can be applied. Although it is possible to superimpose, the IF signal, the original oscillation signal, and the pilot signal must be transmitted in different frequency bands. As a result, the optical transmission signal becomes a wide band, and as a result, the cost of the optical communication system increases. Also in the technique of the above-mentioned Patent Document 1, since the IF signal, the original oscillation signal, and the control signal must be transmitted in different bands, the optical transmission signal becomes a wide band, which increases the cost of the wireless communication system. There is a fear.

  The present invention has been made in view of the above points, and by multiplexing a part of an optical transmission signal on a carrier wave and transmitting it, the optical transmission signal can be prevented from becoming a broadband and the cost of optical components can be reduced. An object of the present invention is to provide an optical signal transmitter and an optical signal receiver.

  The optical signal transmission apparatus of the present invention includes an original vibration signal generating means for generating an original vibration signal, a first LO signal generating means for generating an LO signal from the original vibration signal generated by the original vibration signal generating means, A first mixer that converts an RF signal into an IF signal using the LO signal generated by the first LO signal generating means, and an original generated by the original vibration signal generating means based on an input control signal A modulation means for modulating an oscillation signal; a multiplexing means for multiplexing the IF signal output from the first mixer; and an original oscillation signal modulated by the modulation means; and the multiplexing means And an electrical / optical conversion means for converting the combined signal from an electrical signal to an optical signal.

  The optical signal receiving apparatus of the present invention includes an optical / electrical conversion means for converting an optical signal received from the optical signal transmission apparatus into an electrical signal, and an electrical signal output from the optical / electrical conversion means as an IF signal. Demultiplexing means for demultiplexing into a modulated original oscillation signal, and a control obtained by demodulating the original oscillation signal and the modulated original oscillation signal obtained by removing the modulation component from the modulated original oscillation signal A demodulating means for generating a signal, a second LO signal generating means for generating an LO signal from the original signal, and an LO signal generated by the second LO signal generating means, A second mixer for converting the input IF signal into an RF signal, and an amplifier for controlling the gain by the control signal demodulated by the demodulating means and amplifying the RF signal output from the second mixer and outputting the amplified signal Means.

  The optical signal transmission apparatus of the present invention includes an original vibration signal generating means for generating an original vibration signal, and a first LO signal generating means for generating an LO signal from the original vibration signal generated by the original vibration signal generating means. A first mixer that converts the RF signal into the IF signal using the LO signal generated by the first LO signal generating means, and the first LO signal based on the input control signal. Modulating means for modulating the LO signal generated by the generating means; combining means for combining the IF signal output from the first mixer and the LO signal modulated by the modulating means; and the combining And an electrical / optical conversion means for converting the combined signal combined by the means from an electrical signal to an optical signal.

  The optical signal receiving apparatus of the present invention includes an optical / electrical conversion means for converting an optical signal received from the optical signal transmission apparatus into an electrical signal, and an electrical signal output from the optical / electrical conversion means as an IF signal. A demultiplexing means for demultiplexing into a modulated LO signal, a LO signal obtained by removing a modulation component from the modulated LO signal, and a control signal obtained by demodulating the modulated LO signal A demodulating means for demodulating, a second mixer for converting the IF signal input from the demultiplexing means to an RF signal using the demodulated LO signal, and a control signal demodulated by the demodulating means. And amplifying means for controlling and amplifying and outputting the RF signal output from the second mixer.

  According to the present invention, since the original oscillation signal is used as the carrier wave for transmitting the control signal on the optical signal transmission device side, the frequency band occupied by the optical transmission signal can be narrowed. Alternatively, since the LO signal is used as a carrier wave for transmitting the control signal, the frequency band occupied by the optical transmission signal can be narrowed. This simplifies the circuit configuration of the optical signal transmission device, so that inexpensive optical components can be used. On the optical signal receiver side, the control signal and the original oscillation signal or LO signal can be separated and extracted by the demodulator, so that the optical transmission signal transmitted in a narrow transmission band can be easily converted to the original RF signal. Can be returned. This simplifies the circuit configuration of the optical signal receiving apparatus and allows the use of inexpensive optical components. Therefore, it is possible to construct an optical signal transmission system that reduces costs.

<Summary of invention>
In the optical signal transmission system according to the present invention, when the optical signal transmitter converts the RF signal into an optical signal of IF signal and transmits it, the original oscillation signal or LO signal (local oscillation signal) is used as a carrier wave, and this carrier wave is controlled. The signal is modulated and transmitted optically. Further, when the optical signal receiving device side receives the optical signal of the IF signal, the demodulator separates the control signal and the original oscillation signal or the LO signal, and then extracts the original RF signal based on the control signal. It is returning. Accordingly, since a broadband frequency is not required for the optical transmission signal, the circuit configuration of the optical signal transmitting device and the optical signal receiving device is simplified, so that inexpensive optical components can be used. As a result, an optical signal transmission system can be constructed at a low cost.

  Hereinafter, embodiments of an optical signal transmission system according to the present invention will be described in detail with reference to the drawings. In the drawings used in the embodiments, the same components are denoted by the same reference numerals, and redundant description is omitted as much as possible.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of an optical signal transmission system according to Embodiment 1 of the present invention. The optical signal transmission system shown in FIG. 1 includes a radio base station 1 that transmits an RF signal and a control signal, an optical interface unit 2 that is an optical signal transmitter, an optical forward base station 3 that is an optical signal receiver, The optical fiber 4 that connects the interface unit 2 and the optical advance base station 3 and the antenna 5 that wirelessly transmits the RF signal output from the optical advance base station 3 are configured.

  The optical interface unit 2, which is an optical signal transmission device, includes an original vibration signal generator 21 that generates an original vibration signal (that is, an original oscillation signal), and an LO signal (local oscillation) from the original vibration signal from the original vibration signal generator 21. A first LO signal generation unit 22 that generates a signal), a first mixer 23 that converts an RF signal from a radio base station into an IF signal by the LO signal generated by the first LO signal generation unit 22; The modulation unit 24 that modulates the original oscillation signal generated by the original oscillation signal generation unit 21 by the control signal from the radio base station 1, the IF signal output from the first mixer 23, and the original oscillation modulated by the modulation unit 24 A multiplexer 25 that combines the signals, and an E / O unit (electric / optical converter) that converts the combined signal combined by the combiner 25 from an electrical signal to an optical signal and transmits the optical signal to the optical fiber 4. 26).

  Further, the optical forward base station 3 which is an optical signal receiving device receives an optical signal transmitted through the optical fiber 4 from the optical interface unit 2 and converts it into an electrical signal (optical / electrical conversion unit) 31. A demultiplexer 32 that demultiplexes the electrical signal output from the O / E unit 31 into an IF signal and a modulated original oscillation signal, and an original obtained by removing a modulation component from the modulated original oscillation signal. A demodulator 33 that generates an oscillation signal and a control signal obtained by demodulating the modulated original oscillation signal; a second LO signal generator 34 that generates an LO signal (local oscillation signal) from the original oscillation signal; The second mixer 35 that converts the IF signal input from the duplexer 32 into an RF signal using the LO signal generated by the second LO signal generator 34 and the control demodulated by the demodulator 33 The gain is controlled by the signal and output from the second mixer 35 It amplifies the F signal and an amplifier 36 to be output to the antenna 5.

  Next, the operation of the optical signal transmission system shown in FIG. 1 will be described. The RF signal output from the radio base station 1 is input to the optical interface unit 2. In the optical interface unit 2, this RF signal is input to the first mixer 23. Then, the first mixer 23 converts the input RF signal into an IF signal using the LO signal generated by the first LO signal generator 22 from the original signal from the original signal generator 21.

  On the other hand, the modulation unit 24 modulates the original vibration signal generated by the original vibration signal generation unit 21 based on the control signal output from the radio base station 1. Then, the multiplexer 25 multiplexes the original signal whose control signal is modulated by the modulation unit 24 and the IF signal output from the first mixer 23. Further, the combined signal of the IF signal and the original signal obtained by modulating the control signal is input to the E / O unit 26 and converted from an electric signal to an optical signal. The combined signal (that is, the original signal obtained by modulating the IF signal and the control signal) is transmitted as an optical signal from the E / O unit 26 through the optical fiber 4 and transmitted to the optical advance base station 3.

  On the other hand, in the optical forward base station 3, the O / E unit 31 converts the received optical signal of the combined signal into an electric signal again and transmits it to the duplexer 32. Further, the demultiplexer 32 demultiplexes the IF signal and the original signal obtained by modulating the control signal. Then, the demodulator 33 extracts the original vibration signal by removing the modulation component from the modulated original vibration signal, and extracts the control signal by demodulating the modulated original vibration signal. Further, the original vibration signal from which the modulation component has been removed is input to the second LO signal generator 34. Then, the second LO signal generator 34 generates an LO signal.

  Next, the second mixer 35 converts the IF signal into an RF signal using the LO signal output from the second LO signal generator 34. Further, the RF signal converted by the mixer 35 is amplified by the amplifier 36 whose gain is controlled by the control signal separated and extracted by the demodulator 33. The RF signal amplified by the amplifier 36 is output from the antenna 5 by radio waves as the original RF signal.

  FIG. 2 is a block diagram illustrating a detailed configuration of the demodulation unit 33 configured in the optical forward base station 3 in the optical signal transmission system illustrated in FIG. Therefore, the configuration and operation of the demodulation unit 33 will be described in more detail with reference to FIG. As shown in FIG. 2, the demodulator 33 includes a carrier recovery circuit 33a that extracts a source signal that is a carrier by removing a modulation component from the source signal that has been modulated with the control signal, and a source signal that has been modulated with the control signal. The phase detection circuit 33b that separates and extracts the components of the control signal by comparing the phase of the signal and the carrier wave (original oscillation signal) output from the carrier recovery circuit 33a, and the component of the control signal output from the phase detection circuit 33b And a discriminating / reproducing circuit 33d for outputting a control signal for gain control of the amplifier based on the demodulation timing output from the timing extraction circuit 33c. Has been.

  Next, the operation of the demodulator 33 shown in FIG. 2 will be described with reference to FIG. In the demodulator 33, when the original oscillation signal modulated by the control signal is input to the carrier wave reproduction circuit 33a, the carrier wave reproduction circuit 33a extracts the original oscillation signal by removing the control signal that is the modulation component. Output a signal. As shown in FIG. 1, the original oscillation signal output from the carrier recovery circuit 33a is input to the second LO signal generator 34 and converted into an LO signal to become a carrier wave. Alternatively, the original oscillation signal output from the carrier recovery circuit 33a can be output as a carrier as it is.

  Further, the original oscillation signal whose control signal is modulated is input to the phase detection circuit 33b, and the phase of the original oscillation signal is compared with the carrier wave (original oscillation signal) input from the carrier wave recovery circuit 33a to the phase detection circuit 33b. Are extracted separately. The component of the control signal separated / extracted by the phase detection circuit 33b is output as a control signal for controlling the gain of the amplifier by the identification / reproduction circuit 33d based on the demodulation timing from the timing extraction circuit 33c. That is, the control signal output from the identification / reproduction circuit 33d is input to the amplifier 36 to control the amplification factor of the RF signal, as shown in FIG.

<Embodiment 2>
FIG. 3 is a block diagram showing a configuration of the optical signal transmission system according to Embodiment 2 of the present invention. The optical signal transmission system of the second embodiment shown in FIG. 3 is different from the optical signal transmission system of the first embodiment shown in FIG. 1 in that the multiplexer 25 of the optical interface unit 2a on the optical signal transmission device side is Rather than modulating the original signal and combining with the IF signal, the LO signal is modulated and combined with the IF signal, and the demodulator 39 of the optical forward base station 3a on the optical signal receiving device side Instead of extracting the original vibration signal by removing the modulation component from the original vibration signal modulated with the control signal, the LO signal as the carrier wave is extracted by removing the modulation component from the original vibration signal modulated with the control signal. It is that you are.

  That is, the optical signal transmission system of the second embodiment shown in FIG. 3 is different from the optical signal transmission system of the first embodiment shown in FIG. 1 in the configuration of the optical interface unit 2a that is an optical signal transmission device. The modulation unit 29 modulates the LO signal generated by the first LO signal generation unit 22 by the control signal from the radio base station 1, and transmits the modulated LO signal to the multiplexer 25; In the configuration of the optical forward base station 3a, which is a device, the demodulator 39 removes the modulation component from the modulated LO signal of the control signal and separates and demodulates the LO signal and the control signal. In this way, the demodulator 39 demodulates the LO signal, and the second mixer 35 combines the IF signal and the LO signal to generate an RF signal.

<Summary>
As described above, according to the optical signal transmission system of the present invention, the original signal or the LO signal is used as the carrier wave for transmitting the control signal in the optical signal transmission apparatus. As a result, the frequency bandwidth occupied by the optical transmission signal is narrowed, so that the circuit configuration is simplified and inexpensive optical components can be used. Further, in the optical signal receiving apparatus, the control signal and the original oscillation signal or the LO signal are separated and extracted by the demodulator. Thereby, the optical transmission signal transmitted in a narrower transmission band can be returned to the original RF signal. In addition, by transmitting the LO signal by applying a modulation signal, the circuit configuration is simplified, and inexpensive optical components can be used.

  According to the optical signal transmission system of the present invention, since the control signal is transmitted using the original oscillation signal or the LO signal as a carrier wave, the optical signal can be transmitted in a narrow frequency band. Therefore, since the circuit configuration is simplified, a general-purpose and inexpensive optical component can be used, so that it can be effectively used as a low-cost wireless transmission device, wireless reception device, or wireless communication system.

1 is a block diagram showing a configuration of an optical signal transmission system according to Embodiment 1 of the present invention. The block diagram which shows the detailed structure of the demodulation part of the optical advance base station in the optical signal transmission system shown in FIG. The block diagram which shows the structure of the optical signal transmission system in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radio base station 2, 2a Optical interface part 3, 3a Optical advance base station 4 Optical fiber 5 Antenna 21 Original vibration signal generation part 22 1st LO signal generation part 23 1st mixer 24, 29 Modulation part 25 Multiplexer 26 E / O section (electrical / optical conversion section)
31 O / E section (optical / electrical converter)
32 Demultiplexer 33, 39 Demodulator 33a Carrier recovery circuit 33b Phase detection circuit 33c Timing extraction circuit 33d Identification recovery circuit 34 Second LO signal generator 35 Second mixer 36 Amplifier

Claims (4)

An original vibration signal generating means for generating an original vibration signal;
First LO signal generating means for generating an LO signal from the original vibration signal generated by the original vibration signal generating means;
A first mixer for converting an RF signal into an IF signal using the LO signal generated by the first LO signal generating means;
Modulation means for modulating the original vibration signal generated by the original vibration signal generation means based on the input control signal;
Combining means for combining the IF signal output from the first mixer and the original signal modulated by the modulating means;
An optical signal transmission device comprising: an electrical / optical conversion unit that converts the combined signal combined by the combining unit from an electrical signal to an optical signal. Optical / electrical conversion means for converting an optical signal received from the optical signal transmission device according to claim 1 into an electrical signal;
A demultiplexing unit that demultiplexes the electric signal output from the optical / electrical conversion unit into an IF signal and a modulated original oscillation signal;
Demodulating means for generating an original oscillation signal obtained by removing a modulation component from a modulated original oscillation signal and a control signal obtained by demodulating the modulated original oscillation signal;
Second LO signal generating means for generating an LO signal from the original vibration signal;
A second mixer that converts the IF signal input from the demultiplexing means into an RF signal using the LO signal generated by the second LO signal generating means;
An optical signal receiving apparatus comprising: amplification means for controlling a gain by a control signal demodulated by the demodulation means and amplifying and outputting an RF signal output from the second mixer. An original vibration signal generating means for generating an original vibration signal;
First LO signal generating means for generating an LO signal from the original vibration signal generated by the original vibration signal generating means;
A first mixer that converts the RF signal into the IF signal using the LO signal generated by the first LO signal generating means;
Modulation means for modulating the LO signal generated by the first LO signal generation means based on the input control signal;
Combining means for combining the IF signal output from the first mixer and the LO signal modulated by the modulating means;
An optical signal transmission device comprising: an electrical / optical conversion unit that converts the combined signal combined by the combining unit from an electrical signal to an optical signal. Optical / electric conversion means for converting an optical signal received from the optical signal transmission device according to claim 3 into an electrical signal;
Demultiplexing means for demultiplexing the electrical signal output from the optical / electrical conversion means into an IF signal and a modulated LO signal;
Demodulation means for generating an LO signal obtained by removing a modulation component from the modulated LO signal and a control signal obtained by demodulating the modulated LO signal;
A second mixer for converting the IF signal input from the demultiplexing means into an RF signal using the LO signal generated by the demodulation means;
An optical signal receiving apparatus comprising: amplification means for controlling a gain by a control signal demodulated by the demodulation means and amplifying and outputting the RF signal outputted from the second mixer.

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