JPH11103288A - Light transmitter/receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and inexpensively constitute a light transmitter/receiver. SOLUTION: A modulated electric signal Smod generated by modulating the amplitude of a high frequency (millimeter wave band) subcarrier by a base band signal SBB to be transmitted and a main carrier MC outputted from a light source 110 are inputted to an external light modulation part 120 in a light transmitter 101. The modulation part 120 modulates the amplitude of the main carrier MC by the signal Smod and outputs a double modulated optical signal OSdmod to an optical filter part 130. The filter part 130 transmits only one side band wave component included in the signal OSdmod and projects the transmitted signal to an optical fiber 140 as an optical signal OS. A photoelectric conversion part 150 in a light receiver 102 directly obtains a base band signal SBB by photoelectrically converting the optical signal OS transmitted through the fiber 140.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitting / receiving apparatus, and more particularly, to an optical transmitting / receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to enable optical transmission.

[0002]

2. Description of the Related Art Optical transmission, in which information is transmitted on light, is expected to be widely used in future high-speed communication networks because of its low loss and wide bandwidth. For example, an optical transceiver for optically transmitting an electrical high-frequency signal (hereinafter, referred to as a first optical transceiver) and an optical transceiver for optically transmitting a baseband signal (hereinafter, referred to as a second optical transceiver). Etc.) have been proposed. Hereinafter, these two optical transceivers will be specifically described with reference to the drawings.

[0003] First, a first optical transmitting / receiving apparatus will be described. In recent years, mobile phones or PHS (Personal Handyphone S)
ystem) are rapidly expanding. Therefore, utilization of higher frequencies is being studied, and a microcell system or a picocell system using a millimeter wave band of about 30 GHz to 300 GHz is being studied. In such a cell system, high-frequency signals in the millimeter wave band are radiated from a large number of wireless base stations connected to the control station,
Wireless service is provided. This cell system has various advantages. First, since signals in the millimeter wave band have a large propagation loss in space, they do not easily adversely affect adjacent cells. Secondly, since signals in the millimeter wave band have a short wavelength, the size of an antenna or the like installed in a control station or the like is reduced. Third, since the signal in the millimeter wave band has a high frequency, the transmission capacity can be increased. As a result, there is a possibility that a high-speed transmission service that cannot be realized by the conventional wireless service can be provided.

However, in a radio communication system to which such a cell system is applied, many radio base stations are installed in a town. Therefore, the wireless base station is required to be small and inexpensive. Therefore, a first optical transmission / reception device employing a so-called subcarrier optical transmission system, which has been actively researched and developed in recent years, may be applied to a wireless communication system. As for the subcarrier optical transmission system, for example, "Microwave and millimeter-wave f
iber optic technologies for subcarrier transmissio
n systems "(Hiroyo Ogawa, IEICE Transactions on Com
munications, Vol.E76-B, No.9, pp1078-1090, Septem
ber, 1993). In this subcarrier optical transmission system, the intensity of a main carrier, which is typically a non-modulated light, is modulated by a modulated signal obtained by putting information of an audio signal and / or a video signal on a subcarrier, thereby Is obtained. The change in the intensity of this optical signal is
It uniquely corresponds to a change in amplitude, a change in frequency, or a change in phase of the modulation signal. In the subcarrier optical transmission system, since an optical fiber with a very low loss is used, if the modulated signal is in the millimeter wave band, the modulated signal can be transmitted as it is to a remote place.

FIG. 17 is a block diagram showing a configuration of a typical first optical transmission / reception apparatus. In FIG.
The first optical transceiver includes a light source 110 and an external light modulator 12.
0, an optical fiber 140, a photoelectric conversion unit 150, a frequency conversion unit 1710, and a demodulation unit 1720. The light source 110 and the external optical modulator 120 constitute an optical transmitter 101 and constitute a wireless base station, and the photoelectric converter 150, frequency converter 1710 and demodulator 1720 constitute an optical receiver 102. Installed at the control station. However, FIG. 17 shows a configuration related to only a signal path in one direction, that is, a configuration related to only a signal path transmitted from a wireless base station to a control station. In the first optical transceiver, the electric signal to be transmitted from the radio base station to the control station is typically a millimeter wave band in which a baseband signal such as an audio signal and / or a video signal is put on a subcarrier. This is an electric modulation signal S _mod . The electric modulation signal S _mod is transmitted from a mobile phone or a PHS terminal or the like moving outside the radio base station via an antenna or an amplifier (not shown) to the optical transmitter 1.
01 is input to the external light modulator 120. Light source 1
Reference numeral 10 oscillates unmodulated light as a main carrier MC, and the main carrier MC is also input to the external light modulator 120. The external light modulation unit 120 performs external light intensity modulation, and converts the intensity of the input main carrier MC into the input electric modulation signal S
Modulation is performed based on a change in the amplitude of the _mod , whereby an optical signal OS _mod is obtained. This optical signal OS _mod emitted from the external optical modulator 120 to the optical fiber 140 is:
The carrier itself becomes a carrier wave, and enters the photoelectric conversion unit 150 of the optical receiver 102 while carrying the electric modulation signal S _mod as it is through the optical fiber 140. The photoelectric conversion unit 150 performs photoelectric conversion to convert the incident optical signal OS _mod into an electric signal including the intensity modulation component. The frequency conversion unit 1710 includes the photoelectric conversion unit 150
Is down-converted into an intermediate frequency band electric signal. The demodulation unit 1720 demodulates information of a baseband signal such as an audio signal and / or a video signal based on the intermediate frequency band electric signal input from the frequency conversion unit 1710.

[0006] Next, a second optical transmission of the baseband signal is performed.
The optical transmitting and receiving device will be described. FIG. 18 is a block diagram showing a configuration of a typical second optical transmission / reception device. In FIG. 18, the second optical transmitting / receiving device includes a light source driving unit 181
0, a light source 110, an optical fiber 140, and a photoelectric conversion unit 150. Among them, the light source driving unit 1810 and the light source 110 constitute the light transmitting device 101, and the photoelectric conversion unit 150 constitutes the light receiving device 102. In the second optical transmitter-receiver, the baseband signal S _BB to be transmitted from the optical transmitter 101 to the optical receiver 102 is assumed to digital information such as voice signals and / or video signals.
The baseband signal _SBB is input to the light source driving unit 1810. The light source driving unit 1810 drives the light source 110,
The intensity of the optical signal output from the light source 110,
Modulation is performed based on the input baseband signal _SBB (direct light modulation method). This optical signal is transmitted to the optical fiber 140
After being transmitted through the inside, photoelectric conversion is performed by the photoelectric conversion unit 150, whereby the original baseband signal _SBB is obtained. Such an optical transmission technology is common, and is described in, for example, Chapter 2 “Practical Optical Communication System” of “Optical Communication Technology Reader” (edited by Shimada, published by Ohmsha) published in 1980. I have.

[0007] However, the photoelectric conversion unit 150 and the frequency conversion unit 1710 shown in FIG. 17 are required to accurately perform the photoelectric conversion and the frequency conversion of the high-frequency signal in the millimeter wave band, and are required to have a wide band. Otherwise, the demodulation unit 1720 cannot perform accurate demodulation processing. Therefore,
In the first optical transmission / reception device, electric components corresponding to a high frequency band are connected to each other. For this connection, a dedicated connector, a waveguide or a semi-rigid cable is used. Since it is difficult to freely process the waveguide and the semi-rigid cable, there is a problem that it is difficult to manufacture the first optical transceiver. Also, when trying to transmit high-frequency electrical signals such as millimeter-wave bands with low loss,
Although it is necessary to use a waveguide, the size of the waveguide is larger than that of a coaxial cable, and thus there is a problem that the scale of the first transmitting / receiving device is increased.

[0008]

As described above, the second
Optical transceiver unit (see FIG. 18) is often used to transmit a baseband signal S _BB of digital information by wire. On the other hand, it has been studied that the first optical transmitting / receiving device (see FIG. 17) is applied to a wireless communication system. As described above, since the first and second optical transmission / reception devices have different applications, they are considered as separate systems. For an optical transmission / reception device that simultaneously transmits both the baseband signal and the high-frequency electric signal, the optical transmission / reception device is not so much used. Had not been considered. However, if the wavelength multiplexing technique is used, such an optical transmitting and receiving apparatus can be constructed. That is, the optical signal output from the light source 110 in FIG. 18 and the optical signal output from the external optical modulator 120 in FIG. 17 are wavelength-multiplexed on the transmission side. The resulting wavelength multiplexed signal is transmitted in the optical fiber 140, separated at the optical receiving side, and then subjected to separate opto-electric conversion, whereby the receiving side can obtain both signals at the same time. However, since the optical transmitting and receiving apparatus to which the wavelength multiplexing technique is applied must separate the wavelength-multiplexed optical signal accurately on the optical receiving side, the transmitting side requires a plurality of light sources 110 having different oscillation wavelengths from each other. There is a problem in that the construction of the optical transmission / reception device requires a considerable cost.

[0009] US Pat. No. 5,596,436 discloses an optical transmitting / receiving apparatus to which a subcarrier multiplexing optical transmission system is applied, which looks similar to some of the optical transmitting / receiving apparatuses disclosed in the present application. There are parts that are. However, in the optical transmitting and receiving apparatus according to this US patent, first, each electric modulation signal is generated by modulating each subcarrier in each mixer and each baseband signal in each mixer. The multiplexed signal is output to combiner 4
0 is generated by multiplexing each electric modulation signal. The external light modulator 46 modulates the unmodulated light from the laser 44 with the multiplexed signal. The optical transmission device according to the above-mentioned U.S. Patent is different from the optical transmission device 101 of the present application in the configuration. That is, although one subcarrier is used in the optical transmission device 101 of the present application, a plurality of subcarriers are used in the optical transmission device according to the above-mentioned US patent. Therefore, the spectrums of the optical signals emitted from both optical transmitters are different from each other, and in the optical signal according to the above-mentioned U.S. Patent, the components of the main carrier and the components of each sub-carrier are close to each other on the optical frequency axis. However, in the optical signal OS (described later) according to the present application, the component of the main carrier and the component of the double-sided band do not approach each other. Thereby, the optical receiving device according to the present application is:
A remarkable technical effect that the components of the baseband signal _SBB can be easily and accurately extracted as compared with the above-mentioned U.S. Pat.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical transceiver capable of optically transmitting an electrical high-frequency signal, and which is simple to manufacture and small in size. . Another object of the present invention is to
It is an object of the present invention to provide an optical transmitting and receiving apparatus that can simultaneously transmit both a baseband signal and a high-frequency signal using the same light source.

[0011]

A first aspect of the present invention is directed to an optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein the optical transmitting apparatus and the optical receiving apparatus are modulated with an electric signal to be transmitted. The sub-carrier is input from the outside, and the main carrier, which is unmodulated light having a constant optical frequency, is double-modulated by the input sub-carrier to generate and output a double-modulated optical signal. The optical spectrum of the double-modulated optical signal input from the dual-modulation unit includes a main carrier component at a position of a constant optical frequency, and further a position separated by a subcarrier frequency from the constant optical frequency. Selects an optical signal containing either the upper band or the lower band from the double-modulated optical signal that contains the upper band and lower band components and is input from the double modulator. Optical filter section, An optical-to-electrical conversion unit that obtains an electrical signal to be transmitted by photoelectrically converting an optical signal input from the unit, the optical transmission device includes at least a local oscillation unit and a double modulation unit, The optical receiving device includes at least a photoelectric conversion unit, and the optical filter unit is included in one of the optical transmitting device and the optical receiving device. According to the first aspect, the opto-electric conversion unit can directly obtain an electric signal to be transmitted at a relatively low frequency from the optical signal. There is no need for expensive and difficult-to-process electrical components corresponding to the subcarrier band of a high frequency.
Further, with this, it is possible to easily configure the optical receiving device at low cost.

According to a second aspect, in the first aspect, the double modulating section is configured to input a semiconductor laser that outputs a main carrier wave and a main carrier wave that is input from the semiconductor laser by an external light modulation method, from the outside. And at least one external light modulator for amplitude-modulating a subcarrier amplitude-modulated with an electric signal to be transmitted. According to the second aspect, since the dual modulation section is configured by the existing semiconductor laser and the external light modulation section, the optical transmitting and receiving apparatus is constructed at low cost.

According to a third aspect, in the second aspect, the subcarrier amplitude-modulated with the electric signal to be transmitted is a signal transmitted wirelessly from the outside, and receives the signal transmitted wirelessly. And an antenna unit for supplying the dual modulation unit. According to the third aspect, the optical transceiver is easily connected to the wireless transmission system by including the antenna unit that receives a signal wirelessly transmitted from the outside.

According to a fourth aspect, in the third aspect, the electric signal to be transmitted is a frequency-multiplexed multi-channel signal, and the electric modulation section is a multi-channel signal.
It is characterized in that a modulated electric signal is generated and output by amplitude-modulating the input sub-carrier. According to the fourth aspect, the optical transceiver can optically transmit a large amount of information.

According to a fifth aspect, in the third aspect, the electric signal to be transmitted is digital information, and the electric modulation section performs on / off keying of the subcarrier with the digital information. According to the fifth aspect, the optical transceiver can transmit high-quality information.

A sixth aspect is an optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein a subcarrier modulated by an electric signal to be transmitted is inputted from the outside, and is fixed. The main carrier, which is unmodulated light having an optical frequency,
By doubly modulating with the input subcarrier,
A dual-modulation unit that generates and outputs a double-modulated optical signal is provided.The optical spectrum of the double-modulated optical signal input from the double-modulation unit includes a main carrier component at a position of a constant optical frequency, and The upper band and the lower band are included in the position of the upper band and the lower band at a position separated from the optical frequency by the frequency of the subcarrier. An optical filter unit for selectively passing an optical signal containing either one of the components; and an optical branching unit for splitting an optical signal input from the optical filter unit into a first optical signal and a second optical signal and outputting the first optical signal and the second optical signal. A first optical-to-electrical conversion unit for obtaining an electrical signal to be transmitted by photoelectrically converting a first optical signal input from the optical branching unit, and a photoelectric conversion for the second optical signal input from the optical branching unit Second light for outputting an electric signal obtained as a detection signal A gas conversion unit, and at a predetermined time interval, detect an average value of the detection signal input from the second photoelectric conversion unit, and output the signal from the double modulation unit based on the maximum value of the detected average value. A wavelength controller for controlling the wavelength of the double-modulated optical signal, wherein the optical transmitter includes at least a local oscillator and a double modulator, and the optical receiver includes at least a first photoelectric converter. And the optical filter unit is included in one of the optical transmitting device and the optical receiving device. According to the sixth aspect,
As in the first aspect, the optical transmitting / receiving device is configured simply and at low cost while eliminating the need for expensive and difficult-to-process electric components corresponding to the relatively high frequency subcarrier band.
Further, since the wavelength of the double modulated optical signal is controlled, the optical filter unit can always output an optical signal that can be accurately demodulated.

[0017] A seventh aspect is the optical transmission device and the first and second optical transmission devices.
An optical transmitting and receiving device connected to the optical receiving device so as to be capable of optical transmission, wherein the optical transmitting device outputs a local oscillation unit that outputs a subcarrier having a constant frequency, and a main carrier that is unmodulated light having a constant optical frequency. An electrical signal to be transmitted from the outside and a dual modulation unit that generates and outputs a double modulated optical signal by performing double modulation with a subcarrier input from a local oscillation unit, The spectrum of the double-modulated optical signal output from the dual-modulation unit has a main carrier component at a position of a constant optical frequency, and an upper band and a lower band at a position further away from the constant optical frequency by a subcarrier frequency. The optical transmitter includes a first optical signal that includes one of the upper band and the lower band, and converts the double modulated optical signal that is input from the double modulator into a first optical signal that includes one of the upper band and the lower band. Carrier components and upper and lower sidebands Further comprising an optical filter unit that divides the optical signal into a second optical signal including the other component and outputs the first optical signal and the second optical signal. Obtaining an electric signal to be transmitted by photoelectrically converting the first optical signal that is transmitted;
The second optical receiver receives the second optical signal transmitted from the optical transmitter.
It is characterized in that a signal obtained by modulating a subcarrier with an electric signal to be transmitted is obtained by photoelectrically converting an optical signal.
The first optical signal includes one sideband component included in the double-modulated double-modulated optical signal, and is to be transmitted by being photoelectrically converted by the first photoelectric conversion unit. Converted to electrical signals. Further, the second optical signal is
The other sideband and the main carrier component of the doubly modulated doubly modulated optical signal are included. Is converted to a modulated signal. As described above, according to the seventh aspect, the receiving side can simultaneously obtain both an electric signal to be transmitted and a signal obtained by modulating a subcarrier with the electric signal. Further, as apparent from the above description, since both signals can be transmitted by one unmodulated light wave, a plurality of light sources are not required unlike the wavelength multiplexing technique. The transmitting and receiving device can be constructed at low cost.

According to an eighth aspect, in the seventh aspect, the optical filter section comprises: an optical circulator section for directly outputting the double modulated optical signal input from the double modulation section; Of the doubly modulated optical signal, a first optical signal is generated by reflecting one of the upper band wave and the lower band wave and output to the optical circulator unit, and the component of the main carrier wave and the upper band wave And an optical fiber grating section that generates a second optical signal by transmitting one of the other components of the lower sideband and outputs the generated second optical signal to the second optical receiver. The optical circulator section further includes:
The first optical signal input from the optical fiber grating is output as it is to the first optical receiver. In the eighth aspect, since the optical filter section includes the optical circulator and the optical fiber grating, which are existing optical components, the optical transmitting and receiving apparatus is configured simply and at low cost.

The ninth aspect is the seventh aspect, wherein the second aspect is the second aspect.
The optical receiver includes an antenna unit for radiating a signal obtained by modulating a subcarrier with an electric signal to be transmitted obtained by photoelectric conversion into space. The subcarrier modulated with the electric signal to be transmitted is a signal suitable for wireless transmission. Therefore, according to the ninth aspect, the second optical receiver includes the antenna unit that radiates the subcarrier into space, so that the optical transceiver is easily connected to the wireless transmission system.

According to a tenth aspect, in the seventh aspect, the electric signal to be transmitted is obtained by converting analog information into digital information. According to the tenth aspect, the optical transceiver can transmit high-quality information.

According to an eleventh aspect, in the seventh aspect, the electric signal to be transmitted is obtained by multiplexing a plurality of electric signals obtained by modulating an intermediate frequency carrier with analog information or digital information by a predetermined multiplexing method. It is characterized by the following.
In a twelfth aspect based on the eleventh aspect, the predetermined multiplexing method is frequency division multiplex access, time division multiplex access, or code division multiplex access. According to the eleventh and twelfth aspects, the optical transmitting / receiving device can multiplex a large amount of information and transmit the optical information.

A thirteenth aspect is an optical transmitting / receiving apparatus in which an optical transmitting apparatus and first and second optical receiving apparatuses are connected so as to enable optical transmission, wherein the optical transmitting apparatus outputs a subcarrier having a constant frequency. By locally modulating the local oscillator and the main carrier, which is unmodulated light having a constant optical frequency, with an electric signal to be transmitted externally input and a subcarrier input from the local oscillator, A first optical receiving device comprising: a double modulation unit that generates and outputs a double modulation optical signal; and an optical branch unit that splits and outputs a double modulation optical signal input from the double modulation unit. A low-pass filter unit that outputs an electric signal to be transmitted by passing a component included in a low band of the electric signal obtained by performing photoelectric conversion on the double-modulated optical signal transmitted from the transmission device. The second optical receiver is transmitted from the optical transmitter, That the double-modulated optical signal is passed through a component contained in the high-frequency electrical signal obtained by photoelectric conversion,
A high-pass filter unit that outputs a signal obtained by modulating a subcarrier with an electric signal to be transmitted; As in the seventh aspect, the receiving side of the thirteenth aspect may be configured such that the low-pass filter section and the high-pass filter section perform a low-frequency portion And, since the high-pass portion is passed, it is possible to simultaneously obtain a signal obtained by modulating a subcarrier with an electric signal to be transmitted included in a relatively low band and an electric signal to be transmitted included in a relatively high band, Further, the optical transceiver can be constructed at low cost.

A fourteenth aspect is an optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein the optical transmitting apparatus outputs a sub-oscillator having a constant frequency, By modulating the main carrier, which is unmodulated light having a constant optical frequency, with an externally input electric signal to be transmitted and a subcarrier input from a local oscillator, a double modulated optical signal is obtained. An optical-to-electrical conversion unit for generating and outputting a signal, wherein the optical receiving device photoelectrically converts the double-modulated optical signal transmitted from the optical transmitting device and outputs an electric signal; A distribution unit that distributes at least two electric signals input from the conversion unit, and a low-pass filter that outputs an electric signal to be transmitted by passing a component included in a low band of the electric signal distributed by the distribution unit Division and distribution section By passing the component contained in the high band of the electrical signal, and a high pass filter section for outputting a signal obtained by modulating the subcarrier by an electrical signal to be transmitted. As in the seventh aspect, the receiving side of the fourteenth aspect may be configured such that the low-pass filter section and the high-pass filter section perform the low-frequency portion of the electrical signal obtained by performing the photoelectric conversion of the double modulated optical signal. And, since the high-pass portion is passed, it is possible to simultaneously obtain a signal obtained by modulating a subcarrier with an electric signal to be transmitted included in a relatively low band and an electric signal to be transmitted included in a relatively high band, Further, the optical transceiver can be constructed at low cost.

The fifteenth aspect is the seventh, thirteenth or fourteenth aspect.
In the aspect of the above, the dual modulation unit, the electric signal to be transmitted from the outside, by amplitude-modulating the sub-carrier input from the local oscillation unit, an electric modulation unit that generates and outputs a modulated electric signal A light source that outputs a main carrier that is an unmodulated light having a constant optical frequency, and a modulated electric signal that is input from an electric modulation unit, and amplitude-modulates the main carrier that is input from the light source, thereby generating a double-modulated optical signal. And an external light modulation unit that generates According to the fifteenth aspect, the optical transmitter uses the same light source to simultaneously transmit the electric signal to be transmitted and the signal obtained by modulating the subcarrier with the same to the receiving side. As a result, the optical transceiver is constructed at low cost.

[0025] A sixteenth aspect is a method according to the fifteenth aspect, wherein
The electric signal to be transmitted is digital information, and the electric modulation unit performs on / off keying of the subcarrier with the digital information. According to the sixteenth aspect, the optical transceiver includes:
High quality information can be transmitted.

The seventeenth aspect is the seventh, thirteenth or fourteenth aspect.
In the aspect, the dual modulation section amplitude-modulates the main carrier input from the light source with a light source that outputs a main carrier that is unmodulated light having a constant optical frequency and a subcarrier input from a local oscillation section. Accordingly, by modulating the amplitude of the modulated optical signal input from the first external optical modulator with the first external optical modulator for generating and outputting the modulated optical signal and the electric signal to be transmitted input from the outside, , A second external optical modulator for generating a double modulated optical signal.

The eighteenth aspect is the seventh, thirteenth, or fourteenth aspect.
In the aspect, the dual modulation unit outputs a main carrier that is a non-modulated light having a constant optical frequency, and an electric signal to be transmitted input from the outside, and amplitude-modulates the main carrier input from the light source. By modulating the amplitude of the modulated optical signal input from the first external optical modulator with the first external optical modulator for generating and outputting the modulated optical signal and the subcarrier input from the local oscillator. , A second external optical modulator for generating a double modulated optical signal. According to the seventeenth and eighteenth aspects, the optical transmitter uses the same light source to simultaneously transmit the electric signal to be transmitted and the signal obtained by modulating the subcarrier with the same to the receiving side. As a result, the optical transceiver is constructed at low cost.

According to a nineteenth aspect, in the thirteenth or fourteenth aspect, the double modulating section modulates the main carrier with the sub-carrier input from the local oscillation section by a single sideband amplitude modulation method. Features. According to the nineteenth aspect, by applying the single sideband amplitude modulation method, a double-modulated optical signal is less affected by chromatic dispersion in an optical fiber as an optical transmission path, and the transmission distance is increased. .

According to a twentieth aspect, there is provided an optical transmitting and receiving apparatus in which an optical transmitting apparatus and first and second optical receiving apparatuses are connected to be capable of optical transmission, wherein the optical transmitting apparatus outputs a subcarrier having a constant frequency. A local oscillator, a mode-locked light source that is mode-locked based on a sub-carrier input from the local oscillator, oscillates at an optical frequency interval related to the sub-carrier, and generates and outputs a mode-locked optical signal; An external light modulator that generates and outputs a double-modulated optical signal by amplitude-modulating a mode-locked optical signal input from a mode-locked light source with an electric signal to be transmitted input from the outside,
An optical splitter for splitting and outputting a double-modulated optical signal input from the external optical modulator, wherein the first optical receiver converts the double-modulated optical signal transmitted from the optical transmitter into an optical-electrical signal. A low-pass filter unit that outputs an electric signal to be transmitted by passing a component included in a low band of the electric signal obtained by the second transmission, and the second optical receiver is transmitted from the optical transmitter. A high-pass filter unit that outputs a signal obtained by modulating a sub-carrier with an electric signal to be transmitted by passing a component included in a high band of an electric signal obtained by photoelectrically converting a double-modulated optical signal. . The receiving side of the twentieth aspect is characterized in that, similar to the seventh aspect, the low-pass filter unit and the high-pass filter unit are configured to perform a low-pass portion of an electric signal obtained by photoelectrically converting the double modulated optical signal. And, since the high-pass portion is passed, it is possible to simultaneously obtain a signal obtained by modulating a subcarrier with an electric signal to be transmitted included in a relatively low band and an electric signal to be transmitted included in a relatively high band, Further, the optical transceiver can be constructed at low cost.

A twenty-first aspect is an optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein the optical transmitting apparatus outputs a local oscillator that outputs a subcarrier having a constant frequency; A mode-locked light source that generates and outputs a mode-locked optical signal by being mode-locked based on the sub-carrier input from the local oscillator and oscillating at an optical frequency interval related to the sub-carrier, and input from the outside An external optical modulation unit that generates and outputs a double-modulated optical signal by amplitude-modulating a mode-locked optical signal input from a mode-locked light source with an electric signal to be transmitted; A photoelectric conversion unit that photoelectrically converts the double-modulated optical signal transmitted from the photoelectric conversion unit and outputs an electric signal; a distribution unit that distributes at least two electric signals input from the photoelectric conversion unit; A low-pass filter unit that outputs an electric signal to be transmitted by passing a component included in a low band of the electric signal distributed by the filter unit, and a component included in a high band of the electric signal distributed by the distribution unit. A high-pass filter unit that outputs a signal obtained by modulating a subcarrier with an electric signal to be transmitted by passing the signal. The second
In the receiving side of the first aspect, the low-pass filter section and the high-pass filter section perform, similarly to the seventh aspect, the low-pass portion and the high-pass portion of the electric signal obtained by performing the photoelectric conversion of the double modulated optical signal. Since the band portion is passed, it is possible to simultaneously obtain a signal obtained by modulating a subcarrier with an electric signal to be transmitted included in a relatively low band and an electric signal to be transmitted included in a relatively high band, An optical transceiver can be constructed at low cost.

A twenty-second aspect is an optical transmission / reception device in which an optical transmission device and an optical reception device are connected to be capable of optical transmission, wherein the optical transmission device outputs a first unmodulated light having a first optical frequency. A first light source, and an external light modulator that generates and outputs a modulated optical signal by amplitude-modulating a first unmodulated light input from the first light source with an electric signal to be transmitted input from the outside. A second optical frequency different from the first optical frequency by a predetermined optical frequency.
A second light source that outputs a second unmodulated light having an optical frequency;
The modulated optical signal input from the external optical modulator and the second unmodulated light input from the second light source are combined so that the polarizations of the modulated optical signal and the second unmodulated light match. The first optical receiver includes an optical multiplexing unit that generates and outputs an optical signal, and an optical branching unit that splits and outputs an optical signal input from the optical multiplexing unit. A low-pass filter unit that outputs an electric signal to be transmitted by passing a component included in a low band of the electric signal obtained by performing photoelectric conversion on the received optical signal. By passing a component included in a high band of an electric signal obtained by performing optical-to-electric conversion on an optical signal transmitted from an optical transmitting apparatus, a signal obtained by modulating a subcarrier with an electric signal to be transmitted is output. A band-pass filter unit;

A twenty-third aspect is an optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein the optical transmitting apparatus outputs a first unmodulated light having a first optical frequency. A first light source, and an external light modulator that generates and outputs a modulated optical signal by amplitude-modulating a first unmodulated light input from the first light source with an electric signal to be transmitted input from the outside. A second optical frequency different from the first optical frequency by a predetermined optical frequency.
A second light source that outputs a second unmodulated light having an optical frequency;
The modulated optical signal input from the external optical modulator and the second unmodulated light input from the second light source are combined so that the polarizations of the modulated optical signal and the second unmodulated light match. By doing so, an optical multiplexing unit that generates and outputs an optical signal, and an optical branching unit that splits and outputs an optical signal input from the optical multiplexing unit, the optical receiving device is transmitted from the optical transmitting device, An opto-electric conversion unit that opto-electrically converts an incoming optical signal to output an electric signal, a distribution unit that distributes at least two electric signals input from the opto-electric conversion unit, and a low-frequency band of the electric signal distributed by the distribution unit And a low-pass filter unit that outputs an electric signal to be transmitted by passing components included in the electric signal to be transmitted by passing components included in a high band of the electric signal distributed by the distribution unit. Outputs a signal obtained by modulating a subcarrier with a signal And a high-pass filter.
According to the twenty-second and twenty-third aspects, a modulated optical signal is generated by amplitude-modulating the first unmodulated light with the electrical signal to be transmitted. The modulated optical signal is combined with the second unmodulated light to generate an optical signal. For example, the seventh
In the aspect described above, the electro-optical conversion needs to be performed twice, but the optical transmitter of this aspect performs the electro-optical conversion only once. Thus, by reducing the number of times of the electro-optical conversion, low-loss optical transmission can be realized. Further, the optical transmission device of this aspect does not require an electric component for amplitude-modulating the subcarrier with an electric signal to be transmitted. In other words, according to the present aspect, there is no need for expensive and difficult-to-process electrical components corresponding to the subcarrier band having a relatively high frequency. Along with this, it is possible to configure the optical transmitting and receiving device easily and at low cost.

According to a twenty-fourth aspect, in any one of the thirteenth, fourteenth, and twentieth to twenty-third aspects, a transmission output from the high-pass filter is provided downstream of the high-pass filter. An antenna unit for radiating a signal obtained by modulating a subcarrier with a power signal to space into a space is provided. According to the twenty-fourth aspect, similarly to the thirteenth aspect, the optical transmitting / receiving device is easily connected to the wireless transmission system.

The twenty-fifth aspect is the seventh, thirteenth, fourteenth,
And in any one of the twentieth to twenty-third aspects, the electric signal to be transmitted is obtained by modulating a carrier of an intermediate frequency having a lower frequency than a subcarrier output from the local oscillator with analog information or digital information. Characterized in that: When the electric signal to be transmitted is an electric signal as described above, the receiving side of the optical transmitting and receiving apparatus according to the twenty-fifth aspect modulates a subcarrier with an intermediate frequency carrier modulated with an analog signal or the like. Signal is obtained. As a result, the optical transmission / reception device can perform optical transmission regardless of the modulation format.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a block diagram showing a configuration of an optical transceiver according to a first embodiment of the present invention. FIG.
The optical transmitting and receiving apparatus shown in FIG. 1 is connected to an optical transmitting apparatus 101 and an optical receiving apparatus 102 via an optical fiber 140 so as to enable optical transmission. The optical transmission device 101 includes a light source 110, an external light modulation unit 120, an optical filter unit 130, and an antenna unit 190, and the optical reception device 102 includes a photoelectric conversion unit 1
50 is provided. FIGS. 2 (a-1) to 2 (d-1)
Main parts (a-1) to (d-1) of the optical transceiver shown in FIG.
5 schematically shows the spectrum of the signal at.

The operation of the optical transceiver shown in FIG.
A description will be given based on FIG. 1 and FIG. In the optical transmission apparatus 101, the antenna section 190 includes a signal (hereinafter, referred to as a modulated electric signal) obtained by amplitude-modulating an electric subcarrier SC having a constant frequency f _{0 with} a baseband signal S _BB to be transmitted having a frequency f _1. S _mod ) is wirelessly transmitted from outside. The antenna unit 190 receives the modulated electric signal S _mod and outputs it to the external light modulation unit 120. Now, _let the current waveform of the baseband signal SBB be I (t). Also,
This amplitude modulation, and has been performed by the modulation index m _d. Then, the voltage waveform V _d (t) of the modulated electric signal S _mod
Is represented by the following equation (1). _{V d (t) = (1} + m d I (t)) cos (ω 0 t) ... (1) here, is ω ₀ = 2πf _0. Also, (1 + m _d I
(T)) and D (t), the above equation (1) becomes the following equation (2)
It is represented by V _d (t) = D (t) cos (ω ₀ t) (2)

The light source 110 is typically composed of a semiconductor laser, oscillates unmodulated light having a constant optical frequency ν as shown in FIG. 2 (a-1), and outputs this as a main carrier MC. . The external light modulator 120 has, for example, a Mach-Zehnder type configuration, and modulates the amplitude of the main carrier MC input from the light source 110 with the modulated electric signal S _mod input from the antenna 190, thereby performing double modulation. (Hereinafter, referred to as a double modulated optical signal OS _dmod ). More specifically, the Mach-Zehnder type external optical modulator 120 firstly receives the input main carrier MC
Is branched into two. One of the branched main carriers MC is optically phase-modulated by the input modulated electric signal S _mod . The main carrier MC that has been optically phase-modulated is multiplexed with the other main carrier MC that is branched, thereby generating the above-mentioned double modulated optical signal OS _dmod . The amplitude change of the double-modulated optical signal OS _dmod uniquely corresponds to the amplitude change of the modulated electric signal S _mod , and the optical spectrum has the center optical frequency ν as shown in FIG. the component of the main carrier MC, further position of integral multiple of the optical frequency f ₀ from the optical frequency [nu (shown only ± f ₀₎ having components of sidebands (upper sideband and lower sideband). The occupied bandwidth of both sideband components is dependent on the frequency f _1.

Next, the electric field intensity waveform E (t) of the double modulated optical signal OS _dmod is expressed by a mathematical formula. The minimum value of the difference between the input voltages when the amplitude of the double modulated optical signal OS _dmod output from the external optical modulator 120 is 0 and the maximum is Vπ And the main carrier MC multiplexed in the external optical modulator 120
And the phase difference between the phase-modulated main carrier MC and π /
Assume it is set to 2. According to this assumption, the double modulated optical signal OS _dmod is represented by the following equation (3).

(Equation 1) Where k = π / 2Vπ And δ ₁ is expressed by the following equation (4).

(Equation 2) For example, the baseband signal S _BB is a sine wave, and its current waveform is I (t) = cos (ω ₁ t) (ω ₁ = 2π
Assuming that f ₁ ), δ ₁ is represented by the following equation (5), and the above equation (3) can be expanded as the following equation (6) by using the following equation (5).

(Equation 3)

(Equation 4) Also, in the above equation (6), the optical frequency ν and the ν, f
Considering the first-order terms of ₁ and f ₀ , the electric field strength waveform E (t) of the double modulated optical signal OS _dmod is finally expressed by the following equation (7).

(Equation 5) Here, J ₀ is a zero-order Bessel function, and J ₁ is a first-order Bessel function.

As described above, the double modulated optical signal OS
_{The dmod} is input to the optical filter unit 130. The pass band of the optical filter unit 130 is set so that only the upper band component or the lower band component can be extracted from the components of the double modulated optical signal OS _dmod shown in FIG. Have been. For example, when the pass band of the optical filter unit 130 is set in the vicinity of the optical frequency ν + f ₀ (see the part surrounded by the dotted line in FIG. 2B-1), only the component of the upper band wave is The light passes through the optical filter section 130 as an optical signal OS. The optical spectrum of the optical signal OS is shown in FIG.
As shown in 1), it has only the same components as the upper band wave, and is included in the optical frequency band near the optical frequency ν + f ₀ .

The electric field intensity waveform E _f (t) of this optical signal OS
Is represented by the following equation (8). When the following equation (8) is arranged, the following equation (9) is obtained.

(Equation 6)

(Equation 7) Here, in the above equations (8) and (9), ω = 2πν, and in the above equation (9), m ′ is represented by the following equation (10), and K is represented by the following equation (11).

(Equation 8)

(Equation 9)

The optical signal OS described above with reference to the formula and FIG. 2C-1 is emitted from the optical filter unit 130 to the optical fiber 140, transmitted by the optical fiber 140, and transmitted by the optical receiving unit 102. The light enters the conversion unit 150. Thus, the optical signal OS is transmitted to a remote place. The photoelectric conversion unit 150 performs photoelectric conversion on the incident optical signal OS and outputs an electrical signal. Referring to FIG. 2 (c-1), the optical signal OS is obtained by amplitude-modulating a carrier having an optical frequency ν + f ₀ with a baseband signal S _BB (= cos 2πf ₁ t) which is information to be transmitted. It can be seen that this is equivalent to Therefore, the current waveform I _pd (t) of the electric signal output from the photoelectric conversion unit 150 is represented by the following equation (12).

(Equation 10) Here, η is the conversion efficiency of the photoelectric conversion unit 150, and I
_pd is a direct current component. As can be understood by referring to the above equation (12), from the output electric signal of the photoelectric conversion unit 150,
If extract only omega ₁ of the component (the component of the frequency f _1), as shown in FIG. 2 (d-1), an amplitude modulation component optical signal OS has found that is a baseband signal S _BB of the current waveform I
(T) will be obtained directly. Incidentally, extracting only the component of the omega ₁ can be easily realized by connecting a band-pass filter in the subsequent stage of the photoelectric conversion unit 150. As described above, the photoelectric conversion unit 150 only needs to have the frequency characteristic of the frequency f ₁ band, and is not required to have a wide band as in the normal subcarrier optical transmission.

In the above description, the baseband signal S
_BB is expressed as I (t) = cos (ω
If it is ₁ t), assumed to be that is 1 channel signal. However, even if the baseband signal S _BB is a multi-channel signal, that is, I (t) = cos (ω
Even if it is expressed as ₁ t) + cos (ω ₂ t) +..., It can be demodulated in the present optical transmitting and receiving apparatus in the same manner as a signal of one channel. Further, when the baseband signal S _BB is particularly digital information, the components of the subcarrier SC of the modulated electrical signal S _mod is digitally amplitude modulated called ASK (Amplitude Shift Keying) and on-off keying (On Off Keying) As a result, the optical transmitting and receiving apparatus can optically transmit high-quality information.

When the sub-carrier SC is modulated by the double-sided band with the baseband signal S _BB (= I (t)) of the digital information, the voltage waveform V of the modulated electric signal S _mod is obtained.
_d (t) is represented by the following equation (13).

[Equation 11] At this time, the electric field intensity waveform E (t) of the double modulated optical signal OS _dmod output from the external optical modulator 120 is obtained as in the following equation (14).

(Equation 12) The double modulated optical signal OS _dmod represented by the above equation (14) passes through the optical filter unit 130, is optically transmitted as the optical signal OS through the optical fiber 140, and then enters the photoelectric conversion unit 150. As described above, the photoelectric conversion unit 150 performs photoelectric conversion on the incident optical signal OS and outputs an electrical signal. The current waveform I _pd (t) of the electric signal is represented by the following equation (15).

(Equation 13)In the above equation (15), km_dI (t) ≪1. This
In the case of double-sideband modulation,
As is clear, the output current waveform of the photoelectric conversion unit 150
Is obtained as a demodulated signal as it is. Ma
From the above equation (15), for a first-order change of I (t),
And I_pdIt can be seen that (t) undergoes a second order change. I
Therefore, M-ASK (multiplex ASK modulation method) is adopted.
Then, compared to the threshold interval of I (t), I_pd(T)
Since the threshold interval is doubled in decibels, the optical signal OS
May occur on the optical transmission line (optical fiber)
It turns out that it becomes strong against noise.

Here, it is assumed that the phase difference between the main carrier MC multiplexed in the external light modulator 120 and the phase-modulated main carrier is π / 2, but the phase difference is other than π / 2. In the case of, basically the same effect can be obtained. Further, the same effect can be obtained even when an electro-absorption type external light modulator or the like is used instead of the Mach-Zehnder type external light modulator. As described above, in the present optical transmission / reception apparatus, the optical signal processing is used to optically transmit a high-frequency electric signal in the millimeter wave band, and the optical signal is further subjected to the optical signal processing. In addition to the need for high-frequency electric components (millimeter-wave band down-converters and demodulators), high-frequency components such as waveguides and semi-rigid cables, which are difficult to handle, are completely unnecessary. As a result, the size of the optical transmitting and receiving device can be extremely reduced.

In addition, since the main carrier is externally modulated with a high-frequency electrical signal in the millimeter wave band, the optical frequency interval between the main carrier component and the sideband component in the optical spectrum shown in FIG. Is widened (corresponding to the millimeter wave band), whereby the optical filter unit 130 can accurately extract only the sideband wave component by the current technology. In the first embodiment, the external optical modulator 120 optically modulates the main carrier MC with the millimeter-wave band electric modulation signal S _mod so as to achieve a remarkable technical effect. However, even if the external light modulator 120 modulates the light with the electric modulation signal S _mod in the other frequency band, the light receiving device 102
Electrical components (down-converter and demodulator) without the need for, can be demodulated baseband signal S _BB. That is,
The optical transceiver according to the first embodiment can be applied to a wider frequency band without being limited to the millimeter wave band.

The optical transceiver according to the first embodiment
Is a modulated electric signal S in the millimeter wave band. _modDirect light modulation with
Is difficult considering the frequency response characteristics of the light source 110.
Therefore, an external light modulation method was adopted. But strange
Electric control signal S_modIf is approximately below the microwave band,
Regardless of the frequency response characteristics, the modulated electric signal S_{mo d}
The light source 110 is directly driven by the
The intensity can also be modulated directly. In other words, this optical transmission and reception
The device can also employ a direct light modulation scheme. Ma
In the optical transmitting and receiving apparatus according to the first embodiment, the optical transmitting device
The optical filter unit 130 of the device 101 has a double modulated signal OS._dmod
Extract only the optical signal OS from the optical fiber 140 and output it to the optical fiber 140
Was. However, the optical filter unit 130 is
02 may be provided. In this case, the optical transmission device 1
01 is a double modulated optical signal generated by the external optical modulator 120
Issue OS_dmodIs directly output to the optical fiber 140. Optical reception
The device 102 is controlled by a front optical filter unit 130.
And the double modulated optical signal O input from the optical fiber 140
S_dmodAfter extracting only the optical signal OS from the
The optical signal OS extracted by the photoelectric conversion unit 150
Opto-electrical conversion is performed for this.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
It is a block diagram which shows the structure of the optical transmission / reception apparatus which concerns on embodiment. The optical transmitting and receiving apparatus shown in FIG.
1 and the optical receiver 102 are connected via an optical fiber 140 so as to enable optical transmission. The optical transmission device 101 includes a light source 110 and first and second external light modulation units 120-1 and 120-1.
20-2, the optical filter unit 130, and the local oscillation unit 170
, And the optical receiving device 102 includes the photoelectric conversion unit 150. 4 (a-3) to (b-3) schematically show signal spectra in main parts (a-3) to (b-3) of the optical transceiver shown in FIG.

Hereinafter, the operation of the optical transceiver shown in FIG.
This will be described with reference to FIGS. Optical transmission device 101
In FIG. 2, the light source 110 is typically composed of a semiconductor laser, oscillates unmodulated light having a constant optical frequency ν as shown in FIG. Output to the light modulation section 120-1. Further, local oscillation section 170 outputs an electrical subcarrier SC having a constant frequency f _{0 in} the millimeter wave band to first external optical modulation section 120-1. The first external light modulator 120-1 has, for example, a Mach-Zehnder type configuration (see the first embodiment), and receives the input main carrier MC (see FIG. 2A-1). The amplitude is modulated by the sub-carrier SC. As a result, a modulated optical signal OS _mod is generated and output to the second external optical modulator 120-2. As shown in FIG. 4A-3, the optical spectrum of the modulated optical signal OS _mod includes the component of the main carrier MC at the central optical frequency ν and the optical frequency f to the optical frequency f.
_There are sideband components (upperband and lowerband) at integer multiples of ₀ (only ± f _{0 in the} figure).

The baseband signal S _BB to be transmitted having the frequency f ₁ is input from outside the optical transmitter 101 to the second external optical modulator 120-2. Second external light modulator 1
20-2 also has, for example, a Mach-Zehnder type configuration (see the first embodiment), and converts the input modulated optical signal OS _mod (see FIG. 4A-3) into the input baseband. Amplitude modulation is performed with the signal _SBB . As a result, a double modulated optical signal OS _dmod is generated. This double modulated optical signal O
As shown in FIG. 4 (b-3), the optical spectrum of S _dmod includes the component of the main carrier MC at the central optical frequency ν, and the position at an integral multiple of the optical frequency f ₀ from the optical frequency ν (± f in the drawing).
₀ only) has components of sidebands (upper and lower sidebands). Also, the occupied frequency band of the two sideband components is dependent on the frequency f _1. In FIG. 4 (b-3), the component of the baseband signal _SBB is different from that shown in FIG. 2 (b-1) in that it also occurs for the main carrier MC. As described above, the double modulated optical signal OS _dmod is input to the optical filter unit 130. In the optical transmitting and receiving apparatus shown in FIG. 3, components subsequent to the optical filter unit 130 perform the same operations as the corresponding components in the optical transmitting and receiving apparatus shown in FIG. Therefore, in the second embodiment, the description of the corresponding components will be omitted. However, since the modulation method of the second embodiment is different from that of the first embodiment, it should be noted that most of the mathematical expressions used in the first embodiment are not applied in the second embodiment. Keep it.

In the optical transmission / reception device shown in FIG.
The external light modulator 120-1 modulates using the subcarrier SC.
The second external light modulator 120-2 outputs the baseband signal S
_BBWas modulated using However, the first external light modulator 1
20-1 is the baseband signal S _BBAmplitude modulation using
The second external optical modulator 120-2 oscillates using the subcarrier SC.
Width modulation may be performed. In addition, the optical transmission and reception according to the second embodiment
In the transmission device, the optical filter unit 130 of the optical transmission device 101
Double modulated signal OS_dmodExtract only the optical signal OS from
The light was emitted to the fiber 140. However, the optical filter section
130 may be provided in the optical receiver 102. This
In the case of, the optical transmitting apparatus 101 includes the second external optical modulator 120
-2 double-modulated optical signal OS_dmodDirect light fa
The light is emitted to the Eva 140. The optical receiving device 102 is
Input from the optical fiber 140 by the
Double modulated optical signal OS_dmodOnly the optical signal OS from
After the extraction, the optical signal is
The photoelectric conversion is performed on the signal OS.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
It is a block diagram which shows the structure of only the optical transmission device about the optical transmission / reception device which concerns on embodiment. Although the optical receiver is not shown in FIG. 5, the optical receiver 102 shown in FIG. 1 or 3 can be connected. Optical transmission device 101 shown in FIG.
Is a local oscillator 170, a mode-locked light source 510,
An external light modulator 120 and an optical filter 130 are provided.

Hereinafter, the optical transmission apparatus 101 shown in FIG.
This will be described with reference to FIG. 2, FIG. 4 and FIG. Local oscillator 17
0 outputs the same subcarrier SC as described above. Modro
The light source 510 is driven by the input sub-carrier SC.
It is locked and oscillates in multiple modes. This mode lock
There are two methods: electric drive or light injection.
These methods may be used. Here, the mode lock
Set the wave number interval equal to the frequency of the subcarrier SC.
In other words, from the mode-locked light source 510, (a-
Modulated optical signal OS shown in 3)_modOptical signal similar to (exact
Oscillates in multiple modes over a wider optical frequency band.
However, for convenience, this optical signal is also modulated optical signal OS _modCall
) Is output to the external light modulator 120. Also,
Baseband signal S similar to_BBIs outside the optical transmitter 101
The signal is input to the external light modulation unit 120 from the unit. External light modulator
120 is an input modulated optical signal OS_modIs entered
Baseband signal S_BBBy amplitude modulation with
4 (b-5), the double modulated optical signal OS shown in FIG._dmodGenerate a
And output. As described above, the double modulated optical signal OS
_dmodIs input to the optical filter unit 130,
As shown in FIG. 1 or FIG.
Since it is the same as the corresponding component in FIG.
Description is omitted.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment of the present invention.
It is a block diagram which shows the structure of the optical transmission / reception apparatus which concerns on embodiment. The optical transmission / reception device shown in FIG. 6 is different from the optical transmission / reception device shown in FIG. 1 in further including an optical branching unit 310, a second photoelectric conversion unit 320, and a wavelength control unit 330. Since there is no other difference between the two optical transmission / reception devices, corresponding components are denoted by the same reference numerals and description thereof will be omitted. Note that the optical signal OS transmitted through the optical-electrical conversion unit 150 and the optical fiber 140 shown in FIG. that called conversion unit 150 and the first optical signal OS _1, keep note here (see FIG. 6).

The operation of the optical transceiver according to the fourth embodiment will be described below with reference to FIG. 6, focusing on the differences from the optical transceiver shown in FIG. In FIG. 6, the optical signal OS
Is the optical filter unit 1 as described in the first embodiment.
The signal is output from the optical splitter 30 and input to the optical branching unit 310. The optical branching unit 310 converts the input optical signal OS into a first optical signal O
S ₁ and the second optical signal OS ₂ are branched into two, and the first optical signal O
S ₁ is emitted to the optical fiber 140, and the second optical signal OS ₂ is output to the second photoelectric conversion unit 320. This first optical signal O
S ₁ after being transmitted through the optical fiber 140, the first photoelectric conversion unit 150 is processed in the same manner as described in the first embodiment. The second photoelectric conversion unit 320 also outputs an electrical signal by performing photoelectric conversion with respect to the second optical signal OS ₂ input. Hereinafter, this electric signal is used as the detection signal S
_{Called det} .

[0055] Wavelength controller 330 at predetermined time intervals, to detect the average value of the detection signal S _{de t} input. Then, the wavelength control unit 330 selects the maximum value V _max among the detected average value as the maximum value V _max is always detected, and controls the temperature or bias current of the light source 110, a main The wavelength (optical frequency) of the carrier MC is controlled. In the optical transmitting and receiving apparatus, the oscillating wavelength of the light source 110 and / or the optical
The pass band of 0 may deviate from a predetermined oscillation wavelength and / or pass band. When such a shift occurs, the optical filter unit 130 generates an upper-band component or a lower-band component from the components (main carrier component and both-side band components) included in the double modulated optical signal OS _dmod. Cannot be accurately extracted. However, according to the optical transmitting and receiving apparatus according to the fourth embodiment, the wavelength control unit 330
Since S is monitored and the oscillation wavelength of the light source 110 is feedback-controlled, even if the above-described deviation occurs, the deviation can be corrected. Can always be accurately extracted.

(Fifth Embodiment) FIG. 7 shows a fifth embodiment of the present invention.
It is a block diagram which shows the structure of the optical transmission / reception apparatus which concerns on embodiment. The optical transmitting / receiving device shown in FIG.
As compared with the optical transmitting and receiving device shown in FIG.
The second optical receiver 102-2 is further provided with a second optical receiver 102-2 that is optically connected to the optical transmitter 101 via the second optical receiver 101-2. Since there is no other difference between the two optical transmission / reception devices, corresponding components are denoted by the same reference numerals, and description thereof will be simplified. In the fifth embodiment, the optical fiber 140, the optical receiving device 102, and the optical-electrical conversion unit 150 illustrated in FIG. -1 and the first photoelectric conversion unit 150-1 are referred to in FIG.
Optical signal OS has been shown also to be referred to as a first optical signal OS _1, previously annotated here. The optical transmission device 101 shown in FIG. 7 is different from the optical transmission device 101 shown in FIG. 1 in that an optical filter unit 710 is provided instead of the optical filter unit 130. Further, the second optical receiving device 102-2 includes a second photoelectric conversion unit 150-2.
8 (a-7) to (f-7) schematically show signal spectra in main parts (a-7) to (f-7) of the optical transceiver shown in FIG.

Hereinafter, an optical transceiver according to the fifth embodiment will be described.
The operation of the optical transmission and reception shown in FIG.
The following description focuses on the differences from the communication device. Optical transmission device 101
In the first embodiment, the baseband modulation unit 180
As described in the above, the input from outside the optical transmitting apparatus 101 is performed.
Baseband signal S _BBIn the local oscillator 170
The subcarrier SC input from the_dWith amplitude modulation
And the modulated electrical signal S_modGenerate Now this baseball
Command signal S_BBIs defined as I (t). This modulation
Air signal S_modVoltage waveform V_d(T) is expressed by the previous equation (2).
The signal is output to the external light modulator 120.

The light source 110 outputs a main carrier MC of the optical spectrum as shown in FIG. 8 (a-7). FIG. 8 (a-7) is the same as FIG. 2 (a-1). The external light modulator 120 is, as described in the first embodiment,
The main carrier MC input from the light source 110 is amplitude-modulated by the modulated electric signal S _mod input from the baseband modulation unit 180, and a double-modulated optical signal having an optical spectrum as shown in FIG. Generate and output OS _dmod . The optical spectrum of FIG. 8 (b-7) is shown in FIG.
Same as 1). Also, this double modulated optical signal O
As described in the first embodiment, the electric field intensity waveform E (t) of S _dmod is finally converted into a mathematical expression as in the previous expression (7). The double modulated optical signal OS _dmod as described above is input to the optical filter unit 710. Optical filter unit 710
_Shows the input double modulated optical signal OS _dmod as shown in FIG.
As shown in 7), the components of the lower side bands included in band B _1, so as to divide on the sideband and the main carrier components contained in the band B _2, is set to the passing light frequency band I have. The optical filter unit 710, the components of the divided lower sideband, a first optical fiber as the first optical signal OS ₁ 140-
Emitted to 1, also the components of the sideband and the main carrier after being divided, as a second optical signal OS ₂ second optical fiber 140
-2.

Here, the detailed configuration and operation of the optical filter section 710 will be described with reference to FIGS. In FIG. 9, the optical filter unit 710 includes an optical circulator unit 910 having terminals 1, 2, and 3, and an optical fiber grating unit 920. Here, terminals 1, 2 and 3
Is connected to the external light modulator 120, the optical fiber grating 920, and the optical fiber 140-1. The double-modulated optical signal OS _dmod input from the external optical modulator 120 to the terminal 1 of the optical circulator 910 is directly output only to the optical fiber grating 920 connected to the terminal 2. The optical fiber grating section 920 is a narrow-band optical notch filter, and of the input double-modulated optical signal OS _dmod , a band B ₁ shown in FIG. 8 (b-7).
Is set so as to reflect only the components included in.
Thus, the first optical signal OS ₁ is reflected, as a result, is again incident on the optical circulator portion 910 from the terminal 2 is directly emitted to only the first optical fiber 140-1 connected to the terminal 3. In the optical fiber grating 920, of the double-modulated optical signal OS _dmod inputted, since the transmission of the components of the reflected band (except bands B _1), the second optical signal OS ₂ and the second optical fiber 140-2
Is emitted. As described above, the optical filter unit 710
By combining an optical circulator, which is an existing optical component, with an optical fiber grating, a narrow band optical filtering process can be realized with a simple configuration.

[0060] optical spectrum of the first optical signal OS ₁ is, as shown in FIG. 8 (c-7), included in the optical frequency band in the vicinity of an optical frequency ν-f _0. This first optical signal OS ₁
The electric field intensity waveform E _OS1 (t) is expressed by the following equation (16). When the following equation (16) is arranged, the following equation (17) is obtained.

[Equation 14]

(Equation 15) Here, m ′ and K in the above equation (16) are the same as those in the previous equation (1).
0) and (11). Further, the second optical signal O
Optical spectrum of S _2, as shown in FIG. 8 (d-1), include the vicinity of the optical frequency [nu to [nu + f ₀ near the optical frequency band. The waveform E _OS2 (t) of the second optical signal OS ₂ is expressed by the following equation (18).

(Equation 16) When the above equation (18) is rearranged using m ′ and K, the following equation (19) is obtained.

[Equation 17]

The first optical signal OS ₁ and the second optical signal OS ₂ as described above with reference to the equations and FIG. 8 are used to convert the first optical fiber 140-1 and the second optical fiber 140-2.
And transmitted to the first optical receiving device 102-1 and the second optical receiving device 102-2. Thus, both the optical signals OS ₁ and OS ₂ are transmitted to the remote location. First,
In the first optical receiver 102-1, a first photoelectric conversion unit 150-1 performs a photoelectric conversion on the first optical signal OS ₁ incident, and outputs an electrical signal. The first optical signal OS ₁ is, referring to FIG. 8 (c-7), the optical frequency ν
The carrier of −f ₀ is the baseband signal S _BB (= cos 2
It can be seen that this is equivalent to the amplitude-modulated signal at πf ₁ t). Therefore, the current waveform I _pd1 (t) of the electric signal output from the first photoelectric conversion unit 150-1 is expressed by the above equation (1).
Similarly to 2), it is expressed by the following equation (20).

(Equation 18)Where η₁Is the conversion efficiency of the first photoelectric converter 150-1
And I_pd1Is a direct current component. Equation (20)
As can be understood by reference, the first photoelectric conversion unit 150
From the electric signal output by −1, a band-pass
Using frequency f ₁By extracting only the components of FIG.
7), the first optical signal OS₁Amplitude modulation
Component is the baseband signal S_BBCurrent waveform I
(T) will be obtained directly. Note that the frequency f₁
Extracting only the components of
Easily implemented by connecting a bandpass filter to the stage
Can appear. Here, the first photoelectric conversion unit 150-1 includes:
This baseband signal S_BBFrequency band to obtain
If there is.

Next, in the second optical receiver 102-2, a second optical-electrical converting portion 150-2, performs photoelectric conversion on the second optical signal OS ₂ incident, outputs an electric signal I do. The second optical signal OS ₂ is 8 Referring to (f-7), a main carrier MC is the aforementioned electric modulation signal S
_mod (a signal obtained by amplitude-modulating the sub-carrier SC with the baseband signal S _BB ) and a single sideband modulation (Single SideBand Modulati)
on)). Therefore, the current waveform I _pd2 (t) of the electric signal output from the second electro-optical converter 150-2 is represented by the following equation (21).

[Equation 19]Where η_TwoIs the conversion efficiency of the second photoelectric conversion unit 150-2.
And I_pd2Is a direct current component. Equation (21)
As can be understood by reference, the second photoelectric converter 150
-2 output a band-pass filter, etc.
Using frequency f ₀By extracting only the components of FIG.
7), the second optical signal OS_TwoAmplitude modulation
The component, that is, the frequency f₀Band electric modulation signal S_modBut,
It will be obtained directly and naturally. Note that the frequency f
₀Extracting only the components of the band is performed by the photoelectric conversion unit 150.
Easy by connecting a band-pass filter to the subsequent stage
Can be realized. Here, the second photoelectric conversion unit 150-2
Is the electric modulation signal S_{mo d}Frequency band that can obtain
All you have to do is.

As described above, the optical transmitter 10 shown in FIG.
1 divides a double-modulated optical signal OS _dmod obtained by double-modulating the main carrier MC into one sideband component and the main carrier and the other sideband component by optical filtering;
Each is optically transmitted. The first and second optical receiver 102-1 and 102-2, by separately photoelectric conversion, respectively, it is possible to obtain a base band signal S _BB with electric modulation signal S _mod. Thus, the optical transmitter-receiver can simultaneously optical transmission baseband signal S _BB with this on a subcarrier SC and an electrical modulation signal S _mod which is amplitude modulated with the same light source 110.

In the fifth embodiment, the optical filter unit 710 divides the band into the lower band component, the upper band component, and the main carrier component. The band may be divided into a sideband component and a main carrier component. The electric modulation signal S _mod shown in FIG. 8 (f-7) is f ₀
Is suitable for wireless transmission in the case of microwave band or millimeter wave band. Therefore, in the subsequent stage of the second photoelectric conversion unit 150-2, the antenna an electric modulation signal S _mod be radiated into space (not shown) is provided, an electric modulation signal S _mod by leading to the antenna, this optical transceiver The device and the wireless transmission system can be easily connected.

In the fifth embodiment, when the electric modulation signal S _mod output from the baseband modulation section 180 is in the microwave band or the millimeter wave band, the light source 110 is controlled by the high frequency electric modulation signal S _mod. It is difficult to perform direct optical modulation in consideration of the frequency response characteristics.
Used an external light modulation method. However, if the electric modulation signal S _mod output from the baseband modulation unit 180 is substantially equal to or lower than the microwave band, the light source 110 is directly driven by the electric modulation signal S _mod irrespective of the frequency response characteristics. The intensity of the output light of 110 can also be directly modulated. That is, the present optical transmitting and receiving apparatus can also employ a direct optical modulation method.

(Sixth Embodiment) FIG. 10 is a block diagram showing a configuration of an optical transceiver according to a sixth embodiment of the present invention. The optical transmission / reception device shown in FIG.
Compared with the optical transmitting and receiving apparatus shown in FIG. 3, the optical transmitting and receiving apparatus is different in that the optical transmitting and receiving apparatus further includes a second optical receiving apparatus 102-2 connected to the optical transmitting apparatus 101 via the second optical fiber 140-2 so as to enable optical transmission. Since there is no other difference between the two optical transmission / reception devices, corresponding components are denoted by the same reference numerals, and description thereof will be simplified. Note that the optical fiber 140, the optical receiving device 102, and the photoelectric conversion unit 150 shown in FIG. 3 and the first photoelectric conversion unit 150-1.
Optical signal OS has been shown also to be referred to as a first optical signal OS _1, previously annotated here. Further, the optical transmission apparatus 101 shown in FIG.
The difference is that an optical filter unit 710 is provided instead of the optical filter unit 130. Further, the second optical receiving device 102-2 includes a second photoelectric conversion unit 150-2. FIGS. 11 (a-10) to (f-10) correspond to FIGS.
0 (f-10) to (f-1).
0) schematically shows the spectrum of the signal.

The operation of the optical transceiver according to the sixth embodiment will be described below with reference to FIGS. 10 and 11, focusing on the differences from the optical transceiver shown in FIG. In the optical transmitter 101, the light source 110 outputs the main carrier MC of the optical spectrum as shown in FIG. 8A to the first external optical modulator 120-1 as described in the second embodiment. I do. Further, local oscillation section 170 outputs the same subcarrier SC as described above to first external optical modulation section 120-1. First
As described in the second embodiment, the external optical modulator 120-1 amplitude-modulates the input main carrier MC with the input subcarrier SC to generate a modulated optical signal OS _mod . Output to the external light modulator 120-2. The optical spectrum of the modulated optical signal OS _{mod is the same as} the optical spectrum of FIG. 4A-3A, as shown in FIG.

As described in the second embodiment,
Baseband signal S_BBFrom outside the optical transmitter 101
2 Input to the external light modulator 120-2. Second external light change
The adjusting section 120-2 is also provided as described in the second embodiment.
, The input modulated optical signal OS_modTo the entered base
Sband signal S_BBModulated optical signal OS with amplitude modulation
_dmodGenerate This double modulated optical signal OS_dmodLight spec
As shown in FIG. 11 (b-10),
Since it is the same as the optical spectrum of (b-3), a detailed description will be given.
Omitted. As described above, the double modulated optical signal OS
_dmodAre input to the optical filter unit 710. Optical filter section
710 is the input double modulated optical signal OS_dmodFigure 1
1 (b-10), the band B₁Included in the lower side
Band wave component and band B_TwoUpper band wave and main carrier included in
So that the transmitted light frequency band is divided into
Is set. The optical filter unit 710 is
The component of the sideband is converted to the first optical signal OS.₁As the first optical fiber
Outgoing to the bar 140-1, and the split upper band wave and
The component of the main carrier is converted to the second optical signal OS_TwoAs the second optical fiber
The light is emitted to the eva 140-2. This first optical signal OS₁Light of
The spectrum is as shown in FIG. 11 (c-10).
Frequency ν-f₀Is included in the optical frequency band in the vicinity of. Ma
The second optical signal OS_TwoThe optical spectrum of FIG.
As shown in (d-10), from the vicinity of the optical frequency ν, ν + f
₀Included in nearby optical frequency bands. As explained above
The first optical signal OS₁And the second optical signal OS_TwoIs the fifth
As described in the embodiment, the first optical receiver 102-1
And the second light receiving device 102-2. This
The two optical signals OS₁And OS_TwoIs transmitted to a remote location
You.

The first optical receiving device 102-1 and the second optical receiving device 102-2 operate in the same manner as in the fifth embodiment, so that a base having a spectrum as shown in FIG. The band signal S _BB and FIG.
An electric modulation signal having a spectrum as shown in -10) (a signal obtained by amplitude-modulating a subcarrier with a baseband signal)
And outputs S _mod . Incidentally, in FIG. 11 (f-10), the electrical modulation signal S _{mo d} is shown an electrical modulation signal S _mod in FIG 8 (f-7) in substantially the same. However, to be precise, due to the influence of the sideband component (see the hatched portion) of the main carrier MC, the electric modulation signal S _mod shown in FIG.
_Has slightly larger distortion than the electric modulation signal S _mod shown in FIG. 8 (f-7). However, since the modulation method of the sixth embodiment is different from that of the fifth embodiment, most of the mathematical formulas used in the fifth embodiment are different from those of the sixth embodiment.
Note that this does not apply to the embodiment. As described above, according to the optical transmitter shown in FIG. 10, the main carrier MC is double-modulated (the modulated optical signal OS _mod obtained by amplitude-modulating the main carrier with the sub-carrier is further converted into the baseband signal _SBB) . Double modulated optical signal OS _dmod obtained by amplitude modulation)
(See FIG. 11 (b-10)), the optical spectrum is divided into one sideband component, the main carrier and the other sideband component by optical filtering, and each is optically transmitted. Then, the first optical receiving device and the second optical receiving device individually perform opto-electrical conversion, thereby obtaining the baseband signal S _BB (see FIG. 11E-10) and the electric modulation signal S _mod (see FIG. _11E ). 11 (f-10)). In this way, the present optical transmitting and receiving apparatus also has the same light source 11.
Using 0, a baseband signal and a signal obtained by amplitude-modulating a subcarrier with the baseband signal are simultaneously optically transmitted.

In the optical transmitting / receiving apparatus shown in FIG.
Also, the optical filter unit 710 includes an upper band component and a lower band component.
The band may be divided into a wave component and a main carrier component. Also,
The optical transmitting and receiving device shown in FIG.
Similarly to the device, the second photoelectric conversion unit 150-2 is provided at a subsequent stage.
The antenna (described above) is provided, and the electric modulation signal S _modThe said en
Easy connection to wireless transmission system by guiding to tena
it can. Further, in the optical transceiver shown in FIG.
The external optical modulator 120-1 modulates the signal using the subcarrier, and
2 The external light modulator 120-2 uses the baseband signal
Was modulated. However, the first external light modulator 120-1 is
Amplitude modulation using a baseband signal and second external light modulation
Unit 120-2 may perform amplitude modulation using the subcarrier.

(Seventh Embodiment) FIG. 12 is a block diagram showing a configuration of an optical transceiver according to a seventh embodiment of the present invention. The optical transmitting and receiving apparatus shown in FIG. 12 is different from the optical transmitting and receiving apparatus shown in FIG.
The first optical receiving device 102-1 is a low-pass filter unit 122
0 is further provided, and the second optical receiver 102-2 is further provided with a high-pass filter unit 1230. The other configuration is the same as that of the optical transmitting / receiving apparatus shown in FIG.

The operation of the optical transceiver shown in FIG.
Will be described with reference to FIG. 11 and FIG. Second outside
The optical modulator 120-2 has the same double modulation as in the sixth embodiment.
Light control signal OS _dmod(See FIG. 11 (b-10))
Output to the optical branching unit 1210. The optical branching unit 1210
Double modulated optical signal OS_dmodIs multi-branched (in this description
Splits into two) and splits into optical fibers 140-1 and 140-2.
Emit. Double-branched double modulated optical signal OS_dmodOne of
And the other, after this, the optical fibers 140-1 and 140-1
-2, the first photoelectric conversion unit 150-1 and the second
The light enters the photoelectric conversion unit 150-2. First photoelectric conversion
The unit 150-1 and the second photoelectric conversion unit 150-2 are
Modulated optical signal OS_dmodIs photoelectrically converted and output. In addition,
First photoelectric converter 150-1 and second photoelectric converter 15
The light receiving current of 0-2 includes the baseband signal S_BB(Figure 1
1 (e-10)) and the electric modulation signal S
_mod(See FIG. 11 (f-10)).
You.

The electric signal output from first electric conversion section 150-1 is input to low-pass filter section 1220, and only the portion of the electric signal included in the low band passes through filter section 1220 and is output. You. This allows the second
As in the embodiment, the baseband signal S _BB (FIG. 11)
(See (e-10)). On the other hand, the electric signal output from the second electro-optical conversion unit 150-2 is input to the high-pass filter unit 1230, and only a part of the electric signal included in the high band passes through the filter unit 1230 and is output. You. Thereby, similarly to the second embodiment, an electric modulation signal S _mod (see FIG. 11F-10) can be obtained.

As described above, according to the optical transmitter shown in FIG. 12, the same main carrier M as the optical transmitter shown in FIG.
The double-modulated optical signal OS _dmod obtained by double-modulating C is multi-branched,
Each is optically transmitted. Then, the first optical receiving device and the second optical receiving device individually obtain the baseband signal _SBB and the electric modulation signal S _mod by individually performing opto-electric conversion and then performing low-pass and high-pass filtering. be able to. Thus, the present optical transmitting and receiving apparatus also uses the same light source 1.
The optical transmission of the baseband signal and the electric modulation signal can be simultaneously performed by using the optical signal 10. The first and second optical receivers 102-1 and 102-2 described above have first and second opto-electric converters 150 having different frequency bands in which opto-electric conversion is possible.
-1 and 150-2. However, the first and second optical receiving apparatuses 102-1 and 102-2 are identical to each other and have a wide frequency band capable of collectively performing the photoelectric conversion of the double modulated optical signal OS _dmod. A conversion unit may be provided. Even such a case, the first and second optical receiver 102-1 and 102-2, by the low-pass and high-pass filtering, it is possible to obtain a base band signal S _BB and electric modulation signal S _mod. Note that, as the optical transmission device 101 according to the present embodiment, a device other than that described in the sixth embodiment may be applied.

(Eighth Embodiment) In the optical transmitting and receiving apparatus shown in FIG. 12, two types of optical receiving apparatuses having different configurations are connected. However, if the optical receiving device is configured as described below, even if only one type of optical receiving device is connected to the optical transmitting and receiving device, both the baseband signal _SBB and the electric modulation signal _Smod can be obtained. Hereinafter, such an optical receiving apparatus will be described with reference to FIG.

In the optical transmitting / receiving apparatus shown in FIG. 13, an optical transmitting apparatus 101 and one or more optical receiving apparatuses 102 are connected via an optical fiber 140 so as to enable optical transmission. The optical transmission device 101 shown in FIG.
Since the configuration is the same as that of the first embodiment, the description thereof is omitted. FIG.
The optical receiver 102 shown in FIG. 3 has a configuration different from the optical receiver 102-1 or 102-2 shown in FIG. 12, and includes an opto-electric converter 150, a distributor 1310,
Low-pass filter section 1320 and high-pass filter section 1
330.

As is clear from the above, the optical transmission device 1
The double-modulated optical signal OS _dmod emitted from 01 is transmitted through each optical fiber 140 and enters the photoelectric conversion unit 150 of the optical receiving device 102. The photoelectric conversion unit 150 has a broadband characteristic capable of performing photoelectric conversion from a low band to a high band, and collectively performs photoelectric conversion of the double modulated optical signal OS _dmod .
An electric signal obtained by this is output to distributor 1310. The electric signal is multi-divided by the distributor 1310 (in the present description, the electric signal is divided into two). One of the electric signals divided into two by the divider 1310 is input to the low-pass filter unit 1320, and only a part of the electric signal included in the low band passes through the filter unit 1320 and is output. Thereby, the baseband signal S _BB (FIG. 11 (e)
-10)) is obtained.

The other of the electric signals divided into two by divider 1310 is input to high-pass filter section 1330, and only the portion of the electric signal included in the high band passes through filter section 1330 and is output. You. As a result, an electric modulation signal S _mod (see FIG. 11 (f-10)) is obtained.

As described above, if the optical transmitting / receiving apparatus has one optical receiving apparatus shown in FIG. 13, similarly to the optical transmitting / receiving apparatus shown in FIG. 12, the baseband signal _SBB and the electric modulation signal S _mod You can get both. In FIG. 13, a plurality of (two in the figure) optical receiving devices 102 are connected. However, the number of the optical receivers 102 may be one depending on the construction conditions of the optical transceiver. In such a case, the optical splitter 1210 becomes unnecessary, and the second external optical modulator 120-2 transmits the double modulated optical signal O to the optical fiber 140.
_Emit S _dmod . Further, in the optical transmitting and receiving apparatuses according to the seventh and eighth embodiments, the first external optical modulator 120-
As is clear from FIG. 11, the first and second external light modulators 120-2 are amplitude-modulated by the double-sided band amplitude modulation method. However, the first external light modulator 120-
The first and second external light modulators 120-2 may perform amplitude modulation by a single sideband amplitude modulation method. According to the single sideband amplitude modulation method, the double modulated optical signal OS _dmod
The center optical frequency ν has a main carrier MC component. The double-modulated optical signal OS _dmod is further on the high frequency side or the low frequency side with respect to the optical frequency ν, and at the position of the optical frequency f ₀ from the optical frequency ν, the upper band or the lower band. With components. Such an optical signal OS _dmod is transmitted through each optical fiber, but is less affected by chromatic dispersion in the optical fiber 140 than in the case of double-sideband amplitude modulation. Can be done.

(Ninth Embodiment) FIG. 14 is a block diagram showing a configuration of an optical transmitting / receiving apparatus according to a ninth embodiment of the present invention, which includes only an optical transmitting apparatus. Although the optical receiver is not shown in FIG. 14, the optical receivers 102-1 and 102-2 shown in FIG. 12 or the optical receiver 102 shown in FIG. 13 can be connected. Optical transmission device 10 shown in FIG.
1 is different from the optical transmitting apparatus 101 shown in FIG. 5 in that an optical branching unit 1210 is provided instead of the optical filter unit 130. Since there is no other difference, the corresponding components are denoted by the same reference numerals. Further, the optical branching unit 1210 has also been described with reference to FIG. Therefore, since the operation of the optical transmission apparatus 101 shown in FIG. 14 is clearer than these, the description is simplified.

The mode-locked light source 510 is
The mode is locked by the sub-carrier SC inputted from 70 and multi-mode oscillation is performed. If the frequency interval of the mode lock is set to be equal to the frequency of the subcarrier SC, the modulated optical signal OS _mod (see FIG. 11A-10) is output from the mode lock light source 510 to the external light modulator 120. External light modulator 120 generates based on the baseband signal S _BB inputted from the input modulated optical signal OS _mod and external double-modulated optical signal OS _dmod (see FIG. 11 (b-10)), Output to the optical branching unit 1210. Optical branching unit 1210
After multi-branching the input double-modulated optical signal OS _dmod , the optical signal is output to each optical fiber 140. In the optical transmitting / receiving apparatus shown in FIG. 14, at least one optical receiving apparatus 102 only needs to be connected, and if one optical receiving apparatus 102 is used, the optical branching unit 1210 becomes unnecessary, and The double modulated optical signal OS _dmod is emitted to 140.

(Tenth Embodiment) FIG. 15 is a block diagram showing the configuration of an optical transmitting and receiving apparatus according to a tenth embodiment of the present invention, which includes only an optical transmitting apparatus. Note that FIG.
Although the optical receiver is not shown in FIG. 1, the optical receivers 102-1 and 102-2 shown in FIG. 12 or the optical receiver 102 shown in FIG. 13 can be connected. The optical transmitter 101 shown in FIG. 15 includes a first light source 1510-1 and a second light source 1510
-2, an external light modulator 120, an optical multiplexer 1520,
And an optical branching unit 1210. In the optical transmitting apparatus 101 of FIG. 15, those corresponding to the components of the optical transmitting apparatus of FIG. 14 are denoted by the same reference numerals, and the description thereof will be simplified. Fig. 16 (a-15)-
(D-15) is a main part (a-1) of the optical transmission device shown in FIG.
5A to 5D schematically show signal spectra.

Hereinafter, the operation of the optical transceiver according to the tenth embodiment will be described with reference to FIGS. In the optical transmitting apparatus 101, the first light source 1510-1, the first unmodulated light UML ₁ external optical modulating portion of the optical frequency [nu 120
Output to The first unmodulated light UML ₁ is FIG. 16 (a
It has an optical spectrum as shown in -15). Also,
The baseband signal S _BB of the frequency f ₁ is
Is input to the external light modulation unit 120 from outside. External light modulator 120, as described in the second embodiment, the first unmodulated light UML ₁ input, and an amplitude modulated by the input baseband signal S _BB generating a modulated optical signal OS _mod I do. The optical spectrum of the modulated optical signal OS _mod is shown in FIG.
6 as shown in (b-15), the first unmodulated light component of UML ₁ to the center optical frequency [nu, more integer multiples of the position the optical frequency f ₁ from the optical frequency [nu (shown ± f ₁ only) It has a sideband component. Such a modulated optical signal OS _mod is input to the optical multiplexing unit 1520.

The second light source 1510-2 receives the light frequency ν
And outputs to the optical multiplexing section 1520 and the second unmodulated light UML ₂ apart by a predetermined optical frequency from. This predetermined optical frequency is an optical frequency corresponding to the frequency f ₀ of the sub-carrier SC. The second unmodulated light UML _2, as shown in FIG. 16 (c-15)
Has an optical spectrum as shown in FIG. Optical multiplexing section 152
0 is the input modulated optical signal OS _mod and the second unmodulated light U
ML ₂ is multiplexed with the ML ₂ so that their polarizations are combined, and output to the optical branching unit 1210 as an optical signal OS. This optical signal OS is composed of the modulated optical signal OS _mod and the second unmodulated light UML ₂
Are simply multiplexed, and have an optical spectrum as shown in FIG. 16 (d-15). Referring to FIG. 16D-15, the optical spectrum of the optical signal OS is the eighth.
It is understood that this is the same as the case where the single sideband amplitude modulation method described in the embodiment is applied. Therefore, the optical transmitting apparatus 101 configured as shown in FIG. 15 also has the same effect as the case where the single sideband amplitude modulation method described in the eighth embodiment is applied.
Further, in the present embodiment, the baseband is used using only two light sources (the first light source 1510-1 and the second light source 1510-2) without using the local oscillation unit 170 as in the eighth embodiment. The signal _SBB and the electric modulation signal _Smod can be optically transmitted. Thus, in the eighth embodiment and the like, the first external light modulation unit 120-1 and the second external light modulation unit 120-2 need to perform the electro-optical conversion twice. The device 101 includes an external light modulator 12
At 0, electro-optical conversion is performed only once. Thus, by reducing the number of times of the electro-optical conversion, low-loss optical transmission can be realized. Furthermore, the optical transmission device 10 of the present embodiment
1 does not require an electrical component for amplitude modulating the subcarrier with an electrical signal to be transmitted. That is, according to the present embodiment, there is no need for expensive and difficult-to-process electric components corresponding to the subcarrier band having a relatively high frequency. Along with this,
The optical transmitting and receiving device can be configured easily and at low cost. Further, the oscillation light frequencies of the two light sources can be easily changed by changing the respective bias currents and the ambient temperature. Therefore, the frequency band of the electric modulation signal S _mod obtained on the optical receiving device side can be easily changed. In the tenth embodiment, as can be understood with reference to FIG.
The oscillation light frequency of 0-1 is ν, and the second light source 1510−
It has been described that the oscillation light frequency of No. 2 is ν + f ₀ . However, the oscillation light frequency of the second light source 1510-2 is ν−f ₀
It may be.

In each of the above embodiments, when the baseband signal is analog information, the analog information is transmitted on the subcarrier SC by optical transmission.
Since the optical signals 50-1 and 150-2 typically detect the square of the optical signal, the second harmonic may interfere. Therefore, on the optical transmission apparatus 101 side, a baseband signal of analog information is converted from analog to digital, and a baseband signal, which is digital information obtained by this, is carried on a subcarrier and optically transmitted. The optical receiver 102 and the like perform digital / analog conversion of such an optical signal after photoelectric conversion. As a result, the optical transceiver can transmit high-quality information that is not subject to harmonic interference.

The optical transmitting and receiving apparatus according to each of the embodiments has a configuration in which a baseband signal is input from the outside. However, the baseband signal is preliminarily mounted on a carrier having an intermediate frequency using a predetermined modulation method (amplitude modulation, frequency modulation, or phase modulation). If the signal obtained by modulating the intermediate frequency carrier is optically transmitted after being superimposed on the subcarrier SC output from the local oscillation unit 170, the optical receiving device according to each embodiment allows the intermediate frequency carrier and the Thus, a signal obtained by modulating the subcarrier SC can be obtained, and optical transmission independent of the modulation method can be performed. Note that the intermediate frequency is limited to a frequency lower than the frequency f ₀ of the sub-carrier SC. This means that if the carrier component of the intermediate frequency is not included between ν ± f ₀ , This is because it is difficult to perform electrical conversion and filtering. Further, in the optical transmitting and receiving apparatus according to each embodiment, a plurality of intermediate frequency carrier waves having different frequencies are prepared, different baseband signals are respectively loaded on different intermediate frequency carriers, and a frequency division multiplexing method is adopted. Thus, these can be collectively optically transmitted.

The optical transmitting and receiving apparatus according to each embodiment includes
By employing time division multiplexing or code division multiplexing, it is also possible to multiplex different baseband signals onto one intermediate frequency carrier and transmit the multiplexed baseband signals. Further, by using frequency division multiplexing and time division multiplexing or code division multiplexing in combination, more information can be multiplexed and transmitted. As described above, by optically filtering the double amplitude-modulated optical signal, the optical spectrum is divided into one sideband component and the main carrier and the other sideband component, and each is optically transmitted. After these are subjected to photoelectric conversion, a baseband signal to be transmitted and an electric modulation signal obtained by modulating a subcarrier with the baseband signal can be simultaneously obtained. This electric modulation signal is suitable for wireless transmission in a microwave band or a millimeter wave band. Therefore, according to the present optical transmission / reception device, it is possible to construct a system in which a wired communication network using an optical fiber and a wireless transmission system using an electric modulation signal (a high-frequency signal in a microwave band or a millimeter band) are integrated. Moreover, the optical transmitter uses only one light source, which is advantageous in terms of the construction and maintenance costs of the optical transmitter and receiver.

Further, the transmission loss of the 1.3 μm band single mode fiber which is generally used is the smallest.
In the case of transmitting an optical signal in the 5 μm band, the extinction of the modulation component due to dispersion occurs in a few km in an ordinary amplitude modulated optical signal with a high-frequency signal such as a millimeter wave band. Since an amplitude-modulated optical signal having only the sideband component is received, it is not affected by dispersion. In addition, by using an optical signal in the 1.5 μm band, an optical amplifier (EDFA: Erbium Doped Fiber Amplifier) is used.
Can be used, so that the light receiving sensitivity can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical transceiver according to a first embodiment of the present invention.

FIG. 2 is a main part (a-1) to of the optical transceiver shown in FIG. 1;
FIG. 4 schematically shows a spectrum of a signal in (d-1).

FIG. 3 is a block diagram illustrating a configuration of an optical transceiver according to a second embodiment of the present invention.

FIG. 4 is a main part (a-3) of the optical transceiver shown in FIG. 3;
FIG. 3B schematically shows the spectrum of the signal in FIG.

FIG. 5 is a block diagram showing a configuration of only an optical transmission device in an optical transmission and reception device according to a third embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of an optical transceiver according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram illustrating a configuration of an optical transceiver according to a fifth embodiment of the present invention.

8 is a main part (a-7) of the optical transceiver shown in FIG. 7;
5 schematically shows the spectrum of the signal at (f-7).

FIG. 9 is a block diagram illustrating a detailed configuration of an optical filter unit 710.

FIG. 10 is a block diagram illustrating a configuration of an optical transceiver according to a sixth embodiment of the present invention.

11 is a main part (a-1) of the optical transmitting and receiving apparatus shown in FIG.
2 schematically shows the spectrum of a signal in (0) to (f-10).

FIG. 12 is a block diagram illustrating a configuration of an optical transceiver according to a seventh embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of an optical transceiver according to an eighth embodiment of the present invention.

FIG. 14 is a block diagram showing a configuration of an optical transmitting and receiving apparatus according to a ninth embodiment of the present invention, which includes only an optical transmitting apparatus.

FIG. 15 is a block diagram illustrating a configuration of only an optical transmission device in an optical transmission and reception device according to a tenth embodiment of the present invention.

16 is a main part (a-15) of the optical transmitter illustrated in FIG.
5 schematically shows the spectrum of a signal in (d-15).

FIG. 17 is a block diagram showing a configuration of a first optical transmission / reception apparatus conventionally used.

FIG. 18 is a block diagram showing a configuration of a second optical transmission / reception device conventionally used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Optical transmission device 110 ... Light source 120 ... External light modulation part 130,710 ... Optical filter part 120-1 ... First external light modulation part 120-2 ... Second external light modulation part 510 ... Mode lock light source 170 ... Local oscillation Unit 180 Baseband modulation unit 190 Antenna unit 102 Optical receiving device 150 Photoelectric conversion unit 150-1 First photoelectric conversion unit 150-2 Second photoelectric conversion unit 140 Optical fiber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/04 10/06

Claims (25)

[Claims] An optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein a subcarrier modulated with an electric signal to be transmitted is inputted from outside and has a constant optical frequency. A double modulation unit that generates and outputs a double modulated optical signal by doubly modulating a main carrier that is unmodulated light with the input subcarrier, and is input from the double modulation unit. The optical spectrum of the double-modulated optical signal includes the main carrier component at the position of the constant optical frequency, and the upper band and the lower band at a position separated from the constant optical frequency by the frequency of the subcarrier. Component, and from the double modulated optical signal input from the double modulation unit, an optical filter unit that passes an optical signal containing any one of the upper band and the lower band. Input from the optical filter unit A photoelectric conversion unit that obtains the electrical signal to be transmitted by photoelectrically converting the optical signal to be transmitted, wherein the optical transmission device includes at least the double modulation unit, and the optical reception device Includes at least the photoelectric conversion unit, and the optical filter unit is included in one of the optical transmission device and the optical reception device. 2. The dual modulation section, comprising: a semiconductor laser that outputs the main carrier; and an external signal that transmits the main carrier input from the semiconductor laser according to an external optical modulation method. The optical transmitting and receiving apparatus according to claim 1, further comprising at least one external optical modulation unit that performs amplitude modulation with the subcarrier that is amplitude-modulated in (1). 3. The sub-carrier amplitude-modulated with the electric signal to be transmitted is a signal transmitted wirelessly from the outside, and receives the signal transmitted wirelessly and sends the signal to the dual modulation unit. The optical transmitting and receiving device according to claim 2, further comprising an antenna unit for supplying. 4. The electric signal to be transmitted is a frequency-multiplexed multi-channel signal, and the sub-carrier amplitude-modulated by the multi-channel signal is:
4. The optical transmitting and receiving apparatus according to claim 3, wherein the signal is externally input to the double modulation unit. 5. The electric signal to be transmitted is digital information, and the sub-carrier on / off keyed by the digital information is inputted from the outside to the double modulation unit. 4. The optical transceiver according to 3. 6. An optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, wherein a subcarrier modulated with an electric signal to be transmitted is inputted from outside and has a constant optical frequency. A main carrier that is unmodulated light, by double-modulating the input sub-carrier, a double modulator that generates and outputs a double-modulated optical signal, and is input from the double modulator. The optical spectrum of the double-modulated optical signal includes the main carrier component at the position of the constant optical frequency and the upper band and the lower band at a position separated from the constant optical frequency by the frequency of the subcarrier. And an optical filter unit that passes an optical signal containing any one of the upper band and the lower band from the double modulated optical signal input from the double modulator. Input from the optical filter section An optical splitter for splitting the optical signal to be split into a first optical signal and a second optical signal, and outputting the first optical signal, and the first optical signal input from the optical splitter is photoelectrically converted to perform the transmission. First to get an electrical signal
A photoelectric conversion unit, a second photoelectric conversion unit that outputs an electric signal obtained by photoelectrically converting the second optical signal input from the optical branching unit as a detection signal, at predetermined time intervals, An average value of the detection signal input from the second photoelectric conversion unit is detected, and a wavelength of the double modulation optical signal output from the double modulation unit is determined based on the maximum value of the detected average value. A wavelength control unit for controlling, the optical transmission device includes at least the double modulation unit, the optical reception device includes at least the first photoelectric conversion unit, and the optical filter unit includes An optical transmitting / receiving device, which is included in one of the optical transmitting device and the optical receiving device. 7. An optical transmission / reception device in which an optical transmission device and first and second optical reception devices are connected so as to be capable of optical transmission, wherein the optical transmission device outputs a subcarrier having a constant frequency. By modulating a main carrier, which is unmodulated light having a constant optical frequency, with an electric signal to be transmitted externally input and the sub-carrier input from the local oscillator, A double modulation unit that generates and outputs a double modulation optical signal, the spectrum of the double modulation optical signal output from the double modulation unit, the component of the main carrier at the position of the constant optical frequency, The optical transmitter further includes an upper wave component and a lower band component at a position separated from the constant optical frequency by the frequency of the subcarrier, and the optical transmitter includes the double modulated optical signal input from the double modulator. The upper band wave and the lower band And a first optical signal including a component of the main carrier and a second optical signal including the other component of the upper band and the lower band. Signal and second
An optical filter unit that outputs an optical signal, wherein the first optical receiving device converts the electrical signal to be transmitted by performing optical-electrical conversion on the first optical signal transmitted from the optical transmitting device. Obtaining, further, the second optical receiving device transmits the second optical transmission device transmitted from the optical transmitting device.
An optical transmitting and receiving apparatus, wherein an optical signal is photoelectrically converted to obtain a signal in which the subcarrier is modulated with the electric signal to be transmitted. 8. The optical circulator section, which outputs the double modulated optical signal input from the double modulator section as it is, and an optical circulator section that outputs the double modulated optical signal input from the optical circulator section. Among them, the first optical signal is generated by reflecting one of the components of the upper sideband and the lower sideband and output to the optical circulator unit, and the component of the main carrier and the upper sideband and An optical fiber grating section that generates the second optical signal by transmitting any other component of the lower sideband and outputs the generated second optical signal to the second optical receiving device, wherein the optical circulator section further includes the optical fiber grating. The optical transmitting and receiving device according to claim 7, wherein the first optical signal input from the unit is directly output to the first optical receiving device. 9. The apparatus according to claim 7, wherein the second optical receiving apparatus includes an antenna unit for radiating a signal obtained by modulating a subcarrier with the electric signal to be transmitted obtained by photoelectric conversion into a space. The optical transmitting / receiving device as described in the above. 10. The optical transceiver according to claim 7, wherein the electric signal to be transmitted is a signal in which analog information is converted into digital information. 11. The electric signal to be transmitted, wherein a plurality of electric signals obtained by modulating a carrier of the intermediate frequency with analog information or digital information are multiplexed by a predetermined multiplexing method. 8. The optical transceiver according to 7. 12. The optical transceiver according to claim 11, wherein the predetermined multiplexing method is frequency division multiplex access, time division multiplex access, or code division multiplex access. 13. An optical transmission / reception device in which an optical transmission device and first and second optical reception devices are connected so as to be capable of optical transmission, wherein the optical transmission device outputs a subcarrier having a constant frequency. By modulating a main carrier, which is unmodulated light having a constant optical frequency, with an electric signal to be transmitted externally input and the sub-carrier input from the local oscillator, The first optical receiving device includes: a double modulation unit that generates and outputs a double modulation optical signal; and an optical branch unit that branches and outputs the double modulation optical signal input from the double modulation unit. A low-pass that outputs the electric signal to be transmitted by passing a component included in a low band of the electric signal obtained by performing the photoelectric conversion of the double-modulated optical signal transmitted from the optical transmission device. A second pass filter unit; The device passes a component included in a high band of an electric signal obtained by photoelectrically converting the double-modulated optical signal transmitted from the optical transmission device, and transforms the subcarrier with the electric signal to be transmitted. An optical transmission / reception device including a high-pass filter unit that outputs a modulated signal. 14. An optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected so as to be capable of optical transmission, the optical transmitting apparatus comprising: a local oscillator for outputting a subcarrier having a constant frequency; By modulating the main carrier which is unmodulated light having an externally input electric signal to be transmitted and the sub-carrier input from the local oscillator, a double modulated optical signal is obtained. A double modulation unit that generates and outputs the optical receiving device, wherein the optical receiving device photoelectrically converts the double modulated optical signal transmitted from the optical transmitting device and outputs an electric signal; A distribution unit that distributes at least two electric signals input from the opto-electrical conversion unit; and outputs the electric signal to be transmitted by passing a component included in a low band of the electric signal distributed by the distribution unit. Low pass A high-pass filter unit that outputs a signal obtained by modulating the subcarrier with the electric signal to be transmitted by passing a component included in a high band of the electric signal distributed by the distribution unit. An optical transceiver. 15. The dual modulation section generates and outputs a modulated electric signal by amplitude-modulating the subcarrier input from the local oscillation section with the electric signal to be transmitted input from the outside. An electrical modulation unit, a light source that outputs the main carrier that is unmodulated light having a constant optical frequency, and an amplitude of the main carrier that is input from the light source with the modulated electrical signal that is input from the electrical modulation unit. The optical transceiver according to claim 7, further comprising an external optical modulator that generates the double modulated optical signal by performing modulation. 16. The optical transmitting and receiving apparatus according to claim 15, wherein the electric signal to be transmitted is digital information, and wherein the electric modulation unit performs on / off keying of the subcarrier with the digital information. 17. The dual modulation section, comprising: a light source that outputs the main carrier, which is unmodulated light having a constant optical frequency; and the subcarrier that is input from the local oscillation section, which is input from the light source. A first external optical modulation unit that generates and outputs a modulated optical signal by amplitude-modulating the main carrier; and an electric signal to be transmitted input from the outside and input from the first external light modulation unit. A second method for generating the double modulated optical signal by amplitude-modulating the modulated optical signal
The optical transceiver according to claim 7, 13 or 14, further comprising an external light modulator. 18. The dual modulation section, comprising: a light source that outputs the main carrier wave, which is unmodulated light having a constant optical frequency; and an electric signal to be transmitted that is input from outside and is input from the light source. A first external optical modulator that generates and outputs a modulated optical signal by amplitude-modulating the main carrier; and a subcarrier that is input from the local oscillator and is input from the first external optical modulator. A second method for generating the double modulated optical signal by amplitude-modulating the modulated optical signal
The optical transceiver according to claim 7, 13 or 14, further comprising an external light modulator. 19. The apparatus according to claim 13, wherein the dual modulation section modulates the main carrier with the sub-carrier input from the local oscillation section by a single sideband amplitude modulation method. An optical transmitting / receiving device according to claim 1. 20. An optical transmission / reception device in which an optical transmission device and first and second optical reception devices are connected so as to be capable of optical transmission, wherein the optical transmission device outputs a subcarrier having a constant frequency. A mode-locked light source that generates and outputs a mode-locked optical signal by being mode-locked based on a sub-carrier input from the local oscillator and oscillating at an optical frequency interval related to the sub-carrier, An external light modulator that generates and outputs a double-modulated optical signal by amplitude-modulating the mode-locked optical signal input from the mode-locked light source with an input electrical signal to be transmitted; and An optical branching unit that splits and outputs the double-modulated optical signal input from the unit, wherein the first optical receiving device photoelectrically converts the double-modulated optical signal transmitted from the optical transmitting device. A low-pass filter unit that outputs the electric signal to be transmitted by passing a component included in a low band of the electric signal obtained by the gas conversion, and wherein the second optical receiving device includes the optical transmitting device. A signal obtained by modulating the sub-carrier with the electric signal to be transmitted by passing a component contained in a high band of the electric signal obtained by performing photoelectric conversion on the double-modulated optical signal transmitted from An optical transmitting and receiving device comprising a high-pass filter section. 21. An optical transmission / reception device in which an optical transmission device and an optical reception device are connected so as to enable optical transmission, the optical transmission device comprising: a local oscillation unit that outputs a subcarrier having a constant frequency; A mode-locked light source for generating and outputting a mode-locked optical signal by oscillating at an optical frequency interval related to the sub-carrier, An external light modulator that generates and outputs a double-modulated optical signal by amplitude-modulating the mode-locked optical signal input from the mode-locked light source with an electric signal to be provided; A photoelectric conversion unit that photoelectrically converts the double-modulated optical signal transmitted from the transmission device and outputs an electric signal; and at least an electric signal input from the photoelectric conversion unit. A distributing unit for distributing, a low-pass filter unit for outputting the electric signal to be transmitted by passing a component included in a low band of the electric signal distributed by the distributing unit; A high-pass filter unit that outputs a signal obtained by modulating the subcarrier with the electric signal to be transmitted by passing a component included in a high band of the electric signal. 22. An optical transmitting and receiving apparatus in which an optical transmitting apparatus and an optical receiving apparatus are connected to be capable of optical transmission, wherein the optical transmitting apparatus outputs a first unmodulated light having a first optical frequency. A light source; an external light modulation unit that generates and outputs a modulated light signal by amplitude-modulating the first unmodulated light input from the first light source with an electric signal to be transmitted input from the outside; A second light source that outputs a second unmodulated light having a second optical frequency that is different from the first optical frequency by a predetermined optical frequency, a modulated optical signal that is input from the external light modulator, and a second optical source that is input from the second light source An optical multiplexing unit that generates and outputs an optical signal by multiplexing the second unmodulated light with the polarization of the modulated optical signal and the second unmodulated light, An optical splitter that splits and outputs an optical signal input from the unit. The first optical receiving device transmits the electric signal to be transmitted by passing a component included in a low band of the electric signal obtained by performing photoelectric conversion on the optical signal transmitted from the optical transmitting device. A low-pass filter unit that outputs a signal, wherein the second optical receiving device passes a component included in a high band of an electric signal obtained by performing photoelectric conversion of the optical signal transmitted from the optical transmitting device. An optical transmitting and receiving device, comprising: a high-pass filter unit that outputs a signal obtained by modulating the subcarrier with the electric signal to be transmitted. 23. An optical transmission / reception device in which an optical transmission device and an optical reception device are connected to be capable of optical transmission, wherein the optical transmission device outputs a first unmodulated light having a first optical frequency. A light source; an external light modulation unit that generates and outputs a modulated light signal by amplitude-modulating the first unmodulated light input from the first light source with an electric signal to be transmitted input from the outside; A second light source that outputs a second unmodulated light having a second optical frequency that is different from the first optical frequency by a predetermined optical frequency, a modulated optical signal that is input from the external light modulator, and a second optical source that is input from the second light source An optical multiplexing unit that generates and outputs an optical signal by multiplexing the second unmodulated light with the polarization of the modulated optical signal and the second unmodulated light, An optical splitter that splits and outputs an optical signal input from the unit. An optical-to-electrical conversion unit that performs optical-to-electrical conversion on the optical signal transmitted from the optical transmission device and outputs an electric signal; and at least two electric signals that are input from the optical to electric conversion unit. A distributing unit for distributing, a low-pass filter unit for outputting the electric signal to be transmitted by passing a component included in a low band of the electric signal distributed by the distributing unit; A high-pass filter unit that outputs a signal obtained by modulating the subcarrier with the electric signal to be transmitted by passing a component included in a high band of the electric signal. 24. A stage after the high-pass filter section,
21. An antenna unit for radiating a signal obtained by modulating a subcarrier with the electric signal to be transmitted output from the high-pass filter unit to a space is provided. 24. The optical transmitting / receiving device according to any one of claims to 23. 25. The electric signal to be transmitted, wherein an intermediate frequency carrier having a lower frequency than a subcarrier outputted from the local oscillator is modulated with analog information or digital information. The optical transceiver according to any one of claims 7, 13, 14, and 20 to 23.