JP3937237B2 - Optical frequency shift keying modulator - Google Patents

Description

  The present invention relates to an optical frequency shift keying modulator and the like.

  Optical frequency shift keying (optical FSK) is a technique for modulating the frequency of light and transmitting the frequency difference as a signal. Since the FSK signal generally has no information in its amplitude, it is characterized by being hardly affected by level fluctuations and noise.

  An FSK system using a digital signal is already known (for example, see Japanese Patent Application Laid-Open No. 11-17746 (Patent Document 1)). However, this technique relates only to shifting the frequency of a digital signal, and does not shift the frequency of light.

  An optical FSK system is a system that shifts the frequency of light. In the conventional optical FSK system, the laser oscillation wavelength itself is changed by changing the current supplied to the wavelength tunable laser light source. On the receiver side, the wavelength is divided into components by a demultiplexer, converted into an electric signal by a photodetector, the intensity is measured, and the difference is taken by a subtractor. However, in such an optical FSK system, there is a problem that the intensity of the laser also changes as the wavelength of the laser changes, and this must be compensated. Furthermore, there is a problem that it cannot cope with the high speed.

An optical single sideband modulator (optical SSB (Single Slide-Band) modulator) is known as a device that can convert the frequency of input light. FIG. 1 is a block diagram showing the basic configuration of the optical SSB modulator. As shown in FIG. 1, the optical SSB modulator 1 includes a first sub Mach-Zehnder waveguide (MZ _A ) 2, a second sub-Mach-Zehnder waveguide (MZ _B ) 3, the MZ _A and the The phase of light propagating through the two arms of the MZ _A by controlling the bias voltage between the two arms constituting the MZ _A and the main Mach-Zehnder waveguide (MZ _C ) 4 having the MZ _B a first electrode (DC _a electrode) 5 for controlling, by controlling the bias voltage between the two arms composing the MZ _B, to control the phase of the light propagating in the two arms of the MZ _B The second electrode (DC _B electrode) 6, the first RF electrode (RF _A electrode) 7 for inputting a radio frequency (RF) signal to the two arms constituting the MZ _A , and the MZ _B are constituted. Input RF signal to two arms The two of the RF electrode (RF _B electrode) 8, the MZ _A and the MZ DC or low frequency for controlling the phase of light propagating the MZ _A and the MZ _B by controlling the bias voltage of _B that And an electrode (DC _C electrode) 9. The “low frequency” in the low frequency electrode means, for example, a frequency of 0 Hz to 500 MHz.

That is, in the optical SSB modulator, a direct current or low frequency electrode (DC _C electrode) is used to control the phase of light propagating through MZ _A and MZ _B. As for optical SSB modulators (Shimotsu et al., “Optical SSB Modulation Using Integrated LN Modulator”, IEICE Technical Report, OEIC. OPE2000-37, LQE2000-31 (2000-07), 29-34 , 2000).

The frequency of the output light can be changed also by the optical SSB modulator. However, since the response speed of the control circuit for changing the frequency is limited, the speed of the frequency change by the optical SSB modulator is about 10 ns. Originally, the optical SSB modulator is not intended to shift the frequency of output light at high speed and use the shifted frequency as information. Therefore, there is a problem that the optical SSB modulator is not necessarily suitable for the optical FSK modulator.
Japanese Patent Laid-Open No. 11-17746

  An object of the present invention is to provide an optical FSK modulator that can be used for optical information communication and the like.

  It is an object of the present invention to provide an optical FSK modulator that can be used for optical information communication and the like and can transmit information at high speed.

  It is an object of the present invention to provide an optical FSK modulator that can be used for optical information communication and the like and is relatively space-saving.

  An object of the present invention is to provide an optical FSK modulator used for optical multiplex information communication including a change in amplitude of output light and a change in frequency.

  An object of the present invention is to provide an optical FSK modulator that can provide a new millimeter-wave source and microwave source.

  An object of the present invention is to provide an optical information transmission method using optical FSK.

  An object of the present invention is to provide an optical FSK communication system, which is an optical information transmission system using optical FSK.

  An object of the present invention is to provide a multilevel modulated optical FSK communication system.

  An object of the present invention is to provide an optical FSK that is an optical information transmission system using optical FSK and optical intensity modulation, and an optical intensity modulation communication system.

  It is an object of the present invention to provide a millimeter wave / microwave generation method using an optical FSK modulator.

  An object of the present invention is to provide a UWB wireless communication system using an optical FSK modulator.

(1) In order to solve at least one of the above-described problems, an optical FSK modulator of the present invention includes a first sub Mach-Zehnder waveguide (MZ _A ), a second sub-Mach-Zehnder waveguide (MZ _B ), _A main Mach-Zehnder waveguide (MZ _C ) including the MZ _A and the MZ _B, and having a light input portion and a modulated light output portion, and two arms constituting the MZ _{A A} first RF electrode (RF _A electrode) for inputting a radio frequency (RF) signal and a second RF electrode (RF _B electrode) for inputting an RF signal to the two arms constituting the MZ _B are inputted. A traveling wave electrode (RF _C electrode) for controlling the frequency of light output from the output unit by controlling the voltage of the RF signal, and the voltage of the RF signal input to the RF _C electrode By controlling from the output unit Modulates the frequency of the output light.

The optical FSK modulator of the present invention is a conventional optical SSB modulator, and performs frequency modulation with an RF _C electrode, which is a traveling wave electrode, in a portion corresponding to a DC _C electrode. A frequency shift signal can be output. For this reason, the optical FSK modulator of the present invention leads to an increase in transmission rate. In addition, in the optical FSK modulator of the present invention, unlike the conventional optical FSK modulator, the power supplied to the light source can be kept constant without changing the light source wavelength, so that a parasitic intensity change can be prevented. . As a result, in the optical communication system using the optical FSK modulator of the present invention, an intensity modulator for intensity change compensation becomes unnecessary, and a simple system and a more accurate system can be achieved. Further, in the optical FSK modulator of the present invention, the wavelength shift amount can be matched with twice the frequency of the high-frequency power signal, and the wavelength shift amount is accurate.

  Furthermore, according to the optical FSK modulator of the present invention, when the RFc signal is a rectangular pulse having a short rise time and a short fall time, a UWB signal can be easily generated. That is, according to the present invention, a new millimeter wave source and microwave source can be provided.

(2) In the optical FSK modulator of the present invention, preferably, resonant electrodes are used as the RF _A electrode and the RF _B electrode. Since resonant electrodes are used as the RF _A electrode and the RF _B electrode, the optical FSK modulator can be reduced in size and efficiency.

(3) In the optical FSK modulator of the present invention, preferably, by controlling the bias voltage between two arms composing the MZ _A, first to control the phase of light propagating two arms of the MZ _A a first direct current or low frequency electrode (DC _a electrode), by controlling the bias voltage between two arms composing the MZ _B, first to control the phase of the light propagating in the two arms of the MZ _B 2 direct current or low frequency electrodes (DC _B electrodes). In this example, since the DC electrode and the RF electrode are provided separately, a circuit for superimposing the DC electrode and the RF electrode on the outside of the MZ interferometer becomes unnecessary.

(4) In the optical FSK modulator of the present invention, the preferably, by controlling the bias voltage between two arms composing the MZ _C, to control the phase of the light propagating in the two arms of the MZ _C 3 direct current or low frequency electrodes (DC _C electrodes).

(5) In order to solve at least one of the above-described problems, an optical information transmission method of the present invention includes a light introducing step of introducing light into the light input unit using the optical frequency shift keying modulator, An RF signal input process for inputting an RF signal to the RF _A electrode and the RF _B electrode, and a frequency of the light output from the output unit by controlling the frequency of the RF signal input to the RF _C electrode. And an output optical frequency shift process.

In the present invention, since the traveling wave type electrode is used as the RF _C electrode, the frequency of the output light can be modulated at high speed. For this reason, since the frequency change of light can be efficiently transmitted as information, the present invention is effective as an optical information transmission method.

(6) In the optical information transmission method of the present invention, more preferably, the signal input to the RF _C electrode has a frequency component of 500 MHz or more.

(7) The optical information transmission method of the present invention more preferably modulates the amplitude of the output light by controlling the intensity of the RF signal input to one or both of the RF _A electrode and the RF _B electrode. The amplitude is transmitted as information.

  By transmitting not only the change in optical frequency but also the change in optical amplitude as information, more information can be transmitted at a time.

  (8) In order to solve at least one of the above-described problems, an optical FSK communication system of the present invention is an optical communication system including a transmitter, a receiver, and a fiber connecting the transmitter and the receiver. The transmitter includes: a laser light source; the optical frequency shift keying modulator according to any one of (1) to (4) to which light from the laser light source is input; and the optical frequency shift keying modulator. A signal source for outputting a signal to be transmitted, and a high-frequency electrical signal source for providing a high-frequency electrical signal to the optical frequency shift keying modulator, wherein the receiver transmits light transmitted from the transmitter A demultiplexer for demultiplexing the signal according to its wavelength, a first photodetector for detecting one optical signal demultiplexed by the demultiplexer, and demultiplexed by the demultiplexer Detect remaining optical signal Comprising a second light detector because the output signal of the first photodetector, and a subtractor for calculating a difference between said second output signal of the photodetector.

  In the optical FSK communication system of the present invention, since the power supplied to the light source can be kept constant without changing the light source wavelength as in the conventional optical FSK communication system, it is possible to prevent a parasitic intensity change from occurring. Thereby, in the optical FSK communication system of the present invention, an intensity modulator for intensity compensation becomes unnecessary, and a simple system and a more accurate system can be achieved.

  (9) As another aspect of the optical FSK communication system of the present invention, the optical FSK communication system according to the above (7) in which the signal source can set and switch a plurality of voltage levels. . This communication system is called a multi-level modulation optical FSK communication system.

  In the multi-level modulated optical FSK communication system, an output signal having a plurality of output intensities can be obtained, so that information on the output signal is further increased.

(10) In order to solve at least one of the above problems, the optical FSK and optical intensity modulation communication system of the present invention includes a transmitter, a receiver, and a fiber that connects the transmitter and the receiver. In the communication system, the transmitter receives a laser light source, a light intensity modulator that modulates the intensity of light from the laser light source, and light from the laser light source that has modulated the intensity by the light intensity modulator. The optical frequency shift keying modulator according to any one of (1) to (4), an intensity modulation signal source for outputting a signal to be transmitted to the optical intensity modulator, and the optical frequency shift keying A signal source for outputting a signal to be transmitted to the modulator, and a high-frequency electrical signal source for providing a high-frequency electrical signal to the optical frequency shift keying modulator, wherein the receiver is the transmitter An intensity measurement photodetector for measuring the intensity of the transmitted optical signal, a demultiplexer for demultiplexing the optical signal transmitted from the transmitter according to its wavelength, and demultiplexing by the demultiplexer A first optical detector for detecting one of the optical signals, a second optical detector for detecting the remaining optical signal demultiplexed by the demultiplexer, and the first light A subtractor for calculating a difference between the output signal of the detector and the output signal of the second photodetector;

  The optical FSK and optical IM modulation communication system of the present invention can modulate the intensity of the laser light before the optical FSK modulation, and transmit a signal obtained by simultaneously applying the optical FSK and the optical intensity modulation.

  (11) Another aspect of the optical FSK and optical intensity modulation communication system of the present invention is an optical communication system including a transmitter, a receiver, and a fiber connecting the transmitter and the receiver. The transmitter includes a laser light source, the optical frequency shift keying modulator according to any one of (1) to (4) to which light from the laser light source is input, and the optical frequency shift keying modulator that adjusts the frequency. A light intensity modulator for modulating the intensity of light from the modulated laser light source, an intensity modulation signal source for outputting a signal to be transmitted to the light intensity modulator, and a light frequency shift keying modulator A signal source for outputting a signal, and a high-frequency electrical signal source for providing a high-frequency electrical signal to the optical frequency shift keying modulator, wherein the receiver transmits light transmitted from the transmitter An intensity measuring photodetector for measuring the intensity of the signal, a demultiplexer for demultiplexing the optical signal transmitted from the transmitter according to its wavelength, and one of the signals demultiplexed by the demultiplexer A first photodetector for detecting an optical signal, a second photodetector for detecting the remaining optical signal demultiplexed by the demultiplexer, and an output of the first photodetector A subtractor for calculating a difference between the signal and the output signal of the second photodetector.

  That is, in the optical FSK and optical intensity modulation communication system of this aspect, the optical intensity modulator modulates the intensity of light from the laser light source whose frequency is modulated by the optical frequency shift keying modulator.

(12) In order to achieve at least one of the above objects, millimeter and microwave pulse generator according to the present invention, the above (1) to (4) an optical frequency shift keying modulator according to any one of the An optical signal whose optical frequency is switched by the optical frequency shift keying modulator is input, and the frequency component is more than twice the frequency of the RF signal input to the RF _A electrode and the RF _B electrode of the optical frequency shift keying modulator. comprising a light detector capable of responding, the millimeter wave microwave to obtain a signal corresponding to the difference frequency of the upper sideband and the lower sideband which occurs when switching the optical frequency of the optical signal by the optical frequency shift keying modulator It is a pulse generator .
(13) A preferred embodiment of the millimeter wave / microwave pulse generator is the millimeter wave / microwave pulse generator according to the above (12), which uses a rectangular pulse as the RF signal input to the RF _C electrode.
(14) In order to solve at least one of the above-described problems, the millimeter-wave / microwave pulse generation method of the present invention includes the optical frequency shift keying modulator according to any one of (1) to (4) above. An optical signal whose optical frequency is switched by the optical frequency shift keying modulator is input, and a frequency component more than twice the RF signal frequency input to the RF _A electrode and the RF _B electrode of the optical frequency shift keying modulator is used. Using an optical detector that can respond, an optical signal whose optical frequency is switched by the optical frequency shift keying modulator is input to the optical detector, and generated when the optical frequency of the optical signal is switched by the optical frequency shift keying modulator This is a millimeter wave / microwave pulse generation method for obtaining a signal corresponding to the difference frequency between the upper sideband and the lower sideband .

In the millimeter wave / microwave pulse generation method of the present invention, since the optical FSK modulator described above is used, the signal applied to the RFc electrode is, for example, a high-frequency rectangular pulse with a rise time of 1% to 10%. Millimeter wave / microwave pulse can be obtained by using. In addition, since a photodetector capable of responding to a frequency component more than twice the frequency of the RF signal input to the RF _A electrode and RF _B electrode of the optical frequency shift keying modulator is used, such a millimeter wave / microwave is effective. Can be detected.

(15) In order to solve at least one of the above problems, the UWB wireless communication system of the present invention includes the optical frequency shift keying modulator according to any one of (1) to (4), and the optical frequency shift keying. A photodetector capable of receiving an optical signal whose optical frequency is switched by the modulator and responding to a frequency component more than twice the RF signal frequency inputted to the RF _A electrode and the RF _B electrode of the optical frequency shift keying modulator ; , provided to afford a UWB signal corresponding to the difference frequency of the upper sideband and the lower sideband which occurs when switching the optical frequency of the optical signal by the optical frequency shift keying modulator, using UWB signals obtained UWB A wireless communication system.

In the UWB wireless communication system of the present invention, since the optical FSK modulator described above is used, the signal applied to the RFc electrode is, for example, a high-frequency rectangular pulse having a rise time of 1% to 10%. Millimeter wave / microwave pulse can be obtained. In addition, since a photodetector capable of responding to a frequency component more than twice the RF signal frequency input to the RF _A electrode and RF _B electrode of the optical frequency shift keying modulator is used, such a millimeter wave / microwave is effective. Can be detected. Thus, the UWB wireless communication system of the present invention can achieve the UWB wireless communication system.

  According to the present invention, an optical FSK modulator that can be used for optical information communication and the like can be provided.

  According to the present invention, it is possible to provide an optical FSK modulator that can be used for optical information communication and the like and can transmit information at high speed.

  According to the present invention, it is possible to provide an optical FSK modulator that can be used for optical information communication and the like and is relatively space-saving.

  ADVANTAGE OF THE INVENTION According to this invention, the optical FSK modulator used for the optical multiplex information communication including the change of the amplitude of output light and the change of a frequency can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the optical FSK modulator which can provide a new millimeter wave source and a microwave source can be provided.

  According to the present invention, a new optical FSK information transmission method can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the optical FSK communication system which is an optical information transmission system by optical FSK can be provided.

  According to the present invention, a multilevel modulated optical FSK communication system can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the optical FSK which is an optical information transmission system by optical FSK and optical intensity modulation, and an optical intensity modulation communication system can be provided.

  According to the present invention, it is possible to provide a millimeter wave / microwave generation method using an optical FSK modulator.

  According to the present invention, a UWB wireless communication system using an optical FSK modulator can be provided.

(1. Optical FSK modulator)
Hereinafter, an optical FSK modulator 10 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the basic configuration of such an optical FSK modulator. As shown in FIG. 2, the optical FSK modulator of the present invention includes, for example, a first sub Mach-Zehnder waveguide (MZ _A ) 2, a second sub-Mach-Zehnder waveguide (MZ _B ) 3, and the MZ _A main Mach-Zehnder waveguide (MZ _C ) 4 including _A and the MZ _B, and having a light input portion and a modulated light output portion, and a bias between the two arms constituting the MZ _A By controlling the voltage, the first direct current or low frequency electrode (DC _A electrode) 5 for controlling the phase of light propagating through the two arms of the MZ _{A and} the two arms constituting the MZ _B The second DC or low frequency electrode (DC _B electrode) 6 for controlling the phase of the light propagating through the two arms of the MZ _B by controlling the bias voltage of the MZ _B , and the two constituting the MZ _A Radio frequency (RF) signal on arm A first RF electrode (RF _A electrode) 7 for inputting, a second RF electrode (RF _B electrode) 8 for inputting the RF signal to the two arms composing the MZ _B, the frequency of the RF signal input ; and a traveling-wave-type electrode (RF _C electrode) 11 for controlling the frequency of light output from the output unit by controlling.

(1.1. Mach-Zehnder waveguide)
Each Mach-Zehnder waveguide is configured to include, for example, two phase modulators in parallel. 2 includes a first sub Mach-Zehnder waveguide (MZ _A ) 2, a second sub-Mach-Zehnder waveguide (MZ _B ) 3, the MZ _A and the MZ _B, and inputs light. And a main Mach-Zehnder waveguide (MZ _C ) 4 having a modulated light output portion.

(1.2. Substrate)
The substrate material is preferably an electro-optic crystal such as lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution, and particularly preferably an X-cut (X-cut) LiNbO ₃ substrate. As a method for forming the optical waveguide, a known forming method such as an internal diffusion method such as a titanium diffusion method or a proton exchange method can be used. That is, the optical FSK modulator of the present invention can be manufactured, for example, as follows. First, titanium is patterned on a lithium niobate wafer by a photolithography method, and the titanium is diffused by a thermal diffusion method to form an optical waveguide. The conditions at this time may be that the thickness of titanium is 100 to 2000 angstroms, the diffusion temperature is 500 to 2000 ° C., and the diffusion time is 10 to 40 hours. An insulating buffer layer (thickness 0.5-2 μm) of silicon dioxide is formed on the main surface of the substrate. Next, an electrode made of metal plating having a thickness of 15 to 30 μm is formed thereon. The wafer is then cut. In this way, an optical modulator in which a titanium diffusion waveguide is formed is formed.

(1.3. Resonance type electrode)
A resonance type photoelectrode (resonance type optical modulator) is an electrode that performs modulation using resonance of a modulation signal. A well-known thing can be employ | adopted as a resonance type electrode, For example, the thing of Unexamined-Japanese-Patent No. 2002-268025 is employable.

(1.4. Traveling wave type electrode)
A traveling wave type electrode (traveling wave type optical modulator) is an electrode (modulator) that modulates light while guiding a light wave and an electric signal in the same direction (for example, Hiroshi Nishihara, Haruna). Masamitsu, Toshiaki Sugawara, “Optical Integrated Circuit” (Revised Supplement), Ohmsha, pp. 119-120). As the traveling wave type electrode, known ones can be adopted. For example, Japanese Patent Application Laid-Open Nos. 11-295574, 11-295684, 2002-169133, 2002-40381, 2000- Those disclosed in JP 267056 A, JP 2000-47159 A, JP 10-133159 A, and the like can be used.

  The traveling wave electrode preferably employs a so-called symmetrical ground electrode arrangement (having at least a pair of ground electrodes on both sides of the traveling wave signal electrode). Thus, by arranging the ground electrodes symmetrically across the signal electrodes, the high frequency output from the signal electrodes is easily applied to the ground electrodes arranged on the left and right sides of the signal electrodes. Can be suppressed.

(2. Operation of optical FSK modulator)
The operation of the optical FSK modulator will be described below. Sinusoidal RF signals whose phases are different by 90 ° are input to four optical phase modulators in parallel. Also for the light, the bias voltage DC _A electrode, DC _B electrode, and RF _C electrode are adjusted so that each phase difference is 90 °. Then, light whose frequency is shifted by the frequency of the RF signal is output. The direction (decrease / increase) of the frequency shift can be selected by setting the bias voltage. That is, each phase modulator has a phase difference of 90 ° for both electricity and light. When an X-cut substrate is used as the substrate, only four sine modulators are used to supply the RF signal electrode RF _A electrode and RF _B electrode with a sine wave having a phase difference of 90 °. The modulation of RF signals of 90 °, 180 °, and 270 ° can be realized (Hisumi et al., X-cut Lithium Niobium Optical SSB Modulator, Electron Letter, vol. 37, 515-516 (2001)).

FIG. 3 is a conceptual diagram showing an optical spectrum at each point of the optical FSK modulator. The arrow in the figure represents light. In each MZ structure part of FIG. 2, the bias voltage of the DC _A electrode and the DC _B electrode is adjusted so that the light phase difference between the two paths (path 1 and path 3, path 2 and path 4) is 180 °. (Left in FIG. 3). The bias voltage of the RF _C electrode is adjusted so that the optical phase difference between the two MZ structure portions is 90 °. There are double sidebands at the points P and Q in FIG. 2 (center of FIG. 3). However, the phase of the lower sideband is opposite at point P and point Q. For this reason, only the upper side wave component is included in the output light obtained by combining these lights (right side in FIG. 3).

On the other hand, when the bias voltage of the RF _C electrode is adjusted so that the optical phase difference between the two MZ structure portions is 270 °, only the lower side wave component is output. Therefore, by switching the signal voltage of the RF _C electrode, it can be output by switching the upper side band component and a lower side band component. It is also possible to switch the signal current or signal frequency RF _C electrode.

In the present invention, since the traveling wave electrode corresponding to the RF frequency is used as the RF _C electrode, the above-described frequency shift can be performed at high speed. Therefore, the present invention can provide an optical FSK modulator and an optical information transmission method using the optical FSK modulator.

(3. Optical FSK communication system)
The optical FSK communication system is a system for optical information communication using optical frequency shift keying. The optical FSK communication system of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing the basic configuration of the optical FSK communication system of the present invention. As shown in FIG. 4, the optical FSK communication system of the present invention is similar to a normal optical communication system in that a transmitter (21), a receiver (22), and a fiber connecting the transmitter and the receiver are connected. (23).

(3.1. Transmitter)
As shown in FIG. 4, the transmitter (21) in the optical FSK communication system of the present invention includes a laser light source (24), an optical FSK modulator (25) to which light from the laser light source is input, A signal source (26) for outputting a signal to be transmitted to the optical FSK modulator and a high-frequency electric signal source (27) for supplying a high-frequency electric signal to the optical frequency shift keying modulator are provided.

(3.1.1. Laser light source)
The laser light source (24) is a device for generating a laser. In the conventional optical FSK system, the wavelength of the laser itself generated from the laser light source is changed. However, in the optical FSK modulator and the optical FSK communication system of the present invention, since the optical modulator is used, the output of the laser light source itself can be kept constant.

(3.1.2. Optical FSK modulator)
As the optical FSK modulator (25), the optical FSK modulator described above can be used.

(3.1.3. Signal source)
The signal source (26) is a device for outputting a signal to be transmitted to the optical FSK modulator, and a known signal source can be adopted. The signal source (FSK signal source) controls a signal transmitted to the RF _C electrode of the optical FSK modulator. Using a signal source that can be switched by setting a plurality of voltage levels is an aspect related to optical FSK communication capable of multi-level modulation. The signal input from the signal source to the RF _C electrode is preferably a signal having a frequency component of 500 MHz or more and 300 GHz or less, preferably 500 MHz to 10 GHz. The frequency of the signal transmitted to the RF _C electrode controlled by the signal source is preferably smaller than the frequency of the signal transmitted to the RF _A electrode and the RF _B electrode controlled by the high frequency electric signal source described later. If the frequency of the signal transmitted to the RF _C electrode controlled by the signal source is larger than the frequency of the signal transmitted to the RF _A electrode and the RF _B electrode controlled by the high frequency electric signal source described later, the apparatus becomes complicated. Because.

(3.1.4. High frequency electrical signal source)
The high-frequency electric signal source (27) is a device for supplying a high-frequency electric signal to the optical frequency shift keying modulator, and a known high-frequency electric signal source can be adopted. The high-frequency electrical signal source mainly controls signals transmitted to the RF _A electrode and the RF _B electrode. Examples of the high frequency include 1 GHz to 100 GHz. Examples of the output of the high-frequency electric signal source include a sine wave having a constant frequency.

(3.2. Receiver)
As shown in FIG. 4, the receiver (22) in the optical FSK communication system of the present invention includes a duplexer (28) that demultiplexes an optical signal transmitted from the transmitter according to its wavelength, A first photodetector (29) for detecting one optical signal demultiplexed by the demultiplexer, and a second light for detecting the remaining optical signal demultiplexed by the demultiplexer A detector (30); and a subtractor (31) for calculating a difference between the output signal of the first photodetector and the output signal of the second photodetector.

(3.2.1. Splitter)
The demultiplexer (28) is a device that demultiplexes the optical signal transmitted from the transmitter in accordance with its wavelength, and a known demultiplexer can be employed.

(3.2.2. Photodetector)
The photodetectors (29, 30) are devices for detecting an optical signal demultiplexed by the demultiplexer, and a known photodetector can be adopted. As this photodetector, for example, a device including a photodiode can be employed. Examples of the photodetector include one that detects an optical signal and converts it into an electrical signal. The intensity of the optical signal can be detected by the photodetector.

(3.2.3. Subtractor)
The subtractor (31) is a device including a calculation circuit for calculating a difference between the output signal of the first photodetector and the output signal of the second photodetector, and a known subtractor can be employed. .

(4. Operation of optical FSK communication system)
Hereinafter, an example of the operation of the optical FSK communication system will be described. Light from the laser light source is input to the optical FSK modulator (25). In the optical FSK modulator, a predetermined signal is applied to the RF _C electrode by the signal source (26), and a predetermined signal is applied to the RF _A electrode and the RF _B electrode from the high frequency electric signal source (27). As a result, a predetermined signal is transmitted from the transmitter.

  FIG. 5 is a graph showing an example of an output spectrum from the optical FSK modulator. In this example, the laser beam is a 193 THz, 0 dBm laser beam, the signal from the signal source is a 2.5 Gbps NRZ signal, the signal from the high frequency electrical signal source is a 10 GHz signal, and the phase change in the optical FSK modulator The amount was 105 degrees.

  The output consisting mainly of two frequency components as shown in FIG. 5 reaches the receiver through an optical fiber such as a single mode fiber.

  In the receiver (22), the duplexer (28) demultiplexes the optical signal transmitted from the transmitter according to the wavelength. The first photodetector (29) detects one optical signal demultiplexed by the demultiplexer. The second photodetector (30) detects the remaining optical signal demultiplexed by the demultiplexer. The subtractor (31) calculates a difference between the output signal of the first photodetector and the output signal of the second photodetector. The signal obtained by the subtracter is output to a monitor (not shown).

  FIG. 6 is an eye diagram of the output signal output in this way. In this example, the transmitter described above is used, a 50 km single-mode fiber is used as an optical fiber, an optical signal is amplified by an optical amplifier having a constant output mode of 10 dBm after transmission through the optical fiber, and the optical detector The output is smoothed by a Bessel filter having a cutoff frequency of 2.5 G × 0.75 Hz. FIG. 6 shows that a good eye opening is obtained, and that the optical FSK communication system of the present invention is capable of digital signal transmission.

(5. Operation of multilevel modulated optical FSK communication system)
In the multi-level modulation optical FSK communication system, in the operation of the optical FSK communication system described above, the signal source is achieved by setting and switching a plurality of voltage levels. In the optical FSK communication system described above, the output signal is “1” or “−1”. However, in the multilevel modulated optical FSK communication system, the intensity of light of two types of wavelengths output from the optical FSK modulator can be adjusted, so that output signals of a plurality of levels can be obtained.

  FIG. 7 is a diagram for explaining signal output having values in five stages. In FIG. 7, the outputs from the optical FSK modulator are λ1 and λ2. That is, in the subtracter, the output signal derived from λ2 is subtracted from the output signal derived from λ1. In the example shown in FIG. 7, five-stage outputs “1”, “0.5”, “0”, “−0.5”, and “−1” can be obtained.

(6. Optical FSK and optical intensity modulation communication system)
The optical FSK and optical intensity modulation communication system of the present invention will be described with reference to the drawings. FIG. 8 is a schematic diagram showing the basic configuration of the optical FSK and optical intensity modulation communication system of the present invention. As shown in FIG. 8, the optical FSK and optical intensity modulation communication system of the present invention includes a transmitter (21), a receiver (22), a transmitter and a receiver, as in a normal optical communication system. (23).

(6.1. Transmitter)
As shown in FIG. 8, the transmitter (21) includes a laser light source (24), a light intensity modulator (32) for modulating the intensity of light from the laser light source, and the light intensity modulator. An optical frequency shift keying modulator (25) to which light from a laser light source modulated is input, an intensity modulation signal source (33) for outputting a signal to be transmitted to the optical intensity modulator, and the optical frequency A signal source (FSK signal source) (26) for outputting a signal to be transmitted to the shift keying modulator, and a high frequency electrical signal source (27) for supplying a high frequency electrical signal to the optical frequency shift keying modulator. It has. Among the configurations of the transmitter, those described earlier in the description of the optical FSK communication system can be similarly used.

Although not particularly illustrated, the transmitter (21) includes a laser light source (24), an optical frequency shift keying modulator (25) to which light from the laser light source is input, and the optical frequency shift keying modulator. A light intensity modulator (32) for modulating the intensity of light from a laser light source whose frequency is modulated, an intensity modulation signal source (33) for outputting a signal to be transmitted to the light intensity modulator, and the light A signal source (FSK signal source: 26) for outputting a signal to be transmitted to the frequency shift keying modulator, and a high frequency electric signal source (27) for supplying a high frequency electric signal to the optical frequency shift keying modulator. What is provided is a mode different from the optical FSK and optical intensity modulation communication system of the present invention described above.
(6.1.1. Light intensity modulator)
The light intensity modulator (32) is a device for modulating the intensity of light from the laser light source, and a known light intensity modulator can be adopted. The light intensity modulator may directly modulate the intensity of output light from the laser light source, or may modulate the intensity of output light from the optical frequency shift keying modulator.

(6.1.2. Intensity modulation signal source)
The intensity modulation signal source is a device for outputting a signal to be transmitted to the light intensity modulator, and a known intensity modulation signal source can be adopted.

(6.2. Receiver)
As shown in FIG. 8, the optical FSK of the present invention and the receiver (22) in the optical intensity modulation communication system are an intensity measurement photodetector for measuring the intensity of the optical signal transmitted from the transmitter. (34), a demultiplexer (28) for demultiplexing the optical signal transmitted from the transmitter according to its wavelength, and a first demultiplexer for detecting one of the optical signals demultiplexed by the demultiplexer. 1 photo detector (29), a second photo detector (30) for detecting the remaining optical signal demultiplexed by the demultiplexer, and an output signal of the first photo detector And a subtractor (31) for calculating a difference from the output signal of the second photodetector. Of the configuration of the receiver, the same components as those described in the description of the optical FSK communication system can be used in the same manner.

(6.2.1. Photodetector for intensity measurement)
The intensity measurement photodetector (34) is a device for measuring the intensity of the optical signal transmitted from the transmitter, and a known photodetector can be adopted.

(7. Operation of optical FSK and optical intensity modulation communication system)
The operations of the optical FSK and optical intensity modulation communication system of the present invention are basically the same as those of the optical FSK communication system described above. In the optical FSK and optical intensity modulation communication system of the present invention, the intensity of light from a laser light source is modulated, and the intensity of the optical signal is measured before demultiplexing the optical signal transmitted from the transmitter.

  FIG. 9 is a graph showing an example of an output spectrum from the optical FSK modulator in the optical FSK and optical intensity modulation communication system. In this example, the laser light is 193 THz, 0 dBm laser light, the extinction ratio in the light intensity modulator is 10 dB, the signal from the light intensity modulation signal is an NRZ signal of 20 Gbps, and the signal from the FSK signal source is 1 Gbps. The signal from the high-frequency electrical signal source was a 50 GHz signal, and the phase change amount in the optical FSK modulator was 105 degrees.

  The output mainly composed of two frequency components as shown in FIG. 9 reaches the receiver through an optical fiber such as a single mode fiber.

  In the receiver (22), a light detector (34) for detecting light intensity detects the intensity of the optical signal. A demultiplexer (28) demultiplexes the optical signal transmitted from the transmitter according to its wavelength. The first photodetector (29) detects one optical signal demultiplexed by the demultiplexer. The second photodetector (30) detects the remaining optical signal demultiplexed by the demultiplexer. The subtractor (31) calculates a difference between the output signal of the first photodetector and the output signal of the second photodetector. The signal obtained by the subtracter is output to a monitor (not shown).

  FIG. 10 is an eye diagram of the output signal output in this way. FIG. 10A shows the output signal of the light detector for detecting the light intensity, and FIG. 10B shows the output signal obtained by the subtractor. In this example, the transmitter described above is used, and a 50 km single mode fiber is used as the optical fiber. After transmitting the optical fiber, the output of the photodetector for detecting the light intensity is smoothed with a Bessel filter having a cutoff frequency of 30 GHz. The output obtained by the subtractor is smoothed by a Bessel filter having a cutoff frequency of 2 GHz. From FIG. 10A, it can be seen that a good eye opening is obtained at the output of the light detector for detecting the light intensity, and that digital signal transmission is possible. Further, from FIG. 10B, it can be seen that the output obtained by the subtractor has a large variance at the zero level and the mark level due to the influence of intensity modulation, but the eye opening is secured. From the above, it can be seen that in the optical FSK and optical intensity modulation communication system of the present invention, the intensity modulation signal and the FSK signal can be transmitted simultaneously.

(8. Millimeter wave / microwave pulse generation method)
Hereinafter, the millimeter wave / microwave pulse generation method of the present invention will be described. The method for generating millimeter-wave / microwave pulses according to the present invention is responsive to an optical frequency shift keying modulator and a frequency component more than twice the RF signal frequency input to the RF _A electrode and the RF _B electrode of the optical frequency shift keying modulator. This is a millimeter-wave / microwave pulse generation method using a photo detector. As such a photodetector, “single traveling carrier photodiode” (Tadao Ishibashi, Hiroshi Ito, “single traveling carrier photodiode”, Applied Physics, Vol. 70, No. 11, p.1304- 1307 (2001)).

The millimeter-wave / microwave pulse generation method of the present invention utilizes the phenomenon that in the optical FSK modulator, two components of the upper sideband and the lower sideband are transiently generated simultaneously when the optical frequency is switched. When the output light of the modulator is guided to a photodetector that can respond to a frequency component greater than the frequency difference between these two components (twice the RF signal frequency input to the RF _A and RF _B electrodes), the two components are generated simultaneously. An RF signal having a frequency corresponding to the frequency difference is generated only during the period. Since this is a transient phenomenon at the time of frequency switching, if the signal for switching the optical frequency (RF _C ) is a rectangular pulse with a short rise / fall time, an RF signal can be generated for a very short time.

That is, the generation method of the millimeter wave / microwave pulse of the present invention uses the optical FSK modulator described above, and the signal applied to the RFc electrode is, for example, a high-frequency rectangular pulse, and the rise time is 1% to 10%. % Millimeter wave / microwave pulse is obtained. Moreover, since the UWB signal can be obtained by using the millimeter wave / microwave pulse obtained in this way, a UWB wireless communication system can be obtained. For example, when a rectangular pulse with a rise time of 0.05 nanoseconds is input to RF _C and the RF signal frequency input to the RF _A electrode and the RF _B electrode is 25 GHz, a 50 GHz RF signal (UWB signal with a pulse width of 0.1 nanoseconds). ) Is obtained.

  The UWB wireless communication system is a wireless system using a very wide frequency band (several GHz to several tens GHz) using a very narrow pulse (impulse wave) of 1 nanosecond or less. This system is used for remote sensing. By using this method, it is possible to realize communication at a high data transmission rate with less power consumption than in the prior art. The bandwidth of the UWB wireless communication system is a bandwidth that is more than 1000 times that of existing wideband CDMA (Wideband CDMA). A specific bandwidth = (bandwidth) / (center frequency) of 25% or more is usually called UWB.

  The UWB wireless communication system is characterized by extremely low power spectrum density (noise level, DS-SS (Spread Spectrum System Using Direct Spreading or less)). In addition, the UWB wireless communication system is characterized in that it can coexist with little interference and interference with existing communication systems. The UWB wireless communication system is characterized in that it can transmit several kilometers with an average power level of 1 mW or less. In addition, since the UWB wireless communication system uses extremely short (ns unit) pulses, it has a characteristic of being strong against multipaths (that is, having a high path separation capability) by RAKE reception, and when used as a radar. Has a feature that high-precision distance measurement (in several centimeters) is possible (having high distance resolution). The UWB wireless communication system has a feature that a small size and low power consumption system can be constructed because there is no carrier and signal emission time is extremely short. Since the UWB wireless communication system can always occupy a wide band (eg, on the order of GHz), large-capacity multiple access / ultra-high-speed transmission (<several hundred Mbps) is possible. The UWB wireless communication system can be applied to ITS (Vehicle-to-Vehicle Communication, etc.) because it can perform communication and ranging at the same time.

Since the carrier frequency of the UWB signal is twice that of the high frequency electric signal source, a signal having a high frequency component can be generated and the frequency can be easily controlled. Since the pulse waveform of the UWB signal is determined by the RF _C signal waveform, the pulse shape of the UWB signal can be easily controlled by adjusting the rise time, for example.

FIG. 11 is a graph changed to a drawing showing an example of the waveform of the output signal output by the millimeter wave / microwave pulse generation method of the present invention. 11A shows a UWB signal (millimeter wave / microwave pulse), and FIG. 11B shows an enlarged view thereof. In this example, using the transmitter (FIG. 4; 21) of the optical FSK communication system described above, the signal from the signal source is a 1 GHz repetitive rectangular pulse with a rise time of 5%, and the signal from the high-frequency electric signal source is used. The signal was a 25 GHz signal and detected using a high-speed photodetector. Incidentally, when the optical phase change due to RF _C is P, the envelope of the photodetector output is expressed by COS (P / 2) SIN ( P / 2). Here, when P = 0 degrees, only λ1 is output, and when P = 180 degrees, only λ2 is output. In the transient state, 0 <P <180 degrees and an RF signal is generated from the photodetector. From FIG. 11, it can be seen that a UWB signal can be obtained by using the optical FSK modulator of the present invention.

  Since the optical FSK modulator of the present invention can obtain a signal with a good S / N ratio without changing the intensity of light, it is preferably used in an optical information transmission system.

  Further, the optical FSK modulator of the present invention can modulate the phase of light at high speed, and therefore can be used for high-speed optical information communication.

  The optical FSK modulator of the present invention can be suitably used in an optical information transmission system combined with an intensity modulation technique because it can perform phase modulation on the label portion of an optical packet.

Furthermore, the optical FSK modulator of the present invention can control the amplitude of the output light by controlling the intensity of the RF signal input from the RF _A electrode and the RF _B electrode. Therefore, it is suitably used for an optical information transmission system that performs optical frequency modulation and optical amplitude modulation together with frequency control of output light at the RF _C electrode.

  Furthermore, since the optical FSK modulator of the present invention is a new device for generating RF pulses, it is preferably used as a new millimeter wave source for transmission in the millimeter wave region.

  The optical FSK communication system of the present invention can be used as an optical information transmission system.

  The multilevel modulated optical FSK communication system of the present invention can be used as an optical information transmission system.

  The optical FSK and optical intensity modulation communication system of the present invention can be used as an optical information transmission system.

  The millimeter wave / microwave generation method of the present invention can be used as a new millimeter wave / microwave generation method in an optical information transmission system or the like.

  The UWB wireless communication system of the present invention can be used in various information communication fields such as ITS.

FIG. 1 is a block diagram showing a basic configuration of an optical SSB modulator. FIG. 2 is a block diagram showing the basic configuration of the optical FSK modulator according to the first embodiment of the present invention. FIG. 3 is a conceptual diagram showing an optical spectrum at each point of the optical FSK modulator (FIG. 2). FIG. 4 is a block diagram showing the basic configuration of the optical FSK communication system of the present invention. FIG. 5 is a graph showing an example of an output spectrum from the optical FSK modulator. FIG. 6 is an eye diagram of an output signal in the optical FSK communication system. FIG. 7 is a diagram for explaining signal output having values in five stages. FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, and FIG. 7E show “1”, “0.5”, “0”, “−0”, respectively. .5 "and" -1 "are given. FIG. 8 is a schematic diagram showing the basic configuration of the optical FSK and optical intensity modulation communication system of the present invention. FIG. 9 is a graph showing an example of an output spectrum from the optical FSK modulator in the optical FSK and optical intensity modulation communication system. FIG. 10 is an eye diagram of an output signal in the optical FSK and optical intensity modulation communication system. FIG. 10A shows the output signal of the light detector for detecting the light intensity, and FIG. 10B shows the output signal obtained by the subtractor. FIG. 11 is a graph changed to a drawing showing an example of the waveform of the output signal output by the millimeter wave / microwave pulse generation method of the present invention. 11A shows a UWB signal (millimeter wave / microwave pulse), and FIG. 11B shows an enlarged view thereof.

Explanation of symbols

1 optical SSB modulator 2 first sub Mach-Zehnder waveguide (MZ _A )
3 Second sub Mach-Zehnder waveguide (MZ _B )
4 Main Mach-Zehnder waveguide (MZ _C )
5 First electrode (DC _A electrode)
6 Second electrode (DC _B electrode)
7 First RF electrode (RF _A electrode)
8 Second RF electrode (RF _B electrode)
9 DC or low frequency electrode (DC _C electrode)
10 Optical FSK modulator 11 Third RF electrode (RF _C electrode)
DESCRIPTION OF SYMBOLS 21 Transmitter 22 Receiver 23 Fiber 24 Laser light source 25 Optical FSK modulator 26 Signal source 27 High frequency electric signal source 28 Demultiplexer 29 1st optical detector 30 2nd optical detector 31 Subtractor 32 Optical intensity modulator 33 Intensity modulation signal source 34 Intensity measurement photodetector

Claims (15)

A first sub-Mach-Zehnder waveguide (MZ _A ), a second sub-Mach-Zehnder waveguide (MZ _B ),
_A main Mach-Zehnder waveguide (MZ _C ) including the MZ _A and the MZ _B, and having a light input portion and a modulated light output portion;
_A first RF electrode (RF _A electrode) for inputting a radio frequency (RF) signal to the two arms constituting the MZ _A ;
A second RF electrode (RF _B electrode) for inputting an RF signal to the two arms constituting the MZ _B ;
A third RF electrode (RF _C electrode) that is a traveling wave electrode that controls the frequency of light output from the output unit by controlling the voltage of the input RF signal;
An optical frequency shift keying modulator that modulates the frequency of light output from the output unit by controlling the voltage of the RF signal input to the RF _C electrode, which is a traveling wave electrode corresponding to the RF signal. The optical frequency shift keying modulator according to claim 1, wherein a resonant electrode is used as the RF _A electrode and the RF _B electrode. _A first direct current or low frequency electrode (DC _A electrode) for controlling a phase of light propagating through the two arms of the MZ _A by controlling a bias voltage between the two arms constituting the MZ _A ; ,
By controlling the bias voltage between the two arms composing the MZ _B, the second direct current or low frequency electrode (DC _B electrode) for controlling the phase of the light propagating in the two arms of the MZ _B and ,
The optical frequency shift keying modulator according to claim 1 or 2, further comprising: By controlling the bias voltage between the two arms composing the MZ _C, a third DC or low frequency electrode to control the phase of the light propagating in the two arms of the MZ _C a (DC _C electrode) The optical frequency shift keying modulator according to any one of claims 1 to 3. An optical information transmission method using the optical frequency shift keying modulator according to any one of claims 1 to 4,
A light introduction step for introducing light into the light input section;
An RF signal input step of inputting an RF signal to the RF _A electrode and the RF _B electrode;
Light information transmission method and an output optical frequency shifting step of controlling the frequency of light output from the output unit by controlling the voltage of the signal input to the RF _C electrode. 6. The optical information transmission method according to claim 5, wherein the signal input to the RF _C electrode has a frequency component of 500 MHz or more. 6. The light according to claim 5, wherein the amplitude of the output light is modulated by controlling the intensity of the RF signal input to one or both of the RF _A electrode and the RF _B electrode, and the modulated amplitude is also transmitted as information. Information transmission method. An optical communication system including a transmitter, a receiver, and a fiber connecting the transmitter and the receiver,
The transmitter transmits a laser light source and light from the laser light source to the optical frequency shift keying modulator according to any one of claims 1 to 4 and the optical frequency shift keying modulator. A signal source for outputting a power signal, and a high-frequency electrical signal source for providing a high-frequency electrical signal to the optical frequency shift keying modulator,
The receiver is a duplexer that demultiplexes the optical signal transmitted from the transmitter according to its wavelength;
A first photodetector for detecting one optical signal demultiplexed by the demultiplexer;
A second photodetector for detecting the remaining optical signal demultiplexed by the demultiplexer;
A subtractor that calculates a difference between an output signal of the first photodetector and an output signal of the second photodetector;
Optical FSK communication system. The optical FSK communication system according to claim 8, wherein the signal source can be switched by setting a plurality of voltage levels. An optical communication system including a transmitter, a receiver, and a fiber connecting the transmitter and the receiver,
The transmitter includes a laser light source, a light intensity modulator that modulates the intensity of light from the laser light source, and light from the laser light source that has been modulated by the light intensity modulator. 5. The optical frequency shift keying modulator according to claim 4, an intensity modulation signal source for outputting a signal to be transmitted to the optical intensity modulator, and a signal to be transmitted to the optical frequency shift keying modulator. And a high frequency electrical signal source for providing a high frequency electrical signal to the optical frequency shift keying modulator,
The receiver includes an intensity measurement photodetector for measuring the intensity of the optical signal transmitted from the transmitter;
A demultiplexer for demultiplexing the optical signal transmitted from the transmitter according to its wavelength;
A first photodetector for detecting one optical signal demultiplexed by the demultiplexer;
A second photodetector for detecting the remaining optical signal demultiplexed by the demultiplexer;
A subtractor that calculates a difference between an output signal of the first photodetector and an output signal of the second photodetector;
Optical FSK and optical intensity modulation communication system. An optical communication system including a transmitter, a receiver, and a fiber connecting the transmitter and the receiver,
5. The optical frequency shift keying modulator according to claim 1, wherein the transmitter receives a laser light source and light from the laser light source, and the optical frequency shift keying modulator has a frequency thereof. A light intensity modulator that modulates the intensity of light from a laser light source that has modulated light, an intensity modulation signal source for outputting a signal to be transmitted to the light intensity modulator, and a light frequency shift keying modulator A signal source for outputting a power signal, and a high-frequency electrical signal source for providing a high-frequency electrical signal to the optical frequency shift keying modulator,
The receiver includes an intensity measurement photodetector for measuring the intensity of the optical signal transmitted from the transmitter;
A demultiplexer for demultiplexing the optical signal transmitted from the transmitter according to its wavelength;
A first photodetector for detecting one optical signal demultiplexed by the demultiplexer;
A second photodetector for detecting the remaining optical signal demultiplexed by the demultiplexer;
A subtractor that calculates a difference between an output signal of the first photodetector and an output signal of the second photodetector;
Optical FSK and optical intensity modulation communication system. An optical frequency shift keying modulator according to any one of claims 1 to 4 ,
An optical signal whose optical frequency is switched by the optical frequency shift keying modulator is inputted, and responds to a frequency component more than twice the RF signal frequency inputted to the RF _A electrode and the RF _B electrode of the optical frequency shift keying modulator. A photodetector that can ,
Comprising
A signal corresponding to the difference frequency between the upper sideband and the lower sideband generated when the optical frequency of the optical signal is switched by the optical frequency shift keying modulator is obtained.
Millimeter wave / microwave pulse generator .   RF _C The millimeter wave / microwave pulse generator according to claim 12, wherein a rectangular pulse is used as an RF signal input to the electrode. An optical frequency shift keying modulator according to any one of claims 1 to 4 and an optical signal whose optical frequency is switched by the optical frequency shift keying modulator are input, and an RF of the optical frequency shift keying modulator is input. Using a photodetector that can respond to frequency components more than twice the frequency of the RF signal input to the _A and RF _B electrodes,
An optical signal whose optical frequency is switched by the optical frequency shift keying modulator is input to the photodetector, and an upper side band and a lower side wave generated when the optical frequency of the optical signal is switched by the optical frequency shift keying modulator. Obtain a signal corresponding to the difference frequency of the band
Millimeter wave / microwave pulse generation method. An optical frequency shift keying modulator according to any one of claims 1 to 4 ,
An optical signal whose optical frequency is switched by the optical frequency shift keying modulator is inputted, and responds to a frequency component more than twice the RF signal frequency inputted to the RF _A electrode and the RF _B electrode of the optical frequency shift keying modulator. A photodetector that can ,
Comprising
A UWB wireless communication system using a UWB signal obtained by obtaining a UWB signal corresponding to a difference frequency between an upper sideband and a lower sideband generated when the optical frequency of an optical signal is switched by the optical frequency shift keying modulator .

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