JP2003258732A - Laser light source, power feeding apparatus using the same, wireless carrier discharge system, and portable telephone base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser light source available for a power feeding apparatus in which a configuration is simple and an energy loss is suppressed. <P>SOLUTION: In a laser light source 110 for generating a beat to be used as a carrier by photoelectric conversion, a pair of laser beams with a frequency difference equal to the frequency of the beat are emitted. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light source used when a beat for use as a carrier wave is generated by photoelectric conversion, a power supply device using the same, and
The present invention relates to a wireless carrier emission system and a mobile phone base station.

[0002]

2. Description of the Related Art A mobile phone can communicate by transmitting and receiving radio waves (a wireless carrier wave on which an information signal is superimposed) with a mobile phone base station. Here, in both cases of transmission of radio waves from the mobile phone to the mobile phone base station and transmission of radio waves from the mobile phone base station to the mobile phone, it is necessary to supply power to the transmission side to generate a wireless carrier wave (carrier). Becomes

The power supply at the mobile phone base station is carried out by sending high frequency power generated by a wireless device to an antenna through a coaxial cable. According to such power feeding, high-frequency power is sent using a coaxial cable, so that there is an advantage that the configuration of the antenna part can be simplified.

[0004]

By the way, in the future, when the radio wave used in the mobile phone becomes a microwave having a high frequency, the above-mentioned power feeding method has a problem that the loss due to the coaxial cable is large. Therefore, a power feeding method that does not use a coaxial cable is required.

As a power feeding method without using such a coaxial cable, high-frequency power is once converted into an optical signal by an E / O converter, and the optical signal is transmitted to a position right below the antenna via an optical fiber, and then again by the O / E converter. It has been proposed to convert it into an electric signal and supply it to an antenna.

However, in this method, since an electric signal is converted into an optical signal and the optical signal is converted into an electric signal again, a complicated system cannot be avoided.
There is also a problem that power efficiency is low, that is, energy loss is large.

The present invention has been made in view of the above points, and an object thereof is to use a laser light source which can be used in a power supply device having a simple structure and low energy loss, and a laser light source using the same. Power supply device, and
An object is to provide a wireless carrier emission system and a mobile phone base station.

[0008]

The laser light source of the present invention comprises:
It is used when generating a beat for use as a carrier wave by photoelectric conversion, and is characterized by emitting a pair of laser beams having a frequency difference equal to the frequency of the beat.

According to the above structure, the beat generated by photoelectrically converting the pair of emitted laser beams can be used as an electric signal as a carrier, so that an electric signal for a carrier is generated and the electric signal is used as an optical signal. As compared with the case where the optical signal is converted into the electric signal again after being converted into, the configuration for generating the carrier wave can be simplified and the energy loss can be suppressed to be low.

Further, even when a high frequency radio wave such as a microwave is emitted, an electronic circuit for generating the high frequency is unnecessary.

Furthermore, since the electric signal can be generated in beats by photoelectric conversion of the laser light, it is not necessary to use a capacitor or the like, and the stability of the electric signal can be improved.

The laser light source of the present invention may be composed of a fiber laser having resonators at both fiber ends. As a configuration of the laser light source, it is conceivable to prepare two lasers that emit laser lights having different frequencies and combine the laser lights from the lasers. Then, such a configuration is a heterodyne system in which the combined wave is input to the photoelectric conversion element and those beats are generated as electric signals which are carrier waves. However, according to the above configuration, since the laser light source is a fiber laser, the configuration of the laser light source can be a homodyne type and simple.

Here, as a specific configuration of the fiber laser which is the laser light source of the present invention, in the fiber laser, the resonator spacing is set so that the frequency difference between the pair of laser beams is equal to the beat frequency. You can list the things that have been done.

The fiber laser, which is the laser light source of the present invention, may be one in which the resonator spacing is set so that the pair of laser beams becomes a primary standing wave and a secondary standing wave. According to this configuration, the primary standing wave is a laser beam having a cavity spacing of 1/2 wavelength and the secondary standing wave is a laser beam having a cavity spacing of a wavelength. It can be the smallest and compact.

The fiber laser which is the laser light source of the present invention has a frequency selectivity in which at least one of the resonators at both fiber ends selectively reflects only a plurality of laser beams of equal frequency intervals including the pair of laser beams. May be included. According to this structure, the resonator can oscillate only a plurality of laser lights having a frequency interval equal to the frequency of the beat including the pair of laser lights. Specifically, for example, an etalon can be used as the resonator.

In this case, assuming that one fiber end is a total reflection end and the other fiber end is an emission end, only the resonator on the side of the total reflection end selectively reflects only a plurality of laser beams. It is preferable to have frequency selectivity. When a resonator having frequency selectivity is provided on the emitting end side, the configuration becomes complicated, and when an etalon is used as the resonator on the emitting end side, the output of laser light becomes small due to its insertion loss. The laser light source of the present invention may be equipped with a filter means for selectively emitting only the pair of laser lights. For example, when laser light other than the pair of laser lights having a frequency difference equal to the frequency of the carrier wave is emitted from the laser light source, beats of arbitrary combinations are generated. However, according to the above configuration, since only a specific pair of laser beams having a frequency difference equal to the frequency of the carrier wave is emitted from the laser light source, an extra noise component can be removed. Here, it is also possible to remove an unnecessary laser light component by the filter means at the time of output and thereby emit only the pair of laser lights, but this is not efficient. Therefore, it is preferable that only the pair of laser beams oscillate. For example,
In the case of a fiber laser, if a bandpass filter or a dielectric multi-layer film filter is provided between the resonators, or if a circulator is provided between the resonators and a fiber grating is connected to it to form a filter means, Only a pair of laser lights can be oscillated.

The laser light source of the present invention may be configured such that the pair of laser lights have the same polarization state. According to such a configuration, since the pair of laser lights have the same polarization state, it is possible to efficiently perform photoelectric conversion, and thereby to further reduce energy loss.

When the laser light source of the present invention is composed of a fiber laser, at least one of the resonators at both fiber ends may have polarization selectivity. According to such a configuration, since the polarization state of the pair of laser lights is aligned by the resonator having polarization selectivity, photoelectric conversion can be efficiently performed, thereby lowering energy loss. Can be suppressed.
Moreover, since the polarized waves are aligned by the resonator,
It is not necessary to separately provide an independent polarization controller, and the configuration can be simplified.

The power supply device of the present invention is used for power supply for emitting a wireless carrier wave, and includes a laser light source for emitting a pair of laser beams having a frequency difference equal to the frequency of the wireless carrier wave, and the laser light source. And a photoelectric conversion element for photoelectrically converting the pair of laser lights into an electric signal that is a beat having a frequency equal to the frequency difference between the pair of laser lights.

With the above arrangement, the same action and effect as those of the laser light source of the present invention can be obtained.

In the power supply device of the present invention, the photoelectric conversion element may be an element such as a photodiode or an element that generates an electromagnetic wave by photoelectric conversion. Specifically, such an element may be, for example, a high electron mobility transistor (HEMT).

The power supply device of the present invention may further comprise polarization adjusting means for adjusting the polarization states of the pair of laser beams from the laser light source which are input to the photoelectric conversion element. Some photoelectric conversion elements, such as photodiodes, have photoelectric conversion performance that depends on the polarization state of laser light. Therefore, according to the above configuration, if the pair of laser beams are adjusted by the polarization adjusting means so that the polarization state that the photoelectric conversion element is good at is obtained, photoelectric conversion by the photoelectric conversion element is effectively performed. Can be made. Specifically, as the polarization adjusting means, for example, 1/2
A wave plate, a retardation plate of a quarter wave plate, or a plate using birefringence by bending an optical fiber can be mentioned.

The power supply device of the present invention may further include light attenuating means for variably attenuating the intensity of a pair of laser beams from the laser light source input to the photoelectric conversion element. When the output of the laser light from the laser light source is excessively large, if it is directly input to the photoelectric conversion element, the characteristics of the photoelectric conversion element may be saturated and the characteristics may be distorted or the photoelectric conversion element may be destroyed. is there. However, according to the above configuration, when the output of the laser light from the laser light source is excessively large, the intensity of the laser light input to the photoelectric conversion element can be attenuated by the light attenuating unit, so that the intensity is high. It is possible to avoid a situation in which the laser light is input and the characteristics of the photoelectric conversion element are impaired or destroyed. Specifically, as the light attenuating unit, for example, a variable optical attenuator can be used.

The wireless carrier emission system of the present invention emits a wireless carrier wave, and emits a pair of laser beams having a frequency difference equal to the frequency of the wireless carrier wave, and a pair of laser light sources from the laser light source. A transmission optical fiber for transmitting laser light, a pair of laser light from the laser light source is input via the transmission optical fiber,
A photoelectric conversion element that photoelectrically converts the pair of laser lights into an electric signal that is a beat having a frequency equal to the frequency difference between them.
An antenna that emits an electric signal from the photoelectric conversion element as a wireless carrier wave is provided.

With the above arrangement, the same action and effect as those of the laser light source of the present invention can be obtained. In addition, the coaxial cables and waveguides that have been conventionally used to transmit high-frequency power to the antenna have extremely large losses,
In addition, since it is heavy and expensive to construct, it is not necessary to use those. Therefore, it is not necessary to transmit AC power up to the vicinity of the antenna, and at most DC power for supplying to the photoelectric conversion element or the optical amplifier is sufficient.

In the wireless carrier wave emission system according to the present invention, the pair of laser beams emitted from the laser light source have the same polarization state, and the transmission optical fiber has the pair of laser beams. May be configured to transmit while maintaining their polarization states. According to this configuration, since the pair of laser beams emitted from the laser light source and having the same polarization state are transmitted through the transmission optical fiber while maintaining the polarization state, photoelectric conversion is efficient. It is well run and can keep energy loss low.

The wireless carrier wave emission system of the present invention may further comprise a modulation means for superimposing an information signal on the pair of laser beams from the laser light source. According to such a configuration, the information signal is superimposed on the electric signal for power feeding and the intensity is modulated, whereby the radio wave carrying the information can be transmitted from the antenna.

In this case, in the wireless carrier emission system of the present invention, the laser light source has resonators at both fiber ends,
One of them may be a fiber laser having a total reflection end and the other an output end, and the modulating means may be a resonator on the output end side. With this configuration, since the resonator on the output end side serves as a modulator, it is not necessary to provide a separate modulator separately, and the configuration of the entire system can be simplified.

As a concrete carrier emission system, there may be mentioned a cellular phone base station and a short-range communication system using a wireless carrier wave having a short wavelength such as millimeter wave, microwave or infrared ray.

[0030]

As described above, according to the present invention, since a pair of laser beams are input to the photoelectric conversion element and the beat generated by photoelectric conversion is used as the electric signal of the carrier, the structure is simplified. It is possible to suppress the energy loss at the same time.

Further, even in the case of emitting high frequency radio waves such as microwaves, an electronic circuit for generating such high frequencies is not necessary.

Furthermore, since the electric signal of the carrier wave is generated in beats by photoelectric conversion of the laser light, the stability of the generated electric signal can be improved.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 shows the configuration of a mobile phone base station 100 according to the first embodiment of the present invention. The mobile phone base station 100 emits a high frequency radio carrier such as a microwave.

This mobile phone base station 100 comprises a fiber laser 110 constituting a laser light source and a fiber laser 1.
The output light from the isolator 120 is input, and the modulator (modulation means) 130 is provided so that the output light from the isolator 120 is input.
And a polarization adjusting element (polarization adjusting means) 140 provided so that the output light from the modulator 130 is input, and a variable adjusting element provided so that the output light from the polarization adjusting element 140 is input. An optical attenuator (optical attenuator) 150, a transmission optical fiber 160 provided so that the output light from the variable optical attenuator 150 is input, and an output light of the fiber laser 110 transmitted by the transmission optical fiber 160. And an optical amplifier 170 provided so that the output light from the optical amplifier 170 is input.
80, and an antenna 190 provided in the vicinity of the photoelectric conversion element 180 so that the electric signal output from the photoelectric conversion element 180 is directly input. That is, in the mobile phone base station 100, the fiber laser 110, the isolator 120, and the modulator 13
0, the polarization adjusting element 140 and the variable optical attenuating element 150 are installed indoors on the ground, while the antenna 190, the photoelectric conversion element 180 directly below the antenna 190, and the optical amplifier 170 are arranged at a high place such as a steel tower, and the antenna 190 To connect the optical amplifier 170, which is connected to the fiber laser 110 via the photoelectric conversion element 180, and the variable optical attenuation element 150, which is connected to the fiber laser 110 via the isolator 120, the modulator 130, and the polarization adjusting element 140. A transmission optical fiber 160 extends to the. Then, in the power feeding system of the mobile phone base station 100, a specific pair of laser lights having a frequency difference (longitudinal mode interval) equal to the frequency of the wireless carrier wave emitted from the antenna 190 is emitted from the fiber laser 110,
The information signals are superimposed by intensity-modulating the laser lights input by the modulator 130 via the isolator 120, and the information signals are passed through the polarization adjusting element 140, the variable optical attenuating element 150, and the transmission optical fiber 160. Is input to the optical amplifier 170, and a specific pair of laser beams amplified by the optical amplifier are photoelectrically converted by the photoelectric conversion element 180, and a carrier of an electric signal that is a beat is emitted from the antenna 190 as a wireless carrier. The wireless carrier wave is transmitted to a predetermined mobile phone. That is, the fiber laser 110 and the photoelectric conversion element 120 form a power feeding device.

The fiber laser 110 is provided with a rare earth element-doped fiber 111, a total reflection end side resonator 112 provided at one of the fiber ends, that is, a total reflection end side, and an emission end that is the other fiber end. Emitting end side resonator 11
3, a WDM coupler 114 provided on the total reflection end side of the rare earth element-doped fiber 111, and a WDM coupler 114.
A pumping LD (laser diode) 115 connected to
The filter element (filter means) 116 is provided on the emission end side of the rare earth element-doped fiber 111.

Further, the fiber laser 110 is capable of oscillating a plurality of laser beams including a specific pair of laser beams having a frequency difference (longitudinal mode interval) equal to the frequency of the radio carrier emitted from the antenna 190. belongs to. That is, the gap between the total reflection end side resonator 112 and the emission end side resonator 113 is set so that the frequency difference (longitudinal mode interval) of a specific pair of laser lights among the plurality of laser lights becomes equal to the frequency of the wireless carrier wave. That is, the resonator spacing is set. For example, when the frequency of the wireless carrier wave is 60 GHz, the resonator spacing is 60 GHz or 30 when the frequency difference (longitudinal mode spacing) between the specific pair of laser beams.
The frequency is set to be GHz, 10 GHz, 5 GHz, or the like, that is, a multiple of the frequency difference (longitudinal mode interval) is the frequency of the wireless carrier wave. At this time, the resonator spacing may be set so that a specific pair of laser lights becomes a primary standing wave and a secondary standing wave, and if so, the primary standing wave reduces the resonator spacing by half. Since the laser light having the wavelength and the secondary standing wave are the laser light having the resonator spacing as the wavelength, the fiber laser 110 as the laser light source can be made compact with the smallest resonator spacing.

The rare earth-doped fiber 111 is an optical fiber whose core is doped with a rare earth element. For example, an erbium-doped fiber (EDF) doped with erbium (Er) or a neodymium-doped fiber doped with neodymium (Nd) is used. It is composed of a ytterbium-doped fiber (YDF) doped with (NDF) or Yb (ytterbium).

The total-reflection end-side resonator 112 has a frequency selectivity that selectively reflects only a plurality of laser beams having a uniform frequency interval including a specific pair of laser beams, and is composed of, for example, an etalon. It The emitting end side resonator 113 is
The reflectance is 1 to 20%. Then, at least one of the total reflection end side resonator 112 and the emission end side resonator 113 has polarization selectivity, and the emission end side resonator 113 is provided.
The polarization states of a specific pair of laser beams output from the same are the same.

The pumping LD 115 is a pumping light source which emits pumping light having a wavelength corresponding to the rare earth element doped in the rare earth element doped fiber 111. For example, the rare earth element doped fiber 111 is an erbium doped fiber (E).
In the case of DF), it is composed of a semiconductor laser or the like that emits excitation light having a wavelength of 0.98 μm or a wavelength of 1.48 μm. Note that W
The DM coupler 114 is a branch element used to inject the pumping light from the pumping LD 115 into the rare earth element-doped fiber 111.

The filter element 116 transmits only light in a frequency range including the frequencies of a specific pair of laser lights, and is composed of, for example, a bandpass filter or a dielectric multilayer film filter.

Then, in this fiber laser 110,
Excitation light from the excitation LD 115 is input to the rare earth element-doped fiber 111, and the excitation light causes the outermost shell electrons of the rare earth element to be in an excited state to form a population inversion state, and the excited electrons transit to the ground state. Spontaneous emission light is emitted at the time. As shown in FIG. 2 (a), the spontaneous emission light that resonates (10 GHz in FIG. 2 (a)).
2) can be oscillated between the total reflection end side resonator 112 and the emission end side resonator 113, but since the total reflection end side resonator has frequency selectivity, As shown, a plurality of laser lights having a frequency interval equal to a frequency difference (a beat frequency, 60 GHz in FIG. 2B) of a specific pair of laser lights are selected from among them, and
The filter element 116 having the transmission characteristic as shown in FIG. 2C allows only a specific pair of laser beams to pass therethrough, as shown in FIG. 2D. As a result, only the specific pair of laser lights oscillates between the total reflection end side resonator 112 and the emission end side resonator 113, and amplification is repeated by stimulated emission, and a part of the laser light is emitted. 113
Is output via.

The isolator 120 is the fiber laser 1
It is an element that transmits the output light from 10 only in the direction of the antenna 190 side, and its isolation is 25 dB or more.

The modulator 130 is, for example, an electro-absorption modulator (EAM) and superimposes an information signal on a carrier wave. When the intensity modulation by the modulator 130 is not performed, as shown in FIG. 3A, when only the radio carrier having a constant amplitude is emitted from the antenna 190, the intensity modulation is performed by the modulator 130 and the information is transmitted. By superimposing the signals, as shown in FIG.
From 0, a radio carrier containing information is emitted by having a large and small amplitude.

The polarization adjusting element 140 is the photoelectric conversion element 18
The polarization state of a specific pair of laser beams is adjusted so that the photoelectric conversion performance of 0 becomes high, and is constituted by a retardation plate such as a ½ wavelength plate or a ¼ wavelength plate.

The variable optical attenuation element 150 attenuates the intensity of a specific pair of laser beams from the fiber laser 110 when the intensity of the photoelectric conversion element 180 is saturated and the characteristic is distorted. And is composed of, for example, a light variable attenuator.

The transmission optical fiber 160 is an optical fiber that transmits a specific pair of laser lights whose polarization states are aligned while maintaining their polarization states, and is composed of, for example, a polarization-maintaining fiber. .

The optical amplifier 170 amplifies a specific pair of laser beams and is composed of, for example, a rare earth element-doped fiber amplifier (EDFA). In the illustrated example, the optical amplifier 170 is arranged directly below the antenna 190, but an optical amplifier may be arranged on the fiber laser 110 side and only the photoelectric conversion element may be arranged directly below the antenna.

The photoelectric conversion element 180 is for converting a specific pair of laser beams into an electric signal, and for example, a photodiode or a high electron mobility transistor (High Electron Mobility T) that directly generates an electromagnetic wave by photoelectric conversion.
ransistor: HEMT). Further, the photoelectric conversion element 180 has a band sufficient to demodulate a specific pair of input laser beams into an electric signal having a frequency corresponding to the frequency difference (longitudinal mode interval) between them.

The antenna 190 emits a carrier wave, which is an electric signal from the photoelectric conversion element, as a wireless carrier wave, and is composed of, for example, a linear antenna.

According to the mobile phone base station 100 having the above-described configuration, in the power feeding device including the fiber laser 110 and the photoelectric conversion element 180, a specific pair of laser beams are input to the photoelectric conversion element 180 to perform photoelectric conversion. Since the beat generated by is the electric signal of the carrier wave, after generating the electric signal of the carrier wave and converting the electric signal into an optical signal,
Compared with a device that converts the optical signal into an electric signal again, the structure of the power feeding device can be simplified and energy loss can be suppressed low.

Further, a high-frequency carrier wave such as a microwave can be emitted without requiring an electronic circuit for generating a high frequency.

Furthermore, since the electric signal of the carrier wave is generated in beats by photoelectric conversion of the laser light, it is not necessary to use a capacitor or the like, and the stability of the electric signal can be improved.

Further, although coaxial cables and waveguides conventionally used for transmitting high-frequency power to an antenna have very large losses and are expensive, it is not necessary to use them. Therefore, it is not necessary to transmit AC power up to the vicinity of the antenna 190, and at most DC power for supply to the photoelectric conversion element 180 and the optical amplifier 170 is sufficient.

As a structure of the laser light source, it is conceivable to prepare two lasers which emit laser lights having different frequencies and combine the laser lights from the respective lasers. And, in such a structure, a heterodyne system in which the combined wave is input to the photoelectric conversion element and those beats are generated as an electric signal as a carrier wave is used. However, in the first embodiment, since the laser light source is configured by the fiber laser 110, the configuration of the laser light source is homodyne type and simple.

At least one of the total reflection end side resonator 112 and the emission end side resonator 113 has polarization selectivity so that a specific pair of laser lights have the same polarization state. Therefore, the polarization states of a specific pair of laser lights are aligned, and since the transmission optical fiber 160 is composed of a polarization maintaining fiber, the fiber laser 11
A specific pair of laser beams having the same polarization state emitted from 0 transmits the optical fiber 1 while maintaining the polarization state.
Since 60 is transmitted, photoelectric conversion can be efficiently performed, and energy loss can be reduced. Further, since the polarized waves are aligned by the resonator, it is not necessary to separately provide an independent polarization controller, and the entire configuration is simplified.

The photoelectric conversion performance of the photoelectric conversion element 180 may depend on the polarization state of the laser light like a photodiode. However, in the first embodiment, since the polarization adjusting element 140 is provided, it is possible to adjust the polarization state of the specific pair of laser lights so that the photoelectric conversion performance of the photoelectric conversion element 180 is improved. The photoelectric conversion element 180 can function with high performance.

When a laser beam other than the specific pair of laser beams having a frequency difference (longitudinal mode interval) equal to the frequency of the carrier wave is emitted from the fiber laser 110, an arbitrary combination of beats is generated. However, in the first embodiment, the total reflection end side resonator 112 having frequency selectivity selects only a plurality of laser lights at equal frequency intervals including a specific pair of laser lights, and further, the filter element 116. Since only a specific pair of laser lights are selected and only the specific pair of laser lights are emitted from the fiber laser 110, it is possible to remove an unnecessary noise component. Moreover, since the filter element 116 is provided between both the resonators of the fiber laser 110 and only the specific pair of laser beams oscillates, the efficiency is improved.

When the output of the specific pair of laser beams from the fiber laser 110 is excessive, if they are directly input to the photoelectric conversion element 180, the characteristics of the photoelectric conversion element 180 may be saturated and the characteristics may be distorted. , Photoelectric conversion element 1
There is a risk of destroying 80. However, according to the first embodiment, when the output of the specific pair of laser beams from the fiber laser 110 is excessive, the specific pair of lasers input to the photoelectric conversion element 180 by the variable optical attenuator 150. Since the intensity of light can be attenuated, strong laser light is input to the photoelectric conversion element 180.
It is possible to avoid the situation of damaging or destroying the characteristics of.

(Second Embodiment) FIG. 4 shows the configuration of a mobile phone base station 200 according to a second embodiment of the present invention. The mobile phone base station 200 emits a high frequency radio carrier such as a microwave.

This mobile phone base station 200 includes a fiber laser 210 that constitutes a laser light source and a fiber laser 2.
Isolator 220 provided so that the output light from 10 is input, Polarization adjustment element (polarization adjustment means) 240 provided so that the output light from isolator 220 is input, and polarization adjustment element Variable optical attenuator (optical attenuator) provided so that output light from 240 is input.
250, a transmission optical fiber 260 provided so that the output light from the variable optical attenuator 250 is input, and an output light of the fiber laser 210 transmitted by the transmission optical fiber 260 is input. Optical amplifier 270
And a photoelectric conversion element 280 provided so that the output from the optical amplifier 270 is input, and a position close to the photoelectric conversion element 280 so that the electric signal output from the photoelectric conversion element 280 is directly input. The provided antenna 290
And, it has a configuration provided with. That is, in the mobile phone base station 200, the fiber laser 210, the isolator 220, the polarization adjusting element 240, and the variable optical attenuating element 25.
0 is installed indoors on the ground, while antenna 290
And the photoelectric conversion element 280 and the optical amplifier 27 immediately below
0 is arranged at a high place such as a steel tower, and an optical amplifier 270 connected to an antenna 290 via a photoelectric conversion element 280, and a variable optical attenuation connected to a fiber laser 210 via an isolator 220 and a polarization adjusting element 240. Element 250
And a transmission optical fiber 260 extends so as to connect the two. Then, in the power feeding method of the mobile phone base station 200, a specific pair of laser lights having a frequency difference (longitudinal mode interval) equal to the frequency of the wireless carrier wave emitted from the antenna 290 is emitted from the fiber laser 210, and those laser lights are emitted. Laser light is an isolator 220 and a polarization adjusting element 24.
0, variable optical attenuator 250 and transmission optical fiber 260
Is sequentially input to the optical amplifier 270, and the optical amplifier 27
One specific laser beam amplified by 0 is photoelectric conversion element 2
A carrier wave which is an electric signal of a beat generated by photoelectric conversion at 80 is emitted from the antenna 290 as a wireless carrier wave, and the wireless carrier wave is transmitted to a predetermined mobile phone. That is, the fiber laser 210 and the photoelectric conversion element 220 form a power feeding device. In addition,
As will be described later, intensity modulation for superimposing the information signal is performed in the fiber laser 210, and the antenna 290
The information signal is included in the wireless carrier wave emitted from the device and transmitted to the mobile phone.

Further, in this portable telephone base station 200, the emitting end side resonator 213 is constructed so that the reflectance or the insertion loss thereof can be freely adjusted, and by operating it, the laser light to be output has information. It is designed to superimpose signals. That is, the modulator as an independent element is not provided, and the emitting end side resonator 213 also has the function of the modulator.

The other structure is the same as that of the first embodiment.

According to the portable telephone base station 200 having the above configuration, since the output end side resonator 213 also constitutes the modulator, it is not necessary to provide a separate modulator separately, and the overall configuration is simplified. Can be one.

Other functions and effects are the same as those in the first embodiment.

(Other Embodiments) In the above-described first and second embodiments, the mobile phone base stations 100 and 200 are described, but the present invention is not particularly limited to this.
It may be a carrier emission system such as a short-distance communication system that uses a wireless carrier having a short wavelength such as a millimeter wave, a microwave, or infrared.

In the first and second embodiments, the laser light sources are the fiber lasers 110 and 210. However, the laser light sources are not particularly limited to this, and two lasers that emit laser light having different frequencies are prepared. The laser light from the laser may be combined. Such a configuration is a heterodyne system in which the combined wave is input to a photoelectric conversion element and those beats are generated as an electric signal as a carrier wave.

In the first and second embodiments, the laser light is amplified by the rare earth element-doped fibers 111, 211, but the invention is not limited to this, and the laser light is amplified by Raman amplification. You may

In the first and second embodiments, the excitation L
The WDM coupler 114 to which the D115 and 215 are connected is provided on the total reflection end side of the rare earth element-doped fibers 111 and 211, but the present invention is not particularly limited to this, and even if it is on the emission end side, the total reflection end side is further reduced. Reflection end side resonator 112, 2
12 or may be provided outside the emitting end side resonators 113 and 213.

Further, in the first and second embodiments, the WDM
Excitation LDs 115 and 215 via couplers 114 and 214
The pumping light is injected from the pump LD. However, the pumping light is not particularly limited to this, and the rare earth element-doped fiber 1 is directly supplied from the pumping LD 115, 215 via the total reflection end side resonator.
Excitation light may be injected into 11 and 211.

In the first and second embodiments, the filter means is constituted by the filter elements 116 and 216 interposed between the resonators of the fiber lasers 110 and 210, but the present invention is not limited to this. As shown in FIG. 5, the circulator 317 provided in the rare earth element-doped fiber 311 between both resonators and the fiber grating 318 connected thereto may constitute the filter means. In this case, the fiber grating 31
Only the laser light reflected at 8 oscillates, and the filter function is fulfilled.

Further, in the above-described first and second embodiments, the polarization adjusting means is constituted by the polarization adjusting elements 140 and 240, but the invention is not particularly limited to this, and the birefringence caused by bending the optical fiber. May be used.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a mobile phone base station according to a first embodiment of the present invention.

FIG. 2A is a graph showing the relationship between the frequency and the intensity of laser light that can be oscillated by a fiber laser, and FIG. 2B is the frequency of the laser light after being selected by the total reflection end-side resonator. It is a graph showing the relationship with the intensity, (c) is a graph showing the relationship between the frequency and the transmittance of the filter element,
(D) is a graph showing the relationship between the frequency and the intensity of the laser light after being selected by the filter element.

FIG. 3A is an explanatory diagram showing a waveform of a wireless carrier wave on which an information signal is not superimposed, and FIG. 3B is an explanatory diagram showing a waveform of a wireless carrier wave on which an information signal is superimposed.

FIG. 4 is a configuration diagram showing a configuration of a mobile phone base station according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a filter means of a fiber laser according to another embodiment of the present invention.

[Explanation of symbols]

100,200 Cellular phone base station (wireless carrier emission system) 110,210 Fiber laser (laser light source) 111,211,311 Rare earth element doped fiber 112,212 Total reflection end side resonator 113,213 Emission end side resonator 114, 214 WDM coupler 115, 215 Excitation LD 116, 216 Filter element (filtering means) 120, 220 Isolator 130 Modulator (modulating means) 140, 240 Polarization adjusting element (polarization adjusting means) 150, 250 Variable optical attenuating element (optical) Attenuation element) 160,260 Transmission optical fiber 180,280 Photoelectric conversion element 190,290 Antenna 317 Circulator 318 Fiber grating

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04B 10/26 10/28 (72) Inventor Masaaki Morisawa 3-4-1, Marunouchi, Chiyoda-ku, Tokyo Shin-Kokusai Building Mitsubishi Cable Industries, Ltd. Tokyo Office (72) Inventor Yutaka Suganuma 3-4-1 Marunouchi, Chiyoda-ku, Tokyo Shin-Kokusai Building Mitsubishi Cable Industries Ltd. Tokyo Office (72) Inventor Masashi Takahashi Marunouchi, Chiyoda-ku, Tokyo 3-4-1 New International Building Mitsubishi Cable Industries, Ltd. Tokyo Office F-term (reference) 5F072 AB07 AB08 AB09 AK06 JJ20 KK30 MM03 PP07 SS02 YY20 5K002 BA02 BA05 BA13 BA21 CA13 CA14 EA04 FA01 FA02

Claims (18)

[Claims] 1. A laser light source used when a beat for use as a carrier wave is generated by photoelectric conversion, the laser light source emitting a pair of laser lights having a frequency difference equal to the frequency of the beat. light source. 2. The laser light source according to claim 1, comprising a fiber laser having resonators at both fiber ends. 3. The laser light source according to claim 2, wherein the fiber laser has a cavity interval set such that a frequency difference between the pair of laser beams is equal to a frequency of the beat. And laser light source. 4. The laser light source according to claim 3, wherein in the fiber laser, the resonator spacing is set so that the pair of laser lights become a primary standing wave and a secondary standing wave. Laser light source characterized by. 5. The laser light source according to claim 2, wherein in the fiber laser, at least one of the resonators at both fiber ends selects only a plurality of laser lights at equal frequency intervals including the pair of laser lights. A laser light source having a frequency selectivity of selectively reflecting light. 6. The laser light source according to claim 5, wherein in the fiber laser, one fiber end is a total reflection end and the other fiber end is an emission end, and a resonance on the total reflection end side among them. A laser light source characterized in that only the container has a frequency selectivity that selectively reflects only the plurality of laser lights. 7. The laser light source according to claim 1, further comprising a filter unit that selectively emits only the pair of laser beams. 8. The laser light source according to claim 1, wherein the pair of laser lights are configured to have the same polarization state. 9. The laser light source according to claim 2, wherein at least one of the resonators at both fiber ends has polarization selectivity. 10. A power supply device used for power supply for emitting a wireless carrier wave, comprising: a laser light source that emits a pair of laser lights having a frequency difference equal to the frequency of the wireless carrier wave; and a pair of laser light sources from the laser light source. A power supply device, comprising: a photoelectric conversion element that receives a laser beam and photoelectrically converts the pair of laser beams into an electric signal that is a beat having a frequency equal to a frequency difference between the pair of laser beams. 11. The power feeding device according to claim 10, wherein the photoelectric conversion element is an element that generates an electromagnetic wave by photoelectric conversion. 12. The power feeding device according to claim 10, further comprising polarization adjusting means for adjusting a polarization state of a pair of laser beams from the laser light source input to the photoelectric conversion element. Power supply device characterized by. 13. The power supply device according to claim 10, further comprising an optical attenuator that variably attenuates the intensity of a pair of laser beams from the laser light source that are input to the photoelectric conversion element. Characteristic power supply device. 14. A wireless carrier emission system for emitting a wireless carrier, comprising: a laser light source emitting a pair of laser lights having a frequency difference equal to the frequency of the wireless carrier; and transmitting a pair of laser lights from the laser light source. Optical fiber for transmission, and a pair of laser light from the laser light source is input through the optical fiber for transmission, and the pair of laser light is photoelectrically converted into an electric signal that is a beat having a frequency equal to the frequency difference between them. A wireless carrier wave emission system, comprising: a photoelectric conversion element that operates as described above; 15. The wireless carrier wave emission system according to claim 14, wherein the laser light source is configured such that the pair of laser lights emitted from the laser light source have the same polarization state, The wireless carrier emission system, wherein the transmission optical fiber is configured to transmit the pair of laser lights while maintaining their polarization states. 16. The wireless carrier wave emission system according to claim 14, further comprising a modulation means for superimposing an information signal on a pair of laser beams from the laser light source. system. 17. The radio carrier emission system according to claim 16, wherein the laser light source has a resonator at both fiber ends, one of which is a total reflection end and the other is an output end. A wireless carrier wave emission system comprising a laser, and the modulating means is composed of a resonator on the output end side. 18. A mobile phone base station that emits a wireless carrier wave, the laser light source emitting a pair of laser beams having a frequency difference equal to the frequency of the wireless carrier wave, and transmitting a pair of laser beams from the laser light source. Optical fiber for transmission, and a pair of laser light from the laser light source is input through the optical fiber for transmission, and the pair of laser light is photoelectrically converted into an electric signal that is a beat having a frequency equal to the frequency difference between them. A mobile phone base station, comprising: a photoelectric conversion element that operates as described above; and an antenna that emits an electric signal from the photoelectric conversion element as a wireless carrier wave.