CN104601245B - Optical link capable of generating and transmitting radio frequency track angular momentum - Google Patents

Abstract

The invention discloses an optical link capable of generating and transmitting radio frequency track angular momentum. The diameter of existing radio frequency track angular momentum wave beams can obviously increase along with increase of transmission distance to result in receiving difficulty of a receiving end. The optical link capable of generating and transmitting radio frequency track angular momentum comprises an optical carrier radio frequency link and a free space optical link, wherein the optical carrier radio frequency link comprises a laser device, an optical amplifier and a photoelectric detector; radio frequency signals are modulated onto a beam emitted by the laser device through the an electro-optical modulator, and the beam enters the input end of the free space optical link; the beam output from the output end of the free space optical link is amplified through the optical amplifier and then enters the photoelectric detector to achieve recovery of the radio frequency signals. The optical link capable of generating and transmitting radio frequency track angular momentum integrates the characteristics that radio frequency track angular momentum wave beams are less prone to being interfered and optical frequency track angular momentum wave beams are less prone to divergence, improves the transmission quality of the track angular momentum wave beams, reduces distortion of the wave beams and accordingly improves the transmission efficiency of the wave beams.

Description

A kind of optical link that can produce and transmit radio frequency orbital angular momentum

Technical field

The present invention relates to produce carrying orbital angular momentum wave beam field with transmission, more particularly, to one kind produces and transmits radio frequency The optical link of orbital angular momentum.

Background technology

With the increase of communication usage amount, frequency spectrum resource reduces increasingly, and the capacity improving communication system has become with speed For matter of utmost importance.The angular momentum of electromagnetic wave is divided into spin angular momentaum and orbital angular momentum, and spin angular momentaum corresponds to wave beam Polarized state, and orbital angular momentum is then also not used.Therefore, using orbital angular momentum be a kind of improve spectrum efficiency new Method.The electromagnetic wave carrying orbital angular momentum has spiral phase front, this phase place and attitude and track angular motion The mode number of amount is relevant.The different orbital angular momentum wave beam of mode number is completely orthogonal, so having reusability.Several when having The wave beam of individual difference orbital angular momentum mode number is combined on a wave beam by multiplexing, and wherein each orbital angular momentum carries solely Vertical data, then the capacity of communication system and spectrum efficiency just improve several times.In theory, the mode number of orbital angular momentum is can Infinitely-great to get.Therefore, improve capacity and the spectrum efficiency tool of communication system using the wave beam carrying orbital angular momentum There is good development prospect.

Research currently for orbital angular momentum concentrates on optical frequency and radio-frequency range respectively.Optical frequency orbital angular momentum wave beam Production method mainly have hologram, spiral phase plate etc., the production method of radio frequency orbital angular momentum wave beam mainly has spiral Phase-plate, excipient antenna, array antenna etc..Both orbital angular momentum wave beams have respective weak point.Due to light wave Wavelength is little, and the phase place of optical frequency orbital angular momentum wave beam is easily affected so that wave beam is distorted by scattering and atmospheric turbulance.Penetrate Frequency orbital angular momentum beam diameter significantly becomes big with the increase of propagation distance, receiving terminal can be caused to receive difficult.Both Situation is all unfavorable for the long-distance communications of orbital angular momentum wave beam.

Content of the invention

It is an object of the invention to provide a kind of carry radio-frequency technique, Free Space Optics using light, design optical link, from And produce and transmit the optical link carrying radio frequency orbital angular momentum wave beam.

The present invention solves the taken technical scheme of technical problem：

The present invention includes light and carries radio frequency link and Free Space Optics link, and described light carries radio frequency link and includes laser Device, electrooptic modulator, image intensifer, photodetector；Radiofrequency signal modulates, by electrooptic modulator, the light that laser instrument sends Shu Shang, this light beam freedom of entry space optical link input；Pass through from Free Space Optics link output light beam out Image intensifer is amplified into the recovery that radiofrequency signal realized by photodetector；Described Free Space Optics link includes first Collimater, the second collimater, the first beam splitter, the second beam splitter, the first speculum and the second speculum；First collimator conduct The input of Free Space Optics link, space light beam is transmitted on the first speculum by the first beam splitter, the sky of reflection Between light beam through the first beam splitter reflection to the second beam splitter, then be transmitted on the second speculum by the second beam splitter, The space light beam of two-mirror reflection passes through the second beam splitter reflection to the second collimater, and the second collimater is as free space The output end of optical link.

The first described speculum or the second speculum the locus of different orientations the reflected beams different so that with In one space light beam, the light path of different orientations is different, thus changing the phase place of radiofrequency signal.

The space light beam of the first described speculum reflection carries radio frequency orbital angular momentum signal.

The first described speculum and the second mirror structure are identical, shape complementarity；Second speculum is by different orientations Light path compensate, thus by the reduction of the phase place of the radiofrequency signal on light beam, recovering primary signal.

The first described speculum and the second speculum are all step structure in the circumferential, the height between each ladder Difference is much larger than optical wavelength, but with the wavelength of radiofrequency signal in the same order of magnitude, real by changing the difference in height between each ladder Now to radiofrequency signal with azimuthal phase shift.The difference in height of two adjacent hierarchic structures is D, then adjacent steps structure reflected light Bundle delay inequality Δ τ be：

Wherein c is the light velocity in vacuum, the difference of the radiofrequency signal phase place causingFor：

Wherein f_RFFrequency for radiofrequency signal.Because the phase place of orbital angular momentum wave beam is with the periodically variable spy in azimuth Property, adjacent hierarchic structure meets to the change difference of radiofrequency signal phase place：

Wherein l is the mode of orbital angular momentum, and N is the number of the entirely upper hierarchic structure of circumference.

Beneficial effects of the present invention：Permissible through the optical link of light load radio frequency theory analysis, Free Space Optics design Produce the light beam carrying radio frequency orbital angular momentum, the big shortcoming of radio frequency orbital angular momentum wave beam diversity can be overcome, also can change The problem that kind optical frequency orbital angular momentum wave beam is easily interfered.Therefore, this link can improve the efficiency of orbital angular momentum communication, The distance of communication can be increased simultaneously.

Brief description

Fig. 1 produces and transmits the optical link of radio frequency orbital angular momentum；

The speculum schematic diagram of Fig. 2 particular design；

Fig. 3 is the phase place schematic diagram of radiofrequency signal in the light beam of space after reflection；

The side view of the speculum of Fig. 4 particular design；

Specific embodiment

Below in conjunction with the accompanying drawings the present invention is further described：

The general block diagram producing and transmitting the optical link of radio frequency orbital angular momentum is as shown in Figure 1.In figure laser instrument 1-1, Electrooptic modulator 1-2, image intensifer 1-3, photodetector 1-4 constitute light and carry radio frequency link I it is achieved that the tune of radiofrequency signal System and the demodulation to radiofrequency signal.Radiofrequency signal is modulated on the light beam that laser instrument sends by electrooptic modulator, receiving terminal By photodetector, radiofrequency signal is recovered.First collimator 2-1 in Fig. 1, the second collimater 2-2, the first beam splitter 2-3, Second beam splitter 2-4, the first speculum 2-5 and the second speculum 2-6 constitutes Free Space Optics link II it is achieved that radio frequency The generation of orbital angular momentum and compensation.Light beam is equivalent to through Free Space Optics link and achieves a radio frequency orbital angular momentum Modulation and demodulation.Between the first speculum and the second speculum, the light beam of transmission is the light wave carrying radio frequency orbital angular momentum Bundle.Due in this link radio frequency orbital angular momentum carry space light beam upload defeated, so overcoming radio frequency track angle The larger shortcoming in momentum beam direction angle.Simultaneously because it is radio frequency orbital angular momentum that space light beam uploads defeated, corresponding week To phase place change for radio frequency phase place change.So small disturbance is negligible for radio frequency wavelength, also change It has been apt to the shortcoming that optical frequency orbital angular momentum wave beam is easily interfered.

Fig. 2 is the structural representation of the first speculum 2-5 and the second speculum 2-6 of particular design.From collimater out Spatial light incide the center of speculum.Can see that the speculum of particular design circumferentially has step structure, each Difference in height between ladder is much larger than optical wavelength, but with the wavelength of radiofrequency signal in the same order of magnitude, by changing each ladder Between difference in height realize to radiofrequency signal with azimuthal phase shift.Fig. 3 is the phase of radiofrequency signal in the light beam of space after reflection Position schematic diagram.

Fig. 4 is the side view of particular design speculum.As figure, the difference in height of two adjacent hierarchic structures is D, then irradiate Delay inequality to top half light beam and the light beam of the latter half is

Wherein c is the light velocity in vacuum, and the difference of the radiofrequency signal phase place causing is

Wherein f_RFFrequency for radiofrequency signal.Because the phase place of orbital angular momentum wave beam is with the periodically variable spy in azimuth Property, adjacent hierarchic structure should meet to the change difference of radiofrequency signal phase place

Wherein l is the mode of orbital angular momentum, and N is the number of hierarchic structure in whole circumference.

According to principles above, the Free Space Optics link with particular design speculum is added light to carry radio frequency link In, the light beam between two pieces of particular design speculums will carry the radio frequency orbital angular momentum of phase vortex distribution, thus this Hybrid optical link just can be realized carrying generation and the transmission of the light beam of radio frequency orbital angular momentum simultaneously.

Claims (1)

1. a kind of optical link that can produce and transmit radio frequency orbital angular momentum it is characterised in that：Including light carry radio frequency link and Free Space Optics link, described light carries radio frequency link and includes laser instrument, electrooptic modulator, image intensifer, photodetector； Radiofrequency signal is modulated on the light beam that laser instrument sends by electrooptic modulator, and this light beam freedom of entry space optical link inputs End；It is amplified into photodetector from Free Space Optics link output light beam out through image intensifer and realize radio frequency Signaling protein14-3-3；Described Free Space Optics link include first collimator, the second collimater, the first beam splitter, second point Bundle device, the first speculum and the second speculum；First collimator is as the input of Free Space Optics link, space light beam It is transmitted on the first speculum by the first beam splitter, the space light beam of reflection is through the first beam splitter reflection to the second beam splitting Device, then be transmitted on the second speculum by the second beam splitter, the space light beam of the second speculum reflection passes through the second beam splitting Device reflexes to the second collimater, and the second collimater is as the output end of Free Space Optics link；

The first described speculum or the second speculum the locus of different orientations the reflected beams different so that same sky Between in light beam different orientations light path different, thus changing the phase place of radiofrequency signal；

The space light beam of the first described speculum reflection carries radio frequency orbital angular momentum signal；

The first described speculum and the second mirror structure are identical, shape complementarity；Second speculum is by the light of different orientations Journey compensates, thus by the phase place reduction of the radiofrequency signal on light beam, recovering primary signal；

The first described speculum and the second speculum are all step structure in the circumferential, and the difference in height between each ladder is remote More than optical wavelength, but with the wavelength of radiofrequency signal in the same order of magnitude, by change the difference in height between each ladder realize right Radiofrequency signal is with azimuthal phase shift；The difference in height of two adjacent hierarchic structures is D, then adjacent steps structure the reflected beams Delay inequality Δ τ is：

$\mathrm{\Δ}\mathrm{\τ}=-\frac{2D}{c}$

Wherein c is the light velocity in vacuum, the difference of the radiofrequency signal phase place causingFor：

Wherein f_RFFrequency for radiofrequency signal；Because the phase place of orbital angular momentum wave beam is with the periodically variable characteristic in azimuth, Adjacent hierarchic structure meets to the change difference of radiofrequency signal phase place：

Wherein l is the mode of orbital angular momentum, and N is the number of the entirely upper hierarchic structure of circumference.