CN2652047Y - Multicircuit amplitude and frequency modulated acousto-optic modulation fibre-optical transmission apparatus - Google Patents
Multicircuit amplitude and frequency modulated acousto-optic modulation fibre-optical transmission apparatus Download PDFInfo
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- CN2652047Y CN2652047Y CNU032560230U CN03256023U CN2652047Y CN 2652047 Y CN2652047 Y CN 2652047Y CN U032560230 U CNU032560230 U CN U032560230U CN 03256023 U CN03256023 U CN 03256023U CN 2652047 Y CN2652047 Y CN 2652047Y
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- acousto
- optic modulator
- frequency
- input circuit
- preamplifier
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Abstract
The utility model relates to a multi-path acousto-optic amplitude and frequency modulation fiber transmission device, which belongs to the optical communication field, and is characterized in that: the transmission device is composed of a laser, an acousto-optic modulator, an acousto-optic modulator drive source, an amplitude and frequency modulation (AM/FM) signal source, a diaphragm, an optical collector, a demodulator and an optical information processing unit. Lights modulated by the acousto-optic modulator, the diaphragm and the optical collector are transmitted to the demodulator through fiber. The acousto-optic modulator is composed of a channel input circuit, a frequency modulation signal input circuit and a broadband coupling and power amplifying circuit. The channel input circuit wherein is composed of at least one crystal oscillator for local oscillation, a double balanced frequency mixing modulator and a preamplifier. The frequency modulation signal input circuit is composed of a voltage controlled oscillator and a preamplifier. Based on the technical scheme, the utility model has the advantages of broadband, multi-path, low noise, strong anti-jamming, multifunction, multiple signal channel and synchronous transmission of sound, image and word signals.
Description
Technical field
The utility model relates to a kind of multichannel amplitude modulation, frequency-modulated sound light modulation optical fiber transmitting device, belongs to optical communication field.
Background technology
The modulation of light wave is by changing its certain specific character, and for example realize amplitude, position phase, frequency, polarization or the direction of propagation, and the difficult point of laser communication is modulation technique, and main points will have enough modulation bandwidths.Light modulation can wherein have interference effect by several technology implementations, electro optic effect, magneto optical effect and acoustooptical effect.Most of light modulations are relevant with the change of refractive that produces by the control modulation signal.Variations in refractive index can be caused by following column effect:
1) electro optic effect;
2) magneto optical effect;
3) acoustooptical effect;
4) the semiconductor carriers change in concentration or
5) above effect is synthetic.
The shortcoming of existing acoustooptic modulation transmitting device with acoustooptical effect is single channel transmission and transmission range is short, interference free performance is poor.
Summary of the invention
The purpose of this utility model is in order to overcome the shortcoming of prior art, provides that a kind of many expenditures, broadband, noise are low, the multichannel amplitude modulation of strong anti-interference performance, frequency-modulated sound light modulation optical fiber transmitting device.
The modulation of laser beam is based on the Bragg diffraction principle in the acoustooptical effect in this patent.As everyone knows, when satisfying certain specified conditions, the transparent medium of a branch of light by a ultrasonic travelling wave, have partly energy by and this ultrasonic caused exponent of refractive index change and produce diffraction, with the most use in the diffraction effect that this class is produced by the ultrasonic travelling wave field is the Bragg diffraction.Fig. 1 is that the incident light direction is any, Δ K
m≠ 0, i.e. momentum mismatch, Fig. 2 be incident light along specific direction, Δ K
m=0, promptly momentum mates, when satisfying the Bragg diffraction conditions, and m=± 1.Shown in Fig. 1,2, by the interaction of analysis sound plane wave and optical plane ripple, because coherent effect, only diffraction light is the strongest when two bundle ripples satisfy certain fixed angle.These diffraction conditions are expressed as with the wave vector relation of two bundle ripples:
The circular frequency and the wave vector of incident light are respectively ω
0With k
0, the circular frequency of sound wave and wave vector are respectively Ω and k.Wave vector k
0Be respectively k with the mould of K
0=2 π n/ λ
0, K=2 π/∧=2 π f/v
λ
0Be optical wavelength, n is the refractive index of medium knot incident light, and ∧ and f are respectively ultrasonic wavelength and frequencies, and V is the velocity of sound.
Be defined as by equation (1) Bragg, diffraction
Sin θ B=K/2k=λ/2 ∧ (2) wherein θ B are Bragg angle (λ=λ
0/ n is the wavelength of light wave in medium).
Frequency relation between incident light and the diffraction light can be derived by parametric interaction is theoretical
ω
± 1=ω ± Ω (3) is ω wherein
+ 1=ω+Ω and ω
-1=ω-Ω corresponds respectively to positive 1 grade of negative 1 order diffraction light frequency.The zero level light frequency is identical with the incident light frequency, and frequency change and Doppler frequency shift are mutually roughly the same.When incident light satisfies the geometrical condition of Bragg diffraction just, in acousto-optic modulator, produced the light modulation that realizes by sound wave.Sound wave can be done amplitude modulation(PAM) and position modulation mutually to incident light, produces deflection, produces frequency shift (FS), and these characteristics are respectively applied for intensity modulated, beam deflection, filter, light signal processing, acousto-optic frequency modulator or the like.
The technical solution of the utility model is based on above-mentioned principle realization, be characterized in that it comprises laser, acousto-optic modulator, acousto-optic modulator drive source, amplitude modulation, amplitude modulation (AM/FM) signal source, Guang Lan, condenser, demodulator and optical information processing part, pass through the Optical Fiber Transmission demodulator through the light modulated of acousto-optic modulator, Guang Lan, condenser; The acousto-optic modulator drive source is connected with broadband coupling power amplifier by at least 1 FM signal input circuit of forming by the channel input circuit of forming as crystal oscillator, preamplifier, two balanced mixing modulator of local oscillator, by voltage controlled oscillator, preamplifier and forms.Demodulator and optical information processing part are made up of optical detection rectified signal processing unit, preamplifier, power amplifier, display, printer and loudspeaker.
According to such scheme, the utility model has the advantages that broadband, multichannel, low noise, strong interference immunity, serve many purposes, many signalling channels are transmitted signals such as sound, image, literal simultaneously.
Description of drawings
When Fig. 1 is any for the incident light direction, the interactional wave vector figure of Bragg diffraction light wave and sound wave;
Fig. 2 is an incident light during along specific direction, the interactional wave vector figure of Bragg diffraction light wave and sound wave;
Fig. 3 is the zero order beam under the Bragg diffraction and positive 1 grade of light beam and frequency change figure thereof;
Fig. 4 is the zero order beam under the Bragg diffraction and negative 1 grade of light beam and frequency change figure thereof;
Fig. 5 is a connection diagram of the present utility model;
Fig. 6 is an acousto-optic modulator drive source circuit schematic diagram;
Fig. 7 is the detection principle figure of light signal;
Fig. 8 receives amplification circuit diagram for optical fiber photoelectricity;
Fig. 9 is the many signal utilizations of an acousto-optic modulator multifrequency schematic diagram.
Embodiment
The utility model embodiment is done an explanation in conjunction with the accompanying drawings.By shown in Figure 5, multichannel amplitude modulation, frequency-modulated sound light modulation optical fiber transmitting device comprise laser 1, acousto-optic modulator 2, acousto-optic modulator drive source 3, amplitude modulation, amplitude modulation (AM/FM) signal source 4, diaphragm 5, condenser 6, demodulator and optical information processing part, transfer to demodulator through the light modulated of acousto-optic modulator 2, diaphragm 5, condenser 6 by optical fiber 7; Acousto-optic modulator drive source 3 is mainly to be connected and to be formed by the multichannel input circuit of forming as crystal oscillator 12, preamplifier 13, two balanced mixing modulator 15 of local oscillator, FM signal input circuit and the broadband mainly be made up of voltage controlled oscillator 18, preamplifier 19 power amplifier 21 that is coupled by at least 1.Demodulator and optical information processing part are made up of optical detection rectified signal processing unit 8, preamplifier 9, power amplifier 10, display, printer and loudspeaker 11.
By shown in Figure 6, above-mentioned acousto-optic modulator drive source 3 is made up of the multichannel input circuit of forming as crystal oscillator, preamplifier, two balanced mixing modulator of local oscillator one or more, and local oscillator can adopt f
0-f
nThe crystal oscillator 12 of multiple frequency, the preamplifier 13 of the crystal oscillator 12 of each frequency by separately, coupling transformer 14 are connected with separately two balanced mixing modulators 15, the two balanced mixing modulators 15 outputs power amplifier 21 that is coupled through amplifier 16, coupling transformer 17 and FM signal input circuit while of being made up of voltage controlled oscillator 18, preamplifier 19, coupling transformer 20 and broadband is connected, and its output is connected with acousto-optic modulator 2.
By shown in Figure 6, when amplitude modulation, frequency modulation (AM/FM) signal source 4 are output as certain amplitude (during amplitude-modulated signal between 0～1V), when being input to double balanced mixer 15 in the acoustooptic modulation drive source 4 by signal source 4, produced the intensity-modulated signal that on carrier wave that is frequency of ultrasonic, superposes, when useful signal is when using pulse code, a kind of variation of intensity modulated is pulse modulation.Signal through acoustooptic modulation drive source 3 is delivered on the PZT (piezoelectric transducer) of acousto-optic modulator 2, produced an intensity with the synchronous ultrasonic wave that changes of the useful signal of signal source 4, in the real-time acousto-optic interaction medium that is sent to acousto-optic modulator, produced the ultrasonic grating field during is advanced.By Fig. 3, shown in Figure 4, after beam of laser enters the clear aperture of acousto-optic modulator with the incident condition that satisfies the Bragg diffraction, do the district mutually by the ultrasonic grating diffraction at acousto-optic, the light beam of outgoing has been divided into several bundles, what wherein do not change direction along original optical path is zero order light, and the strongest a branch of in addition diffraction light is positive 1 grade or negative 1 grade, decides on the incident angle of the relative sound wave direct of travel of laser, its intensity can be adjusted to equal and opposite in direction, as long as be to transfer to the incident of Bragg angle equally.By Fig. 3, shown in Figure 4, at the positive and negative 1 grade of light intensity I of exit end
+ 1Or I
-1With zero order light light intensity I
00Sum total be equal to the incident intensity I of laser basically
0, i.e. I
0≌ I
+ 1+ I
00Or I
0=I
-1+ I
00Adjust the position of diaphragm 5, optional one is as the carrier of useful signal among zero order light and positive and negative 1 grade of light.For obtaining maximum available light signal, optical fiber 7 is gone into end and has been placed the laser that a focus lamp 6 collections are come out through the modulator diffraction, one of the key technical indexes of silica fiber 7 is a numerical aperture, characterize the characteristic of optical fiber and light source, detector and the coupling of other optical component, be defined as NA=Sin θ max, generally between 0.1～0.6, corresponding θ max is at 9 °～33 ° for the numerical aperture of optical fiber, and the multimode fiber numerical aperture is bigger.
For as much as possible being coupled in the optical fiber of laser diffraction light beam being gone, five times regualting frame of device configuration, has (1) transverse horizontal displacement Y, (2) vertical height lifting Z, (3) mounting platform is made rotation θ along central shaft at X-Y plane, and its directions X is that light going direction (4) optical fiber lens is installed the two-dimentional fine adjustment mechanism that is clipped in vertical YZ plane.That laser is used in this device is H
e-N
eLaser, laser tube are installed in can adjust height, on the support of light beam exit direction.The acousto-optic modulator mounting platform has degree of heightening and mounting plane is done the angle rotation along central shaft at X-Y plane, and diaphragm has lifting and laterally mobile function in vertical plane Y-Z.And the exit end of optical fiber is fastening and the photosensitive window of photodetector made normal incidence by a special fixture, has guaranteed making full use of of luminous energy.
By shown in Figure 7, be the detection and the demodulation of light signal.By shown in Figure 8, optical fiber photoelectricity receives amplifying circuit by photodiode D
5, resistance R
19, R
20And variable resistor R
21The input circuit of forming is formed by connecting through preamplifier 22, power amplifier 23.When the laser of being modulated by ultrasonic diffraction arrives receiving terminal through Optical Fiber Transmission, utilize Pin photodiode D
5Advantages such as response is fast, and spectral region is big, and noise is little have been made a photoelectricity receiving demodulation device, by changing the load resistance R of optical diode
21Change the frequency compensation of preamplifier 22, obtained the useful signal of low noise high-fidelity.When amplitude modulation, when frequency modulation (AM/FM) signal source 4 is output as an audio signal, observe through loudspeaker output and oscilloscope at power amplifier 23 outputs, the reproducibility fidelity of signal is all fine, and because broadband character (a few MHZ-tens MH that acousto-optic modulator itself is possessed
Z) and big linear dynamic range, fully guaranteed the linearity and the bandwidth of amplitude-modulated wave (AM).H as high-fidelity
IFi sound equipment (optical fiber) transmission system has an enormous advantage in all many-sides of the big bandwidth of anti-interference low noise.
Utilize the broadband character of acousto-optic modulator, can realize the transmission of a plurality of channels on a device, method is multifrequency operation in the effective bandwidth scope of this acousto-optic modulator, as shown in Figure 9, can realize N=Δ F in principle
M/ Δ F
SThe Optical Fiber Transmission of individual channel, Δ F
MBe the effective bandwidth of acousto-optic modulator, tens MH are arranged usually
Z, and Δ F
SBe the bandwidth of useful signal, when needing only multi-frequency excitation, 1 order diffraction luminous point of each channel can be separated with diaphragm on suitable distance, just can make abundant signalling channel, transmits signals such as sound, image, literal simultaneously.
Claims (3)
1, a kind of multichannel amplitude modulation, frequency-modulated sound light modulation optical fiber transmitting device, it is characterized in that it comprises laser (1), acousto-optic modulator (2), acousto-optic modulator drive source (3), amplitude modulation, frequency modulation (AM/FM) signal source (4), diaphragm (5), condenser (6), demodulator and optical information processing part; Light modulated through acousto-optic modulator (2), diaphragm (5), condenser (6) is to connect via optical fiber (7) to transfer to demodulator.
2, multichannel amplitude modulation according to claim 1, frequency-modulated sound light modulation optical fiber transmitting device, it is characterized in that described acousto-optic modulator drive source (3) is main be connected and formed by the channel input circuit of forming as crystal oscillator (12), preamplifier (13), two balanced mixing modulator (15) of local oscillator, FM signal input circuit and the broadband mainly be made up of voltage controlled oscillator (18), preamplifier (19) power amplifier (21) that is coupled by being at least 1.
3, multichannel amplitude modulation according to claim 1, frequency-modulated sound light modulation optical fiber transmitting device, it is characterized in that described demodulator and optical information processing part are made up of optical detection detection signal of telecommunication processing unit (8), preamplifier (9), power amplifier (10), display, printer and loudspeaker (11).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU032560230U CN2652047Y (en) | 2003-07-28 | 2003-07-28 | Multicircuit amplitude and frequency modulated acousto-optic modulation fibre-optical transmission apparatus |
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|---|---|---|---|
| CNU032560230U CN2652047Y (en) | 2003-07-28 | 2003-07-28 | Multicircuit amplitude and frequency modulated acousto-optic modulation fibre-optical transmission apparatus |
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| CN2652047Y true CN2652047Y (en) | 2004-10-27 |
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ID=34328707
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| CNU032560230U Expired - Fee Related CN2652047Y (en) | 2003-07-28 | 2003-07-28 | Multicircuit amplitude and frequency modulated acousto-optic modulation fibre-optical transmission apparatus |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102215079A (en) * | 2011-06-03 | 2011-10-12 | 武汉邮电科学研究院 | Frequency shift elimination method based on multi-wavelength relevant optical communication system |
| CN106850066A (en) * | 2017-01-24 | 2017-06-13 | 西安电子科技大学 | The device and method of Doppler shift measurement is realized based on dual-polarization modulator |
| CN109217929A (en) * | 2018-10-29 | 2019-01-15 | 黄河科技学院 | A kind of super high speed all-optical communication system |
-
2003
- 2003-07-28 CN CNU032560230U patent/CN2652047Y/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102215079A (en) * | 2011-06-03 | 2011-10-12 | 武汉邮电科学研究院 | Frequency shift elimination method based on multi-wavelength relevant optical communication system |
| CN106850066A (en) * | 2017-01-24 | 2017-06-13 | 西安电子科技大学 | The device and method of Doppler shift measurement is realized based on dual-polarization modulator |
| CN106850066B (en) * | 2017-01-24 | 2019-05-07 | 西安电子科技大学 | The method for realizing Doppler shift measurement based on dual-polarization modulator |
| CN109217929A (en) * | 2018-10-29 | 2019-01-15 | 黄河科技学院 | A kind of super high speed all-optical communication system |
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| GR01 | Patent grant | ||
| C19 | Lapse of patent right due to non-payment of the annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |