Large-bandwidth optical fiber type acousto-optic modulator

Abstract

The utility model discloses a large-bandwidth optical fiber type acousto-optic modulator, which structurally comprises a bottom plate, a first acousto-optic modulator, a second acousto-optic modulator and a reflecting mirror, the first acousto-optic modulator, the second acousto-optic modulator and the reflecting mirror are all mounted on the bottom plate, the first acousto-optic modulator and the second acousto-optic modulator are arranged in a cascading manner, and the first acousto-optic modulator and the second acousto-optic modulator are mounted on the bottom plate. The sum of the radio frequency of the first acousto-optic modulator and the radio frequency of the second acousto-optic modulator is equal to the sum of the intermediate frequency of the first acousto-optic modulator and the intermediate frequency of the second acousto-optic modulator, and the reflector is located on an output light path of the second acousto-optic modulator. And the reflector totally reflects the frequency shift light output by the second acousto-optic modulator and returns to the second acousto-optic modulator through the original path. According to the scheme, the problem that in the prior art, the bandwidth of an optical fiber type acousto-optic modulator is limited by the optical fiber coupling angle is solved, and the ultra-large bandwidth optical fiber type acousto-optic modulator can be achieved through cascade connection of the two bandwidth type acousto-optic modulators.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of optoelectronic technology, specifically relates to a kind of large bandwidth optical fiber type acoustooptic modulator. BACKGROUND

[0002] Acoustooptic modulator (AOM) can shift frequency to laser, when extra-high frequency oscillation, laser passes through the acoustooptic medium and occurs a series of frequency shift, frequency shift light will produce the same frequency shift amount and corresponding direction change as added frequency, the bandwidth (generally take 3dB bandwidth) of acoustooptic modulator refers to the maximum frequency shift amount that can be realized before the output optical power drops by 50%.

[0003] The frequency shift characteristic of acoustooptic modulator is widely used in laser radar, frequency modulation continuous wave generation, distributed fiber sensing and other sensing fields, and the frequency and distance mapping is realized by modulating light frequency and intrinsic light beat frequency, the spatial resolution is inversely proportional to modulation bandwidth, and the larger the bandwidth of the device is, the more effectively the detection accuracy of the system can be improved, which is a key device for improving system performance.

[0004] At present, a single fiber acoustooptic modulator is used for frequency shift in optical fiber system, as shown in the accompanying drawings, laser input through fiber collimating head is recoupled into output optical fiber at intermediate frequency after passing through acoustooptic modulator. Figure 1 In addition to being affected by its own structure, the bandwidth is greatly limited due to the existence of a deflection angle between frequency shift light and incident light, and the angle size is proportional to frequency, when the frequency changes greatly, the direction of frequency shift light changes greatly and is difficult to be coupled into optical fiber, which greatly limits the bandwidth of fiber acoustooptic modulator, and the highest level that can be achieved is only 80MHz. UTILITARY MODEL CONTENT

[0005] In view of the above problems existing in the prior art, the technical problem to be solved by the utility model is how to provide a large bandwidth optical fiber type acoustooptic modulator which can greatly improve the bandwidth of fiber acoustooptic modulator and improve system performance.

[0006] In order to solve the above technical problems, the utility model adopts the following technical scheme:

[0007] The application discloses a large-bandwidth optical fiber type acousto-optic modulator, which comprises a base plate, a first acousto-optic modulator, a second acousto-optic modulator and a reflecting mirror, wherein the first acousto-optic modulator, the second acousto-optic modulator and the reflecting mirror are all mounted on the base plate, the first acousto-optic modulator and the second acousto-optic modulator are arranged in cascade, the sum of the radio frequency of the first acousto-optic modulator and the radio frequency of the second acousto-optic modulator is equal to the sum of the intermediate frequency of the first acousto-optic modulator and the intermediate frequency of the second acousto-optic modulator, and the reflecting mirror is located on the output light path of the second acousto-optic modulator and fully reflects the frequency-shifted light output by the second acousto-optic modulator and returns to the second acousto-optic modulator again.

[0008] The working principle of the application is that the incident light is sequentially frequency-shifted by the first acousto-optic modulator and the second acousto-optic modulator, the light of different frequencies after frequency-shifted by the first acousto-optic modulator and the second acousto-optic modulator is output in parallel, the frequency-shifted light output by the second acousto-optic modulator is fully reflected by the reflecting mirror and sequentially frequency-shifted by the second acousto-optic modulator and the first acousto-optic modulator again and then output.

[0009] Since the sum of the radio frequency of the first acousto-optic modulator and the radio frequency of the second acousto-optic modulator is equal to the sum of the intermediate frequency of the first acousto-optic modulator and the intermediate frequency of the second acousto-optic modulator, when the first acousto-optic modulator performs positive frequency shift, the second acousto-optic modulator performs negative frequency shift, and when the first acousto-optic modulator performs negative frequency shift, the second acousto-optic modulator performs positive frequency shift. The deflection angle of the first acousto-optic modulator to the light is θ 1 , the deflection angle of the second acousto-optic modulator to the light is θ 2 , and the total deflection angle of the incident light after passing through the first acousto-optic modulator and the second acousto-optic modulator is θ, θ = θ 1 + θ 2 .

[0010] When the frequency of the first acousto-optic modulator is increased df , the deflection angle of the first acousto-optic modulator to the light is θ 1 + dθ , the frequency-shifted amount of the first acousto-optic modulator to the light is f 1 + df At this time, the frequency of the second acousto-optic modulator is decreased df , the deflection angle of the second acousto-optic modulator to the light is θ 2 - dθ , and the frequency-shifted amount of the second acousto-optic modulator to the light is -（f 2 - df),The total deflection angle of the incident light after passing through the first and second acousto-optic modulators is still θ, θ = θ 1 + θ 2 ， The total frequency shift of the incident light after passing through the first and second acousto-optic modulators is f 1 -f 2 + 2df;

[0011] The frequency-shifted light output by the second acousto-optic modulator reaches the mirror, which returns all the light in the original path. The returned light passes through the second and first acousto-optic modulators in turn and is frequency-shifted again. The returned light output after the second frequency shift is coupled into the optical fiber, and the total frequency shift of the light coupled into the optical fiber is 2(f2-f1). f 1 -f 2 + 2df ). This scheme can be applied to two acousto-optic modulators with the same bandwidth and arbitrary center frequencies. The intermediate frequency of the output light is twice the sum of the intermediate frequencies of the two devices, and the bandwidth is twice the sum of the bandwidths of the two devices. This scheme can realize frequency shifting of any frequency and bandwidth within -1000 to +1000 MHz by using appropriate combinations of acousto-optic modulators. By changing the operating wavelength of each component, the wavelength range that this scheme can be applied to includes but is not limited to 200-2000 nm. Further, the input and output effects of a large-bandwidth optical fiber are realized.

[0012] Preferably, it further comprises a polarization beam splitting prism and a quarter-wave plate. The polarization beam splitting prism is located on the input light path of the first acousto-optic modulator, and the polarization beam splitting prism transmits the collimated light in the horizontal polarization state to the first acousto-optic modulator. The quarter-wave plate is located between the second acousto-optic modulator and the mirror, and the quarter-wave plate outputs the frequency-shifted light output by the second acousto-optic modulator after a 90° phase delay to form vertically polarized light. The mirror fully reflects the vertically polarized light output by the quarter-wave plate and then inputs it to the second acousto-optic modulator through the quarter-wave plate again.

[0013] Preferably, it further comprises an input fiber collimator and an output fiber collimator. The input fiber collimator shapes the input polarized light into collimated light and outputs it. The polarization beam splitting prism is located on the output light path of the input fiber collimator. The output fiber collimator is located on the reflected output light path of the polarization beam splitting prism, and the output fiber collimator shapes the vertically polarized light reflected by the polarization beam splitting prism and outputs it.

[0014] Preferably, the output fiber collimator outputs light with a frequency twice the sum of the frequencies of the first and second acousto-optic modulators, and a bandwidth twice the sum of the bandwidths of the first and second acousto-optic modulators.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] 1. The present application can realize large bandwidth laser frequency shift under the condition of fiber input and output. The two bandwidth acousto-optic modulators are placed in cascade, the center frequency and the bandwidth are variable, the control driving frequencies applied to the two acousto-optic modulators always satisfy a fixed relationship, so that the output light of different frequencies is parallel to each other. Since the angle of the output light of different frequencies is unchanged, the light is returned to the original path through a reflecting mirror and finally synthesized into a beam, so as to be coupled into the fiber, realizing the input and output of large bandwidth fiber. By using appropriate combination, the frequency shift of any frequency and any bandwidth can be realized.

[0017] 2. The present application solves the problem that the bandwidth of the fiber type acousto-optic modulator in the prior art is limited by the fiber coupling angle. By using two bandwidth acousto-optic modulators in cascade, a fiber type acousto-optic modulator with super large bandwidth can be realized.

[0018] 3. The present application can be applied to two acousto-optic modulators with the same bandwidth and arbitrary center frequency. The output light has a frequency twice the sum of the frequencies of the two devices, and a bandwidth twice the sum of the bandwidths of the two devices.

[0019] 4. By using appropriate acousto-optic modulator combination, the present application can realize frequency shift of any frequency and any bandwidth within -1000 to +1000 MHz. By changing the working wavelength of each component, the present application can be applied to a wavelength range including but not limited to 200-2000 nm. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Fig. 1 is a structural schematic view of a fiber type acousto-optic modulator in the prior art;

[0021] Figure 2 Fig. 2 is a structural schematic view of a large bandwidth fiber type acousto-optic modulator of the present application;

[0022] Figure 3 Fig. 3 is a light path principle view of the large bandwidth fiber type acousto-optic modulator of the present application;

[0023] Figure 4 Fig. 4 is a 400 MHz bandwidth efficiency test curve diagram realized by using the large bandwidth fiber type acousto-optic modulator of the present application.

[0024] Explanation of reference numerals: input optical fiber collimator 1, polarization beam splitter prism 2, first acousto-optic modulator 3, second acousto-optic modulator 4, quarter-wave plate 5, mirror 6, output optical fiber collimator 7, base plate 8. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application. Unless otherwise defined, the technical terms or scientific terms used herein should have the usual meanings understood by those of ordinary skill in the art to which the present application belongs.

[0026] The terms "first", "second", and similar terms used in the patent application specification and claims of the present application do not represent any order, number or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms "a", "an" or "the" and the like do not represent a quantity limitation, but represent the existence of at least one. The terms "include" or "contain" and the like mean that the elements or objects appearing before "include" or "contain" cover the features, integers, steps, operations, elements and / or components listed after "include" or "contain", and do not exclude the existence or addition of one or more other features, integers, steps, operations, elements, components and / or sets thereof. "Up", "down", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] The present scheme provides a large-bandwidth optical fiber type acousto-optic modulator, as shown in the accompanying Figure 2As shown, it comprises a base plate 8, an input fiber collimator 1, a polarization beam splitter prism 2, a first acousto-optic modulator 3, a second acousto-optic modulator 4, a quarter-wave plate 5, a mirror 6 and an output fiber collimator 7, wherein the input fiber collimator 1, the polarization beam splitter prism 2, the first acousto-optic modulator 3, the second acousto-optic modulator 4, the quarter-wave plate 5, the mirror 6 and the output fiber collimator 7 are all arranged on the base plate 8, the input fiber collimator 1 is used to output collimated light after the input polarized light is shaped, the polarization beam splitter prism 2 is located on the output light path of the input fiber collimator 1, and the polarization beam splitter prism 2 transmits the collimated light in horizontal polarization state to the first acousto-optic modulator 3. The first acousto-optic modulator 3 and the second acousto-optic modulator 4 are arranged in cascade, the center frequency and the bandwidth are variable, the second acousto-optic modulator re-shifts the frequency of the light shifted by the first acousto-optic modulator, the control driving frequencies of the first acousto-optic modulator 3 and the second acousto-optic modulator 4 satisfy a set relationship, the directions of the light shifted by the first acousto-optic modulator 3 and the second acousto-optic modulator 4 are the same, and when the first acousto-optic modulator 3 performs positive frequency shift, the second acousto-optic modulator 4 performs negative frequency shift, and when the first acousto-optic modulator 3 performs negative frequency shift, the second acousto-optic modulator 4 performs positive frequency shift, so that the light of different frequencies which is sequentially shifted by the first acousto-optic modulator 3 and the second acousto-optic modulator 4 is output in parallel, as shown in FIG. 2. Figure 3 As shown, the quarter-wave plate 5 is located between the second acousto-optic modulator 4 and the mirror, the quarter-wave plate 5 phase delays the light output by the second acousto-optic modulator 4 by 90° to form vertical polarized light and then outputs, the mirror 6 fully reflects the vertical polarized light output by the quarter-wave plate 5 and then inputs the vertical polarized light to the second acousto-optic modulator 4 through the quarter-wave plate 5 again, and the output fiber collimator 7 is located on the reflected output light path of the polarization beam splitter prism 2, and the output fiber collimator 7 shapes and then outputs the vertical polarized light reflected by the polarization beam splitter prism 2.

[0028] The working principle of the scheme is as follows: the above-mentioned large-bandwidth fiber acousto-optic modulator is used to sequentially shift the frequency of the incident light through the first acousto-optic modulator 3 and the second acousto-optic modulator 4, the light of different frequencies which is sequentially shifted by the first acousto-optic modulator 3 and the second acousto-optic modulator 4 is output in parallel, the light output by the second acousto-optic modulator 4 is fully reflected by the mirror 6 and then sequentially shifted by the second acousto-optic modulator 4 and the first acousto-optic modulator 3 and then output.

[0029] Specifically, the control driving frequency applied to the first acousto-optic modulator 3 and the driving frequency applied to the second acousto-optic modulator 4 satisfy the following set relationship:

[0030] The sum of the radio frequency of the first acousto-optic modulator 3 and the radio frequency of the second acousto-optic modulator 4 is equal to the sum of the intermediate frequency of the first acousto-optic modulator 3 and the intermediate frequency of the second acousto-optic modulator 4. One of the frequencies increases, and the other one needs to decrease the same frequency. For example, when the first acousto-optic modulator 3 performs positive frequency shiftf 1 When the first AOM 3 is positive frequency shift -f 2 When the first AOM 3 is negative frequency shift f 1 When the second AOM 4 is positive frequency shift f 2 .

[0031] Here, the first AOM 3 is positive frequency shift f 1 , the second AOM 4 is negative frequency shift -f 2 , the total frequency shift is f 1 -f 2 According to the formula of the deflection angle of the AOM:

[0032] θ = λf / V

[0033] Where λ is the wavelength of the light, V is the speed of sound, the deflection angle of the first AOM 3 is θ 1 , the deflection angle of the second AOM 4 is θ 2 , and the total deflection angle of the incident light after passing through the first AOM 3 and the second AOM 4 is θ, θ = θ 1 + θ 2 .

[0034] When the first AOM 3 increases the frequency df , the deflection angle of the first AOM 3 is θ 1 + dθ , and the frequency shift of the first AOM 3 is f 1 + df At this time, the second AOM 4 decreases the frequency df , the deflection angle of the second AOM 4 is θ 2 - dθ , and the frequency shift of the second AOM 4 is -（f 2 - df), The total deflection angle of the incident light after passing through the first AOM 3 and the second AOM 4 is still θ, θ = θ 1 + θ 2， The total frequency shift of the incident light after passing through the first acousto-optic modulator 3 and the second acousto-optic modulator 4 is f 1 -f 2 + 2df;

[0035] Since the angles of the final output light of different frequencies are unchanged and parallel to each other, all the light is returned to the original path through the mirror 6, and the frequency shift occurs again after passing through the two acousto-optic modulators, and finally a beam of light is synthesized according to the reversible optical path. Specifically, the frequency-shifted light output by the second acousto-optic modulator 4 passes through the quarter-wave plate 5 with a phase delay of 90° and reaches the mirror 6, the mirror 6 returns all the light to the original path, the returned light passes through the second acousto-optic modulator 4 and the first acousto-optic modulator 3 in turn and is frequency-shifted again, and the returned light after the second frequency shift is reflected by the polarization beam splitter prism 2 and then output and coupled into the optical fiber, the total frequency shift of the light coupled into the optical fiber is 2(2f1+2f2). f 1 -f 2 + 2df ).

[0036] This scheme can be applied to two acousto-optic modulators with the same bandwidth and arbitrary center frequencies, the intermediate frequency of the light output by the output optical fiber collimator 7 is twice the sum of the intermediate frequency of the first acousto-optic modulator 3 and the intermediate frequency of the second acousto-optic modulator 4, and the bandwidth of the light output by the output optical fiber collimator 7 is twice the sum of the bandwidth of the first acousto-optic modulator 3 and the bandwidth of the second acousto-optic modulator 4. For example, the first acousto-optic modulator 3 with a frequency range of (f1-f2) is used for negative frequency shift, and the second acousto-optic modulator 4 with a frequency range of (f2-f1) is used for positive frequency shift, then the frequency range of the frequency-shifted light output by the output optical fiber collimator 7 is (2f1-2f2). f 1 ，f 1 + df ). f 2 ，f 2 + df . （2（f 2 -f 1 - df), 2 （f 2 -f 1 + df)) .

[0037] For example, the two acousto-optic modulators of (130, 230) and (230, 330) are used to realize arbitrary frequency shift output within a bandwidth of 0-400MHz by using this scheme, as shown in the attached Figure 4As shown, the positive and negative frequency shift mode of the exchange device can also realize -400-0MHz frequency shift output. The combination of suitable acousto-optic modulators can realize frequency shift of any frequency and any bandwidth within -1000 to +1000MHz, and the wavelength of the components can be changed, and the wavelength range that can be applied by the scheme includes but is not limited to 200-2000nm.

[0038] Compared with the prior art, the utility model discloses can realize the laser frequency shift of large bandwidth under the condition of fiber input and output. The utility model discloses two bandwidth type acousto-optic modulators are placed in cascade, and the center frequency and bandwidth are changeable, and the control driving frequency of two acousto-optic modulators always satisfies fixed relation, thereby making the output light of different frequencies parallel to each other, and since the angle of the output light of different frequencies is invariable, the light is returned to the original path through the reflecting mirror 6 and is finally synthesized into a bundle, thereby being coupled into the fiber, realizing the input and output of large bandwidth fiber, and the combination of suitable acousto-optic modulators can realize frequency shift of any frequency and any bandwidth. The scheme solves the problem that the bandwidth of the fiber type acousto-optic modulator in the prior art is limited by the fiber coupling angle, and through the cascade of two bandwidth type acousto-optic modulators, the fiber type acousto-optic modulator of super large bandwidth can be realized. The scheme can be applied to two bandwidth type acousto-optic modulators with the same center frequency, and the output light frequency is twice the sum of the frequencies of the two devices, and the bandwidth is twice the sum of the bandwidths of the two devices. The combination of suitable acousto-optic modulators can realize frequency shift of any frequency and any bandwidth within -1000 to +1000MHz, and the wavelength range that can be applied by the scheme includes but is not limited to 200-2000nm.

[0039] Finally, it needs to be explained that the above embodiments are only used to illustrate the technical scheme of the utility model and not to limit the technical scheme, and those of ordinary skill in the art should understand that the technical scheme of the utility model is modified or replaced equivalently without departing from the purpose and scope of the technical scheme, and should be covered in the scope of the claims of the utility model.

Claims

1. A large bandwidth fiber optic acousto-optic modulator characterized by, The device comprises a base plate, a first acousto-optic modulator, a second acousto-optic modulator and a mirror, the first acousto-optic modulator, the second acousto-optic modulator and the mirror are all mounted on the base plate, the first acousto-optic modulator and the second acousto-optic modulator are arranged in cascade, the sum of the radio frequency of the first acousto-optic modulator and the radio frequency of the second acousto-optic modulator is equal to the sum of the intermediate frequency of the first acousto-optic modulator and the intermediate frequency of the second acousto-optic modulator, the mirror is located on the output light path of the second acousto-optic modulator, and the mirror fully reflects the frequency-shifted light output by the second acousto-optic modulator and returns to the second acousto-optic modulator again.

2. The large bandwidth fiber optic acousto-optic modulator of claim 1, wherein, The device further comprises a polarization beam splitting prism and a quarter-wave plate, the polarization beam splitting prism is located on the input light path of the first acousto-optic modulator, the polarization beam splitting prism transmits the collimated light in horizontal polarization state to the first acousto-optic modulator, the quarter-wave plate is located between the second acousto-optic modulator and the mirror, the quarter-wave plate phase delays the frequency-shifted light output by the second acousto-optic modulator by 90° to form vertical polarization light and then outputs, and the mirror fully reflects the vertical polarization light output by the quarter-wave plate and then inputs the vertical polarization light to the second acousto-optic modulator again through the quarter-wave plate.

3. The large bandwidth fiber optic AOM of claim 2, wherein, The device further comprises an input optical fiber collimator and an output optical fiber collimator, the input optical fiber collimator shapes the input polarized light into collimated light and then outputs, the polarization beam splitting prism is located on the output light path of the input optical fiber collimator, and the output optical fiber collimator is located on the reflected output light path of the polarization beam splitting prism, the output optical fiber collimator shapes the vertical polarization light reflected by the polarization beam splitting prism and then outputs.

4. The large bandwidth fiber optic AOM of claim 3, wherein, The intermediate frequency of the light output by the output optical fiber collimator is twice the sum of the intermediate frequency of the first acousto-optic modulator and the intermediate frequency of the second acousto-optic modulator, and the bandwidth of the light output by the output optical fiber collimator is twice the sum of the bandwidth of the first acousto-optic modulator and the bandwidth of the second acousto-optic modulator.

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