Multi-core optical fiber and acousto-optic modulation device

Abstract

A multi-core optical fiber and an acousto-optic modulation device. The multi-core optical fiber comprises: an acoustic-excitation core, a plurality of outer cores, a trench layer, and a cladding; the acoustic-excitation core is located at the circle center position of the cladding, and the distances between the acoustic-excitation core and the plurality of outer cores are equal; the trench layer is arranged on the outer side of the acoustic-excitation core; and the plurality of outer cores have the same core spacing and are annularly arranged around the acoustic-excitation core. By using the acoustic-excitation core, the multi-core optical fiber can simultaneously modulate a plurality of light-guiding cores within the cladding, achieving consistent modulation effects.

Description

Multi-core optical fiber and acousto-optic modulation device TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber technology, and in particular to a multi-core optical fiber and an acousto-optic modulation device. BACKGROUND

[0002] With the rapid development of optical fiber communication technology, multi-core optical fibers have shown great application potential in high-speed data communication and optical fiber sensing and communication integrated systems due to their unique transmission advantages. However, the existing acousto-optic modulation technology of optical fibers is limited by the acoustic response frequency of acousto-optic crystals, and the modulation bandwidth is difficult to break through 400MHz, which cannot meet the needs of high-speed and high-capacity data transmission.

[0003] In the prior art, the structure of a multi-core optical fiber usually includes a plurality of cores and a common cladding region. Each core has independent transmission capability, but due to the existing acousto-optic modulation technology, only single-core acousto-optic modulation can be achieved. If the modulation of each core in the multi-core optical fiber is to be achieved, a large number of acousto-optic modulators and fan-in fan-out (FIFO) devices need to be used, and each core needs to be equipped with an independent acousto-optic modulator and fan-in fan-out device for separate processing.

[0004] However, the structure of the above multi-core optical fiber is complex, the cost is high, and there is a problem of inconsistent modulation effect between the cores, which affects the overall transmission quality. SUMMARY

[0005] The present application provides a multi-core optical fiber and an acousto-optic modulation device to solve the problem of poor acousto-optic modulation effect of the multi-core optical fiber in the prior art.

[0006] In a first aspect, the present application provides a multi-core optical fiber, comprising: an acoustic excitation core, a plurality of outer layer cores, a channel layer, and a cladding layer.

[0007] The acoustic excitation core is located at the center of the cladding, and the distance between the acoustic excitation core and the plurality of outer layer cores is the same.

[0008] The channel layer is arranged outside the acoustic excitation core.

[0009] The plurality of outer layer cores have the same core spacing and are arranged in a ring around the acoustic excitation core.

[0010] In a possible design, the mode field area of the acoustic excitation core is a preset threshold, and the range of the preset threshold is greater than or equal to 4μm 2 and less than or equal to 40μm 2 .

[0011] In a possible design, the channel layer is a double-layer channel layer.

[0012] In a possible design, the acoustic wave excitation core has a mode field area less than or equal to 15 μm at a wavelength of 1550 nm 2 .

[0013] In a possible design, the acoustic wave excitation core has a mode field area greater than or equal to 5 μm 2 .

[0014] In a possible design, the number of outer layer cores is 3, 4, 6 or 8.

[0015] In a second aspect, the present application provides an acousto-optic modulation device, comprising: the multi-core optical fiber in the first aspect and any one of the embodiments of the first aspect;

[0016] The multi-core optical fiber is configured to perform acousto-optic modulation on the target optical fiber.

[0017] The target optical fiber comprises a plurality of cores and a cladding.

[0018] The number and arrangement of the plurality of cores of the target optical fiber are consistent with those of the plurality of outer layer cores of the multi-core optical fiber, and the target optical fiber does not have a core at the center of the cladding.

[0019] In a possible design, the device further comprises: a fan-in device, a fan-out device and a pump light wave end.

[0020] The fan-in device and the fan-out device are configured to connect the multi-core optical fiber and the target optical fiber.

[0021] The pump light wave end is connected to the acoustic wave excitation core and configured to emit pump light to the acoustic wave excitation core.

[0022] In a possible design, the pump light wave end is sequentially connected to a light source, a phase modulator and an optical isolator, the phase modulator is further connected to a microwave signal source, and the optical isolator is connected to the acoustic wave excitation core.

[0023] In a possible design, the fan-in device comprises a first fan-in device and a second fan-in device, and the fan-out device comprises a first fan-out device and a second fan-out device.

[0024] The channels of the first fan-out device and the channels of the second fan-in device are configured to correspond to the plurality of cores of the target optical fiber.

[0025] The channels of the first fan-in device and the channels of the second fan-out device are configured to correspond to the cores of the multi-core optical fiber.

[0026] The first fan-out device is configured to receive an optical signal transmitted by the target optical fiber and transmit the optical signal to the multi-core optical fiber via the first fan-in device.

[0027] The second fan-out device is configured to receive an acousto-optically modulated optical signal of the multi-core optical fiber and transmit the optical signal to the target optical fiber via the second fan-in device.

[0028] In one possible design, the plurality of outer layer channels of the first fan-in are used to connect the channels of the first fan-in with the plurality of outer layer cores of the multicore optical fiber;

[0029] The plurality of outer layer channels of the second fan-in are used to connect the plurality of outer layer cores of the multicore optical fiber with the channels of the second fan-out;

[0030] The middle channel of the first fan-in is used to connect the pump light wave port with the acoustic wave excitation core.

[0031] The multicore optical fiber and the acousto-optic modulation device provided by the present application are configured by arranging an acoustic wave excitation core in the center of the plurality of outer layer cores arranged in a ring, and using the FBS effect of the acoustic wave excitation core to excite a radially polarized mode (R 0m ) acoustic wave with circumferentially symmetric distribution and polarization insensitivity in the multicore optical fiber. 0m The acoustic wave fills the entire cross section of the multicore optical fiber and extends to the outside of the cladding of the optical fiber, thereby achieving simultaneous modulation of a plurality of light guiding cores in the cladding, and because the R 0m acoustic wave is circumferentially symmetrically distributed, the modulation effect between the cores is consistent, thereby solving the problem of poor acousto-optic modulation effect of the multicore optical fiber in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Fig. 1 is a schematic diagram of the cross-sectional structure of a multicore optical fiber according to an embodiment of the present application;

[0034] Fig. 2 is a schematic diagram of the relationship between the FBS gain coefficient and the effective mode field area at a wavelength of 1550 nm according to an embodiment of the present application;

[0035] Fig. 3 is a schematic diagram of the structure of an acousto-optic modulation device according to an embodiment of the present application;

[0036] Fig. 4 is a schematic diagram of the R 0m acoustic wave frequency distribution of a multicore optical fiber according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purposes, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in conjunction with the drawings in the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0038] It should be understood that the terms "comprising", "including", "containing", "involving", "having" and "including" indicate the presence of the specified features, steps, operations, elements, components, items, kinds and / or groups, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, items, kinds and / or groups.

[0039] The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B and / or C" means "any one of the following: A; B; C; A and B; A and C; B and C; A, B and C". There is an exception to this definition only when a combination of elements, functions, steps or operations is inherently mutually exclusive based on some way.

[0040] With the rapid development of optical fiber communication technology, multi-core optical fiber has great application potential in high-speed data communication and optical fiber sensing integrated system due to its unique transmission advantages.

[0041] Multi-core optical fiber can realize multi-channel parallel transmission in one optical fiber by concentrating multiple light guide cores in a common optical fiber cladding, which can significantly improve the single fiber transmission capacity and has significant application prospects in high-capacity optical fiber communication field. In addition, optical fiber communication system and sensing system have high commonality and compatibility in equipment devices and transmission media. With the unique structural characteristics of multi-core optical fiber, its technical advantages in optical fiber sensing application field have also been gradually recognized by people. For example, by integrating phase-sensitive optical time domain reflectometer, Raman optical time domain reflectometer, Brillouin optical time domain reflectometer and other sensing methods in different cores of the same multi-core optical fiber, distributed sensing of temperature, vibration, strain and other physical parameters can be realized, which greatly expands the sensing ability of multi-core optical fiber and has significant application prospects in aerospace, deep sea exploration, earthquake warning and perimeter security fields.

[0042] The distributed optical fiber sensing system needs to use narrow pulse light as probe light for sensing event positioning and acoustic wave excitation. The generation of pulse light needs to rely on electro-optical modulation or acousto-optical modulation, etc. The optical fiber electro-optical modulator is extremely sensitive to the polarization state of light, and the extinction ratio of the modulated light pulse is difficult to break through 40dB, which limits the measurement accuracy and sensing distance of the sensing system. While the optical fiber acousto-optical modulator can realize high extinction ratio pulse generation up to 50dB, and has better temperature stability, better light spot quality and lower cost, the device has obvious advantages.

[0043] At present, the optical fiber acousto-optical modulator usually uses a transducer to excite acoustic waves in the acousto-optical crystal to realize acousto-optical modulation. This method is subject to the lower acoustic response frequency of the acousto-optical crystal, and the modulation bandwidth of the acousto-optical modulator is difficult to break through 400MHz, which limits its application in high-speed data communication, optical fiber sensing and communication integrated system and other fields. More importantly, for multi-core optical fiber transmission or sensing system, the structure of the multi-core optical fiber usually includes multiple cores and a common cladding region, and each core has independent transmission capability. Limited by the existing acousto-optical modulation technology, only single-core acousto-optical modulation can be realized. If the modulation of each core in the multi-core optical fiber is to be realized, a large number of acousto-optical modulators and fan-in fan-out devices (FIFO) are needed, and each core is equipped with an independent acousto-optical modulator and fan-in fan-out device for individual modulation.

[0044] Therefore, there are the following disadvantages when performing acousto-optical modulation of multi-core optical fiber. First, since each core needs to be equipped with an independent acousto-optical modulator and fan-in fan-out device, the multi-core optical fiber sensing system has a complex structure and high hardware cost. Second, due to the performance difference of each modulator, the modulation effect may differ greatly between different cores, such as inconsistent parameters of modulation depth and extinction ratio, which will seriously affect the overall transmission performance of the multi-core optical fiber. In addition, the existing acousto-optical modulation technology is limited by the acoustic response frequency of the acousto-optical crystal, and the modulation bandwidth is limited, which is difficult to meet the demand of high-speed and large-capacity data transmission.

[0045] In view of the above problems, the present application provides a multi-core optical fiber and an acousto-optical modulation device. The multi-core optical fiber adopts a core arrangement mode combining a ring core and a center core, and excites a radially symmetric distributed and polarization-insensitive radial mode acoustic wave through the center core, while modulating the outer layer core arranged in a ring shape, thereby realizing simultaneous modulation of each core in the multi-core optical fiber, and having high stability characteristics of high bandwidth and consistent modulation effect distribution, thereby meeting the distributed optical fiber sensing and large-capacity data transmission demand of the multi-core optical fiber.

[0046] The technical solutions of the present application will be described in detail below with specific examples. The following specific examples can be combined with each other, and the same or similar concepts or processes may not be described in detail in some examples.

[0047] Figure 1 shows a cross-sectional structure of a multicore optical fiber according to an embodiment of the present application. As shown in Figure 1, the multicore optical fiber according to the embodiment includes an acoustic excitation core, a plurality of outer cores, a trench layer, and a cladding layer.

[0048] The acoustic excitation core is located at the center of the cladding layer, and the cladding layer is used to accommodate the cores and is made of silica.

[0049] The acoustic excitation core has the same distance to the plurality of outer cores.

[0050] The trench layer is arranged outside the acoustic excitation core, and the plurality of outer cores have the same core pitch and are arranged in a ring around the acoustic excitation core.

[0051] The multicore optical fiber according to the embodiment adopts a core arrangement mode combining a ring core and a central core. The ring core arrangement mode and the refractive index distribution of each core layer are consistent with a target multicore optical fiber, so as to perform acousto-optic modulation on the target multicore optical fiber.

[0052] The multicore optical fiber according to the embodiment utilizes the forward Brillouin scattering (FBS) effect of the acoustic excitation core to excite a radial mode (R 0m ) acoustic wave having a circumferentially symmetric distribution and being polarization-insensitive in the multicore optical fiber. 0m The R 0m acoustic wave fills the entire cross section of the multicore optical fiber and extends to the outside of the cladding layer, so as to achieve simultaneous modulation of a plurality of light guiding cores in the cladding layer. Due to the circumferentially symmetric distribution of the R 0m acoustic wave, the modulation effect of each core will be consistent. In addition, the resonance frequency of the R

[0053] In some embodiments, the trench layer is a double trench layer.

[0054] With continued reference to Figure 1, two trench layers are arranged outside the acoustic excitation core, and the refractive index depth of each trench layer is -0.0045 to -0.012. The width of each trench layer is equal and is 10 to 20 μm. The deep refractive index trench can be realized by doping germanium or boron elements in the silica material. The two trench layers can effectively confine the optical field of the acoustic excitation core, so as to avoid large power crosstalk to the outer light guiding cores due to the light mode leakage of the acoustic excitation core. The two trench layers can suppress the crosstalk to less than -70 dB / km.

[0055] In some embodiments, the mode field area of the acoustic excitation core is a preset threshold, and the preset threshold is greater than or equal to 4 μm 2 and less than or equal to 40 μm2 .

[0056] In particular, the acoustic excitation fiber core has a mode field area greater than or equal to 4 μm 2 and less than or equal to 30 μm 2 .

[0057] at a wavelength of 1550 nm, the acoustic excitation fiber core has a mode field area greater than or equal to 5 μm 2 and less than or equal to 40 μm 2 .

[0058] Optionally, the acoustic excitation fiber core has a mode field area greater than or equal to 4 μm 2 and less than or equal to 11 μm 2 .

[0059] In some embodiments, the acoustic excitation fiber core has a mode field area less than or equal to 15 μm 2 .

[0060] Optionally, the acoustic excitation fiber core has a mode field area greater than or equal to 5 μm 2 .

[0061] In this embodiment, the optical fiber has an outer diameter of 125 μm. The acoustic excitation fiber core has a small mode field area of 4-40 μm 2 to enhance the FBS effect and excite high-order R 0m acoustic waves, thereby expanding the bandwidth of the acousto-optic modulation to more than 1 GHz.

[0062] In particular, the FBS gain coefficient of the FBS effect is used to describe the acousto-optic intensity of the R 0m acoustic wave and the light field, in units of [W×km] -1 , which can be expressed as:

[0063] where k0 is the incident light wave number, n is the effective refractive index of the optical fiber, c is the speed of light in vacuum, and p is the density of the optical fiber material; Ω m is the resonance angular frequency of the R 0m acoustic wave, and Γ m is the line width of the FBS scattering spectrum.

[0064] and are the electrostrictive overlap integrals and the photoelastic overlap integrals represented by the light wave electric field E T (r) and the acoustic field , respectively, which determine the excitation efficiency of the R 0m acoustic wave mode and the acousto-optic modulation degree of the incident light wave, respectively, and are expressed as:

[0065] Where a1 = 0.66 and a2 = -1.2 are both photoelastic parameters of silica optical fiber. 'a' is the radius of the multi-core fiber, and 'r' is the component along the fiber radius.

[0066] The electric field E of light waves in the fiber core T (r) satisfies a Gaussian function distribution, which can be expressed as:

[0067] Where E0 is the Gaussian peak intensity of the electric field of the light wave, and w is the effective radius of the mode field, that is, the radius at which the electric field intensity on the Gaussian axis drops to 1 / e.

[0068] The effective mode area (A) of optical fiber eff The following proportional relationship exists between the radius of the model field and the radius of the model field: A eff =πw 2 (5)

[0069] Combining formulas (1) to (5), it can be seen that the FBS gain coefficient With effective modulus area (A) eff They are directly related, and their relationship is shown in Figure 2.

[0070] As shown in Figure 2, at a wavelength of 1550 nm, the mode field area of ​​the acoustically excited fiber core is 15 μm. 2 The corresponding minimum FBS gain coefficient is 16 [W×km]. -1 It is approximately three times that of ordinary single-mode fiber, effectively enhancing the acousto-optic effect. This is achieved by exciting different types of R... 0m The acoustic mode enables an acousto-optic modulation bandwidth of up to 1.485 GHz.

[0071] In some embodiments, the number of outer cores is 3, 4, 6 or 8.

[0072] In other words, multi-core optical fibers have 4, 5, 7, or 9 cores.

[0073] As shown in Figure 3, this application also provides an acousto-optic modulation device, including: a multi-core optical fiber in the first aspect and any embodiment of the first aspect.

[0074] Multi-core optical fibers are used for acousto-optic modulation of target optical fibers; the target optical fiber contains multiple cores and a cladding; the number and position of the multiple cores of the target optical fiber are the same as those of the multiple outer cores of the multi-core optical fiber, and no core is set at the center of the cladding of the target optical fiber.

[0075] In the embodiment, the outer core arrangement of the multicore optical fiber is consistent with the core position arrangement and the core number of the target optical fiber to be acousto-optically modulated, and the mode fields of the respective corresponding cores are matched to ensure that the light guiding core of the target optical fiber can be efficiently coupled with the light guiding core of the acousto-optically modulated multicore optical fiber.

[0076] In some embodiments, the acousto-optical modulation device further comprises a fan-in device, a fan-out device, and a pump light wave end. The fan-in device and the fan-out device are used to connect the multicore optical fiber and the target optical fiber; the pump light wave end is connected with the acoustic excitation core and is used to emit pump light to the acoustic excitation core.

[0077] In some embodiments, the pump light wave end is sequentially connected with a light source, a phase modulator, and an optical isolator. The phase modulator is further connected with a microwave signal source, and the optical isolator is connected with the acoustic excitation core.

[0078] The central wavelength of the light source is adjustable within 1310-1550 nm. The microwave signal source is used to generate multi-wavelength pump light waves to excite R 0m acoustic waves.

[0079] The optical isolator is used to isolate the backscattered light generated by the acoustic excitation core, such as Rayleigh scattering, Raman scattering, and back Brillouin scattering, so as to protect the phase modulator.

[0080] In some embodiments, the fan-in device comprises a first fan-in device and a second fan-in device, and the fan-out device comprises a first fan-out device and a second fan-out device.

[0081] Referring to FIG. 3, the fan-in device is the first fan-in device, the fan-out device is the second fan-out device, and only the outer channels of the second fan-out device are shown.

[0082] The channels of the first fan-out device and the channels of the second fan-in device are both arranged in correspondence with the plurality of cores of the target optical fiber;

[0083] The channels of the first fan-in device and the channels of the second fan-out device are both arranged in correspondence with the cores of the multicore optical fiber. That is, the channels of the first fan-in device and the channels of the second fan-out device are consistent with and distributed in accordance with the core number of the multicore optical fiber.

[0084] The first fan-out device is used to receive the optical signal transmitted by the target optical fiber and transmit the optical signal to the multicore optical fiber through the first fan-in device; and the second fan-out device is used to receive the acousto-optically modulated optical signal of the multicore optical fiber and transmit the optical signal to the target optical fiber through the second fan-in device.

[0085] In some embodiments, the plurality of outer channels of the first fan-in device are used to connect the channels of the first fan-out device and the plurality of outer cores of the multicore optical fiber. The plurality of outer channels of the second fan-out device are used to connect the plurality of outer cores of the multicore optical fiber and the channels of the second fan-in device. The middle channel of the first fan-in device is used to connect the pump light wave end and the acoustic excitation core.

[0086] In this embodiment, the channels of the fan-in and the fan-out do not interfere with each other, and can respectively transmit signals without changing the structure of the existing fan-in and fan-out, and can be directly adapted for use, thereby saving the cost of acousto-optic modulation.

[0087] Taking a five-core acousto-optic modulation multi-core optical fiber as an example, the fan-in and the fan-out of the five-core acousto-optic modulation multi-core optical fiber are five channels, and can simultaneously acousto-optically modulate multiple cores of a target four-core optical fiber. The fan-in and the fan-out of the target four-core optical fiber are four channels, and are correspondingly connected with the outer core of the acousto-optic modulation five-core optical fiber.

[0088] As shown in FIG. 3, the four channels of the fan-in of the multi-core optical fiber are correspondingly connected with the four channels of the fan-out (not shown in the figure) of the left target optical fiber, and the middle channel of the fan-in of the multi-core optical fiber is used for connecting the acoustic excitation core and the pump light wave end.

[0089] The four channels of the fan-out of the multi-core optical fiber are correspondingly connected with the four channels of the fan-in (not shown in the figure) of the right target optical fiber, so as to ensure that the modulated light wave signal can continue to be normally transmitted in the right multi-core optical fiber.

[0090] Since the FBS process satisfies the energy conservation and momentum conservation, when the frequencies of the two light waves satisfy the FBS phase matching condition, that is, the frequency difference of the two light waves is R 0m resonant frequency (ν m = Ω m / 2π), an R 0m acoustic field will be excited in the acoustic excitation core. Therefore, the multi-wavelength light wave for exciting the R 0m acoustic field selects a center frequency of ν0, and each wavelength component corresponds to a center frequency of ν i (i = -h, …, 0, …, h, h is a positive integer), and a total of 2h+1 wavelength components are included. The frequency interval between adjacent two wavelength components is ν m , and at this time, the center frequencies of the 2h+1 wavelength components are respectively ν0-h νm , …, ν0, …, ν0+h νm . The generation of the multi-wavelength pump light wave needs to tune the output frequency of the microwave signal source to ν m , load the radio frequency signal to the phase modulator, and then generate the multi-wavelength light wave.

[0091] When two light waves with the same propagation direction and the frequency difference of the forward acoustic field resonant frequency are simultaneously incident into the optical fiber, according to the FBS phase matching condition, R 0m acoustic waves will be excited in the optical fiber, which is uniquely determined by the momentum conservation and energy conservation conditions. The excited R 0m acoustic waves change the density of the optical fiber material, so that the refractive index Δn of the optical fiber is periodically changed, which can be expressed as Δn = bRI cos(2πvt) (6) m t) (6)

[0092] where b RI is the refractive index variation amplitude, v m is the resonance frequency of the excitation acoustic field, and t is time.

[0093] If the single-frequency, unmodulated target fiber optical wave field is represented as

[0094] where A is the incident optical wave field amplitude, is the initial phase, j is the imaginary unit, z is the position coordinate of the optical wave along the fiber transmission direction, and k is the incident optical wave axial wave vector.

[0095] Under the action of acousto-optic modulation, the incident target wavelength optical wave will undergo a phase shift 0m under the modulation of the excited R The modulated target wavelength optical wave field can be represented as

[0096] where l is the fiber length, and λ is the incident optical wave wavelength.

[0097] Due to the acousto-optic modulation of the R 0m acoustic wave on the optical wave, the single-frequency target wavelength optical wave will become a multi-wavelength modulated optical wave, which can be represented as

[0098] where J n is the nth-order Bessel function.

[0099] As can be seen from equation (10), the target fiber optical wave modulated by acousto-optic will have multiple frequency components in the frequency domain.

[0100] Based on the above understanding, taking a five-core acousto-optic modulation multi-core fiber as an example, the effective mode field area of the acoustic wave excitation fiber core is set to 10.5 μm, and the corresponding FBS gain coefficient is 20.8 [W×km] -1 At this time, the R 0m acoustic wave frequency distribution of the acousto-optic modulation multi-core fiber design is shown in FIG. 4.

[0101] When m = 16, the maximum acoustic intensity exists, and at this time, the R 016 acoustic wave frequency v 16 = 738.8 MHz. If the frequency of the microwave signal source is set to 738.8 MHz, then a multi-wavelength pump light with a frequency interval of 738.8 MHz will be generated.

[0102] When the multi-wavelength pump light is incident into the acoustic excitation core, a depolarized R 0m acoustic wave 0m The acoustic wave fills the entire cladding cross-section of the optical fiber and extends to the outside of the fiber cladding, which can realize simultaneous and uniform modulation of a plurality of light guiding cores in the cladding, and the acoustic-optical modulation effect of each core is highly consistent, without inter-core difference in modulation effect.

[0103] It can be predicted that if the frequency of the microwave signal source is set to R 032 the resonance frequency of the acoustic wave is 1.485 GHz, and the corresponding modulation bandwidth of the entire multi-core optical fiber acoustic-optical modulation device is 1.485 GHz.

[0104] In addition, R 03 the resonance frequency of the acoustic wave is 1.344 GHz, and if the temperature changes by 1℃, R 029 the resonance frequency of the acoustic wave and the linear corresponding coefficient of the external environment temperature increases with the increase of the value of m, and changes about 18kHz / ℃ to 169kHz / ℃. For example, R 029 the resonance frequency of the acoustic wave is 1.344 GHz, and if the temperature changes by 1℃, R 029 the frequency of the acoustic wave changes only 0.169MHz, which means that the temperature stability of the acoustic-optical modulation bandwidth can reach 0.00125%.

[0105] In summary, the multi-core optical fiber of the present application increases an acoustic excitation core at the center of the structure, uses the FBS effect to excite a depolarized (R 0m ) acoustic wave with circumferential symmetry distribution and polarization insensitivity in the multi-core optical fiber, R 0m the acoustic wave fills the entire cladding cross-section of the optical fiber and extends to the outside of the fiber cladding, which can realize simultaneous modulation of a plurality of light guiding cores in the cladding, and the acoustic-optical modulation effect of each core is highly consistent, and the entire acoustic-optical modulation device has polarization insensitivity. R 0m The acoustic wave acts as an acoustic-optical modulation sound field, and the acoustic-optical modulation bandwidth can reach 1.485GHz. By using the temperature insensitive characteristic of the resonance frequency, the temperature stability of the acoustic-optical modulation bandwidth can reach 0.00125%, and the environmental adaptability is strong.

[0106] The acoustic-optical modulation device of the present application can realize simultaneous acoustic-optical modulation of each core of the multi-core optical fiber by only two pairs of fan-in and fan-out devices, effectively saving the cost and complexity of the device.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part or all of the technical features. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-core optical fiber, characterized in that, The multi-core optical fiber includes: an acoustically excited fiber core, multiple outer fiber cores, a channel layer, and a cladding layer; The acoustically excited fiber core is located at the center of the cladding, and the acoustically excited fiber core is equidistant from the plurality of outer fiber cores; The channel layer is disposed on the outside of the acoustically excited fiber core; The multiple outer fiber cores have the same core spacing and are arranged in a ring around the acoustically excited fiber core.

2. The multi-core optical fiber according to claim 1, characterized in that, The mode field area of ​​the acoustically excited fiber core is a preset threshold, and the preset threshold range is greater than or equal to 4 μm. 2 and less than or equal to 40μm 2 .

3. The multi-core optical fiber according to claim 1, characterized in that, The channel layer is a double-layer channel layer.

4. The multi-core optical fiber according to claim 2, characterized in that, At a wavelength of 1550 nm, the mode field area of ​​the acoustically excited fiber core is less than or equal to 15 μm. 2 .

5. The multi-core optical fiber according to claim 4, characterized in that, The mode field area of ​​the acoustically excited fiber core is greater than or equal to 5 μm. 2 .

6. The multi-core optical fiber according to any one of claims 1-5, characterized in that, The number of outer fiber cores is 3, 4, 6 or 8.

7. An acousto-optic modulation device, characterized in that, The device includes a multi-core optical fiber as described in any one of claims 1-6; The multi-core optical fiber is used for acousto-optic modulation of the target optical fiber; The target optical fiber comprises multiple cores and a cladding; The number and position arrangement of the multiple cores of the target optical fiber are the same as those of the multiple outer cores of the multi-core optical fiber, and no core is set at the center position of the cladding of the target optical fiber.

8. The apparatus according to claim 7, characterized in that, The device also includes: a fan-in device, a fan-out device, and a pump optical wave terminal; The fan-in and the fan-out are used to connect the multi-core optical fiber to the target optical fiber; The pump light wavefront is connected to the acoustically excited fiber core and is used to emit pump light into the acoustically excited fiber core.

9. The apparatus according to claim 8, characterized in that, The pump light wave end is sequentially connected to a light source, a phase modulator, and an optical isolator. The phase modulator is also connected to a microwave signal source, and the optical isolator is connected to the acoustic excitation fiber core.

10. The apparatus according to claim 8, characterized in that, The fan-in device includes a first fan-in device and a second fan-in device, and the fan-out device includes a first fan-out device and a second fan-out device. The channels of the first fan-out device and the second fan-in device are both configured to correspond to multiple fiber cores of the target optical fiber; The channels of the first fan-in device and the second fan-out device are both configured to correspond to the cores of the multi-core optical fiber; The first fan-out is used to receive the optical signal transmitted by the target optical fiber and transmit it to the multi-core optical fiber via the first fan-in; The second fan-out is used to receive the acousto-optic modulated optical signal from the multi-core optical fiber and transmit it to the target optical fiber via the second fan-in.

11. The apparatus according to claim 10, characterized in that, The multiple outer channels of the first fan-in are used to connect the channels of the first fan-out to the multiple outer cores of the multi-core optical fiber; The multiple outer channels of the second fan-out are used to connect the multiple outer cores of the multi-core optical fiber to the channels of the second fan-in; The middle channel of the first fan-in is used to connect the pump light wave end to the acoustic excitation fiber core.

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