阅读说明：本技术 一种基于自加速平面波光束的空分复用和解复用方法及系统 (Space division multiplexing and demultiplexing method and system based on self-accelerating plane wave beam ) 是由 陈钰杰 林树青 闻远辉 余思远 于 2020-06-18 设计创作，主要内容包括：本发明公开了一种基于自加速平面波光束的空分复用和解复用方法,该方法包括：对光纤中出射的光场扩束并对扩束后的光场进行空间相位调制和一维空间傅里叶变换,得到自加速平面波光束模式；将自加速平面波光束模式经过一维空间傅里叶变换后进行空间相位解调制,并将解调制后的光场经过二维空间傅里叶变换得到分离后的光场。该系统包括：复用模块和解复用模块。通过使用本发明,可以提升通信容量和提高空间利用率。本发明作为一种基于自加速平面波光束的空分复用和解复用方法及系统,可广泛应用于光通信应用领域。(The invention discloses a space division multiplexing and demultiplexing method based on self-accelerating plane wave beams, which comprises the following steps: expanding the light field emitted from the optical fiber, and performing spatial phase modulation and one-dimensional spatial Fourier transform on the expanded light field to obtain a self-accelerating plane wave light beam mode; and performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam mode, then performing spatial phase demodulation, and performing two-dimensional spatial Fourier transform on the demodulated light field to obtain a separated light field. The system comprises: a multiplexing module and a demultiplexing module. By using the invention, the communication capacity can be improved and the space utilization rate can be improved. The space division multiplexing and demultiplexing method and system based on the self-accelerating plane wave beam can be widely applied to the field of optical communication application.)

1. A space division multiplexing and demultiplexing method based on self-accelerating plane wave beams is characterized by comprising the following steps:

expanding the light field emitted from the optical fiber, and performing spatial phase modulation and one-dimensional spatial Fourier transform on the expanded light field to obtain a self-accelerating plane wave light beam mode;

and performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam mode, then performing spatial phase demodulation, and performing two-dimensional spatial Fourier transform on the demodulated light field to obtain a separated light field.

2. The spatial multiplexing and demultiplexing method according to claim 1, wherein the step of expanding the light field emitted from the optical fiber and performing spatial phase modulation and one-dimensional spatial fourier transform on the expanded light field to obtain the self-accelerating plane wave beam mode specifically comprises:

expanding and injecting each path of Gaussian spots emitted from the optical fiber into a first spatial light modulator for spatial phase premodulation to obtain each mode light field after spatial phase premodulation;

and carrying out one-dimensional spatial Fourier transform on each mode light occasion beam after spatial phase premodulation through a first cylindrical lens to generate a self-accelerating plane wave light beam mode.

3. The method according to claim 2, wherein the center of the gaussian spot is aligned with the center of the first spatial light modulator and the optical axis is perpendicular to the plane of the first spatial light modulator.

4. The spatial multiplexing and demultiplexing method according to claim 3, wherein said first spatial light modulator is loaded with a phase pattern, and the phase pattern expression is as follows:

M(x₁,y₁)＝[iΦ(x₁)+iωy₁]

the phi (x)₁) Is x₁Initial spectral phase corresponding to a dimensionally curved trajectory, i being an imaginary unit, ω being y₁Linear phase coefficient in dimension, said M (x)₁,y₁) Is a phase pattern, said x₁And y₁Representing the dimension of the first plane.

5. The method according to claim 4, wherein the step of performing spatial phase demodulation after performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam pattern, and performing two-dimensional spatial Fourier transform on the demodulated optical field to obtain a separated optical field specifically comprises:

performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam mode through a second cylindrical lens to obtain a Gaussian spot carrying a superposition phase;

compensating the phase of the Gaussian spot in the x dimension through a second spatial light modulator to obtain a Gaussian envelope light field with a linear phase carried in the y dimension;

and performing two-dimensional space Fourier transform on the Gaussian envelope light field through a spherical lens to obtain a separated light field.

6. The spatial multiplexing and demultiplexing method according to claim 5, wherein the phase compensation of the gaussian spot in the x dimension by the second spatial light modulator is specifically performed by loading a frequency domain compensation phase in the x dimension by the second spatial light modulator, and the compensation phase is expressed as follows:

D(x₃,y₃)＝exp[-iΦ(-x₃)]

said, said x₃And y₃Representing the dimension of the third plane.

7. A spatial multiplexing and demultiplexing system based on self-accelerating plane wave beams, comprising:

and the multiplexing module is used for expanding the light field emitted from the optical fiber, performing spatial phase modulation on the expanded light field, combining the light field, and performing one-dimensional spatial Fourier transform to obtain a self-accelerating plane wave light beam mode.

And the demultiplexing module is used for demodulating the spatial phase of the self-accelerating plane wave beam mode after one-dimensional spatial Fourier transform, and obtaining a separated light field by performing two-dimensional spatial Fourier transform on the demodulated light field.

8. The system according to claim 7, wherein the multiplexing module comprises a beam expanding module, a first spatial light modulator, a beam combining module and a first cylindrical lens, the demultiplexing module comprises a second cylindrical lens, a beam splitting module, a second spatial light modulator and a spherical lens, the pre-modulation plane of the first spatial light modulator is located at the front focal plane of the first cylindrical lens, the demodulation plane of the second spatial light modulator is located at the rear focal plane of the second cylindrical lens, and the demodulation plane of the second spatial light modulator is located at the front focal plane of the spherical lens.

9. The system according to claim 8, further comprising a light intensity detection module, wherein the light intensity detection module has a light intensity detection plane located at the back focal plane of the ball lens.

10. The system according to claim 9, wherein the optical fields of the front focal plane and the back focal plane of the first cylindrical lens satisfy a one-dimensional spatial fourier transform relationship, the optical fields of the front focal plane and the back focal plane of the second cylindrical lens satisfy a one-dimensional spatial fourier transform relationship, and the optical fields of the front focal plane and the back focal plane of the spherical lens satisfy a two-dimensional spatial fourier transform relationship.

Technical Field

The invention relates to the field of optical communication application, in particular to a space division multiplexing and demultiplexing method and system based on self-accelerating plane wave beams.

Background

Since the first observation of the light beam in the experiment in 2007, the self-accelerating light beam represented by the light beam is spotlighted by optical researchers due to the characteristics of being bendable and self-healing, and the like, and is practically used in many cases. When the self-accelerating light beam is applied to free space optical communication as a carrier, the flexibility of the self-accelerating light beam can play the advantage of flexibly bypassing obstacles, and the self-healing performance of the self-accelerating light beam has the capacity of resisting disturbance, so that the self-accelerating light beam can adapt to different free space scenes. In the existing related research, signal transmission is limited to a single channel, and compared with the existing other free space optical communication, the communication capacity is limited, and the resource utilization rate of the space is not high. With the proposition and development of a caustic design method and the unified connection of the wigner function to the track and the angular spectrum and the field distribution of the light field thereof, the construction means of the self-accelerating light beam are greatly enriched, and researchers can transmit the light beam in the space along more flexible and diversified curved tracks. The design method comprises the step of regulating and controlling the amplitude and the phase of the light field, common modulating devices are phase modulating devices such as a phase plate and a spatial light modulator, the construction process is divided into control in a space real domain and a frequency domain, the phase modulating devices for real domain control directly act on the phase of the light field, and the control in the frequency domain acts on the amplitude of the real space light field through the Fourier transform function of the lens to modulate the Fourier space phase. Much of the research attention on self-accelerating beams has focused on the flexible design of trajectories, and in earlier research work, a series of orthogonal airy beam families, solved from wave equations, were discovered. The orthogonality of the spatial modes of the bent beams can be exploited to broaden the number of beam modes transmitted in a confined space, but there is no insight into the exploitation or use of these orthogonal modes, such as mode generation, multiplexing and demultiplexing.

The modular division multiplexing has considerable development and application prospect for improving communication capacity and space utilization rate. In a multimode multiplexing network, mode generation, multiplexing and demultiplexing all depend on mode precision control, wherein the most basic is to realize conversion between a gaussian mode in an optical fiber and a transmission mode in a space. Key indicators of mode conversion are high efficiency, low loss, and low crosstalk of mode conversion. The existing free space optical communication multiplexing/demultiplexing link depends on multiple phase regulation, most of the links have complicated optical systems, the alignment precision is extremely high, and the optical field generates non-negligible energy loss through a plurality of optical elements

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a space division multiplexing and demultiplexing method and system based on an auto-accelerating plane wave beam, which implement space division multiplexing based on a compact optical path, improve communication capacity and improve space utilization.

The first technical scheme adopted by the invention is as follows: a space division multiplexing and demultiplexing method based on self-accelerating plane wave beams comprises the following steps:

expanding the light field emitted from the optical fiber, and performing spatial phase modulation and one-dimensional spatial Fourier transform on the expanded light field to obtain a self-accelerating plane wave light beam mode;

and performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam mode, then performing spatial phase demodulation, and performing two-dimensional spatial Fourier transform on the demodulated light field to obtain a separated light field.

Further, the step of expanding the light field emitted from the optical fiber and performing spatial phase modulation and one-dimensional spatial fourier transform on the expanded light field to obtain the self-accelerating plane wave beam mode specifically includes:

expanding and injecting each path of Gaussian spots emitted from the optical fiber into a first spatial light modulator for spatial phase premodulation to obtain each mode light field after spatial phase premodulation;

and carrying out one-dimensional spatial Fourier transform on each mode light occasion beam after spatial phase premodulation through a first cylindrical lens to generate a self-accelerating plane wave light beam mode.

Further, the center of the Gaussian spot is aligned with the center of the first spatial light modulator, and the optical axis is perpendicular to the plane of the first spatial light modulator.

Further, the first spatial light modulator is loaded with a phase pattern, and the phase pattern expression is as follows:

M(x₁,y₁)＝[iΦ(x₁)+iωy₁]

the phi (x)₁) Is x₁Initial spectral phase corresponding to a dimensionally curved trajectory, i being an imaginary unit, ω being y₁Linear phase coefficient in dimension, said M (x)₁,y₁) Is a phase pattern, said x₁And y₁Representing the dimension of the first plane.

Further, the step of performing spatial phase demodulation on the self-accelerating plane wave beam mode after one-dimensional spatial fourier transform, and performing two-dimensional spatial fourier transform on the demodulated optical field to obtain a separated optical field specifically includes:

performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam mode through a second cylindrical lens to obtain a Gaussian spot carrying a superposition phase;

compensating the phase of the Gaussian spot in the x dimension through a second spatial light modulator to obtain a Gaussian envelope light field with a linear phase carried in the y dimension;

and performing two-dimensional space Fourier transform on the Gaussian envelope light field through a spherical lens to obtain a separated light field.

Further, the phase of the gaussian spot in the x dimension is cancelled by the second spatial light modulator, specifically, the phase of the gaussian spot in the x dimension is cancelled by loading a frequency domain compensation phase in the x dimension by the second spatial light modulator, and the compensation phase expression is as follows:

D(x₃,y₃)＝exp[-iΦ(-x₃)]

said, said x₃And y₃Representing the dimension of the third plane.

The second technical scheme adopted by the invention is as follows: a self-accelerating plane wave beam based spatial multiplexing and demultiplexing system comprising:

and the multiplexing module is used for expanding the light field emitted from the optical fiber, performing spatial phase modulation on the expanded light field, combining the light field, and performing one-dimensional spatial Fourier transform to obtain a self-accelerating plane wave light beam mode.

And the demultiplexing module is used for demodulating the spatial phase of the self-accelerating plane wave beam mode after one-dimensional spatial Fourier transform, and obtaining a separated light field by performing two-dimensional spatial Fourier transform on the demodulated light field.

Further, multiplexing module includes beam expanding module, first spatial light modulator, closes and restraints module and first cylindrical lens, it includes second cylindrical lens, beam splitting module, second spatial light modulator and ball lens to demultiplex the module, the premodulation plane of first spatial light modulator is located the preceding focal plane of first cylindrical lens, the demodulation plane of second spatial light modulator is located the back focal plane of second cylindrical lens, the demodulation plane of second spatial light modulator is located the preceding focal plane of ball lens.

Further, the device also comprises a light intensity detection module, wherein a light intensity detection plane of the light intensity detection module is positioned on the back focal plane of the ball lens.

Further, the light fields of the front focal plane and the rear focal plane of the first cylindrical lens satisfy the relationship of one-dimensional spatial fourier transform, the light fields of the front focal plane and the rear focal plane of the second cylindrical lens satisfy the relationship of one-dimensional spatial fourier transform, and the light fields of the front focal plane and the rear focal plane of the spherical lens satisfy the relationship of two-dimensional spatial fourier transform.

The method and the system have the beneficial effects that: the invention converts the light output by the single-mode optical fiber into the self-accelerating plane wave light beam through phase pre-modulation, combines the light into a space channel for simultaneous transmission, improves the number of channels in the space, and separates out the signals transmitted together through demultiplexing, thereby achieving the effects of improving the communication capacity and the space utilization rate.

Drawings

FIG. 1 is a flow chart of the steps of a spatial multiplexing and demultiplexing method based on self-accelerating plane wave beams according to the present invention;

FIG. 2 is a flow chart of steps of an embodiment of the present invention;

FIG. 3 is a block diagram of a spatial multiplexing and demultiplexing system based on self-accelerating plane wave beams according to the present invention;

fig. 4 is a diagram of the structure of an apparatus according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

In order to improve the resource utilization rate of free space bending light beam communication, the orthogonal self-accelerating plane wave light beam is used as a multiplexing space mode, and mode generation, multiplexing and demultiplexing of the same mode family are efficiently realized through reasonable configuration of a phase modulation module and a Fourier transform module. The flexibility and the self-healing performance of the self-accelerating light beam are kept, and meanwhile, the number of modes for transmitting data is increased, and the freedom degree of free space self-accelerating light beam communication is greatly enriched as a space division multiplexing technology.

As shown in fig. 1, the present invention provides a spatial multiplexing and demultiplexing method based on self-accelerating plane wave beam, which includes the following steps:

s101, expanding the light field emitted from the optical fiber, and performing spatial phase modulation and one-dimensional spatial Fourier transform on the expanded light field to obtain a self-accelerating plane wave beam mode.

Specifically, the gaussian spot output from the light is expanded and enters the first spatial light modulator 3, and the expanded gaussian spot covers enough pixels on the first spatial light modulator 3 to carry enough phase information.

S102, carrying out spatial phase demodulation on the self-accelerating plane wave beam mode after one-dimensional spatial Fourier transform, and carrying out two-dimensional spatial Fourier transform on the demodulated light field to obtain a separated light field;

as a preferred embodiment of the method, the step of expanding the light field emitted from the optical fiber, and performing spatial phase modulation and one-dimensional spatial fourier transform on the expanded light field to obtain the self-accelerating plane wave beam mode further includes:

expanding and injecting each path of Gaussian spots emitted from the optical fiber into the first spatial light modulator 3 for spatial phase premodulation to obtain each mode light field after spatial phase premodulation;

in particular, the first spatial light modulator 3 is loaded with a hybrid phase M (x)₁,y₁) The x-dimension phase distribution is a frequency domain phase related to the self-accelerating light beam track, and the y-dimension is linear distribution corresponding to the mode, so that the expanded Gaussian light spot is pre-modulated into a Gaussian envelope light field with a mixed phase.

And (3) performing one-dimensional spatial Fourier transform on each mode light occasion beam after spatial phase premodulation through a first cylindrical lens 5 to generate an auto-acceleration plane wave light beam mode.

Specifically, each path of light after being pre-modulated is combined, the combined light field is subjected to x-dimension one-dimensional Fourier transform through the first cylindrical lens 5, and a self-accelerating plane wave light beam mode is generated on the back focal plane of the first cylindrical lens 5.

Wherein, the cross-section light field expression of the single self-accelerating plane wave beam mode is as follows:

and correspondingly bending the one-dimensional field distribution of the light beam on the initial plane in the x dimension, wherein the mode is bent according to a preset track in the x dimension, and the linear phase of a specific linear coefficient is reserved in the y dimension.

As a further preferred embodiment of the method the center of the gaussian spot is aligned with the center of the first spatial light modulator 3 and the optical axis is perpendicular to the plane of the first spatial light modulator 3.

Further as a preferred embodiment of the method, the first spatial light modulator 3 is loaded with a phase pattern, and the phase pattern expression is as follows:

M(x₁,y₁)＝[iΦ(x₁)+iωy₁]

the phi (x)₁) Is x₁Initial spectral phase corresponding to a dimensionally curved trajectory, i being an imaginary unit, ω being y₁Linear phase coefficient in dimension, said M (x)₁,y₁) Is a phase pattern, said x₁And y₁Representing the dimension of the first plane.

As a preferred embodiment of the method, the step of performing spatial phase demodulation on the self-accelerating plane wave beam mode after one-dimensional spatial fourier transform, and performing two-dimensional spatial fourier transform on the demodulated optical field to obtain a separated optical field specifically includes:

performing one-dimensional spatial Fourier transform on the self-accelerating plane wave beam mode through a second cylindrical lens 6 to obtain a Gaussian spot carrying a superposition phase;

compensating the phase of the Gaussian spot in the x dimension through a second spatial light modulator 7 to obtain a Gaussian envelope light field with a linear phase carried in the y dimension;

and (3) performing two-dimensional space Fourier transform on the Gaussian envelope light field through a ball lens 8 to obtain a separated light field.

Specifically, the self-accelerating plane wave beam mode passes through the second cylindrical lens 6, the focal plane is restored to be a Gaussian envelope carrying the superposed phase behind the second cylindrical lens 6, the phase compensation is carried out on the second spatial light modulator 7, the Gaussian envelope light field after the phase compensation passes through the spherical lens 8, due to the linear phase in the direction, the light field is focused on the rear focal plane of the spherical lens 8, the relation of the space Fourier transform is satisfied by the front focal plane of the spherical lens 8 and the light field of the rear focal plane, and the light field is focused on the position (x) on the rear focal plane of the spherical lens 8₄＝0,y₄A), the expression of a is as follows:

a＝λfω

the λ is the wavelength of light, the f is the parity of the spherical lens 8, and the ω is the mode linear phase coefficient.

Further, as a preferred embodiment of the method, the phase of the gaussian spot in the x dimension is cancelled by the second spatial light modulator 7, specifically, the phase of the gaussian spot in the x dimension is cancelled by the frequency domain compensation phase loaded on the x dimension by the second spatial light modulator 7, and the compensation phase expression is as follows:

D(x₃,y₃)＝exp[-iΦ(-x₃)]

said x₃And y₃A dimension representing a third plane, the compensation phase D (x)₃,y₃) And the premodulation phase satisfies the cancellation relation in x dimension.

As shown in fig. 3, a spatial multiplexing and demultiplexing system based on an auto-accelerating plane wave beam includes:

and the multiplexing module expands the light field emitted from the optical fiber, performs spatial phase modulation on the expanded light field, combines the light field, and performs one-dimensional spatial Fourier transform to obtain a self-accelerating plane wave light beam mode.

And the demultiplexing module is used for demodulating the spatial phase of the self-accelerating plane wave beam mode after one-dimensional spatial Fourier transform, and obtaining a separated light field by performing two-dimensional spatial Fourier transform on the demodulated light field.

Further as a preferred embodiment of the present system, the multiplexing module includes a beam expanding module, a first spatial light modulator 3, a beam combining module, and a first cylindrical lens 5, the demultiplexing module includes a second cylindrical lens 6, a beam splitting module, a second spatial light modulator 7, and a spherical lens 8, a pre-modulation plane of the first spatial light modulator 3 is located at a front focal plane of the first cylindrical lens 5, a demodulation plane of the second spatial light modulator 7 is located at a rear focal plane of the second cylindrical lens 6, and a demodulation plane of the second spatial light modulator 7 is located at a front focal plane of the spherical lens 8.

Specifically, the first spatial light modulator 3 is used for pre-modulation at a transmitting end, and is loaded with a mixed phase obtained by superimposing a spectral phase of a beam x-dimensional curved trajectory and a y-dimensional linear phase, and the second spatial light modulator is used for demodulation at a receiving end and is loaded with a compensation pattern of the x-dimensional spectral phase.

Further as a preferred embodiment of the present system, the present system further comprises a light intensity detection module, and a light intensity detection plane of the light intensity detection module is located on the back focal plane of the ball lens 8.

Further as a preferred embodiment of the present system, the light fields of the front focal plane and the back focal plane of the first cylindrical lens 5 satisfy a one-dimensional fourier transform relationship, the light fields of the front focal plane and the back focal plane of the second cylindrical lens 6 satisfy a one-dimensional fourier transform relationship, and the light fields of the front focal plane and the back focal plane of the spherical lens 8 satisfy a two-dimensional fourier transform relationship.

Specifically, with reference to fig. 4, the light intensity detection module may be formed by a video camera or an optical fiber array, and obtains light intensity distribution information by shooting an image or coupling a light field into different optical fibers, the light intensity detection module of the present embodiment employs a camera, and the first spatial light modulator 3, the second spatial light modulator 7, the first cylindrical lens 5, and the second cylindrical lens 6 are arranged as a 4f system.

The specific embodiment of the system is as follows:

referring to fig. 4, a space division multiplexing and demultiplexing system based on self-accelerating plane wave light beams includes a laser 1, a beam expanding lens group 2, a first spatial light modulator 3, a beam combining module, a first cylindrical lens 5, a second cylindrical lens 6, a second spatial light modulator 7, a beam splitting module, a ball lens 8 and a camera 9, the beam combining module and the beam splitting module employ a beam splitter 4, a pre-modulation plane of the first spatial light modulator 3 is located at a front focal plane of the first cylindrical lens 5, a demodulation plane of the second spatial light modulator 7 is located at a rear focal plane of the second cylindrical lens 6, and a demodulation plane of the second spatial light modulator 7 is located at a front focal plane of the ball lens 8.

The embodiment is illustrated in the process of generating and passing through the demultiplexer in one mode, and similarly, the generation and beam combination processes in other modes can be realized by increasing the numbers of the lasers 1, the beam expanding lens group 2 and the first spatial light modulator 3.

The contents in the above method embodiments are all applicable to the present system embodiment, the functions specifically implemented by the present system embodiment are the same as those in the above method embodiment, and the beneficial effects achieved by the present system embodiment are also the same as those achieved by the above method embodiment.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.