CN115993683B - Communication angle measurement integrated space laser communication device - Google Patents

Abstract

The present invention discloses a space laser communication device integrating communication and angle measurement, which belongs to the field of space laser communication technology. It uses a multi-core optical fiber to simultaneously perform beam incident angle calculation and laser communication in a common optical branch manner, including a multi-core optical fiber module and a beam incident angle calculation module. Among them, the center position optical fiber of the multi-core optical fiber is used for communication, and the non-center optical fiber is used for measuring the deviation angle of the light beam. When the light beam is in a non-optimal alignment situation, the present invention uses the optical power irradiated into the non-center fiber core to detect the light beam deviation angle, and completes the calculation of the light beam pointing deviation while communicating in a common optical branch manner, thereby avoiding the light beam energy loss in a non-common branch manner, and making the device more compact, greatly reducing the complexity of the optical path, the overall weight and cost of the device.

Description

A space laser communication device integrating communication and angle measurement

Technical Field

The present invention belongs to the technical field of space laser communication, and more specifically, relates to a space laser communication device integrating communication and angle measurement.

Background technique

Free Space Optical Communication (FSO) technology is a wireless communication technology that uses laser as an information carrier to achieve communication in free space. Space optical communication has the advantages of good security, high communication rate, fast transmission speed, convenient band selection, and large information capacity. Its terminal system is small in size, light in weight, low in power consumption, simple in construction, and highly flexible. It has great strategic needs and application value in both military and civilian fields.

Traditional space laser communication devices mainly include lasers, pan/tilts, CCD cameras, fast reflectors, four-quadrant detectors, etc. The beam capture and alignment process is mainly divided into a coarse capture process and a fine alignment process, which are performed by a coarse tracking unit and a fine tracking unit respectively. Its main disadvantage is that a part of the light needs to be separated in the beam design to be incident on a four-quadrant detector or other photoelectric detection equipment to accurately measure the incident angle of the beam, which greatly increases the complexity of the optical path, as well as the overall weight and cost of the device.

Summary of the invention

In view of the defects of the above-mentioned prior art or the need for improvement, the present invention provides a space laser communication device integrating communication and angle measurement, which is used to solve the technical problems of the complexity of the optical path, the high weight and cost of the entire device caused by the use of detection equipment such as four-quadrant detectors to measure the incident angle of the light beam in traditional space laser communication equipment.

In order to achieve the above object, the present invention provides a space laser communication device integrating communication and angle measurement, comprising:

A multi-core optical fiber module, comprising a central optical fiber and M non-central optical fibers uniformly surrounding the central optical fiber, for receiving focused incident light; wherein the end faces of the cores of the non-central optical fibers are in the same plane D and form a circular area with point O as the center; the end face of the central optical fiber and the end face of the non-central optical fiber are parallel to each other and are not located in the same plane, so that the incident light spot covers the position of the central optical fiber and the position of at least one non-central optical fiber;

A beam incident angle calculation module, used to calculate the incident angle of the incident light based on the radial offset of the light spot in multiple non-parallel radial directions in the circular area;

Wherein, for any radial direction, the radial offset of the light spot is the offset of the center point of the incident light spot in the radial direction relative to point O. Based on the characteristic that the power ratio coefficient changes linearly when the incident light moves in the radial direction, the power ratio coefficient in the radial direction acquired in real time is proportionally mapped to obtain the value; wherein, the power ratio coefficient is _Pm and _Pn are the optical powers at two power points in the radial direction;

When M is an even number, the power point is the center point of the non-central optical fiber on the circular area. In an optional implementation manner, the optical power thereon is obtained by detecting the optical power in the non-central optical fiber using a detector;

When M is an odd number, the power point is the center point of the non-central optical fiber on the circular area and a virtual point symmetrical to the center point of the non-central optical fiber about point O; the optical power at the power point symmetrical to the center point of the non-central optical fiber about point O is calculated based on the Gaussian distribution characteristics of the incident light spot on the circular area and the optical power at any three non-central optical fiber center points. In an optional implementation, the optical power at the center point of the non-central optical fiber is obtained by detecting the optical power in the non-central optical fiber using a detector.

Further preferably, the radial offset of the light spot in the i-th radial direction is:

Wherein, _Ki is the power ratio coefficient in the i-th radial direction; _{Ki_max} is the maximum value of the power ratio coefficient when the incident light moves in the i-th radial direction; _{Si_max} is the maximum offset of the center point of the light spot relative to point O when the incident light moves in the i-th radial direction.

Further preferably, the light beam incident angle calculation module calculates the incident angle of the incident light using method 1 or method 2;

In the first method, the beam incident angle calculation module obtains the position of the incident light spot on the plane D based on the radial offset of the light spot in any two non-parallel radial directions, and then obtains the incident angle of the incident light;

In the second method, the light beam incident angle calculation module combines all non-parallel radial directions in pairs, and based on the radial offset of the light spot in the two radial directions under each combination, obtains the position of the incident light spot on plane D and then calculates the average value as the final position of the incident light spot on plane D, thereby obtaining the incident angle of the incident light.

Further preferably, a rectangular coordinate system is established with point O as the origin, the positive direction of the Y axis of the rectangular coordinate system is the radial direction of any power point, and the positive direction of the X axis of the rectangular coordinate system is obtained by rotating the positive direction of the Y axis clockwise by 90°; the position of the incident light spot on plane D is represented by the offset of the center point of the incident light spot on plane D relative to point O in the rectangular coordinate system, specifically:

Wherein, Δx _ij is the offset of the center point of the incident light spot on plane D relative to point O in the X-axis direction calculated based on the radial offsets of the light spots in the non-parallel i-th radial direction and j-th radial direction; Δy _ij is the offset of the center point of the incident light spot on plane D relative to point O in the Y-axis direction calculated based on the radial offsets of the light spots in the non-parallel i-th radial direction and j-th radial direction; S _i is the radial offset of the light spot in the i-th radial direction; S _j is the radial offset of the light spot in the j-th radial direction; when M is 2N, Q is N; when M is 2N-1, Q is 2N-1;

In the following method, the calculation formula of the incident angle θ _x and θ _y of the incident light is:

In the second method, the calculation formulas for the incident angles θ _x and θ _y of the incident light are:

Wherein, _θx is the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the X-axis direction and the axial direction; _θy is the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the Y-axis direction and the axial direction; f is the focal length; and They are respectively the average values of the offsets of the center point of the incident light spot on plane D relative to point O in the X-axis direction and the average values of the offsets in the Y-axis direction, calculated based on the radial offsets of the light spots in two radial directions under each combination.

Further preferably, the light beam incident angle calculation module obtains the incident angle of the incident light based on the angle between the projection of the incident light beam on two planes formed by any two non-parallel radial directions and the axial direction of the central optical fiber and the axial direction;

Alternatively, the light beam incident angle calculation module combines all non-parallel radial directions in pairs, and based on the angle between the projection of the incident light beam on two planes formed by the two non-parallel radial directions of each combination and the axial direction of the central optical fiber and the axial direction, obtains the incident angle of the incident light and then calculates the average value as the final incident angle of the incident light;

The angle between the projection of the incident light beam on the plane formed by any radial direction and the axial direction of the central optical fiber and the axial direction is calculated based on the radial offset of the light spot in the radial direction.

Further preferably, the angle θ _i between the projection of the incident light beam on the plane formed by the i-th radial direction and the axial direction of the central optical fiber and the axial direction satisfies:

Where f is the focal length.

Further preferably, the above-mentioned space laser communication device further includes a lens for focusing the parallel light beam to the multi-core optical fiber module;

The distance from the center of the lens to the center fiber end face is the focal length of the lens.

Further preferably, the above-mentioned space laser communication device further includes:

The fan-in fan-out module is used to spatially demultiplex the cores in the multi-core optical fiber module so that each core is fanned out through M+1 optical fibers, thereby splitting the communication beam and the detection beam output by the multi-core optical fiber module; wherein the communication beam and the detection beam are incident lights coupled into the central optical fiber and the non-central optical fiber respectively;

The non-central optical fiber fanned out by the fan-in and fan-out modules is connected to the beam incident angle calculation module.

Further preferably, the above-mentioned space laser communication device further includes: a modulation and demodulation module;

The modulation and demodulation module is connected to the central optical fiber fanned out by the fan-in and fan-out module, and is used to modulate the local communication laser and transmit it through the central optical fiber when the space laser communication device serves as a transmitting end; when the space laser communication device serves as a receiving end, it demodulates the communication light beam input through the central optical fiber.

Further preferably, the above-mentioned space laser communication device is used to realize full-duplex communication; wherein the modulation and demodulation module includes:

A signal modulation module, used to modulate the local communication laser and transmit it via the central optical fiber when the space laser communication device is used as a transmitting end;

A signal demodulation module, used for demodulating the communication light beam input via the central optical fiber when the space laser communication device is used as a receiving end;

The circulator is used to combine the communication light beam input to the signal demodulation module and the modulated light beam output by the signal modulation module into the central optical fiber.

In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

1. The present invention provides a space laser communication device integrating communication and angle measurement, which uses a multi-core optical fiber to simultaneously calculate the incident angle of a beam and perform laser communication in a common optical branch mode, including a multi-core optical fiber module and a beam incident angle calculation module, wherein the center position optical fiber of the multi-core optical fiber is used for communication, and the non-center optical fiber is used for measuring the deviation angle of the beam; the present invention obtains the power ratio coefficients in multiple non-parallel radial directions in real time, and based on the characteristic that the power ratio coefficient changes linearly when the incident light moves in the radial direction, the obtained power ratio coefficient is proportionally mapped, thereby obtaining the radial offset of the light spot in multiple non-parallel radial directions, and then solving the incident angle of the incident light, and can detect the deviation angle of the beam by using the optical power irradiated into the non-center fiber core when the beam is in a non-optimal alignment situation. The calculation of the beam pointing deviation is completed while communicating in a common optical branch mode, avoiding the beam energy loss in the non-common branch mode, and making the device more compact, greatly reducing the complexity of the optical path, the overall weight and cost of the device.

2. The space laser communication device with integrated communication and angle measurement provided by the present invention adopts a circulator design to realize the common path of the transmitting and receiving light beams, so that the system can perform full-duplex communication on the same laser communication link.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a cross-sectional schematic diagram of a multi-core optical fiber module provided by the present invention when the number of non-central optical fibers is an even number;

FIG2 is a cross-sectional schematic diagram of a multi-core optical fiber module provided by the present invention when the number of non-central optical fibers is an odd number;

FIG3 is a schematic diagram of a space laser communication device with integrated communication and angle measurement provided in Example 1 of the present invention;

FIG4 is a schematic diagram of the structure of a space laser communication system integrating communication and angle measurement provided in Example 2 of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

In order to achieve the above-mentioned purpose, the present invention provides a space laser communication device integrating communication and angle measurement, which uses a multi-core optical fiber, and uses the optical fiber at the center position as the communication optical fiber, and the optical fiber at the non-center position as the detection optical fiber. The offset of the incident light beam relative to the center optical fiber is measured to realize the measurement of the incident angle of the light beam and the common optical branch for communication, which solves the problems of optical path branching, optical power loss, increased equipment weight, high cost, etc. caused by the use of photoelectric detection equipment such as four-quadrant detectors to measure the incident angle of the light beam in traditional space laser communication equipment.

Specifically, the space laser communication device provided by the present invention includes: a multi-core optical fiber module and a light beam incident angle calculation module.

The multi-core optical fiber module includes a central optical fiber and M non-central optical fibers uniformly surrounding the central optical fiber, and is used to receive focused incident light; wherein the end faces of the cores of each non-central optical fiber are in the same plane D and form a circular area with point O as the center.

It should be noted that in the spatial optical coupling scenario, the main influencing factors for the optical fiber coupling efficiency are caused by three aspects, namely axial movement error, radial movement error and incident angle error. The calculation formula for the optical fiber coupling efficiency P is as follows:

Where, A＝(kωT) ² /2, B＝G ² +(D+1) ² F ² +2DFGsinθ+D(G ² +D+1)sin ² θ, _Z0 is the radial offset, _X0 is the axial offset, θ is the angular offset, ωT is the transmitting beam waist, and ωR is the receiving beam waist.

When θ approaches zero, the coupling efficiency calculation formula is substituted into the power ratio coefficient calculation formula to theoretically derive the relationship formula between the power ratio coefficient and the radial displacement of the light spot. The change curve of the power ratio coefficient can be plotted by MATLAB software, and some areas of the curve can be approximated as a linear relationship. At the same time, the fiber coupling efficiency is simulated by ZEMAX optical design software. When only the incident angle of the light beam at the end face of the fiber is changed and the incident angle changes within the range of -0.8° to 0.8°, the fiber coupling efficiency does not change significantly. At this time, the main influencing factor of the fiber coupling efficiency is the position and size of the light spot irradiated on the end face of the fiber. It can be seen that when the light beam is deflected in a small angle range, the incident angle at the end face of the fiber has little effect on the fiber coupling efficiency. For the above coupling efficiency calculation formula, the term containing the variable θ can be eliminated.

Correspondingly, when the deflection angle of the incident light beam changes in the range of -0.8° to 0.8°, a regular change trend can be observed on the detection optical fiber. Taking a seven-core optical fiber as an example, when the incident light spot moves perpendicular to the line connecting the non-center optical fiber and the center, as shown in the cross-sectional diagram of a multi-core optical fiber in Figure 1, the optical fibers are numbered 0 to 6. The received power of each non-center optical fiber is recorded as P ₁ , P ₂ , P ₃ , P ₄ , P ₅ , and P ₆ , respectively. When the incident light spot moves perpendicular to the direction of the line connecting a non-center optical fiber and the center optical fiber, taking the radial direction corresponding to optical fiber No. 1 and optical fiber No. 4 as an example, the corresponding power ratio coefficient The value of remains unchanged. When the incident light spot moves along the direction of the line, the corresponding power ratio coefficient Linear changes. By calibrating the range of linear transformation, the spot position range or the beam incident angle range is determined. Within this range, the power ratio coefficient in each radial direction changes linearly in the corresponding radial direction. According to the above conclusion, when the beam incident angle is within the linear transformation range (at this time, the moving area of the incident light spot on plane D is the linear area), the incident angle of any beam within this range can be accurately calculated to achieve the angle measurement function.

It should be noted that the end face of the central optical fiber and the end face of the non-central optical fiber are parallel to each other and are not located in the same plane. The two are separated by a certain distance so that the incident light spot covers the position of the central optical fiber and the position of at least one non-central optical fiber when moving in the linear region, thereby ensuring that communication and angle measurement can be achieved simultaneously; wherein, the end face of the central optical fiber can protrude outward or be recessed inward relative to the end face of the non-central optical fiber, as long as it is ensured that when the incident light beam deviates at any angle in the linear region, the incident light spot can cover the position of the central optical fiber and the position of at least one non-central optical fiber. Specifically, in this embodiment, the spacing between the center points of two adjacent optical fibers is 41.5μm. The spacing between the end face of the central optical fiber and the end face of the non-central optical fiber is determined according to the actual parameters such as the wavelength of the light beam and the focal length of the lens. After multiple groups of test simulations, when the distance between the end face of the central optical fiber and the end face of the non-central optical fiber is controlled at 0.4mm~0.65mm, the incident angle of the light beam can be solved by the detection optical fiber, and the receiving power of the communication optical fiber and the detection optical fiber is within an acceptable range. During design, it is necessary to ensure that the diameter of the light spot incident on the end face of the non-center fiber is not less than the spacing d between the center points of the non-center fibers, so as to ensure that when the light spot position moves in the linear region, at least one detection fiber can receive the optical power signal, so as to avoid a blind spot when the light beam is incident near a zero-degree angle.

The beam incident angle calculation module is used to calculate the incident angle of the incident light based on the radial offset of the light spot in multiple non-parallel radial directions in the circular area, as compensation information for the incident light offset. Based on the compensation of the incident light offset based on the incident angle of the incident light, the light beam can be aligned to the center of the communication optical fiber, realizing the integrated function of beam angle measurement and communication using multi-core optical fiber.

Specifically, for any radial direction, the radial offset of the light spot is the offset of the center point of the incident light spot in the radial direction relative to point O. Based on the characteristic that the power ratio coefficient changes linearly when the incident light moves in the radial direction, the power ratio coefficient in the radial direction acquired in real time is proportionally mapped to obtain the power ratio coefficient; wherein the power ratio coefficient is Pm and Pn are the optical powers at two power points in the radial direction; when M is an even number, the power point is the non-central optical fiber center point on the circular area; when M is an odd number, the power point is the non-central optical fiber center point on the circular area and a virtual point symmetrical to the non-central optical fiber center point about point O, as shown in FIG2 ; the optical power at the power point symmetrical to the non-central optical fiber center point about point O is calculated based on the Gaussian distribution characteristics of the incident light spot on the circular area and the optical power of the detection light beam corresponding to any three non-central optical fibers.

Since the deflection angle of the incident light beam is controlled so that the power ratio coefficient in each radial direction is within the range of ±θ _max that varies linearly in the corresponding radial direction (in this embodiment, the deflection angle of the incident light beam is controlled to vary within the range of -0.8° to 0.8°), for any radial direction i, when the deflection angle of the incident light beam reaches the maximum, the value of the power ratio coefficient is ±K _{i_max} , and the corresponding spot detection fiber end face position S is ±S _{i_max} . After proportional mapping, the radial offset of the light spot in the i-th radial direction is:

Wherein, _Ki is the power ratio coefficient in the i-th radial direction; _{Ki_max} is the maximum value of the power ratio coefficient when the incident light moves in the i-th radial direction; _{Si_max} is the maximum offset of the center point of the light spot relative to point O when the incident light moves in the i-th radial direction.

Further, in an optional implementation manner, the light beam incident angle calculation module obtains the position of the incident light spot on plane D based on the radial offset of the light spot in any two non-parallel radial directions, and further obtains the incident angle of the incident light.

Specifically, based on the offset of the light spot in two radial directions relative to point O, combined with analytic geometry, it is obviously possible to determine the position of the plane formed by the two directions; for the convenience of representation, a coordinate formula is generally established to obtain an expression for the position of the incident light spot on the plane; it should be noted that it is not limited to a specific type of coordinate system, and the following explanation is given using a rectangular coordinate system as an example. Specifically, a rectangular coordinate system is established with point O as the origin, the positive direction of the Y-axis of the rectangular coordinate system is the radial direction of any power point, and the positive direction of the X-axis of the rectangular coordinate system is obtained by rotating the positive direction of the Y-axis clockwise by 90°; the position of the incident light spot on plane D is represented by the offset of the center point of the incident light spot on plane D relative to point O in the rectangular coordinate system.

For 2N+1 multi-core optical fibers, the non-central optical fibers are denoted as 1 to 2N. The calibration method is as follows: the incident angle θ of the incident light beam is changed, the optical power P _i (θ) (i＝1, 2, …, N) at each power point is measured, and the power ratio coefficient in each radial direction is calculated as According to the variation trend of _Ki (θ) with θ, the linear interval of Ki (θ) and the incident angle of the beam are determined, and the maximum values of the power ratio coefficient in the linear region _{K1_max} , _{K2_max} , ..., _{KN_max} and the corresponding maximum values of the spot position _{S1_max} , _{S2_max} ..., _{SN_max} are obtained. According to the above parameters, the offset distance of the current spot from point O in each radial direction can be obtained. Taking Ki _{, Kj} (1≤i<j≤N) in any two non-parallel radial directions, the spot displacements _Si and _Sj in the two directions can be obtained. The coordinates of the spot in the rectangular coordinate system can be solved according to analytic geometry, and the offsets of the center point of the incident light spot on plane D relative to point O in the X-axis direction and the Y-axis direction are obtained respectively:

For 2N multi-core optical fibers, the non-center optical fibers are denoted as 1 to 2N-1. The calibration method is as follows: change the incident angle θ of the incident light beam, and measure _Pi (θ) (i＝1,2,…,2N-1). Since the light beam is Gaussian distributed at plane D, the optical power intensity _P'i (θ) at the central symmetric position with _Pi (θ) can be uniquely determined, that is, the 2N-1 odd number of non-center optical fibers are supplemented by 4N-2 non-center optical fibers. The 4N-2 non-center optical fibers are numbered 1 to 4N-2 in clockwise order, and the power ratio coefficient in each radial direction is calculated. According to the changing trend of _Ki (θ) with θ, the linear interval of Ki (θ) and the incident angle of the light beam is determined, and the maximum values _{K1_max} , _{K2_max} ..., K _{(2N-1)_max} in the linear region are obtained, and the maximum values of the spot position are _{S1_max} , _{S2_max} ..., S _{(2N-1)_max} . The offset distance of the current spot from point O in each radial direction can be obtained. Taking _Ki , _Kj (1≤i<j≤2N-1) in two non-parallel radial directions, we can get the spot displacements _Si , _Sj in the two directions. The coordinates of the spot in the rectangular coordinate system can be solved according to analytic geometry, and the offsets of the center point of the incident light spot on plane D relative to point O in the horizontal and vertical directions are obtained respectively:

Combining the above two situations, the horizontal and vertical offsets of the center point of the incident light spot on plane D relative to point O calculated based on the radial offsets of the light spot in the non-parallel i-th radial direction and j-th radial direction are obtained:

Wherein, _Si is the radial offset of the light spot in the i-th radial direction; _Sj is the radial offset of the light spot in the j-th radial direction; when M is 2N, Q is N; when M is 2N-1, Q is 2N-1.

Specifically, in this embodiment, taking a 7-core optical fiber as an example, as shown in FIG1 , the connecting line of optical fibers 1 and 4 is defined as direction a, the connecting line of optical fibers 2 and 5 is defined as direction b, and the connecting line of optical fibers 3 and 6 is defined as direction c. Select the offset of the light spot in the two directions a and b The x coordinate of the light spot is solved according to analytical geometry, and the horizontal offset Δx and Δy of the incident light beam relative to the central optical fiber are calculated to obtain the current light spot coordinates: Then, according to the current coordinates of the light spot and the focal length f, the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the X-axis direction and the axial direction can be calculated. And the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the Y-axis direction and the axial direction

Furthermore, in an optional implementation, in order to reduce the test error, the power points in all non-parallel radial directions are comprehensively solved for the spot coordinates. Specifically, the light beam incident angle calculation module combines all non-parallel radial directions in pairs, and based on the radial offset of the spot in the two radial directions under each combination, obtains the position of the incident light spot on plane D and then calculates the average value as the final position of the incident light spot on plane D, thereby obtaining the incident angle of the incident light.

Taking M = 2N as an example, for N non-parallel radial optical fibers, we can solve The coordinates of the points are calculated and the arithmetic mean solution is obtained to obtain the final result. According to the current coordinates of the light spot, combined with the focal length, the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the X-axis direction and the axial direction can be calculated. And the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the Y-axis direction and the axial direction

Taking 7-core optical fiber as an example, three spot coordinates (Δx ₁ , Δy ₁ ), (Δx ₂ , Δy ₂ ), (Δx ₃ , Δy ₃ ) can be obtained, where Δy ₁ = _Sa , Δy ₂ = _Sa , Δy ₃ = S _b - S _c . The horizontal and vertical displacements of the light spot are obtained as Then, according to the current coordinates of the light spot and the focal length f, the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the X-axis direction and the axial direction can be calculated. And the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the Y-axis direction and the axial direction

Further, in an optional implementation manner, the beam incident angle calculation module obtains the incident angle of the incident light based on the angle between the projection of the incident light beam on two planes formed by any two non-parallel radial directions and the axial direction of the central optical fiber and the axial direction; wherein the angle between the projection of the incident light beam on the plane formed by any radial direction and the axial direction of the central optical fiber and the axial direction is calculated based on the radial offset of the light spot in the radial direction; specifically, the angle θ _i between the projection of the incident light beam on the plane formed by the i-th radial direction and the axial direction of the central optical fiber and the axial direction satisfies:

Where f is the focal length.

Further, in an optional implementation, the beam incident angle calculation module combines all non-parallel radial directions in pairs, and based on the angle between the projection of the incident light beam on two planes formed by the two non-parallel radial directions of each combination and the axial direction of the central optical fiber, obtains the incident angle of the incident light and then calculates the average value as the final incident angle of the incident light to reduce the test error. Among them, the angle between the projection of the incident light beam on the plane formed by any radial direction and the axial direction of the central optical fiber and the axial direction is calculated based on the radial offset of the light spot in the radial direction; specifically, the angle θ i between the projection of the incident light beam on the plane formed by the i-th radial direction and the axial direction of the central optical fiber and the axial direction _satisfies :

Where f is the focal length.

Furthermore, in an optional implementation, the above-mentioned space laser communication device further includes a focusing module, which is used to focus the parallel light to obtain focused incident light and transmit it to the multi-core optical fiber module;

The focusing module can be a focusing lens or a lens group. When the focusing module is a focusing lens, the distance from the center of the lens to the end face of the central optical fiber is the lens focal length, i.e., the focusing focal length. When the focusing module is a lens group, the distance from the geometric center of the lens group to the end face of the central optical fiber is the lens focal length, i.e., the focusing focal length.

In order to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments:

Embodiment 1,

A space laser communication device integrating communication and angle measurement, as shown in FIG3 , includes, in addition to the above-mentioned multi-core optical fiber module 1 and beam incident angle calculation module 4, a fan-in fan-out module 2, a modulation and demodulation module 3 and a focusing lens 5;

The focusing module 5 is used to focus the parallel light to obtain focused incident light and transmit it to the multi-core optical fiber module; the distance from the center of the lens to the end face of the central optical fiber is the focal length f of the lens.

The fan-in and fan-out module 2 is used to spatially demultiplex the cores in the multi-core optical fiber module 1, so that each core is fanned out through M+1 optical fibers (which can be single-mode optical fibers, few-mode optical fibers, multi-mode optical fibers, etc.), thereby splitting the communication beam and the detection beam output by the multi-core optical fiber module 1; wherein the communication beam and the detection beam are incident lights coupled into the central optical fiber 11 and the non-central optical fiber 12 respectively; the non-central optical fiber 12 fanned out by the fan-in and fan-out module 2 is connected to the beam incident angle calculation module 4.

Specifically, the fan-in fan-out module 2, i.e., the multi-core fiber fan-in fan-out module, is a device that realizes efficient coupling of a multi-core fiber with a plurality of fan-out fibers, and realizes the space-division channel demultiplexing function in various applications of the multi-core fiber. The module adopts a taper process, which can realize optical power coupling of low insertion loss, low core crosstalk, and high return loss between the multi-core fiber and a plurality of fan-out fibers. In this embodiment, the fan-in fan-out module 2 adopts a seven-channel structure, and cooperates with the multi-core fiber module 1 to construct the core function of the device, so as to achieve the goal of integrated communication and angle measurement.

The modulation and demodulation module 3 is connected to the central optical fiber 11 fanned out by the fan-in and fan-out module 2, and is used to modulate the local communication laser and transmit it through the central optical fiber 11 when the space laser communication device acts as a transmitting end; when the space laser communication device acts as a receiving end, it demodulates the communication light beam input through the central optical fiber 11.

Specifically, the modulation and demodulation module 3 includes: a signal modulation module 32, a signal demodulation module 33 and a circulator 31, so that the space laser communication device is used to realize full-duplex communication. Among them, the signal modulation module 32 is used to modulate the local communication laser when the space laser communication device is used as a transmitting end, and transmit it through the central optical fiber 11; the signal demodulation module 33 is used to demodulate the communication light beam input through the central optical fiber 11 when the space laser communication device is used as a receiving end; the circulator 31 is used to combine the communication light beam input to the signal demodulation module 33 and the modulated light beam output by the signal modulation module 32 to the central optical fiber, so as to realize full-duplex communication under the same laser link.

Embodiment 2,

A space laser communication system integrating communication and angle measurement, as shown in FIG4 , is composed of two terminal devices, each of which includes a coarse capture detection module, a beam pointing control module, a reflector, a fast reflector, an optical transceiver module, and the space laser communication device described in Example 1. Specifically, the first terminal device 1 includes: a first coarse capture detection module 10, a first beam pointing control module 11, a first optical transceiver module 12, a first multi-core optical fiber module 13, a first optical fiber fan-in fan-out module 14, a first modulation and demodulation module 15, and a first beam incident angle calculation module 16; wherein the first beam pointing control module 11 includes a first reflector 111 and a first fast reflector 112; the first multi-core optical fiber module 13 includes a first communication optical fiber 131 and a first detection optical fiber group 132. The second terminal device 2 includes: a second coarse capture detection module 20, a second light beam pointing control module 21, a second optical transceiver module 22, a second multi-core optical fiber module 23, a second optical fiber fan-in and fan-out module 24, a second modulation and demodulation module 25 and a second light beam incident angle calculation module 16; wherein, the second light beam pointing control module 21 includes a second reflector 211 and a second fast reflector 212; the second multi-core optical fiber module 23 includes a second communication optical fiber 231 and a second detection optical fiber group 232.

The devices at both ends use the coarse capture detection module to initially locate the target, and the modulation and demodulation module is used to transmit and receive the light beam. The transmitted light beam passes through the multi-core fiber module, the optical transceiver module, and then is transmitted to the beam pointing control module through the reflector to point the light beam to the device on the other side. The received light beam passes through the optical transceiver module and enters the multi-core fiber module. The light coupled into the center fiber is received by the laser communication modulation and demodulation module as a communication fiber. The light that is not coupled into the center fiber will be received by the non-center fiber, and the fiber will be split by the multi-core fiber fan-in and fan-out module and then enter the beam incident deviation angle measurement module. The beam pointing is corrected according to the solution results.

Before the device is actually applied, it needs to be calibrated. Through experimental means, find out the area where the ratio of the received power of the detection fiber changes linearly with the incident angle, and record the maximum deviation range of the linear change as the calibration value.

Install the two terminals at two locations or on the mobile objects to be communicated, and turn on the dual-terminal devices. First, the coarse capture detection module locks the position of the opposite target in space, and analyzes the azimuth of the target relative to the aircraft based on the relevant image processing algorithm. According to the obtained azimuth, the beam pointing control module outputs a control signal to operate the large field of view fast transmitting mirror for coarse pointing.

After the coarse pointing process at both ends is completed, the detection fiber of the multi-core fiber module can receive the incident light beam. According to the current received power and the parameters obtained by calibration, the light spot position at the end face of the detection fiber can be calculated. In the calculation process, any two values of _Ka , _Kb , and _Kc need to be solved first. For example, if _Ka and _Kb are known, the position offset of the current light spot on the corresponding axis can be expressed as According to the analytical geometry formula, the x and y axis coordinates corresponding to the current light spot can be obtained, and the coordinates of all points can be obtained from any two directions: Δy ₁ = _Sa , Δy ₂ = _Sa , Δy ₃ = S _b - S _c . The displacement of the light spot in the horizontal and vertical directions is further solved as According to the relationship between the spot position and the incident angle, the deflection angle corresponding to the x and y axes can be calculated. In this way, the compensation angle of the deflection mirror can be solved, and the light beam can be aligned to the center of the communication optical fiber, realizing the integrated function of light beam angle measurement and communication using multi-core optical fiber.

In summary, the present invention discloses an integrated method and device for simultaneously measuring the deviation angle of an incident light beam and performing laser communication in a common optical branch manner using a multi-core optical fiber in a space laser communication scenario, wherein the center position optical fiber of the multi-core optical fiber is used for communication, and the non-center optical fiber is used for measuring the deviation angle of the light beam. The end face of the center optical fiber is located at the focal position of the lens, and the end face of the non-center optical fiber deviates from the focal point by a certain distance. The main feature of the device is that when the light beam is not optimally aligned, the light beam deviation angle is detected by using the optical power irradiated into the non-center fiber core. This device completes the calculation of the light beam pointing deviation while communicating in a common optical branch manner, avoiding the light beam energy loss in a non-common branch manner, and making the device more compact.

It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A space laser communication device integrating communication and angle measurement, characterized in that it comprises: A multi-core optical fiber module, comprising a central optical fiber and M non-central optical fibers uniformly surrounding the central optical fiber, for receiving focused incident light; wherein the end faces of the cores of the non-central optical fibers are in the same plane D and form a circular area with point O as the center; the end face of the central optical fiber and the end face of the non-central optical fiber are parallel to each other and are not located in the same plane, so that the incident light spot covers the position of the central optical fiber and the position of at least one non-central optical fiber; A beam incident angle calculation module, used to obtain an incident angle of the incident light based on radial offsets of the light spots in multiple non-parallel radial directions in the circular area; For any radial direction, the radial offset of the light spot is the offset of the center point of the incident light spot in the radial direction relative to the point O. Based on the characteristic that the power ratio coefficient changes linearly when the incident light moves in the radial direction, the power ratio coefficient in the radial direction acquired in real time is proportionally mapped to obtain the power ratio coefficient; the power ratio coefficient is _Pm and _Pn are the optical powers at two power points in the radial direction; When M is an even number, the power point is the non-central optical fiber center point on the circular area; When M is an odd number, the power point is the non-central optical fiber center point on the circular area and a virtual point symmetrical to the non-central optical fiber center point about point O. 2. The spatial laser communication device according to claim 1, characterized in that the radial offset of the light spot in the i-th radial direction is: Wherein, _Ki is the power ratio coefficient in the i-th radial direction; _{Ki_max} is the maximum value of the power ratio coefficient when the incident light moves in the i-th radial direction; _{Si_max} is the maximum offset of the center point of the light spot relative to point O when the incident light moves in the i-th radial direction. 3. The space laser communication device according to claim 2, characterized in that the light beam incident angle calculation module calculates the incident angle of the incident light using method 1 or method 2; In the method, the light beam incident angle calculation module obtains the position of the incident light spot on the plane D based on the radial offset of the light spot in any two non-parallel radial directions, and then obtains the incident angle of the incident light; In the second method, the light beam incident angle calculation module combines all non-parallel radial directions in pairs, and based on the radial offset of the light spot in the two radial directions under each combination, obtains the position of the incident light spot on the plane D and then calculates the average value as the final position of the incident light spot on the plane D, thereby obtaining the incident angle of the incident light. 4. The spatial laser communication device according to claim 3 is characterized in that a rectangular coordinate system is established with the point O as the origin, the positive direction of the Y axis of the rectangular coordinate system is the radial direction where any power point is located, and the positive direction of the X axis of the rectangular coordinate system is obtained by rotating the positive direction of the Y axis clockwise by 90°; the position of the incident light spot on the plane D is represented by the offset of the center point of the incident light spot on the plane D relative to the point O in the rectangular coordinate system, specifically: Wherein, Δx _ij is the offset of the center point of the incident light spot on plane D relative to point O in the X-axis direction calculated based on the radial offsets of the light spots in the non-parallel i-th radial direction and j-th radial direction; Δy _ij is the offset of the center point of the incident light spot on plane D relative to point O in the Y-axis direction calculated based on the radial offsets of the light spots in the non-parallel i-th radial direction and j-th radial direction; S _i is the radial offset of the light spot in the i-th radial direction; S _j is the radial offset of the light spot in the j-th radial direction; when M is 2N, Q is N; when M is 2N-1, Q is 2N-1; In the above method, the calculation formula of the incident angle of the incident light is: In the second method, the calculation formula of the incident angle of the incident light is: Wherein, _θx is the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the X-axis direction and the axial direction; _θy is the angle between the projection of the incident light beam on the plane formed by the axial direction of the central optical fiber and the Y-axis direction and the axial direction; f is the focal length; and They are respectively the average values of the offsets of the center point of the incident light spot on plane D relative to point O in the X-axis direction and the average values of the offsets in the Y-axis direction, calculated based on the radial offsets of the light spots in two radial directions under each combination. 5. The space laser communication device according to claim 2, characterized in that the light beam incident angle calculation module obtains the incident angle of the incident light based on the angle between the projection of the incident light beam on two planes formed by any two non-parallel radial directions and the axial direction of the central optical fiber and the axial direction; Alternatively, the light beam incident angle calculation module combines all non-parallel radial directions in pairs, and based on the angle between the projections of the incident light beam on two planes formed by the two non-parallel radial directions of the incident light beam in each combination and the axial direction of the central optical fiber and the axial direction, obtains the incident angle of the incident light and then calculates the average value as the final incident angle of the incident light; The angle between the projection of the incident light beam on a plane formed by any radial direction and the axial direction of the central optical fiber and the axial direction is calculated based on the radial offset of the light spot in the radial direction. 6. The spatial laser communication device according to claim 5, characterized in that the angle θ _i between the projection of the incident light beam on the plane formed by the i-th radial direction and the axial direction of the central optical fiber and the axial direction satisfies: Where f is the focal length. 7. The space laser communication device according to any one of claims 1 to 6, characterized in that it further comprises: a lens for focusing the parallel light to obtain the focused incident light and transmit it to the multi-core optical fiber module; The distance from the center of the lens to the central optical fiber end face is the focal length of the lens. 8. The spatial laser communication device according to any one of claims 1 to 6, characterized in that it also includes: a fan-in and fan-out module, used to perform spatial demultiplexing on each core in the multi-core optical fiber module, so that each core is fanned out through M+1 optical fibers, thereby splitting the communication beam and the detection beam output by the multi-core optical fiber module; wherein the communication beam and the detection beam are incident lights coupled into the central optical fiber and the non-central optical fiber, respectively; The non-central optical fiber fanned out by the fan-in and fan-out module is connected to the light beam incident angle calculation module. 9. The space laser communication device according to claim 8, characterized in that it also includes: a modulation and demodulation module; The modulation and demodulation module is connected to the central optical fiber fanned out by the fan-in and fan-out module, and is used to modulate the local communication laser and transmit it through the central optical fiber when the space laser communication device serves as a transmitting end; when the space laser communication device serves as a receiving end, demodulate the communication light beam input through the central optical fiber. 10. The spatial laser communication device according to claim 9, characterized in that it is used to realize full-duplex communication; wherein the modulation and demodulation module comprises: A signal modulation module, used for modulating the local communication laser and transmitting it via the central optical fiber when the space laser communication device is used as a transmitting end; A signal demodulation module, used for demodulating the communication light beam input via the central optical fiber when the space laser communication device is used as a receiving end; The circulator is used to combine the communication light beam input to the signal demodulation module and the modulated light beam output by the signal modulation module into the central optical fiber.