A light-receiving and light-emitting circuit structure for a multi-wavelength satellite laser communication terminal

Abstract

The present invention discloses a light-receiving and light-emitting circuit structure for a multi-wavelength satellite laser communication terminal, including a refractive antenna, a quarter-wave plate, a polarization beam splitter, a post-receiving optical path, and a post-transmitting optical path. The working wavelength sequences of the post-receiving optical path and the post-transmitting optical path are different. The post-receiving optical path and the post-transmitting optical path respectively compensate for the optical focal error caused by the refractive optical antenna for the corresponding working wavelength, so that the terminal light-receiving and light-emitting circuit structure can cover the receiving working wavelength and the transmitting working wavelength of the multi-wavelength laser communication terminal, and can realize the switching of the receiving and transmitting wavelengths in the laser communication terminal as needed. The adoption of this transceiver optical structure form has a simple structure, reduces the number of optical lenses, and has a lower laser absorption coefficient. Compared with the laser communication terminal based on the traditional achromatic refractive antenna, the total volume and total weight of the laser communication terminal are further reduced, and its thermal stability is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite laser communication, and in particular relates to a light transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal. Background Art

[0002] Reflection antennas are widely used in current satellite laser communication systems. This is because reflective antennas have significant advantages in large-aperture situations. Reflection antennas rely on high-precision reflectors (such as parabolic mirrors or aspheric mirrors) to collimate or expand laser beams, which can effectively reduce aberrations and chromatic aberrations, thereby maintaining high beam quality. Compared with refractive antennas, reflective antennas do not cause additional chromatic aberrations due to material dispersion, which is particularly important for multi-wavelength communication systems. These characteristics make reflective antennas the first choice in satellite laser communications, especially in communication tasks that require high precision and long distances.

[0003] With the rapid development of satellite Internet, satellite laser communication terminals are gradually showing a trend of miniaturization. Miniaturized design can reduce the weight and volume of the equipment, thereby reducing launch costs and increasing the deployment flexibility of satellites. Under this trend, refractive antennas show obvious advantages over reflective antennas. Refractive antennas are usually composed of lenses, which are more compact and lightweight, and can effectively reduce the size of the system without sacrificing performance. In addition, the refractive system is easy to manufacture at a small aperture, and because it does not have the problem of central occlusion in the reflector, it can provide higher light energy transmission efficiency. These characteristics make refractive antennas more suitable for satellite laser communication terminals that require lightweight and high efficiency, especially in the communication missions of low-Earth orbit satellites and small satellites, the advantages of refractive antennas are becoming more and more obvious.

[0004] The current mainstream satellite laser communication technology adopts multi-wavelength technology, and its receiving laser signal and transmitting laser signal use different working wavelength sequences. The receiving laser wavelength sequence is a group of similar laser wavelengths (typically 1 to 5 wavelengths, with an adjacent wavelength spacing of 0.4nm), and the transmitting laser wavelength sequence is another group of similar laser wavelengths (typically 1 to 5 wavelengths, with an adjacent wavelength spacing of 0.4nm). There is a large difference between the central wavelength of the receiving wavelength sequence and the central wavelength of the transmitting wavelength sequence, typically 20nm. Due to the large difference in the wavelengths of the receiving and transmitting wavelengths, for this type of satellite laser communication terminal, the refractive antenna faces the problem of achromatic aberration, that is, correcting the dispersion effect generated when light beams of different wavelengths pass through the lens. In order to achieve achromatic aberration, the refractive antenna usually uses a combination of optical lenses with different refractive indices and Abbe numbers. Even if aspherical lenses are used, the refractive antenna still needs no less than 3 lenses. For the case of large beam expansion (>=8×) or short length (length / aperture <1.5), the number of lenses is typically 4 to 5, or even more. More lenses increase the complexity of the optical system, resulting in higher manufacturing costs. In addition, more lenses will introduce additional reflection losses, reducing the transmission efficiency of the optical system.

[0005] On the other hand, the thermal problem of the refractive antenna is an important factor affecting its performance. As the ambient temperature changes, the refractive index of the lens material changes, and the parameters such as the thickness and curvature radius of the lens change with its thermal expansion. The absorption and heat of the optical lens to the emitted laser beam can also cause the optical element to produce material refractive index changes and local shape changes. The above factors all lead to the displacement of the focus position of the beam, affecting the collimation and transmission efficiency of the system. Under poor temperature conditions, there is often a large temperature gradient, that is, there is a temperature difference between the various parts of the optical-mechanical system. In addition to causing the focus of the optical system to change along the optical axis, this situation will also cause additional changes in the direction of the optical axis, as well as other spherical aberrations, astigmatism and other thermal aberrations caused by thermal factors. In the design process of the refractive antenna, in order to effectively correct the chromatic aberration and select targeted optical glass materials, it is often difficult to fully take into account factors such as its light absorption coefficient, thermal expansion coefficient and refractive index temperature coefficient, which makes the refractive antenna have a problem of optical performance degradation when the temperature level changes or there is a temperature gradient. This is particularly evident in harsh space temperature environments such as satellite laser communications. Therefore, in high-power laser communication systems or space environments, the thermal problem of achromatic refractive antennas becomes a major challenge.

[0006] In summary, for miniaturized satellite laser communication terminals, especially high-transmitting-power systems, reducing size and weight, achieving chromatic aberration correction of the transmitting and receiving wavelengths, and improving thermal stability are key considerations in the design of their optical paths. Refractive antennas are suitable for this lightweight requirement due to their compact structure, and have significant advantages in miniaturized design and reduced transmission costs. When used in multi-wavelength communication systems, refractive optical systems need to correct chromatic aberration through multiple lenses, which increases the complexity and weight of the system. The thermal effect of high-power lasers can cause thermal expansion of the lens material, affecting the optical performance, especially in achromatic materials, where thermal stability is poor. Therefore, the design needs to balance lightweight, chromatic aberration correction, and thermal stability to ensure efficient operation of the system in a complex space environment. Summary of the invention

[0007] The present invention is aimed at the refractive optical system in the multi-wavelength laser communication terminal, and proposes a light-receiving and light-emitting circuit structure for a multi-wavelength satellite laser communication terminal. The refractive antenna is composed of two optical lenses. The optical focal error caused by the refractive optical antenna is compensated for the corresponding working wavelengths in the post-receiving optical path and the post-transmitting optical path, respectively, so that the terminal light-receiving and light-emitting circuit structure can cover the receiving working wavelength and the transmitting working wavelength of the multi-wavelength laser communication terminal, and the receiving and transmitting wavelength switching in the laser communication terminal can be realized as needed. The adoption of this transceiver optical structure form has a simple structure, reduces the number of optical lenses, and has a lower laser absorption coefficient. Compared with the laser communication terminal based on the traditional achromatic refractive antenna, the total volume and total weight of the laser communication terminal are further reduced, and its thermal stability is greatly improved. It is applied to miniaturized satellite laser communication systems, especially high-transmitting-power satellite laser communication systems, and has significant technical advantages.

[0008] The above purpose is achieved through the following technical solutions:

[0009] The present invention discloses a light-receiving and light-emitting path structure for a multi-wavelength satellite laser communication terminal, comprising a refractive antenna, a quarter-wave plate, a polarization beam splitter, a post-receiving light path and a post-transmitting light path, wherein the refractive antenna is composed of a positive lens lens, a negative lens lens and a refractive antenna lens barrel, and the refractive antenna lens barrel is used to connect the positive lens lens and the negative lens lens; the post-receiving light path comprises a receiving light path optical focal compensation lens, a receiving lens and a receiving detector; the post-transmitting light path comprises a transmitting light path optical focal compensation lens, a transmitting lens and a transmitting light source;

[0010] Among them, there are differences in the working wavelength sequences of the post-receiving optical path and the post-transmitting optical path. The central wavelength of the working wavelength sequence of the post-receiving optical path is recorded as , the central wavelength of the working wavelength sequence of the optical path after emission is recorded as ;

[0011] The beam expansion ratio of the refractive antenna is , there is chromatic aberration for the working wavelength of the refractive antenna. Assuming that No defocus, meet the conditions: ,or ; The positive lens and negative lens that make up the refractive antenna have refractive index functions of and , positive lens and negative lens for wavelength The optical focal lengths are and , the following relationship needs to be satisfied: The optical materials of the positive lens and the negative lens also need to satisfy the athermal relationship as shown in formula (1):

[0012] CTE m * F 1 +F 2 F 1 F 2 = CTE 1 F 1 - 1 F 1 [ n 1 l ref ,T -1] ∂ n 1 l ref ,T ∂T + CTE 2 F 2 - 1 F 2 [ n 2 l ref ,T -1] ∂ n 2 l ref ,T ∂T (1)

[0013] Where T is the reference temperature of the environment where the optical system is located. is the thermal expansion coefficient of the glass material of the positive lens, is the thermal expansion coefficient of the glass material of the negative lens, is the thermal expansion coefficient of the refractive antenna barrel;

[0014] The optical power of the receiving optical path is compensated by the optical power of the lens , it is necessary to compensate for the wavelength of the refractive antenna The residual power of the lower optic satisfies the following relationship as shown in formula (2):

[0015] (2);

[0016] The focal length of the emission light path is adjusted to compensate for the focal length of the lens. , it is necessary to compensate for the wavelength of the refractive antenna The residual power of the lower optic satisfies the following relationship as shown in formula (3):

[0017] (3).

[0018] Furthermore, when the refractive antenna is designed, the wavelength without defocusing Meet the following conditions:

[0019] like = ,but , remove the focal compensation lens of the receiving light path;

[0020] like = ,but , remove the optical power compensation lens in the emission light path.

[0021] Furthermore, the refractive index and thermal expansion coefficient of the lens materials of the positive lens and the negative lens in the refractive antenna meet the following conditions:

[0022] ∂ n 1 l ref , T ∂ T + CTE 1 *[ n 1 l ref , T -1]=0 ;

[0023] ∂ n 2 l ref , T ∂ T + CTE 2 *[ n 2 l ref , T -1]=0 .

[0024] Furthermore, the optical power compensation lens of the receiving light path adopts a filter with optical power, one side of which contains a narrow-band filter film; one side or both sides of the filter with optical power have a curvature, and its optical power satisfies the condition of formula (3).

[0025] Furthermore, the transmitting and receiving wavelength structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength , specifically:

[0026] 1) The quarter wave plate can be switched between two states: 45 degrees and 135 degrees in the fast axis direction. These two states are achieved by replacing two different quarter wave plates with a mechanical structure; or by rotating the same quarter wave plate with a mechanical structure;

[0027] 2) The receiving optical path focal compensation lens can have a focal power of and The two states are switched, and accordingly, the optical focal length compensation lens of the emission light path is and The two states are switched, and the switching method is achieved by including two compensation lenses with different optical focal lengths in the receiving optical path and the transmitting optical path respectively, and switching through a mechanical structure; or by exchanging the optical focal length compensation lens of the receiving optical path and the optical focal length compensation lens of the transmitting optical path through a mechanical structure;

[0028] 3) Simultaneously, the operating modes of the transmitting light source and the receiving detector are switched accordingly.

[0029] Furthermore, the transmitting and receiving wavelength structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength , specifically:

[0030] 1) adding a half-wave plate between the quarter-wave plate and the polarization beam splitter, wherein the fast axis direction of the half-wave plate is consistent with that of the quarter-wave plate;

[0031] 2) No-defocus wavelength of refractive antenna = , , the receiving optical path and the transmitting optical path share the same optical power compensation lens, and its optical power is ;

[0032] 3) The half-wave plate and the optical focal compensation lens are installed on a rotating mechanism, and the rotating mechanism is used to change the optical path when the transmitting and receiving wavelengths are switched. Before the transmitting and receiving wavelengths are switched, the half-wave plate is located in the optical path, between the quarter-wave plate and the polarization beam splitter, and the optical focal compensation lens is located in the optical path after receiving; after the transmitting and receiving wavelengths are switched, that is, When the half-wave plate cuts out the light path, the focal length compensation lens is located in the light path after emission.

[0033] Furthermore, the transmitting and receiving wavelength structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength , specifically:

[0034] The half-wave plate, the filter without optical power and the filter with optical power are mounted on the rotating mechanism. The fast axis direction of the half-wave plate is consistent with that of the quarter-wave plate. The optical power of the filter without optical power is zero, and the wavelength that can be transmitted is , the focal length of the optical power filter is , the transmittance wavelength ,The rotating mechanism is used to change the optical path when switching the transmitting and receiving wavelengths;

[0035] Before the wavelength switching between transmitting and receiving, the half-wave plate is located in the optical path, between the quarter-wave plate and the polarization beam splitter, the optical power filter is located outside the optical path and does not work, and the optical power filter is located in the optical path after receiving;

[0036] After the transmit and receive wavelengths are switched, When , the half-wave plate is cut out of the optical path and does not work; the optical power filter is located in the optical path after receiving, and the optical power filter is switched to the optical path after transmitting.

[0037] The present invention is aimed at the refractive optical system in the multi-wavelength laser communication terminal, especially for miniaturized satellite laser communication systems and high-transmitting-power satellite laser communication systems, and proposes a light-receiving and light-emitting circuit structure for a multi-wavelength satellite laser communication terminal, wherein the chromatic aberration generated by the light path after receiving and the light path after transmitting are compensated respectively. The light-receiving and light-emitting circuit structure can also switch the wavelength of receiving and transmitting by switching the light path after transmitting. Its beneficial effects include the following aspects:

[0038] 1. Simple structure, reducing the number of optical lenses, reducing the size and weight of the laser communication terminal, and reducing the launch cost;

[0039] 2. Reduce the number of optical lenses and improve the transmittance of the optical system;

[0040] 3. Compared with the achromatic refractive antenna, the refractive antenna of the present invention has more freedom in material selection, and can more comprehensively take into account the optical glass material's resistance to space environment radiation, laser absorption coefficient, stability to temperature changes, and stability to temperature gradients, thereby improving the performance and stability of the laser communication terminal in many aspects;

[0041] 4. It can make full use of polarization transceiver isolation and wavelength transceiver isolation, so that the system can obtain good isolation, which can be applied to ultra-long distance laser communication and high transmission power laser communication;

[0042] 5. The transmitting and receiving wavelengths can be switched through as few as one mechanical motion link, which is conducive to the interconnection between satellite laser communication terminals. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the light-receiving and light-emitting circuit structure of the present invention;

[0044] Figure 2 It is a schematic diagram of the structure of a filter with optical power used in the post-receiving optical path described in Example 4;

[0045] Figure 3 It is a structural form in which the light-transmitting and light-receiving circuit structure described in Example 5 realizes the switching of the light-transmitting and light-receiving wavelengths;

[0046] Figure 4 is a schematic structural diagram of the transmitting and receiving wavelength switching solution described in Example 6 before rotation switching;

[0047] Figure 5 is a schematic structural diagram of the receiving and transmitting wavelength switching solution after rotation switching described in Example 6;

[0048] Figure 6 is a schematic structural diagram of the receiving and transmitting wavelength switching solution with a filter function described in Example 7 before rotation switching;

[0049] Figure 7 is a schematic structural diagram of the receiving and transmitting wavelength switching solution with a filter function described in Example 7 after rotation switching;

[0050] Description of each component in the figure: 1. Refractive antenna; 101. Positive lens; 102. Negative lens; 103. Refractive antenna barrel; 2. Quarter wave plate; 3. Polarization beam splitter; 4. Receiving optical path; 401. Receiving optical path optical focality compensation lens; 402. Receiving lens; 403. Receiving detector; 404. Optical filter with optical focality; 5. Receiving optical path; 501. Optical focality compensation lens for transmitting optical path; 502. Transmitting lens; 503. Transmitting light source; 6. Half wave plate; 7. Optical focality compensation lens; 8. Rotating mechanism; 9. Optical filter without optical focality; 10. Optical filter with optical focality. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0052] Embodiment 1:

[0053] like Figure 1 As shown, the light-receiving and light-emitting path structure for a multi-wavelength satellite laser communication terminal in this embodiment is composed of a refractive antenna 1, a quarter-wave plate 2, a polarization beam splitter 3, a post-receiving optical path 4, and a post-transmitting optical path 5. The refractive antenna 1 is composed of a positive lens 101, a negative lens 102, and a refractive antenna lens barrel 103, and the refractive antenna lens barrel 103 is used to connect the positive lens 101 and the negative lens 102; the post-receiving optical path 4 is composed of a receiving optical path focal compensation lens 401, a receiving lens 402, and a receiving detector 403; the post-transmitting optical path 5 is composed of a transmitting optical path focal compensation lens 501, a transmitting lens 502, and a transmitting light source 503.

[0054] There are differences in the working wavelength sequences of the post-receiving optical path 4 and the post-transmitting optical path 5, which are used to improve the transmit-receive isolation by the difference in different wavelengths during communication, that is, to reduce the interference of the back reflection and back scattering of the transmitting light beam on the receiving optical path; for the convenience of expression, the central wavelength of the working wavelength sequence of the receiving optical path is recorded as , the central wavelength of the working wavelength sequence of the emission light path is recorded as .

[0055] Let the beam expansion ratio of the refractive antenna 1 be , there is a chromatic aberration in its working wavelength. Assuming that its wavelength No defocus, meet the conditions: ,or The positive lens 101 and the negative lens 102 constituting the refractive antenna 1 have refractive index functions of and The refractive index function is a characteristic of the material itself. Optical material manufacturers (such as Chengdu Guangming) will provide the specific relationship of the refractive index function when they leave the factory. The optical focal lengths are and , satisfying or approximately satisfying the following relationship: In order to ensure that the optical power of the optical system remains basically unchanged when the temperature changes, the optical materials of the two lenses selected need to satisfy or approximately satisfy the athermal relationship as shown in formula (1):

[0056] CTE m * F 1 +F 2 F 1 F 2 = CTE 1 F 1 - 1 F 1 [ n 1 l ref , T -1] ∂ n 1 l ref , T ∂ T + CTE 2 F 2 - 1 F 2 [ n 2 l ref , T -1] ∂ n 2 l ref , T ∂ T (1)

[0057] Where T is the reference temperature of the environment where the optical system is located. is the thermal expansion coefficient of the glass material of the positive lens element 101, is the thermal expansion coefficient of the glass material of the negative lens element 102, is the thermal expansion coefficient of the refractive antenna barrel 103.

[0058] Among them, the focal length of the receiving optical path optical focal length compensation lens 401 , it is necessary to compensate the wavelength of the refractive antenna 1 The residual power of the lower optic satisfies or approximately satisfies the following relationship as shown in formula (2):

[0059] (2);

[0060] Among them, the focal length of the emission light path compensation lens 501 is , it is necessary to compensate the wavelength of the refractive antenna 1 The lower optical power residual satisfies or approximately satisfies the following relationship as shown in formula (3):

[0061] (3).

[0062] The optical system works in the following way:

[0063] (1) The refractive antenna 1 contracts the received laser beam and expands the transmitted laser beam. Since the refractive antenna is not achromatic, the working wavelength of the received laser beam is affected during the contraction and expansion process. Additional optical power is generated for the working wavelength of the emitted laser beam Generates additional optical power.

[0064] (2) In the receiving optical path, the circularly polarized laser beam received by the terminal is focused by the refractive antenna 1, carries additional optical focal length, is converted into a linearly polarized beam by the quarter-wave plate 2, and is transmitted by the polarization beam splitter 3 to enter the receiving optical path 4, wherein the optical focal length compensation lens 401 of the receiving optical path has an effect on the wavelength of the refractive antenna 1. The additional optical power under the condition is compensated, and then converged by the receiving lens 402, and detected by the receiving detector 403;

[0065] (3) In the transmitting optical path, the linearly polarized light beam from the transmitting light source 503 in the post-transmitting optical path 5 is collimated by the transmitting lens 502, and then pre-compensated by the transmitting optical path optical focal length compensation lens 501, carrying a certain optical focal length. The transmitting light beam is then reflected by the polarization beam splitter 3, converted into circularly polarized light by the quarter-wave plate 2, and then expanded by the refractive antenna 1. The additional optical focal length of the refractive antenna 1 is offset by the compensated optical focal length, forming a collimated circularly polarized laser beam with a larger aperture, which is emitted to the laser communication terminal on the other side.

[0066] Embodiment 2:

[0067] The difference between this embodiment and embodiment 1 is that the non-defocused wavelength in the design of the refractive antenna 1 is = ,but , in this special case, the optical focal length compensation lens 401 of the receiving light path is removed.

[0068] Embodiment 3:

[0069] The difference between this embodiment and embodiment 1 is that the non-defocused wavelength in the design of the refractive antenna 1 is = ,but In this special case, the emission light path optical focal length compensation lens 501 is removed.

[0070] Embodiment 4:

[0071] The difference between this embodiment and embodiment 1 is that a plane reflector is added at an appropriate position to fold the optical path as needed (such as miniaturization); the optical path structure can be modified so that the post-receiving optical path 4 is located at the reflection arm of the polarization beam splitter 3, and the post-transmitting optical path 5 is located on the transmission side of the polarization beam splitter 3; filters and polarizers can be added to the post-receiving optical path 4 and the post-transmitting optical path 5 as needed to further improve their performance, such as improving the transmit and receive isolation; a precision aiming mirror can be added at an appropriate position between the refractive antenna 1 and the polarization beam splitter 3 to improve the aiming and tracking performance in the laser communication terminal; an advance aiming mirror can be added to the post-transmitting optical path 5 as needed to be suitable for application scenarios with a large relative speed between the transmitting and receiving terminals, or to correct the transmitting and receiving coaxial errors of the receiving and transmitting optical path structure.

[0072] In this embodiment, the refractive index and thermal expansion coefficient of the lens materials of the positive lens 101 and the negative lens 102 of the refractive antenna 1 meet or approximately meet the following conditions:

[0073] ∂ n 1 l ref , T ∂ T + CTE 1 *[ n 1 l ref , T -1]=0 ;

[0074] ∂ n 2 l ref , T ∂ T + CTE 2 *[ n 2 l ref , T -1]=0 ;

[0075] This can reduce the optical axis drift and thermal aberration introduced by the optical system when there is a thermal gradient.

[0076] like Figure 2 As shown, in the post-receiving optical path 4 of this embodiment, a filter 404 with optical power can be used to realize the functions of the filter and the optical power compensation lens of the receiving optical path at the same time; the filter 404 with optical power has a narrow-band filter film on one side; one or both sides have a curvature, and its optical power satisfies the formula (2) Same conditions.

[0077] Embodiment 5:

[0078] The difference between this embodiment and embodiment 1 is that, in order to better realize the interconnection between satellite laser communication terminals, the light-transmitting and light-emitting circuit structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength ,like Figure 3 As shown, it includes the following aspects:

[0079] 1) The quarter wave plate 2 can be switched between two states, where the fast axis directions of the two states are 45 degrees and 135 degrees respectively. The two states are achieved by replacing two different quarter wave plates with a mechanical structure, or by rotating the same quarter wave plate with a mechanical structure;

[0080] 2) The receiving optical path focal compensation lens 401 can be switched between two states, and the focal lengths of the two states are respectively and The emission light path focal compensation lens 501 can be switched into two states, and the focal lengths of the two states are respectively and The switching between the two states of the receiving optical path focal length compensation lens 401 and the transmitting optical path focal length compensation lens 501 can be achieved by having two lenses with different focal lengths in the receiving optical path 4 and the transmitting optical path 5, respectively, and by switching the mechanical structure, or by exchanging the receiving optical path focal length compensation lens 401 and the transmitting optical path focal length compensation lens 501 by the mechanical structure;

[0081] 3) Simultaneously, the operating modes of the transmitting light source and the receiving detector are switched accordingly.

[0082] Embodiment 6:

[0083] The difference between this embodiment and embodiment 1 is that only the transmitting and receiving wavelengths of a single mechanical motion link are switched, that is, switched to the receiving wavelength , which is implemented as follows:

[0084] 1) adding a half-wave plate 6 between the quarter-wave plate 2 and the polarization beam splitter 3, wherein the fast axis direction of the half-wave plate 6 is consistent with that of the quarter-wave plate 2;

[0085] 2) No-defocus wavelength of refractive antenna 1 = , , the receiving optical path 4 and the transmitting optical path 5 share the same optical power compensation lens 7, and the optical power of the optical power compensation lens 7 is ;

[0086] 3) The half-wave plate 6 and the optical power compensation lens 7 are mounted on a rotating mechanism 8, which is used to change the optical path when the transmitting and receiving wavelengths are switched. Before the transmitting and receiving wavelengths are switched, the half-wave plate 6 is located in the optical path, between the quarter-wave plate 2 and the polarization beam splitter 3, and the optical power compensation lens 7 is located in the optical path 4 after receiving. Figure 4 As shown;

[0087] After the transmit and receive wavelengths are switched ( ), the half-wave plate 6 cuts out the optical path, and the focal compensation lens 7 is located in the optical path 5 after emission, as shown in FIG. Figure 5 shown.

[0088] Embodiment 7:

[0089] The difference between this embodiment and embodiment 1 is that only the receiving and transmitting wavelengths of a single mechanical motion link are switched. In order to add a filter function in the receiving optical path, the following method is adopted: a half-wave plate 6, a lightless focal filter 9 and a light-containing focal filter 10 are installed on a rotating mechanism 8, wherein the fast axis direction of the half-wave plate 6 is consistent with that of the quarter-wave plate 2, the optical focal power of the lightless focal filter 9 is zero, and the wavelength can be transmitted. , the focal length of the focal length filter 10 is , the transmittance wavelength The rotating mechanism 8 is used to change the optical path when the transmitting and receiving wavelengths are switched. Before the transmitting and receiving wavelengths are switched, the half-wave plate 6 is located in the optical path, between the quarter-wave plate 2 and the polarization beam splitter 3, the optical power filter 9 is located outside the optical path and does not work, and the optical power filter 10 is located in the optical path 4 after receiving, referring to Figure 6 After the transmit and receive wavelengths are switched ( ), the half-wave plate 6 is cut out of the optical path and does not work, the optical power filter 9 is located in the optical path 4 after receiving, and the optical power filter 10 is switched to the optical path 5 after transmitting, refer to Figure 7 .

[0090] Embodiment 8:

[0091] In order to realize a Φ55mm aperture satellite laser communication terminal for a certain project, in order to compress its length as much as possible and obtain good thermal stability, the key technical details of the light-receiving and light-emitting circuit structure designed in this embodiment are as follows:

[0092] The high refractive index material H-ZLAF96 (glass brand of Chengdu Guangming, China) was selected, and the titanium alloy with CTE of 8.2ppm / K was used as the structural material to achieve heat elimination;

[0093] The emission wavelength of the laser communication terminal is 1540.5nm, and the receiving wavelength is 1563.0nm; the refractive antenna has no defocus at 1540.5nm;

[0094] The refractive antenna is composed of two optical lenses. The center thickness of the positive lens is 11mm, the center thickness of the negative lens is 2mm, and the center distance between the two is 36mm. The total length of the refractive antenna is 50mm, and its length divided by the diameter is approximately 0.91;

[0095] The positive lens in the refractive antenna is a meniscus lens. The first surface is a convex spherical surface with a curvature radius of 34.515 mm. The second surface is a concave high-order aspherical surface with a vertex curvature radius of R=82.767 and a Conic coefficient of k=0. The vector height equation of the aspherical surface is:

[0096] ,

[0097] Where c is the vertex curvature, c=1 / R; r represents the position on the optical surface, the distance from the optical axis; the coefficient of the aspheric high-order term is:

[0098] α1=0,

[0099] α2=1.210018946644955E-006,

[0100] α3=1.751460401975980E-010,

[0101] α4=1.751460401975980E-010,

[0102] α5=6.350140681514549E-016,

[0103] α6=-1.063206176806826E-018,

[0104] α7=9.513398972967811E-022,

[0105] α8=-3.445449214806808E-025;

[0106] The negative lens in the refractive antenna is a double concave lens, the first surface is a concave spherical surface with a curvature radius of -20.203mm, and the second surface is a concave spherical surface with a curvature radius of 14.251mm;

[0107] No optical power compensation lens is required in the transmitting optical path. The focal length of the optical power compensation lens in the receiving optical path is 2632.64 mm. Its thickness is 2 mm. It is a plano-convex lens made of fused quartz. The first surface is convex with a curvature radius of 1169.713 and the second surface is flat.

[0108] The terminal's receiving and transmitting wavelengths are switched by rotating the half-wave plate and the optical focal compensation lens. Before switching, the emission wavelength is 1540.5nm, the receiving wavelength is 1563nm, the optical focal compensation lens is located in the receiving optical path, and the half-wave plate is located in the optical path (between the half-wave plate and the polarization beam splitter); after switching, the emission wavelength becomes 1563nm, and the receiving wavelength is 1540.5nm. By rotating the rotating mechanism, the optical focal compensation lens moves into the emission optical path, and the half-wave plate moves out of the optical path.

Claims

1. A light-transmitting and light-receiving path structure for a multi-wavelength satellite laser communication terminal, comprising a refractive antenna (1), a quarter-wave plate (2), a polarization beam splitter (3), a post-receiving light path (4) and a post-transmitting light path (5), characterized in that: The refractive antenna (1) is composed of a positive lens (101), a negative lens (102) and a refractive antenna lens barrel (103), wherein the refractive antenna lens barrel (103) is used to connect the positive lens (101) and the negative lens (102); the receiving rear optical path (4) comprises a receiving optical path focal length compensation lens (401), a receiving lens (402) and a receiving detector (403); the transmitting rear optical path (5) comprises a transmitting optical path focal length compensation lens (501), a transmitting lens (502) and a transmitting light source (503); There is a difference between the working wavelength sequences of the post-receiving optical path (4) and the post-transmitting optical path (5). The central wavelength of the working wavelength sequence of the post-receiving optical path (4) is recorded as , the central wavelength of the working wavelength sequence of the optical path (5) after emission is recorded as ; The beam expansion ratio of the refractive antenna (1) is , there is chromatic aberration in the working wavelength of the refractive antenna (1), assuming that its wavelength No defocus, meet the conditions: ,or The positive lens (101) and the negative lens (102) constituting the refractive antenna (1) have refractive index functions of: and ,in , the positive lens (101) and the negative lens (102) have a wavelength The optical focal lengths are and , the following relationship needs to be satisfied: The optical materials of the positive lens (101) and the negative lens (102) also need to satisfy the athermal difference relationship as shown in formula (1): （1） Where T is the reference temperature of the environment where the optical system is located. is the thermal expansion coefficient of the glass material of the positive lens element (101), is the thermal expansion coefficient of the glass material of the negative lens element (102), is the thermal expansion coefficient of the refractive antenna lens barrel (103); The focal length of the receiving light path focal length compensation lens (401) is set to , it is necessary to compensate for the refractive antenna (1) at wavelength The residual power of the lower optic satisfies the following relationship as shown in formula (2): （2）； The focal length of the emission light path focal length compensation lens (501) is , it is necessary to compensate for the refractive antenna (1) at wavelength The residual power of the lower optic satisfies the following relationship as shown in formula (3): （3）。 2. The light-transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal according to claim 1, characterized in that: No defocus wavelength when the refractive antenna (1) is designed Meet the following conditions: like = ,but , removing the focal compensation lens (401) of the receiving light path; like = ,but , remove the optical power compensation lens (501) in the emission light path.

3. The light-transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal according to claim 1, characterized in that: The refractive index and thermal expansion coefficient of the lens materials of the positive lens (101) and the negative lens (102) in the refractive antenna (1) satisfy the following conditions: ； 。 4. The light transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal according to claim 1, characterized in that: The receiving light path optical focal compensation lens adopts an optical filter with optical focal length, one side of which contains a narrow-band filter film; one side or both sides of the optical filter with optical focal length have a curvature, and its optical focal length satisfies the condition of formula (3).

5. The light transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal according to claim 1, characterized in that: The transmitting and receiving wavelength structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength , specifically: 1) The quarter wave plate can be switched between two states: 45 degrees and 135 degrees in the fast axis direction. These two states are achieved by replacing two different quarter wave plates with a mechanical structure; or by rotating the same quarter wave plate with a mechanical structure; 2) The receiving light path focal compensation lens (401) can have a focal length of and The two states are switched, and accordingly, the emission light path focal length compensation lens (501) is in a state of focal length of and The two states are switched, and the switching is achieved by including two compensation lenses with different optical focal lengths in the receiving optical path (4) and the transmitting optical path (5), respectively, and switching is achieved through a mechanical structure; or by exchanging the optical focal length compensation lens (401) of the receiving optical path and the optical focal length compensation lens (501) of the transmitting optical path through a mechanical structure; 3) Simultaneously, the operating modes of the transmitting light source (503) and the receiving detector (403) are switched accordingly.

6. The light transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal according to claim 1, characterized in that: The transmitting and receiving wavelength structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength , specifically: 1) adding a half-wave plate (6) between the quarter-wave plate (2) and the polarization beam splitter (3), wherein the fast axis direction of the half-wave plate (6) is consistent with that of the quarter-wave plate; 2) The non-defocused wavelength of the refractive antenna (1) = , , the receiving optical path (4) and the transmitting optical path (5) share the same optical power compensation lens (7), whose optical power is ; 3) The half-wave plate (6) and the optical focal length compensation lens (7) are mounted on a rotating mechanism (8), and the rotating mechanism (8) is used to change the optical path when the transmitting and receiving wavelengths are switched. Before the transmitting and receiving wavelengths are switched, the half-wave plate (6) is located in the optical path, between the quarter-wave plate (2) and the polarization beam splitter (3), and the optical focal length compensation lens (7) is located in the post-receiving optical path (4); after the transmitting and receiving wavelengths are switched, that is, When the half-wave plate (6) cuts out the optical path, the focal compensation lens (7) is located in the optical path (5) after emission.

7. The light transmitting and receiving circuit structure for a multi-wavelength satellite laser communication terminal according to claim 1, characterized in that: The transmitting and receiving wavelength structure adopts the following method to realize the switching of the transmitting and receiving wavelengths, that is, switching to the receiving wavelength , specifically: The half-wave plate (6), the optical power filter (9) and the optical power filter (10) are mounted on the rotating mechanism (8), wherein the fast axis direction of the half-wave plate (6) is consistent with that of the quarter-wave plate (2), the optical power of the optical power filter (9) is zero, and the wavelength of light that can be transmitted is , the focal power of the focal power filter (10) is , the transmittance wavelength , the rotating mechanism (8) is used to change the optical path when switching the transmitting and receiving wavelengths; Before the transmitting and receiving wavelengths are switched, the half-wave plate (6) is located in the optical path, between the quarter-wave plate (2) and the polarization beam splitter (3), the optical power filter (9) is located outside the optical path and does not work, and the optical power filter (10) is located in the optical path (4) after receiving; After the transmit and receive wavelengths are switched, When the half-wave plate (6) is switched out of the optical path, it does not work; the optical power filter (9) is located in the post-receiving optical path (4), and the optical power filter (10) is switched to the post-transmitting optical path (5).

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