Space laser communication system with multi-standard transmission

Abstract

The present invention relates to a space laser communication system for multi-standard transmission, including a laser transmitter, a polarization beam splitter, a coarse pointing mechanism, a wavelength beam splitter, and an energy beam splitter; after the optical signal is emitted by the laser transmitter, it is reflected by the polarization beam splitter to the coarse pointing mechanism for deflection and transmission; after the optical signal is received by the coarse pointing mechanism, it is transmitted to the wavelength beam splitter through the polarization beam splitter, a part of it is transmitted to the coherent detection module through the wavelength beam splitter, another part is reflected to the energy beam splitter through the wavelength beam splitter, and a part is transmitted to the incoherent detection tracking module through the energy beam splitter, and another part is reflected to the incoherent detection communication module through the energy beam splitter. The present invention supports simultaneous transmission of multi-standard and multi-protocol laser intersatellite links, supports coherent and incoherent laser information transmission, can solve the problem of cross-constellation link establishment under different satellite systems and different systems, and realizes the interconnection and interoperability of heterogeneous constellations.

Description

Technical Field

[0001] The present invention relates to the field of communications, and in particular to a multi-standard transmission space laser communication system. Background Art

[0002] Currently, the deployment and construction of high, medium and low orbit communication constellations and remote sensing constellations are gradually underway. Most of them plan to deploy laser inter-satellite link networks. However, due to the construction needs of each satellite system itself, there are different standards (different modulation methods and detection methods) of communication systems and speed requirements, resulting in different communication systems and transmission protocols between constellations unable to communicate with the Internet.

[0003] With the development of on-orbit verification of laser communication terminals, the current systems of satellite-borne laser communication terminals are mainly OOK modulation / incoherent detection and BPSK modulation / coherent detection. The BPSK modulation method can also be upgraded to QPSK to meet the needs of users for higher information transmission rates. In addition, due to the need for miniaturization of on-board laser communication payloads, the same-band, beacon-free optical tracking system has become the main choice for optical carrier frequency and tracking system of space laser communication. However, there are still some problems in the existing technology:

[0004] Chinese patent CN106533562A discloses a space multi-user multi-standard satellite laser communication system and method, including a multi-carrier generation subsystem, a multi-standard modulation matching subsystem, and an optical phased array antenna subsystem connected in sequence, wherein the multi-carrier generation subsystem includes a condenser, a pump cavity, and a polarization beam splitter, wherein the pump cavity is located between the condenser and the polarization beam splitter, the multi-standard modulation matching subsystem includes between the modulator array and the wavelength division multiplexer, and the optical phased array antenna subsystem includes a fine aiming deflection control mirror and a coarse aiming deflection control mirror, wherein the coarse aiming deflection control mirror is located on the side of the fine aiming deflection control mirror. The problem is that the laser communication terminal is generally a full-duplex communication system, and the disclosure only describes the transmission mode of the multi-standard laser communication system, and does not explain the multi-standard simultaneous receiving method, and the optical phased array antenna subsystem used in the invention cannot meet the space application requirements in the short term.

[0005] Chinese patent CN109039462B discloses a multi-modulation format compatible high-speed laser signal non-phase-locked receiving system and method, which can greatly improve the compatibility of communication formats at the relay nodes of the existing laser communication network, and save the price and resource cost of system performance upgrade. It includes a control instruction unit, a low-noise high-gain optical amplifier, an optical switch, a filter, an optical delay interferometer I, and an optical interferometer Q connected to a first balanced detector and a second balanced detector; the first balanced detector and the second balanced detector output electrical signals in turn through a reverse coding switch unit, a parallel-to-serial conversion unit, and a data processing unit. The problem is that it only describes a multi-modulation format compatible receiving system and method, and does not describe the design method and principle of a multi-standard compatible optical system in a laser communication terminal.

[0006] In summary, the current laser transmitter cannot achieve simultaneous modulation of multiple optical carriers, and can only be applied to the switching of OOK, BPSK and QPSK modulation formats of a single optical carrier, which cannot meet the requirements of simultaneous modulation transmission of multiple standards. In the same band without beacon optical tracking system, there is no design and implementation method for the optical channel of laser communication system to meet the requirements of simultaneous transmission and reception of multiple optical carriers. Summary of the invention

[0007] The embodiment of the present invention aims to provide a multi-standard transmission space laser communication system to solve the problem that laser signals of different standards cannot be transmitted simultaneously.

[0008] An embodiment of the present invention provides a multi-standard transmission space laser communication system, the system comprising a laser transmitter, a polarization beam splitter, a coarse pointing mechanism, a wavelength beam splitter, and an energy beam splitter; after the optical signal is emitted by the laser transmitter, it is reflected by the polarization beam splitter to the coarse pointing mechanism for deflection and transmission; after the optical signal is received by the coarse pointing mechanism, it is transmitted to the wavelength beam splitter through the polarization beam splitter, a part of the optical signal is transmitted to a coherent detection module through the wavelength beam splitter, another part is reflected to the energy beam splitter through the wavelength beam splitter, and a part is transmitted to an incoherent detection tracking module through the energy beam splitter, and another part is reflected to an incoherent detection communication module through the energy beam splitter.

[0009] In any embodiment, the laser transmitter includes an IQ modulator and an intensity modulator connected in parallel.

[0010] In either embodiment, the laser transmitter can modulate and switch OOK, BPSK / QPSK signals simultaneously.

[0011] In any embodiment, the space laser communication system further comprises an optical amplifier and a signal transmission module located between the laser transmitter and the polarization beam splitter, wherein the signal transmission module comprises a collimator.

[0012] In any embodiment, the space laser communication system further includes a first fast reflection mirror located between the signal transmission module and the polarization beam splitter.

[0013] In any embodiment, the space laser communication system further includes a telescope disposed between the polarization beam splitter and the coarse pointing mechanism.

[0014] In any embodiment, a quarter wave plate is provided between the telescope and the polarization beam splitter.

[0015] In any embodiment, a second fast-reflecting mirror is disposed between the telescope and the polarization beam splitter.

[0016] In any embodiment, a bandpass filter is provided between the polarization beam splitter and the wavelength beam splitter.

[0017] In any embodiment, the coherent detection module includes a PD detector, the incoherent detection communication module includes an APD communication detector, and the incoherent detection tracking module includes a four-quadrant detector.

[0018] The present invention supports simultaneous transmission of multi-standard and multi-protocol laser inter-satellite links, supports both coherent and incoherent laser information transmission, can solve cross-constellation link establishment under different satellite systems and different systems, and realize the interconnection and interoperability of heterogeneous constellations. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of the structure and function of signal transmission of a space laser communication system according to an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of the structure and function of a signal receiving system of a space laser communication system according to an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of signal transmission and reception at one end of a space laser communication system according to an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of signal transmission and reception at the other end of a space laser communication system according to an embodiment of the present invention;

[0024] Figure 5 Schematic diagram of the structure and function of a laser transmitter according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be considered as part of the complete specification. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated for simplification or convenience. Furthermore, the parts of each structure in the drawings will be described separately. It is worth noting that the elements not shown in the drawings or not described in words are in a form known to ordinary technicians in the relevant technical field.

[0026] The description of the embodiments herein and any reference to directions and orientations are only for the convenience of description and are not to be construed as any limitation on the scope of protection of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination, and the present invention is not particularly limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0027] like Figure 1 and Figure 2 The figure shows a schematic diagram of the structure and function of a multi-standard transmission space laser communication system according to an embodiment of the present invention. The system includes a laser transmitter, a polarization beam splitter, a coarse pointing mechanism, a wavelength beam splitter, and an energy beam splitter. After being emitted by the laser transmitter, the optical signal is reflected by the polarization beam splitter to the coarse pointing mechanism for deflection and emission. After being received by the coarse pointing mechanism, the optical signal is transmitted to the wavelength beam splitter through the polarization beam splitter, a part of which is transmitted to the coherent detection module through the wavelength beam splitter, another part is reflected to the energy beam splitter through the wavelength beam splitter, and a part of which is transmitted to the incoherent detection tracking module through the energy beam splitter, and another part is reflected to the incoherent detection communication module through the energy beam splitter.

[0028] like Figure 3 and Figure 4 As shown, this embodiment can support bidirectional transmission of multi-standard laser intersatellite links based on the same-band non-beacon optical system. Assuming that the two terminals of the laser communication are A and B, then Figure 3 The figure shows the signal transmission diagram of the A end. Figure 4 The figure shows the signal transmission schematic diagram of the B end. At the A end, the laser transmitter can modulate and transmit signal light including OOK modulated light λ1 and BPSK / QPSK modulated light λ2, and the coarse pointing mechanism can receive signal light including OOK modulated light λ3 and BPSK / QPSK modulated light λ4. At the B end, the laser transmitter can modulate and transmit signal light including OOK modulated light λ3 and BPSK / QPSK modulated light λ4, and the coarse pointing mechanism can receive signal light including OOK modulated light λ1 and BPSK / QPSK modulated light λ2.

[0029] like Figure 5As shown, in this embodiment, the laser transmitter includes an IQ modulator and an intensity modulator connected in parallel, wherein the IQ modulator is an amplitude modulator. Compared with setting an IQ modulator or an intensity modulator separately, the IQ modulator and the intensity modulator are connected in parallel in the laser transmitter, so that the amplitude and phase of the optical carriers of different frequencies in the laser transmitter are simultaneously modulated, especially by using optical carriers with a wavelength interval of 15 to 25 nm to simultaneously perform OOK and BPSK / QPSK modulation and transmission, thereby effectively improving the multi-standard simultaneous transmission capability of the laser terminal. The wavelength of the signal light emitted by the laser transmitter can be selected from the frequency points of the 1550nm band specified by the ITU, and the wavelength intervals of λ1, λ2, λ3 and λ4 are within 15 to 25 nm, so as to facilitate wavelength splitting and shared optical amplifiers.

[0030] like Figure 1 As shown, in this embodiment, an optical amplifier and a signal transmission module are also provided between the laser transmitter and the polarization beam splitter, wherein the optical amplifier is used for light amplification, and the signal transmission module includes a collimator (not shown in the figure) for shaping the light. A first fast reflection mirror is also provided between the signal transmission module and the polarization beam splitter for reflecting the shaped optical signal to the polarization beam splitter.

[0031] like Figure 1 and Figure 2 As shown, in this embodiment, a telescope and a quarter wave plate are further provided between the polarization beam splitter and the coarse pointing mechanism. The telescope is located on the side close to the coarse pointing mechanism, and is used for collimation, beam expansion or beam reduction of the optical signal. The quarter wave plate is located on the side close to the polarization beam splitter, and is used for conversion of the optical signal. A second fast-reflecting mirror is further provided between the telescope and the polarization beam splitter. Specifically, the second fast-reflecting mirror may also be provided between the quarter wave plate and the polarization beam splitter, and is used for reflecting the light from the polarization beam splitter to the quarter wave plate. A band-pass filter may also be provided between the polarization beam splitter and the wavelength beam splitter, and is used for filtering.

[0032] like Figure 1-Figure 4 As shown, among which, Figure 3 and Figure 4In the figure, S light represents vertical polarized light, and P light represents horizontal polarized light. The OOK modulated light λ1 and BPSK / QPSK modulated light λ2 emitted by the laser transmitter are vertically polarized light. After passing through the optical amplifier and signal transmission module, they are reflected from the polarization beam splitter to the 1 / 4 wave plate and converted into right-handed circular polarization state. They are collimated and expanded by the telescope, and deflected and emitted by the coarse pointing mechanism. The OOK modulated light λ3 and BPSK / QPSK modulated light λ4 received by the coarse pointing mechanism are both left-handed circular polarization state. After being reduced in beam by the telescope, they are converted into horizontal polarization light by the 1 / 4 wave plate. After being transmitted through the polarization beam splitter and the bandpass filter, the light λ3 is reflected from the wavelength beam splitter to the energy beam splitter. A part of it is reflected from the energy beam splitter to the incoherent detection communication module, and the other part is transmitted from the energy beam splitter to the incoherent detection tracking module. After passing through the bandpass filter, the light λ4 is transmitted from the wavelength beam splitter to the coherent detection module.

[0033] Among them, the coherent detection module can be but not limited to a PD detector, the incoherent detection communication module can be but not limited to an APD communication detector, and the incoherent detection tracking module can be but not limited to a four-quadrant detector.

[0034] The multi-standard transmission space laser communication system of the embodiment of the present invention supports simultaneous transmission of multi-standard and multi-protocol laser inter-satellite links, supports both coherent and incoherent laser information transmission, can solve cross-constellation link establishment under different satellite systems and different systems, and realize the interconnection and interoperability of heterogeneous constellations.

[0035] With the development of laser communication, miniaturization is the main direction. In order to reduce the size of the equipment, a shared optical antenna structure is generally used for the transmitting and receiving channels. In view of the need for the laser communication system to simultaneously transmit and receive signal lights of different standards, a transmitter compatible with multiple modulation modes is used to simultaneously transmit two frequencies of 1550nm, OOK and BPSK / QPSK modulated signal lights, and the polarization beam splitter is used to realize the transmission and reception of the transmitting and receiving light beams. The received multi-standard signal lights are then passed through the wavelength beam splitter and the energy beam splitter to simultaneously realize the tracking and communication reception of different detection methods (incoherent, coherent). The following takes the multi-standard simultaneous transmission of the intersatellite laser communication system with no beacon light tracking and a two-way same-band transceiver system as an example to illustrate the multi-standard transmission space laser communication system of this embodiment.

[0036] like Figure 1-Figure 5As shown in FIG. 1 , the multi-carrier multi-standard transmitter (i.e., laser transmitter) of the terminal simultaneously transmits the signal beam as s-polarized light, and defines OOK modulated light as λ1 and BPSK modulated light as λ2. The light is transmitted through the same optical transmitting branch by the optical amplifier and the fiber combiner, and is reflected by the polarizing beam splitter (PBS), and converted into a right-handed circular polarization state by the 1 / 4 wave plate of the telescope. The light is collimated and expanded by the optical antenna (telescope), and deflected and directed by the coarse pointing mechanism for transmission. The signal lights λ3 and λ4 received by the terminal are both left-handed circularly polarized light, which are beam-contracted by the optical antenna, converted into p-light by the 1 / 4 wave plate, transmitted by the PBS, and enter the receiving channel. The signal light λ3 is reflected by the wavelength splitter and reaches the incoherent detection receiver. The energy splitter is used to realize the capture tracking of the received light beam and the incoherent communication detection demodulation. After the signal light is stably tracked and continuously established, the BPSK modulated signal light λ4 received by the terminal is coupled into the optical fiber through the wavelength splitter to realize coherent detection communication. Figure 2 and Figure 3 As shown in the figure, the combination of PBS, wave plate, wavelength splitter and energy splitter realizes the splitting of multi-standard transmission signal light and reception signal light.

[0037] Typical laser communication system supporting multi-standard simultaneous transmission Figure 4 The modules shown in the figure are composed of multi-system multi-carrier laser transmitter, fiber amplifier, fast reflection mirror, various splitter components, optical antenna, and coarse pointing mechanism. The multi-system multi-carrier laser transmitter realizes the emission of signal light of different frequencies within the 1550nm band; the PBS in the splitter component realizes the transmission and reception of the transmitted and received signal light, the wavelength splitter realizes the splitting of the received signal light of different modulation modes, and the energy splitter is mainly used for the optical branch splitting of the signal light capture tracking and communication function of one of the standards; the optical antenna realizes the signal light beam expansion and collimation, and the coarse pointing mechanism (including azimuth and elevation axis system) realizes the spatial two-dimensional pointing adjustment of the signal light, and a tracking detector is used as a four-quadrant detector, the incoherent communication detector is APD, and the coherent communication reception is the optical fiber coupled to the optical fiber mixer and the local oscillator light is received by the PD detector.

[0038] The key factors affecting the simultaneous transmission of multi-standard optical signals of laser communication terminals in the same band without beacon optical tracking system are:

[0039] The wavelength of the signal light emitted by the multi-standard multi-carrier laser transmitter is selected within the frequency point of the 1550nm band specified by ITU, and the intervals between the wavelengths of λ1, λ2, λ3, and λ4 are within 15nm to 25nm, which is convenient for wavelength splitting and sharing of optical amplifiers;

[0040] Multi-standard multi-carrier laser transmitters must have the functions of simultaneous OOK, BPSK / QPSK modulation and switching;

[0041] It is only necessary to set up a capture and tracking detector on one of the optical carrier branches to achieve stable link establishment of multiple signal lights at the same time. Compared with the transmission mode of single signal light, it improves transmission efficiency while reducing costs and weight.

[0042] The received OOK modulated signal light needs to be split into an incoherent detection receiving branch, and the received BPSK / QPSK modulated signal light needs to be split into a coherent detection receiving branch.

[0043] Based on the same-band beacon-free optical system, the bidirectional transmission of multi-standard laser intersatellite links is supported. Assuming that the two-end laser communication terminal is A / B, the transmission and reception link establishment workflow is as follows: Figure 3 and Figure 4 As shown:

[0044] 1) End A: emits right-handed circularly polarized signal light λ1, λ2, and receives left-handed circularly polarized signal light λ3, λ4;

[0045] 2) End B: emits left-handed circularly polarized signal light λ3, λ4, and receives left-handed circularly polarized signal light λ1, λ2;

[0046] 3) After completing the dual-end tracking and link establishment, the received optical signal is processed by each standard detection communication receiver and the service data is transmitted to the network layer.

[0047] The advantages of the embodiments of the present invention compared with the prior art are:

[0048] Based on the multi-standard coherent optical modulation technology, the embodiment of the present invention realizes the simultaneous modulation of the amplitude and phase of optical carriers of different frequencies in the transmitter by connecting an amplitude modulator in parallel in a multi-carrier multi-standard transmitter, thereby improving the existing multi-standard optical modulation system. By using optical carriers with a wavelength interval of 15nm to 20nm to simultaneously perform OOK and BPSK / QPSK modulation transmission, the multi-standard simultaneous transmission capability of the laser terminal can be effectively improved.

[0049] The optical system of the embodiment of the present invention realizes the simultaneous transmission and reception of multi-standard and four optical carrier signals based on the existing single-standard transmission and same-wavelength polarization splitting technology by combining polarization splitting, energy splitting and wavelength splitting of the optical system. It is also different from the single-standard different-band color splitting solution and can realize the function of simultaneous transmission of two standards of OOK / incoherent detection, BPSK, and QPSK / coherent detection;

[0050] The space laser communication system of the embodiment of the present invention can support the simultaneous detection and baseband processing of multi-standard and multi-protocol signal lights. Compared with the existing space-based relay node laser terminal which can only support information transmission of a single standard and protocol and requires multiple terminals to achieve standard compatibility, the weight and power consumption of the laser communication system of the embodiment of the present invention are greatly reduced.

[0051] 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, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-standard transmission space laser communication system, characterized in that: The system includes a laser transmitter, a polarization beam splitter, a coarse pointing mechanism, a wavelength beam splitter, and an energy beam splitter; The optical signal is emitted by the laser transmitter and then reflected by the polarization beam splitter to the coarse pointing mechanism for deflection and emission; After being received by the coarse pointing mechanism, the optical signal is transmitted to the wavelength splitter through the polarization splitter, a part of it is transmitted to the coherent detection module through the wavelength splitter, another part is reflected to the energy splitter through the wavelength splitter, and a part of it is transmitted to the incoherent detection tracking module through the energy splitter, and another part is reflected to the incoherent detection communication module through the energy splitter.

2. The multi-standard transmission space laser communication system according to claim 1, characterized in that: The laser transmitter includes an IQ modulator and an intensity modulator connected in parallel.

3. The multi-mode transmission space laser communication system according to claim 1, characterized in that: The laser transmitter can simultaneously modulate and switch signals including OOK and BPSK / QPSK signals.

4. The multi-mode transmission space laser communication system according to claim 1, characterized in that: The space laser communication system further comprises an optical amplifier and a signal transmission module located between the laser transmitter and the polarization beam splitter, wherein the signal transmission module comprises a collimator.

5. The multi-standard transmission space laser communication system according to claim 4, characterized in that: The space laser communication system also includes a first fast reflection mirror located between the signal transmission module and the polarization beam splitter.

6. The multi-mode transmission space laser communication system according to claim 1, characterized in that: The space laser communication system also includes a telescope arranged between the polarization beam splitter and the coarse pointing mechanism.

7. The multi-standard transmission space laser communication system according to claim 6, characterized in that: A quarter wave plate is provided between the telescope and the polarization beam splitter.

8. The multi-standard transmission space laser communication system according to claim 6, characterized in that: A second fast-reflecting mirror is provided between the telescope and the polarization beam splitter.

9. The multi-mode transmission space laser communication system according to claim 1, characterized in that: A bandpass filter is provided between the polarization beam splitter and the wavelength beam splitter.

10. The multi-standard transmission space laser communication system according to any one of claims 1 to 9, characterized in that: The coherent detection module includes a PD detector, the incoherent detection communication module includes an APD communication detector, and the incoherent detection tracking module includes a four-quadrant detector.

Images