Coherent optical transmission method and coherent optical transmission system

Abstract

The present invention relates to the field of optical communication technology, and discloses a coherent optical transmission method and a coherent optical transmission system, the method comprising: optically splitting an adjustable optical signal of a first preset wavelength to obtain a first optical signal and a second optical signal; optically combining the first optical signal and the second optical signal to obtain a combined optical signal, the bandwidth of the combined optical signal being the sum of the bandwidths of the first optical signal and the second optical signal; power amplifying the combined optical signal to obtain a first radio frequency optical signal, and outputting the first radio frequency optical signal through an optical fiber antenna. Therefore, the present invention can firstly optically split the adjustable optical signal to obtain a first optical signal and a second optical signal, and then optically combine the modulated first optical signal and the second optical signal to obtain a combined optical signal having a bandwidth that is the sum of the bandwidths of the first optical signal and the second optical signal, thereby increasing the bandwidth of the single optical signal outputted in the end, and meeting the large bandwidth transmission requirements of optical communication.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a coherent optical transmission method and a coherent optical transmission system. Background Art

[0002] With the development of the information age, the transmission of high-speed and large-capacity data has gradually become a hot topic of concern. Among them, laser communication is widely used in various fields due to its high transmission rate, small size, low power consumption, good confidentiality and strong anti-interference ability.

[0003] However, regarding long-distance satellite laser communications in space, existing optical communication modules cannot meet the transmission requirements of large bandwidth (over 100 Gbps). Therefore, there is an urgent need for an optical communication method that can meet the transmission requirements of large bandwidth.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The main purpose of the present invention is to provide a coherent optical transmission method and a coherent optical transmission system, aiming to solve the technical problem of how to provide an optical communication method that can meet the needs of large bandwidth transmission.

[0006] To achieve the above object, the present invention provides a coherent optical transmission method, the method comprising the following steps:

[0007] Performing optical splitting on the tunable optical signal of the first preset wavelength to obtain a first optical signal and a second optical signal;

[0008] Performing preset optical beam combining on the first optical signal and the second optical signal to obtain a beam-combined optical signal, wherein a bandwidth of the beam-combined optical signal is a sum of a bandwidth of the first optical signal and a bandwidth of the second optical signal;

[0009] The combined optical signal is power-amplified to obtain a first radio frequency optical signal, and the first radio frequency optical signal is output through an optical fiber antenna.

[0010] Optionally, the step of performing preset optical beam combining on the first optical signal and the second optical signal to obtain a beam-combined optical signal includes:

[0011] Performing preset modulation on both the first optical signal and the second optical signal to obtain a first regulated optical signal and a second regulated optical signal;

[0012] Performing preset modulation delay on both the first optical signal and the second optical signal to obtain a third regulated optical signal and a fourth regulated optical signal;

[0013] The first to fourth regulated optical signals are optically combined to obtain a combined optical signal.

[0014] Optionally, the method further comprises:

[0015] receiving a second radio frequency optical signal of a second preset wavelength through the optical fiber antenna, and constantly amplifying the second radio frequency optical signal to obtain an amplified modulated signal;

[0016] Performing demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal;

[0017] The mixed optical signal is demodulated in a preset manner to obtain demodulation information.

[0018] Optionally, the step of performing demodulation preprocessing on the amplified modulated signal to obtain a mixed optical signal includes:

[0019] Performing optical splitting on the amplified modulated signal to obtain two orthogonal modulated optical signals;

[0020] The two orthogonally modulated optical signals and the preset optical signal are mixed to obtain a mixed optical signal.

[0021] Optionally, the step of performing preset demodulation on the mixed optical signal to obtain demodulation information includes:

[0022] Performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;

[0023] Performing analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal;

[0024] The digital electrical signal is demodulated to obtain demodulation information.

[0025] In addition, to achieve the above-mentioned purpose, the present invention also proposes a coherent optical transmission system, the coherent optical transmission system comprising: a plurality of optical terminals, the plurality of optical terminals are located on the same horizontal link, the optical terminals comprise: a transmitting end, a receiving end and an optical fiber antenna;

[0026] The transmitting end is used to perform optical splitting on the tunable optical signal of the first preset wavelength to obtain a first optical signal and a second optical signal;

[0027] The transmitting end is further used to perform preset optical beam combining on the first optical signal and the second optical signal to obtain a beam-combined optical signal, wherein the bandwidth of the beam-combined optical signal is the sum of the bandwidths of the first optical signal and the second optical signal;

[0028] The transmitting end is also used to amplify the power of the combined optical signal to obtain a first radio frequency optical signal, and output the first radio frequency optical signal to the receiving end of the target optical terminal through the optical fiber antenna.

[0029] Optionally, the transmitting end includes: an adjustable laser, a polarization beam splitter, a first to a second Mach-Zehnder modulator, a first to a second modulation delay module, a polarization beam combiner and an optical power amplifier, the first modulation delay module includes: a third Mach-Zehnder modulator and a first phase delay, and the second modulation delay module includes: a fourth Mach-Zehnder modulator and a second phase delay;

[0030] The tunable laser is used to determine an tunable optical signal of a preset wavelength according to a preset adjustment signal input by a user;

[0031] The polarization beam splitter is used to perform optical splitting on the adjustable optical signal of the preset wavelength to obtain a first optical signal and a second optical signal;

[0032] A first Mach-Zehnder modulator, configured to perform a preset modulation on the first optical signal to obtain a first regulated optical signal;

[0033] The second Mach-Zehnder modulator is used to perform the preset modulation on the second optical signal to obtain a second adjusted optical signal;

[0034] A first modulation delay module, configured to perform a preset modulation delay on the first optical signal through the third Mach-Zehnder modulator and the first phase delay device to obtain a third regulated optical signal;

[0035] The second modulation delay module is used to perform the preset modulation delay on the second optical signal through the fourth Mach-Zehnder modulator and the second phase delay to obtain a fourth adjusted optical signal;

[0036] The polarization light combiner is used to combine the first regulated light signal to the fourth regulated light signal to obtain a combined light signal;

[0037] The optical power amplifier is used to amplify the power of the combined optical signal to obtain a first radio frequency optical signal.

[0038] Optionally, the receiving end includes: an optical preamplifier, a filtering module and a demodulation module;

[0039] The optical preamplifier is used to constantly amplify the second radio frequency optical signal of the second preset wavelength received by the optical fiber antenna to obtain an amplified modulated signal;

[0040] The filtering module is used to perform demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal;

[0041] The demodulation module is used to perform preset demodulation on the mixed-frequency optical signal to obtain demodulation information.

[0042] Optionally, the filtering module includes: a polarization beam splitter, a mixer and a local oscillator laser;

[0043] The polarization beam splitter is used to perform optical beam splitting on the amplified modulated signal to obtain two orthogonal modulated optical signals;

[0044] The mixer is used to mix the two orthogonally modulated optical signals and the preset optical signal output by the local oscillator laser to obtain a mixed optical signal.

[0045] Optionally, the demodulation module includes: a photodetector, an analog-to-digital converter and a digital signal processor;

[0046] The photoelectric detector is used to perform photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;

[0047] The analog-to-digital converter is used to perform analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal;

[0048] The digital signal processor is used to demodulate the digital electrical signal to obtain demodulation information.

[0049] The present invention discloses optical splitting of an adjustable optical signal of a first preset wavelength to obtain a first optical signal and a second optical signal; performing preset modulation on both the first optical signal and the second optical signal to obtain a first adjustment optical signal and a second adjustment optical signal; performing preset modulation delay on both the first optical signal and the second optical signal to obtain a third adjustment optical signal and a fourth adjustment optical signal; optically combining the first to fourth adjustment optical signals to obtain a combined optical signal, the bandwidth of the combined optical signal being the sum of the bandwidths of the first optical signal and the second optical signal; power amplifying the combined optical signal to obtain a first radio frequency optical signal, and outputting the first radio frequency optical signal through an optical fiber antenna. Therefore, the present invention can first perform optical splitting on the adjustable optical signal to obtain a first optical signal and a second optical signal, then modulate the first optical signal and the second optical signal, and optically combine the modulated first optical signal and the second optical signal to obtain a combined optical signal having a bandwidth that is the sum of the bandwidths of the first optical signal and the second optical signal, thereby increasing the bandwidth of the single optical signal outputted in the end to meet the large bandwidth transmission requirements of optical communication. In addition, the present invention can also increase the modulation mode by a phase delay device during the modulation process, thereby increasing the communication rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of a first process flow of a first embodiment of a coherent optical transmission method of the present invention;

[0051] Figure 2 It is a schematic diagram of a second process of the first embodiment of the coherent optical transmission method of the present invention;

[0052] Figure 3It is a schematic diagram of a first process flow of a second embodiment of a coherent optical transmission method of the present invention;

[0053] Figure 4 It is a second flow chart of the second embodiment of the coherent optical transmission method of the present invention;

[0054] Figure 5 is a structural block diagram of a first embodiment of a coherent optical transmission system of the present invention;

[0055] Figure 6 is a structural block diagram of a transmitting end in a first embodiment of a coherent optical transmission system of the present invention;

[0056] Figure 7 is a first structural block diagram of a receiving end in a first embodiment of a coherent optical transmission system of the present invention;

[0057] Figure 8 is a second structural block diagram of a receiving end in the first embodiment of the coherent optical transmission system of the present invention;

[0058] Fig. 9 It is a third structural block diagram of the receiving end in the first embodiment of the coherent optical transmission system of the present invention.

[0059] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0060] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0061] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0062] It should be noted that the descriptions involving "first", "second", etc. in the embodiments of the present invention are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0063] The embodiment of the present invention provides a coherent optical transmission method, referring to Figure 1, Figure 1 It is a schematic diagram of a first flow chart of a first embodiment of a coherent optical transmission method of the present invention.

[0064] In this embodiment, the coherent optical transmission method includes the following steps:

[0065] Step S10: performing optical splitting on the tunable optical signal of the first preset wavelength to obtain a first optical signal and a second optical signal.

[0066] It should be noted that the execution subject of the method of this embodiment may be an optical terminal, that is, a terminal device for optical signal transmission, or other coherent optical transmission systems that can achieve the same or similar functions and include the optical terminal. The coherent optical transmission system may include several optical terminals, and the several optical terminals are located on the same horizontal link without obstruction, and there should be a certain communication distance between the optical terminals, and the communication transmission link between the optical terminals can be established by adjusting the angle of each optical terminal.

[0067] It should be understood that the above-mentioned adjustable optical signal can be an optical signal of a first preset wavelength generated by an adjustable optical laser. The above-mentioned first preset wavelength can be any wavelength within the C-band, specifically 1530nm-1565nm. The specific value of the above-mentioned first preset wavelength can be set according to actual conditions, and this embodiment does not impose any restrictions on this.

[0068] It is easy to understand that, since the optical communication module in the existing satellite laser communication cannot transmit optical signals with large bandwidth, in order to realize the transmission of optical signals with large bandwidth, the present embodiment can first perform optical splitting on the above-mentioned adjustable optical signal during the modulation process to obtain two optical signals after splitting, namely the above-mentioned first optical signal and the second optical signal, and then modulate the first optical signal and the second optical signal, and then combine the modulated first optical signal and the second optical signal, so as to obtain a single optical signal with large bandwidth. Among them, the device for performing optical splitting can be a polarization beam splitter, and the tunable laser can be connected to the polarization beam splitter through an optical fiber. Therefore, in the present embodiment, the first optical signal and the second optical signal can be two orthogonal polarized light beams, and the two light beams are the same except for the orthogonal phase, that is, the first optical signal and the second optical signal are coherent light.

[0069] Step S20: performing preset optical beam combining on the first optical signal and the second optical signal to obtain a beam combined optical signal, wherein a bandwidth of the beam combined optical signal is a sum of bandwidths of the first optical signal and the second optical signal.

[0070] It can be understood that the combined optical signal is the above-mentioned single optical signal with a large bandwidth. In this embodiment, the combined optical signal can be combined by a polarized optical combiner. The bandwidth of the combined optical signal obtained after combining can be the sum of the bandwidths of the first optical signal and the second optical signal. Therefore, this embodiment can greatly increase the bandwidth of the final transmitted single-channel transmission optical signal, thereby meeting the large bandwidth transmission demand. In addition, in order to increase the transmission rate, the modulation method of the above-mentioned combined optical signal can be increased. Therefore, further, as an implementable method, as Figure 2 As shown, Figure 2 2 is a schematic diagram of a second flow chart of the first embodiment of the coherent optical transmission method of the present invention. In this embodiment, step S20 includes:

[0071] Step S201: performing preset modulation on both the first optical signal and the second optical signal to obtain a first regulated optical signal and a second regulated optical signal;

[0072] Step S202: performing preset modulation delay on the first optical signal and the second optical signal to obtain a third regulated optical signal and a fourth regulated optical signal;

[0073] Step S203: optically combine the first to fourth regulated optical signals to obtain a combined optical signal.

[0074] It should be understood that for the above two polarized lights, namely the first optical signal and the second optical signal, this embodiment can respectively divide the first optical signal and the second optical signal into two beams 1 and 2 through a one-to-two optical fiber splitter, thereby obtaining four optical signals, namely the first optical signal beam 1, the first optical signal beam 2, the second optical signal beam 1, and the second optical signal beam 2; then, this embodiment can respectively connect the first optical signal beam 1 and the second optical signal beam 1 to the Mach-Zehnder modulator through optical fibers for QPSK modulation, namely the above preset modulation, and the first optical signal beam 1 and the second optical signal beam 1 are modulated by Mach-Zehnder to obtain the first regulated optical signal and the second regulated optical signal, and the first regulated optical signal and the second regulated optical signal are directly connected to the polarization beam combiner. The first optical signal beam 2 and the second optical signal beam 2 can be connected by optical fiber to the Mach-Zehnder modulation and then processed by a 90° phase delay device, namely, after the above preset modulation delay, the third regulated optical signal and the fourth regulated optical signal are obtained, and then the third regulated optical signal and the fourth regulated optical signal are connected to the polarization beam combiner. The four light beams are combined into one beam through a polarization beam combiner, thereby obtaining the above-mentioned combined light signal.

[0075] It should be understood that the present embodiment can divide two polarized light beams into two equal paths through an optical fiber beam splitter, one of which is modulated by a Mach-Zehnder modulator and then directly sent to a polarization beam combiner, and the other is modulated by a Mach-Zehnder modulator and then sent to a polarization beam combiner through a 90° phase delay. Each Mach-Zehnder modulator modulates different information. Finally, four beams with a phase difference of 90 degrees are combined into one beam through a polarization beam combiner. Among them, the modulation of the signal can be increased by the phase delay device. Specifically, each phase delay will increase a modulation mode, thereby facilitating the improvement of the communication rate. Based on the above steps, the present embodiment can realize the conversion of electrical signals to optical signals and modulate high-speed data into optical signals.

[0076] Step S30: power amplify the combined optical signal to obtain a first radio frequency optical signal, and output the first radio frequency optical signal through an optical fiber antenna.

[0077] It should be noted that, in this embodiment, the combined light beam, i.e., the combined light signal, can be connected to an optical power amplifier via an optical fiber for power amplification, and finally the amplified light beam, i.e., the first RF light signal, can be output through an optical fiber antenna (or Cassegrain optical fiber antenna) to complete the emission of spatial light.

[0078] This embodiment discloses optical splitting of an adjustable optical signal of a first preset wavelength to obtain a first optical signal and a second optical signal; performing preset modulation on both the first optical signal and the second optical signal to obtain a first regulated optical signal and a second regulated optical signal; performing preset modulation delay on both the first optical signal and the second optical signal to obtain a third regulated optical signal and a fourth regulated optical signal; optically combining the first to fourth regulated optical signals to obtain a combined optical signal, the bandwidth of the combined optical signal being the sum of the bandwidths of the first optical signal and the second optical signal; power amplifying the combined optical signal to obtain a first radio frequency optical signal, and outputting the first radio frequency optical signal through an optical fiber antenna. Therefore, this embodiment can first optically split the adjustable optical signal to obtain a first optical signal and a second optical signal, then modulate the first optical signal and the second optical signal, and optically combine the modulated first optical signal and the second optical signal, so as to obtain a combined optical signal having a bandwidth that is the sum of the bandwidths of the first optical signal and the second optical signal, thereby increasing the bandwidth of the single optical signal outputted in the end, and meeting the large bandwidth transmission requirements of optical communication. In addition, in the modulation process, the present embodiment can also increase the modulation mode by using a phase delay device, thereby improving the communication rate.

[0079] refer to Figure 3 , Figure 3 It is a schematic diagram of a first flow chart of a second embodiment of a coherent optical transmission method of the present invention.

[0080] It is understandable that there is not only a sending process but also a receiving process in the coherent optical communication process. However, coherent optical communication often has problems such as wavelength variation, frequency deviation and phase noise, which affect the performance of the communication system, leading to an increase in the communication bit error rate and even the occurrence of communication interruption. Therefore, in order to improve the stability and reliability of communication reception, further, based on the above-mentioned first embodiment, in this embodiment, the method also includes:

[0081] Step S11: receiving a second radio frequency optical signal of a second preset wavelength through the optical fiber antenna, and constantly amplifying the second radio frequency optical signal to obtain an amplified modulated signal;

[0082] It should be understood that the second radio frequency optical signal can be an optical signal emitted by other optical terminals in the coherent optical transmission system, and the second preset wavelength is the wavelength corresponding to the other optical terminals. The second preset wavelength can also be any wavelength in the C band, specifically 1530nm-1565nm. The specific value of the second preset wavelength can be set by other optical terminals according to actual conditions, and this embodiment does not limit this. Based on optical terminals with different wavelengths, this embodiment can construct a bidirectional high-speed bandwidth coherent optical communication data transmission system with different wavelengths, and the wavelength tunable range of the system can cover the entire C band.

[0083] It can be understood that the spatial light emitted by any optical terminal can be refocused and converged into the optical fiber through the optical fiber antenna. In this embodiment, the second RF optical signal can be constantly amplified by the optical preamplifier, and the optical fiber antenna can be connected to the optical preamplifier through the optical fiber. Among them, the optical preamplifier has the function of constant output power, which can improve the phenomenon of unstable received optical power caused by platform vibration and spatial fluctuation, and play a role in stable coherent detection. In this embodiment, optical preamplifiers of different powers can be selected according to different transmission distances. The longer the distance, the greater the corresponding power of the optical preamplifier.

[0084] Step S21: performing demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal;

[0085] It is understandable that there are many noise signals in the second RF signal after it is transmitted through the air. Therefore, in order to improve the accuracy of the final information acquisition, this embodiment can first demodulate and pre-process the amplified modulated signal. Specifically, as an implementable method, Figure 4 As shown, Figure 4 This is a first flow chart of the second embodiment of the coherent optical transmission method of the present invention. In this embodiment, step S21 includes:

[0086] Step S211: performing optical splitting on the amplified modulated signal to obtain two orthogonal modulated optical signals;

[0087] Step S212: Mix the two orthogonally modulated optical signals and the preset optical signal to obtain a mixed optical signal.

[0088] It should be noted that, in this embodiment, the polarization state of the amplified modulated signal can be separated by a polarization beam splitter, and divided into two orthogonal polarized light beams, that is, the above-mentioned two orthogonal modulated light signals, and the two light beams are the same except that the phases are orthogonal. Then, in this embodiment, the polarized light beam can be mixed with the preset light signal by 90° by a mixer to obtain a mixed light signal.

[0089] It should be understood that the above-mentioned preset optical signal can be a preset optimal wavelength, which is output by the local oscillator laser. Frequency mixing refers to the process of injecting two beams of light with different frequencies into a nonlinear medium to obtain an intermediate frequency signal, and outputting optical signals with phases of 0°, 90°, 180° and 270° respectively after frequency mixing, so as to facilitate the subsequent demodulation and restoration of the original data information based on the optical signals with four phases. In this embodiment, if the signal-to-noise ratio of the amplified modulated signal after receiving and amplifying is relatively low, that is, if it contains more signals of other frequencies, the preset optical signal output by the local oscillator laser can be mixed with the two orthogonal modulated optical signals after beam splitting, so as to obtain only the optical signal with the same wavelength as the preset optical signal in the local oscillator laser, thereby achieving a screening and filtering effect.

[0090] Step S31: performing preset demodulation on the mixed optical signal to obtain demodulation information.

[0091] It should be noted that after obtaining the filtered mixed optical signal, this embodiment can obtain demodulation information by performing preset demodulation on the mixed optical signal. Specifically, as an implementable method, in this embodiment, step S31 includes:

[0092] Step S311: performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;

[0093] Step S312: performing analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal;

[0094] Step S313: demodulate the digital electrical signal to obtain demodulation information.

[0095] It should be understood that in this embodiment, the mixed frequency optical signal transmitted through the optical fiber can be photoelectrically converted by the photoelectric detector to obtain an analog electrical signal. Then, in this embodiment, the analog electrical signal output by the photoelectric detector can be converted into a digital electrical signal based on an analog-to-digital converter, and finally the output 4-channel digital signal can be input into a digital signal processor for signal demodulation to obtain demodulation information, thereby converting the optical signal into an electrical signal, restoring the original data information corresponding to the second radio frequency signal, and completing the demodulation and information resolution of the coherent optical signal.

[0096] It is easy to understand that by continuing to add transmitting and receiving equipment such as tunable lasers, more channels of laser communication links can be built, thereby obtaining higher-speed data transmission. After adding tunable lasers, the corresponding Mach-Zehnder modulators, phase delay devices, analog-to-digital converters, photodetectors, and mixers need to be added. The principle is the same as before, except that light beams of different wavelengths are added, and the modulation and demodulation methods are the same.

[0097] In this embodiment, a second radio frequency optical signal of a second preset wavelength is received by an optical fiber antenna, and the second radio frequency optical signal is constantly amplified to obtain an amplified modulated signal; the amplified modulated signal is optically split to obtain two orthogonal modulated optical signals; the two orthogonal modulated optical signals and the preset optical signal are mixed to obtain a mixed optical signal. The mixed optical signal is photoelectrically converted to obtain an analog electrical signal; the analog electrical signal is analog-to-digital converted to obtain a digital electrical signal; the digital electrical signal is demodulated to obtain demodulation information. In this embodiment, the second radio frequency optical signal can be constantly amplified to obtain a constant beam energy and amplified to output the amplified modulated signal, thereby improving the communication detection sensitivity while ensuring that the beam is not affected by the platform jitter, playing a role in stabilizing spatial optical reception and improving the stability of signal reception; in addition, in this embodiment, the two orthogonal modulated optical signals obtained after the amplified modulated signal is optically split can be mixed with the preset optical signal, so as to obtain only the optical signal with the same wavelength as the preset optical signal, thereby achieving a screening and filtering effect. Therefore, this embodiment can also improve the accuracy of obtaining demodulated information.

[0098] Reference Figure 5 , Figure 5 It is a structural block diagram of the first embodiment of the coherent optical transmission system of the present invention.

[0099] like Figure 5 As shown, the coherent optical transmission system proposed in the embodiment of the present invention includes: a plurality of optical terminals, the plurality of optical terminals are located on the same horizontal link, and the optical terminals include: a transmitting end, a receiving end and an optical fiber antenna;

[0100] The transmitting end is used to perform optical splitting on the tunable optical signal of the first preset wavelength to obtain a first optical signal and a second optical signal;

[0101] The transmitting end is further used to perform preset optical beam combining on the first optical signal and the second optical signal to obtain a beam-combined optical signal, wherein the bandwidth of the beam-combined optical signal is the sum of the bandwidths of the first optical signal and the second optical signal;

[0102] The transmitting end is also used to amplify the power of the combined optical signal to obtain a first radio frequency optical signal, and output the first radio frequency optical signal to the receiving end of the target optical terminal through the optical fiber antenna.

[0103] It should be noted that the coherent optical transmission system in this embodiment may include several optical terminals, and the several optical terminals are located on the same horizontal link without obstruction, and there should be a certain communication distance between the optical terminals, and the communication transmission link between the optical terminals can be established by adjusting the angle of each optical terminal. Each optical terminal may include a transmitting end, a receiving end and an optical fiber antenna, and signals can be transmitted between the optical terminals through the optical fiber antenna.

[0104] It is easy to understand that, since the optical communication module in the existing satellite laser communication cannot transmit optical signals with large bandwidth, in order to realize the transmission of optical signals with large bandwidth, the present embodiment can first perform optical splitting on the above-mentioned adjustable optical signal during the modulation process to obtain two optical signals after splitting, namely the above-mentioned first optical signal and the second optical signal, and then modulate the first optical signal and the second optical signal, and then combine the modulated first optical signal and the second optical signal, so as to obtain a single optical signal with large bandwidth. Among them, the device for performing optical splitting can be a polarization beam splitter, and the tunable laser can be connected to the polarization beam splitter through an optical fiber. Therefore, in the present embodiment, the first optical signal and the second optical signal can be two orthogonal polarized light beams, and the two light beams are the same except for the orthogonal phase, that is, the first optical signal and the second optical signal are coherent light.

[0105] It can be understood that the combined optical signal is the single optical signal with large bandwidth. In this embodiment, the bandwidth of the combined optical signal obtained after combining can be the sum of the bandwidths of the first optical signal and the second optical signal. Therefore, this embodiment can greatly increase the bandwidth of the single optical signal transmitted in the end, thereby meeting the large bandwidth transmission demand. In addition, in order to increase the transmission rate, the modulation method of the combined optical signal in the modulation process can be increased. Therefore, further, as an implementable method, Figure 6 As shown, Figure 6 This is a structural block diagram of a transmitting end in the first embodiment of a coherent optical transmission system of the present invention. In this embodiment, the transmitting end includes: an adjustable laser, a first polarization beam splitter, a first to second Mach-Zehnder modulator, a first to second modulation delay module, a polarization beam combiner and an optical power amplifier. The first modulation delay module includes: a third Mach-Zehnder modulator and a first phase delay device, and the second modulation delay module includes: a fourth Mach-Zehnder modulator and a second phase delay device.

[0106] The tunable laser is used to determine an tunable optical signal of a preset wavelength according to a preset adjustment signal input by a user;

[0107] The first polarization beam splitter is used to perform optical splitting on the adjustable optical signal of the preset wavelength to obtain a first optical signal and a second optical signal;

[0108] A first Mach-Zehnder modulator, configured to perform a preset modulation on the first optical signal to obtain a first regulated optical signal;

[0109] The second Mach-Zehnder modulator is used to perform the preset modulation on the second optical signal to obtain a second adjusted optical signal;

[0110] A first modulation delay module, configured to perform a preset modulation delay on the first optical signal through the third Mach-Zehnder modulator and the first phase delay device to obtain a third regulated optical signal;

[0111] The second modulation delay module is used to perform the preset modulation delay on the second optical signal through the fourth Mach-Zehnder modulator and the second phase delay to obtain a fourth adjusted optical signal;

[0112] The polarization light combiner is used to combine the first regulated light signal to the fourth regulated light signal to obtain a combined light signal;

[0113] The optical power amplifier is used to amplify the power of the combined optical signal to obtain a first radio frequency optical signal.

[0114] It should be understood that the above-mentioned adjustable optical signal can be an optical signal of a first preset wavelength generated by an adjustable optical laser. The above-mentioned first preset wavelength can be any wavelength within the C-band, specifically 1530nm-1565nm. The specific value of the above-mentioned first preset wavelength can be set according to actual conditions, and this embodiment does not impose any restrictions on this.

[0115] It can be understood that for the above two polarized lights, i.e., the first optical signal and the second optical signal, this embodiment can respectively divide the first optical signal and the second optical signal into two beams 1 and 2 through a one-to-two optical fiber splitter, thereby obtaining four optical signals, i.e., the first optical signal beam 1, the first optical signal beam 2, the second optical signal beam 1, and the second optical signal beam 2; then, this embodiment can respectively connect the first optical signal beam 1 to the first Mach-Zehnder modulator through an optical fiber, and connect the second optical signal beam 1 to the second Mach-Zehnder modulator for QPSK modulation, i.e., the above preset modulation, thereby obtaining the first regulated optical signal and the second regulated optical signal, and directly connect the first regulated optical signal and the second regulated optical signal to the polarization beam combiner. The first optical signal beam 2 can pass through the third Mach-Zehnder modulator and then pass through the first phase delay, i.e., the above preset modulation delay, and obtain the third regulated optical signal after processing; the second optical signal beam 2 is connected to the fourth Mach-Zehnder modulator by an optical fiber and then processed by the second phase delay to obtain the fourth regulated optical signal; and then the third regulated optical signal and the fourth regulated optical signal are connected to the polarization beam combiner. The four light beams can be combined into one beam by a polarization beam combiner, thereby obtaining the above-mentioned combined light signal. Wherein, the first phase retarder and the second phase retarder can both be 90° phase retarder.

[0116] It should be understood that the present embodiment can divide two polarized light beams into two equal paths through an optical fiber beam splitter, one of which is modulated by a Mach-Zehnder modulator and then directly sent to a polarization beam combiner, and the other is modulated by a Mach-Zehnder modulator and then sent to a polarization beam combiner through a 90° phase delay. Each Mach-Zehnder modulator modulates different information. Finally, four beams with a phase difference of 90 degrees are combined into one beam through a polarization beam combiner. Among them, the modulation of the signal can be increased by the phase delay device. Specifically, each phase delay will increase a modulation mode, thereby facilitating the improvement of the communication rate. Based on the above steps, the present embodiment can realize the conversion of electrical signals to optical signals and modulate high-speed data into optical signals.

[0117] It should be noted that, in this embodiment, the combined light beam, i.e., the combined light signal, can be connected to an optical power amplifier via an optical fiber for power amplification, and finally the amplified light beam, i.e., the first RF light signal, can be output through an optical fiber antenna (or Cassegrain optical fiber antenna) to complete the emission of spatial light.

[0118] It is understandable that the coherent optical communication process not only involves the sending process, but also the receiving process. However, coherent optical communication often has problems such as wavelength variation, frequency deviation and phase noise, which affect the performance of the communication system, leading to an increase in the communication bit error rate and even the occurrence of communication interruption. Therefore, in order to improve the stability and reliability of communication reception, further, as an implementable method, Figure 7 As shown, Figure 7 The first structural block diagram of the receiving end in the first embodiment of the coherent optical transmission system of the present invention, in this embodiment, the receiving end includes: an optical preamplifier, a filtering module and a demodulation module;

[0119] The optical preamplifier is used to constantly amplify the second radio frequency optical signal of the second preset wavelength received by the optical fiber antenna to obtain an amplified modulated signal;

[0120] The filtering module is used to perform demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal;

[0121] The demodulation module is used to perform preset demodulation on the mixed-frequency optical signal to obtain demodulation information.

[0122] It should be understood that the second radio frequency optical signal can be an optical signal emitted by other optical terminals in the coherent optical transmission system, and the second preset wavelength is the wavelength corresponding to the other optical terminals. The second preset wavelength can also be any wavelength in the C band, specifically 1530nm-1565nm. The specific value of the second preset wavelength can be set by other optical terminals according to actual conditions, and this embodiment does not limit this. Based on optical terminals with different wavelengths, this embodiment can construct a bidirectional high-speed bandwidth coherent optical communication data transmission system with different wavelengths, and the wavelength tunable range of the system can cover the entire C band.

[0123] It can be understood that the spatial light emitted by any optical terminal can be refocused and converged into the optical fiber through the optical fiber antenna. In this embodiment, the second RF optical signal can be constantly amplified by the optical preamplifier, and the optical fiber antenna can be connected to the optical preamplifier through the optical fiber. Among them, the optical preamplifier has the function of constant output power, which can improve the phenomenon of unstable received optical power caused by platform vibration and spatial fluctuation, and play a role in stable coherent detection. In this embodiment, optical preamplifiers of different powers can be selected according to different transmission distances. The longer the distance, the greater the corresponding power of the optical preamplifier.

[0124] It is understandable that the second RF signal has more noise signals after being transmitted in the air. Therefore, in order to improve the accuracy of the final information acquisition, this embodiment can first demodulate and pre-process the amplified modulated signal. Further, as an implementable method, Figure 8 As shown, Figure 8 It is a second structural block diagram of the receiving end in the first embodiment of the coherent optical transmission system of the present invention. In this embodiment, the filtering module includes: a second polarization beam splitter, a mixer and a local oscillator laser;

[0125] The second polarization beam splitter is used to perform optical beam splitting on the amplified modulated signal to obtain two orthogonal modulated optical signals;

[0126] The mixer is used to mix the two orthogonally modulated optical signals and the preset optical signal output by the local oscillator laser to obtain a mixed optical signal.

[0127] It should be noted that, in this embodiment, the polarization state of the amplified modulated signal can be separated by a polarization beam splitter, and divided into two orthogonal polarized light beams, that is, the above-mentioned two orthogonal modulated light signals, and the two light beams are the same except that the phases are orthogonal. Then, in this embodiment, the polarized light beam can be mixed with the preset light signal by 90° by a mixer to obtain a mixed light signal.

[0128] It should be understood that the above-mentioned preset optical signal can be a preset optimal wavelength, which is output by the local oscillator laser. Frequency mixing refers to the process of injecting two beams of light with different frequencies into a nonlinear medium to obtain an intermediate frequency signal, and outputting optical signals with phases of 0°, 90°, 180° and 270° respectively after frequency mixing, so as to facilitate the subsequent demodulation and restoration of the original data information based on the optical signals with four phases. In this embodiment, if the signal-to-noise ratio of the amplified modulated signal after receiving and amplifying is relatively low, that is, if it contains more signals of other frequencies, the preset optical signal output by the local oscillator laser can be mixed with the two orthogonal modulated optical signals after beam splitting, so as to obtain only the optical signal with the same wavelength as the preset optical signal in the local oscillator laser, thereby achieving a screening and filtering effect.

[0129] It should be noted that after obtaining the filtered mixed optical signal, the present embodiment can obtain demodulation information by performing preset demodulation on the mixed optical signal. Therefore, further, as an implementable method, Fig. 9 As shown, Fig. 9 The third structural block diagram of the receiving end in the first embodiment of the coherent optical transmission system of the present invention, in this embodiment, the demodulation module includes: a photodetector, an analog-to-digital converter and a digital signal processor;

[0130] The photoelectric detector is used to perform photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;

[0131] The analog-to-digital converter is used to perform analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal;

[0132] The digital signal processor is used to demodulate the digital electrical signal to obtain demodulation information.

[0133] It should be understood that in this embodiment, the mixed frequency optical signal transmitted through the optical fiber can be photoelectrically converted by the photoelectric detector to obtain an analog electrical signal. Then, in this embodiment, the analog electrical signal output by the photoelectric detector can be converted into a digital electrical signal based on an analog-to-digital converter, and finally the output 4-channel digital signal can be input into a digital signal processor for signal demodulation to obtain demodulation information, thereby converting the optical signal into an electrical signal, restoring the original data information corresponding to the second radio frequency signal, and completing the demodulation and information resolution of the coherent optical signal.

[0134] It is easy to understand that by continuing to add transmitting and receiving equipment such as tunable lasers, more channels of laser communication links can be built, thereby obtaining higher-speed data transmission. After adding tunable lasers, the corresponding Mach-Zehnder modulators, phase delay devices, analog-to-digital converters, photodetectors, and mixers need to be added. The principle is the same as before, except that light beams of different wavelengths are added, and the modulation and demodulation methods are the same.

[0135] The present embodiment discloses a coherent optical transmission system, which includes: a plurality of optical terminals, which are located on the same horizontal plane link, and the optical terminals include: a transmitting end, a receiving end and an optical fiber antenna; the transmitting end is used to perform optical splitting on an adjustable optical signal of a first preset wavelength to obtain a first optical signal and a second optical signal; the transmitting end is also used to perform preset optical beam combining on the first optical signal and the second optical signal to obtain a combined optical signal, and the bandwidth of the combined optical signal is the sum of the bandwidths of the first optical signal and the second optical signal; the transmitting end is also used to power amplify the combined optical signal to obtain a first radio frequency optical signal, and output the first radio frequency optical signal to the receiving end of the target optical terminal through the optical fiber antenna. The transmitting end includes: an adjustable laser, a first polarization beam splitter, a first to second Mach-Zehnder modulator, a first to second modulation delay module, a polarization beam combiner and an optical power amplifier, wherein the first modulation delay module includes: a third Mach-Zehnder modulator and a first phase delay, and the second modulation delay module includes: a fourth Mach-Zehnder modulator and a second phase delay; the adjustable laser is used to determine an adjustable optical signal of a preset wavelength according to a preset adjustment signal input by a user; the first polarization beam splitter is used to perform optical splitting on the adjustable optical signal of a preset wavelength to obtain a first optical signal and a second optical signal; the first Mach-Zehnder modulator is used to perform preset modulation on the first optical signal to obtain a first regulated optical signal; a second Mach-Zehnder modulator, used for performing preset modulation on the second optical signal to obtain a second regulated optical signal; a first modulation delay module, used for performing preset modulation and delay on the first optical signal through a third Mach-Zehnder modulator and a first phase delay to obtain a third regulated optical signal; a second modulation delay module, used for performing preset modulation and delay on the second optical signal through a fourth Mach-Zehnder modulator and a second phase delay to obtain a fourth regulated optical signal; a polarization light combiner, used for performing optical combination on the first regulated optical signal to the fourth regulated optical signal to obtain a combined optical signal; and an optical power amplifier, used for performing power amplification on the combined optical signal to obtain a first radio frequency optical signal. The receiving end includes: an optical preamplifier, a second polarization beam splitter, a mixer, a local oscillator laser, a photodetector, an analog-to-digital converter and a digital signal processor; the optical preamplifier is used to constantly amplify the second radio frequency optical signal of the second preset wavelength received by the optical fiber antenna to obtain an amplified modulated signal; the second polarization beam splitter is used to optically split the amplified modulated signal to obtain two orthogonal modulated optical signals; the mixer is used to mix the two orthogonal modulated optical signals and the preset optical signal output by the local oscillator laser to obtain a mixed optical signal; the photodetector is used to perform photoelectric conversion on the mixed optical signal to obtain an analog electrical signal; the analog-to-digital converter is used to perform analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal; the digital signal processor is used to demodulate the digital electrical signal to obtain demodulation information.Therefore, in this embodiment, the above-mentioned adjustable optical signal can be first optically split to obtain the first optical signal and the second optical signal, and then the first optical signal and the second optical signal can be modulated, and the modulated first optical signal and the second optical signal can be combined to obtain a combined optical signal whose bandwidth is the sum of the bandwidths of the first optical signal and the second optical signal, thereby increasing the bandwidth of the final output single optical signal to meet the large bandwidth transmission requirements of optical communication. In addition, in this embodiment, the modulation mode can be increased by a phase delay device during the modulation process to increase the communication rate. In this embodiment, the constant beam energy of the second RF optical signal can be amplified and the output amplified modulated signal can be amplified to ensure that the beam is not affected by the platform jitter while improving the communication detection sensitivity, thereby playing a role in stabilizing spatial optical reception and improving the stability of signal reception; in addition, in this embodiment, the two orthogonal modulated optical signals obtained after the optical splitting of the amplified modulated signal can be mixed with the preset optical signal to obtain only the optical signal with the same wavelength as the preset optical signal, thereby achieving a screening and filtering effect. Therefore, this embodiment can also improve the accuracy of obtaining demodulated information.

[0136] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0137] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0138] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as a read-only memory / random access memory, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0139] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A coherent optical transmission method, characterized in that: The method comprises: Performing polarization light splitting on the tunable optical signal of the first preset wavelength to obtain a coherent first optical signal and a second optical signal; Performing preset polarization light beam combining on the first optical signal and the second optical signal to obtain a beam-combined optical signal, wherein the bandwidth of the beam-combined optical signal is the sum of the bandwidths of the first optical signal and the second optical signal; Amplifying the power of the combined optical signal to obtain a first radio frequency optical signal, and outputting the first radio frequency optical signal through an optical fiber antenna; The step of performing preset polarization light beam combining on the first optical signal and the second optical signal to obtain a beam combined optical signal comprises: Performing preset modulation on both the first optical signal and the second optical signal to obtain a first regulated optical signal and a second regulated optical signal; Performing preset modulation delay on both the first optical signal and the second optical signal to obtain a third regulated optical signal and a fourth regulated optical signal; Performing polarization light combining on the first to fourth regulated optical signals to obtain a combined optical signal; The method further comprises: receiving a second radio frequency optical signal of a second preset wavelength through the optical fiber antenna, and constantly amplifying the second radio frequency optical signal to obtain an amplified modulated signal; Performing demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal; The mixed optical signal is demodulated in a preset manner to obtain demodulation information.

2. The coherent optical transmission method according to claim 1, characterized in that: The step of performing demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal comprises: Performing polarization light splitting on the amplified modulated signal to obtain two orthogonal modulated optical signals; The two orthogonally modulated optical signals and the preset optical signal are mixed to obtain a mixed optical signal.

3. The coherent optical transmission method according to claim 2, characterized in that: The step of performing preset demodulation on the mixed optical signal to obtain demodulation information comprises: Performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal; Performing analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal; The digital electrical signal is demodulated to obtain demodulation information.

4. A coherent optical transmission system, characterized in that: The system comprises: a plurality of optical transceivers, the plurality of optical transceivers are located on the same horizontal link, and the optical transceivers comprise: a transmitting end, a receiving end and an optical fiber antenna; The transmitting end is used to perform polarization light splitting on the tunable optical signal of the first preset wavelength to obtain a coherent first optical signal and a coherent second optical signal; The transmitting end is further used to perform preset polarization light beam combining on the first optical signal and the second optical signal to obtain a beam-combined optical signal, wherein the bandwidth of the beam-combined optical signal is the sum of the bandwidths of the first optical signal and the second optical signal; The transmitting end is further used to amplify the power of the combined optical signal to obtain a first radio frequency optical signal, and output the first radio frequency optical signal to the receiving end of the target optical terminal through the optical fiber antenna; The transmitting end includes: an adjustable laser, a first polarization beam splitter, first to second Mach-Zehnder modulators, first to second modulation delay modules, a polarization beam combiner and an optical power amplifier, the first modulation delay module includes: a third Mach-Zehnder modulator and a first phase delay, the second modulation delay module includes: a fourth Mach-Zehnder modulator and a second phase delay; The tunable laser is used to determine an tunable optical signal of a preset wavelength according to a preset adjustment signal input by a user; The first polarization beam splitter is used to perform polarization beam splitting on the adjustable optical signal of the preset wavelength to obtain a coherent first optical signal and a coherent second optical signal; A first Mach-Zehnder modulator, configured to perform a preset modulation on the first optical signal to obtain a first regulated optical signal; The second Mach-Zehnder modulator is used to perform the preset modulation on the second optical signal to obtain a second adjusted optical signal; A first modulation delay module, configured to perform a preset modulation delay on the first optical signal through the third Mach-Zehnder modulator and the first phase delay device to obtain a third regulated optical signal; The second modulation delay module is used to perform the preset modulation delay on the second optical signal through the fourth Mach-Zehnder modulator and the second phase delay to obtain a fourth adjusted optical signal; The polarization beam combiner is used to perform polarization beam combining on the first regulated optical signal to the fourth regulated optical signal to obtain a combined optical signal; The optical power amplifier is used to amplify the power of the combined optical signal to obtain a first radio frequency optical signal; The receiving end includes: an optical preamplifier, a filtering module and a demodulation module; The optical preamplifier is used to constantly amplify the second radio frequency optical signal of the second preset wavelength received by the optical fiber antenna to obtain an amplified modulated signal; The filtering module is used to perform demodulation preprocessing on the amplified modulated signal to obtain a mixed frequency optical signal; The demodulation module is used to perform preset demodulation on the mixed-frequency optical signal to obtain demodulation information.

5. The coherent optical transmission system according to claim 4, characterized in that: The filtering module includes: a second polarization beam splitter, a frequency mixer and a local oscillator laser; The second polarization beam splitter is used to perform polarization beam splitting on the amplified modulated signal to obtain two orthogonal modulated optical signals; The mixer is used to mix the two orthogonally modulated optical signals and the preset optical signal output by the local oscillator laser to obtain a mixed optical signal.

6. The coherent optical transmission system according to claim 5, characterized in that: The demodulation module includes: a photodetector, an analog-to-digital converter and a digital signal processor; The photoelectric detector is used to perform photoelectric conversion on the mixed optical signal to obtain an analog electrical signal; The analog-to-digital converter is used to perform analog-to-digital conversion on the analog electrical signal to obtain a digital electrical signal; The digital signal processor is used to demodulate the digital electrical signal to obtain demodulation information.

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