High-speed large-capacity intermediate infrared laser communication method and system based on integrated waveguide

Abstract

The invention provides a high-speed large-capacity intermediate infrared laser communication method and system based on an integrated waveguide, and is mainly used for solving the problems that when an existing space laser communication system adopts intermediate infrared band transmission, a frequency conversion scheme based on a block material is poor in phase matching, large in size, low in conversion efficiency, low in cost and the like. And the actual requirements of high-speed and large-capacity communication are difficult to meet. According to the high-speed large-capacity mid-infrared laser communication method based on the integrated waveguide, the first integrated waveguide is adopted to realize conversion from a near-infrared band to a mid-infrared band frequency comb, the wavelength division multiplexing technology is combined to maximize the channel capacity, and then the second integrated waveguide is adopted to restore a near-infrared band optical signal. The problems of insufficient capacity, generation of attenuation and loss, low rate and the like when near-infrared band optical signals are transmitted in an atmospheric channel are avoided, space laser communication with the rate of Tbps magnitude is realized, an optical field can be restrained in a micro-nano waveguide structure to the greatest extent, and the frequency conversion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to a laser communication method and system, and in particular to a high-speed and large-capacity mid-infrared laser communication method and system based on an integrated waveguide. Background Art

[0002] With the continuous evolution and innovation of communication technologies, communication networks have profoundly affected various fields such as human clothing, food, housing, transportation, social entertainment, education, and scientific research. For space laser communication systems in different application scenarios, the choice of wavelength has a significant impact on system performance. For example, blue-green light is extremely prone to attenuation in the atmospheric channel, while it has better performance in underwater communication scenarios. Currently, in the application scenario of space laser communication in the atmosphere, the near-infrared C-band (~1550nm) is often selected as the carrier. However, compared with the mid-infrared band, the near-infrared band is easily affected by particulate scattering and atmospheric turbulence in the atmosphere, resulting in serious attenuation, wavefront distortion, and beam scintillation during signal transmission, thereby increasing the design complexity at the receiving end and reducing the stability of the communication link. In contrast, using the mid-infrared band as the carrier has obvious advantages when transmitting in space. For example, first, the mid-infrared band is less affected by the background noise of sunlight, reducing by about 80% compared with the near-infrared band. Second, the mid-infrared band is located in the atmospheric transmission window (such as: 3um). Due to its longer wavelength, the scattering effect of particulate matter on the light beam is very low. Third, the mid-infrared band has a higher transmittance, so it can transmit longer distances. Fourth, the mid-infrared band is less affected by phase distortion and intensity scintillation effects caused by atmospheric turbulence, and the scintillation index is lower than that of the near-infrared band, and the signal stability is relatively high, which is suitable for long-distance signal transmission.

[0003] However, in current actual laser communication systems, the maturity of mid-infrared band-related devices is relatively low, the technology development and manufacturing level have not reached an ideal level, and the costs of mid-infrared band-related devices are generally high, and the cost performance is low, which restricts the popularization and development of the mid-infrared band in practical applications. Therefore, based on the respective advantages of the near-infrared band and the mid-infrared band, some research institutions use bulk materials to achieve frequency conversion from the near-infrared band to the mid-infrared band, so that the mid-infrared band is used as the carrier for transmission. Although the mid-infrared band generated by the frequency conversion scheme based on bulk materials can assist in efficient space laser communication, it has bottlenecks such as large volume and low conversion efficiency of bulk materials. In addition, with the continuous improvement of communication requirements, the frequency conversion scheme based on bulk materials is also very difficult to meet the requirements of integration, miniaturization, or adaptation to an integrated optoelectronic platform. Summary of the Invention

[0004] The object of the present invention is to address the problem of high attenuation caused by atmospheric turbulence during the transmission of the near-infrared band in the atmosphere. At the same time, it aims to cope with the current situation where related devices in the mid-infrared band are not yet mature, the technology development and manufacturing level is limited, and the device cost is relatively high. In addition, when the existing space laser communication system uses the mid-infrared band for transmission, the frequency conversion scheme based on bulk materials has problems such as poor phase matching, large volume of bulk materials, and low conversion efficiency, which are difficult to meet the actual requirements of high-speed and large-capacity communication. The present invention provides a high-speed and large-capacity mid-infrared laser communication method and system based on an integrated waveguide.

[0005] To achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A high-speed and large-capacity mid-infrared laser communication method based on an integrated waveguide, characterized in that it includes the following steps:

[0007] Step 1: Use a continuous laser to generate signal light in the near-infrared band, and at the same time use femtosecond pulsed laser as pump light;

[0008] Step 2: Set a first integrated waveguide at the transmitting end and control the temperature of the first integrated waveguide to meet the temperature for frequency conversion; input the near-infrared band signal light and pump light into the first integrated waveguide, and generate a mid-infrared band frequency comb through the difference frequency effect;

[0009] Step 3: Separate the mid-infrared band frequency comb into multiple mid-infrared signal lights with different central wavelengths, and modulate the electrical signal to be transmitted onto the multiple mid-infrared signal lights with different central wavelengths; multiplex the modulated mid-infrared optical signal lights with different central wavelengths to form a high-speed optical signal in the mid-infrared band;

[0010] Step 4: Amplify the high-speed optical signal in the mid-infrared band, and transmit the amplified high-speed optical signal in the mid-infrared band to the transmitting antenna, and transmit it into space through the transmitting antenna;

[0011] Step 5: Set a second integrated waveguide and a second femtosecond pulsed laser at the receiving end, and control the temperature of the second integrated waveguide to meet the temperature for frequency conversion; receive the high-speed optical signal in the mid-infrared band in space through the receiving antenna, input the high-speed optical signal in the mid-infrared band received by the receiving antenna and the pump light generated by the second femtosecond pulsed laser into the second integrated waveguide, and restore the high-speed optical signal in the mid-infrared band to a near-infrared band optical signal through the second integrated waveguide;

[0012] Step 6: Amplify the restored near-infrared band optical signal, and then perform demultiplexing to separate the optical signal lights with different central wavelengths to obtain multiple amplified near-infrared band optical signals with different central wavelengths;

[0013] Step 7: Convert the amplified signals of near-infrared light with different central wavelengths into electrical signals and output them to the subsequent data recovery unit for data recovery.

[0014] Further, in Step 2, the first integrated waveguide is an integrated PPLN waveguide, and its polarization period Λ1 satisfies the quasi-phase matching condition of the following formula:

[0015]

[0016] where, K P1 is the wave vector of the femtosecond pulsed laser, K S1 is the wave vector of the signal light in the near-infrared band, K I1 is the wave vector of the idler light in the first integrated waveguide;

[0017] In Step 5, the second integrated waveguide is an integrated PPLN waveguide, and its polarization period Λ2 satisfies the quasi-phase matching condition of the following formula:

[0018]

[0019] where, K P2 is the wave vector of the pump light at the receiving end, K S2 is the wave vector of the high-speed optical signal in the mid-infrared band, K I2 is the wave vector of the idler light in the second integrated waveguide.

[0020] Further, in Step 2, before inputting the near-infrared band signal light and the pump light into the first integrated waveguide, adjust the polarization direction of the near-infrared band signal light through a polarizer to achieve the optimal frequency conversion efficiency of the first integrated waveguide. At the same time, control the delay time of the pump light through a delay line so that the near-infrared band signal light and the pump light coincide in the time domain.

[0021] Further, Step 3 is specifically as follows:

[0022] Step 3.1: Demultiplex the mid-infrared band frequency comb and separate it into multiple mid-infrared signal lights with different central wavelengths;

[0023] Step 3.2: Perform precoding on the electrical signal and modulate the precoded electrical signal onto multiple mid-infrared signal lights with different central wavelengths;

[0024] Step 3.3: Multiplex the modulated mid-infrared optical signals with different central wavelengths to form a high-speed optical signal in the mid-infrared band.

[0025] In addition, the present invention also provides a high-speed, high-capacity mid-infrared laser communication system based on an integrated waveguide, which is used to implement the above-mentioned high-speed, high-capacity mid-infrared laser communication method based on an integrated waveguide. The laser communication system includes a transmitting end and a receiving end. The special feature is that the transmitting end includes a continuous laser, a first femtosecond pulse laser, a first integrated waveguide, a signal source, an encoder, a wavelength division multiplexer, a first optical amplifier, and a transmitting antenna; the receiving end includes a receiving antenna, a second femtosecond pulse laser, a second integrated waveguide, a second optical amplifier, a wavelength division multiplexer, multiple photodetectors, and multiple data recovery units;

[0026] The continuous laser is used to emit near-infrared band signal light; the first femtosecond pulse laser is used to emit femtosecond pulse laser to serve as pump light;

[0027] The two input ends of the first integrated waveguide are respectively connected to the output end of the continuous laser and the output end of the first femtosecond pulse laser, so as to realize the difference frequency effect and generate a mid-infrared band frequency comb containing mid-infrared signal lights of multiple different central wavelengths;

[0028] The signal source is used to output the electrical signal to be transmitted; the input end of the encoder is connected to the output end of the signal source, and is used to pre-encode the electrical signal to be transmitted;

[0029] The wavelength division multiplexer includes a demultiplexer, a signal modulator, and a multiplexer; the input end of the demultiplexer is connected to the output end of the first integrated waveguide, and is used to demultiplex the mid-infrared band frequency comb and separate it into a plurality of mid-infrared signal lights with different center wavelengths; the input end of the signal modulator is respectively connected to the output end of the encoder and the output end of the demultiplexer, and is used to modulate the pre-coded electrical signal onto the mid-infrared signal lights with multiple center wavelengths; the input end of the multiplexer is connected to the output end of the signal modulator, and is used to multiplex the modulated mid-infrared light signals with multiple center wavelengths to form a high-speed optical signal in the mid-infrared band;

[0030] The input end of the first optical amplifier is connected to the output end of the multiplexer, and is used to amplify the mid-infrared band high-speed optical signal output by the multiplexer; the transmitting antenna is used to transmit the amplified mid-infrared band high-speed optical signal into space for transmission;

[0031] The receiving antenna is used to receive mid-infrared high-speed optical signals in space; the second femtosecond pulse laser is used to emit pump light;

[0032] The two input ends of the second integrated waveguide are respectively connected to the receiving antenna and the output end of the second femtosecond pulse laser, and are used to restore the mid-infrared band high-speed optical signal to a near-infrared band optical signal by the pump light emitted by the second femtosecond pulse laser; the input end of the second optical amplifier is connected to the output end of the second integrated waveguide, and is used to amplify the restored near-infrared band optical signal;

[0033] The input end of the wavelength demultiplexer is connected to the output end of the second optical amplifier, and is used to demultiplex the amplified near-infrared band optical signal, and separate and obtain multiple near-infrared band optical amplified signals with different central wavelengths;

[0034] The input ends of multiple photodetectors are respectively connected to the multiple output ends of the wavelength demultiplexer, and are used to convert the amplified near-infrared band optical signals with different central wavelengths into electrical signals; the input ends of multiple data recovery units are respectively connected to the output ends of the corresponding photodetectors, and are used to recover the data of the converted electrical signals;

[0035] On-chip temperature control devices are respectively integrated on the first integrated waveguide and the second integrated waveguide, and are used to heat the first integrated waveguide and the second integrated waveguide respectively to control the temperatures of the first integrated waveguide and the second integrated waveguide to meet the temperature for frequency conversion.

[0036] Further, both the first integrated waveguide and the second integrated waveguide are integrated PPLN waveguides;

[0037] The input and output of the first integrated waveguide and the second integrated waveguide are both fiber pluggable interfaces, and are used to realize a convenient and fast signal optical frequency conversion experiment;

[0038] The lengths of the first integrated waveguide and the second integrated waveguide are both centimeter-level, the widths are both micron-level, and the heights are both hundred-nanometer-level.

[0039] Further, digital temperature sensors are respectively integrated on the first integrated waveguide and the second integrated waveguide.

[0040] Further, a first erbium-doped fiber amplifier, a polarizer, a delay line and a second erbium-doped fiber amplifier are also included;

[0041] The input end of the first erbium-doped fiber amplifier is connected to the output end of the continuous laser, and is used to fiber-amplify the emitted near-infrared band signal light; the input end of the polarizer is connected to the output end of the first erbium-doped fiber amplifier, and is used to adjust the polarization direction of the near-infrared band signal light after fiber amplification, and its output end is connected to one input end of the first integrated waveguide;

[0042] The input end of the second erbium-doped fiber amplifier is connected to the output end of the first femtosecond pulse laser, and is used for fiber amplification of the emitted femtosecond pulse laser; the input end of the delay line is connected to the output end of the second erbium-doped fiber amplifier, and is used for adjusting the delay time of the femtosecond pulse laser after fiber amplification, and its output end is connected to another input end of the first integrated waveguide.

[0043] Furthermore, it further includes a plurality of filters;

[0044] The input ends of the plurality of filters are respectively connected to the plurality of output ends of the wavelength division demultiplexer, and are used for filtering the amplified signals of near-infrared band light with different central wavelengths, and their output ends are respectively connected to the input ends of the corresponding photodetectors.

[0045] Furthermore, the signal modulator adopts a Mach-Zehnder modulator; the wavelength division demultiplexer is a dense wavelength division multiplexer.

[0046] The beneficial effects of the present invention compared with the prior art are as follows:

[0047] 1. Compared with the existing frequency conversion scheme based on bulk materials, the high-speed large-capacity mid-infrared laser communication method based on an integrated waveguide provided by the present invention uses the first integrated waveguide to realize the conversion of the frequency comb from the near-infrared band to the mid-infrared band, and combines the wavelength division multiplexing technology to maximize the channel capacity, significantly improving the data transmission rate. Finally, the second integrated waveguide is used to restore the received mid-infrared band optical signal to a near-infrared band optical signal. On the one hand, it avoids problems such as insufficient capacity, attenuation and loss, and low rate encountered by near-infrared band optical signals during atmospheric channel transmission, and can realize space laser communication in the Gbps order of magnitude; on the other hand, the optical field can be maximally confined within the micro-nano waveguide structure, greatly weakening the phase matching condition and improving the conversion efficiency, and can be widely applied to high-speed large-capacity mid-infrared laser communication.

[0048] 2. The high-speed large-capacity mid-infrared laser communication system based on an integrated waveguide provided by the present invention cleverly utilizes the difference frequency effect of the first integrated waveguide to convert the near-infrared band signal light into mid-infrared band signal light, and then generates a mid-infrared band frequency comb with different central wavelengths. This mid-infrared band frequency comb generated by this scheme is suitable for space large-capacity communication and can resist atmospheric turbulence; at the same time, the sizes of the integrated first integrated waveguide and second integrated waveguide are small, making the mid-infrared band laser communication terminal have significant advantages in terms of SWaP (size, weight and power consumption). It can not only converge the optical field inside the waveguide, but also conveniently connect peripheral devices, greatly reducing the power consumption and volume, and is more suitable for emerging integrated optoelectronic platforms.

[0049] 3. Compared with the existing frequency conversion schemes based on bulk materials, during the conversion process, the high-speed and large-capacity mid-infrared laser communication system based on integrated PPLN waveguides of the present invention has a short response time, is transparent to modulation formats, and can be compatible with both intensity and phase modulation formats.

[0050] 4. The input and output of the first integrated waveguide and the second integrated waveguide in the present invention are both fiber pluggable interfaces, which are used to realize a convenient and fast signal light frequency conversion experiment. It does not require coupling various lasers during the experiment, effectively reducing the coupling loss. In addition, it is also connected to a peripheral temperature adjustment device through a pluggable interface to improve the frequency conversion efficiency.

[0051] 5. Considering that the optical performance of the integrated PPLN waveguide is extremely sensitive to temperature, the present invention is respectively provided with an on-chip temperature control device and a digital temperature sensor on the first integrated waveguide and the second integrated waveguide, which can control the temperatures of the first integrated waveguide and the second integrated waveguide to meet the frequency conversion requirements, so that the quasi-phase matching requirements can always be satisfied. Description of the Drawings

[0052] Figure 1 It is a schematic diagram of an embodiment of a high-speed and large-capacity mid-infrared laser communication system based on an integrated waveguide of the present invention.

[0053] Specific reference numerals are: 1 - continuous laser; 2 - first erbium-doped fiber amplifier; 3 - polarizer; 4 - first femtosecond pulse laser; 5 - second erbium-doped fiber amplifier; 6 - delay line; 7 - first integrated waveguide; 8 - wavelength division multiplexer, 81 - demultiplexer, 82 - signal modulator, 83 - multiplexer; 9 - first optical amplifier; 10 - transmitting antenna; 11 - receiving antenna; 12 - second femtosecond pulse laser; 13 - second integrated waveguide; 14 - second optical amplifier; 15 - wavelength demultiplexer; 16 - filter; 17 - photodetector; 18 - data recovery unit; 19 - signal source; 20 - encoder. Detailed Embodiments

[0054] To make the advantages and features of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments.

[0055] As Figure 1As shown in the figure, a high-speed and large-capacity mid-infrared laser communication system based on an integrated waveguide includes a transmitting end and a receiving end. Among them, the transmitting end includes a continuous laser 1, a first erbium-doped fiber amplifier 2, a polarizer 3, a first femtosecond pulse laser 4, a second erbium-doped fiber amplifier 5, a delay line 6, a first integrated waveguide 7, a signal source 19, an encoder 20, a wavelength division multiplexer 8, a first optical amplifier 9, and a transmitting antenna 10. The receiving end includes a receiving antenna 11, a femtosecond pulse laser 12, a second integrated waveguide 13, a second optical amplifier 14, a wavelength demultiplexer 15, six filters 16, six photodetectors 17, and six data recovery units 18.

[0056] The continuous laser 1 is used to emit signal light in the near-infrared band. In this embodiment, the wavelength of the signal light in the near-infrared band is 1550 nm. The input end of the first erbium-doped fiber amplifier 2 is connected to the output end of the continuous laser 1 and is used to perform fiber amplification on the emitted signal light in the near-infrared band. The input end of the polarizer 3 is connected to the output end of the first erbium-doped fiber amplifier 2 and is used to adjust the polarization direction of the signal light in the near-infrared band after fiber amplification to achieve the optimal frequency conversion efficiency of the first integrated waveguide.

[0057] In the present invention, a femtosecond pulse laser with a central wavelength in the nanometer range and a repetition frequency in the MHz range is used as the pump light. Therefore, the first femtosecond pulse laser 4 is used to generate a femtosecond pulse laser for use as the pump light. In this embodiment, a femtosecond pulse laser with a central wavelength of 1030 nm, a repetition frequency of 108.4 MHz, and a pulse width of 160 fs is used. The input end of the second erbium-doped fiber amplifier 5 is connected to the output end of the first femtosecond pulse laser 4 and is used to perform fiber amplification on the emitted femtosecond pulse laser. The input end of the delay line 6 is connected to the output end of the second erbium-doped fiber amplifier 5 and is used to adjust the delay time of the femtosecond pulse laser after fiber amplification to make the signal light in the near-infrared band coincide with the pump light in the time domain to improve the conversion efficiency and achieve an efficient difference frequency effect.

[0058] The first integrated waveguide 7 preferably integrates a PPLN waveguide, and its input and output are both fiber pluggable interfaces, and lasers can be directly connected to the corresponding interfaces. The two input ends of the first integrated waveguide 7 are respectively connected to the output end of the polarizer 3 and the output end of the delay line 6, and are used to generate a non-linear optical effect (difference frequency effect) between the signal light in the near-infrared band and the pump light in the integrated PPLN waveguide to generate an optical frequency comb covering the mid-infrared band with a pulse interval in the nanosecond range. The optical frequency comb in this embodiment includes six mid-infrared signal lights with different central wavelengths. The specific expression formula of the difference frequency effect is ω I =ω P- ω S where ω I is the angular frequency of the idler light in the first integrated waveguide 7, ω P is the angular frequency of the femtosecond pulse laser, ωS is the angular frequency of the signal light in the near-infrared band.

[0059] To achieve the frequency conversion process, the polarization period Λ1 of the first integrated waveguide 7 satisfies the quasi-phase matching condition of the following formula:

[0060]

[0061] where K P1 is the wave vector of the femtosecond pulsed laser, K S1 is the wave vector of the signal light in the near-infrared band, K I1 is the wave vector of the idler light in the first integrated waveguide; λ P1 is the wavelength of the femtosecond pulsed laser, λ S1 is the wavelength of the signal light, λ I1 is the wavelength of the idler light in the first integrated waveguide, and n is the effective refractive index.

[0062] Meanwhile, an on-chip temperature control device and a digital temperature sensor also need to be integrated on the first integrated waveguide 7 to control the temperature of the first integrated waveguide 7 to meet the frequency conversion requirement, so that the quasi-phase matching requirement can always be satisfied.

[0063] In this embodiment, the signal source 19 is used to output an electrical signal to be transmitted at 10 Gbps. The input end of the encoder 20 is connected to the output end of the signal source 19 and is used to precode the electrical signal to be transmitted at 10 Gbps.

[0064] The wavelength division multiplexer 8 is abbreviated as WDM, and it includes a demultiplexer 81 (DEMUX), a signal modulator 82, and a multiplexer 83 (MUX); the input end of the demultiplexer 81 is connected to the output end of the first integrated waveguide 7 and is used to demultiplex the mid-infrared frequency comb and separate it into mid-infrared signal lights with multiple different central wavelengths. In this embodiment, the signal modulator 82 uses a Mach-Zehnder modulator, and its input ends are respectively connected to the output end of the encoder 20 and the output end of the demultiplexer 81 and are used to modulate the pre-coded electrical signal onto the mid-infrared signal lights with multiple central wavelengths. The output end of the encoder 20 is used to modulate the pre-coded electrical signal onto the mid-infrared signal lights with multiple central wavelengths. The input end of the multiplexer 83 is connected to the output end of the signal modulator 82 and is used to multiplex the modulated mid-infrared optical signal lights with multiple different central wavelengths to form a high-speed optical signal in the mid-infrared band, enabling them to be transmitted in the optical fiber simultaneously and significantly improving the communication capacity and transmission rate.

[0065] The input end of the first optical amplifier 9 is connected to the output end of the multiplexer 85 and is used to amplify the high-speed optical signal in the mid-infrared band output by the multiplexer 85. The transmitting antenna 10 is used to transmit the amplified high-speed optical signal in the mid-infrared band into space for transmission.

[0066] A receiving antenna 11 for receiving high-speed mid-infrared band optical signals in space. A second femtosecond pulse laser 12 for generating pump light. The second integrated waveguide 13, like the first integrated waveguide 7, is an integrated PPLN waveguide, and both the input and output are fiber pluggable interfaces. The two input ends of the second integrated waveguide 13 are respectively connected to the output ends of the receiving antenna 11 and the second femtosecond pulse laser 12, and are used to restore the high-speed mid-infrared band optical signal received by the receiving antenna to a near-infrared band optical signal through the pump light emitted by the second femtosecond pulse laser 12. The polarization period Λ2 of the second integrated waveguide 13 satisfies the quasi-phase matching condition of the following formula:

[0067]

[0068] where K P2 is the wave vector of the pump light at the receiving end, K S2 is the wave vector of the mid-infrared band optical signal, and K I2 is the wave vector of the idler light in the second integrated waveguide; λ P2 is the wavelength of the pump light at the receiving end, λ S2 is the wavelength of the mid-infrared band optical signal, λ I2 is the wavelength of the idler light in the second integrated waveguide, and n is the effective refractive index. Similarly, an on-chip temperature control device and a digital temperature sensor also need to be integrated on the second integrated waveguide 13 to control the temperature of the second integrated waveguide 13 to meet the frequency conversion requirement, so that the quasi-phase matching requirement can always be satisfied.

[0069] In addition, in order to effectively confine the optical field in the integrated PPLN waveguide, the size of the integrated PPLN waveguide is designed according to the effective mode field area obtained by finite-difference time-domain (FDTD) simulation, and it is determined that its size conditions should meet the requirements of centimeter-level length, micron-level width, and nanometer-level height. The size of the integrated PPLN waveguide is comparable to the wavelength of the near-infrared band signal light, which confines the optical field inside the integrated PPLN waveguide to the greatest extent, reduces optical field leakage, forms local field enhancement, and makes the frequency conversion process more efficient.

[0070] The input end of the second optical amplifier 14 is connected to the output end of the second integrated waveguide 13, and is used to amplify the restored near-infrared band optical signal. The wavelength division demultiplexer 15 is a dense wavelength division multiplexer DWDM for realizing the demultiplexing function. Its input end is connected to the output end of the second optical amplifier 14, and is used to demultiplex the amplified near-infrared band optical signal, so that the optical signals with different central wavelengths are separated to obtain six amplified near-infrared band optical signals with different central wavelengths.

[0071] The input ends of the six filters 16 are respectively connected to the six output ends of the wavelength demultiplexer 15, and are used for filtering the amplified optical signals in the near-infrared band with different central wavelengths. The input ends of the six photodetectors 17 are respectively connected to the output ends of the corresponding filters 16, and are used for converting the amplified optical signals in the near-infrared band with six different central wavelengths into electrical signals. The input ends of the six data recovery units 18 are respectively connected to the output ends of the corresponding photodetectors 17, and are used for data recovery of the converted electrical signals.

[0072] The high-speed large-capacity mid-infrared laser communication system based on an integrated waveguide of the present invention cleverly utilizes the difference frequency effect of the first integrated waveguide 7 to convert the signal optical light in the near-infrared band into signal optical light in the mid-infrared band, and then generates a mid-infrared band frequency comb with different central wavelengths. The mid-infrared band frequency comb generated by this solution is suitable for high-capacity space communication and can resist atmospheric turbulence. At the same time, the sizes of the integrated first integrated waveguide 2 and the second integrated waveguide 13 are small, so that the mid-infrared band laser communication terminal has significant advantages in terms of SWaP (size, weight, and power consumption). It can not only converge the optical field inside the waveguide, but also conveniently connect peripheral devices, greatly reducing power consumption and volume, and being more suitable for emerging integrated optoelectronic platforms. Compared with the existing frequency conversion scheme based on bulk materials, the high-speed large-capacity mid-infrared laser communication system based on an integrated PPLN waveguide of the present invention has a short response time and is transparent to modulation formats during the conversion process, and can be compatible with intensity and phase modulation formats.

[0073] The communication method using the above-mentioned high-speed large-capacity mid-infrared laser communication system based on an integrated waveguide specifically includes the following steps:

[0074] Step 1, the near-infrared band signal optical light with a wavelength of 1550 nm emitted by the continuous laser 1 is fiber-amplified and used as the carrier for space laser communication. At the same time, the femtosecond pulsed laser with a central wavelength of 1030 nm, a repetition frequency of 108.4 MHz, and a pulse width of 160 fs emitted by the first femtosecond pulsed laser 4 is fiber-amplified and used as the pump light.

[0075] Step 2, through the on-chip temperature control device and the digital temperature sensor on the first integrated waveguide 7, control the temperature of the first integrated waveguide 7 to meet the requirements of frequency conversion; input the near-infrared band signal optical light and the pump light into the first integrated waveguide 7, and generate a mid-infrared band frequency comb containing six mid-infrared signal optical lights with different central wavelengths through the difference frequency effect.

[0076] At this time, the polarization direction of the near-infrared band signal optical light after fiber amplification can be adjusted through the polarizer 3 to achieve the optimal frequency conversion efficiency of the first integrated waveguide 7; at the same time, the delay time of the femtosecond pulsed laser after fiber amplification is accurately controlled through the delay line 6, so that the near-infrared band signal optical light and the pump light coincide in the time domain.

[0077] Step 3: First, demultiplex the mid-infrared band frequency comb by the demultiplexer 81 to separate it into mid-infrared signal lights with six different central wavelengths. Then, precode the 10 Gbps electrical signal to be transmitted output by the signal source 19 by the encoder 20, and modulate the precoded electrical signal onto the mid-infrared signal lights with six different central wavelengths. Finally, multiplex the modulated mid-infrared optical signal lights with six different central wavelengths by the multiplexer 83 to form a high-speed mid-infrared band optical signal with a wavelength of 1550 nm.

[0078] Integrate and multiplex the mid-infrared band frequency comb containing mid-infrared optical signal lights with six different central wavelengths through the wavelength division multiplexer 8, so that it forms a high-speed mid-infrared band optical signal carrying a 6×10 Gbps signal and transmits in the optical fiber.

[0079] Step 4: After the first optical amplifier 9 amplifies the high-speed mid-infrared band optical signal carrying a 6×10 Gbps signal, transmit it to the space for high-capacity wireless transmission through the transmitting antenna 10 at the transmitting end.

[0080] Step 5: Control the temperature of the second integrated waveguide 13 to meet the temperature for frequency conversion through the on-chip temperature control device and the digital temperature sensor on the second integrated waveguide 13. Receive the high-speed mid-infrared band optical signal in the space through the receiving antenna 11 at the receiving end; input the high-speed mid-infrared band optical signal received by the receiving antenna 11 and the pump light generated by the second femtosecond pulse laser 12, Pump into the second integrated waveguide 13, and restore the high-speed mid-infrared band optical signal to a near-infrared band optical signal through the second integrated waveguide 13.

[0081] Step 6: After amplifying the restored near-infrared band optical signal by the second optical amplifier 14, demultiplex it, so that the optical signal lights with six different central wavelengths are separated by the wavelength demultiplexer 15 to obtain near-infrared band optical amplified signals with six different central wavelengths.

[0082] Step 7: Filter the near-infrared band optical amplified signals with six different central wavelengths through six filters 16, and then convert them into electrical signals through the corresponding photodetectors 17 and output them to the subsequent data recovery unit 18 for data recovery.

[0083] The high-speed and large-capacity mid-infrared laser communication method based on an integrated waveguide provided by the present invention uses a first integrated waveguide 7 to achieve the conversion of a frequency comb from the near-infrared band to the mid-infrared band. At the same time, a second integrated waveguide 13 is used to restore the received mid-infrared band optical signal to a near-infrared band optical signal. On the one hand, it solves the problems such as insufficient capacity, attenuation and loss, and low rate encountered by near-infrared band optical signals during atmospheric channel transmission, and can achieve space laser communication at the Gbps level. On the other hand, the optical field can be maximally confined within the micro-nano waveguide structure, greatly weakening the phase matching condition and effectively improving the conversion efficiency. It can be widely applied to high-speed and large-capacity mid-infrared laser communication.

[0084] As described above, it is only used to illustrate the technical solution of the present invention and is not intended to limit it. For ordinary professional technicians in the field, the specific technical solution recorded in the above embodiments can be modified, or some of the technical features can be equivalently replaced. These modifications or replacements do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solution protected by the present invention.

Claims

1. A high-speed, high-capacity mid-infrared laser communication method based on integrated waveguides, characterized in that: It includes the following steps: Step 1: Use a continuous laser (1) to generate signal light in the near-infrared band, and at the same time use femtosecond pulsed laser as pump light; Step 2: Set a first integrated waveguide (7) at the transmitting end, and control the temperature of the first integrated waveguide (7) to meet the temperature for frequency conversion; input the near-infrared band signal light and pump light into the first integrated waveguide (7), and generate a mid-infrared band frequency comb through difference frequency effect; Step 3: Separate the mid-infrared band frequency comb into mid-infrared signal lights with multiple different central wavelengths, and modulate the electrical signal to be transmitted onto the mid-infrared signal lights with multiple different central wavelengths; multiplex the modulated mid-infrared optical signal lights with multiple different central wavelengths to form a high-speed optical signal in the mid-infrared band; Step 4: Amplify the high-speed optical signal in the mid-infrared band, and transmit the amplified high-speed optical signal in the mid-infrared band to the transmitting antenna (10), and transmit it into space through the transmitting antenna (10); Step 5: Set a second integrated waveguide (13) and a second femtosecond pulsed laser (12) at the receiving end, and control the temperature of the second integrated waveguide (13) to meet the temperature for frequency conversion; receive the high-speed optical signal in the mid-infrared band in space through the receiving antenna (11), input the high-speed optical signal in the mid-infrared band received by the receiving antenna (11) and the pump light generated by the second femtosecond pulsed laser (12) into the second integrated waveguide (13), and restore the high-speed optical signal in the mid-infrared band to a near-infrared band optical signal through the second integrated waveguide (13); Step 6: After amplifying the restored near-infrared band optical signal, perform demultiplexing to separate the optical signal lights with different central wavelengths, and obtain amplified near-infrared band optical signals with multiple different central wavelengths; Step 7: Convert the amplified near-infrared band optical signals with different central wavelengths into electrical signals and output them to the subsequent data recovery unit (18) for data recovery.

2. The high-speed large-capacity mid-infrared laser communication method based on an integrated waveguide according to claim 1, wherein: In step 2, the first integrated waveguide (7) is an integrated PPLN waveguide, and its polarization period Λ1 satisfies the quasi-phase matching condition of the following formula: Among them, K P1 is the wave vector of the femtosecond pulsed laser, K S1 is the wave vector of the signal light in the near-infrared band, and K I1 is the wave vector of the idler light in the first integrated waveguide (7); In step 5, the second integrated waveguide (13) is an integrated PPLN waveguide, and its polarization period Λ2 satisfies the quasi-phase matching condition of the following formula: Among them, K P2 is the wave vector of the pump light at the receiving end, K S2 is the wave vector of the high-speed optical signal in the mid-infrared band, K I2 is the wave vector of the idler light in the second integrated waveguide (13).

3. The high-speed large-capacity mid-infrared laser communication method based on an integrated waveguide according to claim 1 or 2, wherein: In step 2, before inputting the near-infrared band signal light and pump light into the first integrated waveguide (7), adjust the polarization direction of the near-infrared band signal light through a polarizer (3) to achieve the optimal frequency conversion efficiency of the first integrated waveguide (7), and at the same time control the delay time of the pump light through a delay line (6) to make the near-infrared band signal light and pump light coincide in the time domain.

4. The method for high-speed and high-capacity mid-infrared laser communication based on an integrated waveguide according to claim 3, wherein Step 3 specifically includes: Step 3.1: Demultiplex the mid-infrared band frequency comb to separate it into mid-infrared signal lights with multiple different central wavelengths; Step 3.2: Precode the electrical signal and modulate the pre-coded electrical signal onto the mid-infrared signal lights with multiple different central wavelengths; Step 3.3, multiplex the modulated mid-infrared optical signals with multiple different central wavelengths to form a high-speed optical signal in the mid-infrared band.

5. A high-speed and large-capacity mid-infrared laser communication system based on an integrated waveguide, which is used to implement the high-speed and large-capacity mid-infrared laser communication method based on an integrated waveguide according to any one of claims 1-4, including a transmitting end and a receiving end, and is characterized in that: The transmitting end includes a continuous laser (1), a first femtosecond pulse laser (4), a first integrated waveguide (7), a signal source (19), an encoder (20), a wavelength division multiplexer (8), a first optical amplifier (9), and a transmitting antenna (10); the receiving end includes a receiving antenna (11), a second femtosecond pulse laser (12), a second integrated waveguide (13), a second optical amplifier (14), a wavelength division demultiplexer (15), a plurality of photodetectors (17), and a plurality of data recovery units (18); The continuous laser (1) is used to emit signal light in the near-infrared band; the first femtosecond pulse laser (4) is used to emit femtosecond pulse laser as pump light; Two input ends of the first integrated waveguide (7) are respectively connected to the output end of the continuous laser (1) and the output end of the first femtosecond pulse laser (4), and are used to implement the difference frequency effect to generate a mid-infrared band frequency comb containing mid-infrared signal lights with multiple different central wavelengths; The signal source (19) is used to output an electrical signal to be transmitted; the input end of the encoder (20) is connected to the output end of the signal source (19), and is used to perform pre-coding on the electrical signal to be transmitted; The wavelength division multiplexer (8) includes a demultiplexer (81), a signal modulator (82), and a multiplexer (83); the input end of the demultiplexer (81) is connected to the output end of the first integrated waveguide (7), and is used to demultiplex the mid-infrared band frequency comb and separate it into mid-infrared signal lights with multiple different central wavelengths; the input ends of the signal modulator (82) are respectively connected to the output end of the encoder (20) and the output end of the demultiplexer (81), and are used to modulate the pre-coded electrical signal onto the mid-infrared signal lights with multiple central wavelengths; the input end of the multiplexer (83) is connected to the output end of the signal modulator (82), and is used to multiplex the modulated mid-infrared optical signals with multiple different central wavelengths to form a high-speed optical signal in the mid-infrared band; The input end of the first optical amplifier (9) is connected to the output end of the multiplexer (85), and is used to amplify the high-speed optical signal in the mid-infrared band output by the multiplexer (85); the transmitting antenna (10) is used to transmit the amplified high-speed optical signal in the mid-infrared band into space for transmission; The receiving antenna (11) is used to receive the high-speed optical signal in the mid-infrared band in space; the second femtosecond pulse laser (12) is used to emit pump light; The two input ends of the second integrated waveguide (13) are respectively connected to the output ends of the receiving antenna (11) and the second femtosecond pulse laser (12), and are used to restore the high-speed optical signal in the mid-infrared band to an optical signal in the near-infrared band by using the pump light emitted by the second femtosecond pulse laser (12); the input end of the second optical amplifier (14) is connected to the output end of the second integrated waveguide (13), and is used to amplify the restored optical signal in the near-infrared band. The input end of the wavelength division demultiplexer (15) is connected to the output end of the second optical amplifier (14), and is used to demultiplex the amplified optical signal in the near-infrared band, and separate and obtain multiple amplified optical signals in the near-infrared band with different central wavelengths. The input ends of multiple photodetectors (17) are respectively connected to multiple output ends of the wavelength division demultiplexer (15), and are used to convert the amplified optical signals in the near-infrared band with different central wavelengths into electrical signals; the input ends of multiple data recovery units (18) are respectively connected to the output ends of the corresponding photodetectors (17), and are used to recover data from the converted electrical signals. On-chip temperature control devices are respectively integrated on the first integrated waveguide (7) and the second integrated waveguide (13).

6. The high-speed large-capacity mid-infrared laser communication system based on an integrated waveguide according to claim 5, wherein: Both the first integrated waveguide (7) and the second integrated waveguide (13) are integrated PPLN waveguides. The input and output of both the first integrated waveguide (7) and the second integrated waveguide (13) are fiber pluggable interfaces. The lengths of both the first integrated waveguide (7) and the second integrated waveguide (13) are at the centimeter level, the widths are at the micron level, and the heights are at the hundred nanometer level.

7. The high-speed large-capacity mid-infrared laser communication system based on an integrated waveguide according to claim 6, wherein: Digital temperature sensors are respectively integrated on the first integrated waveguide (7) and the second integrated waveguide (13).

8. The high-speed large-capacity mid-infrared laser communication system based on an integrated waveguide according to any one of claims 5-7, wherein: It further includes a first erbium-doped fiber amplifier (2), a polarizer (3), a delay line (6), and a second erbium-doped fiber amplifier (5); the input end of the first erbium-doped fiber amplifier (2) is connected to the output end of the continuous laser (1), and is used to amplify the emitted near-infrared band signal light by fiber; the input end of the polarizer (3) is connected to the output end of the first erbium-doped fiber amplifier (2), and is used to adjust the polarization direction of the amplified near-infrared band signal light by fiber, and its output end is connected to one input end of the first integrated waveguide (7). The input end of the second erbium-doped fiber amplifier (5) is connected to the output end of the first femtosecond pulse laser (4), and is used to amplify the emitted femtosecond pulse laser by fiber; the input end of the delay line (6) is connected to the output end of the second erbium-doped fiber amplifier (5), and is used to adjust the delay time of the amplified femtosecond pulse laser by fiber, and its output end is connected to the other input end of the first integrated waveguide (7).

9. The integrated waveguide-based high-speed and high-capacity mid-infrared laser communication system according to claim 8, wherein: It further includes a plurality of filters (16); The input ends of the plurality of filters (16) are respectively connected to the output ends of the wavelength division demultiplexer (15) for filtering the amplified near-infrared band optical signals with different central wavelengths, and the output ends are respectively connected to the input ends of the corresponding photodetectors (17).

10. The integrated waveguide-based high-speed and high-capacity mid-infrared laser communication system according to claim 5, wherein: The signal modulator (20) uses a Mach-Zehnder modulator; The wavelength division demultiplexer (15) is a dense wavelength division multiplexer.

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