Binary phase shift keying modulation method and system based on optical frequency comb

Abstract

The invention relates to a binary phase shift keying modulation method and system based on an optical frequency comb. The method comprises the steps that S1, the optical frequency comb and a to-be-modulated emission signal are acquired; s2, splitting a series of frequency components of the optical frequency comb through an array waveguide grating to obtain a plurality of monochromatic light carrier components; s3, performing collimation and power stabilization on each single-color carrier component to obtain a single-color light modulation carrier component; s4, taking each monochromatic light modulation carrier component as a sub-channel carrier channel, independently performing binary phase shift keying modulation on each transmitting signal to modulate the transmitting signal to the corresponding sub-channel carrier channel, and obtaining a modulated optical signal component; and S5, performing light combination processing on all the modulated light signal components through the array waveguide grating to obtain a spatial emission wavelength division multiplexing modulation signal. According to the invention, dense wavelength division multiplexing modulation emission optical link signals with more channels, wider modulation bandwidth, better channel synchronism and higher Doppler frequency shift consistency can be generated.

Description

Technical Field

[0001] The present invention relates to the field of new generation information technologies, and particularly to a binary phase shift keying modulation method and system based on an optical frequency comb. Background Art

[0002] With the rapid development of information and communication technologies (ICT), ultra-large bandwidth optical fiber communication and high-speed mobile access have attracted increasing attention in the industry. The integration of optical fiber technology and wireless technology is the future development direction of communication.

[0003] High-Speed Wavelength Division Multiplexing Laser Modulation is an important research direction in laser communication and integrated communication and navigation radars. In the prior art, to improve the capacity of laser communication, multiple independent lasers are required as modulation light sources, which results in high cost, large volume, and high power consumption of the light sources in the system. Moreover, the number of channels is difficult to flexibly control, and the channel spacing cannot be dynamically adjusted, which is not conducive to the expansion and reconstruction of the optical communication wavelength division multiplexing system. In addition, the wavelengths of the multi-carrier light sources composed of independent lasers are independent of each other, and it is difficult to ensure the stability of the center frequency and frequency spacing of the WDM channels. In the application scenario of low-earth orbit satellite optical communication, after multiple carriers undergo Doppler frequency shift, it poses a great challenge to the receiving terminal of coherent optical communication.

[0004] In addition, in the field of integrated laser communication and guidance communication, the current transmitting system generally consists of a monochromatic light source and a modulator. If wavelength division multiplexing technology is used to expand the transmitting channels, multiple monochromatic light sources are required to modulate the signals. There are not only problems of difficulty in multi-channel synchronization, but also the need to accurately calculate the Doppler frequency shift in space applications, and then calculate and adjust the transmitted modulation optical signal and the received modulation optical signal according to the Doppler frequency shift. When controlling multiple local oscillator lights, the Doppler frequency difference between multiple channels will increase due to the time delay of the control signal. Therefore, how to improve the problems of limited bandwidth improvement, difficulty in wavelength division multiplexing synchronization, and poor Doppler frequency shift consistency between multiple channels in the transmission of optical communication modulation signals is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] Aiming at the deficiencies of the above prior art, the technical problem to be solved by the present invention is: how to provide a binary phase shift keying modulation method based on an optical frequency comb, which can generate a dense wavelength division multiplexing modulation transmitted optical link signal with more channels, wider modulation bandwidth, better channel synchronization, and higher Doppler frequency shift consistency, so as to improve the problems of limited bandwidth improvement, difficulty in wavelength division multiplexing synchronization, and poor Doppler frequency shift consistency between multiple channels in the transmission of optical communication modulation signals.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A binary phase shift keying modulation method based on an optical frequency comb, characterized by comprising:

[0008] S1: Obtain an optical frequency comb and a plurality of transmission signals to be modulated;

[0009] S2: Split a series of frequency components of the optical frequency comb through an arrayed waveguide grating to obtain a plurality of monochromatic optical carrier components with equal wavelength intervals;

[0010] S3: Collimate and equalize the power of each monochromatic carrier component to obtain a monochromatic optical modulation carrier component;

[0011] S4: Use each monochromatic optical modulation carrier component as a sub-channel carrier channel, and modulate each transmission signal onto the corresponding sub-channel carrier channel through binary phase shift keying modulation to obtain a modulated optical signal component;

[0012] S5: Combine all the modulated optical signal components through an arrayed waveguide grating to obtain a spatially transmitted wavelength division multiplexing modulation signal as the input signal of the transmitting optical system.

[0013] Preferably, the optical frequency comb is an electro-optical frequency comb or a microcavity optical frequency comb;

[0014] The electro-optical frequency comb is a multi-wavelength light source with a repetition frequency greater than the modulation signal bandwidth, wherein the repetition frequency of the electro-optical frequency comb is not less than 20 GHz, the comb tooth line width is not greater than 100 KHz, and the number of comb teeth is not less than 50.

[0015] Preferably, the transmission signal is an analog signal obtained by processing a digital signal through constellation shaping, sequence and pilot insertion, and a digital-to-analog converter.

[0016] Preferably, the number of channel splittings of the arrayed waveguide grating matches the optical frequency comb, i.e., is not less than 40, the splitting flatness is less than 1 dB, the insertion loss is less than 10 dB, and the adjacent channel crosstalk is greater than 12 dB.

[0017] Preferably, collimate and equalize the power of each monochromatic carrier component through a collimator and a tunable optical attenuator respectively;

[0018] The tunable attenuation amount of the tunable optical attenuator is not less than 35 dB, the tunable step value is not greater than 0.1 dB, and the insertion loss is not greater than 1 dB.

[0019] Preferably, a single-arm Mach-Zehnder modulator is used to perform binary phase shift keying modulation on the transmission signal;

[0020] The modulation bandwidth of the single - arm Mach - Zehnder modulator is not less than 25 GHz, the insertion loss is not greater than 10 dB, and the half - wave drive voltage is not greater than 3.5 V.

[0021] Preferably, the single - arm Mach - Zehnder modulator includes two pairs of pins, namely the radio - frequency signal input terminal and the DC voltage bias terminal, where the transmitted signal is input through the radio - frequency signal input terminal;

[0022] The input of the single - arm Mach - Zehnder modulator is expressed as:

[0023]

[0024] The output of the single - arm Mach - Zehnder modulator is expressed as:

[0025]

[0026] In the formula: E in (t) represents the input optical signal of the single - arm Mach - Zehnder modulator, that is, the monochromatic light modulation carrier component; E out (t) represents the output optical signal of the single - arm Mach - Zehnder modulator, that is, the modulated optical signal component; E 0 represents the voltage amplitude of the input optical signal; ω 0 represents the angular velocity of the optical field of the input optical signal; represents the inherent phase change generated when two beams of light pass through two interference arms without applying voltage to the electrodes of the single - arm Mach - Zehnder modulator; represents the additional phase change generated in the optical path with electrodes after applying voltage to the electrodes of the single - arm Mach - Zehnder modulator.

[0027] Preferably, the output optical power of the single - arm Mach - Zehnder modulator is expressed as:

[0028]

[0029] In the formula: represents the optical field power of the input optical signal; represents the inherent phase difference of the single - arm Mach - Zehnder modulator.

[0030] An optical - frequency - comb - based binary phase - shift keying modulation system, implemented based on the binary phase - shift keying modulation method of the present invention, includes:

[0031] An input module, used to obtain an optical frequency comb and several transmitted signals to be modulated;

[0032] A beam splitter, used to split a series of frequency components of the optical frequency comb to obtain several monochromatic optical carrier components with equal wavelength intervals;

[0033] A collimator, used to collimate each monochromatic carrier component;

[0034] A tunable optical attenuator for power equalization of each single-color carrier component;

[0035] A single-arm Mach-Zehnder modulator for modulating each single-color optical carrier component into a sub-channel carrier channel, and modulating it onto the corresponding sub-channel carrier channel by performing binary phase shift keying modulation on each transmitted signal separately to obtain a modulated optical signal component;

[0036] An optical combiner for combining all the modulated optical signal components to obtain a spatially transmitted wavelength division multiplexing modulation signal;

[0037] A transmitting optical system for serving as an optical antenna system for the spatially transmitted wavelength division multiplexing modulation signal.

[0038] Preferably, the divergence angle of the transmitted beam of the transmitting optical system is less than 150 urad, and the optical transmittance is not less than 80%.

[0039] Compared with the prior art, the binary phase shift keying modulation method and system based on an optical frequency comb in the present invention have the following beneficial effects:

[0040] The present invention uses an electro-optical frequency comb as a modulation carrier, outputs multiple single-color optical carrier components with equal wavelength intervals through an arrayed waveguide grating (optical splitter), performs power equalization on the collimation and tunable attenuation link for each single-color optical carrier component, performs binary phase shift keying modulation with the transmitted signal in a single-arm Mach-Zehnder modulator, and finally combines multiple modulated optical signal components into one through an arrayed waveguide grating (optical combiner) to form a spatially transmitted wavelength division multiplexing modulation signal with an ultra-high signal rate (exceeding 400 Gbps). First, the present invention uses an electro-optical frequency comb as a modulation light source for dense wavelength division multiplexing, and can emit single-color local oscillator light with no less than 40 - 50 comb teeth, which can greatly increase the current number of wavelength division multiplexing channels and communication capacity. Second, the method of splitting the local oscillator light source through an arrayed waveguide grating of the electro-optical comb is used to improve the problems of local oscillator light source channel expansion and unified adjustment of Doppler frequency shift at the wavelength division multiplexing receiving end. Then, an optical frequency comb power equalization module is added to control the frequency flatness of each single-color carrier light source within ±0.5 dB, making the power of the modulated optical comb teeth more flat, realizing a multi-channel modulation multiplexing light source and a frequency-adjustable optical communication modulation multiplexing device, and the multiplexing channels can be expanded, so as to meet the requirements of large-capacity spatial communication wavelength division multiplexing modulation. In summary, compared with the existing methods, the binary phase shift keying modulation method based on an optical frequency comb in the present invention has the advantages of more signal channels in the dense wavelength division multiplexing modulation transmitting optical link, wider modulation bandwidth, better channel synchronization, and higher Doppler frequency shift consistency. Description of the Drawings

[0041] In order to make the objectives, technical solutions and advantages of the invention more clear, the following will further describe the present invention in detail with reference to the accompanying drawings, where:

[0042] Figure 1 It is a logic block diagram of a binary phase shift keying modulation method and system based on an optical frequency comb.

[0043] Figure 2 It is a hardware link diagram of binary phase shift keying modulation.

[0044] Figure 3 It is a schematic diagram of the principle of generating a binary phase shift keying modulation signal. Specific embodiments

[0045] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0046] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship in which the product of the invention is customarily placed. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive distinction and should not be construed as indicating or implying relative importance. In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "install", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] The following is a more detailed description through specific embodiments:

[0048] Embodiment 1:

[0049] A binary phase shift keying modulation method based on an optical frequency comb is disclosed in this embodiment.

[0050] As Figure 1 shown, the binary phase shift keying modulation (hereinafter also referred to as BPSK) method based on an optical frequency comb includes:

[0051] S1: Obtain an optical frequency comb and a plurality of transmission signals to be modulated;

[0052] S2: Split a series of frequency components of the optical frequency comb (hereinafter referred to as optical comb teeth) through an arrayed waveguide grating (AWG) to obtain a plurality of monochromatic optical carriers with equal wavelength intervals (showing a comb-like shape in the frequency domain);

[0053] S3: Collimate and equalize the power of each monochromatic carrier component to obtain 40 monochromatic optical modulation carrier components with a frequency flatness of no more than 0.2 dB, that is, optical comb teeth (the frequency domain of the monochromatic optical modulation carrier component is comb-shaped);

[0054] S4: Use each monochromatic optical modulation carrier component (optical comb tooth) as a sub-channel carrier channel, and modulate it onto the corresponding sub-channel carrier channel by performing binary phase shift keying modulation on each transmitted signal separately to obtain a modulated optical signal component, that is, a modulated optical comb tooth;

[0055] S5: Combine all the modulated optical signal components (modulated optical comb teeth) through an arrayed waveguide grating to obtain a spatially transmitted wavelength division multiplexing modulation signal, which is used as the input signal of the transmitting optical system.

[0056] The present invention uses an electro-optical frequency comb as a modulation carrier, outputs multiple monochromatic optical carrier components with equal wavelength intervals through an arrayed waveguide grating (optical splitter), collimates each monochromatic optical carrier component and equalizes the power of the adjustable attenuation link, performs binary phase shift keying modulation with the transmitted signal in a single-arm Mach-Zehnder modulator, and finally combines multiple modulated optical signal components into one through an arrayed waveguide grating (optical combiner) to form a spatially transmitted wavelength division multiplexing modulation signal with an ultra-high signal rate (exceeding 400 Gbps). First, the present invention uses an electro-optical frequency comb as a modulation light source for dense wavelength division multiplexing, and can emit monochromatic local oscillator light with no less than 40 - 50 comb teeth, which can greatly increase the current number of wavelength division multiplexing channels and communication capacity. Second, the problem of local oscillator light source channel expansion and unified adjustment of Doppler frequency shift at the wavelength division multiplexing receiving end is improved by the method of splitting the electro-optical comb through an arrayed waveguide grating. Then, an optical frequency comb power equalization module is added to control the frequency flatness of each monochromatic carrier light source within ±0.5 dB, making the power of the modulated optical comb teeth more flat, realizing a multi-channel modulation multiplexing light source and a frequency-adjustable optical communication modulation multiplexing device, and the multiplexing channels can be expanded, so as to meet the requirements of high-capacity spatial communication wavelength division multiplexing modulation. In summary, compared with the existing methods, the binary phase shift keying modulation method based on optical frequency comb in the present invention has the advantages of more signal channel numbers, wider modulation bandwidth, better channel synchronization, and higher Doppler frequency shift consistency in the dense wavelength division multiplexing modulation transmitting optical link.

[0057] In the specific implementation process, the optical frequency comb is an electro-optical frequency comb or a microcavity optical frequency comb;

[0058] An electro-optical frequency comb is a multi-wavelength light source with a repetition frequency greater than the modulation signal bandwidth. The repetition frequency of the electro-optical frequency comb is not less than 20 GHz, the linewidth of the comb teeth is not greater than 100 KHz, and the number of comb teeth is not less than 50. By setting the relevant parameters of the electro-optical frequency comb, it is possible to better split the light to obtain monochromatic optical carrier components, improving the effect of subsequent binary phase shift keying modulation.

[0059] The optical wavelength components of the electro-optical frequency comb are in the form of comb teeth evenly distributed at 10 GHz, so it can be used as a modulation carrier for dense wavelength division multiplexing. However, because the in-band flatness of the comb teeth is not good, it is necessary to use the comb tooth flattening function to adjust the amplitude of each monochromatic optical carrier. The amplitude fluctuation of the electro-optical frequency comb is greater than 20 dB, so the attenuation range of the 1-4 attenuators needs to be greater than 20 dB.

[0060] In the specific implementation process, the transmitted signal is an analog signal obtained after processing the digital signal through constellation shaping, sequence and pilot insertion, and digital-to-analog conversion.

[0061] In the specific implementation process, the number of channel splittings of the arrayed waveguide grating matches the optical frequency comb, that is, not less than 40, the splitting non-uniformity is less than 1 dB, the insertion loss is less than 10 dB, and the crosstalk between adjacent channels is greater than 12 dB. By setting the relevant parameters of the arrayed waveguide grating, it is possible to better split the optical frequency comb, improving the effect of subsequent binary phase shift keying modulation.

[0062] The arrayed waveguide grating uses PLC (planar lightwave circuit) technology, does not require additional power supply or temperature control, and belongs to a pure passive device. Compared with traditional TFF (thin film filter) products, the PLC process arrayed waveguide grating has higher integration, good uniformity, low PMD, and low insertion loss.

[0063] In the specific implementation process, the collimator and variable optical attenuator are used to collimate and flatten the power of each monochromatic carrier component respectively; due to the poor in-band flatness of the comb teeth of the electro-optical frequency comb, it is necessary to use the comb tooth flattening function to adjust the amplitude of each monochromatic optical carrier.

[0064] The adjustable attenuation of the variable optical attenuator is not less than 35 dB, the adjustable step value is not greater than 0.1 dB, and the insertion loss is not greater than 1 dB. By setting the relevant parameters of the variable optical attenuator, it is possible to better adjust the amplitude of each monochromatic optical carrier

[0065] In the specific implementation process, a single-arm Mach-Zehnder modulator is used to perform binary phase shift keying modulation on the transmitted signal;

[0066] The modulation bandwidth of the single - arm Mach - Zehnder modulator is not less than 25 GHz, the insertion loss is not greater than 10 dB, and the half - wave drive voltage is not greater than 3.5 V. By setting the relevant parameters of the single - arm Mach - Zehnder modulator, binary phase - shift keying modulation of the transmitted signal can be better performed.

[0067] Specifically, the input of the single - arm Mach - Zehnder modulator is expressed as:

[0068]

[0069] The output of the single - arm Mach - Zehnder modulator is expressed as:

[0070]

[0071] In the formula: E in (t) represents the input optical signal of the single - arm Mach - Zehnder modulator, that is, the monochromatic light modulation carrier component; E out (t) represents the output optical signal of the single - arm Mach - Zehnder modulator, that is, the modulated optical signal component; E 0 represents the voltage amplitude of the input optical signal; ω 0 represents the angular velocity of the optical field of the input optical signal; represents the inherent phase change generated when two beams of light pass through two interference arms without applying voltage to the electrodes of the single - arm Mach - Zehnder modulator; represents the additional phase change generated by the optical path with electrodes after applying voltage to the electrodes of the single - arm Mach - Zehnder modulator;

[0072] The single - arm Mach - Zehnder modulator includes two pairs of pins, namely the radio - frequency signal input terminal and the DC voltage bias terminal, and the transmitted signal is input through the radio - frequency signal input terminal.

[0073] The working logic of the single - arm Mach - Zehnder modulator includes:

[0074] 1) The input waveguide introduces the input optical signal into the modulator;

[0075] 2) The input optical signal is split into two beams by a beam splitter and enters two interference arms respectively (one interference arm is for modulation and the other is for reference);

[0076] 3) The modulation electrode applies an external electrical signal to modulate the phase or intensity of the optical signal through the electro - optic effect;

[0077] 4) The combiner recombines the two beams of light to form an interference output;

[0078] 5) The output waveguide outputs the modulated optical signal.

[0079] Specifically, the output optical power of the single - arm Mach - Zehnder modulator is expressed as:

[0080]

[0081] In the formula: represents the optical field power of the input optical signal; represents the inherent phase difference of the single-arm Mach-Zehnder modulator.

[0082] From the above two formulas, when θ 0 is 1 and -1, the output power P MZM (t) changes, and only the phase of the output optical field E out (t) changes, thereby realizing the BPSK modulation of the corresponding code elements "0" and "1". Figure 2 is the hardware link diagram for generating code elements. Among them, OSC provides the main working clock for the FPGA; FPGA (field programmable gate array, programmable logic device) is the main body of the modulation signal algorithm; OCXO is a temperature-controlled crystal oscillator and is the reference input part of the phase-locked loop; the phase-locked loop locks the frequency provided by the OCXO to the radio frequency frequency, and then provides a coherent clock for the FPGA and the DAC. The phase-locked loop can only generate one clock signal, and a clock distributor is required to divide it into multiple clock signals for the FPGA and the DAC; the high-speed digital-to-analog conversion device (JESD204C DAC) is a digital-to-analog converter and is the main device for generating modulation signals, responsible for converting the digital signals sent by the FPGA into analog modulation signals and sending them to the lithium niobate modulator.

[0083] The model selection of the devices in this embodiment:

[0084] The programmable logic device is XC7VSX690T.

[0085] The programmable logic device has 693,120 logic units, 350 available I / Os, and 36 groups of GTHs.

[0086] The ultra-high-speed digital-to-analog converter is Leia, with a conversion rate of 65 Gsps and a resolution of 8 bits.

[0087] The single-arm Mach-Zehnder modulator is PCO-1332, with a maximum modulation rate of up to 25 Gbps and a half-wave drive voltage of 3 V. The modulator drive is DR-DG-10-MO-NRZ, with a maximum output voltage of up to 9 V, a gain of 30 dB, and a rising edge of less than 14 ps.

[0088] The phase-locked loop is LMX2820, with a maximum output frequency of up to 22.6 GHz.

[0089] Combined with Figure 3As shown in the figure, the generation of the BPSK signal is divided into three parts: LDPC coding, BPSK constellation mapping, and carrier estimation. The input refers to the target signal to be transmitted, which is the signal to be sent, and the output refers to the data sent to the DAC after coding and carrier frequency offset estimation and compensation. The signal processing of the three parts is completed within the FPGA.

[0090] LDPC coding (Low-Density Parity-Check code) is a forward error correction code close to the Shannon limit, with low encoding and decoding complexity, suitable for hardware implementation, and capable of high-speed decoding. The LDPC code is defined by using a sparse parity-check matrix, and its encoding process involves a generator matrix, such that the information bits are multiplied by the generator matrix to obtain the encoded codeword. Carrier frequency offset estimation is to estimate the Doppler frequency shift amount of the relative motion in space and then compensate (fine-tune) the wavelength of the carrier light to make the data transmission more accurate.

[0091] Embodiment 2:

[0092] In this embodiment, an optical frequency comb-based binary phase shift keying modulation system is disclosed, which is implemented based on the binary phase shift keying modulation method of Embodiment 1.

[0093] The optical frequency comb-based binary phase shift keying modulation system includes:

[0094] An input module, configured to obtain an optical frequency comb and a plurality of transmission signals to be modulated;

[0095] A splitter, configured to split a series of frequency components of the optical frequency comb to obtain a plurality of monochromatic optical carrier components with equal wavelength intervals;

[0096] A collimator, configured to collimate each monochromatic carrier component;

[0097] An adjustable optical attenuator, configured to equalize the power of each monochromatic carrier component;

[0098] A single-arm Mach-Zehnder modulator, configured to modulate each monochromatic optical modulation carrier component into a sub-channel carrier channel, and modulate each transmission signal onto the corresponding sub-channel carrier channel through individual binary phase shift keying modulation to obtain modulated optical signal components;

[0099] A combiner, configured to combine all the modulated optical signal components to obtain a spatially transmitted wavelength division multiplexing modulation signal;

[0100] A transmitting optical system, configured to be an optical antenna system for the spatially transmitted wavelength division multiplexing modulation signal, which uses the same aperture for transmitting and receiving and realizes optical transmit-receive isolation by using an optical circulator.

[0101] In this embodiment, the emission beam divergence angle of the emission optical system is less than 150 urad, and the optical transmittance is not less than 80%. By setting the relevant parameters of the emission optical system, the emission of the spatial emission wavelength division multiplexing modulation signal can be better realized.

[0102] The present invention uses an electro-optical frequency comb as a modulation carrier, outputs multiple monochromatic optical carrier components with equal wavelength intervals through an arrayed waveguide grating (optical splitter), performs collimation and power equalization of the adjustable attenuation link on each monochromatic optical carrier component, performs binary phase shift keying modulation on the transmission signal in a single-arm Mach-Zehnder modulator, and finally combines multiple modulated optical signal components into one through an arrayed waveguide grating (optical combiner) to form a spatial emission wavelength division multiplexing modulation signal with an ultra-high signal rate (exceeding 400 Gbps). First, the present invention uses an electro-optical frequency comb as a modulation light source for dense wavelength division multiplexing, and can emit monochromatic local oscillator light with no less than 40 - 50 teeth, which can greatly increase the current number of wavelength division multiplexing channels and communication capacity. Second, the problem of local oscillator light source channel expansion and unified adjustment of Doppler frequency shift at the wavelength division multiplexing receiving end is improved by the method of splitting the electro-optical comb through an arrayed waveguide grating. Then, an optical frequency comb power equalization module is added to control the frequency flatness of each monochromatic carrier light source within ±0.5 dB, making the power of the modulated optical comb teeth more flat, realizing a multi-channel modulation multiplexing light source and a frequency-adjustable optical communication modulation multiplexing device, and the multiplexing channels can be expanded, so as to meet the requirements of large-capacity spatial communication wavelength division multiplexing modulation. In summary, compared with the existing methods, the binary phase shift keying modulation method based on an optical frequency comb in the present invention has the advantages of more signal channels in the emission optical link of dense wavelength division multiplexing modulation, wider modulation bandwidth, better channel synchronization, and higher Doppler frequency shift consistency.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those of ordinary skill in the art should understand that any modifications or equivalent replacements made to the technical solutions of the present invention without departing from the purpose and scope of the present technical solutions shall be covered by the scope of the claims of the present invention.

Claims

1. A binary phase shift keying modulation method based on optical frequency comb, characterized in that: include: S1: Obtain an optical frequency comb and several transmit signals to be modulated; S2: Splitting a series of frequency components of the optical frequency comb through an arrayed waveguide grating to obtain several monochromatic optical carrier waves with equal wavelength intervals; S3: collimating and power-smoothing each monochromatic carrier component to obtain a monochromatic light modulated carrier component; S4: taking each monochromatic light modulated carrier component as a subchannel carrier channel, and modulating each transmission signal to the corresponding subchannel carrier channel by performing binary phase shift keying modulation on each transmission signal separately, thereby obtaining a modulated optical signal component; S5: All modulated optical signal components are combined by arrayed waveguide grating to obtain a spatial transmission wavelength division multiplexing modulated signal as an input signal of the transmission optical system.

2. The binary phase shift keying modulation method based on optical frequency comb according to claim 1, characterized in that: In step S1, the optical frequency comb is an electro-optical frequency comb or a microcavity optical frequency comb; The electro-optical frequency comb is a multi-wavelength light source with a repetition frequency greater than a modulation signal bandwidth, wherein the repetition frequency of the electro-optical frequency comb is not less than 20 GHz, the comb tooth line width is not greater than 100 KHz, and the number of comb teeth is not less than 50.

3. The binary phase shift keying modulation method based on optical frequency comb according to claim 1, characterized in that: In step S1, the transmission signal is an analog signal obtained by processing the digital signal through constellation shaping, sequence and pilot insertion, and digital-to-analog converter.

4. The binary phase shift keying modulation method based on optical frequency comb according to claim 1, characterized in that: In step S2, the channel splitting number of the arrayed waveguide grating matches the optical frequency comb, that is, not less than 40, the splitting unevenness is less than 1 dB, the insertion loss is less than 10 dB, and the adjacent channel crosstalk is greater than 12 dB.

5. The binary phase shift keying modulation method based on optical frequency comb according to claim 1, characterized in that: In step S3, the monochromatic carrier components of each channel are collimated and power-leveled by a collimator and an adjustable optical attenuator respectively; The adjustable attenuation of the adjustable optical attenuator shall not be less than 35dB, the adjustable step value shall not be greater than 0.1dB, and the insertion loss shall not be greater than 1dB.

6. The binary phase shift keying modulation method based on optical frequency comb according to claim 1, characterized in that: In step S4, the transmission signal is subjected to binary phase shift keying modulation by a single-arm Mach-Zehnder modulator; The modulation bandwidth of the single-arm Mach-Zehnder modulator is not less than 25 GHz, the insertion loss is not greater than 10 dB, and the half-wave driving voltage is not greater than 3.5 V.

7. The binary phase shift keying modulation method based on optical frequency comb according to claim 6, characterized in that: The single-arm Mach-Zehnder modulator includes two pairs of pins, namely, a radio frequency signal input terminal and a direct current voltage bias terminal, wherein the transmission signal input is input through the radio frequency signal input terminal; The input of a single-arm Mach-Zehnder modulator is expressed as: The output of a single-arm Mach-Zehnder modulator is expressed as: Where: E in (t) represents the input optical signal of the single-arm Mach-Zehnder modulator, i.e., the monochromatic light modulated carrier component; E out (t) represents the output optical signal of the single-arm Mach-Zehnder modulator, i.e., the modulated optical signal component; E0 represents the voltage amplitude of the input optical signal; ω0 represents the angular velocity of the optical field of the input optical signal; It represents the inherent phase change of two light beams after passing through the two interference arms of a single-arm Mach-Zehnder modulator without applying voltage to the electrodes; It indicates the additional phase change produced by the light from the electrode after a voltage is applied to the electrode of a single-arm Mach-Zehnder modulator.

8. The binary phase shift keying modulation method based on optical frequency comb according to claim 7, characterized in that: The output optical power of a single-arm Mach-Zehnder modulator is expressed as: Where: Represents the optical field power of the input optical signal; represents the intrinsic phase difference of the single-arm Mach-Zehnder modulator.

9. A binary phase shift keying modulation system based on an optical frequency comb, characterized in that: The binary phase shift keying modulation method according to claim 1 is implemented, comprising: An input module, used to obtain an optical frequency comb and a plurality of transmit signals to be modulated; An optical splitter is used to split a series of frequency components of the optical frequency comb to obtain a number of monochromatic optical carrier waves with equal wavelength intervals; A collimator, used for collimating each monochromatic carrier component; An adjustable optical attenuator is used to smooth the power of each monochromatic carrier component; A single-arm Mach-Zehnder modulator is used to convert each monochromatic light modulated carrier component into a sub-channel carrier channel, and modulate each transmission signal to the corresponding sub-channel carrier channel by performing binary phase shift keying modulation on each transmission signal to obtain a modulated optical signal component; An optical combiner is used to combine all modulated optical signal components to obtain a spatial transmission wavelength division multiplexing modulated signal; The transmitting optical system is used as an optical antenna system for spatially transmitting wavelength division multiplexing modulated signals.

10. The binary phase shift keying modulation system based on optical frequency comb as claimed in claim 9, characterized in that: The emission beam divergence angle of the emission optical system is less than 150urad, and the optical transmittance is not less than 80%.

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