CN111447013B - Fourth-order ultra-wideband signal generation device based on microwave photonics - Google Patents

Abstract

A four-order ultra-wideband signal generation method and device based on microwave photonics belong to the technical field of microwave photonics. The device consists of a continuous wave laser, a polarization controller, an arbitrary waveform generator, an electric amplifier 1, an electric amplifier 2, an electric amplifier 3, an electric amplifier 4, a power divider 1, a power divider 2, a power divider 3, an electric delay line, a dual-polarization orthogonal phase shift keying modulator, a coupler, a direct current voltage stabilizing source 1, a direct current voltage stabilizing source 2, a direct current voltage stabilizing source 3, a direct current voltage stabilizing source 4, a direct current voltage stabilizing source 5, a direct current voltage stabilizing source 6, an optical delay line and a balanced photoelectric detector. By reasonably setting the operating point and the modulation index of the modulator, the generated ultra-wideband signal conforms to the power spectral density mask specified by the Federal communication Commission in the United states and has higher power efficiency. The device can realize two typical modulation modes used in communication, and therefore can be used as a signal source of an optical carrier ultra-wideband communication system.

Description

Fourth-order ultra-wideband signal generation device based on microwave photonics

technical field

The invention belongs to the technical field of microwave photonics, and in particular relates to a microwave photonics fourth-order ultra-wideband signal generation method and device based on a dual-polarization quadrature phase shift keying modulator and a delay line filter.

Background technique

With the continuous improvement of short-range broadband wireless communication requirements for high transmission rate and available radio frequency resources, UWB technology has attracted much attention due to its large bandwidth, high time domain resolution, anti-multipath fading and low power consumption. Therefore, UWB technology has application potential in many application fields, such as local area network, wide area network, sensing system and navigation system. The U.S. Federal Communications Commission regulates UWB signals: its relative bandwidth cannot be lower than 20%, or its 10dB bandwidth is greater than 500MHz. In addition, the frequency range from 3.1 to 10.6 GHz is allocated for wireless indoor communications, the so-called baseband ultra-wideband, whose power spectral density is limited to below -41.3dbm/MHz, also known as the ultra-wideband mask. Due to the limitation of UWB power spectral density, the transmission distance of UWB signals in the air is limited to within a few meters. In order to solve this problem, the light-borne ultra-broadband technology based on microwave photonics has been proposed. In this case, it is necessary to generate ultra-wideband signals in the optical domain, which can overcome the bandwidth limitation of electrical technology and omit redundant electro-optical conversion. In the optical carrier UWB network, the UWB signal is generated and modulated at the central station, and then transmitted to the base station through a long-distance optical fiber.

In order to fit the UWB mask to the greatest extent, that is, to generate an UWB signal with high power efficiency, there are generally two methods to achieve it. The first is to design a waveform that can fit the ultra-wideband mask, but the complex signals designed are usually generated by electrical devices, which is difficult to a certain extent, and the generated pulses are difficult to modulate. The second method is to perform high-order differentiation of Gaussian pulses to generate high-order UWB signals. This method can be implemented using optical devices, which can be flexibly modulated only by outputting encoded signals from an electrical pulse sequence generator.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and device for generating a microwave photonics fourth-order ultra-wideband signal based on a dual-polarization quadrature phase shift keying modulator and a delay line filter. By reasonably setting the operating point and modulation index of the modulator, the generated ultra-wideband signal can meet the power spectral density mask specified by the US Federal Communications Commission, and has high power efficiency. The device can realize two typical modulation modes used in communication, so it can be used as the signal source of the optical carrier ultra-wideband communication system.

The structure of the fourth-order ultra-wideband signal generator based on microwave photons according to the present invention is shown in FIG. Electric amplifier 4, power divider 1, power divider 2, power divider 3, electric delay line, dual polarization quadrature phase shift keying modulator, coupler, DC voltage regulator 1, DC voltage regulator 2 , DC voltage regulator source 3, DC voltage regulator source 4, DC voltage regulator source 5, DC voltage regulator source 6, optical delay line, balanced photodetector; dual-polarization quadrature phase shift keying modulator is integrated in A commercial device on a single chip consists of a Y-type beam splitter, a quadrature phase shift keying modulator 1, a quadrature phase shift keying modulator 2, a 90-degree polarization rotator, and a polarization beam combiner; The shift keying modulator 1 is composed of a Mach-Zehnder modulator 1a and a Mach-Zehnder modulator 1b embedded in the two arms of the female Mach-Zehnder modulator 1, an electric amplifier 1, a DC voltage stabilized source 1 and a Mach-Zehnder modulator 1a, the electric amplifier 2, the DC voltage regulator 2 are connected to the Mach-Zehnder modulator 1b, and the DC voltage regulator 3 is connected to the female Mach-Zehnder modulator 1; the quadrature phase shift keying modulator 2 is composed of The Mach-Zehnder modulator 2a and the Mach-Zehnder modulator 2b embedded in the two arms of the female Mach-Zehnder modulator 2 are formed. The electric amplifier 3 and the DC voltage stabilized source 4 are connected with the Mach-Zehnder modulator 2a. 4. The DC voltage stabilization source 5 is connected with the Mach Zehnder modulator 2b, and the DC voltage stabilization source 6 is connected with the female Mach Zehnder modulator 2.

V_π为调制器的半波电压)。当连续光信号输入到双极化正交相移键控调制器中时， Y型分光器将入射光信号分为功率、频率相等的第七支路光信号和第八支路光信号，第七支路光信号和第八支路光信号光功率约等于入射光信号的一半，频率等于入射光信号的频率。第七支路光信号输入到正交相移键控调制器1中，第三支路电信号和第四支路电信号分别经过电放大器1和电放大器2输入到马赫曾德尔调制器1a和马赫曾德尔调制器1b中；控制直流稳压源1、直流稳压源2和直流稳压源3的输出电压，使马赫曾德尔调制器1a工作在最小传输点，马赫曾德尔调制器1b和母马赫曾德尔调制器1工作在最大传输点；然后通过控制电放大器1、电放大器2来调整马赫曾德尔调制器1a的调制指数β_1a和马赫曾德尔调制器1b的调制指数β_1b，最后使得马赫曾德尔调制器1a输出一个正极性的高斯脉冲波形，使马赫曾德尔调制器1b输出负极性的双高斯脉冲波形(如图2(a)左侧所示)，从而在正交相移键控调制器1输出处结合得到一个正二阶超宽带光信号 (如图2(a)右侧所示)，然后进入到偏振合束器中；Continuous light output by a continuous wave laser (the laser output by a continuous wave laser is continuous, there will be no interruption, and the output power remains unchanged; since this optical signal has only a single frequency, the ideal waveform in the time domain is a sine wave) The input into the dual-polarization QPSK modulator is via a polarization controller, which is used to align the polarization state of the incident light with the principal axis of the dual-polarization QPSK modulator. At the same time, a series of Gaussian pulse electrical signals is output from the arbitrary waveform generator. First, the power divider 1 divides it into two first branch electrical signals and second branch electrical signals with equal amplitude, power and frequency. The frequency of the circuit electrical signal and the second branch electrical signal is the same as the frequency of the Gaussian pulse electrical signal output by the arbitrary waveform generator, and the power of the first branch electrical signal and the second branch electrical signal is about half of the power of the Gaussian pulse electrical signal; The second branch electrical signal is input to the incoming delay line, and the delay τ ₁ is introduced, and its amplitude, power and frequency remain unchanged, and the size of τ ₁ is approximately equal to half of the full width at half maximum of the input Gaussian pulse. Then the first branch electrical signal is subdivided into two third branch electrical signals and fourth branch electrical signals with equal amplitude, power and frequency through the power divider 2, the third branch electrical signal and the fourth branch electrical signal The power of the circuit electrical signal is approximately equal to half of the power of the first branch electrical signal, and the frequency is the same as the frequency of the Gaussian pulse electrical signal output by the arbitrary waveform generator. The second branch electrical signal is then divided into the fifth branch electrical signal and the sixth branch electrical signal with equal amplitude, power and frequency through the power divider 3, and the fifth branch electrical signal and the sixth branch electrical signal. The electrical signal power is approximately equal to half of the electrical signal power of the second branch, and the frequency is the same as the frequency of the Gaussian pulse electrical signal output by the arbitrary waveform generator. The electrical amplifier 1, the electrical amplifier 2, the electrical amplifier 3 and the electrical amplifier 4 are respectively introduced into the third branch electrical signal, the fourth branch electrical signal, the fifth branch electrical signal and the sixth branch electrical signal to adjust the The amplitudes of the branch electrical signals (V _1a , V _1b , V _2a , V _2b ), that is, adjusting the Mach-Zehnder modulator 1a, Mach-Zehnder modulator 1b, Mach-Zehnder modulator 2a, Mach-Zehnder modulator 2b The modulation index of (

V _π is the half-wave voltage of the modulator). When the continuous optical signal is input into the dual-polarization quadrature phase shift keying modulator, the Y-type optical splitter divides the incident optical signal into the seventh branch optical signal and the eighth branch optical signal with equal power and frequency. The optical power of the optical signal of the seventh branch and the optical signal of the eighth branch is approximately equal to half of the incident optical signal, and the frequency is equal to the frequency of the incident optical signal. The seventh branch optical signal is input into the quadrature phase shift keying modulator 1, and the third branch electrical signal and the fourth branch electrical signal are respectively input to the Mach-Zehnder modulator 1a and the fourth branch through the electrical amplifier 1 and the electrical amplifier 2. In Mach-Zehnder modulator 1b; control the output voltages of DC regulated source 1, DC regulated source 2 and DC regulated source 3, so that Mach-Zehnder modulator 1a works at the minimum transmission point, Mach-Zehnder modulator 1b and The female Mach-Zehnder modulator 1 works at the maximum transmission point; then the modulation index β 1a of the Mach-Zehnder modulator _1a and the modulation index β _1b of the Mach-Zehnder modulator 1b are adjusted by controlling the electric amplifier 1 and the electric amplifier 2, and finally Make the Mach-Zehnder modulator 1a output a positive-polarity Gaussian pulse waveform, and make the Mach-Zehnder modulator 1b output a negative-polarity double-Gaussian pulse waveform (as shown on the left side of Figure 2(a)), so that the quadrature phase shift The output of the keying modulator 1 is combined to obtain a positive second-order ultra-broadband optical signal (as shown on the right side of Figure 2(a)), and then enters the polarization beam combiner;

The optical signal of the eighth branch is input into the quadrature phase shift keying modulator 2, and the electrical signal of the fifth branch and the electrical signal of the sixth branch are respectively input to the Mach-Zehnder modulator 2a and the electrical amplifier 4 through the electric amplifier 3 and the electric amplifier 4. In the Mach-Zehnder modulator 2b; the output voltages of the DC voltage regulator source 4, the DC voltage regulator source 5 and the DC voltage regulator source 6 are controlled to make the Mach-Zehnder modulator 2b work at the minimum transmission point, and the Mach-Zehnder modulator 2a and The female Mach-Zehnder modulator 2 works at the maximum transmission point; by controlling the electric amplifier 3 and the electric amplifier 4, the modulation index β 2a of the Mach-Zehnder modulator _2a and the modulation index β _2b of the Mach-Zehnder modulator 2b are adjusted, and finally the The Mach-Zehnder modulator 2a outputs a negative-polarity Gaussian pulse waveform, so that the Mach-Zehnder modulator 2b outputs a positive-polarity double-Gaussian pulse waveform (as shown on the left side of Fig. 2(b)). Since the Mach-Zehnder modulator 2a and the The working transmission point of the Mach-Zehnder modulator 2b is opposite to that of the Mach-Zehnder modulator 1a and the Mach-Zehnder modulator 1b, so the output of the Mach-Zehnder modulator 2a and the Mach-Zehnder modulator 2b is the same as that of the Mach-Zehnder modulator 2b. The waveforms of the Del modulator 1a and the Mach-Zehnder modulator 1b are opposite, so that a negative second-order ultra-wideband optical signal with a delay of τ ₁ is obtained by combining at the output of the quadrature phase shift keying modulator 2 (as shown in Figure 2(b). ) shown on the right); then the polarization state of the negative second-order UWB optical signal is rotated 90 degrees by a 90-degree polarization rotator, so that its polarization state is orthogonal to that of the positive second-order UWB optical signal (eg Figure 2(c) is shown on the left), and then enters the polarization beam combiner; The broadband optical signal and the negative second-order ultra-broadband optical signal are combined, and then divided into the ninth branch optical signal and the tenth branch optical signal through the coupler, their power is about half of the original optical signal, and the frequency is equal to the original optical signal; The optical signals of the nine branches are input to the photodetector 1 in the balanced photodetector. After photoelectric conversion, the positive second-order ultra-broadband optical signal and the negative second-order ultra-broadband optical signal with opposite polarities are combined to generate a positive third-order ultra-broadband signal ( As shown in Figure 2(c)); the optical signal of the tenth branch is delayed by τ ₂ through the optical delay line, and the size of τ ₂ is approximately equal to half of the full width at half maximum of the input electric Gaussian pulse, and then input to the balanced photodetector The photodetector 2 in , after photoelectric conversion, generates a negative third-order ultra-wideband signal (as shown in Figure 2(d)); finally, at the output of the balanced photodetector, two positive third-order signals with opposite polarities are generated. The UWB signal and the negative third-order UWB signal are combined to generate a positive fourth-order UWB signal (as shown in Fig. 2(e)); a delay line filter composed of a balanced photodetector and an optical delay line acts as a first-order differential It is equivalent to the first-order differentiation of the third-order ultra-wide signal, thereby generating a positive fourth-order ultra-wideband signal; when the electrical delay line is changed from the first branch electrical signal to the second branch electrical signal, it can be Generating a negative fourth-order UWB signal, the principle of which is consistent with the principle of generating a positive fourth-order UWB signal, generates A schematic diagram of the negative fourth-order UWB signal process is shown in Fig. 2(f).

The frequencies of the 1st, 2nd, 3rd and 4th order UWB signals are the same, but the amplitude and power will be attenuated with the increase of the connected devices.

P_out表示生成的四阶超宽带信号频谱的功率密度，P_FCC表示超宽带掩模在 3.1到10.6GHz之间的功率密度。首先用Matlab建立了系统的数学模型，然后计算出在输入电高斯脉冲半高全宽不同的情况下，β_a＝1～3、β_b＝3～6(取值间隔 0.02)时输出的不同超宽带信号频谱的功率效率，然后绘制β_a、β_b、功率效率三者之间的三维曲线，并对超过超宽带掩模的频谱所计算的功率效率赋值为0。首先令电高斯脉冲的半高全宽为140ps，令电延时为60ps、光延时为60ps，得到如图3(a)所示的关系曲线，结果表明当调制指数为β_a＝1.74和β_b＝4.76时最佳功率效率为44.09％；令电高斯脉冲的半高全宽为128ps，令电延时为55ps、光延时为60ps，得到如图3(b)所示的关系曲线，结果表明当调制指数为β_a＝1.82和β_b＝ 4.72时最佳功率效率为51.12％；令电高斯脉冲的半高全宽为112ps，令电延时为 50ps、光延时为60ps，得到如图3(c)所示的关系曲线，结果表明当调制指数为β_a＝1.88和β_b＝4.48时最佳功率效率为54.16％；令电高斯脉冲的半高全宽为100ps，令电延时为50ps、光延时为50ps，得到如图3(d)所示的关系曲线，结果表明当调制指数为β_a＝2.56和β_b＝5.78时最佳功率效率为31.73％。通过比较得知，当任意波形发生器输出的电高斯脉冲的半高全宽为112ps，电延时为50ps，光延时为60ps，两个调制指数为1.88、4.88时可以获得理论最佳功率效率54.16％。在进行实验时，通过控制电放大器1、电放大器2、电放大器3、电放大器4使调制指数β_1a＝1.88、β_1b＝4.48、β_2a＝1.88、β_2b＝4.48，生成的四阶超宽带信号的功率效率为53.46％，接近理论分析值。In order to get the best power efficiency, the power efficiency and four modulation indices (β _1a , β _1b , β _2a , β _2b ), delay of electrical delay line, delay of optical delay line, arbitrary waveform generation are established The relationship between the full width at half maximum of the Gaussian pulse output by the device. Since the waveforms output by the QPSK modulator 1 and the QPSK modulator 2 are symmetrical, we make β _1a =β _2a =β _a , β _1b =β _2b =β _b . Since the delays of the electrical and optical delay lines are adjusted with the change of the full width at half maximum of the electrical Gaussian pulse, we establish the relationship between β _a and β _b and the power efficiency at different full widths at half maximum. The formula for calculating power efficiency is

_Pout denotes the power density of the generated fourth-order UWB signal spectrum, and _PFCC denotes the power density of the UWB mask between 3.1 and 10.6 GHz. Firstly, the mathematical model of the system is established with Matlab, and then the different ultra-widebands output when β _a = 1 to 3 and β _b = 3 to 6 (value interval 0.02) are calculated when the input electric Gaussian pulse is different in full width at half maximum. The power efficiency of the signal spectrum, then draw a three-dimensional curve between β _a , β _b , and the power efficiency, and assign a value of 0 to the calculated power efficiency for the spectrum that exceeds the UWB mask. First, let the full width at half maximum of the electric Gaussian pulse be 140ps, the electrical delay time is 60ps, and the optical delay time is 60ps, and the relationship curve shown in Figure 3(a) is obtained. The results show that when the modulation index is β _a = 1.74 and β _b = 4.76, the best power efficiency is 44.09%; the full width at half maximum of the electric Gaussian pulse is 128ps, the electrical delay is 55ps, and the optical delay is 60ps, and the relationship curve shown in Figure 3(b) is obtained. The results show that when When the modulation index is β _a = 1.82 and β _b = 4.72, the best power efficiency is 51.12%; let the full width at half maximum of the electric Gaussian pulse be 112ps, let the electric delay be 50ps, and the optical delay be 60ps, as shown in Figure 3(c ), the results show that the optimal power efficiency is 54.16% when the modulation index is β _a = 1.88 and β _b = 4.48; When the time is 50ps, the relationship curve shown in Fig. 3(d) is obtained. The result shows that the optimal power efficiency is 31.73% when the modulation index is β _a =2.56 and β _b =5.78. By comparison, it is known that when the full width at half maximum of the electrical Gaussian pulse output by the arbitrary waveform generator is 112ps, the electrical delay is 50ps, the optical delay is 60ps, and the two modulation indices are 1.88 and 4.88, the theoretical optimum power efficiency of 54.16 can be obtained. %. During the experiment, by controlling the electric amplifier 1, the electric amplifier 2, the electric amplifier 3, and the electric amplifier 4 so that the modulation indices β _1a =1.88, β _1b =4.48, β _2a =1.88, and β _2b =4.48, the generated fourth-order super The power efficiency of the broadband signal is 53.46%, which is close to the theoretical analysis value.

Finally, two typical communication modulation modes can be realized by changing the bit code sequence output by the arbitrary waveform generator: on-off keying modulation and pulse position modulation. The data encoding sequence is set as "110101". In order to realize on-off keying modulation, let the bit code sequence "0001000" output by the arbitrary waveform generator represent the data code "1", and let the bit code sequence "0000000" represent the data code "0". In order to realize pulse position modulation, let the bit sequence "0010000" represent the data "1", and let the bit sequence "0000100" represent the data "0". The successful realization of the two modulation modes proves that the device has the ability to be used as a signal source in a data communication system.

The invention selects a tunable laser with a wavelength of 1530nm to 1565nm as a continuous wave light source; the coupler is a 5:5 coupler; the bandwidth of the dual-polarization quadrature phase shift keying modulator is 23GHz; the bandwidth of the balanced photodetector is 22GHz; the maximum output bit rate of the arbitrary waveform generator can reach 65Gb/s; DC voltage regulator 1, DC voltage regulator 2, DC voltage regulator 3, DC voltage regulator 4, DC regulator source 5, DC regulator The amplitude of the output voltage of the source 6 is adjustable from 1V to 20V; the working bandwidth of the electrical delay line is 0～6GHz, the delay range is 0～635ps, and the adjustment precision is 5ps; the delay range of the optical delay line is 0～330ps, and the adjustment precision 0.001ps; the working bandwidth of power amplifier 1, power amplifier 2, power amplifier 3, and power amplifier 4 is 0~20GHz, and the gain adjustable range is 19dB~24dB; the work of power divider 1, power divider 2, power divider 3 The bandwidth is from 0 to 18 GHz. Features of the device of the present invention:

(1) An easy-to-integrate dual-polarization quadrature phase shift keying modulator and an easy-to-integrate balanced photodetector are used, and the device has a simple and compact structure, which is helpful to realize an integrated signal source in an optical-borne ultra-wideband communication system.

(2) A high-order ultra-wideband signal is generated, and by controlling the modulation index of the modulator, the spectrum of the generated ultra-wideband signal better fits the power spectral density mask specified by the FCC, and has a higher power efficiency.

(3) Two typical communication modulation modes can be realized, and the device can be used as a signal source of an optical carrier ultra-wideband communication system.

Description of drawings

Figure 1: Schematic diagram of the microwave photon fourth-order ultra-wideband signal generator;

Figure 2: Schematic diagram of the pulse shape generation process;

Figure 3: The relationship between modulation index and power efficiency, in the case of different full width at half maximum: (a) 140ps; (b) 128ps; (c) 112ps; (d) 100ps;

Figure 4: Generated third-order UWB signal;

Figure 5: Generated fourth-order UWB signal;

Figure 6: Two modulation formats implemented for code "110101": (a) on-off keying modulation; (b) pulse position modulation.

Detailed ways

Example 1:

The laser source is TSL-510 tunable laser from Santec Company, the wavelength range of the laser is 1510nm-1630nm; the polarization controller is the three-ring polarization controller of Sichuan Ziguan Company; the dual-polarization quadrature phase shift keying modulator is Fujitsu The company's FTM7977HQA, the bandwidth is 23GHz, the working light wavelength is 1530nm ~ 1610nm, and its half-wave voltage is 3.5V; the arbitrary waveform generator is Agilent's M8195A; DC voltage regulator 1, DC voltage regulator 2, DC voltage regulator Source 3, DC stabilized source 4, DC stabilized source 5, and DC stabilized source 6 are GPS-4303C from Guwei Company, and the output voltage range is adjustable from 1V to 20V; the balanced photodetector is DSC730 from Discoverysemi Company, The bandwidth is 22GHz; the spectrum analyzer is Agilent's N9010A, the measurement signal range bandwidth is 10Hz ~ 26.5GHz; the oscilloscope is Agilent's MSOV254A, the measurement signal bandwidth is 25GHz; the electrical delay line is GigaBaudics' PADL6, and the working bandwidth is 0 -6GHz, the delay range is 0-635ps, and the adjustment accuracy is 5ps; the optical delay line is a dimmable delay line of Sichuan Lightsos Photoelectric Technology Co., Ltd., the delay range is 0-330ps, and the adjustment accuracy is 0.001ps; electric amplifier 1 , Amplifier 2, Amplifier 3, Amplifier 4 are MD-20-M of Optilab Company, the working bandwidth is 0～20GHz, the gain adjustable range is 19dB～24dB; Device 3 is PE2084 of PASTERNACK Company, and its working bandwidth is 0-18GHz.

After the system is connected, turn on the switches of all instruments and equipment to make all the equipment in working state. First, the laser outputs an optical signal with a frequency of 193.414THz (corresponding to a wavelength of 1550nm), and its power is 11dBm. In the polarization quadrature phase shift keying modulator, it is divided into the seventh branch optical signal and the eighth branch optical signal with equal power by the Y-type optical splitter, and enter the quadrature phase shift keying modulator 1 and the quadrature optical signal respectively. Phase shift keying modulator 2. The bit rate of the electric Gaussian pulse sequence output by the arbitrary waveform generator is 10Gb/s, and it is output in the form of bit encoding with one "1" per 32 bits. The repetition rate corresponding to the electric Gaussian pulse is 312.5Mb/s. Set the output electric Gaussian pulse The full width at half maximum of the pulse is 112ps. The electrical Gaussian pulse signal output by the arbitrary waveform generator is input into the power divider 1, and is divided into a first branch electrical signal and a second branch electrical signal with equal amplitude, power and frequency, and the second branch electrical signal is connected to the electrical circuit. Delay line, set the delay of the electrical delay line to 50ps. The first branch electrical signal is further divided into the third branch electrical signal and the fourth branch electrical signal with equal amplitude, power and frequency through the power divider 2, and the third branch electrical signal enters the quadrature phase shift through the electrical amplifier 1 In the Mach-Zehnder modulator 1a of the keying modulator 1, the fourth branch electrical signal enters the Mach-Zehnder modulator 1b of the quadrature phase shift keying modulator 1 through the electric amplifier 2. The output voltage of the control DC voltage regulator 1 is 3.5V, and the output voltage of the DC voltage regulator source 2 and the DC voltage regulator source 3 is 0V. The electrical amplifier 1 and the electrical amplifier 2 are adjusted so that the modulation indices of the Mach-Zehnder modulator 1a and the Mach-Zehnder modulator 1b are close to the theoretical analysis values of 1.88 and 4.48. After the second branch electrical signal is output from the electrical delay line, it is delayed by 50ps, and is divided into the fifth branch electrical signal and the sixth branch electrical signal with equal amplitude, power and frequency by the power divider 3. The fifth branch electrical signal is The circuit electrical signal enters the Mach-Zehnder modulator 2a of the QPSK modulator 2 through the electrical amplifier 3, and the sixth branch electrical signal enters the Mach-Zehnder modulation of the QPSK modulator 2 through the electrical amplifier 4 device 2b. Then, the output voltage of the DC voltage regulator source 5 is controlled to be 3.5V, and the output voltage of the DC voltage regulator source 4 and the DC voltage regulator source 6 is 0V. The electrical amplifier 3 and the electrical amplifier 4 are adjusted so that the modulation indices of the Mach-Zehnder modulator 2a and the Mach-Zehnder modulator 2b are close to the theoretical analysis values of 1.88 and 4.48. The output optical signal of the dual-polarized quadrature phase shift keying modulator is input into the optical coupler, and the optical signal is divided into a ninth branch optical signal and a tenth branch optical signal with equal power. The optical signal of the ninth branch enters the photodetector 1 of the balanced photodetector, and outputs a positive third-order ultra-broadband waveform after photoelectric conversion (as shown in Fig. 4(a, b)). Fig. 4(a) is the time domain waveform of the generated positive third-order UWB signal, and Fig. 4(b) is the frequency spectrum of the positive third-order UWB signal. The optical signal of the tenth branch is input into the optical delay line, and the delay time of the optical delay line is set to 60ps, and then the optical signal output by the optical delay line enters the photodetector 2 of the balanced photodetector, and is output after photoelectric conversion. Negative third-order UWB signal (shown in Fig. 4(c,d)). Fig. 4(c) is the time domain waveform of the generated negative third-order UWB signal, and Fig. 4(d) is the frequency spectrum of the negative third-order UWB signal. After coupling the outputs of photodetector 1 and photodetector 2 in the balanced photodetector, the balanced photodetector outputs a positive fourth-order ultra-wideband signal (as shown in Figure 5(a,b)). Fig. 5(a) is the time domain waveform of the generated positive fourth-order UWB signal, whose full width at half maximum is 40ps, and the waveform has good symmetry. Figure 5(b) is the spectrum of the generated positive fourth-order UWB signal, its 10dB bandwidth is about 6.88GHz, its power efficiency is calculated to be 53.46%, close to the theoretical value, and there is no excess component in the low frequency band, which is a good fit UWB mask. When the electrical delay line is changed from the second branch electrical signal to the first branch electrical signal, a negative fourth-order ultra-wideband signal can be obtained at the output of the balanced photodetector (as shown in Fig. 5(c, d)) . Figure 5(c) is the generated negative fourth-order UWB signal time domain waveform. Figure 5(d) is the spectrum of the generated negative fourth-order UWB signal, which is almost identical to the spectrum of the positive fourth-order UWB signal, and fits well with the UWB mask.

Finally, in order to verify the application capability of the device in data communication systems, two typical modulation modes are implemented: on-off keying modulation and pulse position modulation. The output data encoding sequence is set as "110101". First of all, in order to realize on-off keying modulation, let the electric Gaussian pulse bit code sequence "0001000" output by the arbitrary waveform generator represent the data code "1", and let the bit code sequence "0000000" represent the data code "0". Set the bit code sequence output by the arbitrary waveform generator to "0001000 0001000 0000000 0001000 0000000 0001000", and the bit rate is 10Gb/s. Figure 6(a) shows the generated fourth-order UWB pulse sequence for on-off keying modulation. Then, in order to realize the pulse position modulation, let the bit sequence "0010000" represent the data "1", and let the bit sequence "0000100" represent the data "0". Set the bit code sequence output by the arbitrary waveform generator to "0010000 0010000 0000100 0010000 0000100 0010000", and the bit rate is 10Gb/s. Figure 6(b) shows the generated fourth-order UWB pulse sequence with pulse position modulation, and it can be seen that there is a clear difference between the pulse positions of "1" and "0". Therefore, the device can be used as a signal source in an optical carrier ultra-wideband communication system.

Claims (6)

1. a fourth-order ultra-wideband signal generator based on microwave photon, is characterized in that: by continuous wave laser, polarization controller, arbitrary waveform generator, electric amplifier 1, electric amplifier 2, electric amplifier 3, electric amplifier 4, Power divider 1, power divider 2, power divider 3, electrical delay line, dual polarized quadrature phase shift keying modulator, coupler, DC voltage regulator 1, DC voltage regulator 2, DC regulator Source 3, DC voltage regulator source 4, DC voltage regulator source 5, DC voltage regulator source 6, optical delay line, balanced photodetector; dual-polarization quadrature phase shift keying modulator is integrated on a single chip The commercial device is composed of a Y-type optical splitter, a quadrature phase shift keying modulator 1, a quadrature phase shift keying modulator 2, a 90-degree polarization rotator, and a polarization beam combiner; among them, the quadrature phase shift keying modulation The device 1 is composed of a Mach-Zehnder modulator 1a and a Mach-Zehnder modulator 1b embedded in the two arms of the female Mach-Zehnder modulator 1, and an electric amplifier 1 and a DC voltage stabilized source 1 are connected with the Mach-Zehnder modulator 1a. , the electric amplifier 2, the DC voltage regulator 2 are connected with the Mach Zehnder modulator 1b, the DC voltage regulator source 3 is connected with the female Mach Zehnder modulator 1; the quadrature phase shift keying modulator 2 is embedded in the female Mach The Mach-Zehnder modulator 2a and the Mach-Zehnder modulator 2b on the two arms of the Zehnder modulator 2 are formed. The electric amplifier 3 and the DC voltage stabilizer source 4 are connected to the Mach-Zehnder modulator 2a, and the electric amplifier 4 and the DC stabilizer are connected. The voltage source 5 is connected with the Mach-Zehnder modulator 2b, and the DC voltage-stabilized source 6 is connected with the female Mach-Zehnder modulator 2; The continuous light output by the continuous wave laser is input into the dual-polarization QPSK modulator through the polarization controller, and the polarization controller is used to compare the polarization state of the incident light with the dual-polarization QPSK modulator. The main axis is aligned; at the same time, a series of Gaussian pulse electrical signals is output from the arbitrary waveform generator, which is firstly divided into two first branch electrical signals and second branch electrical signals with equal amplitude, power and frequency by the power divider 1 , the frequencies of the first branch electrical signal and the second branch electrical signal are the same as the frequency of the Gaussian pulse electrical signal output by the arbitrary waveform generator, and the power of the first branch electrical signal and the second branch electrical signal is the Gaussian pulse electrical signal power The second branch electrical signal is input into the incoming delay line, and the delay τ ₁ is introduced, and its amplitude, power and frequency remain unchanged, and the size of τ ₁ is equal to half of the full width at half maximum of the input Gaussian pulse; then the first The branch electrical signal is subdivided into two third branch electrical signals and fourth branch electrical signals with equal amplitude, power and frequency through the power divider 2. The third branch electrical signal and the fourth branch electrical signal power It is equal to half of the power of the first branch electrical signal, and the frequency is the same as the frequency of the Gaussian pulse electrical signal output by the arbitrary waveform generator; then the second branch electrical signal is divided into two channels by the power divider 3, with equal amplitude, power and frequency The electrical signal of the fifth branch and the electrical signal of the sixth branch, the power of the electrical signal of the fifth branch and the electrical signal of the sixth branch is equal to half of the power of the electrical signal of the second branch, and the frequency is the same as the Gaussian pulse output by the arbitrary waveform generator The frequency of the electrical signal is the same; when the continuous optical signal is input into the dual-polarization quadrature phase shift keying modulator, the Y-type optical splitter divides the incident optical signal into the seventh branch optical signal and the eighth branch optical signal with equal power and frequency optical signal, the optical power of the seventh branch optical signal and the eighth branch optical signal is equal to half of the incident optical signal, and the frequency is equal to the frequency of the incident optical signal; the seventh branch optical signal is input to the quadrature phase shift keying modulator In 1, the electrical signal of the third branch and the electrical signal of the fourth branch are respectively input to the Mach-Zehnder modulator 1a and the Mach-Zehnder modulator 1b through the electrical amplifier 1 and the electrical amplifier 2; The output voltages of regulated source 2 and DC regulated source 3 make Mach-Zehnder modulator 1a work at the minimum transmission point, and Mach-Zehnder modulator 1b and female Mach-Zehnder modulator 1 work at the maximum transmission point; then by controlling The electrical amplifier 1 and the electrical amplifier 2 adjust the modulation index β 1a of the Mach-Zehnder modulator _1a and the modulation index β _1b of the Mach-Zehnder modulator 1b, and finally make the Mach-Zehnder modulator 1a output a positive Gaussian pulse waveform, Make the Mach-Zehnder modulator 1b output a negative-polarity double Gaussian pulse waveform, so as to combine at the output of the quadrature phase shift keying modulator 1 to obtain a positive second-order ultra-broadband optical signal, and then enter the polarization beam combiner; eighth The branch optical signal is input into the quadrature phase shift keying modulator 2, and the fifth branch electrical signal and the sixth branch electrical signal are input to the Mach-Zehnder modulator 2a and the Mach-Zehnder modulator 2a and the Mach-Zehnder through the electrical amplifier 3 and the electrical amplifier 4 respectively. In Del modulator 2b; control the output voltage of DC voltage regulator 4, DC voltage regulator 5 and DC voltage regulator 6 , so that the Mach-Zehnder modulator 2b works at the minimum transmission point, and the Mach-Zehnder modulator 2a and the female Mach-Zehnder modulator 2 work at the maximum transmission point; adjust the Mach-Zehnder modulator by controlling the electric amplifier 3 and the electric amplifier 4 The modulation index β 2a of _2a and the modulation index β _{2b of Mach-Zehnder modulator 2b} , finally make Mach-Zehnder modulator 2a output a negative-polarity Gaussian pulse waveform, and make Mach-Zehnder modulator 2b output a positive-polarity double Gaussian pulse waveform , since the working transmission points of Mach-Zehnder modulator 2a and Mach-Zehnder modulator 2b are opposite to those of Mach-Zehnder modulator 1a and Mach-Zehnder modulator 1b, so Mach-Zehnder modulator 2a and Mach-Zehnder modulator 2a and Mach-Zehnder modulator The output of the Mach-Zehnder modulator 2b is the opposite of that of the Mach-Zehnder modulator 1a and the Mach-Zehnder modulator 1b, which combine at the output of the QPSK modulator 2 to obtain a negative second-order superimposed delay τ ₁ . broadband optical signal; then the polarization state of the negative second-order ultra-broadband optical signal is rotated by 90 degrees by a 90-degree polarization rotator, so that its polarization state is orthogonal to that of the positive second-order ultra-broadband optical signal, and then enters the polarization state In the beam combiner; the positive second-order ultra-broadband optical signal and the negative second-order ultra-broadband optical signal output by the quadrature phase shift keying modulator 1 and the quadrature phase shift keying modulator 2 are combined through the polarization beam combiner, and then passed through The coupler is divided into the ninth branch optical signal and the tenth branch optical signal, their power is half of the original optical signal, and the frequency is equal to the original optical signal; the ninth branch optical signal is input to the photodetector in the balanced photodetector 1. After photoelectric conversion, the positive second-order ultra-broadband optical signal and the negative second-order ultra-broadband optical signal with opposite polarities are combined to generate a positive third-order ultra-broadband signal; the tenth branch optical signal is delayed by τ ₂ through the optical delay line , the size of τ ₂ is equal to half of the full width at half maximum of the input electric Gaussian pulse, and then input to the photodetector 2 in the balanced photodetector, after photoelectric conversion, a negative third-order ultra-wideband signal is generated; finally, in the balanced photodetector At the output end of the device, two positive third-order UWB signals and negative third-order UWB signals with opposite polarities are combined to generate a positive fourth-order UWB signal; the delay line filter composed of balanced photodetector and optical delay line is used as the The use of a first-order differentiator is equivalent to performing a first-order differentiation on a third-order ultra-wide signal, thereby generating a positive fourth-order ultra-wideband signal. 2. a kind of fourth-order ultra-wideband signal generating device based on microwave photons as claimed in claim 1, is characterized in that: selecting the tunable laser with wavelength of 1530nm～1565nm to make continuous wave light source; Coupler is the coupling of 5:5 The bandwidth of the dual-polarization quadrature phase shift keying modulator is 23GHz, and the bandwidth of the balanced photodetector is 22GHz; the output bit rate of the arbitrary waveform generator can reach up to 65Gb/s; Voltage source 2, DC voltage stabilizer source 3, DC voltage stabilizer source 4, DC voltage stabilizer source 5, and DC voltage stabilizer source 6 have an adjustable output voltage range of 1V to 20V; the working bandwidth of the electrical delay line is 0 to 6GHz. The delay range is 0~635ps, and the adjustment accuracy is 5ps; the delay range of the optical delay line is 0~330ps, and the adjustment accuracy is 0.001ps; the working bandwidth of the electric amplifier 1, electric amplifier 2, electric amplifier 3, electric amplifier 4 is 0 ~ 20GHz , the gain adjustable range is 19dB ~ 24dB; the working bandwidth of power divider 1, power divider 2, and power divider 3 is 0 ~ 18GHz. 3. a kind of fourth-order ultra-wideband signal generating device based on microwave photon as claimed in claim 1, is characterized in that: by controlling electric amplifier 1, electric amplifier 2, electric amplifier 3, electric amplifier 4, make modulation index β _1a = 1.88, β _1b =4.48, β _2a =1.88, β _2b =4.48, the power efficiency of the generated fourth-order UWB signal is 53.46%. 4. a kind of fourth-order ultra-wideband signal generating device based on microwave photon as claimed in claim 1, is characterized in that: when changing the electrical delay line from the first branch electrical signal to the second branch electrical signal, generate Negative fourth order UWB signal. 5. a kind of fourth-order ultra-wideband signal generating device based on microwave photon as claimed in claim 1,2,3 or 4, it is characterized in that: realize on-off keying modulation by changing the bit code sequence of arbitrary waveform generator output and pulse position modulation are two typical communication modulation modes. 6. a kind of fourth-order ultra-wideband signal generating device based on microwave photon as claimed in claim 5, it is characterized in that: make the bit code sequence " 0001000 " that the arbitrary waveform generator outputs represent data code " 1 ", let the bit code The sequence "0000000" represents the data code "0" to realize on-off keying modulation; the bit sequence "0010000" represents the data "1", and the bit sequence "0000100" represents the data "0" to realize the pulse position modulation.

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