CN113922878A - A photon generator with anti-dispersive power attenuation and capable of switching multi-format chirped waveforms - Google Patents

Abstract

The invention relates to a photon generating device capable of resisting dispersion power attenuation and switching multi-format chirp waveforms, which comprises a laser, a dual-drive double-parallel Mach-Zehnder modulator (comprising a first sub-modulator and a second sub-modulator), a first 90-degree electric bridge, a second 90-degree electric bridge, a single-mode optical fiber, a band-pass filter, a photoelectric detector and a power supply control unit, wherein the dual-drive double-parallel Mach-Zehnder modulator comprises a first sub-modulator and a second sub-modulator; laser output by a laser is input into a main modulator, a radio frequency signal is divided into two paths with phase difference of 90 degrees by a first 90-degree electric bridge and respectively loaded on two radio frequency input ports of a first sub-modulator, a single chirp signal is divided into two paths with phase difference of 90 degrees by a second 90-degree electric bridge and respectively loaded on two radio frequency input ports of a second sub-modulator, and the main modulator is connected with a band-pass filter by a single-mode optical fiber and a photoelectric detector; and the power supply control unit controls the direct current bias point of the second double-parallel sub-modulator to work in a single sideband modulation mode, and the generation of the down-chirp, double-chirp and up-chirp waveforms is switched by adjusting the direct current bias points of the first sub-modulator and the main modulator.

Description

A photon generator capable of resisting dispersion power attenuation and switching multi-format chirped waveforms

technical field

The invention belongs to the technical field of microwave photonics, and in particular relates to a photon generating device which is resistant to dispersion power attenuation and can switch multi-format chirped waveforms.

Background technique

Linearly chirped microwave waveforms are widely used in radars to improve detection range and range resolution. Traditionally, linearly chirped microwave waveforms are generated electrically through a voltage-controlled oscillator. Linear Ramp Controlled Voltage or Direct Digital Synthesizer. However, the center frequency and bandwidth of the resulting signal are limited by electronic bottlenecks. Compared with the electrical method, the microwave chirp signal generated in the optical domain has the advantages of high instantaneous ultra-wideband, large spectral tuning range and strong anti-interference ability. So far, a large number of linearly chirped microwave waveform schemes based on microwave photonics have emerged. Such as frequency-time mapping and optical heterodyne.

In order to further improve the time-bandwidth product of the chirped radio frequency signal, those skilled in the art propose a method for frequency-bandwidth multiplication based on a frequency-sweeping photoelectric oscillator and using an external modulator. This is important in modern radar systems. However, the linearly chirped microwave waveform has a wide range of Doppler coupling knife edge fuzzy coupling. In order to overcome this deficiency, those skilled in the art propose a double-chirped microwave waveform composed of two linearly chirped complementary microwave waveforms. In some cases, sending a double-chirped microwave waveform is a better solution. However, in some scenarios, such as multi-function radar systems, switchable multi-format chirp waveforms are required in order to respond to different requirements, while the existing methods have complex structures and transmission is limited by the periodic power attenuation of the fiber.

In view of the above technical problems, the present invention improves them.

SUMMARY OF THE INVENTION

Based on the above-mentioned deficiencies in the prior art, the present invention provides a photon generating device with anti-dispersion power attenuation and switchable multi-format chirped waveforms.

In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A photon generating device capable of resisting dispersion power attenuation and capable of switching multi-format chirped waveforms, comprising a laser, a dual-drive dual-parallel Mach-Zehnder modulator (including sub-modulator 1, sub-modulator 2), a first 90° electrical bridge , the second 90° bridge, single-mode fiber, band-pass filter, photodetector, power control unit; the laser output from the laser input double-drive double-parallel Mach-Zehnder modulator, the RF signal is divided into the first 90° bridge The two channels with a phase difference of 90° are respectively loaded into the two RF input ports of sub-modulator 1, and the single chirp signal is divided into two channels with a phase difference of 90° through the second 90° bridge and loaded into the two RF input ports of sub-modulator 2 respectively. , the dual-drive dual-parallel Mach-Zehnder modulator is connected to the single-mode fiber, and the single-mode fiber is connected to the band-pass filter through the photodetector; the power control unit controls the DC bias point of the sub-modulator 2 to make it work in the single-sideband modulation In the mode, the generation of down-chirp, double-chirp and up-chirp waveforms can be switched by adjusting the DC bias points of the sub-modulator 1 and the main modulator, and the generated waveforms have the function of resisting dispersion power attenuation. The invention can realize anti-dispersion power attenuation and switchable multi-format chirp waveform generation, and is applied to the fields of multi-function radar and the like.

V_π为调制器的半波电压，即子调制器二工作在正交偏置点，偏置1、偏置3理想状态下根据需要的上啁啾、双啁啾或上啁啾波形来调节，由电源控制单元来控制输入。As a preferred solution, the dual-drive dual-parallel modulator has three DC bias inputs, wherein the input voltage under the ideal state of bias 2 is equal to

V _π is the half-wave voltage of the modulator, that is, the sub-modulator 2 works at the quadrature bias point, and the bias 1 and bias 3 are ideally adjusted according to the required up-chirp, double-chirp or up-chirp waveform. , the input is controlled by the power control unit.

和π；若要产生双啁啾波形，则偏置1、偏置3引起的相移分别为

和

m₁为射频信号的调制系数，J_n()表示第一类贝塞尔函数；若要产生上啁啾波形，则偏置1、偏置3引起的相移为

As a preferred solution, if a down chirp waveform is to be generated, the phase shifts caused by offset 1 and offset 3 are respectively

and π; if a double chirp waveform is to be generated, the phase shifts caused by offset 1 and offset 3 are respectively

and

m ₁ is the modulation coefficient of the radio frequency signal, and J _n ( ) represents the first-type Bessel function; if the up-chirp waveform is to be generated, the phase shift caused by offset 1 and offset 3 is

As a preferred solution, the 90° bridge actually plays the role of branching and phase shifting, and can also be replaced by other branching and phase-shifting devices.

As a preferred solution, the power control unit is an automatic bias point control circuit, and the power control unit can be composed of different adjustable DC voltage sources.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The switching between down chirp, double chirp and down chirp is accomplished by adjusting the DC bias point of the modulator, which is non-polarized and has a simple structure.

(2) Through the single-sideband modulation of the chirped signal, the signal power attenuation caused by the dispersion is eliminated.

Description of drawings

1 is a schematic diagram of the basic structure of a photon generating device that is resistant to dispersion power attenuation and can switch multi-format chirped waveforms of the present invention;

Fig. 2 is the time-domain waveform diagram, time-frequency diagram and electric spectrogram of the lower chirp, double chirp and upper chirp waveform generated by the implementation of the present invention;

3 is a time-frequency diagram and an electrical spectrogram of the lower chirp and double chirp generated by the implementation of the present invention, and the upper chirp waveform is transmitted through the optical fiber;

4 is a time-frequency diagram and an electrical spectrum diagram of the down-chirp, double-chirp, and up-chirp waveforms generated by the implementation of the present invention after passing through the attenuator with the same transmission loss as the optical fiber.

Detailed ways

In order to describe the embodiments of the present invention more clearly, the following will describe specific embodiments of the present invention with reference to the accompanying drawings.

As shown in FIG. 1, an embodiment of the present invention is a photon generating device that resists dispersion power attenuation and can switch multi-format chirped waveforms, which includes a laser 1, a dual-driven dual-parallel Mach-Zehnder modulator 2 (including a sub-modulator 2a) , sub-modulator 2b), the first 90° bridge 6, the second 90° bridge 7, the single-mode fiber 3, the photodetector 4, the band-pass filter 5, and the power control unit 8. The laser output from the laser 1 is input to the dual-drive dual-parallel Mach-Zehnder modulator 2, and the RF signal is divided into two channels with a phase difference of 90° through the first 90° bridge 6, and the upper and lower RF input ports of the sub-modulator 2a are respectively loaded, with a single chirp. The signal is divided into two channels with a phase difference of 90° through the second 90° bridge 7 and loaded into the upper and lower RF input ports of the sub-modulator 2b; The bandpass filter 5 is connected through the photodetector 4; the power supply control unit 8 controls the DC bias point of the sub-modulator 2b to make it work in the single-sideband modulation mode, and adjusts the DC bias of the sub-modulator 2a and the main modulator 2 by adjusting the DC bias point of the sub-modulator 2b. The bias point is used to switch the generation of down-chirp, double-chirp, and up-chirp waveforms, and the generated waveforms have the function of resisting dispersion power attenuation.

In this embodiment, the 90° bridge plays the role of shunt and phase shift, which can be replaced by other shunt and phase shift devices. The power control unit is an automatic control circuit of the bias point, and the power control unit can be composed of different adjustable DC voltage sources.

V_π为调制器的半波电压，也就是子调制器2a工作在正交偏置点，偏置1、偏置3理想状态下根据需要的上啁啾、双啁啾或上啁啾波形来调节，由电源控制单元8来控制输入。Dual Drive Dual Parallel Modulator 2 has three DC bias inputs, where the ideal input voltage for Bias 2 is equal to

V _π is the half-wave voltage of the modulator, that is, the sub-modulator 2a works at the quadrature bias point, and the bias 1 and bias 3 are ideally determined according to the required up-chirp, double-chirp or up-chirp waveform. Regulation, the input is controlled by the power supply control unit 8 .

和π；若要产生双啁啾波形，则偏置1、偏置3引起的相移分别为

和

m₁为射频信号的调制系数，J_n()表示第一类贝塞尔函数；若要产生上啁啾波形，则偏置1、偏置3引起的相移为

To generate a down-chirp waveform, the phase shifts caused by offset 1 and offset 3 are respectively

and π; if a double chirp waveform is to be generated, the phase shifts caused by offset 1 and offset 3 are respectively

and

m ₁ is the modulation coefficient of the radio frequency signal, and J _n ( ) represents the first-type Bessel function; if the up-chirp waveform is to be generated, the phase shift caused by offset 1 and offset 3 is

E₀和ω₀分别为激光信号幅度和角频率，射频信号为V₁ cos(ω₁t),V₁和ω₁分别为射频信号振幅和角频率，单啁啾信号为V₂ cos(ω₂t+kt²),V₂、ω₂和k分别为单啁啾信号的振幅、角频率和啁啾率。The specific principle is described as follows: Assume that the light field of the input optical signal is

E ₀ and ω ₀ are the laser signal amplitude and angular frequency, respectively, the RF signal is V ₁ cos(ω ₁ t), V ₁ and ω ₁ are the RF signal amplitude and angular frequency, respectively, and the single-chirp signal is V ₂ cos(ω ₂ t+kt ² ), V ₂ , ω ₂ and k are the amplitude, angular frequency and chirp rate of the single chirp signal, respectively.

The optical field expression of the output optical signal from the sub-modulator 2a is:

为偏置1所造成的相移，m₁＝πV₁/V_π为射频信号的调制系数，J_n()表示第一类贝塞尔函数。in,

is the phase shift caused by the offset 1, m ₁ =πV ₁ /V _π is the modulation coefficient of the radio frequency signal, and J _n ( ) represents the first-type Bessel function.

The optical field expression of the output optical signal of the sub-modulator 2b is:

Wherein, m ₂ =πV ₂ /V _π is the modulation coefficient of the radio frequency signal.

Then the optical field expression of the output optical signal of the dual-drive dual-parallel Mach-Zehnder modulator is:

为偏置3所造成的相移。如果m₁＝m₂，ω₁＝2ω₂，双驱动双平行马赫曾德尔调制器输出的光信号的光场可以表示为：in,

is the phase shift due to offset 3. If m ₁ =m ₂ , ω ₁ =2ω ₂ , the optical field of the optical signal output by the dual-driven dual-parallel Mach-Zehnder modulator can be expressed as:

After long-distance optical fiber transmission, the optical field of the output optical signal can be expressed as

Among them, θ ₀ and θ _-1 are the phase shifts caused by the optical sideband dispersion of the optical carrier signal and -1-order single-chirp signal modulation, respectively, and γ ₁ and γ _-1 are the first-order and -1-order RF modulation optical edges, respectively. The phase shift caused by the band dispersion, applying Taylor's formula, according to the propagation constant β, can be obtained:

θ ₀ =Lβ ₀ (ω ₀ )

After passing through the photodetector, by using a bandpass filter, the signal can be filtered to contain only spectral components whose center frequency is at _ω2 , and the photocurrent can be expressed as

和

in,

and

时，输出的光电流可以表示为when

, the output photocurrent can be expressed as

i(t)∝J ₁ (m ₁ ) ² cos(ω ₂ t+kt ² +a ₁ +θ ₀ -θ _-1 )+J ₁ (m ₁ ) ² cos(ω ₂ t-kt ² +a ₃ +θ _-1 -γ _-1 )

时，输出的光电流可以表示为when

, the output photocurrent can be expressed as

i(t)∝J ₁ (m ₁ ) ² cos(ω ₂ t-kt ² +π+θ _-1 -γ _-1 )

时，输出的光电流可以表示为when

, the output photocurrent can be expressed as

可以生成一个下啁啾波形；当

时可以生成一个双啁啾波形；当

时，生成一个上啁啾波形。可以看出色散所引起的相移仅仅只影响了生成信号的相位而不是幅度。换句话说消除了下啁啾，双啁啾和上啁啾传输所引起的功率衰弱。It can be seen that when

A down-chirp waveform can be generated; when

can generate a double chirp waveform; when

, an up-chirp waveform is generated. It can be seen that the phase shift caused by dispersion only affects the phase and not the amplitude of the generated signal. In other words, the power degradation caused by down-chirp, double-chirp and up-chirp transmission is eliminated.

The invention can realize anti-dispersion power attenuation and switchable multi-format chirp waveform generation.

The above descriptions are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, but any equivalent modifications or changes made by those of ordinary skill in the art based on the contents disclosed in the present invention should be included in the within the scope of protection described in the claims.

Claims (5)

1. The photon generating device of anti-dispersion power weakening and capable of switching multi-format chirped waveforms is characterized in that the unit comprises a laser (1), a dual-drive dual-parallel Mach-Zehnder modulator (2), a single-mode fiber (3), a photoelectric detector (4), bandpass filter (5), first 90° bridge (6), second 90° bridge (7), power supply control unit (8); dual-drive dual-parallel Mach-Zehnder modulators (2) including sub-modulator one (2a) and sub-modulator two (2b); the laser output from the laser (1) is input into a dual-drive dual-parallel Mach-Zehnder modulator (2); the radio frequency signal passes through the first 90° electrical bridge (6) The two RF input ports of sub-modulator 1 (2a) are respectively loaded into two channels with a phase difference of 90°, and the single chirp signal is divided into two channels with a phase difference of 90° through the second 90° bridge (7) to be loaded respectively. to the two RF input ports of sub-modulator two (2b); the dual-drive dual-parallel Mach-Zehnder modulator (2) is connected to a single-mode fiber (3), and the single-mode fiber (3) is connected to the ribbon through a photodetector (4) pass filter (5); the power control unit (8) controls the DC bias point of the second sub-modulator (2b) to make it work in the single-sideband modulation mode, by adjusting the first sub-modulator (2a) and the dual-drive The DC bias point of the parallel Mach-Zehnder modulator (2) is used to switch the generation of the down-chirp, double-chirp, and up-chirp waveforms. 2. as claimed in claim 1, the photon generating device of anti-dispersion power weakening and capable of switching multi-format chirped waveform, is characterized in that, described double-drive double-parallel Mach-Zehnder modulator (2) has three DC bias inputs, where the input voltage in the ideal state of Bias 2 is equal to

V _π is the half-wave voltage of the modulator, that is, the sub-modulator 2 (2b) works at the quadrature bias point. Under the ideal state of bias 1 and bias 3, the up-chirp, double-chirp or up-chirp according to the needs The waveform is adjusted, and the input is controlled by the power control unit (8). 3. The photon generating device of anti-dispersion power weakening as claimed in claim 2 and capable of switching multi-format chirped waveforms, is characterized in that the phase shifts caused by bias 1 and bias 3 are respectively

and π, resulting in a down-chirp waveform; the phase shifts caused by offset 1 and offset 3 are respectively

and

m ₁ is the modulation coefficient of the radio frequency signal, J _n ( ) represents the first-type Bessel function, which generates a double-chirp waveform; the phase shift caused by offset 1 and offset 3 is

Generates an up-chirp waveform. 4. the photon generating device of anti-dispersion power weakening as described in any one of claim 1-3 and can switch multi-format chirped waveform, it is characterized in that, described power supply control unit (8) is bias point automatic control circuit . 5. The photon generating device with anti-dispersion power weakening and capable of switching multi-format chirped waveforms according to claim 4, characterized in that the power control unit (8) is composed of different adjustable DC voltage sources.

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