All-optical on-chip integrated arbitrary waveform generation device

Abstract

The invention discloses an all-optical arbitrary waveform generation device capable of being integrated on a chip. The device comprises an input end, an output end and a waveform generator unit. The input end of the first structure comprises a frequency modulation continuous wave source with high linearity and low noise; the waveform generator unit comprises two 1-N branch couplers, a plurality of Mach-Zehnder interferometers and a plurality of optical attenuators; and only one photoelectric detector is arranged at the output end. Linear and low-noise frequency-modulated continuous wave signals are firstly sent into different links formed by connecting Mach-Zehnder interferometers and optical attenuators in series through the 1-N branch couplers, signals with different amplitudes and different frequencies can be obtained after passing through the links, the signals are subsequently subjected to beam combination through the 1-N branch couplers, and by regulating and controlling the amplitudes and the frequencies of the signals, the frequency-modulated continuous wave signals with different amplitudes and different frequencies can be obtained. By means of the device, the synthesized arbitrary waveform can be dynamically adjusted, and meanwhile the device has the advantages of being high in integration, low in power consumption, small in size and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical signal processing, and in particular relates to an all-optical arbitrary waveform generating device that can be integrated on a chip. Background Art

[0002] At present, arbitrary waveform generators are mainly manufactured using technologies such as signal generation, digital signal processing, and analog output. In the process of signal generation, the arbitrary waveform generator generates a digital signal waveform through a built-in digital signal processor (DSP) or a programmable gate array (FPGA). Users can set waveform parameters such as frequency, amplitude, phase, etc. through the control panel or software interface on the device; in the process of digital signal processing, it mainly involves interpolation, filtering, transformation, and other operations on the generated waveform to ensure that the generated waveform meets the requirements set by the user; in order to generate analog output, the generated signal will finally undergo a digital-to-analog conversion process, and the digital-to-analog converter (DAC) can convert the digital signal into an analog signal, and the process will also amplify or reduce the analog signal to meet the requirements. The arbitrary waveform generated by this scheme is limited by the sampling rate and bandwidth of the digital-to-analog converter and the digital signal processor, respectively, which greatly limits the application of arbitrary waveforms in high-speed communication systems and complex waveform production. At the same time, the arbitrary waveform generator of the above scheme usually has a large volume and is expensive, which is not conducive to large-scale production and application. Summary of the invention

[0003] The purpose of the present invention is to solve the problem in the prior art that the sampling rate and bandwidth of arbitrary waveforms are limited by a digital-to-analog converter and a digital signal processor respectively.

[0004] To achieve the above-mentioned object, the present invention provides an all-optical on-chip integrated arbitrary waveform generating device, wherein the first structure of the device comprises an input end, a waveform generator unit and an output end; the input end is connected to the waveform generator unit; the waveform generator unit is connected to the output end;

[0005] The input end includes a linear, low-noise frequency-modulated continuous wave source; the waveform generator unit includes a 1-N branch coupler I, a 1-N branch coupler II, a number of Mach-Zehnder interferometers, a number of delay lines, and a number of adjustable optical attenuators; the output end includes a photodetector;

[0006] A linear, low-noise frequency-modulated continuous wave source is connected to an input end of a 1-N branch coupler I, an output end of the 1-N branch coupler I is connected to an input end of a Mach-Zehnder interferometer, the Mach-Zehnder interferometer is connected to an adjustable optical attenuator through a delay line, an output end of the adjustable optical attenuator is connected to an input end of a 1-N branch coupler II, and an output end of the 1-N branch coupler II is connected in series with a photodetector.

[0007] Furthermore, the Mach-Zehnder interferometer includes a delay line and two Y-type branch waveguide couplers, the two Y-type waveguides and the delay line are connected in series, the lengths of the delay lines in the Mach-Zehnder interferometer are inconsistent, and the design of the delay line lengths obeys an arithmetic progression or a geometric progression distribution, the delay line length setting of the arithmetic progression is used to synthesize a Gaussian pulse waveform; the delay line setting of the geometric progression is used to synthesize a triangular wave.

[0008] Furthermore, the adjustment amplitude ratio of the adjustable optical attenuator is from 0% to 100%.

[0009] The second structure of the device includes an input terminal, a waveform generator unit and an output terminal; the input terminal is connected to the waveform generator unit; the waveform generator unit is connected to the output terminal;

[0010] The input end includes a linear, low-noise frequency-modulated continuous wave source; the waveform generator unit includes an optical isolator, a straight waveguide, a ring waveguide, an adjustment electrode, and a coupler; the output end includes a photodetector; the linear, low-noise frequency-modulated continuous wave source is connected to the optical isolator, the optical isolator is directly connected in series with the straight waveguide, the straight waveguide and the ring waveguide are connected through a coupler, and the coupler and the photodetector are connected in series.

[0011] Furthermore, the ring waveguide and the straight waveguide are formed by connecting two Y-branch couplers.

[0012] Furthermore, the coupling coefficient between the straight waveguide and the ring waveguide is controlled by adjusting the electrodes.

[0013] Beneficial effects:

[0014] 1. The present invention provides an all-optical on-chip integrated arbitrary waveform generating device, which can dynamically adjust the synthesized arbitrary waveform, and the device also has the advantages of high integration, low power consumption, small size, large bandwidth, high speed, etc. The function of dynamically adjusting the synthesis of arbitrary waveforms is achieved by adjusting the amplitude and frequency of the synthesized waveform; high integration, small size, and low power consumption are the unique advantages of on-chip integrated devices; large bandwidth and high speed are the unique advantages of optical signals, and its vibration frequency determines that it can have a larger bandwidth and speed.

[0015] 2. The present invention proposes an all-optical on-chip integrated arbitrary waveform generation device, which includes two design methods. The first method uses a linear chirp source and a combination of multiple Mach-Zehnder interferometers to generate beat frequency signals of different amplitudes and frequencies, which can be combined and beat in a photodetector to achieve the generation of arbitrary waveforms. The second method uses a linear chirp and a straight waveguide-ring waveguide combination structure to generate a series of single-frequency signals with frequency amplitudes that decay in geometric series and frequencies that increase in an arithmetic progression, which can be beat in a photodetector to achieve the synthesis of a specified waveform. These two solutions have the advantages of high integration, low power consumption, and small size, and due to the unique advantages of optical frequency, they can also develop in the direction of large bandwidth and high sampling rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the first structure of the all-optical on-chip integrated arbitrary waveform generating device of the present invention;

[0017] Figure 2 This is the second structure of the all-optical on-chip integrated arbitrary waveform generating device of the present invention;

[0018] Figure 3 The simulation time domain result of the first structural implementation scheme of the present invention is a Gaussian pulse waveform with a pulse width of 0.5 μs;

[0019] Figure 4 The frequency domain results of the simulation of the first structural implementation scheme of the present invention are Gaussian pulse waveforms with a pulse width of 0.3 μs;

[0020] Figure 5 The frequency domain simulation result of the first structural implementation scheme of the present invention is a Gaussian pulse waveform with a pulse width of 0.1 μs;

[0021] Figure 6 The frequency domain results of the simulation for the first structural implementation scheme of the present invention are a triangular waveform with a period of 1 MHz;

[0022] Figure 7 The frequency domain results of the simulation of the first structural implementation scheme of the present invention are as follows: the power spectrum of a Gaussian pulse waveform with a pulse width of 0.5 μs;

[0023] Figure 8 The frequency domain results of the simulation of the first structural implementation scheme of the present invention are as follows: the power spectrum of a Gaussian pulse waveform with a pulse width of 0.3 μs;

[0024] Fig. 9 The frequency domain results of the simulation of the first structural implementation scheme of the present invention are as follows: the power spectrum of a Gaussian pulse waveform with a pulse width of 0.1 μs;

[0025] Fig.10 The frequency domain results of the simulation of the first structural implementation scheme of the present invention are the power spectrum of a triangle wave waveform with a period of 1 MHz.

[0026] Figure numerals: 1-linear, low-noise frequency-modulated continuous wave source, 2-1-N branch coupler I, 3-1-N branch coupler II, 4-Mach-Zehnder interferometer, 5-delay line, 6-adjustable optical attenuator, 7-photodetector; 8-optical isolator, 9-straight waveguide, 10-ring waveguide, 11-adjustment electrode, 12-coupler. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The application principle of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] Embodiment 1:

[0030] like Figure 1 As shown, an all-optical on-chip integrated arbitrary waveform generating device includes an input end, a waveform generator unit and an output end in a first structure. The input end is connected to the waveform generator unit; and the waveform generator unit is connected to the output end.

[0031] The input end includes a linear, low-noise frequency-modulated continuous wave source 1; the waveform generator unit includes a 1-N branch coupler I2, a 1-N branch coupler II3, a plurality of Mach-Zehnder interferometers 4, a plurality of delay lines 5, and a plurality of adjustable optical attenuators 6; and the output end includes a photodetector 7.

[0032] The linear, low-noise FM continuous wave source 1 uses an FM signal with a noise coefficient of 0.1% and absolute linearity for simulation. The linear, low-noise FM continuous wave source refers to a source with high frequency sweep linearity (nonlinearity <10 -8 ), a laser source with narrow line width (<20kHz). A linear, low-noise frequency modulated continuous wave source 1 is used to generate a high-quality frequency modulated continuous wave signal. A 1-N branch coupler I2 is used to equally divide the output power of the line frequency modulated continuous wave source; a 1-N branch coupler II3 is used to couple signals of different frequencies and amplitudes, wherein the number of N branches is 50 or 100. A Mach-Zehnder interferometer 4 and an adjustable optical attenuator 6 are combined to output signals of different frequencies and amplitudes.

[0033] The linear, low-noise frequency-modulated continuous wave source 1 is connected to the input end of the 1-N branch coupler I2, the output end of the 1-N branch coupler I2 is connected to the input end of the Mach-Zehnder interferometer 4, the Mach-Zehnder interferometer 4 is connected to the input end of the adjustable optical attenuator 6 through a delay line, the output end of the adjustable optical attenuator 6 is connected to the input end of the 1-N branch coupler II3, and the output end of the 1-N branch coupler II3 is connected in series with the photodetector 7. The signal output by the linear, low-noise frequency-modulated continuous wave source 1 is divided into N beams through the 1-N branch coupler I2, and each beam consists of a Mach-Zehnder interferometer 4 and an adjustable optical attenuator 6. The Mach-Zehnder interferometer 4 includes a delay line 5 and two Y-type branch waveguide couplers, and the length of the delay line 5 of each Mach-Zehnder interferometer 4 is inconsistent, and the two Y-type waveguides and the delay line 5 are connected in series. In this application, two delay line length schemes are designed in the form of arithmetic progression and geometric progression. The delay line length setting of the arithmetic progression is used to synthesize Gaussian pulse waveforms; the delay line setting of the geometric progression is used to synthesize triangular waves.

[0034] The adjustable optical attenuator 6 is used to adjust the amplitude of each optical beat signal. It can adjust the power of the input optical signal, and its adjustment ratio is 0% to 100%; the photodetector 7 is used to convert the combined optical beat signal into an arbitrary waveform signal. The bandwidth of the photodetector 7 is greater than the frequency of the arbitrary waveform signal. The bandwidth of the photodetector 7 needs to be designed according to the specific waveform. As shown in the simulation results, when a Gaussian pulse and a triangular waveform with a smaller repetition frequency are generated, the bandwidth of the photodetector 7 is set to 100MHz.

[0035] Working principle:

[0036] The linear, low-noise frequency-modulated continuous wave source generates a high-quality frequency-modulated optical signal, which is sent to the 1-N branch coupler I2 and evenly divided into N beams, and distributed to the Mach-Zehnder interferometer. Since the frequency-modulated optical signal has a certain sweep bandwidth, a beat signal with different frequency values ​​can be obtained after passing through the Mach-Zehnder interferometer. Then, the amplitude of the frequency signal can be adjusted by an optical attenuator. Subsequently, these beat signals with different frequency values ​​are combined through the 1-N branch coupler II3 and directly transmitted to the photodetector to produce arbitrary waveform signals.

[0037] Example 2

[0038] like Figure 2 As shown, the second structure includes an input terminal, a waveform generator unit and an output terminal. The input terminal is connected to the waveform generator unit; and the waveform generator unit is connected to the output terminal.

[0039] The input end includes a linear, low-noise frequency-modulated continuous wave source 1; the waveform generator unit includes an optical isolator 8, a straight waveguide 9, a ring waveguide 10, an adjustment electrode 11, and a coupler 12; and the output end includes a photodetector 7.

[0040] The linear, low-noise frequency-modulated continuous wave source 1 is connected to the optical isolator 8. The signal output by the linear, low-noise frequency-modulated continuous wave source 1 is transmitted to the straight waveguide 9 through the optical isolator 8, and then enters the ring waveguide 10. The optical signal undergoes different transmission circles in the ring waveguide and then converges in the photodetector 7. Among them, the linear, low-noise frequency-modulated continuous wave source 1, the optical isolator 8 and the straight waveguide 9 are directly connected in series. The straight waveguide 9 and the ring waveguide 10 are connected through the coupler 12, and the coupler 12 and the photodetector 7 are connected in series. The number of circles of the optical signal transmitted in the ring waveguide 10 can be effectively controlled by the adjustment electrode 11.

[0041] The optical isolator 8 is used to isolate the scattered light returned from the ring waveguide 10, which may interfere with the normal operation of the linear frequency modulation continuous wave source module.

[0042] The coupling between the straight waveguide 9 and the ring waveguide 10 is different from the coupling mode of the micro-ring. In the micro-ring resonator, the ring waveguide 10 and the straight waveguide 9 have critical coupling, over-coupling, under-coupling and the like. Different coupling modes can adjust the ring cavity coupling coefficient of the optical signal; the coupling is only a simple splitting effect, and the splitting ratio is changed by adjusting the electrode, so as to adjust the coupling loss of the straight waveguide and the ring waveguide. The structure of the ring waveguide 10 and the straight waveguide 9 is formed by docking two Y-branch couplers, and the adjusting electrode 11 is used to adjust the coupling coefficient between the straight waveguide 9 and the ring waveguide 10. The ring waveguide 10 will not have an ultra-high Q value.

[0043] The output of the linear, low-noise frequency-modulated continuous wave source 1 will output a series of signals with increasing frequency and decreasing power after passing through the structure of the ring waveguide 10 and the straight waveguide 9. The increasing frequency is due to the number of cycles of the propagating light field in the ring waveguide 10. The more cycles of the propagating light field in the ring waveguide 10, the higher the quality of the synthesized waveform; the decreasing power is due to the coupling coefficient between the straight waveguide 9 and the ring waveguide 10, and is also related to the waveguide loss of the ring waveguide 10 itself. The photodetector 7 is used to collect optical signals of different frequencies and amplitudes and convert them into arbitrary waveform signals.

[0044] Embodiment 3:

[0045] The light field output by a linear, low-noise frequency modulated continuous wave source can be expressed as:

[0046]

[0047] Where E is the output light field of the frequency modulated continuous wave source, is the amplitude of the output light field of the frequency modulated continuous wave source, f is the central frequency at time t = 0, ξ is the sweep speed, ψ is the nonlinear term of the sweep, is the phase noise term of the frequency modulated continuous wave source. In the theoretical modeling, the frequency sweep nonlinearity is set to 0, that is, ψ = 0; the phase noise is set to Gaussian white noise with a very small amplitude. The output light field of the delay arm in the Mach-Zehnder interferometer and the photocurrent of the beat signal passing through the photodetector can be expressed as (2) and (3):

[0048]

[0049] Among them, τ n represents the delay time corresponding to different delay line lengths, I represents the beat signal photocurrent, η is the imbalance between the two arms of the Mach-Zehnder interferometer, R is the sensitivity of the photodetector, P n is the light field amplitude output by different Mach-Zehnder interferometers, P n The size of is adjusted by the optical attenuator, i is the number of branches of the Mach-Zehnder interferometer, is the phase noise of the beat signal. The principle of arbitrary waveform synthesis can be expressed by equation (4):

[0050]

[0051] By adjusting the amplitude P n and the beat frequency ξτ n Different waveforms can be synthesized, ξτ n is the beat frequency, which can be adjusted by the delay line length. The synthesis of pulse signals requires that the beat frequency is equally spaced, that is, the frequency variable is an arithmetic progression, and when the amplitude gradually decays over time, it is a geometric progression. When the amplitude decays slowly, the pulse width is narrower; when the amplitude decays quickly, the pulse width is wider. The synthesis of triangle waves and square waves requires the frequency to increase exponentially.

[0052] like Figure 3-Figure 10 It is the time series and power spectrum of synthesized Gaussian pulse and triangle wave signals with different pulse widths. Its amplitude and frequency design calculation formulas are expressed by (5), (6), (7) and (8):

[0053] P Gaussianpulse =2*b n-1 [b=0.3,0.6,0.9] (5)

[0054] f Gaussianpulse =f0+(n-1)*f0[n=1,2,3…100] (6)

[0055] P triangular =2*b n-1 (7)

[0056] f triangular=f0+(n-1)*2f0[b=0.1] (8)

[0057] Where P Gaussianpulse is the amplitude sequence of Gaussian pulses, f Gaussianpulse is the frequency sequence of Gaussian pulses, P triangular is the amplitude sequence of the triangular wave signal, f triangular is the frequency sequence of the triangular wave signal, and b is a typical design parameter. As can be seen from the figure, whether it is a triangular wave or a Gaussian pulse, f0 represents the repetition frequency of the waveform. For a Gaussian pulse, the larger the b value, the slower the amplitude decays in the power spectrum, the more frequency components there are, and the narrower the width of the Gaussian pulse. For a triangular waveform, the b value needs to decay quickly and the frequency increases exponentially.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An all-optical on-chip integrated arbitrary waveform generating device, characterized in that: The first structure of the device includes an input terminal, a waveform generator unit and an output terminal; the input terminal is connected to the waveform generator unit; the waveform generator unit is connected to the output terminal; The input end includes a linear, low-noise frequency-modulated continuous wave source; the waveform generator unit includes a 1-N branch coupler I, a 1-N branch coupler II, a number of Mach-Zehnder interferometers, a number of delay lines, and a number of adjustable optical attenuators; the output end includes a photodetector; A linear, low-noise frequency-modulated continuous wave source is connected to an input end of a 1-N branch coupler I, an output end of the 1-N branch coupler I is connected to an input end of a Mach-Zehnder interferometer, the Mach-Zehnder interferometer is connected to an adjustable optical attenuator through a delay line, an output end of the adjustable optical attenuator is connected to an input end of a 1-N branch coupler II, and an output end of the 1-N branch coupler II is connected in series with a photodetector.

2. The fully optically integrated arbitrary waveform generating device according to claim 1, characterized in that: The Mach-Zehnder interferometer includes a delay line and two Y-type branch waveguide couplers. The two Y-type waveguides and the delay line are connected in series. The lengths of the delay lines in the Mach-Zehnder interferometer are inconsistent, and the design of the delay line lengths obeys an arithmetic progression or a geometric progression distribution. The delay line length setting of the arithmetic progression is used to synthesize a Gaussian pulse waveform; the delay line setting of the geometric progression is used to synthesize a triangular wave.

3. The fully optically integrated arbitrary waveform generating device according to claim 1, characterized in that: The adjustable optical attenuator has an adjustment ratio from 0% to 100%.

4. An all-optical on-chip integrated arbitrary waveform generating device, characterized in that: The second structure of the device includes an input terminal, a waveform generator unit and an output terminal; the input terminal is connected to the waveform generator unit; the waveform generator unit is connected to the output terminal; The input end includes a linear, low-noise frequency-modulated continuous wave source; the waveform generator unit includes an optical isolator, a straight waveguide, a ring waveguide, an adjustment electrode, and a coupler; the output end includes a photodetector; A linear, low-noise frequency-modulated continuous wave source is connected to an optical isolator, the optical isolator is directly connected in series with a straight waveguide, the straight waveguide and a ring waveguide are connected via a coupler, and the coupler and a photodetector are connected in series.

5. The fully optically integrated arbitrary waveform generating device according to claim 4, characterized in that: The ring waveguide and the straight waveguide are formed by connecting two Y-branch couplers.

6. The fully optically integrated arbitrary waveform generating device according to claim 4, characterized in that: The coupling coefficient between the straight waveguide and the ring waveguide is controlled by adjusting the electrodes.

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