Reconfigurable chirped optoelectronic oscillator

Abstract

The application discloses a reconfigurable linear frequency modulation optoelectronic oscillator, and belongs to the field of microwave photonic signal generation.The reconfigurable linear frequency modulation optoelectronic oscillator comprises a tunable laser source, a radio frequency signal generation source, a cascaded intensity modulator and a first phase modulator, a broadband filter, a second phase modulator, a tunable optical filter, an optoelectronic detector and an electric amplifier.The 2m+1 optical comb teeth of the output can be adjusted in frequency and comb interval by adjusting the center frequency of the tunable laser source and the broadband filter; the number of spectral lines of the optical comb teeth can be reconfigured by adjusting the bandwidth of the broadband filter; the frequency of the output signal of the optoelectronic oscillator can be linearly changed by adjusting the center frequency of the tunable optical filter, a multi-band linear frequency modulation signal is generated, and the center frequencies of the linear frequency modulation signals of the bands are respectively equal to the difference between the frequency of each comb tooth and the center frequency of the tunable optical filter.The reconfigurable linear frequency modulation optoelectronic oscillator is realized, and the linear frequency modulation signal generated has the advantage of low phase noise.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave photon signal generation, and particularly relates to a reconfigurable linear frequency modulation optoelectronic oscillator. BACKGROUND

[0002] The linear frequency modulation signal generation technology based on the optoelectronic oscillator has important use value in the field of pulse compression radar. Compared with the generation of linear frequency modulation signals by using the voltage-controlled oscillator or the arbitrary waveform generator in the traditional electronic way, the generation of linear frequency modulation signals based on the optoelectronic oscillator has excellent characteristics such as low loss, high bandwidth and anti-electromagnetic interference.

[0003] The existing device for generating linear frequency modulation signals by using photon technology is mainly based on the frequency-time mapping and frequency multiplication method. The key component in the device for generating linear frequency modulation signals based on the frequency-time mapping method is a spectrum shaper, which makes the waveform of the input optical pulse consistent with the output signal. In the pulse shaper realized by using the linear chirp Bragg grating, the duration of the chirp microwave pulse is short after the linear mapping of the frequency table-time, because the working bandwidth of the linear chirp Bragg grating is limited. In the spectrum shaper based on the dispersion optical fiber, a long dispersion optical fiber is needed to realize large dispersion, so that the system size is large, the stability is reduced and the attenuation is increased. In the spectrum shaper based on the spatial light modulator, the waveform shape and the spatial frequency can be flexibly designed, but the system structure is relatively complex, the size is large and the coupling loss is high due to the use of free space optical devices. The linear frequency modulation signal of low frequency can also be obtained by frequency multiplication, and the frequency multiplication process is realized by beat frequency or photon time compression technology. The limitation of this technology is that when the optical signal composed of two first-order sidebands and an optical carrier is transmitted on a long-span optical fiber, the frequency multiplication signal will suffer power loss caused by dispersion, thereby limiting its application. SUMMARY

[0004] The application aims at the problems in the background art, and provides a reconfigurable linear frequency modulation optoelectronic oscillator.

[0005] To achieve the above object, the technical scheme adopted by the application is as follows:

[0006] A reconfigurable linear frequency modulation optoelectronic oscillator comprises a center frequency tunable laser source, a radio frequency signal source, a cascaded intensity modulator and a first phase modulator, a wideband filter, a second phase modulator, a center frequency tunable optical filter, a photodetector and an electrical amplifier.

[0007] The tunable laser source generates a center frequency f cThe tunable optical carrier is input to the cascaded intensity modulator and first phase modulator, wherein the tunable laser source generates an optical carrier with a center frequency f c ; the cascaded intensity modulator and first phase modulator are modulated by a radio frequency signal source with a center frequency f RF ; the tunable radio frequency signal is modulated, and the output frequency contains f c , f c ±f RF , …, f c ±n f RF , wherein the optical frequency comb has a comb tooth number of 2n+1, n is an integer greater than or equal to 1, and the radio frequency signal source generates a radio frequency signal with a center frequency f RF ; after the optical frequency comb passes through a wideband filter with a center frequency f c and a 3dB bandwidth of 2m f RF , the output frequency is f c , f c ±f RF , …, f c ±m f RF , wherein m is a positive integer less than n; each of the 2m+1 optical comb teeth output by the wideband filter is input to a second phase modulator as an optical carrier, and after being modulated by the second phase modulator, each optical carrier and the positive and negative first-order sideband signals of each optical carrier are output; the signal modulated by the second phase modulator is input to a tunable optical filter, and after the tunable optical filter breaks the amplitude balance between the positive and negative first-order sidebands, the signal is input to a photodetector; the photodetector converts the input optical signal into an electrical signal with a frequency of f c -f, f c ±f RF -f, …, f c ±m f RF -f, a part of the electrical signal is directly output, and the other part of the electrical signal is amplified by an electrical amplifier providing gain to the loop and then fed back to the radio frequency signal port of the second phase modulator to form a complete optoelectronic oscillator loop, wherein f is the center frequency of the tunable optical filter. Finally, a reconfigurable linear frequency modulation optoelectronic oscillator is formed.

[0008] wherein the tunable laser source generates an optical carrier with a center frequency f c , in Hz; the radio frequency signal source generates a radio frequency signal with a center frequency f RF , in Hz; the wideband filter has a center frequency f c , in Hz, and a 3dB bandwidth of 2m f RF , in Hz, and the comb tooth spacing of the optical frequency comb output by the wideband filter is f RF, the number of the comb teeth is 2m+1. When the center frequency of the tunable optical filter is f, the frequency of the electrical signal output by the photodetector is f c -f, f c ±f RF -f,..., f c ±m f RF -f; when the center frequency of the tunable optical filter is linearly changed between f1 and f2, the electrical signal output by the photodetector contains m frequency bands of linear frequency modulation signals with the frequency of f c -f1 to f c -f2, f c ±f RF -f1 to f c ±f RF -f2,..., f c ±m f RF -f1 to f c ±m f RF -f2, each of the linear frequency modulation signals has a bandwidth of f2-f1.

[0009] Further, by adjusting the center frequency f of the tunable laser source and the wideband filter c , the frequency and the comb interval of the output 2m+1 optical combs can be adjusted; by adjusting the bandwidth 2m f of the wideband filter RF , the number of spectral lines of the optical combs 2m+1 can be reconfigured; by adjusting the center frequency f of the tunable optical filter, the frequency of the electrical signal output by the optoelectronic oscillator can be linearly changed, thereby generating a multi-band linear frequency modulation signal, the center frequency of each band of the linear frequency modulation signal being equal to the difference between the frequency of each comb and the center frequency of the tunable optical filter, specifically f c -f, f c ±f RF -f,..., f c ±m f RF -f, the bandwidth of the linear frequency modulation signal is equal to the tuning range f2-f1 of the center frequency of the tunable optical filter.

[0010] Compared with the prior art, the present application has the following beneficial effects:

[0011] This invention provides a reconfigurable linear frequency modulated (LFM) opto-oscillator. By adjusting the center frequencies of a tunable laser source and a broadband filter, the frequency and spacing of the output 2m+1 optical comb teeth can be adjusted. The number of spectral lines in the optical comb (2m+1) can be reconfigured by adjusting the bandwidth of the broadband filter. Adjusting the center frequency of the tunable optical filter linearly changes the frequency of the opto-oscillator's output signal, generating a multi-band LFM signal. The center frequency of each band of the LFM signal is equal to the difference between the frequency of each comb tooth and the center frequency of the tunable optical filter, and the bandwidth of the LFM signal is equal to the tuning range of the tunable optical filter's center frequency. Therefore, this invention realizes a reconfigurable LFM opto-oscillator, and the LFM signal generated by the oscillator has the advantage of low phase noise. Attached Figure Description

[0012] Figure 1 A schematic diagram of a reconfigurable linear frequency modulated optoelectronic oscillator provided by the present invention;

[0013] Figure 2 This is a schematic diagram of a reconfigurable linear frequency modulated opto-oscillator provided for an embodiment. Detailed Implementation

[0014] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0015] Example

[0016] like Figure 2 The diagram shown is a schematic of a reconfigurable linear frequency modulated opto-oscillator provided in an embodiment, including a semiconductor tunable laser source, a tunable radio frequency signal generator, a cascaded Mach-Zehnder modulator and a first phase modulator, a broadband tunable bandpass filter, a second phase modulator, a tunable notch filter, a photodetector, and an electrical amplifier.

[0017] The semiconductor tunable laser source generates a 1550nm optical carrier input to a cascaded Mach-Zehnder modulator and a first phase modulator, the cascaded Mach-Zehnder modulator and the first phase modulator are modulated by a radio frequency signal with a center frequency of 10GHz generated by a tunable radio frequency signal source, and the output wavelength contains an optical frequency comb of 1550nm, 1550±0.08nm, 1550±0.16nm and 1550±0.24nm; the optical frequency comb passes through a wideband tunable bandpass filter with a center wavelength of 1550nm and a 3dB bandwidth of 20GHz, and the output wavelength is 3 optical comb teeth of 1550nm, 1550±0.08nm; each of the 3 optical comb teeth output by the wideband tunable bandpass filter is input to a second phase modulator as an optical carrier, and after being modulated by the second phase modulator, each optical carrier and the corresponding positive and negative first-order sideband signals are output; the signal modulated by the second phase modulator is input to a tunable notch filter with a center wavelength of 1549.84nm, and after the tunable notch filter breaks the amplitude balance between the positive and negative first-order sidebands, the signal is input to a photodetector; the photodetector converts the input optical signal into an electrical signal with a frequency of 10GHz, 20GHz and 30GHz; the electrical signal output by the photodetector is divided into two parts, one part is directly output, and the other part is amplified by an electrical amplifier providing gain to the loop and then fed back to the radio frequency signal port of the second phase modulator, forming a complete optoelectronic oscillator loop. When the center wavelength of the tunable notch filter linearly changes from 1549.84nm to 1549.76nm, the photodetector outputs a linear frequency modulation signal with a frequency of 10-20GHz, 20-30GHz and 30-40GHz.

Claims

1. A reconfigurable linear frequency modulated optoelectronic oscillator, characterized in that, It includes a tunable laser source, a radio frequency signal generator, a cascaded intensity modulator and a first phase modulator, a broadband filter, a second phase modulator, a tunable optical filter, a photodetector, and an electrical amplifier. A tunable laser source generates a center frequency f c A tunable optical carrier is input to a cascaded intensity modulator and a first phase modulator; the cascaded intensity modulator and the first phase modulator are fed by a center frequency f emitted by a radio frequency signal generator. RF Tunable radio frequency signal modulation, output frequency includes f c f c ±f RF , ..., f c ±nf RF The optical frequency comb, where n is an integer greater than or equal to 1; the optical frequency comb passes through a center frequency of f. c 3dB bandwidth is 2m f RF After the broadband filter, the output frequency is f c f c ±f RF , ..., f c ±mf RF The optical comb has 2m+1 teeth, where m is a positive integer less than n. Each of the 2m+1 teeth output by the broadband filter is used as an optical carrier input to the second phase modulator. After being modulated by the second phase modulator, each optical carrier and its positive and negative first-order sideband signals are output. The signal modulated by the second phase modulator is input to the tunable optical filter. After the amplitude balance between the positive and negative first-order sidebands is broken by the tunable optical filter, it is input to the photodetector. The photodetector converts the input optical signal into a frequency of f. c -f, f c ±f RF -f, ...,f c ±mf RF The electrical signal -f is output in part, and the other part is amplified by an electrical amplifier and fed back to the radio frequency signal port of the second phase modulator to form a complete optoelectronic oscillator loop, where f is the center frequency of the tunable optical filter.

2. The reconfigurable linear frequency modulated optoelectronic oscillator according to claim 1, characterized in that, By adjusting the center frequency f of the tunable laser source and the broadband filter c Adjust the frequency and spacing of the 2m+1 output optical comb teeth; adjust the bandwidth of the broadband filter by 2m f. RF The number of spectral lines of the reconstructed optical comb is 2m+1; by adjusting the center frequency f of the tunable optical filter, the frequency of the output signal of the photoelectric oscillator is changed, generating a multi-band linear frequency modulated signal.

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