A noise calibration device and method based on low phase noise crystal self-correlation technology

Abstract

This invention discloses a noise calibration device and method based on low-phase-noise crystal oscillator autocorrelation technology. The device includes a narrow-linewidth laser for generating laser light; an electro-optic modulator for intensity modulation of the laser light using a low-phase-noise crystal oscillator as the modulation frequency to obtain a modulated optical signal; an optical fiber coupler for splitting the modulated optical signal into two paths to obtain a first modulated optical signal and a second modulated optical signal; a first photoelectric converter for photoelectric conversion of the first modulated optical signal to obtain a first radio frequency (RF) signal; a second photoelectric converter for photoelectric conversion of the second modulated optical signal to obtain a second RF signal; and a digital phase noise meter for acquiring the first and second RF signals and then using common autocorrelation to obtain the noise to be measured. This device eliminates the need for a delay line, avoiding the problems of sensitivity degradation and Fourier frequency offset dead zone.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology. More specifically, it relates to a noise calibration device and method based on low phase noise crystal oscillator autocorrelation technology. Background Technology

[0002] Currently, the bottom noise calibration device for photoelectric converters uses the traditional delay line calibration method. The device includes a low phase noise reference source, a laser, an electro-optic modulator, a delay line, a phase detector, and a digital acquisition processor. The disadvantages of this device are: 1. The phase noise performance of the low phase noise reference source generated by traditional frequency synthesis technology is far worse than the bottom noise of the photoelectric converter. Even under quadrature phase detection, the phase noise effect of the low phase noise reference source cannot be completely eliminated; 2. The traditional electrical delay line calibration method directly leads to a decrease in measurement sensitivity and the problem of Fourier frequency offset blind zone analysis; 3. The frequency range for photoelectric converter bottom noise testing is the microwave band, but the bottom noise of measurement systems in the microwave band is relatively poor; 4. Due to the imbalance of the electrical delays of the two phase detector arms, the calibration uncertainty of the phase detection sensitivity in the traditional delay line calibration device is relatively large. With the development of microwave photonic radar technology, the bottom noise of the photoelectric converter, as the receiver of photonic radar, directly affects the target acquisition performance of the radar, therefore this parameter is receiving increasing attention. In addition, the technical specifications of photoelectric converters usually only include bandwidth, dark current and responsivity, but not the bottom noise, which is the most important indicator in photoelectric conversion. Therefore, in fields such as radar and communications, the need for calibration of the bottom noise of photoelectric converters is becoming increasingly urgent.

[0003] First, the bottom noise of the photoelectric converter is generated by internal current noise, so the bottom noise of the photoelectric converter is independent of the frequency range. This means that the bottom noise of the photoelectric converter can be measured in the low-frequency band, which avoids the problem of poor bottom noise in microwave frequency band measurement systems. In addition, when measuring bottom noise in the low-frequency band, a low phase noise crystal oscillator can be selected, whose phase noise level is far higher than that of the bottom noise of the photoelectric converter. In autocorrelation measurement, it will not affect the measurement results. Furthermore, by not using the traditional delay line calibration method, the problem of decreased measurement sensitivity and Fourier frequency offset dead zone can be effectively avoided.

[0004] Therefore, there is an urgent need to propose a noise calibration device and method based on low phase noise crystal oscillator autocorrelation technology to solve the calibration of bottom noise of high-sensitivity photoelectric converters. The application of such a device and method can avoid the problems of decreased measurement sensitivity and Fourier frequency offset analysis blind zone caused by traditional delay line calibration devices. Summary of the Invention

[0005] The purpose of this invention is to provide a noise calibration device and method based on low phase noise crystal oscillator autocorrelation technology, so as to solve at least one of the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a noise calibration device based on low phase noise crystal oscillator autocorrelation technology, the device comprising:

[0008] Narrow linewidth lasers are used to generate laser light.

[0009] An electro-optic modulator is used to intensity modulate the laser using a low phase-noise crystal oscillator as the modulation frequency to obtain a modulated optical signal.

[0010] An optical fiber coupler is used to split the modulated optical signal into two paths to obtain a first modulated optical signal and a second modulated optical signal.

[0011] The first photoelectric converter is used to perform photoelectric conversion on the first modulated optical signal to obtain the first radio frequency signal.

[0012] The second photoelectric converter is used to perform photoelectric conversion on the second modulated optical signal to obtain the second radio frequency signal;

[0013] A digital phase noise tester is used to acquire the first and second radio frequency signals and then obtain the noise to be tested using the common source correlation method.

[0014] Optionally, the narrow linewidth laser has a wavelength of 1550 nm, an output power greater than 70 mW, and a RIN less than 1550 nm. The above This refers to the bottom noise level of the photoelectric converter.

[0015] Optionally, the electro-optic modulator operates at a wavelength of 1550 nm, has an insertion loss of 6 dB, and a frequency range of less than 10 GHz.

[0016] Optionally, the low phase noise crystal oscillator has an output power of 16dBm, an output frequency of 10MHz, and a phase noise greater than -170dBc / Hz@10kHz.

[0017] Optionally, the loss per path of the fiber coupler is 3dB.

[0018] Optionally, the frequency of the first radio frequency signal is 10MHz.

[0019] Optionally, the frequency of the second radio frequency signal is 10MHz.

[0020] Optionally, the step of acquiring the first radio frequency signal and the second radio frequency signal includes

[0021] The first radio frequency signal is input to the test terminal of the digital phase noise tester, and the second radio frequency signal is input to the reference terminal of the digital phase noise tester.

[0022] Optionally, the digital phase noise tester has a frequency range of 10MHz and a bottom noise level greater than or equal to -170dBc / Hz@10kHz.

[0023] A second aspect of the present invention provides a noise calibration method based on low phase noise crystal oscillator autocorrelation technology, the method comprising:

[0024] The intensity of the laser is modulated using an electro-optic modulator with a low phase-noise crystal oscillator as the modulation frequency to obtain a modulated optical signal.

[0025] The modulated optical signal is split into two paths by an optical fiber coupler to obtain a first modulated optical signal and a second modulated optical signal.

[0026] The first modulated optical signal is photoelectrically converted by the first photoelectric converter to obtain the first radio frequency signal.

[0027] The second modulated optical signal is photoelectrically converted by a second photoelectric converter to obtain a second radio frequency signal.

[0028] After acquiring the first and second radio frequency signals using a digital phase noise tester, the noise to be tested is obtained using the common source correlation method.

[0029] The beneficial effects of this invention are as follows:

[0030] The noise calibration device disclosed in this invention based on low phase noise crystal autocorrelation technology does not require a delay line, thus avoiding the problems of decreased sensitivity and Fourier frequency offset blind zone; the phase noise of the low phase noise crystal is excellent and will not affect the measurement results; the bottom noise is excellent, thus avoiding the problem of poor bottom noise of microwave frequency band measurement devices. Attached Figure Description

[0031] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0032] Figure 1 This diagram illustrates the structure of a noise calibration device based on low phase noise crystal oscillator autocorrelation technology provided in an embodiment of the present invention.

[0033] Figure 2 The flowchart of the noise calibration method based on low phase noise crystal oscillator autocorrelation technology provided in the embodiment of the present invention is shown. Detailed Implementation

[0034] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0035] The problems with traditional photoelectric converter bottom noise calibration devices include: 1. The phase noise index of the low phase noise reference source generated by traditional frequency synthesis technology is much worse than the bottom noise of the photoelectric converter; 2. The traditional electrical delay line calibration method directly leads to a decrease in measurement sensitivity and the problem of Fourier frequency deviation blind zone analysis; 3. In the microwave band, the overall calibration device has poor bottom noise; 4. The calibration uncertainty of traditional delay line calibration devices is large.

[0036] In view of this, one embodiment of the present invention discloses a noise calibration device based on low phase noise crystal oscillator autocorrelation technology. The device includes a narrow linewidth laser for generating laser light; an electro-optic modulator for intensity modulation of the laser light using a low phase noise crystal oscillator as the modulation frequency to obtain a modulated optical signal; an optical fiber coupler for splitting the modulated optical signal into two paths to obtain a first modulated optical signal and a second modulated optical signal; a first photoelectric converter for photoelectric conversion of the first modulated optical signal to obtain a first radio frequency (RF) signal; a second photoelectric converter for photoelectric conversion of the second modulated optical signal to obtain a second RF signal; and a digital phase noise tester for acquiring the first and second RF signals and then using common autocorrelation to obtain the noise to be measured.

[0037] like Figure 1 The diagram shows a schematic of a noise calibration device based on low phase noise crystal oscillator autocorrelation technology provided in an embodiment of the present invention. Figure 1 It includes a narrow linewidth laser 1, an electro-optic modulator 2, a low phase noise crystal oscillator 3, an optical fiber coupler 4, a first photoelectric converter 5, a second photoelectric converter 6, and a digital phase noise tester 7.

[0038] The output of the narrow linewidth laser 1 is connected to the single-mode fiber of the input of the electro-optic modulator 2. The modulation end of the electro-optic modulator 2 is connected to the radio frequency cable of the low phase noise crystal oscillator 3. The output of the electro-optic modulator 2 is connected to the single-mode fiber of the input of the fiber coupler 4. The first output of the fiber coupler 4 is connected to the single-mode fiber of the input of the first photoelectric converter under test 5. The second output of the fiber coupler 4 is connected to the single-mode fiber of the input of the second photoelectric converter under test 6. The output of the first photoelectric converter under test 5 is connected to the radio frequency cable of the test end of the digital phase noise tester 7. The output of the second photoelectric converter under test 6 is connected to the radio frequency cable of the reference end of the digital phase noise tester 7.

[0039] In one possible implementation, the narrow-linewidth laser has a wavelength of 1550 nm, an output power greater than 70 mW, and a RIN less than [value missing]. The above This refers to the bottom noise level of the photoelectric converter.

[0040] In one possible implementation, the electro-optic modulator operates at a wavelength of 1550 nm, has an insertion loss of 6 dB, and a frequency range of less than 10 GHz.

[0041] In one possible implementation, the low phase noise crystal oscillator has an output power of 16dBm, an output frequency of 10MHz, and a phase noise greater than -170dBc / Hz@10kHz.

[0042] In one possible implementation, the fiber optic coupler has a loss of 3 dB per path.

[0043] In one possible implementation, the frequency of the first radio frequency signal is 10MHz.

[0044] In one possible implementation, the frequency of the second radio frequency signal is 10MHz.

[0045] In one possible implementation, the acquisition of the first radio frequency signal and the second radio frequency signal includes inputting the first radio frequency signal to the test terminal of the digital phase noise tester, and inputting the second radio frequency signal to the reference terminal of the digital phase noise tester.

[0046] In one possible implementation, the digital phase noise tester has a frequency range of 10MHz and a bottom noise level greater than or equal to -170dBc / Hz@10kHz.

[0047] During operation, narrow-linewidth laser 1 is used as the light source, with a wavelength of 1550nm and an output power of over 70mW. Its RIN should be less than [value missing]. To measure the bottom noise performance of the photoelectric converter, electro-optic modulator 2 uses a low-phase-noise crystal oscillator 3 as the modulation frequency to intensity modulate a narrow-linewidth laser 1. Electro-optic modulator 2 operates at a wavelength of 1550 nm, with an insertion loss of 6 dB and a frequency range up to 10 GHz. The low-phase-noise crystal oscillator 3 has an output power of 16 dBm, an output frequency of 10 MHz, and a phase noise of -170 dBc / Hz at 10 kHz. The modulated light output from electro-optic modulator 2 is split into two paths by fiber coupler 4, each with a loss of 3 dB. Each path of modulated light is input to the photoelectric converter under test 5 and... The photoelectric converter under test 6, after passing through the photoelectric converter under test 5 and the photoelectric converter under test 6, obtains a radio frequency signal with a frequency of 10MHz. One 10MHz input is sent to the test terminal of the digital phase noise tester 7, and the other 10MHz input is sent to the reference terminal of the digital phase noise tester 7. The frequency range of the digital phase noise tester 7 covers 10MHz, and the bottom noise reaches -170dBc / Hz@10kHz. The phase noise curve measured from the digital phase noise tester 7 is the bottom noise of the photoelectric converter. The overall measurement device adopts the common source correlation method.

[0048] The noise calibration device based on low phase noise crystal autocorrelation technology disclosed in this embodiment does not require a delay line, thus avoiding the problems of decreased sensitivity and Fourier frequency offset blind zone; the phase noise of the low phase noise crystal is excellent and will not affect the measurement results; the bottom noise is excellent, thus avoiding the problem of poor bottom noise of microwave frequency band measurement devices.

[0049] A second embodiment of the present invention discloses a noise calibration method based on low phase noise crystal oscillator autocorrelation technology. The method includes: intensity modulation of a laser using an electro-optic modulator with a low phase noise crystal oscillator as the modulation frequency to obtain a modulated optical signal; splitting the modulated optical signal into two paths using an optical fiber coupler to obtain a first modulated optical signal and a second modulated optical signal; photoelectric conversion of the first modulated optical signal using a first photoelectric converter to obtain a first radio frequency (RF) signal; photoelectric conversion of the second modulated optical signal using a second photoelectric converter to obtain a second RF signal; and acquiring the first and second RF signals using a digital phase noise tester, and then obtaining the noise to be measured using the common autocorrelation method.

[0050] like Figure 2 The diagram shows a flowchart of a noise calibration method based on low phase noise crystal oscillator autocorrelation technology provided in an embodiment of the present invention.

[0051] The noise calibration method based on low phase noise crystal autocorrelation technology disclosed in this embodiment does not require a delay line, thus avoiding the problems of decreased sensitivity and Fourier frequency offset blind zone; the phase noise of the low phase noise crystal is excellent and will not affect the measurement results; the bottom noise is excellent, thus avoiding the problem of poor bottom noise of microwave frequency band measurement devices.

[0052] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0053] It should also be noted that in the description of this invention, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A noise calibration device based on low phase noise crystal oscillator autocorrelation technique, characterized in that, The device comprises a narrow linewidth laser for generating laser light; an electro-optical modulator for intensity modulating the laser light with a low phase noise crystal oscillator as a modulation frequency to obtain a modulated light signal; an optical fiber coupler for splitting the modulated light signal into two paths to obtain a first path modulated light signal and a second path modulated light signal; a first photoelectric converter for photoelectrically converting the first path modulated light signal to obtain a first path radio frequency signal; a second photoelectric converter for photoelectrically converting the second path modulated light signal to obtain a second path radio frequency signal; a digital phase noise tester for obtaining the noise to be measured by using a common source self-correlation method after collecting the first path radio frequency signal and the second path radio frequency signal. The wavelength of the narrow linewidth laser is 1550 nm, the output power is greater than 70 mW, and the RIN is less than 10 PD+60 dB, wherein the PD is a bottom noise index of the photoelectric converter.

2. The noise calibration device based on low phase noise crystal oscillator autocorrelation technique according to claim 1, characterized in that, The operating wavelength of the electro-optical modulator is 1550 nm, the insertion loss is 6 dB, and the frequency range is less than 10 GHz.

3. The noise calibration device based on low phase noise crystal oscillator autocorrelation technique according to claim 1, characterized in that, The output power of the low phase noise crystal oscillator is 16 dBm, the output frequency is 10 MHz, and the phase noise is greater than -170 dBc / Hz@10 kHz.

4. The low phase noise crystal oscillator self-correlation technique based noise calibration apparatus of claim 1, wherein, The loss of each path of the optical fiber coupler is 3 dB.

5. The low phase noise crystal oscillator self-correlation technique based noise calibration apparatus of claim 1, wherein, The frequency of the first path radio frequency signal is 10 MHz.

6. The low phase noise crystal oscillator self-correlation technique based noise calibration apparatus of claim 1, wherein, The frequency of the second path radio frequency signal is 10 MHz.

7. The low phase noise crystal oscillator self-correlation technique based noise calibration apparatus of claim 1, wherein, The method comprises The first path radio frequency signal is input to the to-be-measured end of the digital phase noise tester, and the second path radio frequency signal is input to the reference end of the digital phase noise tester.

8. The low phase noise crystal oscillator self-correlation technique based noise calibration apparatus of claim 1, wherein, The frequency range of the digital phase noise tester is 10 MHz, and the bottom noise is greater than or equal to -170 dBc / Hz@10 kHz.

9. A noise calibration method based on low phase noise crystal oscillator autocorrelation technique, characterized in that, The method comprises generating laser light by a narrow linewidth laser; intensity modulating the laser light with a low phase noise crystal oscillator as a modulation frequency by an electro-optical modulator to obtain a modulated light signal; splitting the modulated light signal into two paths by an optical fiber coupler to obtain a first path modulated light signal and a second path modulated light signal; photoelectrically converting the first path modulated light signal by a first photoelectric converter to obtain a first path radio frequency signal; photoelectrically converting the second path modulated light signal by a second photoelectric converter to obtain a second path radio frequency signal; collecting the first path radio frequency signal and the second path radio frequency signal by a digital phase noise tester, and then obtaining the noise to be measured by using a common source self-correlation method; The wavelength of the narrow linewidth laser is 1550 nm, the output power is greater than 70 mW, and the RIN is less than PD+60 dB, wherein the PD is a bottom noise index of the photoelectric converter.

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