Sensitivity detection method for laser coherent detection system

Abstract

The invention discloses a sensitivity detection method for a laser coherent detection system, which relates to a laser coherent detection technology and comprises the following steps: laser emitted by a laser seed source is divided into local oscillation light and signal light through a beam splitter; loading a modulation signal to the signal light by using an acousto-optic modulator or an electro-optic modulator, and carrying out modulation chopping on the modulated signal light to form a pulse signal; carrying out frequency mixing detection on local oscillation light and the signal light in the balance detector; the adjustable optical attenuator is adjusted to reduce the light intensity input to the balance detector, and the attenuation amount of the optical attenuator is recorded; repeatedly determining the peak amplitude at the frequency peak value, and adjusting the variable optical attenuator until the peak value cannot be monitored at the specified frequency f; and calculating the optical power input by the signal end of the balance detector based on the recorded attenuation of the optical attenuator. The invention provides a method for effectively evaluating the performance of a laser coherent detection system.

Description

Technical Field

[0001] The present application relates to laser coherent detection technology, and in particular to a sensitivity detection method for a laser coherent detection system. Background Art

[0002] Since pulsed laser signals have the advantages of narrow optical pulses, wide repetition rate range, and high peak power, they have good application prospects in fields such as communications. Therefore, high-performance laser coherent pulse signal detection systems are increasingly gaining attention from domestic and foreign researchers. Detection sensitivity is an important technical indicator of the receiving system. Its physical meaning is the minimum optical power received by the detector. High sensitivity means that the detection system can distinguish weaker optical pulse signals. For example, in a laser coherent ranging system, the echo generated by the detection target will be greatly reduced by atmospheric attenuation, background light interference, and the influence of the detection system's own thermal noise. Therefore, in order to increase the detection distance, in addition to increasing the laser's transmission power, it is also necessary to suppress various types of noise and extract weak optical signals from the noise.

[0003] The sensitivity of the laser coherent detection system is the minimum detectable optical power under a certain false alarm probability. The minimum detectable optical power is related to the intensity of the emitted pulsed laser, the working distance, the local oscillator optical power, the APD gain factor, the dark current of the APD, the system thermal effect noise, etc. Most of the current research focuses on what measures to take to improve the detection sensitivity, but for the existing laser coherent detection system, there is no accurate measurement method to evaluate the sensitivity of the system. Summary of the invention

[0004] An embodiment of the present application provides a method for detecting the sensitivity of a laser coherent detection system, so as to propose a method for evaluating the performance of a laser coherent detection system.

[0005] The present application provides a method for detecting the sensitivity of a laser coherent detection system, including:

[0006] The laser light emitted by the laser seed source is divided into local oscillator light and signal light by a beam splitter;

[0007] Using an acousto-optic modulator or an electro-optic modulator to load a modulation signal onto the signal light, and subjecting the modulated signal light to modulation and chopping to form a pulse signal;

[0008] The adjustable optical attenuator is used to output the pulse signal to the signal end of a balanced detector, so that the local oscillator light and the signal light are mixed and detected in the balanced detector;

[0009] adjusting the adjustable optical attenuator to a minimum attenuation, and recording the attenuation of the optical attenuator; and,

[0010] Specifying the existence of a peak at a frequency f according to the output of the balanced detector, and determining the peak amplitude at the peak;

[0011] Adjusting the adjustable optical attenuator to reduce the light intensity input to the balanced detector, and recording the attenuation of the optical attenuator;

[0012] Repeatedly determine the peak amplitude at the frequency peak, and adjust the adjustable optical attenuator until the peak value cannot be detected at the specified frequency f;

[0013] The optical power input to the signal end of the balanced detector is calculated based on the recorded attenuation of the optical attenuator.

[0014] Optionally, the laser emitted by the laser seed source is divided into local oscillator light and signal light by a beam splitter, wherein the local oscillator light and the signal light have a set proportional relationship, the local oscillator light is injected into the local oscillator end of the balanced detector, and the signal light is injected into the acousto-optic modulator.

[0015] Optionally, the frequency range of the modulation signal loaded on the signal light by an acousto-optic modulator or an electro-optic modulator is 200 MHz to 800 MHz;

[0016] The insertion loss of the acousto-optic modulator is less than 3dB, and the rise time of the optical pulse is less than 30ns;

[0017] The frequency of the modulation signal is the specified frequency f.

[0018] Optionally, the local oscillator light and the signal light are mixed and detected in the balanced detector, and a common mode rejection ratio is greater than 25 dB.

[0019] Optionally, determining the peak amplitude at the peak value is achieved by an oscilloscope, the bandwidth of the oscilloscope is 3 to 5 times the frequency of the modulation signal, and the sampling rate is not less than 2.5 GS / s.

[0020] Optionally, the optical power P input to the signal end of the balanced detector is calculated based on the recorded attenuation of the optical attenuator to satisfy:

[0021]

[0022] Among them, P seed represents the optical power output by the laser seed source, L represents the return loss of the acousto-optic modulator, a represents the attenuation of the optical attenuator, and α represents the proportion of the signal light after splitting.

[0023] Optionally, calculating the optical power input to the signal end of the balanced detector based on the recorded attenuation of the optical attenuator further includes:

[0024] When an oscilloscope cannot be used to obtain effective frequency domain information, the attenuation of the optical attenuator is directly recorded. The optical power P calculated at this time is the sensitivity of the laser coherent detection system.

[0025] The method of the embodiment of the present application provides a practical method for evaluating the performance of a laser coherent detection system.

[0026] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0028] Figure 1 The following is a schematic diagram of the basic process of the sensitivity detection method of the laser coherent detection system according to the embodiment of the present application;

[0029] Figure 2 The following is a schematic diagram of the detection architecture of the laser coherent detection system sensitivity detection method according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0031] The present application embodiment provides a method for detecting the sensitivity of a laser coherent detection system. Figure 1 , Figure 2 As shown, the following steps are included:

[0032] In step S101, the laser light emitted by the laser seed source is split into local oscillator light and signal light through a beam splitter. In some examples, the laser light emitted by the laser seed source is split into local oscillator light and signal light through a beam splitter, wherein the local oscillator light and the signal light have a set proportional relationship, the local oscillator light is injected into the local oscillator end of the balanced detector, and the signal light is injected into the acousto-optic modulator.

[0033] For example, in practical applications, the laser seed source of the laser coherent detection technology system is divided into two beams by a beam splitter: one is the local oscillator light, and the other is the signal light. 20% of the local oscillator light is injected into the local oscillator end of the balanced detector; 80% is injected into the acousto-optic modulator, where the line width of the seed source is less than 10kHz, the wavelength is 1550nm, and the power is 20-30mW.

[0034] In step S102, a modulation signal is applied to the signal light using an acousto-optic modulator or an electro-optic modulator, and the modulated signal light is subjected to modulation chopping to form a pulse signal. In some embodiments, the frequency range of the modulation signal applied to the signal light using the acousto-optic modulator or the electro-optic modulator is 200 MHz to 800 MHz, the insertion loss of the acousto-optic modulator is less than 3 dB, and the rise time of the optical pulse is less than 30 ns; the frequency of the modulation signal is a specified frequency f.

[0035] In step S103, the pulse signal is output to the signal end of the balanced detector by using the adjustable optical attenuator, so that the local oscillator light and the signal light are mixed and detected in the balanced detector. In some examples, the adjustable optical attenuator has an accuracy of ±0.1 dB and a dynamic range of 100 dB. The local oscillator light and the signal light are mixed and detected in the balanced detector, and the common mode rejection ratio is greater than 25 dB.

[0036] In step S104, the adjustable optical attenuator is adjusted to a minimum attenuation, and the attenuation a1 (dB) of the optical attenuator is recorded.

[0037] In step S105, a peak value is determined at a specified frequency f according to the output of the balanced detector, and the peak amplitude at the peak value is determined. In some examples, the peak amplitude at the peak value is determined by an oscilloscope, the output of the balanced detector is connected to the oscilloscope, and the signal frequency domain is monitored by the oscilloscope, the bandwidth of the oscilloscope is 3 to 5 times the frequency of the modulated signal, and the sampling rate is not less than 2.5 GS / s.

[0038] In the specific example, after using an oscilloscope to perform FFT on the signal and observe the signal spectrum, it can be observed that there is a peak at the specified frequency f, and the peak amplitude V (dBV) at this time is recorded.

[0039] In step S106, the adjustable optical attenuator is adjusted to reduce the intensity of light input to the balanced detector, and the attenuation a2 (dB) of the optical attenuator is recorded.

[0040] In step S107, repeatedly determine the peak amplitude at the frequency peak, and adjust the adjustable optical attenuator until the peak value cannot be detected at the specified frequency f;

[0041] In step S108, the optical power input to the signal end of the balanced detector is calculated based on the recorded attenuation of the optical attenuator.

[0042] In some embodiments, the optical power P (mW) input to the signal end of the balanced detector is calculated based on the recorded attenuation of the optical attenuator to satisfy:

[0043]

[0044] Among them, P seed represents the optical power output by the laser seed source (mW), L represents the return loss of the acousto-optic modulator, a represents the attenuation of the optical attenuator (dB), α represents the proportion of the signal light after splitting, and the splitting ratio of the beam splitter is 8:2, then α=0.8.

[0045] In some embodiments, calculating the optical power input to the signal end of the balanced detector based on the recorded attenuation of the optical attenuator further includes:

[0046] When an oscilloscope cannot be used to obtain effective frequency domain information, the attenuation of the optical attenuator is directly recorded. At this time, the optical power P calculated by formula (1) is the sensitivity of the laser coherent detection system.

[0047] The embodiment of the present application proposes an effective and accurate evaluation method for the sensitivity of the laser coherent detection system, which can evaluate the performance of the laser coherent detection system.

[0048] It should be noted that in the various embodiments of the present application, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0049] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0050] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0051] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A method for detecting sensitivity of a laser coherent detection system, characterized in that: include: The laser light emitted by the laser seed source is divided into local oscillator light and signal light by a beam splitter; Using an acousto-optic modulator or an electro-optic modulator to load a modulation signal onto the signal light, and subjecting the modulated signal light to modulation and chopping to form a pulse signal; The adjustable optical attenuator is used to output the pulse signal to the signal end of a balanced detector, so that the local oscillator light and the signal light are mixed and detected in the balanced detector; adjusting the adjustable optical attenuator to a minimum attenuation, and recording the attenuation of the optical attenuator; and, Specifying the existence of a peak at a frequency f according to the output of the balanced detector, and determining the peak amplitude at the peak; Adjusting the adjustable optical attenuator to reduce the light intensity input to the balanced detector, and recording the attenuation of the optical attenuator; Repeatedly determine the peak amplitude at the frequency peak, and adjust the adjustable optical attenuator until the peak value cannot be detected at the specified frequency f; The optical power input to the signal end of the balanced detector is calculated based on the recorded attenuation of the optical attenuator.

2. The laser coherent detection system sensitivity detection method according to claim 1, characterized in that: The laser emitted by the laser seed source is divided into local oscillator light and signal light through a beam splitter, wherein the local oscillator light and the signal light have a set proportional relationship, the local oscillator light is injected into the local oscillator end of the balanced detector, and the signal light is injected into the acousto-optic modulator.

3. The laser coherent detection system sensitivity detection method according to claim 1, characterized in that: The frequency range of the modulation signal added to the signal light by using an acousto-optic modulator or an electro-optic modulator is 200 MHz to 800 MHz; The insertion loss of the acousto-optic modulator is less than 3dB, and the rise time of the optical pulse is less than 30ns; The frequency of the modulation signal is the specified frequency f.

4. The laser coherent detection system sensitivity detection method according to claim 1, characterized in that: The local oscillator light and the signal light are mixed and detected in the balanced detector, and the common mode rejection ratio is greater than 25dB.

5. The laser coherent detection system sensitivity detection method according to claim 1, characterized in that: The peak amplitude at the peak is determined by an oscilloscope, the bandwidth of the oscilloscope is 3 to 5 times the frequency of the modulation signal, and the sampling rate is not less than 2.5 GS / s.

6. The laser coherent detection system sensitivity detection method according to claim 5, characterized in that: The optical power P at the signal end of the balanced detector is calculated based on the recorded attenuation of the optical attenuator to satisfy: Among them, P seed represents the optical power output by the laser seed source, L represents the return loss of the acousto-optic modulator, a represents the attenuation of the optical attenuator, and α represents the proportion of the signal light after splitting.

7. The method for detecting sensitivity of a laser coherent detection system according to claim 6, characterized in that: The calculation of the optical power input to the signal end of the balanced detector based on the recorded attenuation of the optical attenuator also includes: When an oscilloscope cannot be used to obtain effective frequency domain information, the attenuation of the optical attenuator is directly recorded. The optical power P calculated at this time is the sensitivity of the laser coherent detection system.

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