A device and method for measuring extinction ratio of an acousto-optic modulator

Abstract

The invention discloses an acousto-optic modulator extinction ratio measuring device and method, belonging to the technical field of quantum secure communication, and solving the problem of how to accurately measure the extinction ratio of an acousto-optic modulator. The signal source parameters of the measuring device are set, and the signal source outputs two synchronous electrical signals, which are respectively used as a pulse laser light emission time reference signal and an AOM driver driving time reference signal. The pulse laser generates an optical pulse signal with a high extinction ratio as a reference optical signal. The optical pulse signal is modulated by the AOM and input into a power meter for power measurement. The extinction ratio of the acousto-optic modulator can be measured with high precision. The device has a simple structure, low cost, easy operation, and short measurement time, thus filling the blank of such technical solutions. The basic optical power P0 of the optical pulse is measured, and the minimum optical power P2 is obtained by adjusting the delay of the two electrical signals. The ratio of the basic optical power P0 to the minimum optical power P2 is the extinction ratio of the acousto-optic modulator. The solution is simple and effective, has good feasibility and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of quantum secure communication and relates to a device and method for measuring the extinction ratio of an acousto-optic modulator. Background Art

[0002] Phase modulator (PM) and acousto-optic modulator (AOM) are two commonly used modulators in the field of optics. The principle of the phase modulator is to use the property of the refractive index change of the electro-optic crystal under the action of the electric field to change the phase of the optical signal passing through the modulator. It is generally believed that the phase modulator has a strong polarization-related characteristic. During use, it is usually coupled with a polarization-maintaining fiber to control the polarization of the light passing through the phase modulator. Unlike the phase modulator, the principle of the acousto-optic modulator is the acousto-optic effect. When the driving electrical signal is loaded on the acousto-optic modulator, an ultrasonic field is formed inside the acousto-optic crystal. When the incident light signal passes through the acousto-optic modulator, the light field interacts with the ultrasonic field to diffract, and the intensity of the outgoing diffracted light changes with the intensity of the ultrasonic field. The acousto-optic modulator often uses a single-mode pigtail coupling method, and it is generally believed that the acousto-optic modulator is independent of the polarization characteristics of the modulated light signal.

[0003] In the prior art, a Chinese utility model patent discloses "An acousto-optic modulator optical power loss test machine" (CN210719641U), which specifically discloses: from left to right on the same horizontal line, it includes a light source laser (1), a first optical fiber collimator (2), a first clamp (3), an acousto-optic device (4), a second clamp (5), a second optical fiber collimator (6), and a laser power meter (7); the technical solution of the utility model patent is to propose an acousto-optic modulator optical power loss test machine for the purpose of preventing the influence of ambient background light on the final optical power test during debugging and testing, which is a spatial optical structure; by adopting automatic coupling technology, turning on the light source, performing automatic coupling on a computer, adjusting the dimensions of all electric five-dimensional adjustment frames to maximize the optical power reading, and subtracting the coupling loss of a standard optical fiber collimator, the final test result can be obtained, thereby greatly improving efficiency.

[0004] However, the technical solution of the above patent does not mention how to measure the extinction ratio of the AOM. After literature search, there is no complete public solution in the prior art that can accurately measure the extinction ratio of the AOM. Therefore, how to measure the extinction ratio of the AOM is a technical gap. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to accurately measure the extinction ratio of an acousto-optic modulator.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The invention discloses an acousto-optic modulator extinction ratio measuring device, comprising a control signal generating device, an optical pulse signal generating device, an AOM driver, an AOM and a power meter; two output ends of the control signal generating device are respectively connected to the input ends of the optical pulse signal generating device and the AOM driver; the output end of the optical pulse signal generating device is connected to the AOM, the output end of the AOM driver is also connected to the AOM, and the output end of the AOM is connected to the power meter; the measuring optical path of the acousto-optic modulator extinction ratio is as follows: the parameters of the control signal generating device are set, the control signal generating device outputs two synchronous electrical signals, which are respectively used as the luminous time reference signal of the optical pulse signal generating device and the driving time reference signal of the AOM driver; the optical pulse signal generating device generates an optical pulse signal as a reference optical signal, and the optical pulse signal is modulated by the AOM and input into the power meter for power measurement.

[0008] The invention discloses an acousto-optic modulator extinction ratio measuring device. The measuring optical path of the acousto-optic modulator extinction ratio is as follows: setting parameters of a signal source, the signal source outputs two synchronous electrical signals, which are respectively used as a light emission time reference signal of a pulse laser and a driving time reference signal of an AOM driver. The pulse laser generates an optical pulse signal with a high extinction ratio as a reference optical signal. The optical pulse signal is modulated by the AOM and input into a power meter for power measurement. The extinction ratio of the acousto-optic modulator can be measured with high precision. The device has a simple structure, low cost, easy operation, and short measurement time, thus filling the blank of such technical solutions.

[0009] As a further improvement of the technical solution of the present invention, the control signal generating device outputs the first electrical signal of the two synchronous electrical signals and sends it to the optical pulse signal generating device to control the optical pulse signal generating device to output the optical pulse signal, control the AOM not to work, and use a power meter to measure the basic optical power P0 of the optical pulse signal; the second electrical signal is sent to the AOM driver to control the AOM to work, gradually change the relative delay between the first electrical signal and the second electrical signal, find the minimum optical power P2 measured by the power meter, and calculate the extinction ratio of the AOM as P0 / P2.

[0010] As a further improvement of the technical solution of the present invention, the light emitting frequency of the optical pulse signal generating device is not higher than the modulation frequency of the AOM.

[0011] As a further improvement of the technical solution of the present invention, the light emission period of the optical pulse signal generating device is an integer multiple of the modulation period of the AOM.

[0012] As a further improvement of the technical solution of the present invention, the optical pulse signal generating device is a pulse laser.

[0013] As a further improvement of the technical solution of the present invention, the optical pulse signal generating device uses a continuous light chopping method to generate the required optical pulse signal.

[0014] As a further improvement of the technical solution of the present invention, the device for generating the required optical pulse signal using the continuous light chopping method is a modulator with an intensity modulation function.

[0015] As a further improvement of the technical solution of the present invention, the modulator with intensity modulation function is an intensity modulator or an electro-absorption modulator.

[0016] As a further improvement of the technical solution of the present invention, the control signal generating device and the power meter are controlled by a host computer.

[0017] As a further improvement of the technical solution of the present invention, the control signal generating device adopts any one of a signal source, a signal generator, an arbitrary function generator or a control circuit board.

[0018] As a further improvement of the technical solution of the present invention, the parameters of the control signal generating device include the waveform, frequency, amplitude, bandwidth, delay and duty cycle of the output signal.

[0019] A measurement method using the acousto-optic modulator extinction ratio measurement device comprises the following steps:

[0020] Step S1, setting the parameters of the control signal generating device through the control signal generating device control panel or the host computer, outputting the electrical signal 1 to the optical pulse signal generating device, and controlling the optical pulse signal generating device to output the optical pulse signal;

[0021] Step S2, setting the AOM not to work, and using a power meter to measure the power P0 of the optical pulse signal;

[0022] Step S3, setting the parameters of the control signal generating device through the control signal generating device control panel, and the control signal generating device outputs the electrical signal 2 to the AOM driver;

[0023] Step S4, controlling the AOM to work, and then using a power meter to measure the power P1 of the optical pulse signal;

[0024] Step S5, gradually changing the relative delay of the electrical signal 1 and the electrical signal 2, and finding the minimum power P2 of the power P1 of the optical pulse signal;

[0025] Step S6, calculating the extinction ratio of the AOM as P0 / P2, which is the extinction ratio of the acousto-optic modulator.

[0026] As a further improvement of the technical solution of the present invention, the following steps are included after step S6: step S7, after changing the output voltage of the AOM driver, return to step S4 until the number of set output voltages of different AOM drivers is reached, and the measurement is ended.

[0027] A method for measuring the extinction ratio of an acousto-optic modulator of the present invention measures the basic optical power P0 of an optical pulse, and then obtains the minimum optical power P2 by adjusting the delay of two electrical signals. The ratio of the basic optical power P0 to the minimum optical power P2 is the extinction ratio of the acousto-optic modulator. The scheme is simple and effective, has good feasibility and low cost.

[0028] The advantages of the present invention are:

[0029] (1) The present invention provides an acousto-optic modulator extinction ratio measuring device. The measuring optical path of the acousto-optic modulator extinction ratio is as follows: the parameters of a signal source are set, and the signal source outputs two synchronous electrical signals, which are respectively used as the light emission time reference signal of the pulse laser and the driving time reference signal of the AOM driver. The pulse laser generates an optical pulse signal with a high extinction ratio as a reference optical signal. The optical pulse signal is modulated by the AOM and input into a power meter for power measurement. The extinction ratio of the acousto-optic modulator can be measured with high precision. The device has a simple structure, low cost, easy operation, and short measurement time, thus filling the gap of this type of technical solution.

[0030] (2) The method for measuring the extinction ratio of an acousto-optic modulator of the present invention measures the basic optical power P0 of the optical pulse, and then obtains the minimum optical power P2 by adjusting the delay of the two electrical signals. The ratio of the basic optical power P0 to the minimum optical power P2 is the extinction ratio of the acousto-optic modulator. The scheme is simple and effective, has good feasibility and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a structural diagram of an acousto-optic modulator extinction ratio measuring device according to a first embodiment of the present invention;

[0032] Figure 2 is a flow chart of a method for measuring the extinction ratio of an acousto-optic modulator according to a second embodiment of the present invention;

[0033] Figure 3 It is a structural diagram of an acousto-optic modulator optical power loss tester in the prior art. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0036] Embodiment 1

[0037] like Figure 1 As shown, an acousto-optic modulator extinction ratio measuring device includes a signal source, a pulse laser, an AOM driver, an AOM and a power meter; two output ends of the signal source are respectively connected to the input ends of the pulse laser and the AOM driver; the output end of the pulse laser is connected to the AOM, the output end of the AOM driver is also connected to the AOM, and the output end of the AOM is connected to the power meter.

[0038] The optical path for measuring the extinction ratio of the acousto-optic modulator is as follows: a pulsed laser is used to output a high extinction ratio optical pulse as a reference optical signal. The optical pulse is modulated by the AOM and then input into a high-precision power meter for power measurement. A signal source is used to output two synchronized electrical signals, which are used as the emission time reference signal of the pulsed laser and the driving time reference signal of the AOM driver.

[0039] First, set the parameters of the signal source through the signal source control panel or the host computer, such as the waveform, frequency, amplitude, bandwidth, delay, duty cycle, etc. of the output signal, the signal source outputs electrical signal 1 to the pulse laser, controls the pulse laser to output an optical pulse signal, sets the AOM not to work, and uses a power meter to measure the power P0 of the optical pulse signal; secondly, set the parameters of the signal source through the signal source control panel or the host computer, such as the waveform, frequency, amplitude, bandwidth, delay, duty cycle, etc. of the output signal, the signal source outputs electrical signal 2 to the AOM driver, controls the AOM to work, and then uses a power meter to measure the power P1 of the optical pulse signal; then, gradually change the relative delay of electrical signal 1 and electrical signal 2, and find the minimum power P2 of the power P1 of the optical pulse signal; finally, calculate the extinction ratio of the AOM as P0 / P2, and the power can be directly subtracted when it is in dBm.

[0040] Note that the emission frequency of the pulsed laser should not be higher than the modulation frequency of the AOM in principle, otherwise the measurement result will be inaccurate. In addition, the emission period of the pulsed laser should be an integer multiple of the modulation period of the AOM.

[0041] By using the above method and changing the output voltage of the AOM driver, the extinction ratio of the AOM under different driving voltages can be conveniently measured.

[0042] If the signal source and the power meter are controlled by a host computer to achieve relatively delayed control and power readout, this solution can also be used to achieve automated measurement and result recording, which can further reduce costs and improve test efficiency and accuracy.

[0043] Note that the optical pulse signal here can also be generated by other means, such as using a continuous light chopping method to generate the required optical pulse, such as by using a modulator with intensity modulation function, including an intensity modulator, an electro-absorption modulator, etc. to achieve continuous light chopping.

[0044] Note that the signal source can also be realized by other means, such as a signal generator, an arbitrary function generator, a control circuit board, etc.

[0045] Embodiment 2

[0046] like Figure 2 As shown, the specific steps of the method for measuring the extinction ratio of an acousto-optic modulator using the device for measuring the extinction ratio of an acousto-optic modulator in the first embodiment are as follows:

[0047] Step S1, setting the parameters of the signal source, such as the waveform, frequency, amplitude, bandwidth, delay, duty cycle, etc. of the output signal, through the signal source control panel or the host computer, outputting the electrical signal 1 to the pulse laser, and controlling the pulse laser to output an optical pulse signal;

[0048] Step S2, setting the AOM not to work, and using a power meter to measure the power P0 of the optical pulse signal;

[0049] Step S3, setting the parameters of the signal source, such as the waveform, frequency, amplitude, bandwidth, delay, duty cycle, etc. of the output signal, through the signal source control panel or the host computer, and the signal source outputs the electrical signal 2 to the AOM driver;

[0050] Step S4, controlling the AOM to work, and then using a power meter to measure the power P1 of the optical pulse signal;

[0051] Step S5, gradually changing the relative delay of the electrical signal 1 and the electrical signal 2, and finding the minimum power P2 of the power P1 of the optical pulse signal;

[0052] Step S6, calculate the extinction ratio of the AOM as P0 / P2, and when the power is in dBm, they can be directly subtracted to obtain the extinction ratio of the AOM;

[0053] The following steps may also be included:

[0054] Step S7, after changing the output voltage of the AOM driver, return to step S4 until the number of different AOM driver output voltages is reached, and the measurement is terminated, so that by changing the output voltage of the AOM driver, the extinction ratio of the AOM under different driving voltages can be conveniently measured.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An acousto-optic modulator extinction ratio measuring device, characterized in that: The invention comprises a control signal generating device, an optical pulse signal generating device, an AOM driver, an AOM and a power meter; two output ends of the control signal generating device are respectively connected to the input ends of the optical pulse signal generating device and the AOM driver; the output end of the optical pulse signal generating device is connected to the AOM, the output end of the AOM driver is also connected to the AOM, and the output end of the AOM is connected to the power meter; the measuring optical path of the extinction ratio of the acousto-optic modulator is as follows: setting the parameters of the control signal generating device, the control signal generating device outputs two synchronous electric signals, the first electric signal is sent into the optical pulse signal generating device as a luminous time reference signal of the optical pulse signal generating device, the optical pulse signal generating device is controlled to output the optical pulse signal, the AOM is controlled not to work, the basic optical power P0 of the optical pulse signal is measured by the power meter, the second electric signal is sent into the AOM driver as a driving time reference signal of the AOM driver, the AOM is controlled to work, the relative delay between the first electric signal and the second electric signal is changed, the minimum optical power P2 measured by the power meter is found, and the extinction ratio of the AOM is calculated as P0 / P2.

2. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The light emitting frequency of the optical pulse signal generating device is not higher than the modulation frequency of the AOM.

3. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The light emission period of the optical pulse signal generating device is an integer multiple of the modulation period of the AOM.

4. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The optical pulse signal generating device is a pulse laser.

5. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The optical pulse signal generating device uses a continuous optical chopping method to generate the required optical pulse signal.

6. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 5, characterized in that: The device that generates the required optical pulse signal using the continuous light chopping method is a modulator with an intensity modulation function.

7. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 6, characterized in that: The modulator with intensity modulation function is an intensity modulator or an electro-absorption modulator.

8. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The control signal generating device and the power meter are controlled by a host computer.

9. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The control signal generating device adopts any one of a signal source, a signal generator, an arbitrary function generator or a control circuit board.

10. The device for measuring the extinction ratio of an acousto-optic modulator according to claim 1, characterized in that: The parameters of the control signal generating device include the waveform, frequency, amplitude, bandwidth, delay and duty cycle of the output signal.

11. A method for measuring the extinction ratio of an acousto-optic modulator using the device for measuring the extinction ratio of an acousto-optic modulator according to any one of claims 1 to 10, characterized in that: The following steps are involved: Step S1, setting the parameters of the control signal generating device through the control signal generating device control panel or the host computer, outputting the first electrical signal to the optical pulse signal generating device, and controlling the optical pulse signal generating device to output the optical pulse signal; Step S2, setting the AOM not to work, and using a power meter to measure the power P0 of the optical pulse signal; Step S3, setting the parameters of the control signal generating device through the control signal generating device control panel, and the control signal generating device outputs the second electrical signal to the AOM driver; Step S4, controlling the AOM to work, and then using a power meter to measure the power P1 of the optical pulse signal; Step S5, gradually changing the relative delay of the first electrical signal and the second electrical signal to find the minimum power P2 of the power P1 of the optical pulse signal; Step S6, calculating the extinction ratio of the AOM as P0 / P2, which is the extinction ratio of the acousto-optic modulator.

12. A measurement method according to claim 11, characterized in that: The following steps are also included after step S6: Step S7, after changing the output voltage of the AOM driver, return to step S4 until the number of different output voltages of the AOM driver is reached, and the measurement is terminated.

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