A method for measuring photoelectric response of a photoelectric detector

Abstract

The application discloses a photoelectric response measurement method of a photoelectric detector, belongs to the field of optoelectronic technology, and aims to provide a wideband and low-cost method for measuring the frequency response of a photoelectric detector.In the application, the light signals output by a laser are modulated by signals output by a first signal source and a second signal source in an electro-optic intensity modulator; a control and data processing module is used to control the frequency of the signals output by the first signal source to be fixed and to change the frequency of the signals output by the second signal source, the modulated light signals are input into a photoelectric detector to be measured, a signal analysis module is used to analyze the frequency components output by the photoelectric detector to be measured, the frequency response of the electro-optic intensity modulator is extracted and eliminated, and finally the measurement of the photoelectric response of the photoelectric detector to be measured is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optoelectronics, and particularly relates to a method for measuring the photoelectric response of a photoelectric detector. BACKGROUND

[0002] As the most commonly used light-electricity conversion device, photoelectric detectors are widely used in optical communication links, data centers, microwave photon signal processing and other fields. The measurement of photoelectric frequency response is very important for the characterization of the performance of broadband photoelectric detectors. Accurate measurement of the photoelectric response of photoelectric detectors will also help to evaluate and optimize the ability of optoelectronic systems to transmit and process signals.

[0003] There are two main methods for measuring the photoelectric response of photoelectric detectors at present, namely all-optical excitation method and electro-optical excitation method. The all-optical excitation method mainly includes light wavelength beat frequency method and intensity noise method. The light wavelength beat frequency method uses two continuous wave lasers to beat each other through a photoelectric detector. By changing the wavelength of two or one of the lasers, the frequency response of the photoelectric detector in a wide frequency range can be measured. However, the frequency resolution of this method is limited by the wavelength adjustment accuracy of the laser, and the power stability of the laser is required to be high. The intensity noise method uses the wide spectrum signal output by the amplified spontaneous emission light source to measure the frequency response of the photoelectric detector, which has the characteristics of wide frequency range. However, the measurement accuracy of this method is very low, and the dynamic range is poor. The electro-optical excitation method uses the method of electro-optical modulation to generate high coherence optical sidebands, which has the hot spot of high frequency resolution and large dynamic range. The electro-optical excitation method mainly includes electro-optical sweep frequency method, dual-tone sweep frequency method and optical sampling method. The electro-optical sweep frequency method cascades a modulated laser or an electro-optical intensity modulator with known frequency response with the photoelectric detector to be measured. The photo-electric response of the photoelectric detector to be measured can be obtained by subtracting the electro-optical response from the measured cascade network electric-electric response. The electro-optical sweep frequency method requires an electro-optical device with known frequency response and the same bandwidth, which is not conducive to the measurement of broadband photoelectric detectors. The dual-tone sweep frequency method uses two microwave sweep sources with a fixed frequency interval for dual-tone modulation. The sum frequency and difference frequency signals output by the photoelectric detector are measured to obtain the frequency response of the photoelectric detector. SUMMARY

[0004] The present application provides a method for measuring the photoelectric response of a photoelectric detector, which has the characteristics of low cost, wide measurement frequency range and high resolution.

[0005] A method for measuring the photoelectric response of a photoelectric detector, characterized by the following steps and principles:

[0006] Step 1: Construct a photodetector photoelectric response measurement device, including a laser, an electro-optic intensity modulator, a photodetector under test, a signal analysis module, a first signal source, a second signal source, and a control and data processing module. The laser and the electro-optic intensity modulator are sequentially optically connected to the photodetector under test. The photodetector under test is electrically connected to the signal analysis module. The first and second signal sources are respectively electrically connected to the electro-optic intensity modulator. The control and data processing module is sequentially data-connected to the first signal source, the second signal source, and the signal analysis module.

[0007] Step 2: Determine the frequency f of the photoelectric response of the photodetector under test. M Set the frequency f of the first signal source. LO Second signal source signal frequency f IF , where the frequency f M Frequency f LO and frequency f IF The relation is: f M =kf LO ±f IF k can be either even or odd; frequency f LO f remains unchanged during the test. LO This frequency is generally approximately equal to the 3dB bandwidth cutoff frequency of the electro-optic intensity modulator, and then the frequency f is calculated. M Divide by frequency f LO The quotient, denoted as N, is such that when the parity of N matches the parity of the configured k, k = N. From this, the frequency f of the second signal source can be calculated. IF =f M –kf LO When the parity of N is inconsistent with the parity of the configured k, k = N + 1 is taken, and the frequency f of the second signal source can be calculated. IF =kf LO -f M ;

[0008] Step 3: The optical signal output from the laser is modulated by the first signal source and the second signal source respectively through the electro-optic intensity modulator. After the modulated optical signal is photoelectrically converted by the photodetector under test, the output photocurrent signal is collected and received by the signal analysis module. Step 4: The bias state of the electro-optic intensity modulator is set according to the parity of the configured k. When k is only an even number, the electro-optic intensity modulator is set to work at the linear transmission point; when k is only an odd number, the electro-optic intensity modulator is set to work at the maximum or minimum transmission point.

[0009] Step 5: Set the receiving frequency of the signal analysis module according to the parity of the configured k, and measure the photocurrent signal amplitude at the corresponding frequency; set the receiving frequency of the signal analysis module to f. M and (1+s)fLO And measure the amplitude of the electrical signal at the corresponding frequency as i(f) M ;f IF ) and i[(1+s)f LO ;f IF ], where s = 0, 1, corresponding to the cases where k is only even and only odd, respectively; Step 6: Change the frequency of the second signal source to f R f R Satisfy f R ≈f LO Similarly, the receiving frequency of the signal analysis module is set according to the parity of the configured k; the receiving frequency of the signal analysis module is then set to (2+s)f. LO -f R ,s·f LO +f R (2+s)f R -f LO and (1+s)f LO The amplitude of the electrical signal at the corresponding frequency is measured as i[(2+s)f LO -f R ;f R ]、i(s·f LO +f R ;f R ), i[(2+s)f R -f LO ;f R ] and i[(1+s)f LO ;f R ];

[0010] Step 7: Use the electrical signal amplitude i[(1+s)f measured in Step 5 LO ;f IF ] and the amplitude of the electrical signal i[(2+s)f measured in step 6 LO -f R ;f R ]、i(s·f LO +f R ;f R ), i[(2+s)f R -f LO ;f R ] and i[(1+s)f LO ;f R The modulation coefficient m1(f) of the electro-optic intensity modulator driven by the first signal source was calculated. LO ) and the modulation coefficient m2(f) driven by the second signal source R ) and m2(f IF For the case where k is only an even number, s = 0, and the calculation formula is:

[0011]

[0012] For the case where k is always odd, s = 1, the calculation formula is:

[0013]

[0014]

[0015] Among them, J n (m) is a Bessel function of the first kind, order n;

[0016] Step 8: Use the modulation coefficient m1(f) of the electro-optic intensity modulator calculated in Step 7. LO ) and m2(f IF ), and the electrical signal amplitude i(f) measured in step 4. M ;f IF The frequency of the photodetector under test at frequency f can be calculated using the following formula. M The photoelectric response is as follows:

[0017]

[0018] Step 9: Change the test frequency f M Repeat step 2 to calculate the corresponding frequency f. IF Repeat steps 3, 4, and 5 to measure the electrical signal amplitude i(f). M ;f IF ) and i[(1+s)f LO ;f IF Repeat step 7 to calculate the modulation coefficient m2(f) of the electro-optic intensity modulator. IF Then repeat step 8 to calculate the photodetector under test at frequency f. M The photoelectric response R(f) under the following conditions M From this, we can calculate different frequencies f. M The photoelectric response of the photodetector under test.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] I. This invention uses only one electro-optic intensity modulator for modulation, which has the characteristics of compact structure;

[0021] Second, this invention uses a fixed-frequency microwave signal source and a variable-frequency microwave signal source for modulation, which greatly reduces the cost of the test system, while maintaining the flexible and adjustable test frequency of the photoelectric response of the photodetector under test. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the device of the present invention.

[0023] Figure 2 This is a test result diagram when the parameter k described in this invention is only an even number.

[0024] Figure 3 This is a test result diagram when the parameter k described in this invention is only an odd number. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments. These embodiments are merely some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the protection scope of the present invention.

[0026] like Figure 1 As shown, the optical signal output by the laser is modulated by a first signal source and a second signal source, respectively. After the modulated optical signal is detected by a photodetector, a photocurrent signal is output. The control and data processing modules control the frequency of the first signal source to always be f. LO The frequencies of the second signal source are f IF and f R The signal analysis module measures different frequency components in the output photocurrent of the photodetector, and the photoelectric response of the photodetector can be calculated based on the measured amplitude information of the frequency components. The control and data processing module changes the frequency f of the second signal source. IF Repeating the above steps allows for testing of the photoelectric response of the photodetector at different frequency points.

[0027] To better explain the technical invention, the principles and methods of the invention are briefly described below:

[0028] The optical signal output from the Mach-Zehnder modulator, after being detected by the photodetector under test, has the following expression for the output photocurrent:

[0029]

[0030] In the formula, R is the responsivity of the photodetector under test, I0 is the intensity of the optical carrier signal, and γ is the splitting ratio of the Mach-Zehnder modulator. For the bias phase of the Mach-Zehnder modulator, m1(f LO ) is the output signal f of the first signal source LO The modulation coefficient of the Mach-Zehnder modulator driven by the driver, m2(f IF ) is the output signal f of the second signal source. IF The modulation coefficient of the driving Mach-Zehnder modulator.

[0031] According to formula (1), let k be a non-negative integer and q = 1. Then, the amplitude of the frequency component used to extract the frequency response of the photodetector under test can be obtained as follows:

[0032]

[0033] According to formula (2), the frequency point for measuring the frequency response of the photodetector under test is f. M =kf LO ±f IF Set f LO For a fixed frequency, typically around the 3dB bandwidth cutoff frequency of the electro-optic intensity modulator in the test system, then the parameters k and frequency f are varied. IF To adjust the frequency f for measuring the frequency response of the photodetector M To simplify formula (2), this method configures the parity of k+1, i.e., the parity of k, so that k is either only even or only odd during the measurement process. This is to select suitable parameters k and frequency f. IF Thus matching frequency f M Here, the frequency f is calculated. M With frequency f LO The quotient, denoted as N, is determined by the following formula: If the calculated quotient N has the same parity as the assigned k, then k = N. IF =f M –kf LO Calculate the required frequency f IF If the calculated quotient N does not have the same parity as the configured k, take k = N + 1, and then apply the formula f. IF =kf LO -f M Calculate the required frequency f IF .

[0034] For cases where k is only even or only odd, the bias phase of the Mach-Zehnder modulator is set accordingly. or The frequency component amplitude in formula (2) can be simplified to:

[0035] i(f M ;f IF )=4I0γJ k [m1(f LO )]J1[m2(f IF )]R(f M (3)

[0036] The control signal analysis module analyzes the frequency component (1+s)f LO The measurement was performed, and the amplitude was recorded as i[(1+s)f LO ;f IF], where s = 0 and 1, corresponding to the cases where k is only even and only odd, respectively. The output signal frequency of the second signal source is set to f. R The amplitudes measured using the signal analysis module are recorded as i[(2+s)f LO -f R ;f R ]、i(s·f LO +f R ;f R ), i[(2+s)f R -f LO ;f R ] and i[(1+s)f LO ;f R ]. Because f R ≈f LO Satisfy R[(2+s)f LO -f R ]≈R(s·f LO +f R )≈R[(2+s)f R -f LO ]≈R[(1+s)f LO The modulation coefficient m1(f) of the Mach-Zehnder modulator can be obtained. LO m2(f) R ) and m2(f IF The formula for calculating ) is:

[0037]

[0038] Or:

[0039]

[0040] The frequency response amplitude i(f) measured using the signal analysis module M ;f IF Based on formula (3) and formulas (4) to (6) or formulas (7) to (9), the frequency response J of the electro-optic intensity modulator is subtracted. k [m1(f LO )] and J1[m2(f IF From this, the photoelectric response of the photodetector under test can be obtained as follows:

[0041]

[0042] Finally, based on formula (10), the output signal frequency f of the first signal source is fixed. LO Adjust the frequency f M Calculate the corresponding frequency f M The frequency f below IFChange the output signal frequency f of the second signal source IF By repeating the above steps, different frequencies f can be measured. M The photoelectric response of the photodetector under test at the location.

[0043] Example 1

[0044] In this embodiment, the k parameter is only an even number. First, the test frequency for the photoelectric response of the photodetector under test is determined to be 50MHz (f... M ) and 19.96GHz (f M The electro-optic intensity modulator used has a 3dB bandwidth of approximately 10GHz, therefore the output signal frequency of the first signal source is set to 10.005GHz (f). LO Dividing 50MHz and 19.96GHz by 10.005GHz respectively yields quotients of 0 and 1. Therefore, setting k values ​​to 0 and 2 respectively, the frequency f of the second signal source is calculated. IF These are 50MHz = 50MHz – 0 × 10.005GHz (f) M –0×f LO ), 50MHz=2×10.005GHz–19.96GHz(2f LO -f M Therefore, the frequency f of the second signal source is set. IF Both are 50MHz. The optical signal with an output frequency of 193.1THz from the laser is sent to the electro-optic intensity modulator, and is modulated by the first signal source with a frequency of 10.005GHz (f). LO The microwave signal and the second signal source have a frequency of 50MHz (f IF The microwave signal is modulated, and the modulated optical signal is sent to the photodetector under test for detection. The detected photocurrent is received by the signal analysis module. The electro-optic intensity modulator is set to operate at the linear transmission point, and the frequency is measured using the signal analysis module at 50MHz (f... M =f IF ), 19.96GHz (f M =2f LO -f IF ) and 10.005GHz (f LO The frequency component amplitude information is recorded as i(f) IF ;f IF )=-46.75dBm、i(2f LO -f IF ;f IF ) = -43.91dBm and i(f LO ;f IF = -47.83dBm. The second signal source frequency is set to 10.05GHz (fR The frequencies measured using the signal analysis module were 9.96 GHz (2f). LO -f R ), 10.05GHz (f R ), 10.095GHz (2f R -f LO ) and 10.005GHz (f LO The frequency component amplitude information is recorded as i(2f) LO -f R ;f R ) = -45.15dBm, i(f R ;f R )=-48.87dBm、i(2f R -f LO ;f R ) = -64.06dBm and i(f LO ;f R = -46.34 dBm. Using amplitude information i(2f) LO -f R ;f R ) = -45.15dBm and i(f R ;f R )=-48.87dBm, based on formula (4), the modulation coefficient m1 (10.005GHz) of the electro-optic intensity modulator modulated by the first signal source is calculated to be 3.18rad; using the amplitude information i(2f R -f LO ;f R ) = -64.06dBm and i(f LO ;f R The modulation coefficient m2 (10.05 GHz) of the electro-optic intensity modulator modulated by the second signal source is calculated to be 0.94 rad based on formula (5) and the amplitude information i(f) is then used. LO ;f IF ) = -47.83dBm and i(f LO ;f R The modulation coefficient m2 (50MHz) of the electro-optic intensity modulator modulated by the second signal source is calculated to be 1.21rad based on formula (6) = -46.34dBm. Substituting the modulation coefficients m1 (10.005GHz) = 3.18rad and m2 (50MHz) = 1.21rad into formula (10), the amplitude information i(f) is used to calculate the modulation coefficient m2 (50MHz) of the second signal source modulator. IF ;f IF ) = -46.75dBm and i(2f LO -f IF ;f IFThe calculation yields -43.91 dBm for the photodetector under test at frequencies of 50 MHz (f M =f IF ) and 19.96GHz (f M =2f LO -f IF The photoelectric responses at 19.96 GHz and 50 MHz are -30.71 dB and -31.61 dB, respectively. Therefore, the relative frequency response of the photodetector under test at 19.96 GHz relative to 50 MHz can be calculated to be -0.90 dB. Repeating the above steps, the photoelectric response of the photodetector under test in the measurement frequency range of 50 MHz to 30.06 GHz can be obtained, as shown below. Figure 2 As shown.

[0045] Example 2

[0046] In this embodiment, the k parameter is only an odd number. First, the test frequency for the photoelectric response of the photodetector under test is determined to be 50MHz (f...). M ) and 19.96GHz (f M The electro-optic intensity modulator used has a 3dB bandwidth of approximately 10GHz, therefore the frequency of the first signal source is set to 10.005GHz (f). LO Dividing 50MHz and 19.96GHz by 10.005GHz respectively yields quotients of 0 and 1. Therefore, setting the value of k to 1 for both, the frequency f of the second signal source is calculated. IF These are 9.955GHz = 10.005GHz – 50MHz (f LO -f M ), 9.955GHz=19.96GHz–10.005GHz(f M -f LO Therefore, the frequency f of the second signal source is set. IF Both are 9.955 GHz. The optical signal output from the laser at a frequency of 193.1 THz is fed into an electro-optic intensity modulator, and is modulated by a first signal source at a frequency of 10.005 GHz (f...). LO The microwave signal and the second signal source have a frequency of 9.955 GHz (f IF The microwave signal is modulated, and the modulated optical signal is sent to the photodetector under test for detection. The detected photocurrent is received by the signal analysis module. The electro-optic intensity modulator is set to operate at its maximum transmission point, and the frequency is measured using the signal analysis module at 50MHz (f... M =f LO -f IF ), 19.96GHz (f M =f LO +f IF ) and 20.01GHz (2f LOThe amplitude information of the frequency component is recorded as i(f). LO -f IF ;f IF ) = -48.10dBm, i(f LO +f IF ;f IF ) = -49.01dBm and i(2f LO ;f IF = -38.85dBm. The second signal source frequency is set to 10.05GHz (f R The frequencies measured using the signal analysis module were 19.965 GHz (3f). LO -f R ), 20.145GHz (3f) R -f LO ), 20.055GHz (f LO +f R ) and 20.01GHz (2f LO The amplitude information of the frequency component is recorded as i(3f). LO -f R ;f R ) = -47.28dBm, i(3f R -f LO ;f R ) = -77.48dBm, i(f LO +f R ;f R ) = -49.3dBm and i(2f LO ;f R = -38.71dBm. Using amplitude information i(3f) LO -f R ;f R ) = -47.28dBm and i(f LO +f R ;f R = -49.3dBm, and based on formula (7), the modulation coefficient m1 (10.005GHz) of the electro-optic intensity modulator modulated by the first signal source is calculated to be 3.18rad; using the amplitude information i (3f R -f LO ;f R ) = -77.48dBm and i(f LO +f R ;f R = -49.3dBm, and based on formula (8), the modulation coefficient m2 (10.05GHz) of the electro-optic intensity modulator modulated by the second signal source is calculated to be 0.94rad. Using amplitude information i(2f LO ;f IF) = -38.85dBm and i(2f LO ;f R = -38.71dBm, and based on formula (9), the modulation coefficient m2 (9.955GHz) of the electro-optic intensity modulator modulated by the second signal source is calculated to be 0.97rad. Substituting the modulation coefficients m1 (10.005GHz) = 3.18rad and m2 (9.955GHz) = 0.97rad into formula (10), and using the amplitude information i(f LO -f IF ;f IF ) = -48.10 dBm and i(f LO +f IF ;f IF = -49.01dBm, the calculated value of the photodetector under test at a frequency of 50MHz (f M =f LO -f IF ) and 19.96GHz (f M =f LO +f IF The photoelectric responses at 19.96 GHz and 50 MHz are -29.38 dB and -30.29 dB, respectively. Therefore, the relative frequency response of the photodetector under test at 19.96 GHz relative to 50 MHz can be calculated to be -0.91 dB. Repeating the above steps, the photoelectric response of the photodetector under test in the measurement frequency range of 50 MHz to 30.06 GHz can be obtained, as shown below. Figure 3 As shown.

Claims

1. A method for measuring the photoelectric response of a photodetector, characterized in that, Includes the following steps: Step 1: Construct a photodetector photoelectric response measurement device, including a laser, an electro-optic intensity modulator, a photodetector under test, a signal analysis module, a first signal source, a second signal source, and a control and data processing module. The laser and the electro-optic intensity modulator are sequentially optically connected to the photodetector under test. The photodetector under test is electrically connected to the signal analysis module. The first and second signal sources are respectively electrically connected to the electro-optic intensity modulator. The control and data processing module is sequentially data-connected to the first signal source, the second signal source, and the signal analysis module. Step 2: Determine the frequency f of the photoelectric response of the photodetector under test. M Set the frequency f of the first signal source. LO Second signal source signal frequency f IF , where the frequency f M Frequency f LO and frequency f IF The relation is: f M =kf LO ±f IF k can be either even or odd; determine the frequency f of the first signal source. LO Then calculate the frequency f M Divide by frequency f LO The quotient, denoted as N, is such that when the parity of N matches the parity of the configured k, k = N. From this, the frequency f of the second signal source can be calculated. IF =f M –kf LO When the parity of N is inconsistent with the parity of the configured k, k = N + 1 is taken, and the frequency f of the second signal source can be calculated. IF =kf LO -f M ; Step 3: The optical signal output by the laser is modulated by the first signal source and the second signal source respectively through the electro-optic intensity modulator. After the modulated optical signal is converted by the photodetector under test, the output photocurrent signal is collected and received by the signal analysis module. Step 4: Set the bias state of the electro-optic intensity modulator according to the parity of the configured k. When k is only an even number, the electro-optic intensity modulator is set to work at the linear transmission point; when k is only an odd number, the electro-optic intensity modulator is set to work at the maximum or minimum transmission point. Step 5: Set the receiving frequency of the signal analysis module according to the parity of the configured k, and measure the photocurrent signal amplitude at the corresponding frequency; set the receiving frequency of the signal analysis module to f. M and (1+s)f LO And measure the amplitude of the electrical signal at the corresponding frequency as i(f) M ;f IF ) and i[(1+s)f LO ;f IF ], where s = 0 and 1, corresponding to the cases where k is only even and only odd, respectively; Step 6: Change the frequency of the second signal source to f R f R Satisfy f R ≈f LO Similarly, the receiving frequency of the signal analysis module is set according to the parity of the configured k; the receiving frequency of the signal analysis module is then set to (2+s)f. LO -f R ,s·f LO +f R (2+s)f R -f LO and (1+s)f LO The amplitude of the electrical signal at the corresponding frequency is measured as i[(2+s)f LO -f R ;f R ]、i(s·f LO +f R ;f R ), i[(2+s)f R -f LO ;f R ] and i[(1+s)f LO ;f R ]; Step 7: Use the electrical signal amplitude i[(1+s)f measured in Step 5 LO ;f IF ] and the amplitude of the electrical signal i[(2+s)f measured in step 6 LO -f R ;f R ]、i(s·f LO +f R ;f R ), i[(2+s)f R -f LO ;f R ] and i[(1+s)f LO ;f R The modulation coefficient m1(f) of the electro-optic intensity modulator driven by the first signal source was calculated. LO ) and the modulation coefficient m2(f) driven by the second signal source R ) and m2(f IF For the case where k is only an even number, s = 0, and the calculation formula is: For the case where k is always odd, s = 1, the calculation formula is: Among them, J n (m) is a Bessel function of the first kind, order n; Step 8: Use the modulation coefficient m1(f) of the electro-optic intensity modulator calculated in Step 7. LO ) and m2(f IF ), and the electrical signal amplitude i(f) measured in step 4. M ;f IF The frequency of the photodetector under test at frequency f can be calculated using the following formula. M The photoelectric response is as follows: Step 9: Change the test frequency f M Repeat step 2 to calculate the corresponding frequency f. IF Repeat steps 3, 4, and 5 to measure the electrical signal amplitude i(f). M ;f IF ) and i[(1+s)f LO ;f IF Repeat step 7 to calculate the modulation coefficient m2(f) of the electro-optic intensity modulator. IF Then repeat step 8 to calculate the photodetector under test at frequency f. M The photoelectric response R(f) under the following conditions M From this, we can calculate different frequencies f. M The photoelectric response of the photodetector under test will be measured at different frequencies f. M The photoelectric response R(f) under the following conditions M Compared to low frequency f M By performing normalization, the relative frequency response of the photodetector under test can be obtained.

2. The photoelectric response measurement method for a photodetector according to claim 1, characterized in that, In step 2, the frequency f of the first signal source LO The frequency f remains constant throughout the test. LO This is the 3dB bandwidth cutoff frequency of the electro-optic intensity modulator.

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