Optical receiver frequency response calibration device and method

Abstract

The invention discloses an optical receiver frequency response calibration device and method. The optical receiver frequency response calibration device comprises an industrial personal computer and an optical receiver to be measured. The industrial control computer is in communication connection with a vector network analyzer, an optical transmitter, an optical amplifier, a variable optical attenuator, an optical switch and an optical power meter; the optical transmitter receives a radio frequency signal sent by the vector network analyzer, outputs a modulated optical signal, sequentially passes through the optical amplifier and the variable optical attenuator, and then passes through the optical switch to be divided into a first path and a second path; when the optical switch is switched to the first path, the modulated optical signal is received by the optical receiver to be detected; and when the optical switch is switched to the second path, the modulated optical signal is received by the optical power meter. The invention solves the problems of high environmental requirements, incapability of calibrating phase-frequency response, poor system integration and the like of the traditional optical heterodyne calibration method and microwave frequency scanning method in the device level, and the problems of large test data volume, many calibration files and low test efficiency in the method level.

Description

Technical Field

[0001] The present invention relates to the technical field of receiver frequency response calibration, and in particular, to an optical receiver frequency response calibration device and method. Background Art

[0002] With the development of new technologies such as 5G / 6G, data centers, and cloud computing, high-speed fiber optic communication networks have become the development trend of the next generation of optical communication. Optical receivers are crucial in fiber optic communication systems and electro-optic device frequency response parameter test systems. A typical fiber optic communication system is as Figure 1 shown. In a typical fiber optic communication system, the optical receiver is responsible for converting an optical signal into an electrical signal, and then demodulating the electrical signal through its subsequent electrical module, playing an important role in the system. Its frequency response calibration directly affects the accurate characterization of the electro-optic device under test. Currently, the main calibration methods are the optical heterodyne calibration method and the microwave frequency scanning method.

[0003] Optical heterodyne calibration method: As described in the paper "Research on the Test Method of the Frequency Response of High-Speed Photoelectric Detectors" (Fei Feng, Astronautic Metrology & Measurement Technology, Vol. 30, No. 1), as Figure 2 shown, the laser generated by a tunable external cavity laser and a fixed wavelength distributed feedback laser is input into a photodetector for mixing to generate a high-frequency modulated optical signal for testing. However, this method has many problems: when testing, it is necessary to ensure the wavelength stability of the two lasers. Otherwise, the frequency of the beat signal will shift, resulting in a large measurement error in the frequency response of the optical receiver, and high requirements for the measurement environment and instrument performance; it can only calibrate the amplitude-frequency response and cannot calibrate the phase-frequency response, affecting the performance of the test system; there are many separate instruments in the test system, the operation is complex, the test time is long, and the efficiency is low.

[0004] Microwave frequency scanning method: As Figure 3 shown, using the frequency scanning principle, a test system is built with discrete instruments to complete the test and calibration of the frequency response parameters of the optical receiver. However, although this method solves the problem that the optical heterodyne method has high requirements for both the measurement environment conditions and the performance of the test instrument, it still has problems such as poor system integration, difficult calibration, and large system errors.

[0005] In addition, since the frequency response of the optical receiver is different at different optical wavelengths, as a standard optical receiver module, it is necessary to test the frequency response data of all wavelength points in the full range. The existing technology usually performs frequency response tests for each wavelength point within the full wavelength range, and after the test is completed, the frequency response data file at that wavelength point is saved separately. Therefore, there will be multiple data files, resulting in problems such as a large amount of test data, many test files, and low test efficiency. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides an optical receiver frequency response calibration device and method. By constructing an optical receiver frequency response calibration device based on a vector network analyzer and adopting an optimized calibration method, the present invention solves the problems existing in the traditional optical heterodyne calibration method and microwave frequency scanning method at the device level, such as high environmental requirements, inability to calibrate the phase frequency response, and poor system integration, as well as the problems at the method level, such as large amounts of test data, many calibration files, and low test efficiency.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides an optical receiver frequency response calibration device, including: an industrial control computer and an optical receiver to be measured; the industrial control computer is communicatively connected to a vector network analyzer, an optical transmitter, an optical amplifier, an adjustable optical attenuator, an optical switch, and an optical power meter;

[0009] The optical transmitter receives the radio frequency signal sent by the vector network analyzer, outputs a modulated optical signal, and then sequentially passes through the optical amplifier and the adjustable optical attenuator, and is then divided into a first path and a second path through the optical switch; when the optical switch is switched to the first path, the modulated optical signal is received by the optical receiver to be measured; when the optical switch is switched to the second path, the modulated optical signal is received by the optical power meter.

[0010] As a further technical solution, the industrial control computer establishes a communication connection with the vector network analyzer, the optical transmitter, the optical amplifier, the adjustable optical attenuator, the optical switch, and the optical power meter respectively through a GPIB or LAN bus.

[0011] In the second aspect, the present invention provides an optical receiver frequency response calibration method, based on the optical receiver frequency response calibration device according to any one of the first aspect, including:

[0012] Sending a status initialization instruction through the industrial control computer, and setting the output optical power of the optical transmitter and the characteristic wavelength of the optical transmitter;

[0013] Switching the optical switch to the second path, and obtaining the current display value of the optical power meter;

[0014] Presetting a threshold value, comparing the difference between the set output optical power of the optical transmitter and the current display value of the optical power meter with the threshold value, and setting the amplification value of the optical amplifier or the attenuation value of the optical attenuator according to the comparison result;

[0015] Switching the optical switch to the first path, setting the basic parameters of the vector network analyzer, starting the test, collecting frequency response data, and obtaining a frequency response matrix;

[0016] Fit the frequency response matrix to obtain the "frequency response - characteristic wavelength" polynomial and the fitting coefficient matrix, thereby completing the frequency response calibration of the optical receiver.

[0017] As a further technical solution, the state initialization includes the calibration of the vector network analyzer, the zeroing of the variable optical attenuator and the optical power meter.

[0018] As a further technical solution, the specific method for setting the amplification value of the optical amplifier or the attenuation value of the optical attenuator according to the comparison result is: if P - P , ≥δ, set the amplification value of the optical amplifier to δ; if P - P , ≤ -δ, set the attenuation value of the optical attenuator to δ; where P is the output optical power of the set optical transmitter, P , is the current display value of the optical power meter, and δ is the threshold value.

[0019] As a further technical solution, the basic parameters set for the vector network analyzer include the start frequency, the stop frequency, and the number of scan points.

[0020] As a further technical solution, the specific representation of the frequency response matrix is:

[0021] where y 11 、y 12 …y 1n is the first row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ1; y 21 、y 22 …y 2n is the second row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ2; y m1 、y m2 …y 1n is the m-th row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ m .

[0022] As a further technical solution, perform polynomial fitting on the frequency response matrix column by column to fit and form n "frequency response - characteristic wavelength" polynomials, which are specifically represented as:

[0023] where a k1 、a k2 …a kn are the fitting coefficients, k is the degree of the polynomial, λ is the characteristic wavelength, and m is the number of characteristic wavelengths.

[0024] As a further technical solution, the method for the fitting coefficient matrix is to use the least squares method for fitting to obtain the fitting coefficient matrix as:

[0025] wherein, a coef is the fitting coefficient matrix, and a mn is an element in the fitting coefficient matrix.

[0026] As a further technical solution, after the frequency response calibration of the optical receiver is completed, calibration data is obtained, and the calibration data includes the frequency responses of m characteristic wavelengths and the fitting coefficient matrix.

[0027] One or more technical solutions of the present invention have the following beneficial effects:

[0028] (1) The present invention establishes an optical receiver frequency response calibration device based on instruments such as a vector network analyzer, a standard optical transmitter, an optical amplifier, a variable optical attenuator, an optical switch, and an optical power meter. Compared with the traditional optical heterodyne method, this device is simple, highly operable, and has high system stability; the use of the vector network analyzer enables the collected frequency response data to contain both amplitude information and phase information. Moreover, the cooperation of the optical amplifier, variable optical attenuator, and optical power meter eliminates the influence of optical power error on the calibration accuracy; the optical switch automatically switches the test link, avoiding the operation error caused by manual fiber plugging and unplugging, and improving the calibration accuracy.

[0029] (2) The present invention uses an industrial control computer for integrated control through the GPIB / LAN bus. Its advantages are that all operations are realized through remote control. On the one hand, it avoids the errors introduced by manual operations and improves the calibration accuracy. On the other hand, it improves the calibration efficiency.

[0030] (3) The present invention only collects the frequency response data at characteristic wavelength points instead of the entire wavelength range, which improves the collection efficiency. And through the use of the least squares fitting, the difference between the true value and the fitted value is restored to the greatest extent, making the fitting accuracy reach the highest. Moreover, the calibration data finally obtained by the present invention includes the frequency responses of m characteristic wavelengths and the fitting coefficient matrix, resulting in multiple data files, avoiding problems such as a large amount of test data, many test files, and low test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0032] Figure 1 is a schematic diagram of a typical optical fiber communication system mentioned in the background art of the present invention;

[0033] Figure 2 is a test block diagram of the optical heterodyne method for an optical receiver mentioned in the background art of the present invention;

[0034] Figure 3This is the test block diagram of the microwave frequency scanning method mentioned in the background art of the present invention;

[0035] Figure 4 This is the schematic diagram of the optical receiver frequency response calibration device of the present invention;

[0036] Figure 5 This is the flowchart of the optical receiver frequency response calibration method of the present invention. Detailed implementation manners

[0037] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0038] Example 1

[0039] The present invention provides an optical receiver frequency response calibration device. As Figure 4 shown in the schematic diagram of the optical receiver frequency response calibration device, the optical receiver frequency response calibration device in this embodiment includes an industrial control computer, a vector network analyzer, a standard optical transmitter, an optical amplifier, an adjustable optical attenuator, an optical switch, an optical power meter, and a to-be-tested optical receiver. Among them, the industrial control computer is communicatively connected to the vector network analyzer, the optical transmitter, the optical amplifier, the adjustable optical attenuator, the optical switch, and the optical power meter. Specifically: The industrial control computer establishes communication connections with the vector network analyzer, the optical transmitter, the optical amplifier, the adjustable optical attenuator, the optical switch, and the optical power meter through GPIB or LAN buses respectively, and uses the industrial control computer to perform integrated control through the GPIB / LAN buses. Its advantage is that all operations are realized through remote control. On the one hand, it avoids the errors introduced by manual operations and improves the calibration accuracy. On the other hand, it improves the calibration efficiency.

[0040] As Figure 1 shown, the standard optical transmitter receives the RF signal sent by the vector network analyzer. After outputting a modulated optical signal, it successively passes through the optical amplifier and the adjustable optical attenuator, and then is divided into the first path and the second path through the optical switch; when the optical switch is switched to the first path, the modulated optical signal is received by the to-be-tested optical receiver; when the optical switch is switched to the second path, the modulated optical signal is received by the optical power meter. The adjustable optical attenuator and the optical amplifier are used to cooperate with the optical power meter to ensure that the modulated optical signal input to the to-be-tested optical receiver meets the requirements of the set power; the optical switch realizes the switching of the optical signal between the to-be-tested optical receiver and the optical power meter, and completes the switching of different test links; the optical power meter detects the value of the modulated optical signal power in real time.

[0041] Example 2

[0042] In this embodiment, a method for calibrating the frequency response of an optical receiver is provided. Based on an optical receiver frequency response calibration device provided in Embodiment 1, as Figure 5 shown, the specific process is as follows:

[0043] For the following tests, the control of the vector network analyzer, standard optical transmitter, optical amplifier, variable optical attenuator, optical switch, and optical power meter is all achieved through remote control by an industrial control computer, and it also includes the setting of instrument parameters and the acquisition of data.

[0044] Send a status initialization instruction through the industrial control computer to complete the initialization of the instrument status. The status initialization includes the calibration of the vector network analyzer, the zeroing of the variable optical attenuator and the optical power meter.

[0045] Set the output optical power P of the standard optical transmitter and the characteristic wavelength λ of the optical transmitter;

[0046] Switch the optical switch to the second path and obtain the current display value P of the optical power meter , ;

[0047] Preset an error threshold and perform power value determination, including: comparing the difference between the set output optical power of the optical transmitter and the current display value of the optical power meter with the error threshold, and setting the amplification value of the optical amplifier or the attenuation value of the variable optical attenuator according to the comparison result;

[0048] The specific method for setting the amplification value of the optical amplifier or the attenuation value of the variable optical attenuator according to the comparison result is as follows: If P - P , ≥δ, set the amplification value of the optical amplifier to δ; if P - P , ≤ -δ, set the attenuation value of the variable optical attenuator to δ; where P is the set output optical power of the optical transmitter, P , is the current display value of the optical power meter, and δ is the threshold. Repeatedly obtain the current display value P of the optical power meter , , until the difference between P and P , is less than the threshold δ, that is, the power of the modulated optical signal meets the set requirements.

[0049] Switch the optical switch to the first path, set the basic parameters of the vector network analyzer. The basic parameters include the start frequency, stop frequency, and number of scan points; start the test, collect frequency response data, and obtain a frequency response matrix;

[0050] Among them, the method for obtaining the frequency response matrix is: sequentially set the output optical power and characteristic wavelength value of the standard optical transmitter, and complete the acquisition of frequency response data for n frequencies corresponding to m characteristic wavelengths respectively through the previous method. The formed frequency response matrix is as follows:

[0051] The rows of the matrix represent the frequency responses of n frequency points corresponding to the characteristic wavelength points, and the columns of the matrix represent the frequency responses corresponding to the same frequency point at m characteristic wavelengths. Among them, y 11 、y 12 …y 1n is the first row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ1; y 21 、y v2 …y 2n is the second row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ2; y m1 、y m2 …y 1n is the m-th row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ m .

[0052] The frequency response matrix is fitted to obtain the "frequency response - characteristic wavelength" polynomial and the fitting coefficient matrix, thus completing the frequency response calibration of the optical receiver.

[0053] Among them, polynomial fitting is performed on the frequency response matrix column by column, and n "frequency response - characteristic wavelength" polynomials are formed by fitting, which are specifically expressed as:

[0054] Among them, a k1 、a k2 …a kn are fitting coefficients, k is the degree of the polynomial, λ is the characteristic wavelength, and m is the number of characteristic wavelengths. To ensure that the difference between the fitting accuracy and the actual measured frequency response value is minimized, the least squares method is used for fitting in this embodiment, and the obtained fitting coefficient matrix is:

[0055] Among them, a coef is the fitting coefficient matrix, and a mn is an element in the fitting coefficient matrix.

[0056] According to the above method, the frequency response calibration of the optical receiver is completed. The calibration data finally obtained by the frequency response calibration of the optical receiver includes the frequency response touchstone file (s2p file) of a total of m characteristic wavelength points and the fitting coefficient matrix a coef . In actual engineering applications, when calibrating the frequency response of an optical receiver, the wavelength range of the optical receiver is [1260nm, 1610nm], and there are 8 characteristic wavelengths in total, namely 1260nm, 1310nm, 1360nm, 1410nm, 1460nm, 1510nm, 1550nm, and 1610nm.

[0057] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical receiver frequency response calibration device, characterized in that, Including: An industrial control computer and an optical receiver under test; the industrial control computer is communicatively connected to a vector network analyzer, an optical transmitter, an optical amplifier, a variable optical attenuator, an optical switch, and an optical power meter; The optical transmitter receives the radio frequency signal sent by the vector network analyzer, outputs a modulated optical signal, and then successively passes through the optical amplifier and the variable optical attenuator, and is divided into a first path and a second path after passing through the optical switch; when the optical switch is switched to the first path, the modulated optical signal is received by the optical receiver under test; when the optical switch is switched to the second path, the modulated optical signal is received by the optical power meter for monitoring the power of the modulated optical signal.

2. The optical receiver frequency response calibration device according to claim 1, characterized in that, The industrial control computer establishes a communication connection with the vector network analyzer, the optical transmitter, the optical amplifier, the variable optical attenuator, the optical switch, and the optical power meter respectively through the GPIB or LAN bus.

3. A method for calibrating the frequency response of an optical receiver, based on the optical receiver frequency response calibration device according to any one of claims 1-2, characterized in that, Including: Sending a status initialization instruction through the industrial control computer, and setting the output optical power of the optical transmitter and the characteristic wavelength of the optical transmitter; Switching the optical switch to the second path to obtain the current display value of the optical power meter; Presetting a threshold value, comparing the difference between the set output optical power of the optical transmitter and the current display value of the optical power meter with the threshold value, and setting the amplification value of the optical amplifier or the attenuation value of the optical attenuator according to the comparison result; Switching the optical switch to the first path, setting the basic parameters of the vector network analyzer, starting the test, collecting frequency response data, and obtaining a frequency response matrix; Fitting the frequency response matrix to obtain a "frequency response - characteristic wavelength" polynomial and a fitting coefficient matrix, thereby completing the frequency response calibration of the optical receiver.

4. The optical receiver frequency response calibration method according to claim 3, characterized in that The status initialization includes vector network analyzer calibration, variable optical attenuator and optical power meter zeroing.

5. The optical receiver frequency response calibration method according to claim 3, wherein The specific method for setting the amplification value of the optical amplifier or the attenuation value of the optical attenuator according to the comparison result is as follows: If P - P , ≥δ, set the amplification value of the optical amplifier to δ; if P - P , ≤ -δ, set the attenuation value of the optical attenuator to δ; where P is the output optical power of the set optical transmitter, P , is the current display value of the optical power meter, and δ is the threshold value.

6. The optical receiver frequency response calibration method according to claim 3, characterized in that The setting of the basic parameters of the vector network analyzer includes start frequency, stop frequency, and number of scan points.

7. The optical receiver frequency response calibration method according to claim 3, characterized in that, The specific representation of the frequency response matrix is: Among them, y 11 , y 12 …y 1n is the first row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ1; y 21 , y 22 …y 2n is the second row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ2; y m1 , y m2 …y 1n is the m-th row of the frequency response matrix, representing the frequency response when the characteristic wavelength is λ m .

8. The optical receiver frequency response calibration method according to claim 7, wherein Performing polynomial fitting on the frequency response matrix column by column, and fitting to form n "frequency response - characteristic wavelength" polynomials, specifically represented as: Among them, a k1 , a k2 … a kn are fitting coefficients, k is the degree of the polynomial, λ is the characteristic wavelength, and m is the number of characteristic wavelengths.

9. The optical receiver frequency response calibration method according to claim 3, wherein The method for the fitting coefficient matrix is to use the least squares method to fit, and the obtained fitting coefficient matrix is: Among them, a coef is the fitting coefficient matrix, and a mn is an element in the fitting coefficient matrix.

10. A method for calibrating the frequency response of an optical receiver according to claim 3, characterized in that, After completing the frequency response calibration of the optical receiver, calibration data is obtained, and the calibration data includes the frequency responses of m characteristic wavelengths and the fitting coefficient matrix.

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