Chirp parameter measuring device and method based on directly modulated laser optical module

Abstract

The invention relates to the technical field of photoelectronics, and discloses a chirp parameter measuring device and method based on a directly modulated laser optical module, and the device comprises an arbitrary waveform generator, an optical module, a tunable dispersion compensation module, and an oscilloscope. The optical module comprises a directly modulated laser; the output of the arbitrary waveform generator is electrically connected with the radio frequency input port of the directly modulated laser; the output optical signal end of the directly modulated laser is connected with the input optical end of the adjustable dispersion compensation module; the adjustable dispersion compensation module is used for controlling dynamic switching between a zero dispersion state and a preset non-zero dispersion state by introducing dispersion into a link, and an output optical signal port of the adjustable dispersion compensation module is optically connected with a receiving port of the optical module; and the radio frequency output end of the optical module is electrically connected with the oscilloscope. According to the invention, the problems of long chirp parameter test time and high measurement cost in the prior art are solved, and the chirp parameter measurement method has the characteristic of being capable of realizing rapid and accurate chirp parameter measurement.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technology, and more particularly to a chirp parameter measurement device and method based on a directly modulated laser optical module. Background Art

[0002] In high-speed fiber-optic communication systems, directly modulated lasers (DMLAs) have become a mainstream choice for optical module design due to their low cost, ease of integration, and low energy consumption. However, DMLA-based optical modules can produce optical signal chirp, a significant factor limiting the high-speed, high-quality transmission of communication networks and a crucial parameter for evaluating optical module quality. Particularly in dispersive channels, transient chirp and adiabatic chirp interact with dispersion, not only affecting the channel transmission response but also introducing severe nonlinear effects. Therefore, accurately measuring the chirp parameters of DMLA-based optical modules is crucial to understanding system damage mechanisms, optimizing system performance, and extending transmission distances.

[0003] Currently, there are two main methods for measuring chirp parameters: optical domain measurement and electrical domain measurement. The optical domain measurement method measures the optical signal directly in the optical domain, without passing it through a photodetector. A typical example is the spectrum analysis method, which uses a spectrometer to measure the wavelength offset of the "1" signal relative to the "0" signal to assess the frequency chirp of the DML. However, this method is significantly limited by the resolution of the spectrum analyzer. Currently, the resolution of commercial grating spectrometers is only 0.02nm (2.5GHz) around 1550nm, resulting in poor measurement accuracy. The electrical domain measurement method converts the optical signal through a photodetector to an electrical signal for measurement. These methods primarily include the bandpass filter method and the dispersive single-mode fiber method. Both methods rely on a vector network analyzer (VNA) for electrical spectrum analysis, which increases testing time and is inconvenient for long-term on-site monitoring, increasing measurement costs.

[0004] Therefore, the existing technology has the problems of long chirp parameter testing time and high measurement cost. Therefore, how to invent a device that can monitor chirp parameters online for a long time is a technical problem that needs to be solved urgently in this technical field. Summary of the Invention

[0005] In order to solve the problems of long chirp parameter testing time and high measurement cost in the prior art, the present invention provides a chirp parameter measurement device and method based on a directly modulated laser optical module, which has the characteristics of being able to achieve fast and accurate chirp parameter measurement.

[0006] In order to achieve the above-mentioned purpose of the present invention, the technical solutions adopted are as follows:

[0007] A chirp parameter measurement device based on a directly modulated laser optical module comprises an arbitrary waveform generator, an optical module, a tunable dispersion compensation module, and an oscilloscope; the optical module comprises a directly modulated laser; the arbitrary waveform generator output is electrically connected to the radio frequency input port of the directly modulated laser; the output optical signal end of the directly modulated laser is connected to the input optical end of the adjustable dispersion compensation module; the adjustable dispersion compensation module is used to control dynamic switching between a zero dispersion state and a preset non-zero dispersion state by introducing dispersion into a link, and its output optical signal port is optically connected to a receiving port of the optical module; the radio frequency output end of the optical module is electrically connected to the oscilloscope.

[0008] Preferably, the optical module also includes a photodetector; the photodetector is used to perform photoelectric conversion on the optical signal output by the tunable dispersion compensation module, its receiving end is optically connected to the output optical signal port of the adjustable dispersion compensation module, and its RF output end is electrically connected to the oscilloscope.

[0009] A parameter measurement method of a chirp parameter measurement device based on a directly modulated laser optical module comprises the following steps:

[0010] Generate multi-tone microwave signals through an arbitrary waveform generator;

[0011] By adjusting the dispersion value of the tunable dispersion compensation module to 0, the corresponding reference frequency response is obtained based on the dispersion-free signal acquired by the oscilloscope;

[0012] Dispersion is introduced into the link using a tunable dispersion compensation module. The corresponding acquired frequency response is obtained based on the signal after the introduction of dispersion acquired by an oscilloscope. The reference frequency response is subtracted from the acquired frequency response to obtain the measured dispersion channel frequency response.

[0013] The chirp parameters of the directly modulated laser optical module are fitted based on the measured dispersion channel frequency response to obtain the chirp parameter measurement results.

[0014] Preferably, the multi-tone microwave signal is specifically:

[0015]

[0016] Where N is the number of channels of the multi-tone signal, f i =(i-0.5)f c is the designed frequency point, f c is the interval between adjacent frequency points, A0 is the initial amplitude of the multi-tone signal, is the initial phase.

[0017] Furthermore, by adjusting the dispersion value of the tunable dispersion compensation module to 0, the corresponding reference frequency response is obtained based on the dispersion-free signal collected by the oscilloscope. The specific steps are as follows:

[0018] The dispersion value of the tunable dispersion compensation module is adjusted to 0, and the optical signal output by the dispersion compensation module is input into the module for photoelectric conversion, and then the output analog electrical signal is input into the oscilloscope;

[0019] Perform Fourier transform on the signal collected by the oscilloscope to obtain the frequency point f i The value at The frequency response of the reference is obtained as ω is f i The corresponding angular frequency.

[0020] Furthermore, based on the dispersion signal collected by the oscilloscope, the corresponding collected frequency response is obtained. The specific steps are as follows:

[0021] The dispersion value of the tunable dispersion compensation module is set, and the optical signal output by the dispersion compensation module is input into the module for photoelectric conversion, and then the output analog electrical signal is input into the oscilloscope;

[0022] Perform Fourier transform on the signal collected by the oscilloscope to obtain the frequency point f i The value at The acquired frequency response is

[0023] Furthermore, the measured dispersion channel frequency response is obtained, specifically:

[0024] Furthermore, the chirp parameters of the directly modulated laser optical module are fitted based on the actual dispersion channel frequency response to obtain the chirp parameter measurement results. The specific steps are as follows:

[0025] Construct the frequency point f according to the dispersion channel transfer function under the small signal model i The dispersion channel frequency response at , the theoretical value is obtained

[0026] Will and theoretical value The difference is taken as the error, and the minimum value of the sum of squares of the errors is found;

[0027] The minimum value obtained corresponds to the linewidth enhancement factor and the adiabatic chirp coefficient of the directly modulated laser; the linewidth enhancement factor and the adiabatic chirp coefficient are used as chirp parameter measurement results.

[0028] Furthermore, the theoretical value of the dispersion channel frequency response at each frequency point is based on the dispersion channel transfer function of the directly modulated laser under small signal conditions:

[0029]

[0030] Among them, the first The second term represents the frequency response of the interaction between transient chirp and dispersion. is the frequency response of the interaction between adiabatic chirp and dispersion, P bias is the output optical power of the directly modulated laser under the bias voltage, θ i is the phase change caused by dispersion, λ is the operating wavelength, c is the speed of light, D·L is the dispersion value set by the tunable dispersion compensation module, α is the linewidth enhancement factor, and κ is the adiabatic chirp coefficient.

[0031] Furthermore, The difference from the theoretical value is taken as the error, and the minimum value of the sum of squares of the errors is found. The specific steps are:

[0032] Will The difference from the theoretical value is taken as the error:

[0033]

[0034] Construct the sum of squared error function:

[0035]

[0036] Where N is the total number of frequency points;

[0037] Set the initial values of α and κ to [α0,κ0], and use the numerical optimization algorithm to change α and κ to minimize the SSE.

[0038] The beneficial effects of the present invention are as follows:

[0039] The present invention discloses a chirp parameter measurement device based on a directly modulated laser optical module, which includes an arbitrary waveform generator, an optical module, a tunable dispersion compensation module, and an oscilloscope. Compared with traditional measurement devices using optical fibers, the present invention uses a tunable dispersion compensation module, which can more flexibly control the dispersion value in the link, while avoiding the loss difference caused by different optical fiber lengths, and the measurement results are more accurate. The present invention adopts an arbitrary waveform generator to achieve a single acquisition of the system frequency response based on a multi-tone signal, and indirectly measures the chirp characteristic parameters of the directly modulated laser optical module. Compared with the traditional method of using a single-tone signal sweep measurement, this method is simpler to implement and has a faster measurement speed, and can meet the needs of online long-term monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of a chirp parameter measurement device based on a directly modulated laser optical module of the present invention.

[0041] Figure 2 The present invention is a flow chart of a parameter measurement method of a chirp parameter measurement device based on a directly modulated laser optical module.

[0042] Figure 3 It is a schematic diagram of the frequency response measurement and theoretical fitting curve results of the directly modulated laser optical module in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] like Figure 1 As shown, a chirp parameter measurement device based on a directly modulated laser optical module includes an arbitrary waveform generator, an optical module, a tunable dispersion compensation module, and an oscilloscope. The optical module includes a directly modulated laser; the arbitrary waveform generator output is electrically connected to the RF input port of the directly modulated laser; the output optical signal port of the directly modulated laser is connected to the input optical port of the tunable dispersion compensation module; the tunable dispersion compensation module is used to control the dynamic switching between a zero dispersion state and a preset non-zero dispersion state by introducing dispersion into the link; its output optical signal port is optically connected to the receiving port of the optical module; the RF output port of the optical module is electrically connected to the oscilloscope. The arbitrary waveform generator is used to generate and output a multi-tone microwave signal; the RF input port of the optical module is connected to the arbitrary waveform generator, which modulates the electrical signal onto an optical carrier.

[0046] The optical module also includes a photodetector; the photodetector is used to perform photoelectric conversion on the optical signal output by the tunable dispersion compensation module, its receiving end is optically connected to the output optical signal port of the adjustable dispersion compensation module, and its radio frequency output end is electrically connected to the oscilloscope.

[0047] Example 2

[0048] like Figure 2 As shown, a parameter measurement method of a chirp parameter measurement device based on a directly modulated laser optical module includes the following steps:

[0049] Generate multi-tone microwave signals through an arbitrary waveform generator;

[0050] By adjusting the dispersion value of the tunable dispersion compensation module to 0, the corresponding reference frequency response is obtained based on the dispersion-free signal acquired by the oscilloscope;

[0051] Dispersion is introduced into the link using a tunable dispersion compensation module. The corresponding acquired frequency response is obtained based on the signal after the introduction of dispersion acquired by an oscilloscope. The reference frequency response is subtracted from the acquired frequency response to obtain the measured dispersion channel frequency response.

[0052] The chirp parameters of the directly modulated laser optical module are fitted based on the measured dispersion channel frequency response to obtain the chirp parameter measurement results.

[0053] In a specific embodiment, the multi-tone microwave signal is specifically:

[0054]

[0055] Where N is the number of channels of the multi-tone signal, f i =(i-0.5)f c is the designed frequency point, f c is the interval between adjacent frequency points, A0 is the initial amplitude of the multi-tone signal, is the initial phase.

[0056] In a specific embodiment, by adjusting the dispersion value of the tunable dispersion compensation module to 0, a corresponding reference frequency response is obtained based on the frequency point of the dispersion-free signal acquired by the oscilloscope. The specific steps are as follows:

[0057] The dispersion value of the tunable dispersion compensation module is adjusted to 0, and the optical signal output by the dispersion compensation module is input into the module for photoelectric conversion, and then the output analog electrical signal is input into the oscilloscope;

[0058] Perform Fourier transform on the signal collected by the oscilloscope to obtain the frequency point f i The value at The frequency response of the reference is obtained as ω is f i The corresponding angular frequency.

[0059] In a specific embodiment, the corresponding frequency response of the dispersion signal collected by the oscilloscope is obtained by the following specific steps:

[0060] The dispersion value of the tunable dispersion compensation module is set, and the optical signal output by the dispersion compensation module is input into the module for photoelectric conversion, and then the output analog electrical signal is input into the oscilloscope;

[0061] Perform Fourier transform on the signal collected by the oscilloscope to obtain the frequency point f i The value at The acquired frequency response is

[0062] In a specific embodiment, the measured dispersion channel frequency response is obtained by:

[0063] In a specific embodiment, the chirp parameters of the directly modulated laser optical module are fitted based on the actual dispersion channel frequency response to obtain the chirp parameter measurement results, and the specific steps are as follows:

[0064] Construct the theoretical value of the frequency response of the dispersion channel at each frequency point, including the chirp parameter and linewidth enhancement factor;

[0065] Will The difference from the theoretical value is taken as the error, and the minimum value of the sum of squares of the errors is sought;

[0066] The minimum value obtained corresponds to the linewidth enhancement factor and the adiabatic chirp coefficient of the directly modulated laser; the linewidth enhancement factor and the adiabatic chirp coefficient are used as chirp parameter measurement results.

[0067] In a specific embodiment, the theoretical value of the dispersion channel frequency response at each frequency point is based on the dispersion channel transfer function of the DML-DD system under small signal conditions:

[0068]

[0069] Among them, the first The second term represents the frequency response of the interaction between transient chirp and dispersion. is the frequency response of the interaction between adiabatic chirp and dispersion, P bias is the output optical power of the directly modulated laser under the bias voltage, θ i is the phase change caused by dispersion, λ is the operating wavelength, c is the speed of light, D·L is the dispersion value set by the tunable dispersion compensation module, α is the chirp parameter, κ is the linewidth enhancement factor,

[0070] In a specific embodiment, The difference from the theoretical value is taken as the error, and the minimum value of the sum of squares of the errors is found. The specific steps are:

[0071] Will The difference from the theoretical value is taken as the error:

[0072]

[0073] Construct the sum of squared error function:

[0074]

[0075] Where N is the total number of frequency points;

[0076] Set the initial values of α and κ to [α0,κ0], and use the numerical optimization algorithm to change α and κ to minimize the SSE.

[0077] Example 3

[0078] In this embodiment, the parameter measurement method of the chirp parameter measurement device based on the direct-modulated laser optical module is used to conduct an experiment. The output light center wavelength of the direct-modulated laser optical module to be measured used in this embodiment is 1547.3nm, and the output light power P biasThe digital multi-tone signal is converted from digital to analog by an arbitrary waveform generator and modulated onto the optical carrier of the direct-modulated laser to be tested. The starting frequency of the multi-tone signal is 0.25 GHz and the frequency interval is f c The initial amplitude is A0 and the initial phase is

[0079] Set the dispersion value of the tunable dispersion compensation module to 0, use the optical module to complete the photoelectric detection, and the oscilloscope receives the multi-tone signal to obtain the reference frequency response. And recorded as curve A, which represents the frequency response of the system when there is no dispersion.

[0080] The dispersion value DL of the tunable dispersion compensation module is set to 102ps / nm, dispersion is introduced into the link, and the frequency response curve B containing the dispersion channel is obtained. The measured dispersion channel frequency response is obtained by subtracting curve A from curve B.

[0081] Using the dispersion channel transfer function of the DML-DD system under small signal And the resulting dispersion channel frequency response Perform parameter fitting.

[0082] In this embodiment, the initial search value is set to [3, 10e12] to find the minimum value of the sum of squared errors. The α and κ corresponding to this minimum value are the estimated linewidth enhancement factor and adiabatic chirp coefficient of the directly modulated laser.

[0083] Use either the least squares method or the gradient descent method to change α and κ to minimize SSE.

[0084] The measured dispersion channel frequency response and the theoretical fitting frequency response results are as follows: Figure 3 As shown in Figure 3, the experimentally measured linewidth enhancement factor α and adiabatic chirp coefficient κ are 3.2 and 9.43 GHz / mW, respectively.

[0085] Obviously, the above embodiments of the present invention are merely examples for the purpose of illustrating the present invention, and are not intended to limit the embodiments of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A chirp parameter measurement device based on a directly modulated laser optical module, characterized by: Including arbitrary waveform generator, optical module, tunable dispersion compensation module, oscilloscope; The optical module includes a directly modulated laser; the output of the arbitrary waveform generator is electrically connected to the radio frequency input port of the directly modulated laser; the output optical signal end of the directly modulated laser is connected to the input optical end of the adjustable dispersion compensation module; the adjustable dispersion compensation module is used to control the dynamic switching between the zero dispersion state and the preset non-zero dispersion state by introducing dispersion into the link, and its output optical signal port is optically connected to the receiving port of the optical module; the radio frequency output end of the optical module is electrically connected to the oscilloscope.

2. The chirp parameter measurement device based on a directly modulated laser optical module according to claim 1, characterized in that: The optical module also includes a photodetector; the photodetector is used to perform photoelectric conversion on the optical signal output by the tunable dispersion compensation module, its receiving end is optically connected to the output optical signal port of the adjustable dispersion compensation module, and its radio frequency output end is electrically connected to the oscilloscope.

3. A parameter measurement method for a chirp parameter measurement device based on a directly modulated laser optical module, characterized in that: The following steps are involved: Generate multi-tone microwave signals through an arbitrary waveform generator; By adjusting the dispersion value of the tunable dispersion compensation module to 0, the corresponding reference frequency response is obtained based on the dispersion-free signal acquired by the oscilloscope; Dispersion is introduced into the link using a tunable dispersion compensation module. The corresponding acquired frequency response is obtained based on the signal after the introduction of dispersion acquired by an oscilloscope. The reference frequency response is subtracted from the acquired frequency response to obtain the measured frequency response of the dispersive channel. The chirp parameters of the directly modulated laser optical module are fitted based on the measured dispersion channel frequency response to obtain the chirp parameter measurement results.

4. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 3, characterized in that: The multi-tone microwave signal is specifically: Where N is the number of channels of the multi-tone signal, f i =(i-0.5)f c is the designed frequency point, f c is the interval between adjacent frequency points, A0 is the initial amplitude of the multi-tone signal, is the initial phase.

5. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 3, characterized in that: By adjusting the dispersion value of the tunable dispersion compensation module to 0, the corresponding reference frequency response is obtained based on the dispersion-free signal acquired by the oscilloscope. The specific steps are as follows: The dispersion value of the tunable dispersion compensation module is adjusted to 0, and the optical signal output by the dispersion compensation module is input into the module for photoelectric conversion, and then the output analog electrical signal is input into the oscilloscope; Perform Fourier transform on the signal collected by the oscilloscope to obtain the frequency point f i The value at The frequency response of the reference is obtained as ω is f i The corresponding angular frequency.

6. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 5, characterized in that: Based on the signal containing the dispersive channel acquired by the oscilloscope, the frequency response of the dispersive channel is obtained. The specific steps are as follows: The dispersion value of the tunable dispersion compensation module is set, and the optical signal output by the dispersion compensation module is input into the module for photoelectric conversion, and then the output analog electrical signal is input into the oscilloscope; Perform Fourier transform on the signal collected by the oscilloscope to obtain the frequency point f i The value at The acquired frequency response is 7. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 6, characterized in that: The measured dispersion channel frequency response is obtained as follows:

8. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 7, characterized in that: The chirp parameters of the directly modulated laser optical module are fitted based on the actual dispersion channel frequency response to obtain the chirp parameter measurement results. The specific steps are as follows: Construct the frequency point f according to the dispersion channel transfer function under the small signal model i The dispersion channel frequency response at , the theoretical value is obtained Will and theoretical value The difference is taken as the error, and the minimum value of the sum of squares of the errors is found; The linewidth enhancement factor and adiabatic chirp coefficient of the directly modulated laser corresponding to the obtained minimum value; The linewidth enhancement factor and adiabatic chirp coefficient corresponding to the minimum value are taken as the chirp parameter measurement results.

9. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 8, characterized in that: The theoretical value of the dispersion channel frequency response at each frequency point is based on the dispersion channel transfer function of the directly modulated laser under small signal conditions: Among them, the first The second term represents the frequency response of the interaction between transient chirp and dispersion. is the frequency response of the interaction between adiabatic chirp and dispersion, P bias is the output optical power of the directly modulated laser under the bias voltage, θ i is the phase change caused by dispersion, λ is the operating wavelength, c is the speed of light, D·L is the dispersion value set by the tunable dispersion compensation module, α is the linewidth enhancement factor, and κ is the adiabatic chirp coefficient.

10. The parameter measurement method of the chirp parameter measurement device based on the directly modulated laser optical module according to claim 9, characterized in that: Will The difference from the theoretical value is taken as the error, and the minimum value of the sum of squares of the errors is found. The specific steps are: Will The difference from the theoretical value is taken as the error: Construct the sum of squared error function: Where N is the total number of frequency points; Set the initial values of α and κ to [α0,κ0], and use the numerical optimization algorithm to change α and κ to minimize the SSE.

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