A novel debugging method for DFB laser

Abstract

This invention discloses a novel debugging method for DFB lasers, belonging to the field of optoelectronic technology. The method uses a programmed temperature control platform to continuously change the ambient temperature, simultaneously acquiring forward voltage, backlight current, casing temperature, and real-time extinction ratio. Based on a thermal resistance network model, the active region junction temperature is inverted in real time. Combined with a pre-set physical constraint model including threshold current temperature drift and slope efficiency nonlinear decay, a constrained nonlinear optimization algorithm dynamically solves for a bias and modulation current combination that brings the extinction ratio close to the target value, and applies it to the laser in real time. After completing a full-temperature-range scan, a dynamically generated modulation parameter lookup table is generated based on the recorded data. This invention reduces the debugging time to less than one-third of traditional methods, achieves high-precision stability of the extinction ratio across the entire temperature range, and possesses adaptive capabilities to individual differences, significantly improving the mass production efficiency and consistency of optical modules.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronics technology, specifically a novel debugging method for DFB lasers. Background Technology

[0002] In high-speed optical communication systems, distributed feedback lasers (DFB lasers) serve as core light source devices, and their performance directly determines the transmission rate, signal quality, and long-term reliability of optical modules. With the continuous increase in bandwidth demands from applications such as data center interconnection, 5G fronthaul, and coherent communication, the industry has placed unprecedentedly stringent requirements on the mass production efficiency, cost control, and consistency of optical modules. Against this backdrop, the debugging process of DFB lasers after optical module packaging has become a key factor restricting overall production cycle time and yield improvement. Traditional debugging processes typically follow a two-stage strategy: initial calibration at room temperature followed by fine-tuning at high temperature. First, the extinction ratio of the laser is initially calibrated under standard room temperature conditions, and the corresponding modulation current parameters are recorded. Then, the device is placed under high-temperature aging or operating temperature conditions, and the extinction ratio drift characteristics with temperature are measured again. Based on multi-point sampling data, a mapping relationship between modulation current and temperature is fitted, ultimately generating a modulation current lookup table for driving the chip. This method effectively ensured the consistency of product performance in the early days of low-speed optical modules. Its theoretical basis lies in the fact that the threshold current, slope efficiency and chirp characteristics of DFB lasers are all significantly temperature-dependent, and the extinction ratio, as a core indicator for measuring the quality of digital modulation signals, must remain stable under different operating conditions.

[0003] However, as optical modules evolve towards higher speeds (such as 100G, 400G, and even 800G), the aforementioned commissioning paradigm reveals deep-seated structural contradictions at the principle level. Specifically, the traditional two-stage commissioning is essentially a discretized, post-compensation parameter calibration strategy, implicitly assuming that the influence of temperature on the extinction ratio can be fully characterized by linear or low-order polynomial fitting at finite temperature points. However, in actual physical processes, there is a strong dynamic coupling relationship between the carrier distribution, active region thermal effects, and electro-optic conversion nonlinearity of the DFB laser, resulting in the extinction ratio forming a high-dimensional nonlinear function space with multiple variables such as modulation current, bias current, junction temperature, and package thermal resistance. In this space, a lookup table constructed solely based on two isolated operating points at room temperature and high temperature is not only insufficient to accurately capture the non-monotonic trends within the intermediate temperature range, but also fails to reflect the dynamic response characteristics under transient thermal shock or power cycling. Consequently, to compensate for insufficient fitting accuracy, production lines are often forced to increase the number of high-temperature test points or extend the isothermal stabilization time, leading to a significant increase in the commissioning cycle of a single device. Furthermore, since testing in high-temperature environments requires a precision temperature control platform and long-term thermal equilibrium, the equipment has a high occupancy rate and high energy consumption, and is prone to introducing additional thermal stress damage risks. This is in fundamental conflict with the current lean production goals of the optical module manufacturing industry, which pursue "zero defects, high throughput, and low energy consumption".

[0004] The reason for this is that existing debugging methods treat temperature as an external disturbance variable independent of electrical parameters, neglecting the fact that in real-world operating scenarios, the laser's junction temperature is actually an endogenous state variable determined by bias current, modulation depth, package heat dissipation capacity, and ambient temperature. In other words, the stability of the extinction ratio does not simply depend on a preset temperature-current mapping table, but should be based on real-time sensing and coordinated control of the device's internal thermal-electrical-optical coupling mechanism. When the debugging process still adheres to a linear timing logic of first room temperature and then high temperature, the resulting parameter combinations are essentially the result of optimization under separate physical states, which cannot guarantee global optimization under continuous temperature variation or dynamic load conditions. Especially in mass production, minute material differences or packaging tolerances between individual devices can be significantly amplified through thermal coupling paths, causing systematic deviations in the general lookup table based on a few samples when applied across batches, leading to secondary problems such as increased bit error rate or accelerated lifetime decay in the field. Therefore, how to break through the traditional two-stage static calibration framework and construct a novel calibration method that can embed physical mechanisms, integrate multi-dimensional sensing information, and support adaptive parameter generation has become a core challenge that urgently needs to be overcome by those skilled in the art. Only in this way can we significantly reduce calibration time and equipment dependence while ensuring the stability of the extinction ratio, and ultimately achieve intelligent manufacturing of optical modules with high efficiency, low cost, and high reliability. Summary of the Invention

[0005] The purpose of this invention is to provide a novel debugging method for DFB lasers, in order to solve the problems of low debugging efficiency, insufficient parameter generalization ability and poor adaptability to dynamic conditions caused by the use of discrete temperature point calibration and static parameter fitting in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A novel commissioning method for DFB lasers includes the following steps: The DFB laser to be debugged is placed in a programmable temperature-controlled environment, and the ambient temperature is controlled to change continuously within a preset temperature range. During continuous changes in ambient temperature, multiple physical parameters of the laser are collected in real time at a preset sampling frequency. These physical parameters include at least the laser's forward voltage, backlight monitoring current, housing temperature, and real-time extinction ratio of the output light. Based on the real-time acquired shell temperature, forward voltage, and currently applied bias current, the junction temperature of the active region of the laser is inverted in real time using a pre-calibrated thermal resistance network model. Based on the currently inverted junction temperature, the currently applied bias current and modulation current, and the preset thermo-electric-optical coupled nonlinear model, the combination of bias current and modulation current required to make the extinction ratio approach the preset target value is solved in real time. The thermo-electric-optical coupled nonlinear model describes the functional relationship between the extinction ratio and the junction temperature, bias current, and modulation current, and the model includes physical constraints on the threshold current drift with temperature and the slope efficiency changes with temperature and nonlinear current. The calculated bias current and modulation current are combined and applied to the laser in real time, and the process returns to the step of real-time acquisition of physical parameters until the ambient temperature has been scanned across the entire preset temperature range. Based on the optimal bias current and modulation current data recorded at each temperature point throughout the scanning process, a modulation parameter lookup table covering the operating temperature range is generated.

[0007] According to the above technical solution, the thermal resistance network model is a first-order thermal equivalent circuit model, and its dynamic equation is:

[0008] in, The total thermal resistance of the package, For equivalent heat capacity, For the junction temperature, For the shell temperature, For power dissipation, and Pre-calibrated and cured using pulse heating method, transient thermal impedance curve measured using pulse heating method, and then fitted to obtain... and .

[0009] According to the above technical solution, the thermo-electric-optical coupling nonlinear model includes at least: Threshold current With junction temperature Arrhenius type relation:

[0010] Slope efficiency With junction temperature Arrhenius type relation:

[0011] In addition, correction terms for carrier leakage and gain saturation under high current density are applied, resulting in improved output optical power. and Represented as:

[0012]

[0013] in, For reference temperature, and Threshold current and slope efficiency at the reference point. and These are the threshold current activation energy and the slope efficiency decay energy, respectively. is the Boltzmann constant; where, For temperature-dependent slope efficiency, Both are junction temperature-dependent threshold currents, and are related by an Arrhenius-type exponential relationship. Related; Indicates the junction temperature of the device; and Empirical coefficients are used to characterize the carrier leakage and gain saturation effect at high current densities. As a temperature-sensitive factor characterizing the intensity of spontaneous emission background light, Indicates the injected current; Indicates the junction temperature is When the injection current is I, the output optical power of the laser is , and on indicates that the device is in the lasing state. Indicates the junction temperature is When the injection current is I, the off-state output optical power of the laser.

[0014] According to the above technical solution, the combination of bias current and modulation current is solved in real time using the constrained Newton-Raphson method. During the iteration process, the Jacobian matrix is ​​calculated based on the error between the target extinction ratio and the current extinction ratio, and a regularization term is introduced to suppress iterative oscillation.

[0015] According to the above technical solution, in the process of solving and applying the current combination, dual boundary constraints are also implemented: electrical safety boundary, ensuring that the bias current is not lower than 95% of the threshold current at the current junction temperature and does not exceed 85% of the maximum rated operating current; thermal stability boundary, monitoring the junction temperature change rate, if the junction temperature change rate at multiple consecutive sampling points exceeds the preset threshold, the current adjustment is paused until the thermal field stabilizes again.

[0016] According to the above technical solution, after completing the forward temperature scan from low temperature to high temperature, it also includes performing a reverse temperature scan from high temperature to low temperature at the same or lower rate, and reusing the modulation parameters generated by the forward scan as the initial value during the reverse scan; comparing the optimal current combination obtained by the forward and reverse scans at the same junction temperature, if the deviation exceeds the allowable range, a second fine-tuning scan is triggered until the bidirectional consistency meets the preset convergence criterion.

[0017] According to the above technical solution, when the current combination obtained by the solution is applied to the laser, the actual output bias current and modulation current waveform of the driver chip are monitored in real time through the high-speed feedback channel, and the measured value is cross-verified with the command value. If there is a systematic deviation, a feedforward compensation term is introduced in subsequent iterations to correct the command value.

[0018] According to the above technical solution, the modulation parameter lookup table is generated as follows: spline interpolation is performed on the recorded full-temperature data points to obtain a continuous function. Then, the node intervals are dynamically divided according to the sensitivity of the extinction ratio to the junction temperature. The nodes are densified in the temperature range where the sensitivity is higher than the preset threshold, and the nodes are sparse in the temperature range where the sensitivity is lower. Finally, a piecewise linear lookup table containing the node temperature and the corresponding bias current and modulation current is generated.

[0019] According to the above technical solution, the rate of continuous change of ambient temperature is controlled between 0.5 degrees Celsius and 2 degrees Celsius per minute.

[0020] According to the above technical solution, the sampling frequency of the real-time extinction ratio is ≥10Hz.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention achieves high-precision, high-efficiency, and high-robust calibration of DFB laser modulation parameters by constructing a novel debugging framework based on dynamic junction temperature inversion, with physical constraint nonlinear mapping as the core, and continuous temperature-variable collaborative optimization as the execution path. This method transforms the debugging process from discrete point fitting to continuous trajectory tracking, from external temperature-driven to internal thermal state-driven, and from static parameter loading to dynamic closed-loop control. Thus, while ensuring the stability of the extinction ratio across the entire temperature range, it significantly shortens the debugging time of a single device to less than one-third of that of traditional methods, while reducing reliance on high-precision isothermal platforms. This provides key technical support for the large-scale intelligent manufacturing of high-speed optical modules. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the system architecture and process of a novel debugging method for DFB lasers according to the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 This invention provides a novel debugging method for DFB lasers, aiming to solve the problems of low debugging efficiency, insufficient parameter generalization ability, and poor adaptability to dynamic operating conditions caused by the use of discrete temperature point calibration and static parameter fitting in existing technologies. To achieve the above-mentioned objective, this invention constructs a nonlinear adaptive debugging architecture based on a real-time sensing and closed-loop control mechanism of thermo-electric-optical coupling state. By synchronously acquiring multi-dimensional physical parameters during the post-packaging testing phase, and dynamically generating a combination of modulation current and bias current based on an embedded high-dimensional nonlinear mapping model, the extinction ratio stability optimization across the entire temperature range is achieved during a single continuous temperature change.

[0025] The core of the aforementioned debugging method lies in abandoning the traditional two-stage process of initial adjustment at room temperature and fine adjustment at high temperature, and instead implementing a continuous and coordinated debugging strategy with the internal thermodynamic state of the device as the core driving variable. Specifically, after the optical module completes its hermetically sealed packaging and is connected to the testing system, an initial bias current and modulation current combination are first applied to the DFB laser to keep it in the subthreshold or near-threshold operating range. Then, a programmed temperature control unit is activated, continuously scanning the ambient temperature from the low-temperature end to the high-temperature end at a preset slope, with the scanning rate controlled between 0.5 and 2 degrees Celsius per minute to ensure the heat conduction process is in a quasi-steady state. During this continuous temperature change process, the following four key physical parameters are simultaneously collected: the first is the laser's forward voltage signal, which is conditioned by a low-noise differential amplifier and then input to a high-precision analog-to-digital converter; the second is the output current of the backlight monitoring photodiode, used to calculate the output optical power in real time; the third is the surface temperature of the package housing, measured by a platinum resistance temperature sensor attached to the TO-can metal base; and the fourth is the real-time extinction ratio value output by a high-speed eye diagram analyzer, with a sampling frequency of no less than ten times per second.

[0026] The four types of physical parameters are fed into a central coordinating controller in real time. This controller embeds a thermal state analysis engine and a thermo-electrical-optical coupling modeling unit. The thermal state analysis engine, based on the temporal variation characteristics of the forward voltage and the housing temperature, inverts the dynamic evolution trajectory of the junction temperature in the active region of the DFB laser. This inversion process relies on a pre-calibrated package thermal resistance network model, which expresses the relationship between housing temperature, dissipated power, and junction temperature as a numerical solution of a first-order heat conduction differential equation. The dissipated power is determined by the product of the bias current and the forward voltage, while the heat capacity and thermal conductivity parameters are solidified through pulse heating experiments on small batches of samples in the early stages, ensuring that no recalibration is required during mass production.

[0027] The thermo-electric-optical coupling modeling unit receives the junction temperature sequence, current bias current value, modulation current amplitude, and measured extinction ratio data from the thermal state analysis engine, and constructs a nonlinear regression mapping with four-dimensional input and one-dimensional output. This mapping does not employ traditional polynomial fitting, but rather a piecewise smooth function family based on physical constraints, whose mathematical structure is uniquely determined by the following composite relation:

[0028] in, Indicates the extinction ratio. For the active region junction temperature, For bias current, To modulate the current amplitude, and These represent the average output optical power corresponding to logic "1" and "0", respectively.

[0029] Furthermore, and It is modeled as a composite function containing a threshold current temperature drift term and a slope efficiency nonlinear decay term:

[0030]

[0031] in, For temperature-dependent slope efficiency, Both are junction temperature-dependent threshold currents, and are related by an Arrhenius-type exponential relationship. Related, Indicates the junction temperature of the device; and Empirical coefficients are used to characterize the carrier leakage and gain saturation effect at high current densities. This is a temperature-sensitive factor characterizing the intensity of spontaneous emission background light. All the above function parameters were validated and solidified through the initial process window before the commissioning process began; only the following parameters are retained. and As an adjustable degree of freedom, Indicates the junction temperature is Injection current is At this time, the output optical power of the laser is 'on', indicating that the device is in the lasing state. Indicates the junction temperature is Injection current is At that time, the output optical power of the laser in the off state.

[0032] During continuous temperature scanning, the central coordinating controller performs parameter optimization iterations at fixed time steps. Within each iteration cycle, the controller first optimizes the parameters based on the current junction temperature. Extinction ratio to target (Typically set to a fixed value within the range of 8.2dB to 10.5dB), the solution satisfies The current combination. The solution process uses the constrained Newton-Raphson method, and its Jacobian matrix is ​​obtained by the above composite function pair. and The partial derivatives are used to construct the equation, and a regularization term is introduced to suppress high-frequency oscillations. The obtained equation is... and It is immediately written to the temporary register of the driver chip and takes effect in the next sampling cycle.

[0033] To ensure the physical feasibility of parameter adjustment and device safety, the debugging method further incorporates a dual boundary constraint mechanism. The first boundary is the electrical safety boundary, which stipulates that the bias current must not be lower than 95% of the threshold current at the current junction temperature, nor exceed 85% of the maximum rated operating current. The second boundary is the thermal stability boundary, which requires that the absolute value of the junction temperature change rate within any three consecutive sampling points does not exceed 0.3 degrees Celsius per second. If an exceedance is detected, the current adjustment is automatically paused and the dwell time of the current temperature plateau is extended until the thermal field stabilizes again.

[0034] Once the ambient temperature has completed a full scan from the low-temperature end to the high-temperature end, the central coordinating controller will record the entire process. The dataset is interpolated using spline interpolation to generate a continuous modulation parameter curve covering the entire operating temperature range. This curve is then encoded into a piecewise linear lookup table recognizable by the driver chip, with the node spacing dynamically adjusted based on the temperature sensitivity of the extinction ratio: in temperature regions where the sensitivity is higher than a preset threshold, the node density is automatically increased; in flat regions, it is moderately sparsed to balance storage overhead and control accuracy. Finally, this lookup table is burned into the optical module's non-volatile memory as the basis for modulation parameters during subsequent actual operation.

[0035] In a preferred embodiment of the present invention, the programmed temperature control unit employs a bidirectional temperature scanning strategy. After completing the initial forward scan from low to high temperature, a reverse scan from high to low temperature is immediately executed, reusing the initial parameter curve obtained during the reverse scan as the starting point. By comparing the differences in the optimal current combinations corresponding to the same junction temperature point in both forward and reverse scans, asymmetric deviations introduced by thermal hysteresis or package stress relaxation can be effectively identified and compensated. If the deviation between forward and reverse parameters exceeds the allowable tolerance, a secondary fine-tuning cycle is triggered until bidirectional consistency meets the preset convergence criterion.

[0036] Furthermore, a high-speed feedback channel is established between the central co-controller and the driver chip. This channel not only transmits modulation parameters but also sends back the actual bias current and modulation current waveforms monitored internally by the driver chip in real time. By cross-validating the returned waveforms with the command values, execution errors caused by loose solder joints, parasitic inductance of leads, or nonlinearity of the driver circuit can be detected in a timely manner, and feedforward compensation terms can be introduced in subsequent iterations to correct them.

[0037] Another key feature of the aforementioned debugging method lies in its adaptability to individual differences. Since all physical model parameters are fixed during the early process verification stage, and the debugging process only adjusts two degrees of freedom, inherent variations such as differences in material properties between different devices, epitaxial layer thickness fluctuations, or cavity surface reflectivity deviations can be automatically incorporated into the final parameter curve through continuous optimization, without relying on batch averages or typical value assumptions. This fundamentally avoids the performance degradation problem caused by traditional lookup tables neglecting individual thermo-electrical characteristic differences when applied across batches.

[0038] Example 2 This embodiment provides a novel debugging method for DFB lasers, the specific implementation of which is described below. This method is implemented after the optical module has completed hermetically sealed packaging and before entering final factory testing. It is applicable to distributed feedback (DFB) semiconductor lasers based on TO-can packaging structures, and is particularly suitable for high-speed direct-modulation optical modules with speeds of 25Gbps and above. The entire debugging process is executed by an integrated testing system, which includes a programmable temperature control unit, a multi-channel physical parameter acquisition module, a central coordinating controller, and a laser driver chip that communicates with it.

[0039] Before initiating the commissioning process, the hermetically sealed DFB laser module is first installed in the test fixture, ensuring a reliable connection between its electrical pins and the drive circuit, while also guaranteeing unobstructed heat conduction paths. The test fixture integrates a programmable temperature control platform at its bottom, covering a temperature range of -40℃ to +95℃ with a control accuracy better than ±0.1℃. A Pt100 platinum resistance temperature sensor is attached to the surface of the laser's TO-can metal base using high thermal conductivity silver paste for real-time monitoring of the housing temperature. The sensor signal, after being excited by a low-noise constant current source, is digitized by a 24-bit Δ-Σ analog-to-digital converter at a sampling rate of 20 times per second.

[0040] At the same time, the forward voltage of the laser A differential probe is connected to a low-noise instrumentation amplifier with a gain set to 1 and a common-mode rejection ratio (CMRR) of at least 100 dB. The output signal is then fed into a high-precision analog-to-digital converter (ADC). The output current of the monitor photodiode (MPD) is converted into a voltage signal by a transimpedance amplifier. The transimpedance value is preset to a fixed value based on the typical responsivity of the device and subsequently corrected by a calibration coefficient to obtain an electrical signal proportional to the output optical power. Furthermore, a high-speed eye diagram analyzer receives the laser output optical signal via a coupled fiber and calculates the extinction ratio in real time. Its internal clock recovery circuit is locked to the data rate, with a sampling frequency ≥10Hz, ensuring that the dynamic changes in the extinction ratio can be captured during continuous temperature changes.

[0041] The above four types of physical parameters: forward voltage MPD current, casing temperature Real-time extinction ratio The data is synchronously fed into the central co-controller. This controller is a heterogeneous computing platform based on FPGA and embedded ARM core, where the FPGA is responsible for high-speed data stream processing and real-time control instruction generation, and the ARM core runs advanced algorithm logic. The controller internally incorporates a thermal resistance network model, a thermal-electrical-optical coupling mapping function, and a parameter optimization engine.

[0042] Package thermal resistance network model is used to obtain thermal resistance from the case temperature. With dissipated power Inversion of active region junction temperature The power dissipation is determined by the bias current collected in real time. With forward voltage The product is determined, that is The thermal resistance network is modeled using a first-order thermal equivalent circuit, and its dynamic equation is:

[0043] in, The total thermal resistance of the package, This refers to the equivalent heat capacity. These two parameters were calibrated during the early process verification phase using a pulsed heating method: a short, high-power pulse was applied to the laser (duration less than 100 microseconds to avoid heat diffusion to the casing), and the values ​​were recorded. Transient response over time, utilizing The linear relationship with junction temperature leads to the thermal time constant. Then, by combining steady-state temperature rise data, decoupling is achieved. and Once calibration is complete, the model parameters are embedded in the controller firmware and will not be updated during the mass production debugging phase.

[0044] The thermal state analysis engine, based on the aforementioned heat conduction differential equation, employs a fourth-order Runge-Kutta method to numerically integrate the junction temperature. The initial junction temperature is set to the ambient starting temperature, and the time step is synchronized with the data acquisition cycle, typically 100 milliseconds. The resulting... The sequence serves as the core input for subsequent coupling modeling.

[0045] The thermo-electric-optical coupling modeling unit receives the current junction temperature of the device. Current bias current Current modulation current amplitude and measured extinction ratio A nonlinear mapping is constructed based on a preset family of physical constraint functions. The mathematical expression of this mapping is as described in the invention description, wherein the threshold current... With slope efficiency All relationships are of the Arrhenius type:

[0046] in, This is a reference temperature (usually 298K). and Threshold current and slope efficiency at the reference point. and These are the threshold current activation energy and the slope efficiency decay energy, respectively. , where represents the Boltzmann constant. These parameters were obtained through multi-temperature LI curve fitting during the initial process window verification, and were normalized for specific epitaxial structures and cavity lengths before curing.

[0047] empirical coefficient , and Similarly, calibration is performed in the early stages. and The typical value range was determined by fitting the nonlinear inflection point of the LI curve under high current density. mW / mA², mW / mA²; The relationship between spontaneous emission power and junction temperature is obtained by fitting the data in the subthreshold region, and its form is: ,in It is a spontaneous emission activation energy.

[0048] During continuous temperature scanning, the programmed temperature control unit maintains a constant slope. From the low temperature end (e.g., -40℃) towards the high temperature end (e.g., +95℃) Temperature increase. Slope The rate was set at 1.0°C per minute. This rate ensures that the heat conduction process is in a quasi-steady state, meaning the junction temperature change rate is much smaller than the reciprocal of the thermal time constant, thus avoiding significant thermal inertia distortion. Throughout the scan, the central co-controller performs parameter optimization iterations at 100-millisecond intervals.

[0049] In each iteration cycle, the controller first reads the current junction temperature. And set the target extinction ratio This target value is preset according to application standards, typically 9.0 dB in 25G-LR optical modules, with an allowable tolerance of ±0.3 dB. The controller then solves the nonlinear equations:

[0050] The equation has two degrees of freedom, but in practical engineering, the modulation current amplitude is usually fixed. With bias current The proportional relationship can be used, or auxiliary constraints (such as maintaining a constant average optical power) can be introduced to transform the problem into a single-variable solution. However, this invention preferably retains two degrees of freedom to achieve better global adaptability. The solution employs a constrained Newton-Raphson method, with the following iterative formula:

[0051] in, Indicates the damping coefficient. and This represents the iterative current vector, where the subscripts b and m represent different channels of the laser. Indicates the target error; Representing the error function

[0052] in, The Jacobian matrix has the following elements: in, Represents the elements of the Jacobian matrix. This represents the elements of the Jacobian matrix. Since ER is a scalar, in practice, the error term is expanded into a two-dimensional vector (e.g., by introducing an average optical power constraint), or a pseudo-inverse method is used. Regularization parameter. It is used to suppress oscillations caused by local nonconvexity of the model, and its value is adaptively adjusted according to the historical convergence speed.

[0053] obtained and The data is written to the temporary register of the driver chip. This driver chip is an application-specific integrated circuit (ASIC) that supports dual-channel independent current control, with a bias current resolution better than 0.1mA and a modulation current rise / fall time of less than 30ps. The write operation is completed via I²C or SPI bus, with a latency controlled within 1 millisecond to ensure that the parameters take effect in the next sampling cycle.

[0054] To ensure device safety, a dual boundary constraint mechanism operates simultaneously. Electrical safety boundaries are defined as follows: ,in This represents the device's maximum rated operating current (e.g., 100mA). If the optimization result exceeds this range, the controller will truncate to the boundary value and record the out-of-bounds event. The thermal stability boundary monitors the junction temperature change rate. If three consecutive sampling points exceed 0.3℃ / s, parameter updates are paused, the current current combination is maintained, and the dwell time of the current temperature plateau is extended until... Optimization can only be restored after a delay of more than 500 milliseconds.

[0055] When the ambient temperature completes its transition from to After the forward scan, the controller records the entire process. Perform cubic spline interpolation on the dataset to generate a continuous function. and Subsequently, based on the sensitivity of the extinction ratio to the junction temperature... The lookup table nodes are dynamically partitioned. Sensitivity is calculated using the central difference method.

[0056] in, Indicates junction temperature Extinction ratio sensitivity at the location; Indicates the sampling point number; Indicates the first Junction temperature at each sampling point; This represents the extinction ratio at the (k+1)th sampling point; This represents the extinction ratio at the (k-1)th sampling point; This represents the extinction ratio at the (k+1)th sampling point; This represents the extinction ratio at the (k-1)th sampling point.

[0057] like ,in Indicating a sensitivity threshold (e.g., 0.1 dB / ℃), the minimum spacing between encrypted nodes in this temperature range can reach 1℃; if Then the node spacing can be increased to 5°. The final piecewise linear lookup table contains 10 to 30 nodes, each storing... , , Triplet.

[0058] In a preferred embodiment of the present invention, the system further performs a reverse temperature scan. After the forward scan is completed, the temperature control unit immediately switches from the forward scan at the same slope... Cool down to During this process, the initial modulation parameters are interpolated using a lookup table obtained from the forward scan. The controller synchronously records the optimal current combination under the reverse path. After the scan is completed, calculate the deviation of the forward and reverse parameters at the same junction temperature point:

[0059]

[0060] in, Indicates junction temperature The bias current under forward bias; Indicates junction temperature The bias current when reverse biased; Indicates junction temperature The modulation current under forward bias; Indicates junction temperature The modulation current under forward bias; Indicates junction temperature The absolute value of the difference between the forward and reverse bias currents under DC bias characterizes the current asymmetry under DC bias. Indicates junction temperature The absolute value of the difference between the forward and reverse directions of the modulation current characterizes the current asymmetry under AC drive.

[0061] If in any temperature range or If significant thermal hysteresis or stress relaxation effect is detected, a secondary fine-tuning cycle is triggered, in which... Indicates the degree of bias current asymmetry; This indicates the degree of AC modulation asymmetry. The second cycle uses a smaller temperature change rate (e.g., 0.5℃ / min) and sets a temperature plateau in the high-sensitivity region, repeating the above optimization process until the bidirectional deviation meets the convergence criterion.

[0062] Furthermore, a high-speed feedback channel is established between the central co-controller and the driver chip. This channel not only sends out modulation parameters but also transmits back the actual bias current and modulation current waveforms monitored by the driver chip's internal ADC in real time. Cross-correlation analysis is performed between the transmitted data and the command values. If a systematic deviation is detected (such as current attenuation due to loose solder joints or edge distortion caused by lead inductance), a feedforward compensation term is introduced in subsequent iterations. For example, if the actual measurement... Then the instruction value for the next cycle will be corrected to, ,in This indicates the actual bias current monitored by the driver chip. This indicates the command bias current.

[0063] To verify the technical effects of the present invention, the following embodiments and comparative experiments were conducted.

[0064] In one specific embodiment, 50 2.5GDFB laser modules from the same batch were selected and debugged using the method of this invention. The temperature control slope was 1.0℃ / min, the target extinction ratio was 9.0dB, and the forward scan range was -40℃ to +95℃, followed by a reverse scan. All model parameters were derived from previous process verification. After debugging, the generated lookup table was burned into the module's EEPROM, and verification tests were conducted at five temperature points: -40℃, 0℃, 25℃, 70℃, and 95℃, recording the actual extinction ratio.

[0065] In the comparative experiment, the traditional two-stage debugging method was adopted: first, adjustments were made at 25℃. and The extinction ratio was set to 9.0 dB, and the bias current was then fine-tuned at 85 °C to compensate for threshold drift, while the modulation current remained constant. This method relies on a linear temperature compensation coefficient fitted at discrete points and does not consider nonlinear effects.

[0066] The test results are shown in the table below:

[0067] Data shows that the extinction ratio of the embodiment remains stable within the range of 9.0dB±0.1dB across the entire temperature range, with a significantly lower standard deviation than the comparative example. Particularly at extreme high and low temperatures, the comparative example suffers from a severely deviated extinction ratio due to neglecting the nonlinear decay of slope efficiency and the high current leakage effect. Furthermore, the average setup time for a single device in the embodiment is 8.5 minutes, while the comparative example requires 12.3 minutes (including two isothermal waiting periods), representing an efficiency improvement of approximately 31%.

[0068] Furthermore, in another batch-wise test, three different epitaxial growth batches of DFB chips were selected, with 20 chips in each batch, totaling 60 chips. After debugging using the method of this invention, the extinction ratio distribution overlap of each batch at 95℃ reached 92%, while the comparative sample was only 68%, proving that this invention has a strong adaptive capability to individual differences.

[0069] In summary, this invention achieves high-precision, high-efficiency, and high-robust calibration of DFB laser modulation parameters by constructing a continuous collaborative debugging architecture based on dynamic junction temperature inversion. This method fully discloses the complete technical path from physical parameter acquisition, thermal state analysis, nonlinear mapping modeling to parameter optimization and storage. Those skilled in the art can reproduce all the technical effects based on the above description.

[0070] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0071] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel debugging method for DFB lasers, characterized in that: Includes the following steps: The DFB laser to be debugged is placed in a programmable temperature-controlled environment, and the ambient temperature is controlled to change continuously within a preset temperature range. During continuous changes in ambient temperature, multiple physical parameters of the laser are collected in real time at a preset sampling frequency. These physical parameters include at least the laser's forward voltage, backlight monitoring current, housing temperature, and real-time extinction ratio of the output light. Based on the real-time acquired shell temperature, forward voltage, and currently applied bias current, the junction temperature of the active region of the laser is inverted in real time using a pre-calibrated thermal resistance network model. Based on the current inverted junction temperature, the currently applied bias current and modulation current, and the preset thermo-electric-optical coupling nonlinear model, the combination of bias current and modulation current required to make the extinction ratio approach the preset target value is solved in real time. The thermo-electric-optical coupled nonlinear model describes the functional relationship between the extinction ratio and junction temperature, bias current, and modulation current. The model also includes physical constraints on the threshold current drift with temperature and the slope efficiency variation with temperature and nonlinear current. The calculated bias current and modulation current are combined and applied to the laser in real time, and the process returns to the step of real-time acquisition of physical parameters until the ambient temperature has been scanned across the entire preset temperature range. Based on the optimal bias current and modulation current data recorded at each temperature point throughout the scanning process, a modulation parameter lookup table covering the operating temperature range is generated.

2. The novel debugging method for DFB lasers according to claim 1, characterized in that: The thermal resistance network model is a first-order thermal equivalent circuit model, and its dynamic equations are as follows: in, The total thermal resistance of the package, For equivalent heat capacity, For the junction temperature, For the shell temperature, For power dissipation, and Pre-calibrated and cured using pulse heating method, transient thermal impedance curve measured using pulse heating method, and then fitted to obtain... and .

3. The novel debugging method for DFB lasers according to claim 1, characterized in that: Thermo-electric-optical coupled nonlinear models should include at least: Threshold current With junction temperature Arrhenius type relation: ， Slope efficiency With junction temperature Arrhenius type relation: ， In addition, correction terms for carrier leakage and gain saturation under high current density are applied, resulting in improved output optical power. and Represented as: in, For reference temperature, and Threshold current and slope efficiency at the reference point, and These are the threshold current activation energy and the slope efficiency decay energy, respectively. is the Boltzmann constant; where, For temperature-dependent slope efficiency, Both are junction temperature-dependent threshold currents, and are related by an Arrhenius-type exponential relationship. Related; Indicates the junction temperature of the device; and Empirical coefficients are used to characterize the carrier leakage and gain saturation effects at high current densities. As a temperature-sensitive factor characterizing the intensity of spontaneous emission background light, Indicates the injected current; Indicates the junction temperature is Injection current is At this time, the output optical power of the laser is 'on', indicating that the device is in the lasing state. Indicates the junction temperature is Injection current is At that time, the output optical power of the laser in the off state.

4. A novel debugging method for DFB lasers according to claim 1, characterized in that: The constrained Newton-Raphson method is used to solve the combination of bias current and modulation current in real time. During the iteration process, the Jacobian matrix is ​​calculated based on the error between the target extinction ratio and the current extinction ratio, and a regularization term is introduced to suppress iterative oscillation.

5. A novel debugging method for a DFB laser according to claim 1, characterized in that: During the process of solving and applying current combinations, dual boundary constraints are also implemented: electrical safety boundary, ensuring that the bias current is not lower than 95% of the threshold current at the current junction temperature and does not exceed 85% of the maximum rated operating current; thermal stability boundary, monitoring the junction temperature change rate, if the junction temperature change rate at multiple consecutive sampling points exceeds the preset threshold, the current adjustment is paused until the thermal field stabilizes again.

6. A novel debugging method for a DFB laser according to claim 1, characterized in that: After completing the forward temperature scan from low temperature to high temperature, the process also includes performing a reverse temperature scan from high temperature to low temperature at the same or lower rate, and reusing the modulation parameters generated by the forward scan as initial values ​​during the reverse scan. If the deviation exceeds the allowable range when comparing the optimal current combination obtained by the forward and reverse scans at the same junction temperature, a second fine-tuning scan is triggered until the bidirectional consistency meets the preset convergence criterion.

7. A novel debugging method for a DFB laser according to claim 1, characterized in that: When the current combination obtained from the solution is applied to the laser, the actual output bias current and modulation current waveforms of the driver chip are monitored in real time through a high-speed feedback channel. The measured values ​​are cross-validated with the command values. If there is a systematic deviation, a feedforward compensation term is introduced in subsequent iterations to correct the command values.

8. A novel debugging method for a DFB laser according to claim 1, characterized in that: The modulation parameter lookup table is generated as follows: spline interpolation is performed on the recorded full-temperature data points to obtain a continuous function. Then, the node intervals are dynamically divided according to the sensitivity of the extinction ratio to the junction temperature. The nodes are densified in the temperature range where the sensitivity is higher than the preset threshold, and the nodes are sparse in the temperature range where the sensitivity is lower. Finally, a piecewise linear lookup table containing the node temperature and the corresponding bias current and modulation current is generated.

9. A novel debugging method for a DFB laser according to claim 1, characterized in that: The rate of continuous change in ambient temperature is controlled between 0.5 degrees Celsius and 2 degrees Celsius per minute.

10. A novel debugging method for a DFB laser according to claim 1, characterized in that: The sampling frequency for the real-time extinction ratio is ≥10Hz.

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