SOA segment modeling and simulation design method based on space-time staggered half-step partitioning

Abstract

The application discloses a SOA segmentation modeling simulation design method based on space-time staggered half-step segmentation, and relates to the fields of semiconductor laser amplifiers and semiconductor lasers.The method comprises the following steps: in the light amplification direction of an SOA active region, the SOA active region is gradually segmented according to the space-time staggered half-step segmentation of the carrier concentration and the electric field component of the optical signal, and a SOA segmentation model based on space-time staggered half-step segmentation is constructed; the constructed SOA segmentation model based on space-time staggered half-step segmentation is used to simulate a plurality of parameter groups to be simulated, and the simulation results of the SOA segmentation model based on space-time staggered half-step segmentation for each parameter group are obtained; and data analysis is performed on the simulation results of each parameter group, and one or more parameter groups with performance meeting the requirements are determined as the simulation optimization results of the SOA device.The first-order error term is eliminated, the model and method are improved to the second order, and therefore the simulation precision and the calculation efficiency are improved by orders of magnitude.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor laser amplifier, and particularly relates to a segmented modeling simulation design method of SOA (Semiconductor Optical Amplifier) based on space-time upper staggered half-step dissection. BACKGROUND

[0002] It is pointed out in the paper "Semiconductor optical amplifiers:recent advances and applications", the paper "SOA for future PONs", and the paper "Linear and nonlinear semiconductor optical amplifiers" that wideband and short-haul fiber communication including data center optical interconnection and fiber access network widely use SOA and semiconductor lasers based on SOA.

[0003] According to different application categories of SOA in optical communication and optical sensing, a series of numerical calculation and simulation models are generated, for example, the paper "Wideband semiconductor optical amplifier steady-state numerical model" proposes a frequency domain steady-state model, which is widely used for SOA basic modeling and calculation, the paper "Detailed dynamic model for semiconductor optical amplifiers and their crosstalk and intermodulation distortion" and the paper "Modeling and measurement of longitudinal gain dynamics in saturated semiconductor optical amplifiers of different length" propose detailed time domain models, which are used to simulate and analyze time domain nonlinear effects such as signal crosstalk and gain saturation, and are extended to a wideband model in the paper "Wideband dynamic numerical model of a tapered buried ridge stripe semiconductor optical amplifier gate".

[0004] Frequency-domain based models can give fast simulation results of the power and noise evolution of multi-channel signals along the longitudinal direction of SOA, but cannot provide time-domain evolution information of the signal amplitude and phase. Since 2010, commercial coherent optical communication has been developed. Compared with non-coherent optical communication, it improves the receiving sensitivity and reduces the channel spacing between wavelength division multiplexing channels by simultaneously transmitting amplitude and phase information. Coherent optical communication usually uses high-order modulation formats such as 16-QAM (Quadrature Amplitude Modulation) to further improve the communication transmission rate. Time-domain based SOA models have the ability to precisely simulate the time-domain evolution of amplitude and phase, and have become a necessary tool for the design of coherent optical communication related devices and system optimization.

[0005] High-order modulation formats such as N-QAM can modulate M = log2 N bits of information into a waveform. For M input waveforms with different amplitudes and phases, when the SOA is in a linear state, the amplitudes and phases of the M SOA output waveforms are relatively unchanged, and the performance of the system is only affected by ASE (Amplified Spontaneous Emission) noise. However, at this time, the SOA only works in the small signal amplification interval, the signal-to-noise ratio is small, and the system performance is poor. When the SOA is in a deep gain saturation state, the signal-to-noise ratio is large, but at this time the amplitude and phase of the SOA output waveform are greatly distorted, which greatly reduces the system performance. By using a time-domain based SOA model, the time-domain evolution of the waveform signal including amplitude and phase of the SOA in the gain saturation state can be accurately simulated, the balance point of signal-to-noise ratio and waveform distortion can be found, and the system performance can be optimized.

[0006] Because SOA and SOA-based semiconductor lasers have multiple geometric, physical, and signal parameters, and experience multiple physical processes such as current injection, carrier transition, and depletion, there are many design parameters for modeling. The joint optimization of these parameters is a major challenge in SOA modeling design: for example, when there are 3 parameters to be jointly optimized, each parameter takes 10 values, then the simulation calculation required by traversing all combinations reaches 10 3 , that is, 1000 times, which is a great demand for computing power and computing time.

[0007] Different from the SOA model of frequency domain steady state, the simulation calculation time of the time domain large signal SOA model is longer, which seriously restricts the device design efficiency of SOA and the system optimization effect. In view of the above phenomenon, a new modeling simulation design method for the calculation efficiency of the large signal SOA time domain model is needed to realize the high-speed traversal of the parameter space, which is of great significance not only for SOA and semiconductor laser based on SOA, but also for the modeling simulation and optimization design of amplifiers and lasers in other fields such as semiconductor or non-semiconductor based amplifiers and lasers. SUMMARY

[0008] The application provides a SOA segmented modeling simulation design method based on space-time staggered half-step subdivision, which overcomes the problems of low calculation efficiency of large signal time domain simulation and long time consumption of optimization design of SOA, semiconductor laser based on SOA and other devices.

[0009] The SOA segmented modeling simulation design method based on space-time staggered half-step subdivision of the application comprises: in the light amplification direction of the SOA active region, the SOA active region is gradually segmented according to the space-time staggered half-step subdivision of the carrier concentration and the electric field component of the optical signal, and a SOA segmented model based on space-time staggered half-step subdivision is constructed; the constructed SOA segmented model based on space-time staggered half-step subdivision is used to simulate a plurality of parameter groups to be simulated respectively, and the simulation results of the SOA segmented model based on space-time staggered half-step subdivision for each parameter group are obtained; the simulation results of each parameter group are analyzed to determine one or more parameter groups meeting the performance requirements as the simulation optimization results of the SOA device.

[0010] Preferably, the method further comprises: obtaining parameter data required by the SOA segmented model based on space-time staggered half-step subdivision, so as to directly use the parameter data for the constructed SOA segmented model based on space-time staggered half-step subdivision.

[0011] Preferably, the parameter data comprises band gap parameter data, optical waveguide parameter data, confinement factor and electro-optical gain parameter data. The band gap parameter data comprises carrier concentration at equilibrium, and the acquisition method comprises: in the constructed SOA segmented model based on space-time staggered half-step subdivision, simulating with zero input optical signal as input signal, and taking the value of the model at equilibrium as the carrier concentration at equilibrium. The electro-optical gain parameter data comprises group velocity of the signal, and the acquisition method comprises one of the following methods: obtaining from known literature or database; extracting through laboratory measurement.

[0012] Preferably, the SOA active region is gradually segmented in the light amplification direction of the SOA active region according to the staggered half-step profile of the carrier concentration and the electric field component of the optical signal in space-time, and the SOA segmented model based on the staggered half-step profile in space-time is constructed by: taking the carrier concentration at equilibrium as the initial value of the carrier concentration of the semiconductor laser amplifier optical waveguide; segmenting the semiconductor laser amplifier optical waveguide device according to the direction of optical signal transmission to obtain a plurality of semiconductor laser amplifier optical waveguides with a length of Δz; sampling the input optical signal according to a sampling time interval Δt to obtain M sampling points, wherein Δz = v g Δt, v g is the group velocity of the optical signal propagating in the semiconductor laser amplifier optical waveguide; and the iterative equation of the calculation point of the optical signal is determined according to the differential equation satisfied by the SOA physical model, wherein the carrier concentration N[z, t] on the corresponding segment of the semiconductor laser amplifier optical waveguide contained in the iterative equation of the calculation point of the optical signal is the carrier concentration on the segment of the semiconductor laser amplifier optical waveguide after Δt / 2.

[0013] Preferably, the SOA active region is gradually segmented in the light amplification direction of the SOA active region according to the staggered half-step profile of the carrier concentration and the electric field component of the optical signal in space-time, and the SOA segmented model based on the staggered half-step profile in space-time is constructed by: taking the carrier concentration at equilibrium as the initial value of the carrier concentration of the semiconductor laser amplifier optical waveguide; segmenting the semiconductor laser amplifier optical waveguide device according to the direction of optical signal transmission to obtain a plurality of semiconductor laser amplifier optical waveguides with a length of Δz; sampling the input optical signal according to a sampling time interval Δt to obtain M sampling points, wherein Δz = v

[0014] Preferably, the plurality of parameter groups to be simulated are obtained by: selecting parameters that can be controlled and optimized in design from the parameters of the semiconductor or other electro-optical gain material obtained in advance as the parameters to be simulated; and generating a plurality of parameter groups to be simulated according to the parameters to be simulated and their ranges, wherein each parameter group to be simulated includes all parameters to be simulated and parameter values within the ranges.

[0015] Preferably, the simulation results of each parameter group are analyzed to determine one or more parameter groups meeting the performance requirements as the simulation optimization results of the SOA device, including: calculating the error vector magnitude of the simulation results of each parameter group; and selecting and saving one or more parameter groups with error vector magnitudes meeting the requirements from the plurality of parameter groups as the simulation optimization results of the SOA device.

[0016] Preferably, the method further comprises: sequentially assigning the one or more parameter groups meeting the error vector magnitude requirement to the SOA contained in the system model, and simulating the system model to obtain system simulation results of the system model for each parameter group meeting the error vector magnitude requirement; calculating the bit error rate of the system simulation results of each parameter group, and selecting one or more parameter groups meeting the bit error rate requirement as the simulation optimization result of the system model.

[0017] The SOA segmentation model based on the space-time staggered half-step partitioning can eliminate the first-order error term of the simple segmentation model of the first order, improve the model and method to the second order, thereby improving the simulation accuracy and calculation efficiency by orders of magnitude, and reducing the time consumption of the optimization design. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flowchart of the SOA segmentation modeling simulation design method based on the space-time staggered half-step partitioning;

[0019] Figure 2 is a structural schematic diagram of a common block-type semiconductor laser amplifier;

[0020] Figure 3 is a SOA segmentation schematic diagram and a signal sampling schematic diagram;

[0021] Figure 4 is a simulation algorithm schematic diagram of the SOA;

[0022] Figure 5 is a schematic diagram of a system instance of system optimization;

[0023] Figure 6 is a flowchart of the semiconductor laser amplifier optimized by the system;

[0024] Figure 7 is a comparison diagram of the output waveforms of two partitioning modes and the true solution;

[0025] Figure 8 is a comparison of the global errors of the results of the two partitioning modes. DETAILED DESCRIPTION

[0026] The specific implementation of the present application is described in detail below, and it is necessary to point out here that the following implementation is only for further description of the present application and cannot be understood as a limitation on the protection scope of the present application. Some non-essential improvements and adjustments made by skilled persons in the art to the present application according to the above content of the present application still belong to the protection scope of the present application.

[0027] Referring to Figure 1 The SOA segmentation modeling simulation design method based on the space-time staggered half-step partitioning can include the following steps:

[0028] Step S101: In the light amplification direction of the SOA active region, the SOA active region is gradually segmented according to the way that the carrier concentration and the electric field component of the optical signal are staggered and half-steps in space-time, and a SOA segmented model based on staggered and half-steps in space-time is constructed.

[0029] Step S102: Using the constructed SOA segmented model based on staggered and half-steps in space-time, a plurality of parameter groups to be simulated are simulated respectively to obtain the simulation results of the SOA segmented model based on staggered and half-steps in space-time for each parameter group.

[0030] Step S103: The simulation results of each parameter group are analyzed to determine one or more parameter groups with performance meeting the requirements as the simulation optimization results of the SOA device.

[0031] Further, the step S102 includes: taking the carrier concentration at the balance time as the initial value of the carrier concentration of the semiconductor laser amplifier optical waveguide; segmenting the semiconductor laser amplifier optical waveguide device according to the direction of optical signal transmission to obtain a plurality of semiconductor laser amplifier optical waveguides each having a length of Δz; sampling the input optical signal according to a sampling time interval Δt to obtain M sampling points, wherein Δz=v g Δt, v g is the group velocity of the optical signal propagating in the semiconductor laser amplifier optical waveguide; the iteration equation of the calculation point of the optical signal is determined according to the differential equation satisfied by the SOA physical model; and the iteration equation of the calculation point of the carrier concentration is determined according to the rate equation satisfied by the semiconductor carrier concentration. Wherein the carrier concentration N[z, t] on the corresponding segment of the semiconductor laser amplifier optical waveguide contained in the iteration equation of the calculation point of the optical signal is the carrier concentration on the segment of the semiconductor laser amplifier optical waveguide after Δt / 2, and the signal intensity E[z, t] on the corresponding segment of the semiconductor laser amplifier optical waveguide contained in the iteration equation of the calculation point of the carrier concentration is the average of the signal intensities at the two ends of the segment of the semiconductor laser amplifier optical waveguide after Δt / 2.

[0032] Further, after the step S104, the method further includes: sequentially assigning one or more parameter groups with error vector magnitude meeting the requirements to the SOA contained in the system model, and simulating the system model to obtain the system simulation results of each parameter group, and analyzing the system simulation results of each parameter group to determine one or more parameter groups with performance meeting the requirements as the simulation optimization results of the system model.

[0033] This invention provides a novel spatiotemporally misaligned half-step partitioning SOA modeling and high-speed, efficient simulation design method for optical communication semiconductor laser amplifiers and semiconductor lasers. It features second-order accuracy. Compared to the simple piecewise models with first-order accuracy used in existing technologies, this invention eliminates first-order error terms by partitioning the active region of the spatiotemporally misaligned half-step amplifier, significantly improving simulation accuracy and computational efficiency. This allows for more efficient modeling and faster simulation of complex SOA devices, and significantly increases the number of optimization iterations and the range of parameter spaces traversed within a finite time. This can greatly improve the relevant electrical and optical performance indicators of the designed optical communication semiconductor laser amplifiers, semiconductor lasers, and similar semiconductor devices.

[0034] The following is through Figures 2 to 8 Please provide a detailed explanation.

[0035] See Figure 2 The structure of a common bulk semiconductor laser amplifier mainly includes an electrode 1 providing bias current, an active region 2, an anti-reflection surface 3, and an insulating layer 4, where the z-direction is the propagation direction of the signal light, and L is the total length of the SOA device. After the optical signal is coupled into the SOA, the high-energy carriers in the active region amplify the optical signal due to stimulated emission. Simultaneously, the bias current pumps continuously replenish the consumed high-energy carriers, ensuring the continuous amplification process. When the optical signal reaches the anti-reflection layer, the vast majority of the signal becomes the output signal, with only a very small portion becoming the back-propagating signal in the SOA. Generally, even after amplification, the proportion of the reflected signal in the final output light is still less than the proportion of spontaneous emission noise in the output light, so it can be ignored in practice. This invention still considers the reflected optical signal and its amplification, and this invention can accurately simulate this effect. Therefore, the modeling, simulation, and optimization design method of the optical waveguide of the semiconductor laser amplifier based on spatiotemporally staggered half-step partitioning of this invention involves the following four main steps:

[0036] Step (1): Extract the electrical, optical and electro-optic coupling parameter data of semiconductors or other electro-optic gain materials and SOA devices, such as the constraint factor and electro-optic gain parameter data.

[0037] Specifically, step (1) is as follows:

[0038] Step (1.1): Modeling and simulation of electrical properties of semiconductor or other electro-optical gain material and extraction of bandgap parameters. The parameters extracted in this step include: recombination coefficients (Shockley-Read-Hall recombination coefficient, Bimolecular recombination coefficient, Auger recombination coefficient, etc.), effective mass of light and heavy holes, bandgap width, carrier lifetime, carrier concentration at equilibrium, etc. The intrinsic parameters of these materials, related papers, databases such as "Wideband Semiconductor Optical Amplifier Steady-State Numerical Model" have detailed records. In industrial design applications, these parameters can also be obtained from laboratory tests. Related parameters of doped and other process modified materials can be found in the calculation formula or model of related semiconductor physics textbooks, or obtained from laboratory tests. For the carrier concentration at equilibrium, a pre-estimated value can be used, and in the model established in the following step (2), the input signal is set to zero input of the optical signal, and after a period of simulation, the value when the system reaches equilibrium is set as the carrier concentration at equilibrium.

[0039] Step (1.2): Modeling and simulation of the optical waveguide formed by the semiconductor or other electro-optical gain material and extraction of optical waveguide parameters. The parameters extracted in this step include: SOA length, active area, confinement factor, waveguide scattering loss coefficient, reflectivity of the input and output interfaces.

[0040] Among them, the SOA length and the active area are parameters that can be artificially determined in the SOA design process, and are often set to a certain range, and the SOA device that reaches system optimization is designed by traversing the related parameter values in the following steps (3) and (4).

[0041] Among them, the definition of the confinement factor Γ is given in the book "Physics of Optoelectronic Devices":

[0042]

[0043] Among them, E and H represent the electric field and magnetic field distribution at the signal input end face, is the unit vector along the signal propagation direction, and ds is a small surface element on the signal input end face.

[0044] Therefore, there are two calculation methods for the confinement factor: ① Through related FDTD electromagnetic simulation modeling, the optical mode of the corresponding SOA structure is simulated, and the confinement factor of the corresponding structure can be calculated using the above formula. ② For SOA structures with analytical solutions or approximate analytical solutions, the confinement factor can be calculated using analytical / numerical methods.

[0045] Step (1.3): Extraction of the confinement factor and electro-optical gain parameters data of the semiconductor or other electro-optical gain material. The parameters extracted in this step include, in particular, the differential gain parameter and its frequency response, the carrier concentration at transparency and its frequency response, the signal group velocity and its frequency response, the gain-phase coupling parameter.

[0046] where the differential gain dg / dN at the frequency of the input signal is determined using the gain parameter formula in the paper "Wideband Semiconductor Optical Amplifier Steady-State Numerical Model" and the parameters obtained in step (1.1).

[0047]

[0048] where the letters represent, respectively, g - gain of the g-SOA, v - carrier frequency, N - carrier concentration, c - speed of light, n1 - refractive index of the active region of the SOA, τ s - radiative carrier recombination lifetime, m e / m hh - effective mass of the conduction / valence band electron / hole, E g - bandgap, f c / f v - Fermi distribution function in the conduction / valence band, T0 - average lifetime of the electron under the action of an external field.

[0049] The parameters described in step (1.1) above can be obtained from published papers, material databases and laboratory tests, in addition to the methods and steps described above.

[0050] where the carrier concentration at transparency and its frequency response can be obtained from simulations and laboratory tests, the signal group velocity and its frequency response can be obtained from optical waveguide calculations, and the gain-phase coupling parameter can be obtained from laboratory measurements.

[0051] In one example, the parameters are extracted from the relevant literature, databases or laboratory measurements and recorded in Table 1. For parameters that can be artificially controlled and optimized, such as the length, width and geometry of the active region, the length of the device, etc., a series of values to be simulated are set.

[0052] Table 1. Values of a set of parameters selected in the example and the correspondence table of the letters and physical quantities.

[0053]

[0054] Step (2): The light amplification direction of the SOA active region is processed step by step in a way of time-space staggered half-step profiling, a time-domain mathematical physical model of light field and material gain segmentation is established, and simulation formulas and algorithms based on the model are obtained, and simulation calculation is implemented by hardware or software according to the above method.

[0055] In step (2), the following steps are included:

[0056] Step (2.1): The initial value of the carrier concentration of the semiconductor laser amplifier optical waveguide is given by using the carrier concentration at equilibrium given in step (1).

[0057] Specifically, the carrier concentration at equilibrium obtained in step (1) is taken as N p＝0 =N p＝0.5 p is a lower index used in carrier concentration calculation, that is, a time index (N p＝0 and N p＝0.5 represent the carrier concentrations at 0 and 0.5Δt, respectively, and Δt is the simulation time step).

[0058] Step (2.2): The semiconductor laser amplifier optical waveguide (device) is mathematically divided into multiple segments, such as N segments, in the optical signal transmission direction, such as the z direction. A 16-QAM signal of thousands of bits is generated using software or hardware, and the input optical signal to be simulated (or the optical signal to be input) is mathematically divided into multiple segments, such as M segments, in time t, each segment has a length of Δt, and is sampled at the beginning of each segment to obtain {E(mΔt)}. Alternatively, the input optical signal is sampled at intervals of Δt in time, a total of M sampling points are obtained, and an array composed of M complex numbers is obtained as the input signal of the simulation. At the same time, ensure that Δt=Δz / v g ,v g represents the group velocity of the optical signal in the semiconductor medium, which is obtained in step (1).

[0059] Referring to Figure 3 , the upper half is a profiling diagram of the SOA device with a length of L in the light propagation direction (z direction), each profiled small segment has a length of Δz, and the lower half is a time sampling of the input signal, the horizontal axis is time, and the vertical axis represents the instantaneous power of the signal. The sampling interval is Δt. Ensure that Δz=v g Δt, v g is the group velocity of the signal in the device.

[0060] So far, the mathematical model is accurate for the physical process: on each Δz segment, the optical signal propagates forward and backward in the waveguide, and amplification occurs due to the stimulated recombination of non-equilibrium carriers. The non-equilibrium carrier density evolves under the multiple actions of the applied current and the optical signal and spontaneous recombination. However, the above mathematical model does not have an analytical solution for an arbitrary signal, so the SOA is first divided into several small segments of length Δz for numerical calculation. Then, in the academic research and product development so far, the calculation points of the optical signal are selected as the midpoints or endpoints of the Δz segments of each SOA, and the calculation points of the carrier concentration are selected as the midpoints of the SOA Δz segments. At the same time, in time, the calculation points of the two are selected at the same time. The numerical modeling method above is called the synchronous subdivision modeling method in the present invention, which is essentially to regard the amplification of the optical signal on each SOA Δz segment as the result of the stimulated emission of the carrier concentration on the active region of the segment at the same time. And the change of the carrier concentration on each SOA Δz segment is calculated as the action of the average value of the signal intensity at the same time at the center or both endpoints of the Δz segment. It is obvious that the above simulation of continuous distributed amplification is an approximation in segmented amplification, because this changes the real physical transmission mechanism, thus causing simulation error. When Δz and Δt become smaller, the simulation error decreases and the simulation accuracy improves. When Δz tends to 0, the simulation error gradually disappears. However, when Δz and Δt become smaller, the total number of steps to be calculated becomes larger. When Δz and Δt become smaller and tend to 0, the total number of steps to be calculated tends to infinity, making calculation, simulation and optimization impossible. In the present invention, it is found that the synchronous subdivision modeling method described above is a first-order method, that is, when Δz is reduced by 2 times, the simulation error is reduced by 2 times. To achieve a certain simulation accuracy, Δz generally needs to be very small, resulting in a large number of calculation steps and a long simulation time, which is very low in efficiency.

[0061] Step (2.3): Establishing the calculation points of the optical signal to be calculated E(z,t) represents the electric field of the optical signal at z = nΔz, t = mΔt, and the value of z ranges from 0 to N+1. The differential equation satisfied by the commonly recognized physical model of the semiconductor laser amplifier is as follows: wherein E(z,t) represents the electric field of the optical signal at z = nΔz, t = mΔt, and the value of z ranges from 0 to N+1. The differential equation satisfied by the commonly recognized physical model of the semiconductor laser amplifier is as follows: + E(z,t) represents the electric field of the optical signal at z = nΔz, t = mΔt, and the value of z ranges from 0 to N+1. The differential equation satisfied by the commonly recognized physical model of the semiconductor laser amplifier is as follows: - E(z,t) represents the electric field of the optical signal at z = nΔz, t = mΔt, and the value of z ranges from 0 to N+1. The differential equation satisfied by the commonly recognized physical model of the semiconductor laser amplifier is as follows: H Γ, a, N0, α L and α L are the confinement factor, the differential gain, the carrier concentration when transparent, the gain-phase coupling parameter and the waveguide scattering loss, respectively. Based on the above differential equation, the iterative equation of the calculation point of the optical signal can be obtained: In the above formula, N[z, t] is preferably N[(n±0.5)Δz, (m+0.5)Δt]. In the usual method, N[z, t] is selected as N[nΔz, mΔt] or N[(n±0.5)Δz, mΔt].

[0062] Step (2.4): Establishing the calculation point of carrier concentration N[z, t] represents the carrier concentration at z = qΔz and t = pΔt. Both p and q are half-integers greater than 0 (i.e. 0.5, 1.5, 2.5,...). The carrier concentration of each section of the SOA at the time when the optical signal has entered the active region for Δt / 2 is calculated, at which time the optical signal has only entered the active region for Δz / 2, and the influence of the active region is ignored. Thus, the carrier concentration remains unchanged in the dynamic balance of injection and recombination of the electrical pump, i.e. N 0.5Δt = N0, N0 being the carrier concentration at equilibrium, which can also be referred to as the initial carrier concentration.

[0063] Step (2.5): According to the above formula, the iterative equation of the carrier concentration can be obtained.

[0064] The rate equation satisfied by the semiconductor carrier concentration is as follows:

[0065]

[0066] where I, e and V represent the driving current of the SOA, the elementary charge and the volume of the active region of the SOA respectively, A c is the cross-sectional area of the active region of the SOA, and E represents the energy of a photon; R is a recombination term related to the carrier concentration, and its specific form is R(N) = AN 2 + BN 3 + CN

[0067] The iterative equation of the carrier concentration is as follows:

[0068]

[0069] In the above formula, E[z, t] is selected as where E can represent E + or E - . In the usual method, the time index p of the carrier concentration N selected is an integer rather than a half-integer, and E ± [z, t] is or i.e. the time index of the calculation point of the carrier concentration is the same as that of the electric field component of the optical signal.

[0070] The process of selecting the calculation points of the optical signal electric field and carrier concentration in the above steps (2.3), (2.4), (2.5) is called the time-space staggered half-step partitioning. The closer the time-space steps Δz and Δt are to 0, the closer the simulation is to the real situation.

[0071] Referring to Figure 4 , Figure a) is a general partitioned calculation point arrangement, the horizontal axis represents the direction of the propagation of the optical signal, and the vertical axis represents the time direction. The black points represent the calculation points of the carrier concentration (N), the electric field of the forward propagating signal (E + ), and the electric field of the backward propagating signal (E - ). The brackets in the figure represent the time-space position of the calculation point, for example, N(4, 1) represents the carrier concentration calculation point located at 4Δz, Δt in space. Referring to Figure 4 , Figure b) is the calculation point arrangement used in the present application, the horizontal axis represents the direction of the propagation of the optical signal, and the vertical axis represents the time direction. The black points represent the calculation points of the electric field of the forward propagating signal (E + ) and the electric field of the backward propagating signal (E - ), and the hollow points represent the calculation points of the carrier concentration (N). The cross box and the two rounded rectangles in the figure represent the calculation points involved in the update equations of the carrier concentration, the electric field of the forward propagating signal, and the electric field of the backward propagating signal, respectively. Among them, the carrier concentration above the cross box is calculated using the carrier concentration below the cross box and the electric field values at the left and right ends; the electric field value at the upper right corner of the next time is calculated using the electric field value at the lower left corner of the rounded rectangle and the carrier concentration at the midpoint of the rounded rectangle. For the backward propagating signal, the update calculation is performed using the dashed rounded rectangle box. The non-synchronous (half-step) partitioning method of Δz segments proposed in the present application is a second-order method, which advances the calculation points of the carrier concentration in time by Δt / 2, and calculates the optical signal amplified on each semiconductor laser amplifier optical waveguide as the influence of the carrier concentration on the waveguide after Δt / 2. Moreover, the change of the carrier concentration on each semiconductor laser amplifier optical waveguide is calculated as the effect of the average of the signal intensity at the two ends of the waveguide after Δt / 2. The modeling method of the mathematical model partitioning of the semiconductor laser amplifier and the update calculation method of the electric field value and the carrier concentration are collectively referred to as the preferred time-space staggered half-step partitioning semiconductor laser amplifier modeling simulation method.

[0072] From Figure 4It can be seen that, compared with the synchronous profiling method, the application has the same number of calculation points and the same amount of calculation, i.e. the device length d is equal and Δz is equal, and the calculation complexity is equivalent. However, through computer simulation calculation verification, the half-step profiling modeling method of the application has a second-order accuracy, compared with the first-order accuracy of the synchronous modeling method described in the paper "Wideband dynamic numerical model of a tapered buried ridge stripe semiconductor optical amplifier gate" (IEE Proceedings-Circuits, Devices and Systems, VOL. 149, NO. 3, JUNE 2002), etc. By changing the space-time position of the calculation point of the carrier concentration and performing the update calculation of the electric field value and the carrier concentration as described above, the first-order error term is offset, the simulation accuracy is improved by an order of magnitude, so that the simulation accuracy can be improved by an order of magnitude by reducing the segmentation number N under the same simulation accuracy. Specifically, for the second-order method, when Δz is reduced by 2 times, the simulation error is reduced by 2 2 times; when Δz is reduced by 10 times, the simulation error is reduced by 10 2 times. To achieve a certain simulation high accuracy, the required Δz can be larger, so that the calculation step number is smaller, resulting in shorter simulation time and relatively great improvement of calculation efficiency compared with the first-order method.

[0073] Step (2.6): iteratively calculating the optical signal and the carrier concentration using the input optical signal, the initial carrier concentration and the response of the spatial boundary to the optical signal, and taking the output signal.

[0074] In short, in step (2), the prior art adopts the way of integer profiling of the carrier concentration and the electric field in time synchronization, while the application first adopts the way of half-step profiling of the carrier concentration and the electric field in time and space staggered grid. Compared with the prior art, the number of calculation points of the application does not increase, and the amount of calculation is the same, but the application eliminates the first-order error term by half-step profiling of the semiconductor laser amplifier optical waveguide in time and space staggered grid, improves the simulation accuracy by an order of magnitude, and can improve the calculation efficiency by an order of magnitude by reducing the segmentation number N under the same simulation accuracy.

[0075] It should be noted that the scope of the application is not limited by the above description of profiling, for example, the application is also applicable to other staggered grid step profiling of the carrier concentration and the electric field.

[0076] Step (3): Perform data analysis and extraction on the device simulation results to obtain device and system design parameter results, including input signal power, SOA geometric parameters such as length, pump current and other device optimization parameter results.

[0077] Specifically, for the multiple input parameters in step (1), simulations are performed sequentially to calculate the corresponding EVM (error vector magnitude), and several parameter combinations with better performance are selected as the candidate parameter space for step (4).

[0078] Step (4): Use the system model containing the semiconductor laser amplifier to perform system-level simulation and calculation to obtain system simulation and optimization design results.

[0079] In practical system simulation applications, for example... Figure 5 In the coherent optical communication system based on M-order quadrature amplitude modulation (QAM) shown, the fiber input power is a system-level candidate parameter that needs to be optimized, and the corresponding SOA device candidate parameter can be the pump current. Using the modeling in step (2), the candidate parameter space obtained in step (3), such as the magnitude of the pump current, is traversed by system simulation to determine the final optimization result.

[0080] The SOA system optimization process in steps (3) and (4) is described in [reference needed]. Figure 6 Specifically, it includes:

[0081] Step ①: Determine the optimization parameters (e.g., the length and geometry of the active region, the length of the device, the magnitude of the pump current, etc.) and their possible ranges, and generate multiple sets of parameters to be simulated based on the range with appropriate step sizes;

[0082] Step 2: Determine whether device simulation has been performed for all parameter groups. If yes, proceed to step 6; otherwise, proceed to step 3.

[0083] Step 3: Perform device simulation using the method in step (2) and calculate the EVM (error vector magnitude) of the output result;

[0084] Step 4: If the EVM of this parameter group meets the requirements, proceed to step 5;

[0085] Step 5: Save this parameter set to the parameter set of the system simulation;

[0086] Step 6: Perform system simulation and calculate the BER (Bit Error Rate) of the output results;

[0087] Step 7: Determine whether the BER of the parameter group meets the requirements. If yes, proceed to step 8; otherwise, proceed to step 6.

[0088] Step 8: Save this parameter set to the simulation optimization results.

[0089] The following is the numerical simulation verification and comparison of the traditional synchronization-based segmentation method and the segmentation-based semiconductor laser amplifier optical waveguide segment modeling simulation design method of the present application.

[0090] Using the parameters given in Table 1, a numerical simulation model is established. A set of binary numbers randomly generated by a computer is used as the transmitted data. The set of binary numbers is encoded into 512 symbols in 16QAM modulation format. The signal interval Δt corresponding to each symbol is sampled into a number of discrete values to form a one-dimensional array. The simulation is performed according to the synchronization segmentation "split1" and the half-step segmentation "split2" respectively, and the optical signal at the end of the semiconductor laser amplifier optical waveguide is recorded as the output signal E out , note that its numerical accuracy depends on Δz. As described in the paper "Symmetrized SSF scheme to control global simulation accuracy in fiber optic communication systems" (IEEE JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 26, NO. 2, JANUARY 2008), the normalized standard deviation (nsd) is used as a measure of global error , but is defined as the difference between the approximate solution at a certain step size Δz and the "true solution" obtained by using very small Δz or very large number of steps N steps for each symbol.

[0091] Referring to Figure 7 , Split1 is the output result of synchronization segmentation, Split2 is the output result of staggered half-step segmentation, and True solution is the "true solution" obtained by using the split1 method (i.e. in synchronization segmentation format) with N steps = 4096 steps, the output signal waveforms obtained by the two segmentation methods are compared with the true solution, and the same N steps , the result of half-step segmentation is closer to the true solution.

[0092] The relationship between the number of steps N steps and the global error of nsd is shown in the attached Figure 8As shown, the horizontal axis is the number of steps used for each symbol, and the vertical axis is the global error, FO-FDM is a first-order finite difference method, that is, a common synchronous subdivision format, and SO-FDM is a second-order finite difference method, that is, the staggered half-step subdivision of the present application. Among them, the half-step subdivision method, that is, split 2, is proved to be a second-order method: when the step length is halved, the error of nsd is reduced to 1 / 4. The synchronous subdivision method, that is, split 1, is proved to be a first-order method, and it needs more simulation steps to achieve the same nsd. In the precision or error level, compared with the synchronous subdivision method, the half-step subdivision method needs only 1 / 3 of the number of subdivisions of the former, and the number of calculation steps is only 1 / 9 of the former due to the subdivision in time and space; in the precision level, compared with the synchronous subdivision method, the half-step subdivision method needs about 1 / 10 of the number of subdivisions, that is, 1 / 100 of the number of calculation steps, and can improve the calculation efficiency by about 100 times. In the case of high-capability error correction code in optical communication, the precision level is higher, and in this case, the staggered half-step subdivision method can speed up more than the synchronous subdivision method.

[0093] In summary, the present application has the following technical effects:

[0094] (1) In the simulation calculation of semiconductor laser amplifiers, semiconductor lasers and various electrical and optical devices based on the physical mechanism or mathematical model of semiconductor laser amplifiers, the present application solves the problem of low calculation efficiency and long time-consuming in optimization design caused by the current general first-order precision modeling simulation calculation method, and provides a new calculation point distribution method for the high-speed simulation field of optical communication amplifiers;

[0095] (2) The present application offsets the calculation points of the segmented semiconductor laser amplifier, so that the calculation points of the optical signal electric field and the calculation points of the carrier density are offset by half the subdivision width in time and space. This staggered offset is the key to achieving second-order accuracy and is a major performance improvement over the current first-order precision modeling simulation technology;

[0096] (3) The present application offsets the calculation points of the segmented semiconductor laser amplifier to eliminate the first-order error term, thereby increasing the simulation accuracy and calculation efficiency by orders of magnitude, allowing more realistic large-signal modeling and faster large-signal simulation of complex semiconductor laser amplifiers, and increasing the number of optimization iterations in a limited time, which can greatly improve the performance indicators of the designed high-speed semiconductor laser amplifier for optical communication.

[0097] Although exemplary embodiments of the present application have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the application as disclosed in the accompanying claims, and that all such modifications, additions and substitutions are intended to be included within the scope of the present application. Accordingly, the description of the embodiments of the present application are not intended to limit the scope of the present application, but to describe the present application. Accordingly, the scope of the present application is not limited by the above embodiments, but is defined by the claims or their equivalents.

Claims

1. A SOA segment modeling simulation design method based on space-time staggered half-step split, characterized in that, The method comprises the following steps: In the light amplification direction of the SOA active region, the SOA active region is gradually segmented according to the way that the carrier concentration and the electric field component of the optical signal are staggered and half-steps divided in space-time, and a SOA segmented model based on staggered and half-steps divided in space-time is constructed; The simulation results of the SOA segmented model based on staggered and half-steps divided in space-time for each parameter group are obtained by simulating a plurality of parameter groups to be simulated respectively by using the constructed SOA segmented model based on staggered and half-steps divided in space-time. The simulation results of each parameter group are analyzed to determine one or more parameter groups with performance meeting the requirements as the simulation optimization results of the SOA device.

2. The method of claim 1, wherein, The method further comprises the following steps: Obtaining parameter data required by the SOA segmented model based on staggered and half-steps divided in space-time, so that the parameter data is directly used in the constructed SOA segmented model based on staggered and half-steps divided in space-time.

3. The method of claim 2, wherein, The parameter data includes band gap parameter data, optical waveguide parameter data, confinement factor and electro-optical gain parameter data.

4. The method of claim 3, wherein, The band gap parameter data includes carrier concentration at equilibrium, and the acquisition method comprises the following steps: in the constructed SOA segmented model based on staggered and half-steps divided in space-time, simulating with zero input optical signal as input signal, and taking the value of the model at equilibrium as the carrier concentration at equilibrium.

5. The method of claim 3, wherein, The electro-optical gain parameter data includes the group velocity of the signal, and the acquisition method comprises one of the following methods: obtaining from known literature or database; extracting by laboratory measurement.

6. The method of claim 1, wherein, The method of gradually segmenting the SOA active region in the light amplification direction of the SOA active region according to the way that the carrier concentration and the electric field component of the optical signal are staggered and half-steps divided in space-time comprises the following steps: Taking the pre-acquired carrier concentration at equilibrium as the initial value of the carrier concentration of the semiconductor laser amplifier optical waveguide; Segmenting the semiconductor laser amplifier optical waveguide device according to the transmission direction of the optical signal to obtain a plurality of semiconductor laser amplifier optical waveguides with each segment having a length of Δz; According to a sampling time interval Δt, the input optical signal is sampled to obtain M sampling points, wherein Δz = v g Δt, v g is the group velocity of the optical signal propagating in the optical waveguide of the semiconductor laser amplifier; According to the differential equation satisfied by the SOA physical model, the iterative equation of the calculation point of the optical signal is determined, wherein the carrier concentration N[z,t] on the corresponding segment of the semiconductor laser amplifier optical waveguide contained in the iterative equation of the calculation point of the optical signal is the carrier concentration on the segment of the semiconductor laser amplifier optical waveguide after Δt / 2.

7. The method of claim 6, wherein, The method of gradually segmenting the SOA active region in the light amplification direction of the SOA active region according to the way that the carrier concentration and the electric field component of the optical signal are staggered and half-steps divided in space-time further comprises the following steps: According to the rate equation satisfied by the semiconductor carrier concentration, the iterative equation of the calculation point of the carrier concentration is determined, wherein the signal intensity E[z,t] on the corresponding segment of the semiconductor laser amplifier optical waveguide contained in the iterative equation of the calculation point of the carrier concentration is the average value of the signal intensity at the two ends of the segment of the semiconductor laser amplifier optical waveguide after Δt / 2.

8. The method of claim 1, wherein, The plurality of parameter groups to be simulated are obtained by the following steps: Selecting adjustable and optimizable design parameters from pre-acquired parameters of semiconductor or other electro-optical gain materials as to-be-simulated parameters; According to the to-be-simulated parameters and their ranges, generating a plurality of to-be-simulated parameter groups, wherein each to-be-simulated parameter group includes all to-be-simulated parameters and parameter values within their ranges.

9. The method of claim 1, wherein, The data analysis of the simulation results of each parameter group to determine one or more parameter groups meeting the performance requirements as the simulation optimization results of the SOA device includes: Calculating the error vector magnitude of the simulation results of each parameter group; Selecting and saving one or more parameter groups with error vector magnitudes meeting the requirements from the plurality of parameter groups as the simulation optimization results of the SOA device.

10. The method according to any one of claims 1 to 9, characterized in that, The method further includes: Assigning the one or more parameter groups with error vector magnitudes meeting the requirements to the SOA included in the system model in sequence, simulating the system model, and obtaining system simulation results of the system model for each parameter group with error vector magnitudes meeting the requirements; Calculating the bit error rate of the system simulation results of each parameter group, and selecting one or more parameter groups with bit error rates meeting the requirements as the simulation optimization results of the system model.

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