Gain fluctuation optimization method and device for erbium-doped optical fiber amplifier

Abstract

The invention relates to the technical field of optical communication, and provides a gain fluctuation optimization method and device for an erbium-doped optical fiber amplifier. According to the method, the demand slope is kept unchanged, and a relation curve between the fiber length corresponding to the original spectral shape and the attenuation variation is determined; and keeping the demand slope unchanged, and performing addition and subtraction operation to enable the relation curve to be approximate to a regression straight line, thereby obtaining a target spectral shape. According to the invention, the spectral shape is changed only by adding and subtracting the fibers, the gain flattening filter does not need to be replaced, the practicability is high, and the problem that the practicability is poor due to the fact that the gain fluctuation performance index is met by repairing and replacing a large number of gain flattening filters in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a method and apparatus for optimizing the gain fluctuation of an erbium-doped fiber amplifier. Background Technology

[0002] Fiber optic amplifiers are one of the most important components in optical communication systems. With the development of optical communication technology, the requirements for amplifiers in optical communication systems are becoming increasingly stringent, and various performance indicators are becoming more and more demanding.

[0003] Among the various performance indicators, the gain ripple (GR) of the gain flat filter reflects the degree of fluctuation of the gain spectrum of the erbium-doped fiber amplifier (EDFA) in a specific wavelength band; the smaller the gain ripple, the more uniform the amplifier's amplification capability of optical signals, and the lower the bit error rate of the multi-wavelength system.

[0004] EDFA gain spectral optimization can be achieved through various techniques, with the most common industrial approach being the adjustment of the core optical component, the gain flattening filter (GFF). As a crucial passive component, the GFF works by designing specific wavelength-dependent loss characteristics to precisely compensate for the original non-flat gain spectrum of the EDFA, flattening or smoothing out uneven signal strengths within a specified wavelength range. When adjusting the output spectrum, technicians can replace the GFF module with one of different specifications, utilizing its customized filtering curve to selectively attenuate gain peaks and valleys, thereby achieving gain equalization within the target wavelength range. This hardware configuration adjustment method, due to its repeatability and intuitive results, has become a standardized solution for EDFA spectral optimization.

[0005] However, the actual spectral shape of EDFA products using combined gain-flattening filters is difficult to achieve the ideal situation. The main reasons are: (1) There are often module differences in the overall loss of EDFA products during the manufacturing process; (2) The insertion loss of some passive optical devices (such as couplers, filters, wavelength selective switches and variable optical attenuators) used in EDFA products is not consistent at different operating wavelengths, that is, there are differences in wavelength-dependent loss (WDL). Moreover, in the mass production stage of EDFA, when the gain fluctuation index exceeds the standard, a large number of gain-flattening filters need to be repaired and replaced to meet the gain fluctuation performance index. This is costly, inefficient, and may not be able to ensure the production quality of EDFA, posing a certain quality risk and poor practicality.

[0006] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method and apparatus for optimizing the gain fluctuation of an erbium-doped fiber amplifier. Its purpose is to change the spectral shape simply by adding or removing fibers. It is highly practical and solves the problem of poor practicality of existing technologies that require a large number of rework and replacement of gain-flattening filters to meet the gain fluctuation performance index.

[0008] The present invention adopts the following technical solution: In a first aspect, the present invention provides a method for optimizing the gain fluctuation of an erbium-doped fiber amplifier, comprising: Keeping the demand slope constant, determine the relationship curve between fiber length and attenuation change corresponding to the original spectrum shape; While keeping the demand slope constant, fiber addition and subtraction operations are performed to make the relationship curve approximate a regression line, thus obtaining the target spectrum.

[0009] Furthermore, maintaining the demand slope unchanged while performing fiber addition / reduction operations includes: Based on the aforementioned relationship curve, determine the gain variation of different gain spectra at different wavelengths; Select at least two characteristic bands from all the gain variations; Determine the spectral shape coefficients of the characteristic band; Fiber addition and subtraction operations are performed based on the required slope and the spectral value coefficient.

[0010] Further, determining the spectral shape coefficients of the characteristic band includes: The slope of the linear relationship between the gain change and fiber length change in the characteristic band is determined as the spectral shape coefficient.

[0011] Furthermore, the fiber addition / reduction operation based on the demand slope and the spectral shape coefficient includes: The fiber length is generated according to the required slope and the spectral shape coefficient; Perform the fiber addition / reduction operation according to the stated fiber addition / reduction length.

[0012] Further, generating the fiber addition / reduction length according to the required slope and the spectral shape coefficient includes: Obtain the average actual gain of each of the characteristic bands; Based on the required slope and the total reference gain, the average of each actual gain is processed to obtain the fiber addition / reduction length.

[0013] Further, the step of processing the average of each actual gain based on the demand slope and the total reference gain to obtain the fiber addition / reduction length includes: Determine a first difference between the average actual gain under ideal conditions and the total reference gain; Based on the required slope and the first difference, determine the first deviation between the average actual gain and the total reference gain under ideal conditions; Determine a second difference between the first difference and the first deviation, and determine the product of the second difference and the spectral shape coefficient as the first length; The average of all the first lengths is used to obtain the fiber addition and subtraction lengths.

[0014] Furthermore, the step of processing the average of each actual gain based on the demand slope and the total reference gain to obtain the fiber addition / reduction length also includes: Obtain the actual gain value of the last feature point from the last of the aforementioned feature bands; Determine a third difference between the actual gain value and the total reference gain under ideal conditions; Based on the demand slope and the third difference, determine the second deviation between the actual gain value and the total reference gain under ideal conditions; Determine a fourth difference between the third difference and the second deviation, and determine the product of the fourth difference and the spectral shape coefficient corresponding to the feature point as the second length; The average of all the first lengths and the second lengths is used to obtain the fiber addition and subtraction lengths.

[0015] Furthermore, the determination of the relationship curve between fiber length and attenuation change corresponding to the original spectral shape includes: A first relationship curve is determined between the attenuation change and the first gain slope. Outliers in the first relationship curve are eliminated to obtain a first processing curve. The wavelength and gain change corresponding to the first processing curve are obtained, and the slope of the second relationship curve between the obtained wavelength and the corresponding gain change is determined as a first coefficient. According to the first coefficient of each wavelength, a first change relationship is obtained. The first change relationship is: the gain change of each wavelength corresponding to the change in gain slope per unit caused by the change in attenuation. A second relationship curve between fiber length and second gain slope is determined, outliers in the second relationship curve are eliminated, and a second processing curve is obtained; the slope of the second processing curve is determined as the second coefficient. Based on the first change relationship and the second coefficient, the fiber length change and attenuation change are combined to obtain a variety of optional combinations; wherein, the optional combination is: a combination of fiber length change and attenuation change that keeps the gain slope unchanged when the fiber length change and attenuation change ... Obtain the wavelength and gain change corresponding to the second processing curve, and determine the slope of the third relationship curve between the obtained wavelength and the corresponding gain change as the third coefficient; according to the third coefficient of each wavelength, obtain the second change relationship; wherein, the second change relationship is: the gain change of each wavelength corresponding to the change of each unit fiber length. Based on the first and second variation relationships, the relationship curve between fiber length and attenuation change corresponding to the original spectrum shape is obtained.

[0016] Secondly, the present invention also provides a gain fluctuation optimization device for an erbium-doped fiber amplifier, comprising: At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor for performing the gain fluctuation optimization method for the erbium-doped fiber amplifier described in the first aspect.

[0017] Thirdly, the present invention also provides a non-volatile computer storage medium storing computer-executable instructions that are executed by one or more processors to perform the gain fluctuation optimization method for the erbium-doped fiber amplifier described in the first aspect.

[0018] Fourthly, a computer program product containing instructions is provided, which, when executed on a computer or processor, causes the computer or processor to perform a gain fluctuation optimization method for an erbium-doped fiber amplifier as described in the first aspect.

[0019] Fifthly, the present invention also provides a gain fluctuation optimization system for an erbium-doped fiber amplifier, comprising an erbium-doped fiber amplifier gain fluctuation optimization device as described in the second aspect, and using the erbium-doped fiber amplifier gain fluctuation optimization method as described in the first aspect to complete the interaction of the erbium-doped fiber amplifier gain fluctuation optimization device of the second aspect.

[0020] Unlike existing technologies, the present invention has at least the following beneficial effects: This invention determines the relationship curve between fiber length and attenuation change corresponding to the original spectrum shape. By simply adding or removing fibers, the relationship curve can be made to approximate a regression line and meet the required slope, thereby changing the spectrum shape to obtain the target spectrum shape, which can satisfy the gain fluctuation performance index. There is no need to repair or replace a large number of gain flat filters. The cost of replacing gain flat filters is much greater than the cost of changing fiber length, and the efficiency of replacing gain flat filters is much lower than the efficiency of changing fiber length, making it highly practical. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0022] Figure 1 This is a flowchart illustrating a method for optimizing the gain fluctuation of an erbium-doped fiber amplifier according to an embodiment of the present invention. Figure 2 This is a schematic diagram illustrating a specific example of the relationship between attenuation change and fiber length provided by an embodiment of the present invention; Figure 3 This is a schematic diagram of a process for changing fiber length according to required slope, provided by an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating a specific example of the gain difference before and after fiber addition, provided by an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating a specific example of a test data table provided in an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating a specific example of a gain versus wavelength variation curve provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of a process for changing fiber length according to adding or subtracting fiber length provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the overall process for determining the fiber addition / reduction length provided in an embodiment of the present invention; Figure 9 This is a schematic diagram illustrating a specific process for determining the length of added or removed fibers, provided by an embodiment of the present invention. Figure 10 This is a schematic diagram illustrating another specific process for determining the fiber addition / reduction length provided in an embodiment of the present invention; Figure 11 This is a schematic diagram of the architecture of a gain fluctuation optimization device for an erbium-doped fiber amplifier provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0025] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0026] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0027] In describing some embodiments, the terms "coupled," "coupled," and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the terms "connected" or "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other, such as "optical coupling," "wireless connection," etc. The embodiments disclosed herein are not necessarily limited to the scope of this invention.

[0028] In the description of this invention, the expression “A and / or B” (where A and B are used to formally represent specific features) will be used. The corresponding expression includes the following three combinations: only A, only B, and a combination of A and B.

[0029] As used in this invention, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from a particular value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0030] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1: The core gain medium of EDFA (Erbium-Doped Fiber Amplifier) ​​is erbium-doped fiber, which is erbium ions doped into a silica-based optical fiber. Erbium ions have a unique energy level structure, and their working mechanism is based on stimulated emission: when external pump light is injected, erbium ions absorb the pump light energy and transition from the ground state to a metastable energy level, forming a population inversion distribution. When the signal light passes through the erbium-doped fiber, the metastable erbium ions transfer their stored energy to the signal photons through stimulated emission, achieving coherent amplification of the optical signal. This amplification mechanism has typical wavelength selectivity: the energy level transitions of erbium ions correspond to specific wavelength ranges (e.g., 1530 nm to 1565 nm in the conventional C-band), resulting in significant differences in the gain coefficient of the EDFA for different wavelengths. Its gain spectrum exhibits non-flat characteristics, specifically, a gain peak appears in a specific wavelength region (e.g., around 1532 nm), while the gain gradually decreases in longer or shorter wavelength regions. This gain non-uniformity is called the gain tilt. This characteristic stems from the wavelength correlation of the radiative transition probability between erbium ion energy levels, which is the physical basis for EDFA to achieve optical amplification, but it also limits its direct application in broadband amplification scenarios.

[0032] A gain spectrum curve consists of multiple discrete data points, and a regression line (i.e., a trend line) can be fitted using statistical methods. This trend line is usually non-horizontal, possibly exhibiting a positive or negative slope, the slope of which is the gain tilt. The actual gain spectrum distribution shows periodic fluctuations around this trend line, and the magnitude of these fluctuations can be quantified using the gain ripple parameter. This fluctuation characteristic reflects the non-ideal nature of the spectral response and is one of the important indicators for evaluating the performance of optical devices.

[0033] For ease of description, "product" will be used to refer to "EDFA product" and will not be repeated in the following text.

[0034] In practical applications, during the mass production of EDFAs, once a single product achieves optimal performance through gain flattening filter optimization, it cannot be directly applied to mass production scenarios. The specific problems are as follows: Although the length of the erbium-doped fiber (i.e., fiber length) of all products is strictly controlled within the design value, due to the inherent characteristics of optical devices, there is an uncontrollable process deviation in the total insertion loss of each device. This total insertion loss (i.e., insertion loss) mainly consists of three parts: (1) inherent device loss; (2) fusion splicing loss: caused by axial offset and end face gap due to heat shrink tubing packaging process during fiber fusion splicing; (3) winding loss: micro-bending loss generated by fiber in the fiber coiling process due to modular packaging requirements.

[0035] Insertion loss is a random superposition of the three losses mentioned above. Every optical module will have these three types of insertion loss, and these three types of insertion loss are uncontrollable. Since insertion loss cannot be accurately predicted and controlled during the production stage using existing technology, even if the fiber length is kept constant, the actual gain characteristics of each EDFA will still vary significantly.

[0036] As a critical spectral shaping component, the gain flattening filter's filtering curve must precisely match the gain spectrum of a specific EDFA. In single-unit commissioning scenarios, the gain tilt and gain ripple of the device can be compensated by replacing it with a customized gain flattening filter. Each EDFA requires an independently designed gain flattening filter. However, in mass production, requiring each EDFA to be equipped with an independently designed gain flattening filter necessitates a separate spectral testing and gain flattening filter selection process for each unit, resulting in excessively high manpower and material costs. Furthermore, the lack of standardized configuration options makes it difficult to guarantee product quality consistency, rendering the process impractical for production.

[0037] The following explains why configuring a gain-flattening filter is too costly: For example, even ignoring the design cost of the gain flattening filter, the procurement cost cannot be ignored because each EDFA requires an independent gain flattening filter.

[0038] Next, replacing the gain flattening filter is also costly. The replacement process is not a simple device swap; it involves a series of complex procedures and potential risks. Inside the EDFA, more than twenty critical components are precisely arranged, interconnected by optical fibers, with each pair of connections secured and protected by heat-shrink tubing. When replacing a single component, such as the gain flattening filter, the component must first be located, and then the heat-shrink tubing connections on both sides must be carefully disconnected. This process requires extremely high precision because optical fibers are inherently fragile; even slight scratches or twists can cause breakage or damage. Damage to the fiber will severely affect optical signal transmission and may even lead to the failure of the entire EDFA system.

[0039] Besides the cost of the components themselves, labor costs are also a significant factor. A skilled repair technician needs approximately half an hour to complete the entire replacement process, including locating the component and disconnecting and reconnecting the heat shrink tubing. Therefore, from a direct cost perspective alone, replacing a gain-flattening filter is quite expensive.

[0040] Furthermore, after replacing the gain-flattening filter, rigorous testing is required to ensure the stability of the EDFA system. Since replacing components can impact the overall system performance, multiple tests and adjustments are typically necessary. Ideally, at least one fiber length adjustment should be performed to optimize system performance. These subsequent tests and adjustments undoubtedly increase costs and time investment.

[0041] To solve the above problems, such as Figure 1 As shown, this embodiment of the invention provides a method for optimizing the gain fluctuation of an erbium-doped fiber amplifier, including: Step 10: Keep the demand slope constant and determine the relationship curve between fiber length and attenuation change corresponding to the original spectrum.

[0042] The method for determining the relationship between fiber length and attenuation change corresponding to the original spectrum shape is selected by those skilled in the art based on the specific application scenario. It should be noted that step 10 of this embodiment is used to obtain the relationship between fiber length and attenuation change while maintaining the target demand slope (Tilt) unchanged. Without this premise, there is no correlation between these two variables.

[0043] In one embodiment, the original spectrum can be the actual spectrum obtained by testing the EDFA. The fiber length corresponding to the original spectrum is the current fiber length of the EDFA at each test. The current fiber length is the length of the erbium-doped fiber in the product, excluding the fiber length of ordinary devices. The attenuation change is expressed in decibels (dB). The attenuation change is the change in power attenuation after the optical signal passes through a variable optical attenuator (VOA), i.e., the adjustment amount by the VOA to the degree of optical signal attenuation. The VOA is an important passive optical device in optical fiber communication, achieving real-time signal control by attenuating the transmitted optical power; the VOA can adjust the signal strength in real time to ensure the stability and reliability of the signal during transmission.

[0044] In one alternative embodiment, precise control of the EDFA gain spectrum and output power can be achieved by dynamically adjusting the attenuation change. The relationship curve characterizes the relationship between the current fiber length of the EDFA and the corresponding attenuation change at each test.

[0045] Step 20: Keep the demand slope unchanged and perform fiber addition / reduction operations to make the relationship curve approximate a regression line to obtain the target spectrum.

[0046] Wherein, the demand slope is the final gain slope to be achieved. While dynamically adjusting the attenuation change to maintain a constant demand slope, the EDF length is adjusted so that the relationship curve approximates a regression line, thus obtaining the target spectrum. The ultimate goal of gain fluctuation optimization in this embodiment of the invention is to make the gain slope of the relationship curve as equal to the demand slope as possible. Step 10 above is used to obtain a method for dynamically adjusting the attenuation change to maintain a constant demand slope, and step 20 is used to reduce gain fluctuation using the obtained method.

[0047] For EDFA, the relationship between spectral shape and gain is reflected in the direct impact of the shape of the gain spectrum (i.e., the gain distribution at different wavelengths) on the overall amplification performance. The spectral shape is quantified by parameters such as gain slope and gain fluctuation. By adjusting the length of the erbium-doped fiber or using VOA to change the spectral shape parameters, the increase or decrease of gain at each wavelength can be controlled (e.g., reducing the gain slope), ultimately achieving precise optimization of gain fluctuation and gain slope to meet the user's needs for a specific spectral shape (i.e., the target spectral shape).

[0048] In one embodiment, the required slope can be provided by the user. Fiber addition / removal operations refer to adjusting the optical path structure of the EDAF product by physically disconnecting and / or fusion splicing optical fibers, or adjusting heat shrink tubing connections.

[0049] Fiber addition and removal operations optimize the optical signal transmission path and compensate for losses by changing the number or length of fiber segments. Fiber removal only requires disconnecting one heat-shrink tubing node, removing part of the fiber, and then re-soldering; fiber addition requires disconnecting one heat-shrink tubing node and soldering two nodes (to connect the new fiber segment to the optical path). Both types of operations have low material and labor costs, are convenient to operate, and have simple processes; erbium-doped fiber is relatively inexpensive.

[0050] Existing technologies optimize gain fluctuations by extensively reworking and replacing gain-flattening filters. Rework refers to the process of locating and addressing specific fault nodes within the multi-layer heat-shrink tubing protection structure when performance anomalies (e.g., excessive gain fluctuations) occur in the EDFA optical path. Compared to fiber addition / removal operations, rework requires deep penetration into the internal structure of the optical path; and after replacing the gain-flattening filter, the performance indicators often fail in subsequent tests, necessitating further fiber addition / removal. Fiber addition / removal operations are very common in the EDFA field, requiring only adjustment of the top layer heat-shrink tubing, resulting in high operational efficiency; furthermore, the heat-shrink tubing is clearly marked, further improving the efficiency of fiber addition / removal operations. In one embodiment, fiber removal takes only about ten minutes, and fiber addition takes only about 15 minutes.

[0051] The method for optimizing the gain fluctuation of the erbium-doped fiber amplifier according to an embodiment of the present invention will now be described in detail: Increasing the fiber length of an EDFA does not simply change the gain slope; it usually also affects the spectral shape. The change in gain at each wavelength caused by increasing or decreasing the VOA is relatively linear. This linear relationship applies to most modules under the same optical path structure. For example, if the fiber length and VOA attenuation of an L++ band EDFA module are increased, the spectral shape will change to some extent while keeping the gain slope and output power constant. This typically manifests as: increased gain at mid-wavelengths, slightly decreased gain at the initial wavelength, and a significant decrease in gain at the tailwave. The gain change at corresponding characteristic points shows a clear linear relationship with the fiber length change. In other words, by observing the gain spectral shape, it is possible to determine how to adjust the spectral shape to achieve optimal gain fluctuation by adding or removing fibers.

[0052] The essence of the gain fluctuation optimization method for erbium-doped fiber amplifiers in this invention is to make the graph of the relationship curve as close as possible to the trend line. The gain spectrum curve is composed of multiple discrete data points, and a regression line (i.e., the trend line) can be fitted using statistical methods. By making the relationship curve as close as possible to a straight line and approximate the regression line, the gain fluctuation is minimized.

[0053] This invention determines the relationship curve between fiber length and attenuation change corresponding to the original spectrum shape. By simply adding or removing fibers, the relationship curve can be made to approximate a regression line and meet the required slope, thereby changing the spectrum shape to obtain the target spectrum shape, which can satisfy the gain fluctuation performance index. There is no need to repair or replace a large number of gain flat filters. The cost of replacing gain flat filters is much greater than the cost of changing fiber length, and the efficiency of replacing gain flat filters is much lower than the efficiency of changing fiber length, making it highly practical.

[0054] The following describes the application scenarios of the gain fluctuation optimization method for erbium-doped fiber amplifiers according to embodiments of the present invention: During the commissioning of EDFA, a complete test is first performed on the product to obtain its initial gain characteristics (e.g., relationship curves). For this type of product, only the spectral shape coefficient needs to be calculated once. When the product requires subsequent fiber addition or subtraction operations, without actual equipment operation, the gain change at each point within the gain wavelength range (i.e., the specific value of gain increase or decrease) can be calculated by multiplying the known spectral shape coefficient by the fiber addition or subtraction length (e.g., increasing or decreasing by 135 cm). This accurately predicts the test results after fiber addition or subtraction operations, including indicators such as gain slope and gain fluctuation. Based on this predictive capability, the required fiber addition or subtraction length can be calculated backward based on the user's specific indicators of gain slope and gain fluctuation (e.g., gain slope equal to -1, gain fluctuation less than 1.5 dB), so that the adjusted gain fluctuation reaches a minimum (e.g., 0.5 dB) to precisely meet the user's needs. This process only requires the basic data from the initial test, and adjustments can be guided by calculation without repeated actual equipment operation.

[0055] In one embodiment, routine testing is performed on EDFA products. For EDFA products with excessive gain fluctuation, the gain fluctuation optimization method of the erbium-doped fiber amplifier of this invention is used to optimize gain fluctuation by adding or removing fibers. The specific operation steps of this embodiment are described below: Step 10 includes determining the relationship curve through testing: A first relationship curve is determined between the attenuation change and the first gain slope. Outliers in the first relationship curve are eliminated to obtain a first processed curve. In one embodiment, the R-Squared (RSQ) function is used to eliminate outliers, and the slope function is used to calculate the slope of the first processed curve as the first coefficient. The slope of the first processed curve represents the change in gain slope caused by adjusting the attenuation change by one dB; for example, the slope of the first processed curve can represent that adjusting the attenuation change by 1 dB will change the gain slope by 0.8 dB. Based on this, the relationship between the attenuation change and the gain spectrum is determined, and the wavelength and gain change corresponding to the first processed curve are obtained. The slope of the second relationship curve between the obtained wavelength and the corresponding gain change is determined as the first coefficient. According to the first coefficient for each wavelength, a first change relationship is obtained; wherein, the first change relationship is: the gain change for each wavelength corresponding to the change in gain slope per unit caused by the change in attenuation change. In one embodiment, the unit of gain slope can be decibels. Since the effect of attenuation change adjustment on each wavelength is very different, especially the wavelength difference in the short wavelength range is obvious. Therefore, based on the first processing curve, the slope is calculated for the gain change at each wavelength to obtain the first coefficient corresponding to each wavelength. For example, the first change relationship can be "the gain change per decibel due to the change in attenuation, corresponding to the gain change at each wavelength". An Excel template can be created based on the first change relationship to deduce how the gain spectrum changes after changing the attenuation.

[0056] A second relationship curve is determined between fiber length and a second gain slope. Outliers in the second relationship curve are eliminated to obtain a second processed curve. The slope of the second processed curve is determined as a second coefficient. The second coefficient represents the relationship between fiber length and gain slope; for example, the second coefficient can represent that increasing the fiber length by 175 cm will change the gain slope by 1 dB. In one embodiment, the RSQ function can be used to eliminate outliers, and the Slope function can be used to obtain the second coefficient.

[0057] Next, based on the first change relationship and the second coefficient, the changes in fiber length and attenuation are combined to obtain multiple optional combinations. These optional combinations are: combinations of fiber length and attenuation changes that maintain a constant gain slope when both changes in fiber length and attenuation occur simultaneously; that is, combinations of fiber length and attenuation changes are derived by incorporating the first change relationship. In each combination (e.g., adding fiber increases attenuation change, removing fiber decreases attenuation change), both fiber length and attenuation changes simultaneously to ensure that the gain slope remains unchanged.

[0058] Then, the relationship between different combinations of relationships and the gain spectrum is determined: the wavelength and gain change corresponding to the second processing curve are obtained, and the slope of the third relationship curve between the obtained wavelength and the corresponding gain change is determined as the third coefficient; according to the third coefficient of each wavelength, the second change relationship is obtained; wherein, the second change relationship is: the gain change of each wavelength corresponding to the change of each unit fiber length; in one embodiment, the unit of fiber length can be centimeters. Under the premise of changing the attenuation change while ensuring that the gain slope does not change, the effect of changing the fiber length on each wavelength is very different, especially the difference in the effect on wavelengths in the middle and tail of the relationship curve is significant; therefore, based on the second processing curve obtained after excluding outliers, the slope of the gain change of each wavelength needs to be calculated to obtain the coefficient corresponding to each wavelength. In one embodiment, by connecting the discrete data points of the coefficients obtained for each wavelength, the "gain change of each wavelength corresponding to the addition or subtraction of 100 cm of erbium fiber" can be obtained, that is, the relationship between different combinations of fiber length attenuation change and the gain spectrum. An Excel template can be created according to the second change relationship to deduce how the gain spectrum changes after changing the attenuation change.

[0059] Based on the first and second variation relationships, a curve showing the relationship between fiber length and attenuation change corresponding to the original spectral shape is obtained. In one embodiment, an Excel template created based on the first and second variation relationships is used to deduce the future test spectral shape corresponding to the attenuation change and fiber length change of the original spectral shape of the EDFA product whose gain fluctuation needs to be optimized. Performance indicators are calculated based on the proposed new spectral shape, and its compliance is determined. For example, according to the Excel template of the first variation relationship, an attenuation change of 3.2 dB is added to obtain gain spectrum 1. Based on gain spectrum 1, combined with the change in each characteristic wavelength in the Excel template of the second variation relationship, a gain spectrum with the scheme of "adding an attenuation change of 3.2 dB and adding a fiber length change of 1.5 cm" is obtained. Performance indicators are then obtained and their compliance is determined.

[0060] In one embodiment, during the above test process, fiber addition and subtraction operations are performed, the attenuation change is adjusted, and the front pump value and rear pump value of the test station are kept constant; multiple tests are performed to generate a curve showing the relationship between fiber length and attenuation change.

[0061] To ensure that other conditions do not affect the experiment, at least the following steps must be completed first: fix one light source, ensure that the flatness of the light source is less than 0.2 dB, and ensure the stability of the light source; fix one test station to ensure the repeatability of product testing and the accuracy of data; the selected product should have loose fiber winding and no visible abnormalities.

[0062] After adding or removing fibers from the product, testing should be conducted at the same workstation. During testing, the pre-pump value should remain constant, while the post-pump value should be adjusted according to actual conditions to ensure consistent output power; output power refers to the optical signal power amplified by the EDFA. During testing, the attenuation variation of the product should be adjusted according to the actual scanning spectrum to ensure that the gain slope in the two test results is as consistent as possible.

[0063] Repeat the above tests until the correlation between fiber length and attenuation change is calculated. For example... Figure 2 The solid line in the figure shows a specific example of a relationship curve; where, Figure 2 The dashed line in the diagram represents the regression line that the relationship curve approximates. Here, the front pump value of the test module (not the test station) is kept constant, while the rear pump value needs to be varied according to the output power (e.g., increasing the rear pump when the output power is low). The light source of the test station remains constant, and the photodetector calibration value of the module remains constant. Multiple tests are performed. It is important to note that the L++ band product must maintain stable product status for each test. In one embodiment, for L++ products, a 1 dB attenuation change typically corresponds to a fiber length of 1.5 to 2 meters; the actual corresponding value depends on the actual optical path and module. In an optional embodiment, if the attenuation change is more or less than expected, it may be due to changes in insertion loss during fiber addition / reduction processes; this insertion loss typically includes fiber winding loss and fiber addition / reduction splice insertion loss. Figure 2 The data corresponding to the small and medium squares indicates that the product abnormality may be due to welding abnormalities during fiber addition or reduction, hence the introduction of 0.4 dB loss.

[0064] To explain the process of adding or removing fibers, such as Figure 3 As shown, maintaining the demand slope unchanged while performing fiber addition / reduction operations includes: Step 101: Determine the gain variation of different gain spectra at different wavelengths according to the relationship curve.

[0065] Based on the test curves, a graph showing the change in spectral shape before and after the product is created. This allows analysis of the corresponding characteristic wavelength ranges for adding fiber to the module, increasing attenuation, or removing fiber, decreasing attenuation. Note that due to potential individual module differences, experiments should be conducted on at least 10 EDFA optical amplifier modules, and the intersection of the corresponding characteristic wavelength ranges for each module should be selected as the characteristic point. After completion, the conclusions must be verified on at least 5 EDFA optical amplifier modules. The middle wavelength of the spectral shape change characteristics of L++ products is typically around 1608 nm, and the tail wavelength is typically after 1620 nm; the actual corresponding wavelengths depend on the actual optical path and module. In an optional embodiment, if the changes are inconsistent with expectations, first check whether there are changes in the product's input light and gain, whether the feedforward pump current has changed, and whether the attenuation change is consistent with expectations.

[0066] like Figure 4 The diagram shows a specific example of the gain change before and after adding 118 cm of fiber. The horizontal axis represents the wavelength, and the vertical axis represents the gain change at different wavelengths before and after the fiber length change.

[0067] Step 102: Select at least two characteristic bands from all the gain changes.

[0068] Figure 4 The curve is composed of multiple feature points corresponding to different wavelengths, and each feature point represents a different gain change; at least two feature bands with different wavelength ranges are selected from these feature points. Figure 4 Three characteristic bands were selected, and the data for each characteristic band are shown in the corresponding dashed boxes. The original spectrum is light from 1575 nm to 1625 nm, and the three selected characteristic bands are: 1575 nm to 1590 nm, 1590 nm to 1610 nm, and 1610 nm to 1625 nm.

[0069] This invention enables precise control of the gain of each characteristic band by adjusting the length of the erbium-doped fiber corresponding to each characteristic band (i.e., by adding or removing fibers separately). For example, increasing the fiber length of characteristic bands 1 and 3 improves their gain, while decreasing the fiber length of characteristic band 2 reduces its gain, thereby optimizing the overall gain fluctuation and minimizing the gain difference between sub-bands. By adjusting the fiber length in segments, the unevenness of the gain spectrum can be specifically corrected to meet the user's specific requirements for gain fluctuation (e.g., less than 1.5 dB).

[0070] Step 103: Determine the spectral shape coefficients of the characteristic band.

[0071] In one optional embodiment, after completing the above steps, at least one set of data can be obtained, including at least: the increase or decrease in fiber length (i.e., the change), the change in attenuation, and the change in average gain at the characteristic wavelength. The change in attenuation and the change in average gain at the characteristic wavelength are both strongly correlated with the increase or decrease in fiber length. First, correlation analysis is performed on these data; in one embodiment, correlation analysis can be performed using the RSQ function. The RSQ function is a statistical function used to calculate the square of the Pearson product moment correlation coefficient (i.e., the coefficient of determination) between two sets of data, with a value ranging from 0 to 1, used to measure the strength of the linear relationship between variables. For example, a specific example of test data before and after fiber addition / reduction is... Figure 5 As shown.

[0072] Wherein, "VOA" refers to the attenuation change of the optical signal after passing through the VOA; "Eigenvalue 1" refers to the gain of characteristic band 1, and so on; "▲VOA" refers to the difference in attenuation change before and after fiber addition or subtraction, "▲Eigenvalue 1" refers to the gain change of characteristic band 1 before and after fiber addition or subtraction, and so on. "Addition / Subtraction Length" refers to the change in fiber length corresponding to the characteristic band. The gain change is the average gain change of the corresponding characteristic band under the corresponding fiber length change.

[0073] Using the columns “▲VOA”, “▲Feature Value 1”, “▲Feature Value 2”, and “▲Feature Value 3” as X variables and the column “Addition / Subtraction Length” as Y variable, the RSQ function is used to calculate the correlation coefficient between the X and Y variables, and the RSQ value is obtained.

[0074] The method for determining RSQ is as follows: an RSQ value of 0 to 0.2 indicates that the two sets of data are completely uncorrelated; an RSQ value of 0.2 to 0.4 indicates that the two sets of data are weakly correlated; an RSQ value of 0.4 to 0.6 indicates that the two sets of data are correlated; an RSQ value above 0.8 indicates that the two sets of data are strongly correlated; and an RSQ value above 0.95 indicates that the two sets of data are completely linearly correlated.

[0075] If the calculated RSQ value is greater than 0.95, it indicates that the variation in the characteristic points within the characteristic band and the fiber length exhibit a completely linear relationship, like a linear equation in one variable. Only a few characteristic points differ between multiple characteristic bands, but this does not affect the linear relationship; for example, ... Figure 4 As shown, for the feature points between feature band 1 and feature band 2, and for the feature points between feature band 2 and feature band 3, the corresponding gain changes are all less than 0.1. Since repeated testing may also introduce a gain error of 0.1, it is considered as a test error, and these feature points are not selected.

[0076] Since the changes in attenuation and average gain at the characteristic wavelength should also be zero when the fiber length change is zero, the slope can be directly calculated as the corresponding spectral shape coefficient for the fiber length and characteristic point. The specific process for calculating the spectral shape coefficient will be explained below.

[0077] If the calculated RSQ value is less than 0.95, step 102 should be repeated to check if the selection of characteristic bands is incorrect. In step 102, at least two characteristic bands must be selected, and in step 103, at least two sets of corresponding relationships must also be selected.

[0078] It should be noted that for a specific type of optical product or system, its core characteristics, such as absorption coefficient and optical path structure, are fixed during the design and manufacturing process. The optical path structure encompasses not only the traditional layout of optical components but also key components such as pump sources (e.g., 980nm laser pumping), which together form the basis for stable system operation. Therefore, each type of product possesses its unique characteristic wavelength and spectral shape coefficient, which are important identifiers distinguishing different products. Although there may be slight differences in characteristic wavelengths and spectral shape coefficients between different products, these differences mainly stem from variations in the gain spectrum, absorption coefficient, and overall optical path structure design of the erbium-doped fiber, rather than fundamental differences in the product's essential properties.

[0079] Step 104: Perform fiber addition / reduction operations based on the required slope and the spectral value coefficient.

[0080] The meaning of the spectral shape coefficient is as follows: For example, when the spectral shape coefficient is +165.17, every increase of 165.17 cm in fiber length results in a gain change of one decibel, all other things being equal; when the spectral shape coefficient is -1596.82, every decrease of 1596.82 cm in EDFA results in a gain change of one decibel, all other things being equal.

[0081] The process will be explained below.

[0082] In one embodiment, determining the spectral shape coefficients of the characteristic band includes: The slope of the linear relationship between the gain change and fiber length change in the characteristic band is determined as the spectral shape coefficient.

[0083] Where the change in gain is variable X and the change in fiber length is variable Y, the slope of the linear relationship between the change in gain and the change in fiber length is X / Y. In one embodiment, a linear regression method can be used to fit the relationship between these two sets of data, and the resulting linear regression relationship is used as the slope of the linear relationship. In an optional embodiment, the SLOPE function can be used to calculate the slope of the linear regression line using the least squares method to obtain the slope of the linear relationship; for example, the SLOPE function is used to process... Figure 5 By combining the data in the "▲Eigenvalue 1" column with the data in the "Add / Subtract Length" column, the slope of the linear relationship for characteristic band 1 (i.e., the 1578 nm to 1585 nm band) is obtained, and this linear relationship slope is used as the spectral shape coefficient of characteristic band 1. Since the relationship obtained through measurement in this embodiment will be a curve, for example... Figure 6The actual curve for the wavelength range from a to b and the desired curve for a flat gain are shown; the desired curve is a linear trend line; therefore, when obtaining the desired curve from the actual curve by adding or subtracting fibers, the intermediate characteristic band (e.g., Figure 6 When in “characteristic band 2”, the shortwave portion (e.g., Figure 6 "Characteristic band 1" and long-wavelength portion (e.g., Figure 6 The "characteristic band 3" will also be affected; and if the discrete data points of the average gain of the shortwave portion and the discrete data points of the average gain of the longwave portion can be connected into a line (for example, Figure 6 If the curve required in the middle characteristic band is such that the discrete data points of the average gain in the middle characteristic band are closer to the line connecting them, then the gain fluctuation is smaller. Following this idea, to uniformly measure the length of the fiber addition and reduction, the parameter x is set as x = G(short) + [G(long) - G(short)] / [ (long)- (Short)]×[ (middle)- [(Short)], it can be found that the change in x is also linearly related to the fiber length; where the parameter x means: the offset between the current gain spectrum (i.e., the spectrum shape actually measured) and the spectrum shape under ideal conditions (i.e., the most ideal case is to perfectly fit the trend line); G (short) refers to the average gain of the short-wavelength part, and G (long) refers to the average gain of the long-wavelength part. (Short) refers to the wavelength in the short-wave portion. (in Chinese) refers to the wavelength of the intermediate characteristic band. (Long) refers to the wavelength of the long-wavelength portion. Because the gain change varies with different wavelengths, the gain of each wavelength is calculated according to the data in the first and second change relationships obtained in step 10 (e.g., the corresponding Excel template). This yields the optimal spectral shape solution for the product, calculated as follows: [x(current) - x(expected)] × spectral shape coefficient; x(current) represents the parameter x calculated according to the actual curve, and x(expected) represents the parameter x calculated according to the desired curve. The calculation method for this part of the spectral shape coefficient is consistent with the steps above and will not be repeated here.

[0084] This invention only requires calculating the fiber addition / reduction length and performing fiber addition / reduction operations according to the fiber addition / reduction length to change the original spectrum and optimize gain fluctuations, such as... Figure 7 As shown, the fiber addition / reduction operation based on the demand slope and the spectral shape coefficient includes: Step 201: Generate the fiber addition / reduction length according to the required slope and the spectrum value coefficient.

[0085] In one embodiment, the gain spectrum of the next test is calculated based on the calculated fiber length, and the performance index is deduced to determine whether it is qualified.

[0086] Step 202: Perform fiber addition / reduction operations according to the stated fiber addition / reduction length.

[0087] In one optional embodiment, the fiber addition / reduction values ​​can first be estimated using existing techniques, employing test values ​​of the gain slope of the EDFA product before fiber reduction and VOA settings. Then, based on the method of this embodiment, the optimal combination of fiber length change and attenuation change is calculated using the original spectrum. Finally, feasible fiber length change and attenuation change values ​​are combined from these two steps; one way to combine fiber length change and attenuation change is to take the average. Specifically, as... Figure 8 As shown, generating the fiber addition / reduction length according to the required slope and the spectral shape coefficient includes: Step 301: Obtain the average actual gain of each of the characteristic bands.

[0088] The actual average gain refers to the average gain of each characteristic point within a characteristic band, as measured by actual testing; for example, the average gain of each characteristic point between 1578 nm and 1585.5 nm in the characteristic band.

[0089] Step 302: Based on the required slope and the total reference gain, process the average of each actual gain to obtain the fiber addition / reduction length.

[0090] Specifically, such as Figure 9 As shown, the process of processing the average of each actual gain based on the required slope and the total reference gain to obtain the fiber addition / reduction length includes: Step 401: Determine the first difference between the average actual gain and the total reference gain under ideal conditions.

[0091] The total reference gain is the average of the overall product gain, given by the user; for example, the total reference gain is 22 dB. Ideally, this means the gain slope is 0.

[0092] For example, the expression for the difference between the actual average gain of the characteristic band 1578 nm to 1585.5 nm and the total reference gain is: T1 = AVERAGE(Gain(1578~1585.5)) - AVERAGE(Gain(total)); where AVERAGE(Gain(1578~1585.5)) represents the actual average gain of the characteristic band 1578 nm to 1585.5 nm, and AVERAGE(Gain(total)) represents the total reference gain. Setting this difference expression T1 = 0, we obtain the first difference of the characteristic band 1578 nm to 1585.5 nm.

[0093] In this embodiment of the invention, a first difference is determined for at least two selected characteristic bands for subsequent calculations. Similarly, the expression for the difference between the actual average gain of the characteristic bands 1595.5 nm to 1615 nm and the total reference gain is: T2 = AVERAGE(Gain (1595.5~1615)) - AVERAGE(Gain (total)); where AVERAGE(Gain (1578~1585.5)) represents the actual average gain of the characteristic bands 1595.5 nm to 1615 nm. Setting this difference expression T2 = 0, the first difference between the characteristic bands 1595.5 nm and 1615 nm is obtained. The expression for the difference between the actual average gain in the characteristic band from 1623.5 nm to 1626.4 nm and the total reference gain is: T3 = AVERAGE(Gain(1623.5~1626.4)) - AVERAGE(Gain(total)); where AVERAGE(Gain(1623.5~1626.4)) represents the actual average gain in the characteristic band from 1623.5 nm to 1626.4 nm. Setting this difference expression T2 = 0, we obtain the first difference in the characteristic band from 1623.5 nm to 1626.4 nm.

[0094] In this embodiment of the invention, the deviation between the actual average gain of each characteristic band and the overall reference average is determined by calculating the first difference.

[0095] Step 402: Based on the required slope and the first difference, determine the first deviation between the average actual gain and the total reference gain under ideal conditions.

[0096] Ideally, the gain curve of each feature point should be a line segment. In this embodiment of the invention, the deviation is calculated to connect the line segments corresponding to each feature point.

[0097] For example, when the demand slope is -1, b = T1 + (T3 - T1) / (1625 - 1582) × (1605 - 1582); where, for ease of calculation, 1625 is an approximation of 1626.4. Here, b represents the deviation between the actual mean gain of this characteristic band and the total reference gain under ideal conditions at the demand slope. b is the gain deviation corresponding to T2 under ideal conditions, which is the line segment corresponding to the demand slope, minimizing the corresponding gain fluctuation. Since the essence of this deviation value is calculating the slope, T3 - T1 is used.

[0098] Step 403: Determine the second difference between the first difference and the first deviation, and determine the product of the second difference and the spectral shape coefficient as the first length.

[0099] For example, L1 = (T2 - b) × (-700), where -700 is the spectral shape coefficient.

[0100] Step 404: Take the average of all the first lengths to obtain the fiber addition / reduction lengths.

[0101] Furthermore, for EDFA, because the amplification efficiency of erbium ions at the last characteristic point in the characteristic band (e.g., the characteristic point at wavelength 1626.4 nm) is particularly low, it needs to be calculated separately. Otherwise, it will lead to a large deviation in the gain fluctuation index at that characteristic point. Specifically, based on the above steps, such as Figure 10 As shown, the step of processing the average of each actual gain based on the required slope and the total reference gain to obtain the fiber addition / reduction length further includes: Step 501: Obtain the actual gain value of the last feature point from the last feature band.

[0102] Step 502: Determine the third difference between the actual gain value under ideal conditions and the total reference gain.

[0103] The expression for the difference between the actual mean gain of the feature point at wavelength 1626.4 and the total reference gain is: T4 = Gain(1626.4) - AVERAGE(Gain(total)); where Gain(1626.4) represents the actual mean gain of the feature point at wavelength 1626.4. Setting this difference expression T2 = 0, we obtain the third difference for the feature point at wavelength 1626.4.

[0104] Step 503: Determine the second deviation between the actual gain value and the total reference gain under ideal conditions, based on the required slope and the third difference.

[0105] Similarly, the characteristic band is calculated as follows: d = T1 + (T3 - T1) / (1625 - 1582) × (1626 - 1582); where, for ease of calculation, 1582 is the intermediate value between 1578 and 1585.5. d is the first difference in gain corresponding to T4 under ideal conditions.

[0106] Step 504: Determine the fourth difference between the third difference and the second deviation, and determine the second length by multiplying the fourth difference with the spectral coefficient corresponding to the feature point.

[0107] For example, L2 = -(T4-d) × (-319.12), where -319.12 is the spectral shape coefficient.

[0108] Step 505: Take the average of all the first lengths and the second lengths to obtain the fiber addition / reduction lengths.

[0109] For example, the length of fiber addition / reduction = (L1 + L2) / 2.

[0110] It should be noted that the relationship between fiber length and attenuation change determined in the embodiments of this invention has a wide range of applications: it is applicable to any scenario where the EDFA band is amplified. There are no limitations on the optical path structure and the type of EDFA; it is applicable to C-band, C-extended band, L-band, and L-extended band, and the method is completely consistent. The embodiments of this invention only use the L++ band as an example and are not intended to limit the applicable band of this invention. Existing technologies generally use absorption coefficients to distinguish the types of erbium-doped fibers, and both low-absorption-coefficient and high-absorption-coefficient systems are applicable. Since the optical path structure remains unchanged in actual production for each product, and a specific type of erbium-doped fiber is used, under these specific circumstances, the production quantity of all products in the same batch has no impact on the spectral shape coefficient, characteristic band, and characteristic points. Each product has corresponding spectral shape coefficients, characteristic bands, and characteristic points. Different products have different characteristic wavelengths and spectral shape coefficients, which may vary slightly, but not significantly. The differences stem from two factors: firstly, the absorption coefficients of different types of erbium-doped fibers vary, and secondly, the influence of the optical path structure.

[0111] It is worth noting that insertion loss is uncontrollable in existing technologies. However, the gain fluctuation optimization method for the erbium-doped fiber amplifier (EDFA) according to this invention addresses this issue. In an EDFA, the gain slope is determined by three core factors: first, insertion loss—the greater the insertion loss, the more negative the gain slope, and the two are negatively correlated; second, fiber length—the longer the fiber, the more positive the gain slope, and the two are positively correlated; and third, pump current—the greater the pump current, the more negative the gain slope, and the two are also negatively correlated. In actual mass production scenarios, users typically have specific requirements for the gain slope (e.g., -1 dB, -2 dB, or 0 dB), which must be strictly met. While the insertion loss of the module itself is uncontrollable, most modules have a built-in VOA (Variable Atmosphere Output), which can be manually adjusted to increase insertion loss; however, the VOA can only increase attenuation, not decrease it. The adjustment ratio of gain slope to attenuation change typically fluctuates between 0.8:1 and 1:1, while the ratio of fiber length to gain slope varies depending on the product type. For example, it is approximately 170:1 to 180:1 for L++ band products and approximately 50:1 to 60:1 for C++ band products. This invention first adjusts the fiber length to meet gain fluctuation requirements, and then uses VOA to compensate for the impact of fiber length adjustment on the gain slope, thereby simultaneously achieving the target for both gain fluctuation and slope indicators. Because this invention uses formulas to determine the fiber length for batch production, it can optimize the mass production stage of the model to a certain extent, making the insertion loss between modules controllable during manufacturing.

[0112] When using the method of the present invention, a specific example of an actual production step is as follows: (1) routine testing, and proceed to the next step when the performance indicators are not qualified; (2) adjust VOA to make Tilt reach the target slope and test other performance indicators; (3) calculate the optimal fiber length according to Tilt and GR respectively; (4) use the optimal fiber length to deduce the performance indicators after adding or removing fibers; (5) if the deduction is qualified, then do the adding or removing of fibers; (6) before the actual adding or removing of fibers, the optimal fiber length will be disassembled according to the optical path diagram and noise figure indicators.

[0113] Example 2: like Figure 11 The diagram shown is a schematic representation of an architecture for a gain fluctuation optimization device for an erbium-doped fiber amplifier according to an embodiment of the present invention. The gain fluctuation optimization device for the erbium-doped fiber amplifier in this embodiment includes one or more processors 21 and a memory 22. Figure 11 Take a processor 21 as an example.

[0114] Processor 21 and memory 22 can be connected via a bus or other means. Figure 11 Taking the example of a connection between China and Israel via a bus.

[0115] The memory 22, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs and non-volatile computer-executable programs, such as the gain fluctuation optimization method for the erbium-doped fiber amplifier in this embodiment. The processor 21 executes the gain fluctuation optimization method for the erbium-doped fiber amplifier by running the non-volatile software programs and instructions stored in the memory 22.

[0116] Memory 22 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, memory 22 may optionally include memory remotely located relative to processor 21, which can be connected to processor 21 via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0117] The program instructions / modules are stored in the memory 22. When executed by one or more processors 21, they execute the gain fluctuation optimization method for erbium-doped fiber amplifiers in the above embodiments, for example, executing each step of the gain fluctuation optimization method for erbium-doped fiber amplifiers in the embodiments of the present invention described above.

[0118] This invention also provides a non-volatile computer storage medium storing computer-executable instructions that are executed by one or more processors, for example... Figure 11A processor 21 enables one or more of the processors to execute the gain fluctuation optimization method for erbium-doped fiber amplifiers in specific embodiments of the present invention, for example, to execute the various steps of the gain fluctuation optimization method for erbium-doped fiber amplifiers described above in the embodiments of the present invention; it can also implement... Figure 11 The various modules and units shown; or the gain fluctuation optimization method for erbium-doped fiber amplifiers described in the specific embodiments of the present invention, for example, executing the various steps of the gain fluctuation optimization method for erbium-doped fiber amplifiers described above in the embodiments of the present invention; can also be implemented. Figure 11 The aforementioned modules and units.

[0119] It is worth noting that the information interaction and execution process between the modules and units in the above-mentioned device and system are based on the same concept as the processing method embodiment of the present invention. For details, please refer to the description in the method embodiment of the present invention, and will not be repeated here.

[0120] Those skilled in the art will understand that all or part of the steps in the various methods of the embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: read-only memory (ROM), random access memory (RAM), magnetic disk or optical disk, etc.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the gain fluctuation of an erbium-doped fiber amplifier, characterized in that, include: Keeping the demand slope constant, determine the relationship curve between fiber length and attenuation change corresponding to the original spectrum shape; While keeping the demand slope constant, fiber addition and subtraction operations are performed to make the relationship curve approximate a regression line, thus obtaining the target spectrum.

2. The gain fluctuation optimization method for erbium-doped fiber amplifiers according to claim 1, characterized in that, The method includes: Based on the aforementioned relationship curve, determine the gain variation of different gain spectra at different wavelengths; Select at least two characteristic bands from all the gain variations; Determine the spectral shape coefficients of the characteristic band; Fiber addition and subtraction operations are performed based on the required slope and the spectral value coefficient.

3. The gain fluctuation optimization method for erbium-doped fiber amplifiers according to claim 2, characterized in that, The method includes: The slope of the linear relationship between the gain change and fiber length change in the characteristic band is determined as the spectral shape coefficient.

4. The gain fluctuation optimization method for erbium-doped fiber amplifiers according to claim 2, characterized in that, The method includes: The fiber length is generated according to the required slope and the spectral shape coefficient; Perform the fiber addition / reduction operation according to the stated fiber addition / reduction length.

5. The gain fluctuation optimization method for erbium-doped fiber amplifiers according to claim 4, characterized in that, The method includes: Obtain the average actual gain of each of the characteristic bands; Based on the required slope and the total reference gain, the average of each actual gain is processed to obtain the fiber addition / reduction length.

6. The gain fluctuation optimization method for erbium-doped fiber amplifiers according to claim 5, characterized in that, The method includes: Determine a first difference between the average actual gain under ideal conditions and the total reference gain; Based on the required slope and the first difference, determine the first deviation between the average actual gain and the total reference gain under ideal conditions; Determine a second difference between the first difference and the first deviation, and determine the product of the second difference and the spectral shape coefficient as the first length; The average of all the first lengths is used to obtain the fiber addition and subtraction lengths.

7. The gain fluctuation optimization method for erbium-doped fiber amplifiers according to claim 6, characterized in that, The method further includes: Obtain the actual gain value of the last feature point from the last of the aforementioned feature bands; Determine a third difference between the actual gain value and the total reference gain under ideal conditions; Based on the demand slope and the third difference, determine the second deviation between the actual gain value and the total reference gain under ideal conditions; Determine a fourth difference between the third difference and the second deviation, and determine the product of the fourth difference and the spectral shape coefficient corresponding to the feature point as the second length; The average of all the first lengths and the second lengths is used to obtain the fiber addition and subtraction lengths.

8. The method for optimizing the gain fluctuation of an erbium-doped fiber amplifier according to any one of claims 1-7, characterized in that, The method includes: A first relationship curve is determined between the attenuation change and the first gain slope. Outliers in the first relationship curve are eliminated to obtain a first processing curve. The wavelength and gain change corresponding to the first processing curve are obtained, and the slope of the second relationship curve between the obtained wavelength and the corresponding gain change is determined as a first coefficient. According to the first coefficient of each wavelength, a first change relationship is obtained. The first change relationship is: the gain change of each wavelength corresponding to the change in gain slope per unit caused by the change in attenuation. A second relationship curve between fiber length and second gain slope is determined, outliers in the second relationship curve are eliminated, and a second processing curve is obtained; the slope of the second processing curve is determined as the second coefficient. Based on the first change relationship and the second coefficient, the fiber length change and attenuation change are combined to obtain a variety of optional combinations; wherein, the optional combination is: a combination of fiber length change and attenuation change that keeps the gain slope unchanged when the fiber length change and attenuation change ... Obtain the wavelength and gain change corresponding to the second processing curve, and determine the slope of the third relationship curve between the obtained wavelength and the corresponding gain change as the third coefficient; according to the third coefficient of each wavelength, obtain the second change relationship; wherein, the second change relationship is: the gain change of each wavelength corresponding to the change of each unit fiber length. Based on the first and second variation relationships, the relationship curve between fiber length and attenuation change corresponding to the original spectrum shape is obtained.

9. A gain fluctuation optimization device for an erbium-doped fiber amplifier, characterized in that, The gain fluctuation optimization device for the erbium-doped fiber amplifier includes at least one processor and a memory, which are connected via a data bus. The memory stores instructions that can be executed by the at least one processor. After being executed by the processor, the instructions are used to implement the gain fluctuation optimization method for the erbium-doped fiber amplifier according to any one of claims 1-8.

10. A non-volatile computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions, which are executed by one or more processors to perform the gain fluctuation optimization method for the erbium-doped fiber amplifier as described in any one of claims 1-8.

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