SFP + type packaging optical module key failure mode analysis method
Through the analysis method of key failure mode of the SFP+ type packaged optical module, combined with FTA, RPN and relationship matrix methods, the key failure mode of the optical module is identified, which solves the problem of complexity of the analysis of multiple failure modes of the optical module, and improves the analysis efficiency and accuracy .
Patent Information
- Application Number
- CN202411223921.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2024-12-13
AI Technical Summary
There are many failure modes in optical modules in optical communication systems, and the working conditions are complex, which leads to high complexity in reliability research and makes it difficult to identify key failure modes.
The key failure mode analysis method of SFP+ type packaged optical modules is used, combined with FTA, RPN and relationship matrix methods, and the failure mode of the optical module is qualitatively analyzed and quantitatively evaluated to identify the key failure modes and reduce the complexity of the research.
Effectively analyze the possible failure modes and their hazards of optical modules, identify key failure modes, improve the efficiency and accuracy of the reliability analysis of optical modules, and reduce the complexity of research.
Smart Images
Figure CN119129406A_ABST
Abstract
Description
(I) Technical field
[0001] The invention provides a key failure mode analysis method of an SFP+ type packaged optical module, which relates to a failure mode analysis method of an optical module and belongs to the field of electronic component reliability. (II) Background technology
[0002] Fiber-optic communication technology is widely used in aerospace, electronic and power fields. Optical modules are the core units of the physical layer of optical communication systems. Their main function is to perform optical-to-electrical / electrical-to-optical conversion. They account for a high proportion of the system cost. Millions of optical modules can exist simultaneously in the optical network of a large data center.
[0003] The reliability of optical modules is the basis of the reliability of optical communication systems. The degradation or failure of any optical module in the optical network may seriously affect the health of the system. With the development of the Internet of Things and cloud computing, the traffic of optical communication networks has grown rapidly, and the demand for transmission capacity, stability and security has continued to increase, and the reliability requirements for optical modules have also become higher and higher.
[0004] SFP+ (Small Form-factor Pluggable+) optical modules are small hot-pluggable optical modules that support a maximum transmission rate of 10Gbps. This type of optical module has lower power consumption, smaller size, and stronger adaptability in the field of high-density ports. It is still widely used in optical networks today and is the most used product among 10G optical modules.
[0005] Failure mode refers to the manifestation of product failure, including electrical, optical, thermal, magnetic and other manifestations. Analyzing the failure mode of optical modules is helpful to further analyze the failure mechanism and propose improvement measures. However, there are many types of failure modes of optical modules, and there are different environmental stresses under working conditions, which makes the conditions that need to be considered when conducting reliability research on optical modules complicated. Therefore, it is necessary to study a method for analyzing the key failure modes of optical modules, analyze multiple failure modes of optical modules, identify key failure modes, facilitate further research on key failure modes, and reduce the complexity of research.
[0006] The FTA (Fault Tree Analysis) method is widely used in failure analysis due to its intuitiveness and strong logic, and can be applied to both qualitative and quantitative analysis. The FTA method is used to analyze the hardware, software, environment, and human factors that may cause the failure of the optical module, and further obtain the possible failure modes of the optical module. The RPN (Risk Priority Number) method can quantitatively evaluate the failure mode, and the relationship matrix can jointly analyze the failure mode and environmental stress of the optical module.
[0007] The present invention proposes a key failure mode analysis method for an SFP+ packaged optical module, which can obtain possible failure modes of the optical module, quantitatively evaluate the harmfulness of each failure mode, and analyze the key failure modes in combination with environmental stress, thereby reducing the complexity of the research and providing a methodological reference for failure mode analysis of the optical module. (III) Summary of the invention
[0008] 1. Purpose: The purpose of the present invention is to provide a method for analyzing the key failure modes of SFP+ packaged optical modules, analyze the possible failure modes of optical modules, and analyze the key failure modes thereof in combination with environmental stress, thereby reducing the complexity of the research and providing a methodological reference for the failure mode analysis of optical modules.
[0009] 2. Technical solution:
[0010] A method for analyzing the key failure modes of SFP+ packaged optical modules. The specific process is as follows: Figure 1 As shown, the following steps are included:
[0011] Step 1: Analyze the internal structure and working principle of the optical module, specifically:
[0012] Use non-destructive testing and destructive physical analysis methods, such as X-ray scanning, unpacking visual inspection, etc., combined with product specifications, to analyze the internal structure and working principle of the optical module.
[0013] Step 2: Qualitatively analyze the failure mode of the optical module based on the FTA method, specifically:
[0014] The failure of optical modules can be divided into two types: optoelectronic device failure and circuit failure. Optoelectronic devices and circuits work together, and circuit failure will be reflected in optoelectronic devices, directly affecting the working state of optoelectronic devices. For the core optoelectronic devices in optical modules, such as lasers and photodiodes, a fault tree model is established based on the FTA method to analyze the failure mode.
[0015] Step 3: Calculate the risk priority number of each failure mode according to the RPN method, specifically:
[0016] The risk priority number of a failure mode is defined as the product of the severity level S and the probability level O:
[0017] RPN=SXO
[0018] The severity S of each failure mode is defined with reference to the severity rating (ESR), and is divided into four levels, I to IV, according to the different degrees of impact of the failure mode on the device, corresponding to scores of 4 to 1, as shown in the following table.
[0019] Severity Severity Definition S-score Ⅰ Disaster, once it occurs, the device will lose all output parameters in a short time 4 Ⅱ Fatal, causing significant degradation of key parameters 3 Ⅲ Moderate, causing moderate damage to the device, with a certain delay effect on the device 2 Ⅳ Mild, not enough to affect the stability of the device's main output parameters 1
[0020] The occurrence probability level O is divided into five levels from A to E, corresponding to scores 5 to 1, as shown in the following table.
[0021] Probability level definition O score A Frequent occurrence, high probability 5 B Sometimes occurs, medium probability 4 C Occurs occasionally, not often 3 D Rarely occurs, unlikely to occur 2 E Very rare, almost 0 1
[0022] Step 4: Use the relationship matrix to analyze the key failure modes, specifically:
[0023] According to the risk priority number, the criticality level of the failure mode can be divided into four levels, and the criticality level decreases from i to iv, such as Figure 2 shown.
[0024] The prevalence of environmental stress is divided into four levels, increasing from 1 to 4, namely: (1) rarely exists; (2) occasionally exists; (3) often exists; (4) always exists.
[0025] The criticality level of each failure mode and the universality level of environmental stress are used as the input of the relationship matrix to analyze the threat of each failure mode. The most threatening failure mode is the key failure mode. The relationship matrix is in the form of Figure 3 shown.
[0026] 3. Advantages and effects:
[0027] This method proposes a method for analyzing key failure modes of SFP+ packaged optical modules. The advantages of this invention are:
[0028] (1) This method adopts the FTA method to analyze the hardware, software, environment and human factors that may cause the failure of the optical module, and can intuitively and clearly obtain the possible failure modes of the optical module.
[0029] (2) This method associates failure modes with environmental stress through a relationship matrix, which can effectively analyze the key failure modes of optical modules, reduce the complexity of research, and provide a methodological reference for failure mode analysis of optical modules. (IV) Description of the drawings
[0030] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.
[0031] Figure 1 It is a flow chart of the method of the present invention.
[0032] Figure 2 It is a diagram of failure mode criticality level.
[0033] Figure 3 It is a schematic diagram of the relationship between failure mode and environmental stress in matrix form.
[0034] Figure 4 It is the X-ray scan result of the instance light module.
[0035] Figure 5 This is the unpacking result of the example optical module.
[0036] Figure 6 It is a schematic diagram of the internal structure of the light emitting part.
[0037] Figure 7 It is a schematic diagram of the internal structure of the light receiving part.
[0038] Figure 8 It is the fault tree model of the optical module laser.
[0039] Fig. 9 It is the fault tree model of the photodiode of the optical module.
[0040] Fig.10 This is a diagram of the threat classification of failure modes.
[0041] Fig.11 This is the example optical module relationship matrix result diagram. (V) Specific implementation methods
[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand and implement the present invention, but the examples given are not intended to limit the present invention.
[0043] The present invention provides a method for analyzing key failure modes of an SFP+ packaged optical module. The specific embodiment selects an AXS15-192-40 SFP+ packaged optical module. The specific implementation process of the method is as follows: Figure 1 As shown, the specific implementation steps are as follows:
[0044] Step 1: Analyze the internal structure and working principle of the optical module.
[0045] Use non-destructive testing and destructive physical analysis methods, such as X-ray scanning, unpacking visual inspection, etc., combined with product specifications, to analyze the internal structure and working principle of the optical module. This example selects the AXS15-192-40 SFP+ packaged optical module, performs X-ray scanning and unpacking on the optical module, and the results are as follows: Figure 4 and Figure 5 As shown. By comparing the results, the laser, photodetector and circuit structure inside the optical module are clearly visible. The optical module can be divided into the light transmitting part and the light receiving part for further analysis.
[0046] (1) Light emitting part
[0047] The core of the optical transmission part is the laser. The laser of this optical module is EML (Electroabsorption Modulated Laser), which is monolithically integrated with DFB (Distributed Feedback) laser and EA (Electroabsorption) modulator. The circuit parts other than the laser include the equalizing circuit, automatic power control circuit APC (Automatic Power Control), automatic temperature control circuit ATC (Automatic Temperature Control), code conversion circuit and emission light monitoring circuit, etc. Figure 6 Schematic diagram of the internal structure of the light emitting part.
[0048] Semiconductor lasers generate photons based on the principle of stimulated radiation and perform positive feedback amplification through an optical resonant cavity so that the gain of the generated photons is greater than the loss, and the laser is output.
[0049] (2) Light receiving part
[0050] The core photodetector of the light receiving part is a PIN photodiode. In addition to the core photodetector, the circuit parts include amplifiers, equalizers, decision devices, automatic gain control circuits AGC (Automatic Gain Control), decoding and code conversion circuits, etc. Figure 7 Schematic diagram of the internal structure of the light receiving part.
[0051] PIN photodiode is a three-layer structure device formed by a layer of intrinsic semiconductor (Intrinsic) sandwiched between heavily doped N layer and P layer. After the incident photon is absorbed by the intrinsic layer, the internal electrons jump from the low energy state to the high energy state, forming free electrons and holes. After the photogenerated carriers are generated, they move under the action of the built-in electric field to form a photocurrent.
[0052] Step 2: Perform qualitative analysis on the failure mode of the optical module based on the FTA method.
[0053] The failure of optical modules can be divided into two types: optoelectronic device failure and circuit failure. Optoelectronic devices and circuits work together, and circuit failure will be reflected in optoelectronic devices, directly affecting the working state of optoelectronic devices. For the core optoelectronic devices in optical modules, such as lasers and photodiodes, a fault tree model is established based on the FTA method to analyze the failure mode.
[0054] Figure 8 This is the laser fault tree model, where the top event T is the laser failure and the definitions of the intermediate events are shown in the following table.
[0055]
[0056]
[0057] The definition of bottom events is shown in the following table.
[0058] Event Number Event Definition Event Number Event Definition x1 Drive circuit failure x13 Shock x2 Fatigue degradation at solder joints x14 extrusion x3 External force damage at the solder joint x15 Chemical corrosion x4 Intermetallic Compounds x16 Electrolytic corrosion x5 Dark line defect x17 Oxidation x6 Temperature rise x18 Surge voltage x7 Semiconductor material degradation x19 Static Electricity Breakdown x8 Cavity surface damage defect x20 Intermetallic Compounds x9 Light Scattering x21 Solder joint thermal fatigue x10 Light Diffraction x22 Solder joints fall off x11 Increased light absorption x23 Coupling surface occlusion x12 vibration x24 Connector misaligned
[0059] Fig. 9 is the photodiode fault tree model, where the top event T is the photodiode failure and the definitions of the intermediate events are shown in the following table.
[0060] Event Number Event Definition Event Number Event Definition M1 Reduced responsiveness M9 Increased thermal noise M2 Too much noise M10 No light input M3 No electrical signal M11 External fiber damage M4 Quantum efficiency decreases M12 PIN Breakdown M5 Parasitic parameter changes M13 Pin damage M6 Dark current noise M14 corrosion M7 Leakage current increases M15 Wire bond failure M8 Increased carrier recombination current
[0061] The definition of bottom events is shown in the following table.
[0062]
[0063]
[0064] The main failure modes of the SFP+ packaged optical module include: too low transmitted optical power, no optical signal output, reduced responsiveness, excessive noise, and no electrical signal output. Each bottom event in the fault tree is a sufficient condition for causing the optical module to fail.
[0065] Responsivity is a performance measure for photodetectors. For optical modules, sensitivity is an optical module performance indicator corresponding to responsivity. Sensitivity is used to measure the performance of the receiving part of the optical module. It is defined as the minimum optical power that can be detected by the photodetector under a certain bit error rate level. The bit error rate refers to the ratio of the number of bit errors that occur within a certain period of time to the total number of bits of information transmitted during this period of time.
[0066] In optical modules, the reduced responsivity of the photodetector will increase the difficulty of generating photocurrent, resulting in an increase in the minimum optical power required to be detected while maintaining the bit error rate level. Therefore, the sensitivity and responsivity are inversely proportional, that is, the responsivity decreases and the sensitivity increases.
[0067] The main failure modes of optical modules are summarized as follows: too low transmitted light power, no optical signal output, increased sensitivity, excessive noise, and no electrical signal output.
[0068] Step 3: Calculate the risk priority number of each failure mode according to the RPN method.
[0069] The risk priority number of a failure mode is defined as the product of the severity level S and the probability level O:
[0070] RPNV=S×O
[0071] The severity S of each failure mode is defined with reference to the severity rating (ESR), and is divided into four levels, I to IV, according to the different degrees of impact of the failure mode on the device, corresponding to scores of 4 to 1, as shown in the following table.
[0072] Severity Severity Definition S-score Ⅰ Disaster, once it occurs, the device will lose all output parameters in a short time 4 Ⅱ Fatal, causing significant degradation of key parameters 3 Ⅲ Moderate, causing moderate damage to the device, with a certain delay effect on the device 2 Ⅳ Mild, not enough to affect the stability of the device's main output parameters 1
[0073] The occurrence probability level O is divided into five levels from A to E, corresponding to scores 5 to 1, as shown in the following table.
[0074] Probability level definition O score A Frequent occurrence, high probability 5 B Sometimes occurs, medium probability 4 C Occurs occasionally, not often 3 D Rarely occurs, unlikely to occur 2 E Very rare, almost 0 1
[0075] The risk priority values of the five failure modes, including too low transmitted light power, no light signal output, increased sensitivity, excessive noise, and no electrical signal output, are calculated and shown in the following table.
[0076] Failure Mode Severity S Occurrence probability level O Risk Priority Value Transmitted light power is too low 3 A(5) 15 No light signal output 4 D(2) 8 Increased sensitivity 3 A(5) 15 Too much noise 2 C(3) 6 No electrical signal output 4 D(2) 8
[0077] Step 4: Analyze key failure modes using the relationship matrix.
[0078] According to the risk priority value of the failure mode, the hazard level of each failure mode can be divided into four levels, and the hazard level decreases from i to iv. Figure 2 The diagram below shows how the hazard level is divided according to the risk priority value. The prevalence of environmental stress is divided into four levels: (1) rarely exists; (2) occasionally exists; (3) often exists; and (4) always exists.
[0079] The criticality level of each failure mode and the prevalence level of environmental stress are used as the input of the relationship matrix to identify the threat of the failure mode, and the most threatening one is the critical failure mode.
[0080] The criticality levels of the five failure modes of the optical module are shown in the following table.
[0081]
[0082]
[0083] The environmental stresses existing in the working scenario of the optical module include thermal stress, vibration stress, mechanical impact stress, water vapor, and static electricity.
[0084] The prevalence level of each environmental stress is shown in the following table.
[0085] Environmental stress Universality level Heat stress (4) Must exist Vibration stress (2) Occasionally exists Mechanical shock stress (1) Rarely exists Water vapor (1) Rarely exists Static electricity (1) Rarely exists
[0086] The criticality level of the failure mode and the prevalence level of the environmental stress are input as the relationship matrix to identify the threat of each failure mode. The threat level is classified as follows: Fig.10 shown. Fig.11The relationship matrix results for the output show that low transmitted light power, no optical signal output, increased sensitivity, and no electrical signal output under the influence of thermal stress are the most threatening failure modes for the optical signal transmission system.
[0087] There are 5 types of initial failure modes of optical modules and 5 types of environmental stresses, with a total of 25 combinations of environmental stresses and failure modes. After analysis, the four key failure modes under the influence of thermal stress are found to be too low optical power, no optical signal output, increased sensitivity, and no electrical signal output. The complexity of the research is effectively reduced.
Claims
1. A method for analyzing key failure modes of an SFP+ packaged optical module, comprising the following steps: Step 1: Analyze the internal structure and working principle of the optical module; Step 2: Qualitatively analyze the failure mode of the optical module based on the FTA method; Step 3: Calculate the risk priority number of each failure mode according to the RPN method; Step 4: Analyze key failure modes using the relationship matrix.
2. A method for analyzing key failure modes of an SFP+ packaged optical module according to claim 1, characterized in that: In step 1, the analysis of the internal structure and working principle of the optical module should be combined with the results of non-destructive testing, destructive physical analysis and other methods as well as the product specification.
3. A method for analyzing key failure modes of an SFP+ packaged optical module according to claim 1, characterized in that: In step 2, a qualitative analysis of the failure mode of the optical module is performed based on the FTA method. Fault tree models are established for the core optoelectronic devices in the optical module, such as lasers and photodiodes, to analyze the failure mode.
4. The method for analyzing key failure modes of an SFP+ packaged optical module according to claim 1, characterized in that: In step 3, the risk priority number of each failure mode is calculated with reference to the RPN method. The risk priority number is defined as the product of the severity of the failure mode and the probability level of occurrence. The severity of each failure mode is defined with reference to the severity level and is divided into four levels from I to IV, corresponding to scores of 4 to 1 respectively. The occurrence probability level is divided into five levels from A to E, corresponding to scores 5 to 1 respectively.
5. The method for analyzing key failure modes of an SFP+ packaged optical module according to claim 1, characterized in that: In step 4, the criticality level of each failure mode and the prevalence level of environmental stress are used as the input of the relationship matrix to analyze the threat of each failure mode. The most threatening failure mode is the key failure mode. Among them, the criticality level is divided into four levels according to the risk priority number, from i to iv. The prevalence of environmental stress is divided into four levels, from 1 to 4, which are: (1) rarely exist; (2) occasionally exist; (3) often exist; (4) always exist.