During the use of the optical module,it is inevitable that various problems will occur.When we connect the optical module with the optical module through the optical fiber,the optical port light is not on,the optical port light is red,or the alarm,the optical module fails,etc.Then where is the fault of the optical module?Is it the fault at the transmitting end or the receiving end of the optical module?Is it the internal problem of the optical module itself?Or is it caused by improper external use?This paper summarizes the common faults of the optical module and gives corresponding solutions to help you detect and troubleshoot the faults of the optical module in use.

　　Common internal faults and solutions of optical modules

　　In the process of daily use of optical modules,we may encounter internal failures such as poor optical power,poor eye pattern,poor receiving end,poor working current,and program programming failure.When encountering the above-mentioned faults,we can check the appearance of the optical module to see whether there is obvious damage to the optical module,or use some tools to detect and compare with a complete optical module to find out the faults of the optical module.

　　The following content takes the fast(FS)1g SFP optical module as an example to explain the fault causes of the optical module,corresponding fault detection methods and fault solutions in detail.

　　Fault 1:degradation of optical power performance of optical module

　　The optical power degradation performance failure of the optical module may cause the following phenomena of the optical module:

　　1.The bias current is within the normal range,and the optical power is beyond/below the control range;

　　2.If no light is on,the bias value is displayed as 0,or the bias is short circuited,and the value is large,and the display is 90mA~150mA;

　　3.During commissioning,some lights are on,but the light power is unchanged;

　　If the first phenomenon mentioned above occurs in the optical module,it may be due to the damage of the Tosa emitting component of the optical module,the poor welding of Tosa pins PD+,or the mismatch between the power and resistance and the bias current.The corresponding solutions are:replace the Tosa emitting component of the optical module,re weld the Tosa pins PD+,or adjust the power and resistance;

　　If the second phenomenon mentioned above occurs in the optical module,it is also possible that the Tosa pins PD+is poorly welded,or the memory chip is faulty,and the magnetic beads on the LD-/LD+line are damaged.The corresponding solutions are:re weld the Tosa pins PD+,replace the memory chip on the optical module,and reconnect the same type of magnetic beads on the LD-/LD+line;

　　If the third phenomenon mentioned above occurs in the optical module,it may also be due to the damage of Tosa emitting components or the poor welding of Tosa pins LD.In this case,replace the Tosa emitting components or re weld the Tosa pins PD+.

　　Fault 2:poor eye pattern of optical module

　　Poor eye pattern of optical module generally includes poor extinction rate,scattering of eye pattern,irregular pattern,or no eye pattern.

　　The reason for poor extinction ratio is that the extinction ratio is too large or too small.In this case,the Tosa emitting component should be replaced or the optical power resistance should be reduced/increased;

　　The causes of eye pattern scattering of the optical module include Tosa damage,poor performance of the drive chip,or signal impedance mismatch.In this case,replace the Tosa inside the optical module,replace the drive chip,or change the front-end matching resistance;

　　When the eye pattern of the optical module is irregular,it is necessary to modify the values of the pull-up/pull-down resistance and the matching resistance;

　　When the optical module has no eye pattern during detection,it is because the Tosa is damaged or the matching resistance at the front end is poorly welded.At this time,replace the damaged Tosa component or re weld the matching resistance.

　　Fault 3:poor performance of optical module receiving end

　　The performance of the receiving end of the optical module is poor,mainly including low sensitivity(even no sensitivity)or alarm dysfunction.

　　There are many reasons for low sensitivity or sensitivity failure of the optical module.The common ones are damage of Rosa components,poor contact of Rosa pins out+and out-,too small extinction ratio of light source,poor welding or missing of magnetic beads,damage or poor performance of limiting amplifier chip.For the above reasons,the solutions are:replace Rosa components in the optical module,re weld and reinforce Rosa,adjust the extinction ratio to 10+,re paste magnetic beads Replace the limiting amplifier;

　　When the optical module has alarm dysfunction,the main reason is that the Rosa component is damaged or the alarm resistance does not match.At this time,it is only necessary to replace the Rosa component or change the alarm resistance value.

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