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What is the DDM for SFP Transceiver?

Date: 2019-09-17 12:12 From: 未知 Onclick:

In the information age, people's demand for network data transmission is getting higher and higher, so the optical transceiver has developed rapidly. SFP transceiver with DDM play an important role in the optical link for the location of location faults and real-time parameter monitoring to predict laser degradation.

What is the DDM for SFP Transceiver ?
DDM is Digital Diagnostic Monitoring. Through DDM, users can monitor the real-time parameters of the transceivers, including operating temperature, operating voltage, operating current, transmit and receive optical power, etc., and also display the module's factory information, prompt alarms/warnings. At the same time, it provides a performance monitoring method for the system, which can help the system manage the life of the prediction module, isolate the system failure, and verify the compatibility of the module in the field installation.

How to make a digital diagnosis?
1.Confirm that the tested optical module is placed in the switch port and record the port number.
2.Open the HyperTerminal and enter the following command (for example, Huawei devices):
Optical  transceiver digital diagnostic information read command:
Display transceiver diagnostic interface XGigabitEthernet 0/0/1

The various data derived from the digital diagnostic function of the optical module should be determined from which data to determine different performance. Analyze DDM from the following three aspects, C-Light hopes to help you.

1.How to predict the life of the laser ?
The process of controlling the output power to maintain a stable level is achieved by the optical power feedback control unit inside the optical transceiver by increasing the bias current (Tx_Bias) of the laser. As the laser ages, the quantum efficiency of the laser It will decrease accordingly, so we can predict the lifetime of the laser by monitoring the bias current of the laser.

2.How to find potential problems and determine the location of the fault?
By monitoring the operating voltage and temperature inside the transceiver module in real time, the system administrator can discover some potential problems:
1) If the Vcc voltage is too high, it will cause breakdown of the CMOS device; if the Vcc voltage is too low, the laser will not work properly.
2) The receiving power is too high and will damage the receiving module.
3) The operating temperature is too high, which will accelerate the aging of the device. In addition, the performance of the line and remote transmitters can be monitored by monitoring the received optical power.
4)Through comprehensive analysis of the detected Tx_power, Rx_power, temperature, operating voltage, Tx_Bias warning and alarm status, state variables TxFault and RxLOS in the memory image, it is possible to locate whether the fault occurs in the module or on the line.

3.How to verify compatibility?
Another function of digital diagnostics is the compatibility verification of the module. Compatibility verification is to determine whether the working environment of the module is compatible with the data sheet or related standards. The performance of the module can only be guaranteed in this compatible working environment. In some cases, because the environmental parameters exceed the data sheet or related standards, the performance of the module will be degraded, resulting in transmission errors. The working environment is incompatible with the module:
1) The voltage is outside the specified range;
2) Receive optical power overload or lower than receiver sensitivity;
3) The temperature is outside the operating temperature range.

The output of the physical value of each parameter of the DDM comes from the analog voltage or current of the Trans-Impedance Amplifier, Laser Driver or Post Amplifier.Through DDM, it is more convenient to manage the parameters of the SFP module, which is more suitable for the management of network data transmission. In general, choosing an SFP module with DDM is the best choice. If you want to learn more about DDM, What are the DDM, DOM and RGD functions of SFP optical modules?


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Links: IEEE | ECOC