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How to Measure Power Level of SFP Transceiver Modules?

October 26, 2019

There are two ways to measure the Output power (TX power) and the receiver sensitivity (RX sensitivity) of SFP transceivers.

DDM/DOM Information Reading Through Switch

DDM is short for Digital Diagnostic Monitoring, which provides users with critical information concerning the status of the transmitted and received signals. Through real-time monitoring of the module's internal operating voltage, temperature, receiver power, transmitter bias current, and transmitter power, this approach allows for better fault isolation and error detection.

Example of DDM INFO for a Transeiver Module

When the transceiver supports DDM/DOM, TX Power and Rx sensitivity will display on the transceiver information board. Some of the transceivers will show alarm and error information as above the HPE switch showcase.

Optical Power Meter

Using the optical power meter is another method to measure the TX/RX optical power of transceivers. Taking FS 10GBASE-LR SFP+ module as an example, the test steps are as follows:

  • First, insert the 10GBASE-LR SFP+ transceiver into the SFP+ port of the 10G switch.

  • Then, connect the optical transceiver to the optical power meter using LC-FC single mode fiber patch cables.

  • Finally, press the switch of the optical power parameter, and press the "λ" key to modulate the wavelength of the 10GBASE-LR SFP+ optical module (that is to say, to modulate the wavelength at 1310nm). When completed, the number displayed on the screen is the transmitted optical power of the modules. Also, the transmitted optical power is equivalent to the received optical power of the transceiver on the other side over a short distance link.

TX/RX Optical Power of Transceiver Tested by Optical Power Meter

When there is something wrong with the optical power of SFP transceivers, such as the large/small optical power, unstable optical power, low side-mode suppression ratio, and so on, you need to troubleshoot the modules by following this article: How to Troubleshoot A Fiber Optic Transceiver?

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