SFP optical transceiver is a hot-swappable, compact component that provides fiber connectivity for optical networking. They support various applications like Fibre Channel (FC) switches, SONET/SDH network, Gigabit Ethernet, high-speed computer links, and CWDM and DWDM interfaces. When connected to switches, the optical signal strength of SFP modules is a critical parameter to ensure the normal working of the whole connections. This article will introduce the method of SFP module signals measurement and how to check SFP module optical signal strength.Generally, the signal strength of SFP module includes two parts: Tx power and Rx power. The former one stands for the transmit power signal, and the latter stands for the receive power signal. For a normal SFP transceiver, the value of the Tx and Rx power lies in a specific range, in which the SFP transceiver can work normally. Take Cisco GLC-SX-MM 1000BASE-SX SFP as an example, its transmit power range is -3 to -9.5dBm, and the receiver power range is 0 to -17dBm. If either the Tx or Rx power is in the -30dBm or lower range, it means there is no actual signal being transmitted or received.
The strength of optical signals directly determines whether the network connections can work normally or not. If the Rx power is not strong enough, there will be no signals in the optical links. That’s why a long-reach transceiver or an optical amplifier is needed in long haul transmission. And if the Rx power is too strong, the SFP module will be damaged. Therefore, a quality SFP transceiver is the basic guarantee for a smooth connection.
Generally speaking, there are two common methods to measure optical power strength: milliwatt (mW) and dBm which is short for decibel of the measured power referenced to one milliwatts. The former one measures optical signal strength by power, while the latter describes signal strength with absolute power value. Different vendors may adopt one of them to describe signal power. For instance, Cisco switches are used to adopt dBm to measure the power, while other switches get accustomed to using mW. Since the optical power is small, sometimes microwatt (µW) is also used in some switch vendors. Therefore, there are conversions between these methods.Click here to learn more