How to test the receiving sensitivity of optical communication?

It can be seen that there is some understanding of communication upstairs, but there are also some mistakes.

First of all, the power is expressed in W, kw and mw, but dBm is mainly used in optical communication, isn't it?

According to the definition in communication, the optical power of 1mw is 0dBm, not 1dBm upstairs.

The expression upstairs is a fatal mistake. Let the power of a beam of light be Pmw, that is to say, the dBm number is n.

NdBm = 10 log 10(P/ 1mw)

When the incident power is 1mw, ndbm =10log10 (1MW/1MW) = 0dbm.

When the incident power is 10mw, NDBM =10log10 (10mw/1MW) =10dbm.

When the incident power is 100mw, NDBM =10log10 (100 MW/1MW) = 20 DBM.

When the incident power is 0. 1mw, NDBM =10log10 (0.1MW/1MW) =-10dbm.

Secondly, the definition of "sensitivity is the ratio of the electrical signal power generated by the receiver to the optical power incident on the receiver" upstairs is also very wrong.

The definition of receiver sensitivity is the optical power received by the receiver when the receiver error rate reaches the power of-10.

According to the requirements of the topic, you can test it like this:

Use two optical fibers to interconnect a pair of optical ports of two switches (ensure that the interconnected optical ports are not the upstream ports of the switches. For example, the first port of switch A sends, the first port of switch B receives, the first port of switch A receives and the first port of switch B sends). Connect the computer to the network port (RJ45 interface) of one switch with a network cable, and loop back to the port of another switch with a special loopback device.

Disconnect the optical fiber at the receiving point of the first port of switch B, connect it to the input of the optical attenuator, and connect another optical fiber from the output of the optical attenuator to the first port of switch B for receiving.

At this time, the computer is used to send data continuously, then the variable optical attenuator is adjusted, and the bit error rate of the receiving port of switch B is observed through the special network management software on the computer. When the bit error rate reaches the power of-10, the attenuation of the variable optical attenuator stops.

At this time, disconnect the optical fiber at the receiving point of the first port of switch B and introduce the optical fiber into the optical power meter. At this time, the optical power value displayed on the optical power meter is the receiving sensitivity of the first port of switch B.

The sensitivity test of other ports is similar.

When using optical power meter to test optical power, we should pay attention to choosing the right wavelength, and the value measured by choosing the wrong wavelength is somewhat different!