A loopback test is really a hardware or software method which feeds a received signal or data back to the sender. It is used being an assist in debugging physical connection problems.
Fiber optic transceiver is the fundamental part in almost any fiber optic communication network equipment. Its function is identical to your computer’s Ethernet Card. (although almost all modern computers integrate it in the motherboard, not as a separate PCI card anymore)
Fiber optic transceiver has two ports, a transmitter port along with a receiver port. The direct attach cable port sends out laser signal into a linked transceiver and also the receiver port receives laser signal in the other transceiver.
On fiber optic transceiver manufacturing floors and also in R&D labs, we usually utilize a fiber optic loopback module to verify the transceiver is working perfectly as designed rather than using another transceiver as the partner.
Basically precisely what the loopback module does is directly routing the laser signal in the transmitter port to the receiver port. Then we can compare the transmitted pattern using the received pattern to make sure they are identical and have no error.
The most popular forms of fiber optic transceiver are SC, LC and MTRJ connector types. But each connector type is divided again by fiber type, connector polish type and attenuation.
Each connector type is accessible for three fiber types. These are 50/125um multimode, 62.5/125um multimode and 9/125um single mode.
Only PC polish is offered for multimode type fibers. However for single mode fiber, two connector polish types can be purchased: UPC polish and APC polish.
Along with fiber type, working wavelength is the other important aspect for picking the correct fiber optic loopback module for your specific application. Available wavelengths are 850nm, 1310nm dexhpky91 1550nm. 850nm and 1310nm are for multimode applications and 1550nm is perfect for single mode applications.
You can specify just how the signal power level should be reduced from the loopback path. It is because the receiver port cannot handle very high power. And in real life fiber optic cable, there are always attenuations introduced by fibers, equipment and physical environment. So the transmitter power is attenuated to your safe level with the network before reaching another receiver.