A loopback test is a hardware or software method which feeds a received signal or data straight back to the sender. It is actually used as an help in debugging physical connection problems.
Fiber optic transceiver is definitely the fundamental part in almost any fiber optic communication network equipment. Its function is exactly the same as your computer’s Ethernet Card. (although just about all modern computers integrate it around the motherboard, not as an independent PCI card anymore)
Fiber optic transceiver has two ports, a transmitter port along with a receiver port. The fiber optic cable port sends out laser signal to a linked transceiver as well as the receiver port receives laser signal from your other transceiver.
On fiber optic transceiver manufacturing floors and then in R&D labs, we usually work with a fiber optic loopback module to make sure that the transceiver is working perfectly as designed as an alternative to using another transceiver as its partner.
Basically exactly what the loopback module does is directly routing the laser signal in the transmitter port returning to the receiver port. We can compare the transmitted pattern with all the received pattern to make sure they are identical and get no error.
The most common kinds of Optical 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 offered for three fiber types. They can be 50/125um multimode, 62.5/125um multimode and 9/125um single mode.
Only PC polish is offered for multimode type fibers. But for single mode fiber, two connector polish types are available: UPC polish and APC polish.
Along with fiber type, working wavelength is definitely the other important aspect for picking the proper fiber optic loopback module to your specific application. Available wavelengths are 850nm, 1310nm dexhpky91 1550nm. 850nm and 1310nm are for multimode applications and 1550nm is for single mode applications.
It is possible to specify exactly how the signal power level ought to be reduced within the loopback path. Simply because the receiver port cannot handle very high power. And in real life fiber patch cord, there are always attenuations created by fibers, equipment and physical environment. Hence the transmitter power is attenuated to your safe level through the network before reaching one other receiver.