What is a loopback test?

A loopback check is a hardware or application technique which feeds a obtained sign or knowledge back to the sender. It is employed as an assist in debugging physical link problems.

Fiber optic transceiver loopback test

Fiber optic transceiver is the elementary element in any fiber optic communication network products. Its purpose is specifically the same as your computer’s Ethernet Card. (though almost all present day computers integrate it on the motherboard, not as a different PCI card any more)

Fiber optic transceiver has two ports, a transmitter port and a receiver port. The transmitter port sends out laser signal to a connected transceiver and the receiver port receives laser sign from the other transceiver.

On fiber optic transceiver producing floors and in R&D labs, we typically use a fiber optic loopback module to validate the transceiver is doing work perfectly as developed as an alternative of employing an additional transceiver as its partner.

Fundamentally what the loopback module does is directly routing the laser sign from the transmitter port again to the receiver port. Then we can assess the transmitted sample with the acquired pattern to make sure they are equivalent and have no error.

What types of loopback modules are available?

The most common kinds of fiber optic loopback modules are SC, LC and MTRJ connector varieties. But each connector kind is divided again by fiber sort, connector polish type and attenuation.

fiber optic tools is obtainable for a few fiber types. They are 50/125um multimode, sixty two.five/125um multimode and 9/125um one mode.

Connector Polish Types

Only Computer polish is obtainable for multimode sort fibers. But for single method fiber, two connector polish kinds are accessible: UPC polish and APC polish.

Working Wavelength

In addition to fiber kind, functioning wavelength is the other essential aspect for choosing the right fiber optic loopback module for your distinct software. Obtainable wavelengths are 850nm, 1310nm and 1550nm. 850nm and 1310nm are for multimode purposes and 1550nm is for single manner purposes.


You can specify how the signal energy amount need to be lowered in the loopback route. This is because the receiver port cannot deal with extremely higher energy. And in true daily life fiber optic network, there are often attenuations introduced by fibers, tools and actual physical surroundings. So the transmitter energy is attenuated to a risk-free degree through the network before reaching the other receiver.

Even so because you are routing the transmitter straight back again to the receiver, attenuation normally have to be additional to safeguard the receiver.

How significantly attenuation ought to be added relies upon on your transceiver variety and you have to choose it by oneself. Thankfully, there are a broad assortment of attenuation options obtainable from 0dB, 1dB, 2dB to 24dB or even a lot more.


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