#fiber optic loopback

[fibermodeca-blog]

MTP|MPO Singlemode Fiber Optic Loopback OS1

For more information viist: http://www.fibermode.com

[qing-chloe-blog]

Do You Know Fiber Optic Loopback?

Fiber optic testing and troubleshooting are necessary processes in fiber optic cabling. Usually the common tools for this use are visual faults locator, optical power meter, OTDR, etc. Today, this post would introduce another device that also can be used to diagnose a problem of optical equipment—fiber optic loopback. Fiber optic loopbacks can provide an economical solution for a number of fiber optic test applications. Now let’s get together to know more about it.

What Is Fiber Optic Loopback?

Fiber optic loopback has two fiber optic connectors on each end of the cable. Generally, there are two forms of fiber optic loopbacks: fiber optic loopback cable and fiber optic loopback module. The biggest difference between them is that fiber optic loopback module has an enclosure to protect the cable inside. Fiber optic loopback is used to provide a medium of return patch for an optical signal, especially for fiber optic testing applications and network restorations. And it is very useful when you have a physical connection problem. Fiber optic loopbacks have different compact designs, and they are compliant with Fast Ethernet, Fibre Channel, ATM (Asynchronous Transfer Mode) and Gigabit Ethernet.

How Many Types of Fiber Optic Loopback Do You Know?

As we have mentioned above, fiber optic loopbacks have two fiber connectors on each end, which is similar to fiber patch cords. Therefore fiber loopback cables can be classified by the connector types such as LC fiber loopback, SC fiber loopback, FC fiber loopback and MTRJ fiber loopback. Each type has the similar features with corresponding connectors. Take LC fiber optic loopback cable for example. SC fiber optic loopback plug connector is compliant to IEC, TIA/EIA, NTT and JIS specifications. It has pulls proof design. And this loopback cable has a low cost but high performance, which makes it one of the most popular cables. Besides, fiber optic loopback cables also can be divided into single-mode and multimode loopbackes. These classified methods mentioned above also go with the practice of fiber optic loopback modules because of their similar structures.

What Is Fiber Optic Loopback Used for?

Fiber optic loopbacks can be used in a number of applications such as equipment interconnection, device pig-tailing, premise networks, patch panel applications and communications connections. But here I’d like to introduce one of its common application—fiber optic loopback testing.

A fiber loopback test is a hardware or software method which feeds a received signal or data back to the sender. It is used as an aid in debugging physical connection problems. And the fiber loopback test can be utilized to check whether the fiber optic transceiver is working perfectly as designed. As we all know, fiber optic transceiver has two ports, a transmitter port and a receiver port. The former one is to send out laser signals and the latter is to receive signals. Thus, during the testing process, the loopback module directly routes the laser signal from the transmitter port back to the receiver port. Then we can compare the transmitted pattern with the received pattern to make sure they are identical and have no errors. Fiber optic loopback testing is the easiest way to ensure that the transceiver works faultlessly.

Summary

All in all, even if fiber optic loopbacks have the same division ways of fiber optic cables, they are designed for equipment testing, self-testing, engineering, network diagnostics and measurement applications. Besides, the fiber optic loopbacks with precision ceramic ferrule feature extremely low loss for transparent operation in the test environment and in form of cable and module types. Therefore they play an important role in troubleshooting in laboratories and manufacturing environments and provide an effective way to test the transmission capability and receiver sensitivity of optical network equipment.

From:http://www.chinacablesbuy.com/know-fiber-optic-loopback.html

[sallyfiber]

Fiber optic transceiver loopback test

Fiber optic transceiver is the fundamental part in any fiber optic communication network equipment. Its function is exactly the same as your computer’s Ethernet Card. (although almost all modern computers integrate it on the motherboard, not as a separate PCI card anymore)

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

On fiber optic transceiver manufacturing floors and in R&D labs, we usually use a fiber optic loopback module to verify the transceiver is working perfectly as designed instead of using another transceiver as its partner.

Basically what the loopback module does is directly routing the laser signal from the transmitter port back to the receiver port. Then we can compare the transmitted pattern with the received pattern to make sure they are identical and have no error.

What is a loopback test?

A Fiber optic loopback test is a hardware or software method which feeds a received signal or data back to the sender. It is used as an aid in debugging physical connection problems.

What types of Fiber loopback modules are available?

The most popular types of fiber optic loopback modules are SC, LC and MTRJ connector types. But each connector type is divided again by fiber type, connector polish type and attenuation.

     Fiber Types

Each connector type is available for three fiber types. They are OM2 50/125um multimode, OM1 62.5/125um multimode and 9/125um single mode.

Connector Polish Types

Only PC polish is available for multimode type fibers. But for single mode fiber, two connector polish types are available: UPC polish and APC polish.

Working Wavelength

In addition to fiber type, working wavelength is the other important factor for choosing the correct fiber optic loopback module for your specific application. Available wavelengths are 850nm, 1310nm and 1550nm. 850nm and 1310nm are for multimode applications and 1550nm is for single mode applications.

Fiber optic Attenuation

You can specify how the signal power level should be reduced in the loopback path. This is because the receiver port cannot handle very high power. And in real life fiber optic network, there are always attenuations introduced by fibers, equipment and physical environment. So the transmitter power is attenuated to a safe level through the network before reaching the other receiver.

However since you are routing the transmitter directly back to the receiver, attenuation usually must be added to protect the receiver.

How much fiber optic attenuation should be added depends on your transceiver type and you must decide it by yourself. Fortunately, there are a wide range of attenuation options available from 0dB, 1dB, 2dB to 24dB or even more.

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