What's the difference between an Armored Fiber Cable and a common Fiber Cable?

[PeterBrown]

I wonder which one to choose, Armored Fiber Cable or a common one?

[LenSamuelson]

Selection of communication medium is so dependent on one's application that there is effectively no "correct" way to respond to your question.

Armored optical fiber (what I call traditional high speed fiber) is intended to be used for extended runs across buildings, through conduits, etc. Unarmored optical fiber is used for less distant connections (in the range of up to tens of meters) generally inside server spaces that are environmentally friendly. Both forms of optical fiber tend to be used in high bandwidth applications.

There is also plastic optical fiber ("POF") which has cladding, so it's protected but not "armored". It tends to be used where the communicating devices are up to about 50-80 meters apart, and supports bandwidths up to about 50 Mbits/sec (very approximate).

The project my co-workers and I have implemented uses plastic optical fiber. Between a gateway device and the first remote device we have reliable operation of about 10 Mbits/second up to 60 meters. Between remote devices the length is usually 1 to 3 meters. Our comms is very very reliable, and has essentially no sensitivity to electromagnetic interference, and is (obviously but is worth restating) electrically isolated. Our remote devices are installed in environmentally challenging, harsh environments outdoors so we use cables that run power (low voltage) and fiber together: Two conductors and two fiber links in each cable.

[PeterBrown]

Selection of communication medium is so dependent on one's application that there is effectively no "correct" way to respond to your question.

Armored optical fiber (what I call traditional high speed fiber) is intended to be used for extended runs across buildings, through conduits, etc. Unarmored optical fiber is used for less distant connections (in the range of up to tens of meters) generally inside server spaces that are environmentally friendly. Both forms of optical fiber tend to be used in high bandwidth applications.

There is also plastic optical fiber ("POF") which has cladding, so it's protected but not "armored". It tends to be used where the communicating devices are up to about 50-80 meters apart, and supports bandwidths up to about 50 Mbits/sec (very approximate).

The project my co-workers and I have implemented uses plastic optical fiber. Between a gateway device and the first remote device we have reliable operation of about 10 Mbits/second up to 60 meters. Between remote devices the length is usually 1 to 3 meters. Our comms is very very reliable, and has essentially no sensitivity to electromagnetic interference, and is (obviously but is worth restating) electrically isolated. Our remote devices are installed in environmentally challenging, harsh environments outdoors so we use cables that run power (low voltage) and fiber together: Two conductors and two fiber links in each cable.

Thank you for your reply. But I have another question, normal fiber cable has plastic cladding too, doesn't it? What's the difference between a common optical fiber and a plastic optical fiber?

[LenSamuelson]

I should have written better.. Yes, all current fiber has basic cladding, so the answer is "yes".

That said (again this is just the way I have perceived the world of communications), historically "fiber" was expensive glass fiber (always in cladding :-) ) used in applications where its expense was justified by performance or isolation constraints. It's "common" in the sense that back-in-the-day this sort of high-performance, extended-run, expensive fiber is what most people hear about.

Plastic optical fiber is "recent" (last 8-10 years or so), and while transceivers are more expensive than just RS-422 twisted pair its cost is low enough to be worth considering for normal industrial applications. Its isolation and EMI characteristics simplify decisions where EMI or regulatory requirements would be burdensome.