The Top Fiber
Questions blog series is dedicated to answering the most asked questions in the
industry. From now until the end of the year, we hope to provide great answers.
Most importantly, we’d love for you to ask your fiber questions in the comments
Can I bend fiber around a sharp corner?
I am a big proponent of bend insensitive fiber (BIF),
although I like to call it RBR fiber, or reduced
bend radius fiber. Why is that?
- It gives great flexibility in the construction
of panels and frames, assisting in better cable management.
- There are clear specifications for the bend
- With proper testing and use, the RBR fiber provides
a more reliable network.
CLICK TO TWEET: A fiber question for you: can you bend fiber around a sharp corner?
In the past, we were limited to where and how we placed
slack storage. We devised spools up in the overhead tray to keep a large bend
radius. Sometimes we’d run patches through different frames to keep the bends
out and take up all the slack needed. Now that RBR fiber is rated to a
particular standard, there are panels, frames, wall boxes, etc. that can spool
the slack right in the unit.
But does this mean you no longer worry about how to
handle slack coils? Does bend-induced loss go away? Do you even bother testing
for it? There are still fiber optic glass bend radius standards. ITU-T G.657.A1 has a minimum bend radius of
10 mm, G.657.A2/B2 at 7.5 mm and G.657.B3 down to 5 mm. With specified bend
radii, you need to maintain clean systems with the proper RBR. There may still be bend loss, but maybe not
in the same way as the past. Historically, you would trace the fiber to
physically see the bend. With today’s fiber, the bend loss might indicate more of
an improper seating of a connector or a routing issue in a splice tray.
What about testing? One might argue that testing at one
wavelength is fine. I believe it is beneficial to test at both 1550 nm and 1310
nm, and compare results. Remember that if 1550 nm loss is higher than the 1310 nm
loss, then there is a bend in the system under test. Because of the
characteristics of RBR fiber, the bend will be extreme and may help find the
bend. There is also a possibility that the bend is occurring within the
connector and not visible. Hence, discovering if the loss is bend induced or
some other attenuation is critical.
RBR fiber is a great step in fiber technology that will
expand to all parts of the network – even the outside plant. Keep in mind, with
proper use and cable management, we should be able to eliminate bend loss through
the entire network.
Speaking of OSP: our next topic is how RBR
impacts optical time-domain reflectometer (OTDR) readings and splice machine
operations. In the meantime, tell us your bendable fiber stories.