Fiber Optic Cable & Fire Alarms – Light Years Away from Trouble Free?

By John M. Stofa ©2013

One of the challenges that sophisticated modern fire alarm systems face is the possibility of damage or performance issues caused by lightning, interference due to localized “noise” in the area, or the introduction of water into network cable conductors.  Any one of these conditions could cause the system to operate erratically or perhaps not at all. The best way to overcome all of these problems is the use of Fiber Optic Cables (FOC) for the alarm system backbone or fire alarm network.  But this has also brought with it new challenges that are caused by the very people installing the system; a lack of training resulting in poor installation. 

There are many factors to think about when working with FOC, and this blog will discuss just a few of the heavy hitters.  It is my hope that this discussion will compel one to seek more education and training on how to properly install FOC.

Electricians and installers since the beginning of the modern fire alarm system have been installing copper cables for the fire alarm system with great success.  After the install, the low voltage alarm company is typically responsible for terminating the panels or connecting the wires and then “turning the system on” as it were.  For the most part with some exceptions, the pulling or installing of the copper wire has been a fairly straightforward process.  The difference between copper wire and FOC however is the quality of the end connection or termination, and the ability to send light or communication data down the FOC without it being compromised or degraded to the point where it is useless. 

When pulling copper wire, deep bends in the conductor are not really a problem and poor connections can usually be overcome or easily dealt with.  This is not necessarily the case with FOC.  Deep bends in a FOC can cause performance issues that could present as system “troubles” throughout the network.  See example Photo 1.  Note the grey fiber strand and the deep bends being forced by the copper conductor lying on top of it.

Photo 1

This is a very poor installation and one that should be dealt with immediately.  The grey strand needs to be reconnected and allowed to bend gently as seen with the green strand next to it. 

The next photo is another example of an installation that was perhaps done by an electrician that was more familiar and comfortable using copper than FOC.  Photo 2 shows what happens when the FOC is too long and rather than making it the right length and properly terminating the strands, the installer just loops the extra FOC between the patch panel and the fire alarm panel on a 4” module resulting in deep bends which could cause back scattering of the light, and again possibly putting the system in “trouble”.

Photo 2

The FOC end termination or connector is a delicate part of the puzzle that could result in a poorly operating system.  Often the connector and couplings could be of such poor quality or installed improperly that the overall dB loss for the fiber run could exceed

the allowable limits. They could also have too many couplings installed which also adds to the overall dB loss budget.   In this case the fiber run must be tuned and excessive or poor quality connectors and couplings must be replaced.  This should be dealt with early on in the process before the equipment is even turned on. 

Having the fiber runs measured and certified from end-to-end is critical to creating a fiber network that will perform flawlessly.  This certification is often not performed and the installer simply attempts the plug ‘n play method of let’s see if this works.  Compounded by the fact that most low voltage installers are not qualified to terminate fiber ends and you see installations like Photo 3.  This installer may have an acceptable fiber run from end-to-end, that being patch panel-to-patch panel, but the orange patch cord is now adding extra length and deep bends that could decrease the fiber’s performance and possibly fracture the fiber stand itself.

   

Photo 3

The fact is, FOC is going to be much more prevalent in the next 2 years as the Telcom Industry sunsets copper phone networks in favor of FOC.  This will ultimately force the fire alarm industry to also acquiesce or be left behind.  If you think your lack of knowledge in FOC is going to be a hurdle for your team to overcome, then you must start now in building upon their education and experience rather than face an uphill battle in the months to come.