There is a certain amount of transmission loss (attenuation) that occurs as the light traverses the strands within a fiber optic cable.  Over a short distance, this loss is negligible; but over a long distance, signal loss can add up.  Schneider Electric’s Fiber Manager™ Trace Report (Figure 1), as well as the OTDR and Circuit Traces, summarizes the attenuation loss at two frequencies (1310 nm and 1550 nm).  Maximum loss per kilometer (dB/km) is typically provided on manufacture’s specifications.

When using the OOTB Fiber Manager™ Model (i.e., Minerville), there are four fiber optic cable fields that document a cable’s attenuation as follows:

• EstSMAattenuation1310
• EstSMAttenuation1550
• EstMMAttenuation850
• EstMMAttenuation1310

Only two of these fields are used in Fiber Manager™ reporting.  These are the fields with the AttenuationAFreq and AttenuationBFreq field model names which are usually the singlemode fields.  As a result, the multimode fields are for information only, and ignored by the OOTB Reports.

As a potential solution, SSP recommends a GIS Administrator change the alias of the EstSMAattenuation1310 and EstSMAttenuation1550 fields to AttenuationAFreq AND AttenuationBFreq respectfully.  This way, these fields can be utilized by either singlemode, multimode, or hybrid (combination of both) cables assuming a common frequency.  The Administrator can also change the ArcFM™ visibility of the existing multimode fields (especially if they are never used within the system).

A problem may arise when Fiber Manager™ uses the length of the cable to calculate the loss contribution.  Numerous municipalities utilize the State Plane Coordinate System and typically have units of feet.  Users that enter the manufacturer’s supplied values in db/km, will have an attenuation loss value that is much too high.

As a result, the user must make a simple conversion change from dB/km to dB/ft. To convert, the user must divide the provided specification by 3280 (number of feet in a kilometer).  For example, if the cable has a maximum attenuation loss of 0.4 dB/km, the value in dB/ft would be 0.000122.