Specifications

Crestron DigitalMedia™ Design Guide
Check website (www.crestron.com) for product availability 23
CresFiber™
Crestron makes available a multimode fiber solution for DigitalMedia called CresFiber. It contains four strands of
50 micron multimode fiber for long distance transmission inside a single jacket. Two strands are used for DigitalMedia
and the other two strands are available for redundancy and expansion.
DigitalMedia fibers use high performance OM3 cores with an EMB rating of over 1000MHz-km at 850nm
to achieve long transmission distances.
CresFiber is easy to run and terminate for cable runs that are 300m (1000 ft) or less, and it is highly recommended for these
applications. CresFiber contains four fiber strands in a “breakout” cable formation; each strand has its own 3mm jacket with
strength members inside. This gives it the ability to be terminated directly to the DigitalMedia equipment, without requiring a
breakout kit, because each strand can support a large amount of tension.
 CRESFIBER-NP: CresFiber fiber optic breakout cable: (4)50/125 multimode fiber strands.
Available in 500 ft and 1000 ft spools.
 CRESFIBER-P: Plenum-rated version Available in 500 ft and 1000 ft spools.
Selecting Third Party Fiber (advanced)
Picking the correct fiber cabling for your application is a function of distance and the physical location of the cable. The optical
fiber (the part that carries the optical signal) determines the distance, and the jacket configuration depends on the application
(i.e. plenum, outdoor rating, number of fibers, etc). Either 50u or 62.5u multimode fiber may be used so long as the bandwidth
of the fiber is sufficient (see next section).
Selecting the Optical Fiber
Your selection of fiber cabling must have enough bandwidth to carry the DigitalMedia signals. The bandwidth of multimode
fiber is inversely proportional to the length of the fiber, because of the way multimode fiber works. The bandwidth of the fiber
is measured in Effective Modal Bandwidth (EMB), or MHz*km. For example, a 500MHz*km fiber can carry a 500MHz signal
1km, or a 250MHz signal 2km. Each fiber cable also has a different EMB rating at the two commonly used multimode
wavelengths, 850nm and 1300nm.
NOTE: The bandwidth of fiber cables are calculated based on several different standards put out by the TIA/EIA. This is
because the bandwidths vary slightly, depending on whether the light source is a laser or LED. DigitalMedia is a laser-based
fiber system, so the laser bandwidth should be used. This is sometimes referred to as RML BW (restricted mode launch
bandwidth) or EMBc (Effective Modal Bandwidth calculated).
The calculations must be done at both wavelengths to ensure there is enough bandwidth for each. The DigitalMedia
application requires the following bandwidth over fiber:
1200MHz @ 850nm
150MHz @ 1300nm