Information Technology Reference
In-Depth Information
In addition, some of the new connector implementations now use a pretermi-
nated connector arrangement. As you may know, one of the most time-consuming
steps in conventional fiber optic connector assembly is the polishing of the end of the
terminated fiber that pokes through the tip of the fiber connector. One style of preter-
minated connector has a built-in prepolished fiber stub at the tip of the connector.
The bare fiber strand is inserted through the back of the connector and into a
special “matching fluid” that closely matches the index of refraction of both fiber
pieces. The result is that the usual deflection of the incident light rays that would
occur at an angled fiber end is essentially absent. Instead, the beam passes into the
matching fluid and then into the fiber stub with virtually no refraction, eliminating
a very time-consuming step from the assembly process. An alternative process uses
an index-matched optical-quality sphere to minimize the light dispersion at the end
of the fiber and direct it to the prepolished fiber stub.
However, there is sometimes a price to pay in using the quick-termination fiber
connectors. A standard cut-and-polish fiber termination normally has a lower con-
nector loss than the quick-termination type.
Small Form Factor (SFF) Connectors.
The small form factor (SFF) connector is a
very new type of fiber-optic connection. Although the SC connector met the push-
pull and duplex criteria, it was a large connector that required two adjacent slots in
a modular faceplate. Patch panels had to be completely redesigned to fit this con-
nector, and it prevented the high-density arrangement needed for fiber blades
(option cards) in switches, hubs, and routers. The concept of the SFF connector was
put forth to remedy this size problem.
The SFF connector is generally defined as a fiber-optic connector that termi-
nates two fiber connections within the form factor of a single insert in a modular
jack plate. This arrangement generally complies with the requirement to align a
duplex fiber connection. The TIA-568-C.3,
Optical Fiber Cabling Components
Standard
, drops the requirement for a specific connector on the basis that this will
encourage innovation and that the market will determine usage. The connector can
be of any configuration that meets certain requirements and does not have to be
exactly like the copper modular (RJ-type) connector. Figure 11.5 shows some of the
more popular SFF connector types in contrast to the conventional 568SC connector.
There are two major requirements that must be met by any SFF connector that
complies with TIA-568-C.3. First, the alignment of the optical components must
meet the applicable FOCIS
5
document. Second, the connector must allow the two-
5
FOCIS, Fiber Optic Connector Intermateability Standard, ANSI/TIA/EIA-604-3, sets standards for
optical alignment and loss for single-mode plugs, multimode plugs, and adapters.
