Page 142 - Optical Communications Essentials

Connectors and Splices

132 Chapter Eight

■ The letters SC were coined by NTT to mean subscriber connector or square
connector, although now the connectors are not known by those names.
■ A connector designed specifically for Fibre Channel applications was desig-
nated by the letters FC.
■ Since Lucent developed a specific connector type, they obviously nicknamed it
the LC connector; that is, LC can be considered an acronym for Lucent con-
nector, although it is not called a Lucent connector.
■ The letters MU were selected by NTT to indicate a miniature unit.
■ The designation MT-RJ is an acronym for media termination—recommended
jack.
■ The letters MPO were selected to indicate a multiple-fiber, push-on/pull-off
connecting function.

Table 8.1 summarizes several popular connector types and lists their main
features and applications. More details and illustrations are given below. The
optical SMA single-fiber connector is based on the electrical SMA connector
design and was one of the first to appear. To improve on the screw-on mounting
features of the SMA design, twist-on and snap-on single-fiber connectors such
as the ST, SC, and FC were devised. Further emphasis on reducing connector
sizes for higher packaging densities resulted in many concepts for small-form-
factor (SFF) single-fiber connector types, such as the LC, MU, and MT-RJ
designs. The biggest difference among the SFF connectors is whether they use
ceramic or plastic ferrules.
As their name implies, small-form-factor connectors have a small size. This is
important because as more fiber is being used in private networks, more elec-
tronics are being squeezed into smaller and smaller spaces. The SFF connectors
are designed for fast termination in the field, but most require special tool sets
for installation. SFF connectors also make smaller fiber network interface cards
(NICs) practical for computer workstations and servers. However, since there
are no standards for SFF connectors, network designers have the option to
choose the connector best suited for their needs.
Another recent development was the introduction of an inexpensive, high-
performance, compact multiple-fiber connector. These connectors save space by
providing up to at least 12 potential connections within a single ferrule that has
the same size as single-fiber SFF connectors. This means that one such multiple-
fiber connector can replace up to 12 single-fiber connectors. These components
are known by various acronyms such as MPO, MTP (trademark of US Conec),
and MPX.

ST connector. The ST connector, which is shown in Fig. 8.12, is very popular
for both data communication and telecommunication applications. It utilizes a
precision zirconia (zirconium dioxide) ceramic ferrule. For multimode fibers
this yields a typical insertion loss of 0.4dB when using a manual polishing

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