Notice the size difference of the
two fiber connectors on the right. The last connector
has a 1.25mm ceramic ferrule while its neighbor has
a 2.5mm ferrule. These are all simplex (1 fiber) connectors.
Left - a duplex LC with two
simplex LC connectors in a clipped, duplex form. There
are two 1.25mm ceramic ferrules in this duplex connectors.
Ceramic ferrules for fiber optic connectors for the LC
and MU connectors are 1.25 mm in diameter while ferrules
for ST, SC, ESCON, FDDI and FC connectors are 2.5mm in
diameter.
Diameter is 1.25mm for LC ceramic ferrules and 2.5mm for
SC, ST, ESCON, FC connectors.
The MT-RJ connector uses a duplex
MT ferrule. This ferrule is unique in that there
is only one ferrule but with two holes for the glass.
Note that there are two large holes visible in the
color photo. The actual optical glass fibers are
loated between these larger holes and are not visible
in this photo. These large holes are the guide-pin
holes. The guide-pins are used to align the ferrules
when mated. When the pins are inserted in the ferrule,
this is called a "male" connector. An
MT-RJ connector with no pins is called a "female"
MT-RJ.
The lower left photo shows the ferrules only as
they mate. The actual MT-RJ ferrule must be inserted
in a housing in order to latch.
Other ferrules
are availabe in the MT ferrule family, with up to 72 fibers
per ferrule.
Coupler / Adapter Designs:
In order to mate non-matching connectors or ferrules, couples
and adapters must be used. Depending on the connectors involved,
mating non-matching connectors can range from low cost, and
easily done, to higher cost. In some cases, direct coupling
of different connectors is impossible due to fiber spacing or
physical dimensions.
A duplex ESCON to dual ST coupler
is shown.
A duplex SC to dual ST coupler is
shown.
Issue arise when converting from LC to SC due to the difference
in spacing between the LC connectors and SC connectors as well
as the need for different alignment sleeve dimensions.
Alignment Sleeve (shown as transparent)
The purpose of the alignment sleeve is to guide the two ferrule
tips together and to align them so that light passes between
the optical glass in ferrule #1 and ferrule #2.
For the MT-RJ connector, the adapter is a mechanical piece that
holds the two ferrules in contact. The actual alignment is achieved
through the metal pins supplied in the male MT-RJ connector.
As can be seen, converting from a 2.5mm ferrule diameter to
a 1.25mm ferrule requires a more complex alignment sleeve design.
For example, an LC to SC adapter would require a special multi-sized
alignment sleeve. This design is being developed and should
be available to the optics market soon.
