23/09/2021 Fiber Optic Connector Identifier

The
Fiber Optic Association - Tech Topics
 

Connector
Identifier
 In
the development of fiber optic  
technology over the last 35
years, many
companies and individuals have invented
the
"better mousetrap" - a fiber optic
connector that was lower
loss, lower cost,
easier to terminate or solved some other
perceived problem. In all, about 100 fiber
optic connectors
have been introduced to
the marketplace, but only a few
represent
the majority of the market. Here is a
rundown of
the connectors that have been
the leaders of the industry.

Design
Most fiber optic connectors are plugs or
so-called male
connectors with a
protruding ferrule that holds the fibers
and
aligns fibers for mating. They use a mating
adapter to
mate the two connector ferrules
that fits the securing
mechanism of the
connectors (bayonet, screw-on or snap-in.) From
the top: LC, SC,
The ferrule design is also useful as it can Biconic, Deutsch 1000
be used to
connect directly to active
devices like LEDs, VCSELs and
detectors.

History
The big silver connector at the bottom of
the photo at the
right is the Deutsch 1000,
what was probably the first
commercially
successful fiber optic connector. It was
really
a "pin vise" holding a stripped fiber.
The nose piece is
spring loaded and was
pushed back when the connector was
inserted into a mating adapter. The fiber
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stuck out into a

drop of index matching
fluid on a plastic lens. This
solution was
state of the art in the late 70s, yielding
about 3 dB loss. Many users remember it
as the connector on
the front panel of the
original Tektronix OTDR.

Above
it is the Biconic, the yellow body
indicating a SM version.
Developed by a
team led by Jack Cook at Bell Labs in
Murray
Hill, NJ, the Biconic was molded
from a glass-filled plastic
that was almost
as hard as ceramic. It started with the
fiber
being molded into the ferrule. This lasted
until the
company could get a 125
micron/5mil pin insert into the
plastic mold,
at which point the fiber was glued into the
ferule with epoxy. When singlemode
versions first appeared,
the ferrules were
ground to center the fiber core in the
Connector
color codes: L>R, Multimode,
ferrule to reduce loss. Since it was not Singlemode, SM APC
keyed and could
rotate in the mating
adapters, it had an airgap between the
ferrules when mated, meaning loss was
never less than 0.3 dB
due to fresnel
reflection. Usually MM Biconics had losses
of
0.5-1 dB and SM 0.7 dB or higher.

The
advent of the ceramic ferrule in the
mid-80s in Japan
changed the connector
designs forever. The ceramic ferrule
was
hard and precise. Fibers were accurately
located for
alignment and ferrules could be
allowed to touch. Adding in
convex ferrules
for PC (physical contact) between
connectors
reduced losses to levels below
0.3 dB for both MM and SM
varieties.

In
the late 90s, small form factor (SFF)
connectors became
popular, but only the
LC (top) has been a runaway success,
both in telcos and high bit rate LANs,
SANs, etc.

Below
are some more of the popular
connectors over the years.

Connector
Standards
The most popular connectors are covered
in the
TIA connector intermateability
standards FOCIS-x
(TIA-604-x).
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Color
Codes:
Since
the earliest days of fiber optics,
orange, black or gray
was multimode and
yellow singlemode. However, the advent
of
metallic connectors like the FC and ST
made color
coding difficult, so colored
boots were often used. The
TIA 568 color
code for connector bodies and/or boots is
Beige
for multimode fiber, Blue for
singlemode fiber,
and Green for
singlemode APC (angled) connectors.
More
on fiber optic connector and cable
color codes.

NOTE:
THIS MAKES A GOOD
STUDY GUIDE FOR THE FOA
CFOT AND
CFOS/C EXAMS!
 

Guide
to Fiber Optic Connectors

Check
out the "spotters guide" below and
you will see the most
common fiber optic
connectors. (All the photos are to the
same
scale, so you can get an idea of the
relative size of
these connectors.)
If you wonder what the connector names
mean, see Fiber
Optic Connector
Terminology in The
FOA Online Reference
Guide to Fiber Optics.  

 ST
 ST
(an AT&T Trademark)
was probably still  most
popular connector for
multimode networks until
~2005. It has
a bayonet
mount and a long cylindrical
2.5 mm ceramic
(usually)
ferrule to hold the fiber. Most  
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ferrules are
ceramic, but
some are metal or plastic. A
mating adapter is
used to
mate two connectors (shown
below.) And because STs
are
spring-loaded, you have to
make sure they are seated
properly. If you have high
loss, reconnect them to see if
it
makes a difference.

The
ST/SC/FC/FDDI/ESON
connectors have the same
ferrule size -
2.5 mm or about
0.1 inch - so they can be
mixed and
matched to each
other using hybrid mating
adapters. This
makes it
convenient to test, since you
can have a set of
multimode
reference test cables with ST
or SC connectors
and adapt
to all these connectors. See
below.

ST is covered in the TIA

connector
intermateability
standard FOCIS-2
(TIA-604-
2).

SC
SC
is a snap-in connector
also with a 2.5 mm ferrule
that is
widely used for it's
excellent performance. It was
the
connector standardized in
TIA-568-A, but was not
widely used
at first because it
was twice as expensive as a
ST. Now it's
only a bit more  
expensive and much more
common It's a
snap-in
connector that latches with a
simple push-pull
motion. It is
also available in a duplex
configuration.

SC is covered in the TIA

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connector
intermateability
standard FOCIS-3
(TIA-604-
3).

FC
FC
was one of the most
popular singlemode
connectors for many
years. It
also uses a 2.5 mm ferrule,
but some of the early
ones
use ceramic inside stainless
steel ferrules. It screws
on
firmly, but you must make  
sure you have the key
aligned
in the slot properly
before tightening. It's been
mostly
replaced by SCs and
LCs.

FC is covered in the TIA

connector
intermateability
standard FOCIS-4
(TIA-604-
4).

Mating
Dissimilar
Connectors
The ST, SC and FC
connectors share a 2.5 mm
ferrule design so
they can
be mated to each other. To
do so requires a hybrid
mating adapter as shown
here.

From the top:

ST>FC
SC>FC
SC>ST

In the past, you could also

get hybrid adapters for
these
connectors to FDDI
and ESCON
connectors
(see below)
which used the
same ferrule.

 LC
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LC
is a small form factor
connector that uses a 1.25
mm
ferrule, half the size of
the SC. Otherwise, it's a
standard
ceramic ferrule
connector, easily terminated
with any
adhesive. Good
performance, highly favored
for singlemode.
 
The
LC, MU and LX-5 use
the same ferrule but cross-
mating
adapters are not easy
to find.

LC is covered in the TIA

connector
intermateability
standard FOCIS-10
(TIA-604-
10).

LX-5
LX-5
is like a LC but with a
shutter over the end of the
fiber.

LX-5 is covered in the TIA

connector
intermateability
standard FOCIS-13
(TIA-604-  
13).

MU
MU
looks a miniature SC with
a 1.25 mm ferrule. It's more
popular in Japan and the far
east.

MU is covered in the TIA

connector
intermateability
 
standard FOCIS-17
(TIA-604-
17).

MPO
MPO
is a 12 fiber connector
for ribbon cable, often called
an
array connector. The
connector ferrule is plastic
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and
contains 12 or 16 fibers
in a row. The versions with 12
fiber rows can theoretically
have 6 rows but more than
two
are rare. The 16 fiber
rows are limited to 2 rows.
Fiber
ferrule alignment is by
pins in one ferrule and holes
in the
other.

The
MPO main use is for  
preterminated cable
assemblies and
cabling
systems. Here is a 12 fiber
MT broken out into 12
STs. It
is also used for higher speed
multimode links (40 or
100Gb/s) that use parallel
optics.

MPO means multi-position

optical. This connector is
sometimes called a MTP
which is a commercial name.
It is
covered in the TIA
connector intermateability
standard FOCIS-5
(TIA-604-
5) for the 12 fiber version and
FOCIS-18
for the 16 fiber
version..

For
more information on the
MPO connector, including its
issues
with polarity and
testing, go
here.
 

Military
or
Ruggedized 
Connectors

There are many styles of

ruggedized connectors, mostly
developed for tactical military use
but are now widely used in
field
applications that call for rugged
cables and connectors,
applications such as oil and gas
exploration or use at sporting
events by TV networks. These
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connectors are generally

multifiber
connectors and some
use expanded beam connector
technology for
its resistance to
dirt and harsh environments.
Examples of these
connectors
are the MIL-C-38999, TFOCA
and Hughes.

New
Generation
Connectors

Introduced
Circa 2017-
2019

There were
few new connectors
introduced between 2000 and
2017. But there
have been
several new connectors that are
designed for small
size, making
the duplex LC in the middle look
quite large. The
Senko CS on the
left is a duplex connector using
the LC 1.25mm
ferrule. The SN
on the right also is a duplex
connector using
1.25mm ferrules
but it uses a vertical format. The
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salient
feature of these
connectors is panel or
transceiver density. The
CS is
horizontal and has about twice
the density of a LC. The
vertical
format SN doubles even the CD
density in horizontal
panel space
and the mating adapter is hardly
any higher.

Similar to the SENKO is the US

Conec MDC which appears to
have been designed to a similar
requirement.

Two expanded beam connectors

have been introduced to compete
with the MPO array connector,
from 3M Expanded beam and the
R&M QXB. Expanded beam
connectors have fewer problems
with
alignment and dirt but their
higher cost has limited their CS (L) and
SN (R) connectors with a duplex LC
acceptance.

These
connectors are new and
future commercial success is an
unknown.

US Conec MDC

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Obsolete
Connectors
Deutsch
1000
Deutsch
1000 was probably
the first commercially
successful fiber
optic
connector. It was really a "pin
vise" holding a
stripped fiber.
The nose piece is spring
loaded and was
pushed back
when the connector was  
inserted into a mating
adapter. The fiber stuck out
into a drop of index matching
fluid on a plastic lens. This
solution was state of the art
in
the late 70s, yielding about 3
dB loss. Many users
remember it as the connector
on the front panel of the
original Tektronix OTDR.

SMA
Amphenol
developed the
SMA from the "Subminiature
A" hence SMA,
microwave
connector. The model 905
had a machined ferrule
exactly 1/8 inch in diameter
that mated in a machined
adapter. When the adapters  
were not precise enough for
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better fibers, a necked-down

ferrule that mated with a
Delrin adapter for better
insertion loss performance.
These
connectors are still in
use on some military and
industrial
systems.

BICONIC
This
is the Biconic, the yellow
body indicating a SM version
-
MMs were usually black.
Developed by a team led by
Jack Cook
at Bell Labs in
Murray Hill, NJ, the Biconic
was molded from
a glass-
filled plastic that was almost  
as hard as ceramic.
It started
with the fiber being molded
into the ferrule.
This lasted
until the company could get a
125 micron/5mil
pin insert
into the plastic mold, at which
point the fiber
was glued into
the ferule with epoxy. When
singlemode
versions first
appeared, the ferrules were
ground to center
the fiber
core in the ferrule to reduce
loss. Since it was
not keyed
and could rotate in the mating
adapters, it had an
airgap
between the ferrules when
mated, meaning loss was
never less than 0.3 dB due to
fresnel reflection. Usually MM
Biconics had losses of 0.5-1
dB and SM 0.7 dB or higher.

Jack
Cook retired from Bell
Labs, obtained a license from
AT&T and started Dorran
Photonics to make Biconic
connectors which later
became 3M fiber optics.

Biconic is covered in the TIA

connector
intermateability
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standard FOCIS-1
(TIA-604-
1).

NEC
D4
The
NEC D4 was probably
the first connector to use
ceramic or
hybrid
ceramic/stainless steel
ferrules. It uses a smaller
ferrule than SCs or FCs. It
was widely used in telco
networks in the 80s to early  
90s and some may still be in
use.

AMP
OPTIMATE
The
AMP Optimate was
popular in the early 80s. It
used a conical
plastic ferrule
and screw-on nut. It was
available for every
fiber size
including plastic fiber. Some
may still be in use
in utility
and industrial systems.  

FDDI
- ESCON
Besides
the SC Duplex, you
may occasionally see the
FDDI and ESCON*
duplex
connectors which mate to
their specific networks.
They
are generally used to connect
to the equipment from a
wall
outlet, but the rest of the  
network will have ST or SC
connectors. Since they both
use 2.5 mm ferrules, they can
be
mated to SC or ST
connectors with adapters.

FDDI
- above - has a fixed
shroud over the ferrules

ESCON
- below - the
shroud over the ferrules is
spring-loaded and
retracts

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*ESCON is an IBM trademark

MT-RJ
MT-RJ
is a duplex connector
with both fibers in a single
polymer
ferrule. It uses pins
for alignment and has male
and female
versions.
Multimode only, field
terminated only by
prepolished/splice method.

MT-RJ is covered in the TIA

connector
intermateability
standard FOCIS-12
(TIA-604-
12).

MT-RJ,
Volition and Opti-Jack
(below) are difficult
connectors to
test, as most
test sets do not allow direct
adaptation to
the connector. If
you have to use hybrid (ST or
SC to MT-RJ)
reference
cables, you cannot do a
Method B (one jumper
reference) insertion loss test.
Usually the solution is to
do a
three cable (Method C)
reference.

Volition
3M's
Volition is a slick,
inexpensive duplex connector
that uses
no ferrule at all. It
aligns fibers in a V-groove
like a
splice. Plug and jack
versions, but field terminate
jacks
only.

Volition is covered in the TIA

connector
intermateability
standard FOCIS-7
(TIA-604-
7).

Opti-Jack
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The
Panduit Opti-Jack is a
neat, rugged duplex
connector
cleverly designed
aournd two ST-type ferrules
in a package
the size of a RJ-
45. It has male and female
(plug and jack)
versions.

Opti-Jack is covered in the

TIA connector
intermateability
standard FOCIS-6
(TIA-604-
6).

And
More...

And there were more - TRW built

a connector that had an internal
mechanical splice, Kodak
entered the game with with the
LAMDEK,
an expanded beam
connector using molded lens
technology from
their cameras
and many more - more than 100
by our count!

Here is a list of some of the fiber

optic connectors of the past
taken from a listing of fiber optic
connector adapters for FOTEC
fiber optic power meters:

AMP
Optimate single fiber
connector
SMA ( 905
& 906 Style,
NATO Standard)
Augat OK
& CL Series
H-P
HFBR-4000
H-P
HFBR-0500
AMP
Optimate DNP
Deutsch
1000
Deutsch
4000
Siecor
ITT
FOT/OCN 101/201
WECO LB1B

Biconic:WECO
LA1A,
Dorran,Auto Conn,OFTI
NRC fiber
holder
Bare
fiber adapter
Radiall
F705-017-000
Switchcraft

Diamond,
Interoptics
Stratos,
Holtek
Hughes
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NEC D4
GTE
Expanded Beam
Hughes
Contact
AMP
Optimate Duplex
Deutsch
6000 Expanded
Beam
Plessey
Plessey
Ferrule
NTT FC
LEE TEC
Single Mode
Amphenol
Bayonet
G+H/Breechlok
Contact
Sumitomo
Mini BNC
Deutsch
3000, Expanded
Beam SMA
AT&T
ST
Lamdek
(Kodak)
Philips
2000 Series
Radiall
Optoball F-714
Seimens
LWL (DIN 47255)
Socapex
ITT
FOSCLN5C
AT&T
Rotary Splice
T&B
Ansley (Plastic Fiber)
Amphenol
Mini Bayonet
(906-200-5000)
Radiall
VFO 710
Diamond
Interoptic Din
Cannon
duplex (FOTC)
FDDI
Duplex
Serti
Bayonet Biconic
Sony
Seiko
Methode
Size 16 Contact
Dupont
Duplex
TELLAB/MOLEX

IBM
DUPLEX
NTT SC-P

NTT SC2-P

European
RACE 
Diamond
ES2000
Amphenol
MFM
H-P
HFBR-4516
AMP Mini
DNP
Siemens
SV400
F07
Duplex
Panduit
OptiJack
MIL-T029504/14
Lucent LC
MT-RJ
3M
Volition

 Also
see Fiber
Optic Connector Terminology and The
FOA Online
Reference Guide to Fiber Optics.  
 
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(C) 2019 The Fiber

Optic Association, Inc.

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