A variety of optical fiber connectors are available. Typical connectors are rated for 500-1000 mating cycles.[1] The main differences among types of connectors are dimensions and methods of mechanical coupling. Generally, organizations will standardize on one kind of connector, depending on what equipment they commonly use, or per type of fiber (one for multimode, one for single-mode). In datacom and telecom applications nowadays small form factor connectors (e.g., LC) and multi-fiber connectors (e.g., MTP) are replacing the traditional connectors (e.g., SC), mainly to pack more connectors on the overcrowded faceplate, and thus reducing the footprint of the systems.
According to Telcordia Generic Requirements for Single-Mode Optical Connectors and Jumper Assemblies, optical fiber connectors are used to join optical fibers where a connect/disconnect capability is required. The basic connector unit is a connector assembly. A connector assembly consists of an adapter and two connector plugs. Due to the sophisticated polishing and tuning procedures that may be incorporated into optical connector manufacturing, connectors are generally assembled onto optical fiber in a supplier’s manufacturing facility. However, the assembly and polishing operations involved can be performed in the field, for example, to make cross-connect jumpers to size.
Optical fiber connectors are used in telephone company central offices, at installations on customer premises, and in outside plant applications. Their uses include:
* Making the connection between equipment and the telephone plant in the central office
* Connecting fibers to remote and outside plant electronics such as Optical Network Units (ONUs) and Digital Loop Carrier (DLC) systems
* Optical cross connects in the central office
* Patching panels in the outside plant to provide architectural flexibility and to interconnect fibers belonging to different service providers
* Connecting couplers, splitters, and Wavelength Division Multiplexers (WDMs) to optical fibers
* Connecting optical test equipment to fibers for testing and maintenance.
Outside plant applications may involve locating connectors underground in subsurface enclosures that may be subject to flooding, on outdoor walls, or on utility poles. The closures that enclose them may be hermetic, or may be “free-breathing.” Hermetic closures will subject the connectors within to temperature swings but not to humidity variations unless they are breached. Free-breathing closures will subject them to temperature and humidity swings, and possibly to condensation and biological action from airborne bacteria, insects, etc. Connectors in the underground plant may be subjected to groundwater immersion if the closures containing them are breached or improperly assembled.
Contents
[hide]
* 1 Types
o 1.1 Notes
o 1.2 Mnemonics
* 2 Analysis
* 3 Testing
* 4 See also
* 5 References
* 6 External links
[edit] Types
FC connector
MIC (FDDI) connector
LC connector (duplex version)
LuxCis connector
MT-RJ connector
SC connector (duplex version)
ST connector
TOSLINK connector
Fiber connector types Short name↓ Long form↓ Coupling type↓ Ferrule diameter↓ Standard↓ Typical applications↓
Avio (Avim) Screw Aerospace and avionics
ADT-UNI Screw 2.5 mm Measurement equipment
Biconic Screw 2.5 mm Obsolete
D4 Screw 2.0 mm Telecom in the 1970s and 1980s, obsolete
Deutsch 1000 Screw Telecom, obsolete
DIN (LSA) Screw IEC 61754-3 Telecom in Germany in 1990s; measurement equipment; obsolete
DMI Clip 2.5 mm Printed circuit boards
E-2000 (AKA LSH) Snap, with light and dust-cap 2.5 mm IEC 61754-15 Telecom, DWDM systems;
EC push-pull type IEC 1754-8 Telecom & CATV networks
ESCON Enterprise Systems Connection Snap (duplex) 2.5 mm IBM mainframe computers and peripherals
F07 2.5 mm Japanese Industrial Standard (JIS) LAN, audio systems; for 200 μm fibers, simple field termination possible, mates with ST connectors
F-3000 Snap, with light and dust-cap 1.25 mm IEC 61754-20 Fiber To The Home (LC Compatible)
FC Ferrule Connector or Fiber Channel [1] Screw 2.5 mm IEC 61754-13 Datacom, telecom, measurement equipment, single-mode lasers; becoming less common
Fibergate Snap, with dust-cap 1.25 mm Backplane connector
FSMA Screw 3.175 mm IEC 60874-2 Datacom, telecom, test and measurement
LC Lucent Connector [1], Little Connector, or
Local Connector[citation needed] Snap 1.25 mm IEC 61754-20 High-density connections, SFP transceivers, XFP transceivers
LuxCis 1.25 mm ARINC 801 PC or APC configurations (note 3)
LX-5 Snap, with light- and dust-cap IEC 61754-23 High-density connections; rarely used
MIC Media Interface Connector Snap 2.5 mm Fiber distributed data interface (FDDI)
MPO / MTP Multiple-Fibre Push-On/Pull-off [1] Snap (multiplex push-pull coupling) 2.5×6.4 mm [2] IEC-61754-7; EIA/TIA-604-5 (FOCIS 5) SM or MM multi-fiber ribbon. Same ferrule as MT, but more easily reconnectable.[2] Used for indoor cabling and device interconnections. MTP is a brand name for an improved connector, which intermates with MPO.[3]
MT Mechanical Transfer Snap (multiplex) 2.5×6.4 mm Pre-terminated cable assemblies; outdoor applications[2]
MT-RJ Mechanical Transfer Registered Jack or Media Termination - recommended jack [1] Snap (duplex) 2.45×4.4 mm IEC 61754-18 Duplex multimode connections
MU Miniature unit [1] Snap 1.25 mm IEC 61754-6 Common in Japan
NEC D4 Screw 2.0 mm Common in Japan telecom in 1980s
Opti-Jack Snap (duplex)
OPTIMATE Screw Plastic fiber, obsolete
SC Subscriber Connector [1] or
square connector [1] or
Standard Connector Snap (push-pull coupling) 2.5 mm IEC 61754-4 Datacom and telcom; extremely common
SMA 905 Sub Miniature A Screw typ. 3.14 mm Industrial lasers, military; telecom multimode
SMA 906 Sub Miniature A Screw Stepped; typ. 0.118", then .089"[citation needed] Industrial lasers, military; telecom multimode
SMC Sub Miniature C Snap 2.5 mm
ST / BFOC Straight Tip[1] / Bayonet Fiber Optic Connector Bayonet 2.5 mm IEC 61754-2 Multimode, rarely single-mode; APC not possible (note 3)
TOSLINK Toshiba Link Snap Digital audio
VF-45 Snap Datacom
1053 HDTV Broadcast connector interface Push-pull coupling Industry-standard 1.25mm diameter ceramic ferrule Audio & Data (broadcasting)
V-PIN V-System Snap (Duplex) Push-pull coupling Industrial and electric utility networking; multimode 200 μm, 400 μm, 1 mm, 2.2 mm fibers
[edit] Notes
1. Modern connectors typically use a "physical contact" polish on the fiber and ferrule end. This is a slightly curved surface, so that when fibers are mated only the fiber cores touch, not the surrounding ferrules. Some manufacturers have several grades of polish quality, for example a regular FC connector may be designated "FC/PC" (for physical contact), while "FC/SPC" and "FC/UPC" may denote "super" and "ultra" polish qualities, respectively. Higher grades of polish give less insertion loss and lower back reflection.
2. Many connectors are available with the fiber endface polished at an angle to prevent light that reflects from the interface from traveling back up the fiber. Because of the angle, the reflected light does not stay in the fiber core but instead leaks out into the cladding. Angle-polished connectors should only be mated to other angle-polished connectors. Mating to a non-angle polished connector causes very high insertion loss. Generally angle-polished connectors have higher insertion loss than good quality straight physical contact ones. "Ultra" quality connectors may achieve comparable back reflection to an angled connector when connected, but an angled connection maintains low back reflection even when the output end of the fiber is disconnected.
3. Angle-polished connections are distinguished visibly by the use of a green strain relief boot, or a green connector body. The parts are typically identified by adding "/APC" (angled physical contact) to the name. For example, an angled FC connector may be designated FC/APC, or merely FCA. Non-angled versions may be denoted FC/PC or with specialized designations such as FC/UPC or FCU to denote an "ultra" quality polish on the fiber endface.
4. SMA 906 features a "step" in the ferrule, while SMA 905 uses a straight ferrule. SMA 905 is also available as a keyed connector, used e.g., for special spectrometer applications.
5. E-2000 and F-3000 are registered trademarks of Diamond SA, Switzerland. ST is a registered trademark of AT&T/Lucent Technologies.
[edit] Mnemonics
* LC connectors are sometimes called "Little Connectors".[citation needed]
* MT-RJ connectors look like a miniature 8P8C connector — commonly (but erroneously) referred to as RJ-45.
* ST connectors refer to having a "straight tip", as the sides of the ceramic (which has a lower temperature coefficient of expansion than metal) tip are parallel—as opposed to the predecessor bi-conic connector which aligned as two nesting ice cream cones would. Other mnemonics include "Set and Twist", "Stab and Twist", and "Single Twist",[citation needed] referring to how it is inserted (the cable is pushed into the receiver, and the outer barrel is twisted to lock it into place). Also they are known as "Square Top" due to the flat end face.[citation needed]
* SC connectors have a mnemonic of "Square Connector", and some people believe that to be the correct name.[1] This refers to the fact the connectors themselves are square. Another term often used for SC connectors is "Set and Click" or "Stab and Click".[citation needed]
[edit] Analysis
* FC connectors' floating ferrule provides good mechanical isolation. FC connectors need to be mated more carefully than the push-pull types due to the need to align the key, and due to the risk of scratching the fiber endface while inserting the ferrule into the jack. FC connectors have been replaced in many applications by SC and LC connectors.[4]
* There are two incompatible standards for key widths on FC/APC and polarization-maintaining FC/PC connectors: 2 mm ("Reduced" or "type R") and 2.14 mm ("NTT" or "type N").[5] Connectors and receptacles with different key widths either cannot be mated, or will not preserve the angle alignment between the fibers, which is especially important for polarization-maintaining fiber. Some manufacturers mark reduced keys with a single scribe mark on the key, and mark NTT connectors with a double scribe mark.
* SC connectors offer excellent packing density, and their push-pull design reduces the chance of fiber endface contact damage during connection; frequently found on the previous generation of corporate networking gear, using GBICs.
* LC connectors are replacing SC connectors in corporate networking environments due to their smaller size; they are often found on small form-factor pluggable transceivers.
* ST connectors have a key which prevents rotation of the ceramic ferrule, and a bayonet lock similar to a BNC shell. The single index tab must be properly aligned with a slot on the mating receptacle before insertion; then the bayonet interlock can be engaged, by pushing and twisting, locking at the end of travel which maintains spring-loaded engagement force on the core optical junction.
* In general the insertion loss should not exceed 0.75 dB and the return loss should be higher than 20 dB. Typical insertion repeatability, the difference in insertion loss between one plugging and another, is 0.2 dB.
* On all connectors, cleaning the ceramic ferrule before each connection helps prevent scratches and extends the connector life substantially.
* Connectors on polarization-maintaining fiber are sometimes marked with a blue strain relief boot or connector body, although this is far from a universal standard. Sometimes a blue buffer tube is used on the fiber instead.[6]
* MT-RJ (Mechanical Transfer Registered Jack) uses a form factor and latch similar to the RJ-45 connectors. Two separate fibers are included in one unified connector. It is easier to terminate and install than ST or SC connectors. The smaller size allows twice the port density on a face plate than ST or SC connectors do. The MT-RJ connector was designed by AMP, but was later standardized as FOCIS 12 (Fiber Optic Connector Intermateability Standards) in EIA/TIA-604-12. There are two variations: pinned and no-pin. The pinned variety, which has two small stainless steel guide pins on the face of the connector, is used in patch panels to mate with the no-pin connectors on MT-RJ patch cords.
* Hardened Fiber Optic Connectors (HFOCs) and Hardened Fiber Optic Adapters (HFOAs)
Hardened Fiber Optic Connectors (HFOCs) and Hardened Fiber Optic Adapters (HFOAs) are passive telecommunications components used in an Outside Plant (OSP) environment. They provide drop connections to customers from fiber distribution networks. These components may be provided in pedestal closures, aerial and buried closures and terminals, or equipment located at customer premises such as a Fiber Distribution Hub (FDH) or an Optical Network Terminal or Termination (ONT) unit.
These connectors, which are field-mateable, and hardened for use in the OSP, are needed to support Fiber to the Premises (FTTP) deployment and service offerings. HFOCs are designed to withstand climatic conditions existing throughout the U.S., including rain, flooding, snow, sleet, high winds, and ice and sand storms. Ambient temperatures ranging from –40°C (–40°F) to +70°C (158°F) can be encountered.
Telcordia GR-3120, Issue 2, April 2010, Generic Requirements for Hardened Fiber Optic Connectors (HFOCs) and Hardened Fiber Optic Adapters (HOFAs), contains the industry’s most recent requirements for HFOCs and HFOAs.
[edit] Testing
This section may need to be wikified to meet Wikipedia's quality standards. Please help by adding relevant internal links, or by improving the section's layout. (February 2011)
Glass fiber optic connector performance is affected both by the connector and glass. In an otherwise perfect-looking assembled connector, typical adverse factors include: connector (ferrule) concentricity tolerance, fiber diameter tolerance, fiber core concentricity tolerance (within the fiber), core optical parameter tolerance, stress in the polished fiber causing excess return loss, fiber "pistoning" eg lengthwise movement (usually poor glue), incorrect shaping of the connector tip as a result of polishing. It can be readily seen that the connector manufacturer has little control over many of these, so in-service performance may well be below the manufacturer's specification for these reasons.
Testing fiber optic connector assemblies falls into two general categories: factory testing and field testing.
Factory testing is sometimes statistical, eg a process check. For example a profiling system may be used to ensure that the overall polished shape is correct, and a good quality optical microscope to check for blemishes. Optical Loss / Return Loss performance is checked using specific reference conditions, eg against a "reference standard" single mode test lead, or using an "Encircled Flux Compliant" source for multi mode testing. Testing and rejection ("yield") may represent a significant part of the overall manufacturing cost.
Field testing is usually simpler. A special hand-held optical microscope is used to check for dirt or blemishes, and an optical time-domain reflectometer may be used to identify significant point losses or return losses. A power meter and light source or loss test set may also be used to check end-to-end loss.
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