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22、ONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. TSB-145 TSB-145 RELIABILITY OF PASSIVE FIBER OPTIC COMPONENTS: FAILURE MODES AND MECHANISMS OF FIBER OPTIC CONNECTORS TIA FO 4.3 ABSTRACT The understanding of fiber optic connector reliability has progressed in several areas in recent y
23、ears. Although reliability models for measuring and predicting failure rates are lacking, failure mechanisms and their relationship to material properties, environmental conditions and design parameters are generally well known. A brief summary of failure mechanisms in common connector designs is di
24、scussed in this report produced by TIA Working Group FO 6.3.8. 1. Introduction Fiber optic connector products are sold and installed worldwide in volumes 10 to 100 million units per year. Despite the large numbers, most fall into one of a few basic designs and therefore have common failure modes. Th
25、is report reviews the subject of reliability of connectors from the standpoint of failure modes. Within that context, the following topics are addressed. Technology trends Applications Designs and materials Performance requirements and standards Failure mechanisms and analysis 2. General Connector a
26、ssemblies are single or multi- fiber devices consisting of fiber-terminating plugs and adapters (or receptacles). Their function is to provide remakeable connections between fiber ends 1TSB-145 or between fibers and packaged passive or active devices (e.g. couplers, splitters, wavelength division mu
27、ltiplexers, transmitters, receivers) to facilitate network reconfiguration. Since fiber terminating processes require carefully controlled polishing, tuning and measuring operations, they are generally carried out in a manufacturing facility. The resulting products are pre-connectorized cable assemb
28、lies (e.g. patch cords, preterminated building cables or preterminated cable panels) or packaged devices with adapters. Connectors are also sold as components, which can be assembled in the field with the appropriate tool kits and procedures. Connectors are used in all types of multimode (MM) and si
29、ngle mode (SM) fiber networks under operating conditions ranging from climate controlled building environments to uncontrolled outside plant conditions1,2,3. Some typical functions are: Connecting equipment to network in a central office or commercial building Cross connects in a central office or c
30、ommercial building telecommunication closet Connecting fibers to outside plant electronics equipment Connecting patch panels to hub or switch in commercial building Connections in outside plant patch panels, cabinets, pedestals and closures (above and below ground). Connecting outside cable plant to
31、 central office or premise network in a building basement For their intended environments, connectors must provide stable and repeatable connections with respect to physical function, insertion loss (IL or attenuation) and reflectance (or return loss, RL). Except for cases where components are desig
32、ned with fixed levels of attenuation for purposes of balancing power (attenuators), loss and reflectance are kept as low as is practicable. Maintenance of function and performance within acceptable limits in the above applications and environments is the basic reliability requirement for connectors.
33、 3. Designs and Technology trends Except for a very limited number of special applications, fiber optic connector designs are based on butt-joint fiber alignment. Most are single- or duplex- fiber devices using cylindrical ferrules (ceramic, metal or some combination) in the plug assembly and split
34、resilient alignment sleeves (ceramic, metal or polymer) in the adapter assembly. More recent designs employ cleaved fiber V-groove 2TSB-145 alignment with no ferrule. These exist as single or duplex variants as well. Multifiber connectors accommodating arrays from 2 to 12 fibers are used but in smal
35、ler quantities, today. Array style connectors are typically based on precision machining (or silicon v-groove) and polymer molding technologies. Regardless of the style, the design and manufacturing issues are non-trivial because submicron tolerances are generally required for low insertion loss pro
36、ducts. Applications of connectors, until fairly recently, have been limited primarily to controlled building or partially protected environments, but as noted below, that trend is changing. Industry standards covering designs, applications, and performance have been in existence or under development
37、 for many years, but have not fully evolved to a consistent and useful form with respect to defining, measuring and reporting reliability. In recent years, the following trends have evolved: A move toward designs which allow greater fiber density (e.g. Small Form Factor, SFF designs) An increase in
38、the use of injection molded plastics for ferrules and connector bodies An increase in designs and applications for duplex and multifiber variants Increased application in harsher outside environments Development and refinement of specialty or hybrid components These trends do not change the potentia
39、l failure modes of connectors but may alter the frequency of occurrence depending on the application 4. Design examples Table 1 lists representative examples of available connector designs covering some of the most commonly used styles and variants of cylindrical ferrule and array types. Two of thes
40、e are shown in figures 1 and 2. The relevant interface standards are developed within the International Electrotechnical Commission (IEC), Subcommittee 86B and the Telecommunications Industry Association (TIA), Subcommittee 6.3 to ensure mechanical intermateability between different vendor products
41、made to the same design. It is important to note that conformance to the 3TSB-145 appropriate interface standard affects, but does not guarantee, performance or reliability. TABLE 1: SOME COMMON CONNECTOR STYLES Designation Type/Fiber Count Interface Standard FC cylindrical ferrule-sleeve (2.5 mm) /
42、 simplex IEC 61754 -13 TIA/EIA-604-4A ST (BFOC 2.5) cylindrical ferrule-sleeve (2.5 mm) / simplex IEC 61754 -2 TIA/EIA-604-2 SC cylindrical ferrule-sleeve (2.5 mm)/ simplex - duplex IEC 61754 -4 TIA/EIA-604-4A MU cylindrical ferrule-sleeve (1.25 mm, SFF)/ simplex - duplex IEC 61754 -6 TIA/EIA-604-xx
43、 LC cylindrical ferrule-sleeve, (1.25 mm, SFF)/ simplex - duplex IEC 61754 -20 TIA/EIA-604-10 MPO (MTP) Multifiber array-pin alignment/2-12 IEC 61754 -7 MT-RJ Multifiber array pin alignment (SFF) 2-4 IEC 61754 - 8 TIA/EIA-604-11 4TSB-145 Figure 1. Cylindrical ferrule type connector, SC style PLUGPLU
44、GADAPTORFIBER RIBBONGROOVEHOOKGUIDE PINANGLEDCONNECTORFigure 2. Multi-fiber array type connector, MPO style 5TSB-145 All the designs in table 1 are based on adhesive bonding of fibers inside tightly toleranced ferrule capillaries and precision polishing of the ferrule endface to ensure fiber contact
45、 and accurate positioning. Some designs have tuning capability (active fiber core alignment) to minimize loss. Acceptable reflectance performance for most applications requires a PC (Physical Contact) ferrule finish. Some applications require further reduction of reflectance, which is achieved with
46、an APC (Angled Physical Contact) finish. Note: In Japan, APC may be used as an acronym for Advanced Physical Polish. There are other less common designs using innovative technologies including ferrule-less fiber alignment, index matching membranes, and features permitting termination without adhesiv
47、e bonding or polishing. Since these alternative technologies have had limited use and performance history, this paper will focus on the ferrule and array designs exemplified in table 1. 5. Critical features, parameters and conditions Alignment and positioning of fibers to achieve optical performance
48、 requires maintenance of tight tolerances on several ferrule dimensions and the endface geometry of the polished ferrule. . These are discussed here for the case of cylindrical ferrule designs4. There is work underway in IEC to develop the endface geometry requirements for array style connectors as
49、well. Ferrule Geometry (see figure 3): Ferrule and fiber geometry are the basic factors that impact the position of the fiber core in the finished connector. The position of the fiber core in the connector must be predictable so that the offset of the fiber core in a mated pair of connectors is small. This offset is the major factor insertion loss. The following ferrule requirements apply primarily to single-mode applications. Multimode requirements are similar but less stringent. 1. Outer diameter, roundness and cylindricity ( 0.5 m) 2. Hole diameter
