1、 TIA TELECOMMUNICATIONS SYSTEMS BULLETIN ITM-24 Fiber Break Source Analysis TSB-62.24 APRIL 2004 TELECOMMUNICATIONS INDUSTRY ASSOCIATION The Telecommunications Industry Association represents the communications sector of NOTICE TIA Engineering Standards and Publications are designed to serve the pub
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23、to a license agreement. For information, contact: Global Engineering Documents 15 Inverness Way East Englewood, CO 80112-5704 U.S.A. or call U.S.A. and Canada 1-800-854-7179, International (303) 397-7956 ITM-24 Fiber break source analysis Contents Forewordiii 1. Introduction1 2. References .2 3. App
24、aratus.2 4. Sampling and Specimens3 5. Procedure3 6. Calculations or Interpretation of Results.6 7. Documentation7 Annex A Establishing the mirror radius constants .9 Annex B Comparison with IEC and ITU documentation 11 TIA-TSB-62-24 ii This page left blank. TIA-TSB-62-24 iii ITM-24 Fiber break sour
25、ce analysis Foreword This Informative Test Method comes from TIA Project No. 3-0121, and was formulated under the cognizance of TIA FO-4.6, Subcommittee on Optical Fibers and Materials, and of FO-4.6.2, Working Group on fiber reliability and coatings. This ITM is part of the series of informative te
26、st methods included within TIA/EIA-TSB-62. There are two informative Annexes. Key Words: Fiber failure stress, break end, Break Source Analysis (BSA), radius, chord, mirror, mist TIA-TSB-62-24 ivTIA-TSB-62-24 1 ITM-24 Fiber break source analysis 1 Introduction 1.1 Intent This procedure is intended t
27、o determine the approximate break stress that caused fracture of an optical fiber. 1.2 Scope Break Source Analysis (BSA) is a diagnostic tool intended to ascertain the break stress causing failure of optical fibers. 1.3 Background Fracture behavior in glasses has been studied extensively, and the us
28、e of BSA to determine the mode of failure is common practice. During the fracture process, the crack grows from its original flaw size until it approaches terminal velocity, at which point the surface becomes increasingly roughened by mist, hackle, and eventually crack branching. The mirror region i
29、s the smooth portion of the crack surface that is surrounded by the mist and hackle. A schematic of a fracture surface is illustrated in Figure 1. Figure-1: Features of the fracture surface TIA-TSB-62-24 2The distance from the origin to the mirror-mist boundary is related to the level of stress on t
30、he fiber at failure. 1.4 Limits of usefulness This technique is usually limited to break stress failures at or below approximately 125 kilopounds per square inch (kpsi) and above 25 kilopounds per square inch. The measurement is limited to the case when break-ends have been properly preserved. The m
31、irror measurement method described in Section 5 is limited to the cases of pure tension. The cases of combined tension and bending or torsion remain under study. The calculation to estimate fracture stress in the presence of bending can lead to an underestimation of the actual applied stress at fail
32、ure. 2 References The following documents are references. FOTP-13 (EIA/TIA-455-13A) Visual and mechanical inspection of fiber optic components, devices, and assemblies FOTP-28 (EIA/TIA-455-28B) Method for measuring tensile failure point of optical waveguide fibers FOTP-57 (EIA/TIA-57B) Optical fiber
33、 end preparation and examination 3. Apparatus 3.1 Equipment An optical or electron microscope capable of 200 power magnification (200x) or greater, equipped with incident and transmitted illumination sources, camera attachments, and measurement reticules. Calibrate the microscope and reticule using
34、an object with features of known dimensions at each magnification level. TIA-TSB-62-24 3 3.2 Materials Required materials include paper wipes or the equivalent, a suitable chemical coating stripping agent, tape, isopropyl alcohol or other suitable agent, and mounting fixtures for horizontal (side) a
35、nd vertical (end-on) viewing. 4. Sampling and specimens The specimen is both halves (if available) of the fiber that broke. Lengths of fiber near the break, sufficient to provide mounting in the microscope (typically 20 cm) should be taped to a card that also provides for identifying information, in
36、cluding which end broke. Specimen cards should be stored or transported in a way that does not alter the break ends. 5. Procedure 5.1 Initial inspection Remove the fibers from the specimen card and macroscopically inspect with a low magnification eyepiece or viewer. Note any obvious damage. 5.2 Vert
37、ical microscopic examination Remove enough fiber from the side away from the break source to put the remainder into a holding fixture for examination with the microscope. Starting with the lowest magnification, examine the area near the break for signs of damage. If there is debris on the fiber, rem
38、ove it by sticky tape or ultrasonic cleansing. If possible, complete the measurement of the mirror surface dimensions according to clause 5.5. It may, however, be necessary to remove the coating before this can be done. In this case, complete the horizontal inspection before coating removal. At this
39、 stage of inspection, it may also be possible to identify whether the break was due to bending or torsion. A bending induced break will produce a mirror surface that is cupped and somewhat elliptical in shape. A torsion induce break TIA-TSB-62-24 4will produce a surface that is not at all perpendicu
40、lar to the axis of the fiber. Figure 2 shows an example of such a break. Figure 2 Break with bending present 5.3 Horizontal microscopic examination Place the fiber into a holding device that allows a horizontal inspection with rotation. Rotating the fiber, note any additional signs of damage. At thi
41、s stage it should be possible to confirm a torsion break. 5.4 Remove the coating Chemically strip the coating from the break-end. If necessary, remove any additional coating debris with sticky tape or ultrasonic cleansing. 5.5 Mirror surface measurements This procedure is only appropriate for tensio
42、n breaks where the fracture surface is perpendicular to the fiber axis and non-concave. Figure 1 shows such a surface. This surface shows four main features: - Mirror region - Mist region - Hackle region - Break source The regions are created by the evolution of the fracture after it has achieved cr
43、itical velocity. The mist and hackle regions occur at post-critical velocities that are so extreme that the growth at the flaw front becomes chaotic. The dimension TIA-TSB-62-24 5 of the mirror region is related to the applied stress at the time of failure. The larger the mirror, the lower the appli
44、ed stress. When the applied stress at failure is large, the velocity needed for chaotic growth occurs sooner and the resulting mirror surface is reduced. When the mirror is too small to measure (failure stress larger than about 125 kpsi) or when the mirror covers the entire surface of the break end
45、(failure stress less than about 25 kpsi), this procedure cannot be used. If either of these conditions exist, note which condition is present. There are two methods of characterizing the dimension of the mirror region: - Radius method - Chord method Both these methods can be somewhat affected by the
46、 necessity of distinguishing the boundary between the mirror region and the mist region. This can be somewhat subjective, but as a general rule, the boundary exists prior to any obvious sign of mist. The mirror method is the more classic method used originally in bulk glasses. The chord method may b
47、e more appropriate for fibers (which are round) and more robust with regard to small bending effects. Because of the subjectivity regarding the mirror boundary the calibration procedure of Annex A is recommended. 5.5.1 Radius method For this method, the dimension, r, from the break source to the mir
48、ror boundary directly across the fiber end is measured with the microscope reticule and reported. See Figure 3. TIA-TSB-62-24 6Figure 3 Radius method TIA-TSB-62-24 7 5.5.2 Chord method The edge of the mirror intersects the edge of the fiber end at two locations that are symmetrically located about t
49、he position of the break source. See figure 4. This dimension is measured then divided by two to obtain the half-chord, c, which is reported. Figure 4 Chord method 6 Interpretations of results and calculations 6.1 Break stress calculation for tension The first order relationship of failure stress to mirror dimension was originally der
