copy - 8 - TR62221IEC:2012(E) a winding tension range from 1 N to 3 N, but different winding tensions could yield different with no crossovers in order to avoid negative influence on the correct winding force. 4.4 Relaxationtime Information about relaxation time should be given. Almost all fibres show some kind of coating relaxation effect,most probably dependant on the mechanical properties of the secondary winding and starting the attenuation measurement) less repeatable results may be obtained This relaxation time needs to be investigated by each user (depending on the particulal Reuters ( coating system tested). (Scientific), I Other mechanical relaxation issues (such as humidity and temperature)havebeenobserved such as the difference in storage temperature of the fibre spool and the winding/measurement cycling is an additional option in microbending testing. Inc., 4.5 Material used for fixed roughness For methods A and B a fixed roughness material is required that is single wide with only one grade 40 μm -mineral Al2O3). Reference measurements with known fibre are recommended to control quality of the measurement. downloaded on Nov-27-2014 by James Madison. No further reproduction o 4.6 Drum materials Any kind of material may be used for the drum used in methods B and D. The barrel shall uniform (seamless, smooth surface, constant diameter). The drum shall be of material showing high strength with a relaxation modulus that remains in 4.7 Drum material for temperature cycling Methods A, B and D can be used for temperature cycling tests.This requires a low therma expansion material (e.g. quartz drum). The size of the drum doesn't need fixed dimensions. It is recommended that the drum diameterbe at least 2oo mm tominimize macrobending effects. 5 Testprocedures 5.1 Method A: expandable drum 5.1.1 General This subclause describes a technique for the measurement of the loss increase due to fibres. This method may also be used to measure the microbending sensitivity of optical fibre ribbons. 5.1.2 Apparatus Uncontrolledwhen orderto avoid any loss contribution due to macrobending effects a minimum drum diameter of 2oo mm is recommended, see Figure 1. The curvature at any edges of the expanded material TR 62221 @IEC:2012(E) - 6 - lice segments of the drum also exceeds 2oo mm diameter. The drum surface is coated with a materialoffixed roughness(seesubclause4.5).Thelengthundertestshouldfit ontothe expandable drum.The winding pitch is controlled to prevent the fibre/ribbon turns from overlapping. RDemol While expanding thedrum,the fibre elongation is measured usingthe phase-shift method by Thomson (Method E of IEC 60793-1-22:2001).The attenuation measurement is conducted using either the cut back technique (method A of IEC 60793-1-40: 2001), the backscatter technique (methodCofIEC60793-1-40:2001)orbythedirecttransmittedpowermeasurement technique (method A of IEC 60793-1-46: 2001). Reuters (Scientific), Inc. ns .com dov ed EC2241/12 Figure 1-Set-up for expandable drum method used in an opticalfibretesting facility -20 14 by 5.1.3 Procedure Jam The fibre tobe testedis carefully woundonto the coated drum withminimal tension (e.g.0,4 Nto o,5N)in one singlelayer avoiding anycrossing or overlapping.Thefibreis fixed to avoid any relative slipping.While expandingthe drumthe changes in attenuation coefficient and phase are recorded. ison. No further 5.1.4 Calculations The fibre elongation()can be found from: reprodt xV (1) f×L or where 40 is the phase shift (degrees); f is the modulation frequency (Hz); L is the length of the sample (km); V is the constant depending on the photo-elastic coefficient (k),the speed of light in vacuum (c) and the group index (Ng): Uncontrolled when Copyr yrighted material l - 10 - TR 62221 @ IEC:2012(E) k×c (2) V : 360 Ng For Category B1 fibres, Vis typically 726 km/s/degree. Fromthisthe linearpressurePcanbe calculated T-EA (3) where T is the tension applied to the fibre (N); (Scientific), Inc., R is the radius