IEC 60793-1-34-2021 pdf free.Optical fibres – Part 1-34: Measurement methods and test procedures – Fibre curl.
Two methods are recognized for the measurement of fibre curl, in uncoated optical fibres:
• method A: side view microscopy:
• method B: laser beam scattering.
Both methods measure the radius of curvature of an uncoated fibre by determining the amount of deflection that occurs as an unsupported fibre end is rotated about the fibres axis. Method A uses visual or digital video methods to determine the deflection of the fibre while method B uses a line sensor to measure the maximum deflection of one laser beam relative to a reference laser beam.
By measuring the deflection behaviour of the fibre as it is rotated about its axis and understanding the geometry of the measuring device, the fibres radius of curvature can be calculated from simple circular models, the derivation of which are given in Annex C.
Both methods are applicable to type B optical fibres as described in IEC 60793 (all parts). Method A is the reference test method, used to resolve disputes.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60793 (all parts), Optical fibres
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http:/lwww.electropedia.orgl
• ISO Online browsing platform: available at http://www.iso.org/obp
4.1 Principle
An uncoated fibre end is mounted in a rotatable fixture so that the end extends freely into space by an overhang distance which will depend on the measurement device. The overhang distance is from the fibre fixture to the free endface of the uncoated fibre. The measurement distance from the fibre fixture to the measurement point is typically 10 mm to 20 mm, and the measurement point shall be close to the fibre’s free endface. If the measurement device is designed with measurement distances greater than this, care shall be taken to avoid excessive degradation due to effects of vibration and gravity. The fibre is rotated and the deviations in the position of the test point relative to a reference position are measured to obtain the fibre’s radius of curvature, r.
Details pertaining to the two methods are given in the relevant Annex A or Annex B. Common apparatus requirements are given in 4.2 to 4.5.
4.2 Fibre holding fixture
Provide a fixture that holds the fibre on a constant axis at the holding position and allows the fibre to be rotated through 360°. The fixture may be a v-groove holder such as a vacuum chuck or a fibre ferrule. If a ferrule is used, take care to ensure that the inside diameter is sized closely enough to the fibre diameter to minimize variability in the deflection measurements.
4.3 Fibre rotator
Provide a device to grip and rotate the fibre through 360°. The device may be manually operated, or it may be driven by a rotational device such as a stepper motor.
4.4 Deflection measurement device
Provide a deflection measurement device according to either Annex A or Annex B.
4.5 Computer (optional)
A computer may be used to provide motion control, data collection and computation.
5 Sample preparation
Use an uncabled fibre of appropriate length for the instrument design. Remove enough coating from one end to allow mounting in the fibre fixture with the necessary overhang. The fibre should not extend much past the measuring device’s required measurement distance since excessive lengths can cause degradation as discussed in 4.1.IEC 60793-1-34 pdf download.