Optical fibres - Measurement methods and test procedures. Cut-off wavelength

Optical fibres - Measurement methods and test procedures. Cut-off wavelength

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What is BS EN 60793-1-44 - Optical fibres about?  

BS EN 60793 is a series on optical fibres. Optical fibres are cylindrical dielectric waveguide (nonconducting waveguide) that transmits light along their axis through the process of total internal reflection. BS EN 60793-1-44 establishes uniform requirements for measuring the cut-off wavelength of single-mode optical fibre, thereby assisting in the inspection of fibres and cables for commercial purposes. BS EN 60793-1-44 gives the methods for measuring the cut-off wavelength of fibre and cable.  

The test method in BS EN 60793-1-44 describes procedures for determining the cut-off wavelength of a sample fibre in either an uncabled condition (l c) or in a cable (l cc). Three default configurations are given here: any different configuration will be given in a detailed specification. These procedures apply to all category B and C fibre types (see Normative references).All methods require a reference measurement. There are two reference-scan techniques, either or both of which may be used with all methods: 

  • Bend-reference technique 
  • Multimode-reference technique using category a1 multimode fibre 

Who is BS EN 60793-1-44 - Optical fibres for? 

BS EN 60793-1-44 on optical fibres is useful for: 

  • Telecommunication component manufacturers 
  • Telecommunication equipment manufacturers 
  • Design engineers 
  • Quality control personnel 

Why should you use BS EN 60793-1-44 - Optical fibres 

The fibre consists of a core surrounded by a cladding layer, both of which are made of dielectric materials. BS EN 60793-1-44 describes two methods for measuring cable cut-off wavelength, l cc which is Method A: using uncabled fibre and Method B: using cabled fibre. All of the methods use the transmitted-power technique, which measures the variation with wavelength of the transmitted power of a fibre under test compared to a reference transmitted-power wavelength scan. The reference scan normalizes wavelength-dependent fluctuations in the measurement equipment so that the attenuation of the LP11 mode in the specimen can be properly characterized and the cut-off wavelength precisely determined. 

This procedure can determine the cut-off wavelength of a fibre specimen in either a cabled or uncabled condition. Each method has its own default configurations; BS EN 60793-1-44 will give any different configuration required. The fibre cut-off wavelength, (lc), measured under the standard length and bend conditions described in BS EN 60793-1-44, will generally exhibit a value larger than LCC. For normally installed cable spans, it is common for the measured lc value to exceed the system transmission wavelength. Thus, cable cut-off wavelength is the more useful description of system performance and capability. For short cables, e.g., a pigtail with a length shorter (and possibly a bending radius larger) than described in BS EN 60793-1-44, the cable may introduce modal noise near the cut-off wavelength when lossy splices are present (>0.5 dB). Using BS EN 60793-1-44 you can establish uniform requirements for measuring the cut-off wavelength of single-mode optical fibre, thereby assisting in the inspection of fibres and cables for commercial purposes.  

What’s changed since the last update?  

BS EN 60793-1-44:2011 supersedes BS EN 60793-1-44:2002. BS EN 60793-1-44:2011 includes a technical change with respect to BS EN 60793-1-44:2002: 

  • Withdrawal of Annex D