All nonlinear effects are dependent upon the intensity of the electromagnetic field in the medium. However, it is the total optical power entering and leaving the fibre that is usually measured. Some method is required for converting between the two when comparing theoretical and experimental results. The effective area parameter has been defined for this purpose and is based on the distribution of the electromagnetic field in the core of the fibre.

As part of the development of a traceable measurement service, we have recently completed an assessment of four techniques for measuring effective area. A summary of the theory of effective area and the measurement techniques used in our investigation is available: "Effective Area of Optical Fibres - Definition and Measurement Techniques" ( PDF, 132 kB).

Topics:

• The Definition of Effective Area and Relationship to Mode Field Diameter
• The Direct Far-Field (DFF) Technique
• The Variable Aperture in the Far-Field (VAFF) Technique
• The Near-Field Scanning (NFS) Technique
• The Transverse Offset (TO) Technique