The measured spectral irradiance was multiplied wavelength by wavelength by the erythema action spectra.ResultsWe determined that the biologically effective solar spectrum remains essentially the same over the times of the day that sunburn may be experienced.

The purpose of the present study was to determine the variation of the biologically effective solar spectrum with the time of the day and the time of the year and to determine the variation of the shortest wavelength that contributes to the sunburn reaction with the time of the day and the time of the year.MethodsSpectroradiometric measurements were made at ground level over the period of one year (1988–1989) and at different times of the day at latitude 29.5° north. There have been many measurements of the variation of the solar spectrum with the time of the day and the time of the year, but questions remain as to the variation of the quality of the spectrum and the contribution of the shortest wavelengths of solar terrestrial radiation. In this way we may arrive at the weighted effectiveness of each wavelength of solar radiation to produce a sunburn reaction. This is often referred to as the fundamental mode cut-off, or bend edge.BackgroundBiologically effective solar ultraviolet radiation is defined as the product of the intensity of the solar spectrum and the erythema action spectrum at each wavelength. At wavelengths shorter than cut-off several optical modes may propagate - the fiber is multi-mode.Īs the cut-off wavelength is approached, progressively fewer modes may propagate until, at cut-off, only the fundamental mode may propagate - the fiber is then single-mode.Īt wavelengths longer than cut-off the guidance of the fundamental mode becomes progressively weaker, until eventually (usually at a wavelength several hundred nanometers above cut-off) the fiber ceases to guide - the fiber loses all optical function.The cut-off wavelength is the wavelength at which an optical fiber becomes single-mode.For example, if you are using a helium-neon laser, at 632.8nm, then you need HB600, while a 1550nm diode laser would call for HB1500. If you need Single Mode operation, you should choose the fiber type with the closest cut-off wavelength range below the operating wavelength of your optical source. HB450, SM600 etc.) typically represents the ‘nominal’ cut-off wavelength. When referring to Fibercore products, the number in the fiber product code (i.e. At wavelengths just below the cut-off, a few modes may be guided, whilst multi-mode fiber operates far below the second order cut-off point. Cut-off wavelength is important because, in most cases, it determines your choice of fiber type. The second order mode cut-off wavelength (commonly shortened to cut-off) refers to the wavelength above which the fiber is single-mode only at wavelengths above the cut-off will the fiber guide be single-mode.

Cut off wavelength