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Fiber cut-off bølgelængde

2021-10-25
Fiberafskæringsbølgelængden er for at sikre, at der kun findes én tilstand i fiberen.
En af de vigtigste transmissionskarakteristika for single-mode fiber er cut-off bølgelængden, som er af stor betydning for fiberoptiske kabelproducenter og brugere af fiberoptiske kabler til at designe og bruge fiberoptiske transmissionssystemer.

The normal transmission mode of single-mode fiber is linear polarization mode, (including two orthogonal modes). The so-called cut-off wavelength refers to the cut-off wavelength of higher-order modes (including four degenerate modes composed of two circular polarization modes and two orthogonal modes). The operating wavelength of the single-mode optical fiber transmission system must be greater than the cut-off wavelength, otherwise, the optical fiber will work in the dual-mode area. Due to the existence of modes, mode noise and multi-mode dispersion will be generated, which will lead to the deterioration of transmission performance and the reduction of bandwidth. Figure 1 shows the eigenfunctions and curves of a single fiber, as well as the refractive index profile distribution. It can be seen from Figure 1 that the working area of a single-mode fiber is:

Normaliseret frekvens


I formlen er a kernens radius, er kernens og beklædningens brydningsindeks, og λ er arbejdsbølgelængden. V=2,4048 er afskæringsværdien for modulet. Når den optiske fibers strukturelle parametre er tidsindstillet, er afskæringsbølgelængden for den optiske fiber:


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