Determination of mode power distribution in a parabolic-index optical fibers: Theory and application

Influence of mode coupling on mode group diversity multiplexing in multimode fibers

“…It was found that in terms of optical crosstalk, far field detection is preferable, when SI fibers are concerned, as the far field of the mode groups forms annular patterns (Stepniak 2007). On the other hand, the reception zone is irrelevant in case of GI fibers, as the far field of a GI fiber is a scaled version of its near field (Kitayama et al 1979). The drawback of far field detection is the huge size of detection area, which may restrict the photodiode's bandwidth.…”

“…It can be shown that the far field of a fiber L P µ,ν mode is given with the following transform (with accuracy to a certain constant amplitude) (Kitayama et al 1979)…”

A characterization method of a light source for multimode fiber transmission lines

“…The effective coupled power is calculated from the modal power distribution at the sending end. A simple method with assumptions [Daido et al, 1979] and precise methods with w•ide applicability [Stewart, 1979;Kitayama et al , 1979] are reported as for the measurement of the modal •ower distribution in fibers. The simple method is justified when the following three assumptions are satisfied: (1) the power distribution among the mode group with the same propagation constant is uniform, (2) a large number of modes is excited so that the calculation of near-field patterns using geometrical optics is reasonable, and (3) the phases of modes are random with one another.…”

“…It is apparent from this table that a longer fiber has to be used for a narrower spectral width. As a shorter fiber is preferable for the convenience of measurement, the more general methods [Stewart, 1979;Kitayama et al, 1979] have to be used for the semiconductor laser with a spectral width narrower than the limiting value at the fiber length of 10 m.…”

Mode-matched phase diffractive optical element for detecting laser modes with spiral phases

“…Typically, the modal distribution is estimated by visual inspection, but such inspection is inadequate for most applications that involve sensitive optical sensors [8,9], feedback loops in adaptive optics, and diagnostics of temperature induced changes in high power lasers, as well as for laser beam characterization [7,10]. Other far field image processing techniques for extracting modal composition suffer from nonlinearities, have limited dynamic range, and involve complicated time consuming digital processing [11,12]. Still other techniques involve high quality computer generated diffractive optical elements (DOEs), designed by efficient iterative or cell oriented procedures for converting a complex transmittance function into a phase function (encoding) [4,6,7,10,[13][14][15][16][17].…”