| 摘要 |
A laser provides the light source for an optical system connected to the fibre. An angle of arc is measured for which the far field pattern is reduced from a max. value by 25 dB. The electric field distributions, F(&thgr;), R(γ) for the far field pattern and near field pattern are related by F(&thgr;) which is proportional to integral between O and R(γ) Jo(Kγ Sin&thgr; )γ d γ where Jo is the zero order Bessel function, &thgr; is the radiation angle, K is the wave number, and r is the half radius of the fibre. Using the Hankel transform, the expression is derived for the near field pattern according to R(γ) is proportional to integral between O and F(&thgr;) Jo (Krsin &thgr;) sin2 &thgr; d &thgr;.
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