| 摘要 |
The invention relates to an optical transmitter which consists of a laser module and a connecting lead with a graded-index fibre (7) to which a plug part (12) is connected at one end. When the graded-index fibre (7) is fully excited, damping of the high modes is produced in the plug. This causes modal (speckle) noise on the transmission link. This disturbance is avoided in accordance with the invention by suppressing the excitation of high modes from the outset. For this purpose, a short piece of step-index fibre (6) is spliced (8) onto the graded-index fibre (7). The core radius of the piece (6) of step-index fibre is smaller than the core radius of the graded-index fibre (7). The numerical aperture of the piece (6) of step-index fibre is always smaller than that of the graded-index fibre (7). This produces an excitation of the graded-index fibre (7) which is reduced by 70% with regard to the high modes. <IMAGE>
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