Impact Study of Multimode Fibre Taper in Modal Noise Under Restricted Offset Launch Conditions

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Qian, Chen
Multimode Fibre , Modal Noise
Delivering high bandwidth to the individual household or small business is currently a major bottleneck in the high speed network, a problem referred to as the last mile issue. Multimode fibre is widely deployed in the last mile for cost reasons. Recently, the tremendous high-speed data transport potential of multimode fibre has been demonstrated by utilizing offset launch techniques and a laser source. However, modal noise, caused by interference among the various propagating modes of a multimode fibre in the presence of mode selective loss, is a significant roblem when a laser source is employed. This thesis investigates several aspects of modal noise for what we believe to be the first time. By utilizing single mode fibre launching, modal noise is measured at different transverse offset launching positions with both continuous wave and pulse waveform input at several different fibre lengths. Modal noise is also measured for both waveforms in conjunction with a multimode optical fibre taper in an “in line” configuration, and timing jitter is investigated for the case of pulse waveform input. Performance improvements are found in some offset positions with the fibre taper in line.
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