First Experimental Transmission over 50 m GI-POF at 40 Gb/s for Variable Launching Offsets

We show by BER measurements the first 40 Gb/s transmission over 50m GI-POF. The robustness towards launching offsets, polarisation changes and fibre bending is investigated for MMF and POF with 33GHz multi-mode coupled photo detector. Introduction Silica multi-mode fibre (MMF) and plastic optical fibre (POF) systems are characterized by easy handling and robustness towards strong bending compared to single mode fibre (SMF) systems. Therefore, both are promising candidates for the increasing market of high speed local area networks (LANs) and short optical interconnects in high performance computing (HPC) environment up to 40 Gb/s [1,2]. First experimental results based on eye diagrams were presented up to 40 Gb/s over GI-MMF [2] and up to 30 Gb/s over GI-POF [3]. However, all these publications were limited by multi-mode coupled photo detectors either with a small bandwidth or a small active detection area. For this type of fibre links, no BER measurements focused on the robustness towards launching offsets and polarisation changes were presented. In contrast to that, we are using a 33 GHz multi-mode coupled photo detector with an active detection area of 20 um diameter. This photo detector is the key element for our experimental investigation by BER measurements of robustness towards mode dispersion, polarisation and bending effects at a high data rate of 40 Gb/s over 50 m GIPOF and 100 m GI-MMF. Experimental Setup The experimental setup is shown in fig. 1. The light of the DFB laser (λ=1540 nm) is externally modulated by a Mach Zehnder Modulator (MZM). This is driven by a PRBS of length 2-1 with a data rate of 40 Gb/s (multiplexed in the electrical domain from 10 Gb/s to 40 Gb/s). Afterwards the signal is amplified by an EDFA and attenuated with a variable optical attenuator (VOA) to vary fibre input power. The polarisation of the signal can be changed with a polarisation controller. Variable restricted launch positions are realised by a micropositioner. Thereby, the light is launched with different offsets in horizontal as well as vertical direction from SMF (thin line) into the graded index MMF/POF (thick line). Afterwards, the signal is transmitted over 50 m GI-POF (loss: 14dB – would be reduced to 3 dB by transmitting at 1300 nm) or 100 m GI-MMF (loss: 0.5 dB; bandwidth at 1300 nm: 4 GHz km) with core diameters of 50 um. The signals are detected by a high speed (33 GHz 3 dB bandwidth) multi-mode coupled (50 um core, 1 m length) photo detector with an active area of 20 um diameter. This signal is afterwards amplified by an electrical amplifier (bandwidth: 48GHz; gain: 20dB). Bending influences for POF transmission are investigated by turning the fibre around a screw with a diameter of 8 mm. Finally, the robustness of the system is analysed after 1:4 demultiplexing in the electrical domain by a bit error ratio tester at 10Gb/s (measuring all four tributaries) or an oscilloscope. GI-MMF or 40 Gb/s Data