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Compared with backup sharing in WDM networks, it is more complex and challenging to share backup resources in OFDM-based optical networks with elastic bandwidth allocation. We propose and evaluate conservative and agressive backup sharing policies.

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Abstract:We propose a new WDM-PON architecture using Fabry-Pérot laser diodes (FP-LDs) that are injection-locked by continuous wave (CW) seed light. The modulation characteristics of the CW light injection-locked FP-LD are first investigated. Both uplink and downlink transmissions at 10 Gb/s are experimentally demonstrated using the proposed CW injectionlocked FP-LDs. It is shown that up to 16 laser cavity modes can be selectively injection-locked with side mode suppression ratio larger than 30dB. The effects of the location of FP-LD cavity modes, transmission distance, and injection wavelength detuning on the overall transmission performance are investigated. The possibility of eliminating polarization dependence of the proposed CW injection scheme is also experimentally demonstrated by properly configuring a depolarizer. The deployment cost for the proposed WDM PON is potentially low from the fact that the CW laser sources located at the central office can be shared by many WDMPONs and low-cost FP-LDs are used as light sources for data rates as high as 10 Gb/s.

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Additive manufacturing lends itself well to the manufacture of aerospace parts due to the high complexity and small volume of many components found in modern aero engines. By exploiting additive manufacturing design freedoms, enhanced part functionality can be achieved and lead time can be reduced. However, the integrity of these parts is a primary concern which often cannot be guaranteed with current generation additive manufacturing methods and materials. Studies on the performance of additively manufactured parts under service conditions are therefore required.In this study, laser powder bed fusion is used to produce specimens for creep testing. To allow this a novel specimen design, i.e. Two Bar Specimen, was applied for creep testing. The performance of these specimens, in the as-build condition, is showed to be largely poor because of surface integrity defects, in-built pores, and unfavourable microstructure formation. These are clearly highlighted and explored. Further specimens, subjected to heat treatments, have also been tested. These showed a marked improvement of the microstructure and hence creep performance. The lifetime of heat-treated samples was enhanced by as much as four times compared to the as-build specimens. However, this lifetime performance remains 33 percent below that of samples machined from the equivalent wrought material. This work then proposes manufacturing strategies to significantly enhance the performance of Inconel 718 when processed via laser powder bed fusion and post-heat-treatments.

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