A miniaturized short-reach active optical interconnect, taking advantage of collimated beam based optics, is presented, that features a superior structural tolerance. A receptacle type transmitter (Tx) and receiver (Rx) are introduced, to precisely interface with a standard multimode fiber in a flexible manner while they are efficiently operating based on equivalent collimated beams. In particular, the dependence of the tolerance and optical coupling upon the alignment of constituent elements is rigorously analyzed through ray optic simulations. Plastic injection molding was used to produce crucial parts associated with the optical modules; the arrangement tolerance for the components, such as VCSEL sources, photodetectors (PDs), fibers, and collimating/focusing lenses, was intensively investigated, by monitoring the beam patterns in conjunction with the optical coupling. A compact collimated beam was observed to be generated, providing a divergence of ~ 1.5°. The measured positional shift for the focused beam was found to be only below 10 μm, in response to a misalignment of over 300 μm between the collimating and focusing lens. Thanks to the proposed collimated beam optics, the overall 3-dB alignment tolerance was substantially enhanced to ~ 25 μm. The optical interconnect was finally completed by passively aligning the Tx and Rx modules, with an optical loss of ~ 2.9 and 0.85 dB for the VCSEL-to-fiber and fiber-to-PD coupling, respectively. Its feasibility was practically ensured by delivering a high speed digital signal at 2.5 Gb/s and moreover HD-SDI video data, over a 100-m long fiber.
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