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Ultrashort pulse sources are ubiquitous in scientific research as well as industrial applications. Delivering ultrashort pulses with high fidelity over a fiber-optic network to multiple target locations on a time-sharing basis can potentially overcome their complexity in operation and reduce overhead. We previously demonstrated a mechanism to deliver dispersion-compensated sub-400fs pulses in the C-band to different satellite locations using standard telecom-fiber links, as well as characterize them using a compact detector module at the delivery location assisted by a pulse shaper at the source, both controlled remotely via the cloud. The measurement procedure relied on creating a pulse pair with varying delays before launching them into the delivery fiber and measuring first and second-order autocorrelations at the remote location. However, this method proved inadequate to detect the optical nonlinearities as the spectral broadening seen by a pulse pair with varying delays differs from that of a pair of pulses undergoing nonlinear broadening separately since the degree of overlap between the pulses varies with the delay. To overcome this drawback, we propose to launch the variable-delay pulse pair with no temporal overlap to avoid combined nonlinear distortions and measure the autocorrelation at the output by adding a fixed delay interferometer to our detector module. The in-house fabricated fixed delay element consisted of a quartz plate, which provided a delay ≈ 11ps between the reflections from the front and back surfaces. Both surfaces were coated by custom-engineered partially reflecting semiconductor coatings to give ≈ 40% power in both reflections. The addition of the fixed delay element enables us to detect the spectral changes to the sub 400 fs pulses in the presence of nonlinearities in the delivery links using a compact detector module with no movable parts.
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