Optical switches represent an appealing option to address the upcoming scaling challenges facing electrical switches in data-center networks with the slowdown of Moore’s Law and the exponential increase in network demands posed by emerging cloud workloads. Wavelength switching based on tunable lasers and passive arrayed waveguide grating routers is a particularly promising technology for optical switching due to its amenability to fast switching and the passive nature of the core, which leads to lower power consumption and higher fault tolerance. We investigated the potential of this technology in the context of Sirius, a scalable, optically-switched network architecture for data centers, which can achieve ultra-fast switching time. At its core lies a novel tunable laser that can tune across wavelengths in less than 930 ps. The laser uses a disaggregated architecture where the carrier generation is separated from the wavelength tuning, which significantly reduces the wavelength tuning time compared to conventional tunable lasers. In this paper, we describe the different instantiations of this architecture that we developed and present the experimental evaluation.
Orbital angular momentum (OAM) beams, have attracted great attention in recent years. An OAM beam with a phase singularity is characterized by a helical phase front which provides an additional degree of freedom for wide amount of classical and quantum optical applications. However, despite many attempts to generate and manipulate OAM beams, a robust, reliable and scalable technique to directly address generation, multiplexing and low-loss transmission of the distinct OAM beams is still in great demand. Here, we review the development of all-fiber, ring core photonics lantern mode multiplexer to generate high quality OAM beams up to the second order within a broad spectral range of >550 nm. Our device is a 5-mode mode selective photonic lantern (MSPL) with an annular refractive index profile which is fully compatible with well-established ring core and vortex transmission fibers. Through the excitation of pairs of degenerate linearly polarized (LP) modes of the MSPL, we demonstrate the generation of high quality OAM beams up to the second order. In addition, we demonstrate multiplexing of two OAM modes (OAM+1+ OAM-2) to verify complex beam pattern generation of our all fiber devices. Furthermore, by splicing the end-facet of the photonic lantern to a ring core fiber, we achieve low-loss coupling of OAM modes while maintaining high contrast spiral phase patterns. These results demonstrate the potential of photonic lanterns for generating complex optical beams.
Recently, it has been demonstrated that by recovering the amplitude and phase of the backscattered optical signal, a ΦOTDR using pulse coding can be treated as a fully linear system in terms of trace coding/decoding, thus allowing for the use of tens of thousands of bits with a dramatic improvement of the system performance. In this communication, as a continuation of previous work by the same authors, a preliminary study aiming at characterizing the limits of the system in terms of maximum usable code length is presented. Using a code exceeding 1million bits over a duration of 0.26ms, it is observed that fiber optical path variations exceeding ≈π occurring over a time inferior to the pulse code length can lead to localized fading in the ΦOTDR trace. The occurrence, positions and form of the fading points along the ΦOTDR trace is observed to be strongly dependent on the type, frequency and amplitude of the perturbations applied to the fiber.
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