We present an optical fiber supporting 36 information bearing orbital angular momentum (OAM) states spanning 9 OAM orders. We introduce design techniques to maximize the number of OAM modes supported in the fiber; while avoiding LP mode excitation. We fabricate such a fiber with an air core and an annular index profile using the MCVD process. We introduce a new technique for shaping OAM beams in free-space to obtain better coupling efficiency with fiber with annular index profiles. We excite 9 orders of OAM in the fiber, using interferometry to verify the OAM state on exiting the fiber. Using polarization multiplexing and both signs for the topological charge, we confirm support of 36 states, exploiting to our knowledge the highest number of OAM modes ever transmitted in optical fiber.

This paper proposes an all-fiber fast optical frequency-hop code division multiple access (FFH-CDMA) for high-bandwidth communications. The system does not require an optical frequency synthesizer, allowing high communication bit rates. Encoding and decoding are passively achieved by strain-tunable fiber Bragg gratings. Multiple Bragg gratings replace a frequency synthesizer, achieving a hopping rate in tens of GHz. A main lobe sinc apodization can be used in writing the gratings to enhance the system capacity and the spectrum efficiency. All network users can use the same tunable encoder/decoder design. The simultaneous utilization of the time and frequency domains offers notable flexibility in code selection. Simulations show that the encoder efficiently performs the FFH spread spectrum signal generation and that the receiver easily extracts the desired signal from a received signal for several multiple access interference scenarios. We measure the system performance in terms of bit error rate, as well as autoto cross-correlation contrast. A transmission rate of 500 Mb/s per user is supported in a system with up to 30 simultaneous users at 10 09 bit error rate. We compare FFH-CDMA to several direct sequence-CDMA systems in terms of bit error rate versus the number of simultaneous users. We show that an optical FFH-CDMA system requires new design criteria for code families, as optical device technology differs significantly from that of radio frequency communications.

We report the first experimental realization of an all-optical temporal integrator. The integrator is implemented using an all-fiber active (gain-assisted) filter based on superimposed fiber Bragg gratings made in an Er-Yb co-doped optical fiber that behaves like an 'optical capacitor'. Functionality of this device was tested by integrating different optical pulses, with time duration down to 60 ps, and by integration of two consecutive pulses that had different relative phases, separated by up to 1 ns. The potential of the developed device for implementing all-optical computing systems for solving ordinary differential equations was also experimentally tested.

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A novel type of few-mode fiber, characterized by an inverse-parabolic graded-index profile, is proposed for the robust transmission of cylindrical vector modes as well as modes carrying quantized orbital angular momentum (OAM). Large effective index separations between vector modes (>2.1 × 10(-4)) are numerically calculated and experimentally confirmed in this fiber over the whole C-band, enabling transmission of OAM(+/-1,1) modes for distances up to 1.1 km. Simple design rules are provided for the optimization of the fiber parameters.

We propose a family of ring-core fibers, designed for the transmission of OAM modes, that can be fabricated by drawing five different fibers from a single preform. This novel technique allows us to experimentally sweep design parameters and speed up the fiber design optimization process. Such a family of fibers could be used to examine system performance, but also facilitate understanding of parameter impact in the transition from design to fabrication. We present design parameters characterizing our fiber, and enumerate criteria to be satisfied. We determine targeted fiber dimensions and explain our strategy for examining a design family rather than a single fiber design. We simulate modal properties of the designed fibers, and compare the results with measurements performed on fabricated fibers.

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