R. Amezcua Correa

Compact fiber-optic curvature sensor based on super-mode interference in a seven-core fiber

A compact, low loss, and highly sensitive optical fiber curvature sensor is presented. The device consists of a few-millimeter-long piece of seven-core fiber spliced between two single-mode fibers. When the optical fiber device is kept straight, a pronounced interference pattern appears in the transmission spectrum. However, when the device is bent, a spectral shift of the interference pattern is produced, and the visibility of the interference notches changes. This allows for using either visibility or spectral shift for sensor interrogation. The dynamic range of the device can be tailored through the proper selection of the length of the seven-core fiber. The effects of temperature and refractive index of the external medium on the response of the curvature sensor are also discussed. Linear sensitivity of about 3000  nm/mm(-1) for bending was observed experimentally.

Visible supercontinuum generation in a graded index multimode fiber pumped at 1064 nm.

We observe efficient supercontinuum generation that extends into the visible spectral range by pumping a low differential mode group delay graded index multimode fiber in the normal dispersion regime. For a 28.5 m long fiber, the generated spectrum spans more than two octaves, starting from below 450 nm and extending beyond 2400 nm. The main nonlinear mechanisms contributing to the visible spectrum generation are attributed to multipath four-wave mixing processes and periodic spatio-temporal breathing dynamics. Moreover, by exploiting the highly multimodal nature of this system, we demonstrate versatile generation of visible spectral peaks in shorter fiber spans by altering the launching conditions. A nonlinearly induced mode cleanup was also observed at the pump wavelength. Our results could pave the way for high brightness, high power, and compact, multi-octave continuum sources.

All-fiber few-mode multicore photonic lantern mode multiplexer

The emergence of space division multiplexing (SDM) for ultrahigh capacity networks has heralded pioneering Petabit-class optical transmission systems. In parallel to novel SDM fibers, a new class of components to enable scalable, low-loss schemes for unlocking fiber capacity is being developed. In this work, an all-fiber mode selective photonic lantern mode multiplexer designed for launching into few-mode multicore fibers is demonstrated. This device is capable of selectively exciting LP01, LP11a and LP11b modes in a seven-core configuration, resulting in 21 spatial channels, with less than 38 dB core-to-core crosstalk and insertion loss below 0.4 dB. The multicore photonic lantern multiplexer is scalable to larger number of cores and modes per core, and can be easily integrated with emerging ultra-high bandwidth few-mode multicore optical communication systems.

Few-mode erbium-doped fiber amplifier with photonic lantern for pump spatial mode control

We demonstrate a few-mode erbium-doped fiber amplifier employing a mode-selective photonic lantern for controlling the modal content of the pump light. Amplification of six spatial modes in a 5 m long erbium-doped fiber to ∼6.2  dBm average power is obtained while maintaining high modal fidelity. Through mode-selective forward pumping of the two degenerate LP21 modes operating at 976 nm, differential modal gains of <1  dB between all modes and signal gains of ∼16  dB at 1550 nm are achieved. In addition, low differential modal gain for near-full C-band operation is demonstrated.

16QAM SDM-WDM Transmission over a Novel Hole-Assisted Few-Mode Multi-Core Fiber

A gross transmission rate of 204 Tbit/s is demonstrated over a novel 1 km hole-assisted step-index few-mode multi-core fiber with 7 cores, where each core allows the co-propagation of 3 spatial modes.

Space Division Multiplexing Fibers and Amplifiers

We report on the fabrication of multi-core multi-mode fibers tailored for optics communications applications. Examples of passive graded index fiber and active Er-doped multi-mode and multi-core fibers for ultra-high-density SDM will be discussed.

Gain-controlled erbium-doped fiber amplifier using mode-selective photonic lantern

For the first time, we demonstrate the implementation of a core pumped few mode erbium amplifier utilizing a mode selective photonic lantern for spatial modal control of the pump light. This device is able to individually amplify the first six fiber modes with low differential modal gain. In addition, we obtained differential modal gain lower than 1 dB and signal gain of approximately 16.17 dB at λs = 1550 nm through forward pumping the LP21 modes at λp = 976 nm.

Modal properties of photonic crystal fiber for high-power two μm fiber laser systems

Optical fibers that support single mode operation while achieving large mode areas are key elements for scaling up optical powers and pulse energies of fiber lasers. Here we report on a study of the modal properties of a new-generation of polarization maintaining large-mode-area photonic crystal fibers based on the spectrally and spatially resolved (S2) imaging technique. A fiber designed for Tm fiber laser system single mode operation in the 2μm spectral range is demonstrated for coiling diameters smaller than 40cm. At shorter wavelengths in the 1.3μm range, efficient higher order mode suppression requires tide coiling to about 20cm diameters.