E. M. Monberg

Seven-core multicore fiber transmissions for passive optical network

We design and fabricate a novel multicore fiber (MCF), with seven cores arranged in a hexagonal array. The fiber properties of MCF including low crosstalk, attenuation and splice loss are described. A new tapered MCF connector (TMC), showing ultra-low crosstalk and losses, is also designed and fabricated for coupling the individual signals in-and-out of the MCF. We further propose a novel network configuration using parallel transmissions with the MCF and TMC for passive optical network (PON). To the best of our knowledge, we demonstrate the first bi-directional parallel transmissions of 1310 nm and 1490 nm signals over 11.3-km of seven-core MCF with 64-way splitter for PON.

112-Tb/s Space-division multiplexed DWDM transmission with 14-b/s/Hz aggregate spectral efficiency over a 76.8-km seven-core fiber

We describe a new multicore fiber (MCF) having seven single-mode cores arranged in a hexagonal array, exhibiting low crosstalk among the cores and low loss across the C and L bands. We experimentally demonstrate a record transmission capacity of 112 Tb/s over a 76.8-km MCF using space-division multiplexing and dense wavelength-division multiplexing (DWDM). Each core carries 160 107-Gb/s polarization-division multiplexed quadrature phase-shift keying (PDM-QPSK) channels on a 50-GHz grid in the C and L bands, resulting in an aggregate spectral efficiency of 14 b/s/Hz. We further investigate the impact of the inter-core crosstalk on a 107-Gb/s PDM-QPSK signal after transmitting through the center core of the MCF when all the 6 outer cores carry same-wavelength 107-Gb/s signals with equal powers, and discuss the system implications of core-to-core crosstalk on ultra-long-haul transmission.

Amplification and noise properties of an erbium-doped multicore fiber amplifier

A multicore erbium-doped fiber (MC-EDF) amplifier for simultaneous amplification in the 7-cores has been developed, and the gain and noise properties of individual cores have been studied. The pump and signal radiation were coupled to individual cores of MC-EDF using two tapered fiber bundled (TFB) couplers with low insertion loss. For a pump power of 146 mW, the average gain achieved in the MC-EDF fiber was 30 dB, and noise figure was less than 4 dB. The net useful gain from the multicore-amplifier, after taking into consideration of all the passive losses, was about 23-27 dB. Pump induced ASE noise transfer between the neighboring channel was negligible.

Cladding-pumped erbium-doped multicore fiber amplifier

A cladding pumped multicore erbium-doped fiber amplifier for simultaneous amplification of 6 channels is demonstrated. Peak gain over 32 dB has been obtained at a wavelength of 1560 nm and the bandwidth measured at 20-dB gain was about 35 nm. Numerical modeling of cladding pumped multicore erbium-doped amplifier was also performed to study the properties of the amplifier. The results of experiment and simulation are found to be in good agreement.

Space-, wavelength-, polarization-division multiplexed transmission of 56-Tb/s over a 76.8-km seven-core fiber

We report the first experimental demonstration of space-division-multiplexed DWDM transmission of PDM-QPSK channels over a multicore fiber. A total capacity of 56-Tb/s (7×80×107-Gb/s) is transmitted over a 76.8-km seven-core-fiber with a record spectral-efficiency of 14-b/s/Hz.

Measuring higher-order modes in a low-loss, hollow-core, photonic-bandgap fiber

We perform detailed measurements of the higher-order-mode content of a low-loss, hollow-core, photonic-bandgap fiber. Mode content is characterized using Spatially and Spectrally resolved (S2) imaging, revealing a variety of phenomena. Discrete mode scattering to core-guided modes are measured at small relative group-delays. At large group delays a continuum of surface modes and core-guided modes can be observed. The LP11 mode is observed to split into four different group delays with different orientations, with the relative orientations preserved as the mode propagates through the fiber. Cutback measurements allow for quantification of the loss of different individual modes. The behavior of the modes in the low loss region of the fiber is compared to that in a high loss region of the fiber. Finally, a new measurement technique is introduced, the sliding-window Fourier transform of high-resolution transmission spectra of hollow-core fibers, which displays the dependence of HOM content on both wavelength and group delay. This measurement is used to illustrate the HOM content as function of coil diameter.

Scaling the effective area of higher-order-mode erbium-doped fiber amplifiers

We demonstrate scaling of the effective area of higher-order mode, Er-doped fiber amplifiers. Two Er-doped higher-order mode fibers, one with 3800 μm(2) A(eff) in the LP(0,11) mode, and one with 6000 μm(2) effective area in the LP(0,14) mode, are demonstrated. Output beam profiles show clean higher order modes, and S(2) imaging measurements show low extraneous higher order mode content. CW and pulsed amplifier experiments are reported. Nanosecond pulses are amplified to 0.5 mJ pulse energy with 0.5 MW peak power.

Multicore Erbium Doped Fiber Amplifiers for Space Division Multiplexing Systems

We report on the recent development of multicore fiber amplifiers suitable for amplifying space division multiplexed signals. We designed and constructed 7-core amplifiers, where the cores could be pumped individually or simultaneously through the cladding and studied the amplification and noise properties of these amplifiers. In the core-pumped amplifier, the net average gain was 25 dB, and noise figure was less than 4 dB. Using side-coupled cladding pumping, gain over 25 dB was obtained in each of the cores over a 40-nm bandwidth covering the C-band. We present results of numerical simulation that shows ways of further improvement of amplifier performance, including gain, noise figure, and power conversion efficiency (PCE) through optimization of fiber design.

Photo-induced SNAP: fabrication, trimming, and tuning of microresonator chains

We introduce multiple series of uncoupled and coupled surface nanoscale axial photonics (SNAP) microresonators along the 30 micron diameter germanium-doped photosensitive silica optical fiber and demonstrate their permanent trimming and temporary tuning with a CO2 laser and a wire heater. Hydrogen loading allows us to increase the introduced variation of the effective fiber radius by an order of magnitude compared to the unloaded case, i.e., to around 5 nm. It is demonstrated that the CO2 laser annealing of the fabricated microresonator chain can be used to modify the fiber radius variation. Depending on the CO2 laser beam power, the microresonator effective radius variation can be increased in depth up to the factor of two or completely erased. In addition, we demonstrate temporary tuning of a microresonator chain with a wire heater.

First demonstration of hollow-core fiber for intra data center low latency connectivity with a commercial 100Gb/s interface

For the first time 100Gb/s transmission using commercial low latency hardware is demonstrated over the longest manufactured hollow-core fiber (2.75km) to date, proving the feasibility of ultra-low latency intra-data center connectivity.