Dispersion-Diversity Multicore Fiber Signal Processing

Abstract

Beyond playing a primary role in high-capacity communication networks, multicore optical fibers can bring many advantages to optical and microwave signal processing, as not only space but also chromatic dispersion are introduced as new degrees of freedom. The key lies in developing radically new multicore fibers where the refractive index profile of each individual core is tailored properly to provide parallel dispersion-diversity signal processing with application in a variety of scenarios such as parallel channel equalization, analogue-to-digital conversion, optical computing, pulse generation and shaping, multiparameter fiber sensing, medical imaging, optical coherence tomography, broadband measurement instrumentation, and next-generation fiberwireless communications. Here, we experimentally prove, for the first time to our knowledge, reconfigurable two-dimensional dispersion-managed signal processing performed by a novel dispersiondiversity heterogeneous multicore fiber. The fiber comprises seven different trench-assisted cores featuring a different refractive index profile in terms of both radial geometry and core dopant concentration. As a representative application case, we demonstrate reconfigurable microwave signal filtering with increased compactness as well as performance flexibility and versatility as compared to previous technologies.

Photonic-Assisted Analog-to-Digital Conversion Based on a Dispersion-Diversity Multicore Fiber

“…being λ 0 the anchor wavelength where all the cores experience an identical group delay, τ n (λ 0 ) = τ 0 , n = 1, 2, …, N, and ΔD = Dn -Dn-1, n = 2, 3, …, N, the incremental chromatic dispersion between adjacent cores at λ 0 , [16,17]. For the photonic-assisted time-interleaved ADC to increase the sampling rate of the parallel electronic ADCs, f s , by a factor N, the DGD between cores must satisfy the relation…”

“…It comprises seven distinct trench-assisted cores drawn from seven different preforms and placed in a hexagonal disposition. The refractive index profile of each core was tailored independently to satisfy a common group delay at the anchor wavelength λ 0 = 1530 nm with linearly incremental chromatic dispersion values, D n , ranging from 14.3 to 20.3 ps/km/nm, respectively for cores 1 up to 7, with an incremental chromatic dispersion ∆D = 1 ps/km/nm, [17]. Table 1 gathers the design parameters of each core refractive index profile along with the measured chromatic dispersions.…”

“…Accounting for both the fiber link and the fan-in/fan-out devices, the measured total insertion losses range from 4.6 to 7.7 dB, while the measured inter-core crosstalk is below -26.9 dB at 1560 nm in the worst-case (cores 1 and 2). A complete experimental characterization of this MCF, including among others crosstalk time variation and spectra, influence of temperature on the fiber skew, and spectral chromatic dispersion behavior, can be found in [17].…”

“…We have previously proposed the exploitation of dispersiondiversity multicore fibers (MCF) [15] to provide parallel optical and microwave signal processing while the signal is being distributed with increased compactness and reduced power consumption, along with improved performance versatility and flexibility [16][17][18][19][20][21][22]. The so-called dispersion-diversity MCF involves tailoring "à la carte" the chromatic dispersion of each individual fiber core.…”

“…opens the way to a comprehensive range of dispersion-managed digital and analogue signal processing applications. Representative application scenarios include interferencecontrolled signal distribution in Multiple-Input Multiple-Output configurations, parallel chromatic dispersion compensation, time differentiation and integration, Fourier transformation, self-imaging phenomena (Talbot effects) to provide pulse repetition rate multiplication, waveform generation and shaping, optical beamforming for phased-array antennas, radiofrequency signal filters, instantaneous radiofrequency measurement and multicavity optoelectronic oscillation, among others [17].…”