Experimental demonstration of multi-cavity optoelectronic oscillation over a multicore fiber

Abstract

We report, for the first time to our knowledge, the experimental demonstration of multi-cavity optoelectronic oscillators where the cavities are provided by the different cores of a multicore fiber. We implemented two multi-cavity architectures over a 20-m-long 7-core fiber link: unbalanced dual-cavity oscillation (the cavity lengths are a multiple of a reference value) and multi-cavity Vernier oscillation (the cavity lengths are slightly different). Since all the cavities are hosted under a single fiber cladding and are subject to the same environmental and mechanical conditions, optoelectronic oscillators built upon multicore fibers benefit from improved performance stability as compared to independent singlemode fiber cavities.

Microwave Signal Processing over Multicore Fiber

“…There, we show how homogeneous MCFs allow for two different OEO architectures, highly unbalanced dual-cavity operation (the cavity lengths are a multiple of a reference value) and multi-cavity vernier operation (the cavity lengths are slightly different), where moderate and long cavity lengths (>2 m) are compatible with a high-spectral purity and multi-GHz oscillation mode spectral separation. The experimental demonstration of both multicavity architectures was reported for the first time in [59] over a 20-m-long commercial homogeneous MCF link. This MCF comprises seven cores and is characterized by a cladding diameter of 125 µm, a core separation of 35 µm and a core mode field diameter of 6.4 µm.…”

“…In essence, a short loop provides the required spectral separation between adjacent oscillating modes while a long loop is responsible for the spectral purity. The number of loops can as well be generalized to an arbitrary number [54][55][56][57]59]. In concrete, the work reported in [54] experimentally demonstrated three-cavity OEOs by using three different single-mode fiber links whose lengths were multiple of a given reference value.…”

“…Setup for the experimental demonstration of a multi-cavity Vernier optoelectronic oscillator over a seven-core homogeneous fiber. PC: polarization controller; RF: radiofrequency; EOM: electrooptic modulator; VDL: variable delay line; EDFA: Erbium-doped fiber amplifier; VOA: variable optical attenuator; PD: photodetector (blue: optical path; red: electrical path) [59].…”

“…. ) where ∆τ is the incremental delay between cavities that produces the Vernier effect [59]. Figure 9a shows the measured RF spectrum for the three-cavity Vernier OEO where we matched the oscillating modes of all three cavities at the frequency located near 4.494 GHz.…”

“…If the dispersion parameter D in each core is a multiple of a basic value ΔD (incremental dispersion parameter), the oscillation frequency for a core with a length L is given by [55]: Phase Noise (dBc/Hz) Figure 9. Experimental oscillation spectra of a multi-cavity Vernier optoelectronic oscillator using a 20-m seven-core fiber for: (a) dual-versus triple-loop operation; and (b) three consecutive oscillation modes for the triple-loop operation [59]. Figure 10 shows the measured phase noise spectrum for the three-cavity Vernier architecture (compared to the two-cavity Vernier architecture), where we observe a −85 dBc/Hz phase noise level at a 10-KHz offset from the carrier that decreases down to −130 dBc/Hz for a 1-MHz offset.…”