Electro-opto-mechanical radio-frequency oscillator driven by guided acoustic waves in standard single-mode fiber

TL;DR

This paper demonstrates a novel opto-electronic RF oscillator using guided acoustic waves in standard fiber, achieving stable 319 MHz oscillations with high mode suppression without RF filtering.

Contribution

It introduces a new fiber-based opto-electronic oscillator leveraging guided acoustic modes for stable RF generation without additional filtering.

Findings

Oscillates at 319 MHz matching acoustic resonance.

Suppresses competing acoustic modes by at least 40 dB.

Achieves single longitudinal mode oscillation with narrow linewidth.

Abstract

An opto-electronic radio-frequency oscillator that is based on forward scattering by the guided acoustic modes of a standard single-mode optical fiber is proposed and demonstrated. An optical pump wave is used to stimulate narrowband, resonant guided acoustic modes, which introduce phase modulation to a co-propagating optical probe wave. The phase modulation is converted to an intensity signal at the output of a Sagnac interferometer loop. The intensity waveform is detected, amplified and driven back to modulate the optical pump. Oscillations are achieved at a frequency of 319 MHz, which matches the resonance of the acoustic mode that provides the largest phase modulation of the probe wave. Oscillations at the frequencies of competing acoustic modes are suppressed by at least 40 dB. The linewidth of the acoustic resonance is sufficiently narrow to provide oscillations at a single longitudinal mode of the hybrid cavity. Competing longitudinal modes are suppressed by at least 38 dB as well. Unlike other opto-electronic oscillators, no radio-frequency filtering is required within the hybrid cavity. The frequency of oscillations is entirely determined by the fiber opto-mechanics.