Bandwidth-tunable narrowband rectangular optical filter based on stimulated Brillouin scattering in optical fiber

Area of Science:

• Photonics and Optical Engineering
• Fiber Optic Communications
• Nonlinear Optics

Background:

• Stimulated Brillouin scattering (SBS) offers a versatile platform for optical filtering and amplification.
• Achieving precise spectral shaping and low ripple in SBS-based filters remains a challenge.
• Nonlinearity and multi-peak Brillouin responses can degrade filter performance.

Purpose of the Study:

• To propose and demonstrate a novel rectangular optical filter with tunable bandwidth.
• To suppress passband ripple and out-of-band gain for improved signal fidelity.
• To analyze the noise performance and system applicability of the proposed filter.

Main Methods:

• Utilizing stimulated Brillouin scattering (SBS) in optical fiber for filter operation.
• Employing digital feedback control for precise shaping of comb-like pump spectral lines.
• Mitigating nonlinear effects and using a single Brillouin peak fiber to reduce ripple.
• Analyzing noise performance across various bandwidths.

Main Results:

• Achieved a tunable bandwidth from 50 MHz to 4 GHz with <15-MHz resolution.
• Suppressed passband ripple to approximately 1 dB.
• Demonstrated a 2.1-GHz bandwidth filter with 19-dB gain amplifying OFDM signals (QPSK and 16-QAM).

Conclusions:

• The proposed SBS-based rectangular optical filter offers precise spectral control and low ripple.
• The filter demonstrates effective amplification of complex modulated signals for subscriber systems.
• This technology holds promise for advanced optical communication networks.