Single-element balanced detector giving 65 dB CMRR at 30 MHz

Area of Science:

• Photonics
• Optical Sensing
• Interferometry

Background:

• Balanced detectors (BDs) are crucial for noise reduction in optical measurements.
• Traditional BDs often require complex designs and careful component matching.
• Achieving high common-mode rejection ratio (CMRR) is essential for sensitive detection.

Purpose of the Study:

• To present a simplified single-element balanced detector (BD) design.
• To demonstrate high common-mode rejection ratio (CMRR) using optical fibers.
• To improve stability and reduce complexity in balanced detection systems.

Main Methods:

• Utilized optical fibers in sensing and reference channels with controlled path length differences.
• Designed a single-element detector to capture the differential signal at a target frequency.
• Employed the optical Kerr effect with a 30 MHz pulsed laser for demonstration.

Main Results:

• Achieved a common-mode rejection ratio (CMRR) of 65 dB, near the shot-noise limit.
• Demonstrated stable CMRR performance over extended periods.
• Showcased superior performance compared to a commercial balanced detector in optical Kerr effect measurements.

Conclusions:

• The proposed single-element fiber optic balanced detector offers a simple and effective solution for noise suppression.
• This design eliminates the need for precise detector and amplifier matching, enhancing stability.
• The demonstrated high CMRR in the MHz range is scalable to other frequencies (kHz-GHz).