A Novel Mach-Zehnder Interferometer Using Eccentric-Core Fiber Design for Optical Coherence Tomography

Area of Science:

• Optics and Photonics
• Fiber Optics
• Interferometry

Background:

• Optical Coherence Tomography (OCT) traditionally uses single-mode fiber (SMF).
• Achieving precise optical path difference (OPD) control in fiber-based interferometers is crucial.
• Reference delay lines can add complexity and bulk to OCT systems.

Purpose of the Study:

• To propose and demonstrate a novel Mach-Zehnder interferometer design for OCT.
• To utilize eccentric-core fiber (ECF) as a key component for enhanced control.
• To replace the conventional reference optical delay line with an all-fiber passive device.

Main Methods:

• An eccentric-core fiber (ECF) was integrated into one arm of a Mach-Zehnder interferometer.
• The sensitivity of the ECF to directional bending was exploited for OPD adjustment.
• Birefringence of the ECF was theoretically calculated and experimentally verified.
• System performance was analyzed using a mirror and overlapping glass slides as samples.

Main Results:

• The ECF-based interferometer demonstrated precise OPD adjustment via directional bending.
• The polarization sensitivity of the ECF was found to be comparable to SMF.
• The proposed structure successfully functioned as an all-fiber passive device, replacing a delay line.
• Experimental measurements confirmed the system's response to sample variations.

Conclusions:

• The novel ECF-based Mach-Zehnder interferometer is a viable and precise alternative for OCT.
• ECF's directional bending sensitivity offers a unique method for OPD control in all-fiber systems.
• This design simplifies OCT systems by eliminating the need for a separate reference delay line.