Measurement of optical fiber parameters and thermal core diffusion characteristics by digital image processing

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Accurate measurement of optical fiber parameters like numerical aperture (NA) and mode field diameter (MFD) is crucial for telecommunications and sensing.
• Existing methods for NA and MFD measurement can be expensive and complex, limiting accessibility in laboratory settings.

Purpose of the Study:

• To develop and validate a cost-effective, accessible method for simultaneously measuring the NA and MFD of single-mode optical fibers.
• To assess the utility of this method in monitoring process-induced changes, such as core diffusion, in ultra-high NA fibers.

Main Methods:

• Digital image processing of the light output pattern from optical fibers projected onto a screen.
• Utilizing smartphone cameras and simple optomechanical components for data acquisition.
• Measuring changes in NA and MFD during controlled heat deposition from a CO2 laser source on an ultra-high NA fiber.

Main Results:

• The developed method successfully performed simultaneous measurements of NA and MFD on commercial single-mode fibers.
• The technique effectively monitored the adiabaticity of core diffusion in an ultra-high NA fiber by observing the constancy of the NA * MFD product.
• Demonstrated a strong correlation between the NA * MFD product and the adiabatic nature of the process.

Conclusions:

• The proposed digital image processing technique offers a cheap and easily implementable alternative for measuring key optical fiber parameters.
• This method is suitable for laboratory use and for monitoring dynamic processes affecting fiber properties, such as laser-induced core diffusion.
• The ability to monitor adiabaticity via the NA * MFD product enhances the diagnostic capabilities for fiber fabrication and modification processes.