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Mode conversion coefficients in optical fibers
Applied Optics
|February 16, 2010
Summary
A new method experimentally determines mode conversion coefficients in multimode fibers by analyzing far-field output. Mode coupling in liquid-core fibers increases significantly under pressure, with glass-core fibers showing much higher values.
Area of Science:
- Optics and Photonics
- Materials Science
Background:
- Multimode fibers are crucial for optical communication and sensing.
- Understanding mode conversion is essential for predicting signal behavior and loss.
- Existing methods for measuring mode conversion can be complex.
Purpose of the Study:
- To develop a simple experimental method for determining mode conversion coefficients in multimode fibers.
- To quantify the normalized mode coupling coefficient in liquid-core and glass-core fibers.
- To investigate the effect of transverse pressure on mode coupling in liquid-core fibers.
Main Methods:
- The method involves observing the far-field output of a collimated input beam.
- The angle of incidence of the input beam is systematically varied.
- Mode coupling coefficients are calculated based on far-field patterns.
Main Results:
- A normalized mode coupling coefficient (D) of 3 x 10^-6 rad^2 m^-1 was measured in liquid-core fibers.
- Applying transverse pressure increased the mode coupling coefficient in liquid-core fibers by up to a factor of 10.
- Glass-core fibers exhibited mode coupling coefficients approximately two orders of magnitude larger than liquid-core fibers.
Conclusions:
- The devised method provides a straightforward approach for experimental determination of mode conversion coefficients.
- Transverse pressure significantly influences mode coupling in liquid-core fibers.
- Glass-core fibers demonstrate inherently higher mode coupling compared to liquid-core fibers, suggesting different loss mechanisms or structural properties.
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