Birefringence in elliptically clad borosilicate single-mode fibers

Area of Science:

• Materials Science
• Optical Engineering
• Solid State Physics

Background:

• Birefringence in optical fibers can impact signal transmission.
• Understanding stress-induced birefringence is crucial for fiber optic applications.
• Borosilicate fibers are widely used in telecommunications.

Purpose of the Study:

• To investigate the origin of stress-induced strain birefringence in borosilicate elliptically clad fibers.
• To determine the factors influencing the magnitude of this birefringence.
• To assess the permanence of the observed strain birefringence.

Main Methods:

• Experimental analysis of borosilicate elliptically clad fibers.
• Thermal cycling to test annealing effects.
• Varying cladding ellipticity and material compositions.

Main Results:

• Strain birefringence originates from the expansion coefficient mismatch between the cladding and outer jacket.
• The birefringence is non-annealable, even after repeated thermal cycling.
• Birefringence increases linearly with cladding ellipticity and expansion coefficient mismatch for a fixed dopant concentration.

Conclusions:

• The expansion coefficient mismatch is the primary cause of permanent strain birefringence in these fibers.
• Cladding ellipticity is a key design parameter influencing birefringence.
• Strategies to mitigate birefringence must account for material properties and fiber geometry.