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Polarization mode dispersion in single-mode fibers
Imperfections in optical fibers cause birefringence, leading to mode dispersion. This dispersion was measured and found to be 30 psec/km, but can be compensated with a double twist.
Area of Science:
- Optics
- Materials Science
- Telecommunications
Background:
- Real single-mode optical fibers exhibit imperfections.
- These imperfections lead to polarization-dependent phase and group velocities, a phenomenon known as birefringence.
Purpose of the Study:
- To measure the mode dispersion caused by birefringence in short optical fiber lengths.
- To investigate methods for compensating mode dispersion.
Main Methods:
- Measured mode dispersion by analyzing the depolarization of broad-bandwidth light in fiber lengths of 0.5-2.5 meters.
- Investigated compensation using a +/-68 degrees double twist.
Main Results:
- A typical fiber exhibited a mode dispersion of 30 psec/km at a 0.69-microm wavelength.
- Observed results were in good agreement with the measured birefringence.
Conclusions:
- Mode dispersion is a significant effect in real optical fibers.
- A double twist midway along the fiber can effectively compensate for mode dispersion by interchanging fast and slow modes.
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