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Polarization-insensitive nonlinear optical loop mirror demultiplexer with twisted fiber
Y Liang1, J W Lou, J K Andersen
1Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109-2122, USA.
Optics Letters
|December 13, 2007
Summary
We reduced polarization sensitivity in nonlinear optical loop mirrors (NOLMs) using twisted fiber. This fiber twisting significantly improves NOLM performance by minimizing polarization-dependent losses.
Area of Science:
- Nonlinear optics
- Optical fiber technology
Background:
- Polarization sensitivity in nonlinear optical loop mirrors (NOLMs) can degrade device performance.
- Minimizing polarization sensitivity is crucial for stable and reliable operation of NOLMs.
Purpose of the Study:
- To experimentally reduce the polarization sensitivity of a nonlinear optical loop mirror (NOLM).
- To investigate the effect of twisted fiber on NOLM polarization sensitivity.
Main Methods:
- Utilized 550 m of twisted dispersion-shifted fiber with a twist rate of 8 turns/m.
- Induce circular birefringence in the fiber to equalize polarization-dependent nonlinear phase shifts.
- Experimentally measured polarization sensitivity with varying twist rates.
Main Results:
- Reduced polarization sensitivity from 5 dB to 0.5 dB using twisted fiber.
- Observed a monotonic decrease in sensitivity with increasing twist rate, with >4 turns/m needed for circular polarization emulation.
- Achieved 23% nonlinear transmission at 4 pJ/pulse switching energy with 8 turns/m twisted fiber.
Conclusions:
- Fiber twisting effectively reduces NOLM polarization sensitivity.
- Remaining sensitivity is attributed to energy transfer between orthogonal signal pulse modes.
- Optimized fiber twist rates are essential for high-performance NOLMs.
