Wide bandwidth flat gain Raman amplifier by using polarization-independent interferometric filter

Area of Science:

• Photonics and Optical Engineering
• Fiber Optic Communications

Background:

• Raman gain flattening is essential for broadband optical amplifiers.
• Polarization-dependent loss can degrade amplifier performance.

Purpose of the Study:

• To propose and demonstrate a polarization-independent filter for flattening Raman gain.
• To investigate the effectiveness of high birefringence fiber sections in a fiber loop mirror.

Main Methods:

• A polarization-independent filter was constructed using a fiber loop mirror with high birefringence (Hi-Bi) fiber sections and a polarization controller.
• Raman gain profiles were measured using a single pump wavelength (1455 nm) with varying numbers and lengths of Hi-Bi fiber sections.

Main Results:

• A flattened Raman gain within +/-0.5 dB over a 43 nm bandwidth at 1555 nm was achieved using a 5 cm Hi-Bi fiber section.
• Using two Hi-Bi fiber sections (5 cm and 8.5 cm) further flattened the gain over a 38 nm bandwidth with reduced gain suppression.

Conclusions:

• The proposed fiber loop mirror filter effectively flattens Raman gain in a polarization-independent manner.
• The configuration offers a viable solution for improving the performance of broadband optical amplifiers.