Optical Fiber Filters Linewidth Enhancement Based on Erbium-doped Photonic Crystal Fiber Cavities

Optical fibers have recently become an essential part of any communication system. Erbium-doped photonic crystal fibers (EDPCF) have special optical properties that can be used in interesting applications like interferometric sensors and supercontinuum sources. In this work, we report active optical fiber cavities that enhance the linewidth of passive fiber filters. In the proposed configuration, an Erbium-doped photonic crystal fiber (EDPCF) is used as a gain medium with a passive fiber filter. The EDPCF gain reaches 30 dB around the center wavelength of 1560 nm. The 3-dB linewidth of the filter is originally 7.7 nm and reaches 4.2 nm after enhancement. This configuration is compared with another one where the gain medium is a semiconductor optical amplifier (SOA). The 3-dB linewidth enhancement is 1.83× in the case of EDPCF, while it is 2× in the case of SOA.