Erbium-doped fiber ring laser with wavelength selective filter based on non-linear photonic crystal fiber Mach-Zehnder interferometer

A high output power, stable wavelength spacing and switchable multi-wavelength erbiumdoped fiber laser has been demonstrated experimentally using a combination of non-linear photonic crystal fiber Mach-Zehnder (MZI) interferometer with polarization dependent loss effect. This MZI functions together with a polarization controller (PC) as a wave selecting filter (WSF). Adjusting the PC within the WSF part gives rise to three emissions as single, dual and triple wavelengths. Multi-wavelength laser with maximum spacing of 1.6 nm was achieved by controlling the polarization state in a ring cavity. Such stable wavelength spacing aroused interest in wavelength-division-multiplexer systems. Output power around -3 dB at 1550 nm wavelength, with small power fluctuation for each line, was recorded at room temperature. The measured 3-dB laser line-width was 0.03 nm, with a high side-mode suppression ratio of 48 dB.