C- and L-band tunable fiber ring laser using a two-taper Mach-Zehnder interferometer filter

A stable C- and L-band tunable fiber ring laser, using a two-taper Mach-Zehnder interferometer (MZI) as a filter, is proposed and demonstrated experimentally. One of the two taper waists is mechanically bent to tune the laser wavelength. Being amplified by an L-band erbium-doped fiber amplifier and an erbium-doped fiber, respectively, the fiber ring laser has a full L-band (1564-1605 nm) and C- band (1550-1565 nm) tuning range with a side-mode suppression ratio as high as 50 dB. The laser linewidth and the minimum tuning step are related to the MZI's cavity length. It was also found that thermal annealing relieved the internal stresses of the tapers and greatly improved the laser performance. (C) 2010 Optical Society of America