Multiwavelength fiber laser based on enhanced bidirectional SOA utilizing Lyot filter

Abstract

We demonstrated a multiwavelength fiber laser (MWFL) based on two bidirectional semiconductor optical amplifiers (SOAs) and a Lyot filter. The structure is enhanced by placing two -SOAs in a bidirectional region to improve the lasing performance. This resulted in a higher extinction ratio (ER) of 36.05 dB, as earlier work only achieved a maximum extinction ratio (ER) of 17 dB utilizing an SOA based on bidirectional configuration. The performance of the MWFL in unidirectional and bidirectional configurations, as well as different parameter settings of SOA current and polarization controller (PC) angle is examined. Using a unidirectional configuration decreases the amplification on one side of the SOA, hence reducing the wavelength bandwidth by 2 nm, which is equivalent to six lasing lines. According to the wavelength bandwidth of 13 nm and channel spacing of 0.22 nm, the optimal performance of MWFL employing bidirectional configuration is 56 lasing lines within 3 dB bandwidth. Consequently, we decreased each SOA's operating current, resulting in lower lasing lines. Changing the PC angle modifies the polarization degree and state, hence impacting multiwavelength flatness and wavelength bandwidth performance. When the polarizer is removed, the ER and lasing lines are decreased to 42 dB and 9 nm, respectively. The MWFL has high stability with a peak power fluctuation of 0.25 dB in 120 min.