A stable multiwavelength erbium-doped fiber laser (EDFL) based on random distributed feedback (RDFB) is presented. The random EDFL consists of a half-opened linear cavity in which a mirror forms one end, while the other end is connected to RDFB of a 25-km-long single mode fiber. In the laser cavity, the instability caused by the RDFB and cascaded stimulated Brillouin scattering is successfully mitigated by four wave mixing effect in a 2-kmlong highly nonlinear fiber. Experimental results indicate the generation of 24 stable laser lines at the pump power of 350 mW. The recorded peak power fluctuation for the laser is less than 0.7 dB in a 60-min duration, illustrating the stability of the multiwavelength random fiber laser.
We investigate an influence of intensity to the flatness of multiwavelength fiber laser based on a mechanism of intensity dependent transmission. This mechanism is induced by nonlinear polarization rotation from a semiconductor optical amplifier and its combination with polarization devices. Due to the mechanism, a flatter multiwavelength spectrum can be achieved by reducing the bias current. The use of lower throughput port of an optical coupler can also increase the flatness of the multiwavelength spectrum. The flat multiwavelength spectrum has 153 lines within 3 dB bandwidth at current setting of 125 mA. This multiwavelength laser is stable within 60 min at power fluctuation of less than 0.2 dB.
We investigate the performance of multiwavelength spectrum based on an advanced mechanism of a bidirectional Lyot filter. The generation and the variation of the multiwavelength spectrum are due to the effect of intensity dependent loss, which is induced from a semiconductor optical amplifier and its combination with a polarizer. By using the bidirectional configuration, a flat spectrum of 96 number of lines within 5 dB bandwidth is generated at current setting of 350 mA. The extinction ratio of the multiwavelength spectrum is high at 15 dB even though the line spacing is 0.1 nm. Multiwavelength flatness is better using the bidirectional Lyot filter configuration due to the effect of double interference. Additionally, different intensity and polarization angle are also found to be influencing the multiwavelength spectrum.
A multi-wavelength fiber laser which is based on a Lyot filter is experimentally demonstrated. A combination of four-wave mixing in a highly nonlinear fiber and Lyot filter mechanism in the laser cavity is able to generate multi-wavelength with relatively high extinction ratio (ER). At the input current of 100mA, six laser lines with ER more than 5 dB are successfully generated. The wavelength spacing for the multi-wavelength is 0.15nm, corresponding to the characteristics of the Lyot filter used.
Keyword:Four-wave mixing Lyot filter Multi-wavelength fiber laser
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