  We present a comprehensive theoretical and experimental investigation of a
dual-wavelength, bismuth-doped fiber (BDF) laser operating near 1700 nm based
on cascaded cavities. The BDF provides optical gain from 1650 nm to 1800 nm
when pumped at 1550 nm; the laser cavity is defined by a 90% mirror on one end
and two fiber Bragg gratings (FBGs) separated by a length of BDF on the other.
The laser can operate at either wavelength alone or both wavelengths
simultaneously by simple adjustment of the pump power. Experimental results
correlate well simulations based on a theoretical model of the laser.
