Abstract: A polarized fiber laser source includes a fiber laser 10 comprising a pair of Bragg gratings 14,16 at opposite ends of a fiber laser cavity 18 which is doped with a rare-earth dopant so as to allow lasing to occur at a lasing wavelength .lambda..sub.L. A grating tap 26 is provided along a portion of the laser cavity 18 to couple-out a predetermined amount of light along one polarization, e.g., the "s" polarization", at the lasing wavelength .lambda..sub.L. This causes one polarization mode to experience more loss than the other, thereby allowing the fiber laser to lase only on the less lossy polarization mode and causing the laser output light 40 to be polarized only along such polarization.

Abstract: An optical transmitter includes at least one single-mode type laser diode for producing laser emission, and an external cavity with a partial reflector for reflecting a portion of the emission back into the laser. A DC current operates the laser in a first mode with a first frequency of emission. The laser is pulsed with a predetermined sequence of signal pulses each shifting the laser to a second mode with a second frequency different than the first frequency. The frequency shifting thereby constitutes information in a laser beam corresponding to the sequence of signal pulses. The laser system may be formed of a plurality of laser diodes in an array, so that the reflector reflects emission back into the diodes to lock them in the alternate modes of operation.