A distributed feedback fibre laser is realized with a phase-shifted fibre Bragg grating. Dual-mode operation is obtained by means of linear birefringence for heterodyne generation of optical microwave signal. The two modes, operating in the same cavity produce a beat signal with exceptionally low-phase noise. The linewidth of the resulting microwave signal obtained is less than 1 kHz.
- optical phase locked loop
- phase-shifteed grating