Self-tuning optical waveguide filter

摘要

A self-tuning optical waveguide filter (20) for attenuating a lower power light signal at lambda 1 more than a higher power signal at lambda 2 comprises a length of single core (27) waveguide (11) and a light injector (12) for applying lambda 1, lambda 2 into the waveguide in two propagating modes subject to mode beating. The mode beating produces high intensity regions of lambda 1 physically displaced from high intensity regions of lambda 2. A portion (15) of the waveguide (11) is doped with a saturable absorber for disproportionately attenuating wavelengths at lower power levels. Advantageously the waveguide is a single-core fiber having its central core doped with rare-earth saturable absorber. In a preferred embodiment, the fiber is dimensioned to propagate lambda 1, lambda 2 in the LPO1, and LPO2 modes, and the saturable absorber is Erbium. <IMAGE> <IMAGE>