Nanosecond thermal fiber switch using a Sagnac interferometer

We demonstrate a new, fast, and stable all-optical fiber switch based on the TOAD principle. It utilizes a transient thermal phase shift induced by a short pump pulse to cause switching in a cobalt (Co)-doped fiber placed in a Sagnac fiber loop. Switched pulses as short as 7-ns were observed in a 2-m loop containing a 2.55-cm length of Co-doped fiber pumped with 12-ns pulses. Compared to other all-optical switches using doped fibers, this switch offers a dramatic increase in speed and stability, and a sizable reduction in fiber length requirement.