  We report an in-line polarization-dependent all-optical fiber modulator based
on a stereo graphene-microfiber structure (GMF) by utilizing the lab-on-rod
technique. Owing to the unique spring-like geometry, an ultra-long GMF
interaction length can be achieved, and an ultra-high modulation depth (MD) of
~7.5 dB and a high modulation efficiency (ME) of ~0.2 dB/mW were demonstrated
for one polarization state. The MD and ME are more than one order larger than
those of other graphene-waveguide hybrid all-optical modulators. By further
optimizing the transferring and cleaning process, the modulator can quickly
switch between transparent and opaque states for both the two polarization
states with a maximized MD of tens of decibels. This modulator is compatible
with current fiber-optic communication systems and may be applied in the near
future to meet the impending need for ultrafast optical signal processing.

Optics