Four-port fiber frequency shifter with a null taper coupler.
A prototype of a new design of fiber frequency shifter, based on a special four-port fused taper coupler with a null maximum coupling ratio, is reported. In this coupler the constituent fibers are so dissimilar that the maximum coupling is (ideally) zero. In the presence of a flexural acoustic wave, light is coupled between the fibers, acquiring a frequency shift in the process. Near 100% conversion with 30-dB sideband and carrier suppression is achieved, in an unoptimized device, for just 1 mW of electrical drive power.
T A
TA
Birks
S G
SG
Farwell
P S
PS
Russell
C N
CN
Pannell