Fiber Bragg Grating or FBG sensors are gaining more and more interest in structural health monitoring of composite materials. Often, the weakest point in such a system is the ingress point of the fiber sensing chain into the composite material. For this reason we have developed a strongly miniaturized FBG interrogator unit with wireless power and data transmission, which can be incorporated in the composite structure. The interrogator is based on an arrayed waveguide grating (AWG) filter fabricated in a SOI technology, which is tailored in such a way to give large cross-talk between neighboring channels. The AWG signals are read by a linear 128 pixel InGaAs array flip-chipped on top of the Photonic Circuit (PIC). The spectrometer unit is completed with a ROIC mounted on the same substrate. The SLED and remaining electronics are integrated on a small and thin substrate and surrounded by the wireless antenna. The interrogator has an overall dimension of 100 mm diameter by max 7 mm height. The power dissipation of the electronics unit is limited to 1.5 W. The unit is capable of measuring strain values as low as 5 micro-strain.
Monolithic Semiconductor Ring Lasers (SRLs) are promising devices for all-optical memory and all-optical switching
applications, as they can operate in a directional bistable regime where only one directional mode (clockwise or anti-clockwise)
is active at one time. The unidirectional bistable regime can be naturally associated to a binary logic, and the
SRL represents an elementary digital memory cell that can be written all-optically, realising the function of an all-optical
flip-flop. In fact, the direction of operation can be switched by injecting an external optical signal pulse into the SRL
through one of the 4 input/output ports.
Directional switching of the SRL-based all-optical flip-flop has been demonstrated by injecting optical pulses with 5 ps
duration into one of the four input/output ports. The required switching energy is around 100 fJ, and the swiching time is
between 100 and 200 ps. The same function has been demonstrated by injecting 400 ps pulses as optical trigger.