An ultra-long-distance Fiber Bragg Grating (FBG) sensor system using a high-speed swept-wavelength light source
(HSLS) is proposed and demonstrated. The light output of the HSLS is amplified and turned on and off, and its timing is
synchronized to the sweep signal of the HSLS to reduce optical noise caused by Rayleigh scattering from the
transmission fiber. This system can detect changes in FBG reflection wavelengths even when the FBGs are located at a
distance of 230 km.
A high-speed MEMS swept-wavelength light source (SLS) for an FBG sensor system is proposed and demonstrated. It is basically a multi-mode external-cavity laser diode (LD), and consists mainly of an LD head, diffraction grating, and electromagnetically actuated MEMS scanning mirror. It has a linewidth of 0.03 nm, scan range from 1508 to 1582 nm, scan rate of 0.57 ms and output power of 10 mW. The heart of the MEMS SLS is the MEMS scanning mirror (8 x 6 mm) that changes the oscillation wavelength continuously and rapidly. The scanning mirror is actuated by electromagnetic force derived from a permalloy piece glued on the back of the mirror and a C-shape electromagnet. The MEMS SLS allows construction of a low-cost, simple and high-speed FBG interrogator system.