A fiber Bragg grating (FBG) sensor system using a fiber ring laser with a hybrid amplifier is proposed and demonstrated. The hybrid amplifier comprises an erbium doped waveguide amplifier and a semiconductor optical amplifier. The experiment shows that such the hybrid amplifier has a high amplifier spontaneous emission power and gain spectrum. Moreover, this fiber ring laser can provide a stable multiwavelength output with an optical signal-to-noise ratio over 50 dB even if the FBGs are located at a 25 km remote sensing position.
Three new design waveguides for adiabatic directional full couplers are studied. We theoretically and numerically show that the performance of new full couplers is improved. Whe the length of the coupler is 4mm (the minimum local beat length is 2mm) at 1.57μm wavelength, the crosstalk is smaller than -35dB. For the length of the coupler is 4mm, the crosstalk is smaller than -20dB in the 1.5μm ~ 1.7μm range. For the length of the couplers is 7mm, we find that the crosstalk is smaller than -35dB in the 1.5μm ~ 1.7μm range. The same as the requirement of the maximum crosstalk, the corresponding wavelength is between 1.42μm to 1.7μm when the lenght of the couplers is 12mm.