We propose and fabricate a linear frequency-swept DFB laser array based on the reconstructed-equivalent-chirp (REC) technique used in sensing system. During the fabrication process of the laser arrays, the reconstructed-equivalent-chirp technique is utilized to simplify the fabrication of the grating and precisely control the grating phase. A semiconductor optical amplifier (SOA) is monolithically integrated to enhance and balance the output optical power. The module achieves a wavelength range of more than 3 nm by covering 4 channels with an interval of 0.8 nm. The side mode suppression ratios (SMSRs) of all channels are above 50 dB and the output power are guaranteed above 10 dBm with the SOA providing 14 dBm saturation output power. To tune the wavelength on the microsecond scale, we adopt a combination of a MCU and a FPGA as the controlling core to turn on and off the driving current of all the 4 lasers on the DFB laser array, and the switching time between 2 channels is well controlled within 50 ns. At the same time, the module makes the wavelength output linearly with the current through the filter circuit, and achieves the sweep speed of 100 nm/s. This sweep speed, sweep range, output power, and good single-model performance meet the needs of sensing system for light sources.
A weak double-peak fiber Bragg grating (FBG) temperature sensor is proposed and demonstrated. Wavelength-swept tunable laser is regarded as one of the most popular demodulation methods for fiber Bragg grating (FBG) sensors. However, due to the limitations of the existing tunable laser technologies, a fast, compact, stable and low-cost tunable laser for FBG sensors is still unavailable, which will become one of the major barriers for more widespread applications of FBG sensors. To further improve the efficiency and accuracy of the FBG interrogation system, a FBG temperature sensor is proposed and demonstrated by using tunable laser and a weak double-peak FBG. Since the reflection of the weak double-peak FBG has two main reflection peaks and relatively wide bandwidth, it is convenient to track the two characteristic peaks to accurately obtain the wavelength shift during the alteration of ambience temperature. A proof-ofconcept experiment is also conducted to verify the theory. By demodulating a weak double-peak FBG in the temperature experiment, a sensor sensitivity of 10.17 pm/ °C is measured for the proposed interrogation system.
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