By employing a simple model of describing three-level lasers, we have theoretically investigated the effect of photon lifetime on the output dynamics of Er-doped distributed feedback fibre lasers. And based on the theoretical analysis we have proposed a promising method to suppress self-pulsing behaviour in the fibre lasers.

The technique of Brillouin scattering distributed optical fiber sensing has been presented. Optical heterodyne detection was used to detect the weak Brillouin back scattering signal based on single longitudinal mode distributed feedback (DFB) laser and electric optical modulation technique. The scattering signal was amplified effectively by improving the filter and erbium doped fiber amplifier (EDFA). The 11 GHz radio-frequency (RF) signal of Brillouin back scattering is gathered and averaged. The experimental procedures and results are presented. The results show that the peak power of Brillouin back scattering at 11 GHz can reach 50 mV, and the intensity noise of light source induced the system's signal to noise ratio (SNR) decreased greatly, which reduced the difficulty of signal process in demodulation system. The experimental results confirm that the configuration is feasible.

A diode-pumped Yb-doped double-clad fiber amplifier (YDDCFA) with the narrow bandwidth continuous wave (CW) and pulse input signal is investigated. The input single-mode (SM) signal bandwidth is 10^(-4) nm from a distributed feedback (DFB) fiber laser. The saturated gain of the CW amplification is 11 dB at the forward pump. And besides CW signals, we also amplify pulses with duration of 150 ns and the 1-Hz repetition. The pulse is amplified to 2 W of peak power, 0.31 microjoule of energy, 23 dB of gain and less than 6% of stability at the forward pump power of 1.4 W. For higher power, reflections and backscattering can generate the self pulsation in the amplifier. The results are important for the development of the narrow-band double-clad fiber amplifier.

Yb-doped phase-shifted fiber Bragg grating (PS-FBG) has been fabricated with phase shift introduced by shielded method. In the fabrication process, the PS-FBG is used as the laser cavity. Whether the introduced phase-shift is π/2 or not is determined by the laser output power. As long as the output power of the laser begins to drop down, the exposure is stopped, and the phase shift is π/2 then. It is necessary to anneal the PS-FBG to stabilize its characteristics, which will reduce the introduced phase-shift. The second exposure of the PS-FBG is needed to restore the π/2 phase shift. A fiber grating laser has been made with the method. When the pump power is 100 mW, the laser output is 25 mW with signal-noise-ratio (SNR) of 60 dB. Within 1 h the output fluctuation of the laser is less than 1%. The laser is always under single-mode operation when the temperature of the fiber grating is tuned between 25 ℃ and 30 ℃.

采用遮挡法引入相移制作了掺Yb相移光纤光栅(PS-FBG)。在制作光栅的过程中,将其作为激光器的谐振腔,通过监测激光器的输出功率来确定相移大小。当激光器的输出功率开始下降时,停止曝光,此时引入的相移为π/2。为了使光栅的特性尽快稳定下来需要对光栅进行退火,这将导致引入的相移小于π/2。为了弥补退火过程中引起的相移降低,需要对退火后的光栅进行二次曝光,以使光栅的相移恢复π/2。利用该方法制作了一只光纤光栅激光器。当抽运功率为100 mW时,获得了25 mW的输出功率,信噪比(SNR)为60 dB。在1 h内,输出功率波动小于1%。当光栅的温度在25～30 ℃之间变化时,激光器单纵模运转。

A diode-pumped Yb-doped double-clad fiber amplifier (YDDCFA) with the narrow bandwidth continuous wave (CW) and pulse input signal is investigated. The input single-mode (SM) signal bandwidth is 10^(-4) nm from a distributed feedback (DFB) fiber laser. The saturated gain of the CW amplification is 11 dB at the forward pump. And besides CW signals, we also amplify pulses with duration of 150 ns and the 1-Hz repetition. The pulse is amplified to 2 W of peak power, 0.31 microjoule of energy, 23 dB of gain and less than 6% of stability at the forward pump power of 1.4 W. For higher power, reflections and backscattering can generate the self pulsation in the amplifier. The results are important for the development of the narrow-band double-clad fiber amplifier.

We have successfully demonstrated a single-frequency distributed-feedback Yb-doped silica fiber laser. The laser cavity is 10 cm long and is formed by a simple method called the shielded method. The phase shift in the fiber Bragg grating is introduced by shielding a small region of the fiber during fabrication by ultraviolet (UV) light from a 193-nm excimer. Without complex pump configuration, the fiber laser gives a maximum output of more than 20 mW when pumped by laser diode at 978 nm with 100 mW. The laser shows a single frequency and single polarization operation.

分析了布里渊分布式光纤传感技术原理,采用自行研制的光纤单纵模分布反馈(DFB)激光器结合电光调制技术,利用相干检测技术,对布里渊微弱后向散射信号进行检测。通过改进滤波放大技术,对微弱后向散射光信号进行有效放大,再用扰偏技术及信号采样平均处理,实现对光纤传感器后向布里渊散射信号在11 GHz高频段直接采集显示。结果表明,探测所得布里渊散射信号峰值功率可达50 mV,能有效降低解调系统信号检测难度,改善了系统信噪比(SNR)。初步实验结果证明了该方案的可行性。

分析了光纤Bragg光栅的传感原理，将光纤光栅置于细钢管通过一种耐高温胶粘结细钢管两端使光纤光栅在高温下不脱落，并通过细钢管上的中间螺纹给光纤光栅施加预应力，使光纤光栅在温度变化过程中一直保持张紧状态，保证传感器有很好的重复性和良好的线性．实验结果表明：该FBG光纤光栅温度传感器灵敏度为0．0252nm／℃，有良好的重复性和线性，温度测量范围达200℃以上，可应用在高温环境测量温度的变化．

报道了一种检测光纤光栅传感器波长的新方案.实验系统采用新型的级联结构对电热调谐的光纤光栅滤波器进行复用,扫描分析传感信号光的峰值波长,同时用参考波长校准方法消除了电热调谐中的蠕动误差.结果表明,系统的检测范围可达23nm,波长分辨率为3.1pm,应变测量分辨率为2.56με.