为了探索飞行时间技术在中短距离长度测量方面的应用，提出一种测量光纤折射率和长度的方案。基于飞行时间技术原理的 TDC7201芯片，配合微控制器、激光发射机和激光接收机等器件和模块，构成一套测 量系统，理论上可对长度范因为 2 cm～100 km的光纤进行测量。以该方案搭建了一个实验平台，对约 1 cm、2 cm、3 cm、以及 1.5 m、5.1 m、20 km、 70 km和 90 km等多种长度的光纤进行了折射率或长度测量。 结果表明：该方案最短测量距离为 1 cm，最长测量距离起过 90 km，在测量长度约 5.1 m的光纤时，系统的标准差可达 0.9 mm。

A high power and good beam quality InGaAs/GaAs quantum well semiconductor disk laser at 1 015 nm wavelength is reported. The semiconductor wafer is grown in reverse order: substrate is on the window side and the distributed Bragg reflector is the last grown epilayer. Then the wafer is up-side-down and capillary bonded to a SiC heatsink, and the substrate is chemically etched. Because the total thickness of the substrate-removed structure is less than 10 μm, the thermal management of the laser is significantly improved, and the maximum output power over 0.6 W is obtained using a 3% output coupler and 3.2 W incident pump power. The M2 factors of 1.02 and 1.01 indicate a near-diffraction-limited beam quality. To further reveal the characteristics of this substrate-etched structure on the thermal management, the heat flux and the temperature distribution of the gain wafer are numerically analyzed, and the corresponding results are discussed.