膜的

Documents against payment: 20% T/T deposit , 80%againtst the copy of BL payment After shipment.

付款条件：电汇，20%首期付款，卖方收到汇款开始生产，80%见物运提单复印或扫描文件付款。

In the end, the photoelectric preamplifier's output Signal Noise Ratio and the laser frequency stability are tested.

最后，对光电前放输出信噪比和稳频精度进行了测试。