Abstract
The frequency references in the band of optical communication receive great attentions as Dense Wavelength Division Multiplexing (DWDM) is widely adopted in recent years. Most research is focused in 1550 nm region because of lowest loss in fiber and only a few researches which are studied in shorter wavelength like 1530 nm. In this thesis, our lab plan to build up an accurate laser system which is stabilized on molecular transition, and use the fiber comb system to get the absolute frequency of molecular transition. By this technique, the frequency standard in 1530 nm region can be built up and become a reference frequency for measuring other molecular transition. The main point of this study is to find the capability of detecting the saturation dip of acetylene molecule in 1530 nm with multi-pass cell, and then try to stabilize the laser frequency in order to measure its absolute frequency in 1530 nm region. In this study, the laser source is a commercial External Cavity Diode Laser which is amplified by Erbium- Doped Fiber Amplifier. In order to detect the saturation dip, two laser beams with opposite propagating directions pass through a multi-pass cell (White cell) filled up with the low pressure acetylene molecule, and the effective optical path in cell is 4 meter. The Lamb dip of 12C2H2 can be observed successfully, and the linewidth of dip is closed to 3 MHz, and SNR is 200 Hz-1/2. Finally, by 3-order demodulation technique, we can succeed to stabilize the laser frequency at the center of saturation dip. The stability of frequency is about 120 kHz.