We report a low coherence supercontinuum source with high-repetition rate and compare its spectral width and coherence under conditions of different pump pulse. The repetition rate of supercontinuum source is 4GHz and the spectrum width of supercontinuum is nearly 400nm. The supercontinuum spectral width and coherence under different pump pulse duration were compared, which indicates that with the same pump power, as the pump pulse duration increases, the width and coherence of the supercontinuum both decreases. We also compare the coherence of the supercontinuum with different pump power, as the pump power increases, the coherence of the supercontinuum deteriorates. The coherence of supercontinuum is related to pulse width and power of injected pulse.
In this paper, we use a pulse trigger to manipulate soliton-fission in supercontinuum generation process by modulation instability (MI) in ~picosecond pump scheme and we demonstrate the prior performance of generated supercontinuum compared to non-trigger situation. A distributed feedback (DFB) laser is modulated into a pulse source with a high repetition rate of 4GHz by pulse amplitude modulation (PAM) and an adiabatic soliton compression (ASC) method is used to compress pulse width from 8.2ps to 3.3ps. It is observed that threshold of SC generation is relatively lower when the trigger is used. As pump light coupled with pulse trigger launch into a 400m high non-linear dispersion-shifted fiber (HNL-DSF), the generated supercontinuum is nearly 100nm wider in redshifted side and exhibit better stability than untriggered one.
In this paper, we experimentally demonstrated a free space optical communication system transmission based on continuous wide-spectrum laser at 10Gbit/s over 1km simulated atmospheric channel. The wide-spectrum laser is part of supercontinuum generated by using a self-made picosecond mode-locked laser based on Raman gain solution effect to pump a dispersion compensation fiber which dispersion coefficient are D=-135ps/nm ⋅ km@1550nm. A 10Gbit/s NRZ signal was then modulated on the wide-spectrum laser and transmitted into a tunable simulated atmospheric turbulence pool which can simulate atmospheric turbulent intensity up to 0.59cm of coherent length. Scintillation intensities and bit error rates of transmission based on wide-spectrum laser and narrow linewidth laser were compared. The results show that communication sensitivity reached -10.98dBm at FEC limit. which has 1.53dB improvement comparing with FSO communication system using narrow linewidth laser under weak turbulent condition.
The transmission characteristics of 384 Gbit / s free-space laser link with dense wavelength division multiplexing (DWDM) are demonstrated, with channel spacing of 100 GHz. We use a simulated atmosphere channel with a tunable weak turbulence, and bit error rate (BER) curves of back-to-back transmission, which are measured and contrasted, respectively. To our knowledge, it is the first demonstration in the research of DWDM-DP-QPSK high-speed free-space optical (FSO) transmission in an atmospheric channel with tunable turbulence. For 100 GHz channel spacing, receiving sensitivities can be −33.6, −32.7, and −32.1 dBm for 300, 336, and 384 Gbit / s DWDM-PM-QPSK signals, respectively, at BER of 3.8 × 10 − 3 (FEC limit). In comparison with −37.6, −36.1, and −35.1 dBm for B2B case, the power penalties are 4, 3.4, and 3.0 dB, respectively. This study indicates that high-speed coherent DWDM-DP-QPSK FSO transmission is feasible.