RESUMEN
A high optical signal-to-noise ratio (OSNR) single-frequency 2 µm Brillouin fiber laser (BFL) with watt-level output and high transfer efficiency is demonstrated for the first time to the best of our knowledge. The Brillouin pump is constructed with a two-stage thulium-doped fiber amplifier (TDFA) seeded by a 2 µm laser diode, providing 4.02 W average power with 1 MHz linewidth. Using an optimized length of 14 m for the Brillouin ring cavity, the BFL works stably in single-mode region with 8 kHz linewidth because of the linewidth narrowing effect. The transfer efficiency is 51% with 1.08 W output power and 62 dB OSNR for 3.22 W pump power.
RESUMEN
Performance of on-off keying (OOK), digital pulse interval modulation (DPIM), and pulse position modulation (PPM) schemes are researched for ground-to-satellite laser uplink communications. Packet error rates of these modulation systems are compared, with consideration of the combined effect of intensity fluctuation and beam wander. Based on the numerical results, performances of different modulation systems are discussed. Optimum divergence angle and transmitted beam radius of different modulation systems are indicated and the relations of the transmitted laser power to them are analyzed. This work can be helpful for modulation scheme selection and system design in ground-to-satellite laser uplink communications.