According to the characteristic of free space optical communication

and on the basis of theoretical analysis and numerical emulation

we bring forward a design of long wavelength optical transmitter applied to inter satellite optical communication. We analyze the influency of the amplified spontaneous emission on the gain of SNR under the high power signal and pump condition and calculate the optimized caliber of the optical antenna with the OOK modulation on the basis of the requirement to the BER of the inter satellite optical communication system.