19 August 2008 Ten Gb/s optically pre-amplified RZ-DPSK for FSO communications systems with very large link losses
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Abstract
For free-space optical (FSO) communications systems, sensitive optical receivers are the key to closing the link over long distances in inter-satellite transmission scenarios, or to overcome large atmospheric attenuation in terrestrial FSO systems. We present a 10.7 Gb/s optical transmitterreceiver pair operating at 1550-nm, based on return-to-zero, differential phase-shift keying (RZDPSK). The receiver is pre-amplified and uses an optical delay interferometer and a balanced photo-receiver. The outer dimensions, the weight, and power consumption are 44×44×18 cm3, 14.1 kg, and 35 W, respectively. This optical receiver is single-mode fiber coupled. At 10.7 Gb/s, a receiver sensitivity of 27 photons/bit was measured, which yields a bit error rate of 1e-9. This is less than 1 dB from the quantum limit (22 photons/bit). Coupled with a commercial optical booster amplifier having an output power of about +37 dBm, a link loss of more than 80 dB can be bridged. In an inter-satellite communications scenario, this corresponds to several tens of thousands of kilometers. Additionally, high link losses can also be experienced in terrestrial systems as the result of atmospheric scintillation. To study this effect, the transmitter and receiver combination were tested with simulated turbulence (scintillation). A turbulence box was used to emulate different levels of scintillation under which the pre-amplified RZ-DPSK system was investigated. Results of these tests are presented.
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Christoph Wree, Charles P. Collier, Steven Lane, Alan Turney, Ben Armentrout, Jesse Yates, Nathaniel Francis, Abhay Joshi, "Ten Gb/s optically pre-amplified RZ-DPSK for FSO communications systems with very large link losses", Proc. SPIE 7091, Free-Space Laser Communications VIII, 709103 (19 August 2008); doi: 10.1117/12.793784; https://doi.org/10.1117/12.793784
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