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Optical communication with semiconductor laser diodesSlot timing recovery in a direct detection optical PPM communication system can be achieved by processing the photodetector waveform with a nonlinear device whose output forms the input to a phase lock group. The choice of a simple transition detector as the nonlinearity is shown to give satisfactory synchronization performance. The rms phase error of the recovered slot clock and the effect of slot timing jitter on the bit error probability were directly measured. The experimental system consisted of an AlGaAs laser diode (lambda = 834 nm) and a silicon avalanche photodiode (APD) photodetector and used Q=4 PPM signaling operated at a source data rate of 25 megabits/second. The mathematical model developed to characterize system performance is shown to be in good agreement with actual performance measurements. The use of the recovered slot clock in the receiver resulted in no degradation in receiver sensitivity compared to a system with perfect slot timing. The system achieved a bit error probability of 10 to the minus 6 power at received signal energies corresponding to an average of less than 60 detected photons per information bit.
Document ID
19880007534
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Davidson, F. (Johns Hopkins Univ. Baltimore, MD, United States)
Date Acquired
September 5, 2013
Publication Date
March 7, 1988
Subject Category
Communications And Radar
Report/Patent Number
NASA-CR-182464
NAS 1.26:182464
Accession Number
88N16918
Funding Number(s)
CONTRACT_GRANT: NAG-356
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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