QPPM receiver for free-space laser communications
Abstract
A prototype receiver developed at NASA Lewis Research Center for direct detection and demodulation of quaternary pulse position modulated (QPPM) optical carriers is described. The receiver enables dual-channel communications at 325-Megabits per second (Mbps) per channel. The optical components of the prototype receiver are briefly described. The electronic components, comprising the analog signal conditioning, slot clock recovery, matched filter and maximum likelihood data recovery circuits are described in more detail. A novel digital symbol clock recovery technique is presented as an alternative to conventional analog methods. Simulated link degradations including noise and pointing-error induced amplitude variations are applied. The bit-error-rate performance of the electronic portion of the prototype receiver under varying optical signal-to-noise power ratios is found to be within 1.5-dB of theory. Implementation of the receiver as a hybrid of analog and digital application specific integrated circuits is planned.
- Publication:
-
Proposed for presentation at the 15th International Communications Satellite Systems Conference
- Pub Date:
- January 1994
- Bibcode:
- 1994sasy.conf.....B
- Keywords:
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- Bit Error Rate;
- Digital Electronics;
- Optical Communication;
- Optical Equipment;
- Receivers;
- Signal Processing;
- Digital Techniques;
- Logic Circuits;
- Matched Filters;
- Pulse Modulation;
- Signal To Noise Ratios;
- Communications and Radar