A spread spectrum multiplexing (SSM) system for an array of reflective, frequency-out fiber optic sensors of identical characteristics has been developed. This system allows accessing of a large number of sensors with high sampling frequency of up to a few MHz and simultaneously permits a considerable improvement of the system optical power budget over single pulse time-division multiplexing methods. An experimental SSM system has been assembled and tested and the experiments have successfully demonstrated the passive multiplexing of eight reflective frequency-out fiber optic sensors with a vibration frequency of 17.36 kHz. Crosstalk of approximately -22 dB has been observed, which is in agreement with theoretical results expected from consideration of the code length of the pseudorandom bit sequence used and the sensor number in the network. Additionally, a novel digital PRBS exhibiting zero auto-correlation at non-zero delays has been modelled and experimentally tested, yielding promising results for sensor multiplexing.

Date Published: 5 March 1993
PDF: 10 pages
Proc. SPIE 1797, Distributed and Multiplexed Fiber Optic Sensors II, (5 March 1993); doi: 10.1117/12.141292

Published in SPIE Proceedings Vol. 1797:
Distributed and Multiplexed Fiber Optic Sensors II
John P. Dakin; Alan D. Kersey, Editor(s)