Abstract
This paper proposes a more realistic optical code
division multiple access (OCDMA) sequence bit error
rate (BER) evaluation technique for multiple access
interference (MAI) during transmission over optical fiber.
The technique provides a filter for all possible non-zero
correlations events that may occur during transmission,
leaning on all positive time-frequency intervals for
a 2-D OCDMA, or all positive time intervals for 1-
D OCDMA. As a wavelength hopping/time sequence
(WH/TS) suggests, this MAI evaluation on a 2-D OCDMA
consists of one-coincidence frequency hopping code
optical orthogonal code (OCFHC-OOC) Bragg gratings
encoded signals. For a better assessment of the timeintervals,
we also investigate the 1-D OCDMA OOC since
the OOC is the time spreading component of the OCFHCOOC
sequence. In both cases, the signals of interest are
transmitted using simple On-Off keying with non-returnto-
zero signalling and direct detection at the receiver.
The received signal contains multiple access interference
from other users’ coincidence correlations and the inband
random correlations from the photodiode due to
square detection. The MAI mean and variance are
analysed over all possible non-zero wavelength-time
interval pairs of sequences and the standard Gaussian
approximation is used to evaluate the bit error rate.
Further, the resulting bit error rate is then compared with
that of the user coincidence-based evaluation technique.