Construction of Wavelength/Time Codes for Fiber-Optic CDMA Networks

Abstract

Fiber-optic code-division multiple-access (FO-CDMA) technology for high-speed access networks has attracted a lot of attention recently. Constructions of 2-D codes, suitable for incoherent wavelength/time (W/T) FO-CDMA, have been proposed to reduce the time spread of the 1-D sequences. The W/T construction of codes can be broadly classified as 1) hybrid sequences and 2) matrix codes. Earlier, we reported a new family of unipolar wavelength/time multiple-pulses-per-row (W/T MPR) matrix codes that have good cardinality, spectral efficiency and at the same time have the lowest off-peak autocorrelation and cross-correlation values equal to unity. In this paper, we propose an algorithm to construct W/T MPR codes, starting with distinct 1-D optical orthogonal codes (OOCs) of a family as the row vectors of the code. The 2-D optical orthogonal signature pattern codes (OOSPCs), which are also constructed from 1-D OOCs, need much higher temporal length than that of W/T MPR codes, to construct codes of given cardinality and weight. Representation of the results of the codes generated using the algorithm are presented and the correlation properties are verified. We have analyzed the performance of the W/T MPR codes considering multiple access interference as the main source of noise. Also, we have compared cardinality and spectral efficiency of the codes with other W/T codes.