Towards self-clocked gated OCDMA receiver

S Idris,I Glesk,T Osadola

doi:10.2971/jeos.2013.13013

S Idris, I Glesk + Show 1 more

Open Access

https://doi.org/10.2971/jeos.2013.13013

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Abstract

A novel incoherent OCDMA receiver with incorporated all-optical clock recovery for self-synchronization of a time gate for the multi access interferences (MAI) suppression and minimizing the effect of data time jitter in incoherent OCDMA system was successfully developed and demonstrated. The solution was implemented and tested in a multiuser environment in an out of the laboratory OCDMA testbed with two-dimensional wavelength-hopping time-spreading coding scheme and OC-48 (2.5 Gbp/s) data rate. The self-clocked all-optical time gate uses SOA-based fibre ring laser optical clock, recovered all-optically from the received OCDMA traffic to control its switching window for cleaning the autocorrelation peak from the surrounding MAI. A wider eye opening was achieved when the all-optically recovered clock from received data was used for synchronization if compared to a static approach with the RF clock being generated by a RF synthesizer. Clean eye diagram was also achieved when recovered clock is used to drive time gating.

Highlights

Optical code division multiple access (OCDMA) is a multiple access technique where signal is transmitted in the form of unique codes
This is the case for two-dimensional wavelength-hopping time-spreading (2DWHTS) OCDMA codes and is a result of a nonzero cross correlation among codes used by simultaneous users [1]
In this paper we report for the first time a demonstration of an incoherent OCDMA receiver with the self-clocked time gate for multi-access interference (MAI) reduction

Summary

INTRODUCTION

Optical code division multiple access (OCDMA) is a multiple access technique where signal is transmitted in the form of unique codes. FBGs for encoding and decoding of WHTS optical codes in OCDMA systems by spreading multiple wavelengths within a bit period and placing them into time chips at the transmitter end and reciprocally de-spreading them and forming an autocorrelation peak at the receiver end is a widely known technique [21, 22]. For implementation of the optical time gating technique an optical clock is needed to precisely control the position of the switching window of the time gate for allowing to pass the user decoded OCDMA data referred to as autocorrelation peak [17] while blocking the MAI known as cross-correlations that falls outside of it (see Figure 1). The all-optically generated clock by the AOCR was evaluated by using BER tester for its stability and later for its suitability to be used as the optical control to drive the SOA-MZI all-optical switch (TG)

EXPERIMENTAL RESULT

AOCR evaluation

CONCLUSION