Design And Development Of Simplex-To-Full Duplex Converter (Sfdc)

Existing fiber optic network employ simplex transmission scheme where two fibers are needed, each to transmit and received signals between connecting points. The increasing demand has seen fiber, particularly in the metro area, are used up in no time. The conventional solution is to install new fibers to support new customers. However fiber installation are always expensive and fussy. Thus, a new approach is desirable in solving the problem. In this thesis, new technique is proposed to double the link bandwidth by fully utilizing the two fiber cores. The technique is based on the basic ligthwave principle that two photons do not know each other. Therefore the optical signals, transmitted and received ones can be made to propagate in the opposite direction in the same fiber, as long as they can be split and isolated at the receiver side. The techniques proposed here in achieving the goal is simple but quite powerful. The components used in developing the device are all passive products. Each of them was characterized prior to developing them according to the design. Then the whole device was tested further both on its own, and in network environment.From the tests conducted, it is important to reduce the reflection from transmitters to adjacent receivers, which is due to SFDC directivity. From the study it is found that the minimum isolation needed between actual and reflected signal to achieve good transmission quality is around 13 dB. Testing on SDH network was successfully conducted on over 50 km fiber link with zero errors. The test was conducted in both laboratory and testbed environment, with cooperation from Telekom Malaysia. Testing on WDM system was conducted in laboratory environment only. The test shows that no error is introduced. Finally it is concluded that SFDC is reliable to be used as a device to realize full duplex transmission, as its realization would result in huge increase in fiber bandwidth utilization with minimum installation and maintainance complexity and cost.

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