Electrostatic properties of the point-plane electrode configuration are reviewed in the hyperbolic approximation. Simple expressions for the field in the neighbourhood of the tip are derived under the assumption that space-charge distortion is absent. Current induced by a charge carrier moving along a field line is investigated and the theoretical expressions are compared with experimental results. Finally, the problem of the space charge is solved along the tip axis.

A novel and simple method to measure the amplitude and the phase of optical pulses is presented. The technique basically involves modulating the optical pulse train in a particular manner and then directly examining the resultant optical spectrum. This experimental measurement technique, which is extremely accurate and sensitive and can be implemented with an all-fiber setup, permits direct measurement of the phase of the optical signal in the frequency domain. Experimental results demonstrate the use of this measurement technique for characterizing optical pulses at 10 GHz from a gain-switched laser diode.

Abstract-The authors demonstrate the use of time-division multiplexing (TDM) to realize a high capacity optical star network. The fundamental element of the demonstration network is a 10 ps, wavelength tunable, low jitter, pulse source. Electrical data is encoded onto three optical pulse trains, and the resultant low duty cycle optical data channels are multiplexed together using 25 ps fiber delay lines. This gives an overall network capacity of 40 Gb/s. A nonlinear optical loop mirror (NOLM) is used to carry out the demultiplexing at the station receiver. The channel to be switched out can be selected by adjusting the phase of the electrical signal used to generate the control pulses for the NOLM. By using external injection into a gainswitched distributed feedsack (DFB) laser we are able to obtain very low jitter control pulses of 4-ps duration (rms jitter < 1 ps) after compression of the highly chirped gain switched pulses in normal dispersive fiber. This enables us to achieve excellent eye openings for the three demultiplexed channels. The difficulty in obtaining complete switching of the signal pulses is presented. This is shown to be due to deformation of the control pulse in the NOLM (caused by the soliton effect compression).The use of optical time-division multiplexing (OTDM) with alloptical switching devices is shown to be an excellent method to allow us to exploit as efficiently as possible the available fiber bandwidth, and to achieve very high bit-rate optical networks.

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