摘要:

The transmission and reflection spectrum of the coupled-waveguide Bragg-reflection filter are computed by a new method. The filter is based on the use of a Bragg grating to obtain contradirectional coupling between two dissimilar waveguides. The analysis shows that the tuning range should be similar to that of a simple Bragg grating filter, but with the advantage of having the output separated from the input. This device could also be used as a selective tap in a wavelength-division multiplexing system

DOI:10.1049/ip-j.1993.0045

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Channel transmission error arguments show how the size of an all-optical multihop network employing deflection routing is limited for a given optical bit rate. These limits are quantified for nonregenerative all-optical mesh networks such as Manhattan Street network and ShuffleNet employing solitons. It is found that the node-to-node fibre span cannot exceed a few kilometres for network sizes up to 400 nodes when the optical bit rate is as high as 100 Gbit/s if the packet error rate is to be bounded below 10−6.

DOI:10.1049/ip-j.1993.0046

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Two new contributions on the subject of polarisation-independent switches are presented. The first concerns experimental results on a polarisation-independent directional coupler with extremely relaxed fabrication tolerances, and the second is a proposal for a digital optical switch in unconventional orientation.

DOI:10.1049/ip-j.1993.0047

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Detailed calculations have been made of the optical switching behaviour in twin-guide travelling-wave laser amplifiers driven with equal current in each guide. For typical device parameters, appropriate to 1.55 μm InGaAsP devices, the analysis indicates that the switching occurs at about one quarter of the saturated power, which in practice means at about 1 mW for an unsaturated gain of 26 dB. The factors influencing this switching power are discussed and some suggestions offered as to ways of reducing the value.

DOI:10.1049/ip-j.1993.0048

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The InP digital optical switch presented is compared with other types of switch. In addition to reverse- and forward-bias operation, its push-pull mode of operation is demonstrated for the first time, as well as its high-speed behaviour. The high potential of the digital optical switch and switching matrix fabrication are described. The results show that the InP-based digital optical switch has to be considered as a key element for guided-wave photonic switching.

DOI:10.1049/ip-j.1993.0049

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Fibre optical communications switching networks with optical nodes containing optically passive (lithium niobate) or active (indium phosphide) space switches as well as erbium-doped fibre amplifiers are analysed numerically from a power budget point of view. Calculations include spectral gain characteristics and gain saturation in the optical amplifiers caused by accumulated amplified spontaneous emission and optical signals. Active switches require less transmitter optical power than the passive switches for passage through a given number of nodes because of their lower losses. Critical parameters are identified as the loss in the optical node and the saturation output power of the optical amplifiers.

DOI:10.1049/ip-j.1993.0050

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A study is made of the reverse-biased optical switches in a MESFET geometry. Carriers are controlled in the switching region by the gate voltage which can enhance the feasibility of carrier-induced devices in high-speed data communication, optical computing and photonic switching. A waveguide optical switch in a conventional MESFET geometry is proposed which gives an extinction ratio better than 8.75 dB at the operating voltage of 7 V. A further optimised structure to reduce the operating voltage and get better optical characteristics has been designed. Computer analysis of the two-dimensional electrostatic potential and the number of depleted carriers shows that diffused carriers are depleted by applying drain and gate voltages of 2 and −2 V, respectively. The beam propagation method applied to wave propagation shows an on/off ratio better than 15 dB. This considerably improves both electrical and optical characteristics of carrier injection-type optical switches.

DOI:10.1049/ip-j.1993.0051

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A comprehensive summary of the operation of two-contact semiconductor self-pulsating laser diode (SP—LD) in both return-to-zero (RZ) and non-return-to-zero (NRZ) optical transmission systems is presented. Results demonstrate that this type of device has great potential as the basis for all-optical clock recovery circuits at multi-Gbits rates for switching applications. Results describe the basic device behaviour showing how zinc doping the shorter (absorber) region of the device enables repeatable and controlled GHz pulsations, within the range ∼ 0.6 to > 5.5 GHz and tunability (via the DC gain current) over many GHz, to be achieved. Experimental results show that the SP-LD can be locked with μW of incident power to produce a locked oscillator with a linewidth of < 10 Hz at 5 GHz and with 20 dB power gain across the device. New results, addressing the pattern dependence, demonstrate that long breaks (up to ∼ 30 ‘zeros’) in the clock can be accommodated without significant degradation of the locked clock purity; the length of break being dependent on the initial state of locking. Other new results show that the lock-up time for such circuits is of the order of 100 clock cycles. System performance is investigated using these devices within a 20 Gbit/s (4 × 5 Gbit/s) optical-time-division-multiplexed demonstrator; the results showing no significant degradation of the bit-error-ratio performance. Other system results at 3.2 Gbit/s show that this technique can be applied to NRZ systems when also utilising a nonlinear effect within a similar device biased below threshold, and identifying the differences from RZ operation. These results show that such an approach could provide major benefits in developing the next generation of telecommunications networks.

DOI:10.1049/ip-j.1993.0052

出版商:IEE    

年代:1993

数据来源: IET

摘要:

A novel architecture for optical TDM switching is introduced, comprising 2 × 2 optical switches integrated onto large substrates, and fibre delay lines. The performance of the architecture is characterised in terms of switch count, crosstalk, frame delay, attenuation and control complexity. It is shown that in the near future a system with 16 inputs and outputs, handling a total of 4096 TDM channels, could be demonstrated experimentally with 448 switches on six substrates using state-of-the-art technology.

DOI:10.1049/ip-j.1993.0053

出版商:IEE    

年代:1993

数据来源: IET