Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling...Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling setups and procedures of these two different methods are given. It is found that a well-controlled precure step is very critical, otherwise it will result in either lower poling efficiency or damaged film. Experimental results show that contact poling does not create severe surface damage as corona poling and poling voltage is much lower, but corona poling provides higher EO effect than contact poling. Besides, contact poling can provide poling size as large as the substrate size.展开更多
Power-line networks are designed to deliver electricity. They reach most of the domiciles and other buildings nowadays, so most of the people have access to it. On the other hand the backbone for the communications ne...Power-line networks are designed to deliver electricity. They reach most of the domiciles and other buildings nowadays, so most of the people have access to it. On the other hand the backbone for the communications networks is not available in all countries especially the developing ones. A high cost and changing the design for the networks may be needed to construct this backbone. If data can be transmitted over the power-line networks, a recognized cost and time save can be achieved. In Egypt, the infrastructure is not always available for constructing a communications network backbone due to the already designed buildings before the need for these backbones. In this paper, we overcome this problem by designing a reliable Power-line Modem that operates safely on the low voltage grid. The modem is based on the Direct Sequence Spread Spectrum technique. It uses the mains zero crossing as an efficient way for the synchronization between the transmitter and the receiver. The Modem takes into account the problems of the Power-line including noise, attenuation and impedance dismatching.展开更多
A new effect of transient mode competition in directly modulated DFB laser based on equivalent phase-shift （EPS） technique is presented and studied. Since there are multi-order reflections in EPS structure and if th...A new effect of transient mode competition in directly modulated DFB laser based on equivalent phase-shift （EPS） technique is presented and studied. Since there are multi-order reflections in EPS structure and if the 0th order subgrating is properly de- signed, the transient lasing of 0th order will occur during the rising time of the injection current. As a result, transient mode competition between -lst order （main mode） and 0th order will occur accordingly. This can consume redundant carrier and suppress the transient relaxation oscillation, which may be applied in some areas like on-off switching modulation of DFB semiconductor lasers. As an example, an equivalent n phase shift （n-EPS） is carefully designed to realize the effect. In such a laser the 0th order wavelength is in the margin of the material gain region and the -1st order wavelength is around the gain peak, while the stable single longitudinal mode （SLM） operation of the -lst order is guaranteed. The simulation investigation is performed. Good results with suppressed relaxation oscillation and 1.25 Gb/s directly on-off modulation （32 dB extinction ratio） are demonstrated. We believe it provides a new kind of method for on-off switching with high extinction ratio and weak relaxation oscillation.展开更多
文摘Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling setups and procedures of these two different methods are given. It is found that a well-controlled precure step is very critical, otherwise it will result in either lower poling efficiency or damaged film. Experimental results show that contact poling does not create severe surface damage as corona poling and poling voltage is much lower, but corona poling provides higher EO effect than contact poling. Besides, contact poling can provide poling size as large as the substrate size.
文摘Power-line networks are designed to deliver electricity. They reach most of the domiciles and other buildings nowadays, so most of the people have access to it. On the other hand the backbone for the communications networks is not available in all countries especially the developing ones. A high cost and changing the design for the networks may be needed to construct this backbone. If data can be transmitted over the power-line networks, a recognized cost and time save can be achieved. In Egypt, the infrastructure is not always available for constructing a communications network backbone due to the already designed buildings before the need for these backbones. In this paper, we overcome this problem by designing a reliable Power-line Modem that operates safely on the low voltage grid. The modem is based on the Direct Sequence Spread Spectrum technique. It uses the mains zero crossing as an efficient way for the synchronization between the transmitter and the receiver. The Modem takes into account the problems of the Power-line including noise, attenuation and impedance dismatching.
基金supported by the National Natural Science Foundation of China(Grant Nos.61306068 and 61435014)the Nature Science Foundation of Jiangsu Province of China(Grant Nos.BK20130585,BK2012058 and BK20140414)National High-Tech R&D Program of China(Grand No.SS2015AA012302)
文摘A new effect of transient mode competition in directly modulated DFB laser based on equivalent phase-shift （EPS） technique is presented and studied. Since there are multi-order reflections in EPS structure and if the 0th order subgrating is properly de- signed, the transient lasing of 0th order will occur during the rising time of the injection current. As a result, transient mode competition between -lst order （main mode） and 0th order will occur accordingly. This can consume redundant carrier and suppress the transient relaxation oscillation, which may be applied in some areas like on-off switching modulation of DFB semiconductor lasers. As an example, an equivalent n phase shift （n-EPS） is carefully designed to realize the effect. In such a laser the 0th order wavelength is in the margin of the material gain region and the -1st order wavelength is around the gain peak, while the stable single longitudinal mode （SLM） operation of the -lst order is guaranteed. The simulation investigation is performed. Good results with suppressed relaxation oscillation and 1.25 Gb/s directly on-off modulation （32 dB extinction ratio） are demonstrated. We believe it provides a new kind of method for on-off switching with high extinction ratio and weak relaxation oscillation.
