Modeling of Ti:LiNbO3 waveguide devices. II.S-shaped channel waveguide bends

For pt.I see ibid., vol.7, no.3, p.533-9, 1989. Directly from design and fabrication parameters, the performances of S-shaped channel waveguide bends are calculated by using the same formalism described in Part I. The calculated insertion losses of S-shaped waveguide bends are in agreement with all experimental data found in the literature. Different S-curves for short-length low-loss waveguide bend design were also studied. Results show that the widely used sine-generated S-curve does not provide lower insertion loss than other S-curves     

Modeling of Ti:LiNbO3 waveguide devices. I. Directionalcouplers

An efficient modelling method to simulate Ti-indiffused LiNbO₃ channel waveguide devices from their design and fabrication parameters is discussed. Procedures are: (1) derivation of the two-dimensional (2-D) refractive index profile; (2) transformation of the 2-D transverse refractive index profile to its one-dimensional (1-D) effective index profile; and (3) use of the 2-D beam propagation method to analyze the device performance. With slight consistent adjustments on Ti-induced refractive index changes, it is possible to calculate the performance of directional couplers in good agreement with experimental measurements. This modeling method can be used to predict performance of future devices     

Digital and quasi-linear electrooptic modulators synthesized from directional couplers

By synthesizing from cascaded directional couplers, we propose new designs to achieve digital and quasi-linear electrooptic modulations. For the digital modulator, a nearly perfect on-state or off-state can be obtained in a broad range of modulation voltages. The calculated switching voltage can be as low as the drive voltage of a conventional directional coupler. The quasi-linear modulator is achieved by adding a set of compensating electrodes to a foreshortened directional coupler. Deviation from a linear voltage-intensity relationship of less than 1 percent can be obtained over a 93.5 percent modulation depth. The calculated second harmonic and the third order intermodulation distortions are -18.3 and -32.6 dB, respectively.     

Simultaneous optical amplification, detection, and transmissionusing in-line semiconductor laser amplifiers

It is demonstrated that in broadband networks inline semiconductor laser amplifiers (SLAs) that provide system gain can also be used as simultaneous transceivers for additional channels at higher frequencies. In the experiment, an SLA in a 622-Mb/s baseband system provided a 6.5-dB fiber-to-fiber gain and served simultaneously as a receiver and a transmitter for two frequency-shift-keying (FSK) channels (each carrying 10 Mb/s) at 755 and 1075 MHz, respectively. Such optical amplifiers/transceivers are potentially useful in broadband digital networks with out-of-band signaling channels or in subcarrier multiple-access networks     

Performance analysis of a solar-powered/fuel-assisted Rankine cycle with a novel 30 hp turbine

The subject of this analysis is a novel hybrid steam Rankine cycle, which was designed to drive a conventional open-compressor chiller, but is equally applicable to power generation. Steam is to be generated by the use of solar energy collected at about 100°C, and is then to be superheated to about 600°C in a fossil-fuel fired superheater. The steam is to drive a novel counter-rotating turbine, and most of its exhaust heat is regenerated. A comprehensive computer program developed to analyze the operation and performance of the basic power cycle is described. Each component was defined by a separate subroutine which computes its realistic off-design performance from basic principles. Detailed predicted performance maps of the turbine and the basic power cycle were obtained as a function of turbine speed, inlet pressure, inlet temperature, condensing temperature, steam mass flow rate, and the superheater's fuel consumption rate. Some of the major conclusions are: (1) the turbine's efficiency is quite constant, varying in the range of 68.5–76.5 per cent (75 per cent at design) for all conditions, (2) the efficiency of the basic power cycle is 18.3 per cent at design, more than double as compared to organic fluid cycles operating at similar solar input temperatures, at the expense of adding only 20 per cent non-solar energy. This, combined with the fact that actual organic Rankine cycles operate typically at temperatures above 140°C, predicts that this system would be economically superior by using less than half of the collector area and by also using less expensive collectors.