Synchronization of high-frequency chaotic optical pulses.
Synchronization of high-frequency chaotic optical pulses is demonstrated in two semiconductor lasers with delayed optoelectronic feedback. The difference between synchronization and modulation is discussed. Evidence is presented to show that true synchronization, rather than modulation or amplification, is accomplished in our optoelectronic feedback system.
Chaos Applications in Optical Communications
The first part of this chapter provides an introduction to the cryptographic techniques applied in contemporary communication systems using algorithmic data encryption. However, there are several other techniques that may provide additional security in the transmission line, taking advantage of the properties of the communication type and the transmission medium. Optical communication systems that exchange light pulses can exploit some properties in the physical layer for securing the communicating parts. Such properties lead to data encryption through methods such as quantum cryptography and chaos encryption, which are described in the second part. Since this chapter focuses on the chaos encryption technique, the third part describes the potential of optical emitters to generate complex chaotic signals using different techniques. Such chaotic carriers can be potentially used for broadband message encryption. The fourth part analyzes the phenomenon of synchronization between chaotic signals. A receiver capable of synchronizing with the emitted carrier can reject the carrier as well and recover the encrypted message. The fifth part presents various message encryption techniques that can be applied for optical communication systems that are able to operate on the basis of a chaotic carrier. Additionally, an example of a preliminary system that has been tested successfully is presented. In the sixth part, contemporary systems based on all-optical or optoelectronic configurations are presented, incorporating also as the transmission medium fiber spools or installed fiber networks. Finally, the seventh part concludes with the potential of this method to guarantee secure optical communications.
Turbine blade temperature calculation and life estimation - a sensitivity analysis
Abstract The overall operating cost of the modern gas turbines is greatly influenced by the durability of hot section components operating at high temperatures. In turbine operating conditions, some defects may occur which can decrease hot section life. In the present paper, methods used for calculating blade temperature and life are demonstrated and validated. Using these methods, a set of sensitivity analyses on the parameters affecting temperature and life of a high pressure, high temperature turbine first stage blade is carried out. Investigated uncertainties are: (1) blade coating thickness, (2) coolant inlet pressure and temperature (as a result of secondary air system), and (3) gas turbine load variation. Results show that increasing thermal barrier coating thickness by 3 times, leads to rise in the blade life by 9 times. In addition, considering inlet cooling temperature and pressure, deviation in temperature has greater effect on blade life. One of the interesting points that can be realized from the results is that 300 hours operation at 70% load can be equal to one hour operation at base load.