Coherent power combination of semiconductor lasers using optical phase-lock loops

Heterodyne optical phase-lock loops (OPLLs) enable the precise electronic control over the frequency and phase of a semiconductor laser (SCL) locked to a ldquomasterrdquo reference laser. One of the more interesting applications of OPLLs is the creation of coherent arrays by locking a number of ldquoslaverdquo SCLs to a common master laser. In this paper, we demonstrate the coherent power combination of various high-power semiconductor lasers using OPLLs in both the filled-aperture and tiled-aperture configurations. We further demonstrate the electronic control over the phase of each individual SCL using a voltage-controlled oscillator. It is feasible to combine a large number of SCLs using this approach, leading to compact, efficient, and cost-effective high-power and high-radiance optical sources

Acquisition times of carrier tracking sampled data phase-locked loops

Phase acquisition times of type II and III loops typical of the Advanced Receiver are studied by computer simulations when the loops are disturbed by gaussian noise. Reliable estimates are obtained by running 5000 trials for each combination of loop signal-to-noise ratio (SNR) and frequency offset. The probabilities of acquisition are shown versus time from start of acquisition for various loop SNRs and frequency offsets. For frequency offsets smaller than one-fourth of the loop bandwidth and for loop SNRs of 10 dB and higher, the loops acquire with probability 0.99 within 2.5 B sub L for type II loops and within 7/B sub L for type III loops

Architectures for RF Frequency synthesizers

Frequency synthesizers are an essential building block of RF communication products. They can be found in traditional consumer products, in personal communication systems, and in optical communication equipment. Since frequency synthesizers are used in many different applications, different performance aspects may need to be considered in each case. The main body of the text describes a conceptual framework for analyzing the performance of PLL frequency synthesizers, and presents optimization procedures for the different performance aspects. The analysis of the PLL properties is performed with the use of the open-loop bandwidth and phase margin concepts, to enable the influence of higher-order poles to be taken into account from the beginning of the design process. The theoretical system analysis is complemented by descriptions of innovative system and building block architectures, by circuit implementations in bipolar and CMOS technologies, and by measurement results. Architectures for RF Frequency Synthesizers contains basic information for the beginner as well as in-depth knowledge for the experienced designer. It is widely illustrated with practical design examples used in industrial products.\ud Written for:\ud Electrical and electronic engineer