Chirp

About: Chirp is a research topic. Over the lifetime, 14403 publications have been published within this topic receiving 178726 citations.

Novel C-IPDM Signal Format for Suppression of Polarization Mode Dispersion

Abstract: A novel chirped intra-bit polarization diversity modulation (C-IPDM) signal format is proposed. The transmission performance of C-IPDM is compared to NRZ, RZ and the common IPDM in terms of the PMD tolerance by simulation in a 40 Gb/s system. The results show that the C-IPDM format can reduce the effects of second-order PMD significantly due to the chirping characteristic and the system Q-factor is increased especially in high PMD systems.

Application of convolve-multiply-convolve SAW processor for satellite communications

Abstract: There is a need for a satellite communications receiver than can perform simultaneous multi-channel processing of single channel per carrier (SCPC) signals originating from various small (mobile or fixed) earth stations. The number of ground users can be as many as 1000. Conventional techniques of simultaneously processing these signals is by employing as many RF-bandpass filters as the number of channels. Consequently, such an approach would result in a bulky receiver, which becomes impractical for satellite applications. A unique approach utilizing a realtime surface acoustic wave (SAW) chirp transform processor is presented. The application of a Convolve-Multiply-Convolve (CMC) chirp transform processor is described. The CMC processor transforms each input channel into a unique timeslot, while preserving its modulation content (in this case QPSK). Subsequently, each channel is individually demodulated without the need of input channel filters. Circuit complexity is significantly reduced, because the output frequency of the CMC processor is common for all input channel frequencies. The results of theoretical analysis and experimental results are in good agreement.

Characterization of Chirped Fiber Bragg Gratings: Identification and Removal of Cladding-Mode Perturbations in Measurement Data

Abstract: In chirped fiber Bragg gratings, structural perturbations and the effect of cladding-mode coupling are shown to be distinguishable. To this end, the absolute value and the phase of the experimentally determined complex coupling coefficient are Fourier transformed separately, yielding a set of discrete lines that can be clearly identified and be traced back to cladding-modes. Removing these lines yields the grating properties in the absence of cladding-modes.

Integrated photonic devices for fiber optic communication systems

Abstract: Fabrication and epitaxial growth technology for III-V semiconductor devices have developed to the point where substantial levels of photonic integration are now feasible. Both highly complex and simple photonic integrated devices are currently the subjects of much active research and product development. These efforts are motivated by the many potential advantages of photonic integration, reduced size, lower power consumption, increased functionality, higher performance and above all else lower cost. We discuss two different examples of photonic integrated devices that demonstrate some of the significant performance advantages that can be achieved with this technology. Both devices are fabricated using our deep ridge buried heterostructure technology that combines both SAG and butt joint epitaxial techniques to obtain the maximum flexibility in the device design. The first device is a high-speed modulator with an integrated phase shifter that enables the transmitter chirp to be dynamically tuned. This enables the transmission performance to be optimized for different amounts of fiber dispersion. In this device the phase shifter can be driven either with a synchronous sinusoidal source or a complementary data modulation. By varying either the amplitude of the drive signal or the bias on the phase modulator the chirp of the transmitted optical pulses can be controlled. For synchronous sinusoidal or narrowband chirp control a single frequency drive signal synchronized with the data modulation is applied to the phase modulator. This signal can be used to apply either positive or negative chirp to the transmitted data bits by varying the phase and amplitude of the drive signal. A more sophisticated approach uses the complement of the data modulation signal to drive the phase modulator. This method referred to as broadband chirp control provides better compensation since it applies frequency chirp only to the transitions in the signal.