Bandwidth compression

Abstract: This paper presents an analysis of optical buffers based on slow-light optical delay lines. The focus of this paper is on slow-light delay lines in which the group velocity is reduced using linear processes, including electromagnetically induced transparency (EIT), population oscillations (POs), and microresonator-based photonic-crystal (PC) filters. We also consider slow-light delay lines in which the group velocity is reduced by an adiabatic process of bandwidth compression. A framework is developed for comparing these techniques and identifying fundamental physical limitations of linear slow-light technologies. It is shown that slow-light delay lines have limited capacity and delay-bandwidth product. In principle, the group velocity in slow-light delay lines can be made to approach zero. But very slow group velocity always comes at the cost of very low bandwidth or throughput. In many applications, miniaturization of the delay line is an important consideration. For all delay-line buffers, the minimum physical size of the buffer for a given number of buffered data bits is ultimately limited by the physical size of each stored bit. We show that in slow-light optical buffers, the minimum achievable size of 1 b is approximately equal to the wavelength of light in the buffer. We also compare the capabilities and limitations of a range of delay-line buffers, investigate the impact of waveguide losses on the buffer capacity, and look at the applicability of slow-light delay lines in a number of applications.

Abstract: This paper introduces a class of finite-state algorithms which characterize self-similar space-filling curves. The curves enable one to continuously map a line onto an N -dimensional cube, and find application in compressing the bandwidth of arbitrary waveforms. The bandwidth compression is effected in return for an increased susceptibility of the signal to perturbations. The algorithms are represented in a diagrammatic form which enables one to convert the N coordinates of a point in a cube into a single number representing the distance along a space-filling curve, or vice-versa, merely by visual inspection. The diagrams are always finite in size and may be constructed by following a rather simple numerical procedure.

Abstract: The transmitter/receiver system for bandwidth or data-rate compression of television signals, described herein, is a prototype model of the experimental system of Cherry et al. [1]. The system is suitable for both black-and-white or half-tone pictures, in realistic noise conditions. The system parameters my be adjusted so that an optimum run-length encoding may be found; the great advantages of run-length quantizing are shown, especially with regard to practical instrumentation, leading to the use of buffer stores of modest capacity. One particular cheap form of receiver operates on a quantized-variable-velocity principle and, being much more simple and cheap than the transmitter, is suitable for use in situations requiring many receivers.

Abstract: Researchers demonstrate bandwidth compression of single photons from 1740 GHz to 43 GHz, and tuning the center wavelength from 379 nm to 402 nm. The scheme relies on sum-frequency generation with frequency-chirped laser pulses. This technique enables interfacing between different quantum systems whose absorption and emission spectral properties are mismatched.