Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Noise Reduction in Photorefractive Image Amplification by Contradirectional Two-Wave Mixing in Rh-Doped BaTiO 3 Crystal

Abstract: Low noise image amplification owing to contradirectional two-wave mixing (CTWM) is proposed and demonstrated in Rh-doped BaTiO3 crystal. Comparing with the conventional forward two-wave mixing scheme, an enhancement of signal-to-noise ratio in the order of 103 is obtained. The theoretical analyses are presented and give a reasonable explanation for the experimental results. The further discussion shows that CTWM scheme can also reduce the influence of the crystal absorption and crystal size on the two-wave mixing process to rise the signal beam gain.

Cramér–Rao Bounds for Beam Tracking With Photon Counting Detector Arrays in Free-Space Optical Communications

Abstract: Optical beam center position on an array of detectors is an important parameter that is essential for estimating the angle-of-arrival of the incoming signal beam. In this paper, we have examined the beam position estimation problem for photon-counting detector arrays, and to this end, we have derived and analyzed the Cramer-Rao lower bounds on the mean-square error of unbiased estimators of beam position. Furthermore, we have also derived the Cramer-Rao lower bounds of other system parameters such as signal peak intensity, and dark current noise power, on the array. In this sense, we have considered robust estimation of beam position in which none of the parameters are assumed to be known beforehand. Additionally, we have derived the Cramer-Rao lower bounds of beam and noise parameters for observations based on both pilot and data symbols of a pulse position modulation (PPM) scheme. Finally, we have considered a two-step estimation problem in which the signal peak and dark current noise intensities are estimated using a method of moments estimator, and the beam center position is estimated with the help of a maximum likelihood estimator.

Laser ultrasonic wave receiver

Abstract: PROBLEM TO BE SOLVED: To provide a monitoring function for a receiver condition suitable for use in a field, and the optimization function for the receiver condition, and to allow a precise flaw detection operation under a stable condition over a long period. SOLUTION: This laser ultrasonic wave receiver is provided with a laser oscillation means PLD constituted of a seed laser oscillation means 1 for oscillating a laser beam IL emitted to a surface of a measured object TP to detect an ultrasonic signal, and a light amplifying means 2 for amplifying pulse-likely an oscillated light from the seed laser oscillation means 1, an optical interference means FP for extracting the ultrasonic signal, from a signal beam of the laser beam IL reflected/scattered on the surface of the measured object TP, a signal processing means 12 for processing an output signal from the optical interference means FP, and a state detecting means 16 for detecting a state of the laser oscillation means PLD. COPYRIGHT: (C)2007,JPO&INPIT

Optical amplifying method

Abstract: PURPOSE:To provide the optical amplifying method which can improve the pump efficiency of an excited beam and can efficiently amplify a signal beam even without using any LD for large output pump. CONSTITUTION:At the optical amplifying method to amplify a signal beam (a) transmitted through an optical amplifier 1 by inputting an excited beam (b) from an LD 2 for pump to the fiber type optical amplifier 1 which Er is doped, in the excited beam (b), an unused excited beam (c) not used for optical amplification is extracted from the signal beam (a) on the output side of the amplifier 1, and the extracted unused beam (c) is returned to the fiber type optical amplifier 1 and used as the excited beam again.