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Erbium doped fiber is a main component of Erbium Doped Fiber Amplifiers (EDFAs), which is wildly used in optical communication. Erbium doped fiber is a good sensing material of fluorescence temperature sensors as well. The Erbium-doped-fiber temperature sensors can operate under high temperature up to 1 100 °C.Fluorescence sensors show considerable promise, with the advantage of being intensity independent. Following the termination of a square excitation light pulse, the fluorescence signal is an exponential decay, which decay lifetime depends on the temperature and can be measured by several methods. The decay acquisition and estimation methods are one kind of them. Different arithmetic is developed such as the Marquardt method, the Prony method and the log-fit method.A new estimation method is given in this paper, basing on the FFT (Fast Fourier Transform) and the Taylor series. The fluorescence lifetime can be calculated from the items of the FF1' with different accuracy. This method is especially designed for the long-fluorescence-lifetime system, for example, Erbium-doped-fiber sensing system with lifetime up to lOms. However this method can be used for other fluorescence material also with a little shift. The advantages of this method include high accuracy, quick processing, independence on base offset etc.The effect of this method is discussed and compared with other estimation methods by numerical simulation and experiment results.

In this paper, the method will be introduced, it's called Quantum Nondemolition measurement. The purpose is to realize a new measuring method to surpass quantum limit. It provides a new mithod of overcoming quantum noise. In principle, it can use any precision to detect a certain weak signal. Finally. the application of QND Measurement in optical communication will be introduced. Keywords: quantum limit, measurment, quantum optical communication 1. QUANTUM NONDEMOLITON MEASUREMENT 1.1 Basic concept Quantum Nondemolition Measurement (QND) was first suggested by the former Russian V.B.Braginsky et a11'1H.At the time they wanted to explore the weak gravity wave in the astrophysics. The gravity wave is rather weak, even lower than standard quantum fluctuation noise and the aim of QND is to overcome the noise, surpass the quantum limitation to reach the ultrahigh accuracy which the classical measurement method can not arrive at.The well-known uncertainty relation shows two non-corresponding relations between the conjugate mechanics and heavy quantum fluctuation. For example, [x, p} = i, then xp h,where AA = { _ <> 2} 1/2 , If we me a precise measurement on one of them (such as measurement of to to make Lr smaller), the fluctuatuon of another (such as p) mechanics quantity will become larger. In most cases, the fluctuation of latter mechanics quantity wifi couple back through certain procedure in the evolution of the system to make the previous fluctuation of the system to make the previous fluctuation of the former mechanics quantity become larger and the fluctuation is random and Supported by Heilongjiang Natural Science Fund O-8194-2294-O/96/$6.OO SPIE Vol. 2893 /557 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

Abstract：The need of understanding and teaching about wave-particle duality if light with gets more and more apparent in the background of the attention of modern physics. As early as the beginning of twentieth Century, Einstein dared to "deny" the development of a very perfect light electromagnetic theory, so that the quantum of light can be developed. In 1924, De Broglie put forward wave-particle duality if light to other micro particles and the concept of matter wave, pointed out that all micro particle has wave-particle duality. This is a very abstract concept for students, most college physics teaching all lack of demonstration about particle duality of light. The present article aims to contribute to demonstrate the wave-particle duality of light at the same time using a simple way based on fiber optical tweezers. It is hoped that useful lesson can be absorbed so that students can deepen the understanding of the particle and wave properties of light. To complement the demonstration experiment for this attribute light has momentum.

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