一、引言随着光纤通信技术的发展,对光纤中光信号直接进行放大的研究引起了各国学者的重视。目前有两类光纤放大技术得到较多的研究。一类是利用光纤中的非线性效应进行光放大。另一类是将光纤的一段以受泵浦作用的有源介质构成,使信号光通过时得到放大。若仅包层由有源介质构成,则信号光通过其消失场与有源介质互作用而获得放大,这便是消失场耦合光纤放大器。本文对这类放大器进行理论分析,对由多模和单模光纤构成放 I. INTRODUCTION With the development of optical fiber communication technology, the research on amplifying the optical signal directly in optical fiber has drawn the attention of scholars all over the world. There are two types of optical fiber amplification technology to get more research. One is the use of optical fiber in the nonlinear effects of optical amplification. The other is a section of the optical fiber to pump the role of the active medium, the signal light is amplified. If only the cladding consists of an active medium, the signal light is amplified by its disappearing field interacting with the active medium, which is the disappearing field coupled fiber amplifier. In this paper, the theoretical analysis of such amplifiers, composed of multi-mode and single-mode fiber amplifier