【正文】 loop mirror filter of twostage polarizationmaintaining fibers and polarization controllers for multiwavelength fiber ring laser,” Opt. Express 17, 10573–10583 (2009).15. M. A. Ummy, N. Madamopoulos, A. Joyo, M. Kouar, and R. Dorsinville, “Tunable multiwavelength SOA based linear cavity dualoutput port fiber laser using Lyot–Sagnac loop mirror,” Opt. Express 19, 3202–3211 (2011).16. A. Gonz225。lezGarc237。a, O. Pottiez, R. GrajalesCouti241。o, B. Ibarra Escamilla, and E. A. Kuzin, “Switchable and tuneable multisavelength Erdoped fibre ring laser using Sagnac filters,” Laser Phys. 20, 720–725 (2010).譯文二：可調(diào)諧全光纖雙折射梳狀濾波器Raymond ，ChangSeok Kim,Jin ,巴爾的摩，約翰霍普金斯大學(xué)電氣與計(jì)算機(jī)工程部門，MD 21218，Email：jkang@引言可調(diào)諧光梳狀濾波器已經(jīng)被證明可用于發(fā)展波分復(fù)用光學(xué)光纖通信系統(tǒng)中的多波長(zhǎng)激光器。這種濾波器實(shí)現(xiàn)方式是使用光纖光柵、高雙折射率光纖和法布里珀羅諧振器1 。在所有這些情況下，梳狀濾波器的信道間隔是固定的，而對(duì)于布拉格光纖來(lái)說(shuō)，光譜調(diào)諧是有限的。本文我們將實(shí)驗(yàn)證明低插入損耗、大消光比和偏振不敏感的可調(diào)頻道間隔梳狀濾波器。這種濾波器可以很容易應(yīng)用于多波長(zhǎng)光纖激光器結(jié)構(gòu)中?；菊{(diào)諧概念一個(gè)基本的Lyot光纖濾波器通過(guò)把一個(gè)高雙折射光纖（PM光纖）放置在兩個(gè)偏振裝置之間，并且快軸相對(duì)于偏振鏡的軸旋轉(zhuǎn)45176。構(gòu)成2 。PM光纖兩個(gè)軸的波長(zhǎng)相關(guān)相位差產(chǎn)生了一個(gè)正弦曲線的波長(zhǎng)相關(guān)濾波傳輸函數(shù)，如方程式1所示，其中是光纖雙折射，是光纖長(zhǎng)度。如方程式2所示，波長(zhǎng)間隔取決于傳輸峰的相鄰距離。 （1） （2）波長(zhǎng)間隔可以通過(guò)改變PM光纖長(zhǎng)度進(jìn)行調(diào)諧，但這種方法不適合動(dòng)態(tài)波長(zhǎng)間隔調(diào)諧。在近期工作中，我們證明了有效的一種方法即通過(guò)使用兩段PM光纖的Lyot濾波器實(shí)現(xiàn)光纖長(zhǎng)度的離散變化3 。這個(gè)結(jié)構(gòu)中，光纖分段放置在兩個(gè)偏振器件之間并且每段都可以獨(dú)立旋轉(zhuǎn)。旋轉(zhuǎn)每段光纖可以改變有效長(zhǎng)度，比如快軸相對(duì)于慢軸為 +45176。或 45176。增加光纖分段數(shù)量隨之可以增加合適波長(zhǎng)間隔的數(shù)量。2段、3段、4段的波長(zhǎng)間隔數(shù)量分別為140。這里我們的工作是把一個(gè)兩段Lyot濾波器擴(kuò)展成一個(gè)三段Lyot濾波器和三、四段SagnacLyot濾波器。這個(gè)工作展現(xiàn)了多段雙折射濾波器獨(dú)特的濾波特性。濾波器透射譜測(cè)量光纖型梳狀濾波器可以通過(guò)兩種方式實(shí)現(xiàn)：1）使用光纖偏振器件的標(biāo)準(zhǔn)Lyot雙折射濾波器；2）使用帶有一個(gè)50：50耦合器的Sagnac干涉儀裝置的SagnacLyot濾波器。圖1a3a顯示了兩種結(jié)構(gòu)的實(shí)驗(yàn)裝置。在PM光纖片段的兩邊都使用光纖半波片，從而有效控制偏振態(tài)。SagnacLyot濾波器只有兩個(gè)有效的旋轉(zhuǎn)角度： +45176。和 45176。另外，二元SagnacLyot梳狀濾波器的有效長(zhǎng)度為和。通常n元SagnacLyot梳狀濾波器有效長(zhǎng)度的數(shù)量為。如圖3a所示，176?？梢援a(chǎn)生一個(gè)的一階濾波器。濾波器片段使用Newport公司PM光纖，折射率為。實(shí)驗(yàn)中搭建了兩個(gè)獨(dú)立的濾波器：1）一個(gè)由=，=，=。這種濾波器應(yīng)用于Lyot和SagnacLyot結(jié)構(gòu)中。由=，=，=，=。使用一個(gè)相干光源（Calmar公司飛秒激光器）和一個(gè)摻鉺光纖放大器中的ASE作光源，Lyot和Sagnac濾波器的傳輸光譜可以用光學(xué)頻譜分析儀測(cè)量。圖1b，2b和3b顯示了三種濾波器測(cè)量的傳輸光譜。旋轉(zhuǎn)光纖片段各邊上的半波片可以得到不同的波長(zhǎng)間隔。各濾波器波長(zhǎng)間隔的數(shù)量為12，和理論值都一致。典型的插入損耗為4dB。插入損耗主要是由于偏振控制器中光纖環(huán)半徑小，產(chǎn)生了明顯的彎曲損耗，并且保偏和非保偏光纖的接合也會(huì)產(chǎn)生損耗。內(nèi)在損耗可以通過(guò)弄直偏振控制光纖測(cè)量。部分損耗來(lái)自于保偏與非保偏焊接。消光比的數(shù)值從16dB到12dB不等。濾波器響應(yīng)間隔非常平坦（）和一致。圖1 Lyot濾波器結(jié)構(gòu)圖2 SagnacLyot濾波器圖3 二階SagnacLyot濾波器結(jié)論我們證明了一個(gè)新的頻道間隔可調(diào)諧的全光纖梳狀濾波器。這種濾波器可以用于一個(gè)在多波長(zhǎng)激光器中，并且為激光器設(shè)計(jì)了提供極高的靈活性。我們同時(shí)證明了Lyot濾波器和SagnacLyot濾波器。其中Lyot濾波器只需要少量光纖片段就能提供大量波長(zhǎng)間隔數(shù)量。（例如四段濾波器提供40個(gè)波長(zhǎng)間隔）另外，SagnacLyot濾波器的可調(diào)諧功能獨(dú)立于輸入偏振態(tài)。測(cè)量的插入損耗的典型值為4dB，消光比為15dB。使用低損耗偏振控制器和改善保偏與非保偏光纖的熔接技術(shù)可以降低插入損耗值。參考文獻(xiàn)1. N. Park, . Dawson, and ,“MultipleWavelength Operation of an ErbiumDoped Fiber Laser,” IEEE Photon. Tech. Lett.,1992, 4, 540–541。 S. Li and . Chan, “Anovel configuration for multiwavelength activelymodelocked fiber lasers using cascadedfibre Bragg gratings”, IEEE . Lett., 1999, 11, 179–181.2. X. Fang,H. Ji, , , and , “A Compound HighOrder PolarizationIndependent Birefringence Filter Using Sagnac Interferometers,” IEEE Photon. , 458–460 (1997)。 Y. Yen and R. Urlich,“Birefringent optical filters in singlemodefiber,” Opt. Lett. 6, 278–280 (1981).3. . Sova, . Kim and . Kang, “DualwavelengthallPM Er/Yb fiber ring laser withwavelength and channel separation tunability”Laser and ElectroOptics, 2001 CLEO2001, CWA52, May 6–11, 2001 Baltimore,MD.外文原文二：Tunable AllFiber BirefringenceComb FiltersRaymond M. Sova, ChangSeok Kim, andJin U. Kang, Department of Electrical andComputer Engineering, Johns Hopkins University,Baltimore, MD 21218, Email: jkang@Tunable optical b filters have been demonstrated to be useful in the development of multiwavelength laser sources for wavelength division multiplexing (WDM) optical fiber munication systems. Such filters have been implemented using fiber Bragg gratings, highbirefringence fibers and FabryPerot In all these cases, the channel spacing of the b filter function is fixed and in the case of the fiber Bragg grating, the spectral extent is limited. In this paper we experimentally demonstrate a tunable b filter with adjustable channel spacing with low insertion loss, large extinction ratio and can be made polarization insensitive. This filter can easily be implemented into a fiber laser configuration for multiwavelength operation. Tuning ConceptA basic Lyot fiber filter can be constructed by placing a highbirefringence fiber (PM fiber) between two polarizers with the fastaxis of the fiber rotated 45 degrees relative to the polarizer The wavelength dependent phase difference between the two axes of the PM fiber produces a sinusoidal wavelength dependent filter transmission function as given by Equation 1, where is the fiber birefringence and is the length of the fiber. The wavelength spacing is determined by the separation of the transmission peaks as given by Equation 2. （1） （2）The wavelength spacing can be tuned by changing the length of the PM fiber but is not practical for the dynamic wavelength space tuning. In recent work, we have demonstrated a method to effectively change the fiber length in discrete steps by using a Lyot filter based on twosegments of PM In this configuration, the fiber segments are placed between two polarizers and each segment is rotated independently. The effective length is changed by rotating each segment such that the fast axis is either +45, 0, or –45 degrees relative to the polarizer axis. The number of possible wavelength spacings increases with increasing number of fiber segments. The number of wavelength spacings for a 2segment, 3segment and 4segment Lyot filter is 4, 13, and 40, respectively. Here we extend this work from a twosegment Lyot filter to a threesegment Lyot filter and three and foursegment SagnacLyot filters. This work demonstrates the unique filtering properties of multisegment