Analysis of steady-state cascaded stimulated Brillouin scatteringin a fiber Fabry-Perot resonator

We investigate the steady-state properties of cascaded stimulated Brillouin scattering (CSBS) in a fiber Fabry-Perot resonator with reflection mirrors by numerically solving the coupled-power equations under the boundary conditions at the two mirrors. The dependence of CSBS on the input power is calculated for the symmetric and asymmetric fiber resonators. The threshold powers for the first- and second-order Stokes waves are calculated as a function of the mirror reflectance for the symmetric resonator     

A self-seeded tunable multiwavelength erbium-doped fiber ring laser with fiber bending scheme

A new tunable multiwavelength fiber laser is proposed. Such a laser contains a homogeneous and inhomogeneous broadening media, i.e., a Fabry–Perót laser diode and an erbium-doped fiber amplifier, in the laser cavity. The Fabry–Perót laser diode is used to obtain tunable multiwavelength lasing. By adjusting the injection current of the Fabry–Perót laser diode, emission at a single wavelength, dual wavelengths, triple wavelengths or quadruple wavelengths are obtained. The lasing wavelength is tuned by bending a section of fiber in the laser cavity. The tuning ranges for single wavelength lasing and dual wavelength lasing are 20 nm and 10 nm, respectively, while those for triple wavelength lasing and quadruple wavelength lasing are 7 nm and 3 nm, respectively.     

Widely tunable wavelength spacing dual-wavelength single longitudinal mode erbium doped fiber laser

A simple widely tunable wavelength spacing dual-wavelength single longitudinal mode (SLM) erbium doped fiber laser (EDFL) based on cascaded fiber Bragg gratings (FBGs) and birefringent fiber filter is proposed and demonstrated. Experimental results show that the lasing wavelength spacing is widely tunable in a range from 2 nm to 18 nm, which has potential to generate frequency tunable terahertz (THz) waves by beating the lasing dual-wavelength in a high speed photodetector. The birefringent fiber filter acts as an ultra-narrow bandpass filter and benefits the simultaneous oscillation of dual-wavelength in a single laser cavity. The output peak power of the lasing dual-wavelength is approximately equalized at room temperature, and a high optical signal-to-noise ratio (OSNR) is realized in the whole tuning range. The SLM operation of dual-wavelength fiber laser is verified by Fabry–Perot (F–P) scanning interferometer, and the clear eye diagram proves that the proposed fiber laser is effective in the application of fiber optic communication system.     

Tunable dual-wavelength-switching fiber grating laser

We report a tunable dual-wavelength-switching fiber grating laser by exploiting the large homogeneous gain broadening in erbium (Er)-doped fiber to suppress simultaneous lasing. Wavelength switching was accomplished through a novel design which has two overlapping cavities sharing a single-gain medium. The loss corresponding to one of the lasing wavelengths can be modulated via an optical chopper. Output power of about 6 mW and extinction ratio up to 50 dB were observed. The lasing wavelengths were tunable and switching was demonstrated for wavelength separations ranging from 0.35 to 23.5 nm     

用可调谐法布里-珀罗腔测量光纤光栅波长

提出了一种利用压电陶瓷构成的可调谐法布里 -珀罗腔测量光纤光栅反射波长的方案 ,该方案可以直接将波长转换为电信号。阐述了该方案的基本原理 ,并讨论了在设计法布里 -珀罗腔时应考虑的几个问题。     

基于拉锥光纤优化的光纤环镜滤波器特性研究

为了将拉锥光纤的光学特性和光纤环镜的滤波特性相结合,提出了一种用拉锥光纤优化的光纤环镜滤波器结构.实验研究发现,在级联的2阶高双折射光纤环镜滤波器中接入拉锥光纤,滤波器输出谱的主峰3dB带宽得到显著压缩,品质因数进一步提高,其Q值很容易达到5.2,滤波器在10dB~35dB调制深度范围内调谐更灵活,输出波形更加稳定.结果表明,该结构改善了高双折射光纤环镜滤波器特性,使调谐更为灵活.     

Analysis of Cavity‐Mode Lasing Characteristics from a Resonator with Broadband Cholesteric Liquid‐Crystal Bragg Reflectors

Detailed optical lasing characteristics in liquid crystal (LC) microlasers consisting of multiple polymer cholesteric LC (PCLC) layers are presented as broadband resonators sandwiching a layer of thick gain media, dye‐containing nematic LC (NLC) or isotropic liquid, in between. Multiple lasing emission peaks due to Fabry‐Perot cavity modes are observed for both gain media, and their polarization characteristics investigated. To analyze lasing characteristics, specified eigen modes are defined, the polarization states of which are maintained before and after passing through the broadband resonator, and obtained for the present full system by using the Berreman 4 × 4 matrix method. Using these specified eigen modes, the optical density for each mode is calculated and compared with the experimental results, and shows good agreement. Finally, lasing characteristics between the resonators with NLC and isotropic gain media are compared, and the advantages of adopting dye‐doped NLC gain medium are shown for tunable red, green, blue lasing in a microlaser system with a broadband resonator.     

光纤光栅法布里-珀罗腔的单模特性研究

分析了基于方向耦合器的光纤光栅法布里－珀罗腔的单模输出条件;在此条件下讨论了谐振腔的完全单模输出特性,并分析了其调谐特性。     

Tunable dual-wavelength fiber laser

A narrow-linewidth, tunable, dual-wavelength fiber laser operating at room temperature with each lasing wavelength in single-longitudinal-mode operation is demonstrated. A commercially available tunable fiber Bragg grating was used to tune one of the lasing lines. An unpumped elliptical-core erbium-doped fiber was used as a saturable absorber to suppress mode hopping. Wavelength switching was achieved using a polarization controller. The linewidth (FWHM, full width at half maximum) of the laser line was 6.7 MHz and the OSNR (optical signal to noise ratio) was more than 40 dB.     

Design of widely tunable semiconductor lasers and the concept ofbinary superimposed gratings (BSG's)

We propose a new concept of binary superimposed gratings (BSG's) as multiwavelength grating reflectors and show it as an effective structural improvement over the existing designs, to both the fabrication process and device performance. We also present a study of key design issues for widely tunable lasers based on grating mirrors with a comb-like reflection spectrum and summarize simple design rules for the grating part of the laser, based on analytical and numerical analysis. The binary supergrating consists of elements of equal size whose refractive index is allowed to be one of two possible values, which are sequenced according to a binary optics formalism to effect a spatial superposition of multiple sets of single-frequency gratings, and its implementation is well within the standard e-beam lithography limits. The calculations of lasing frequency, mode, and side-mode suppression ratio of the tunable laser are formulated and presented along with numerical examples     

Multiwavelength Raman fiber-ring laser based on tunable cascaded long-period fiber gratings

Multiwavelength Raman fiber lasers using intracavity tunable cascaded long-period fiber gratings (LPFGs) are discussed. The application of the cascaded LPFGs as a multichannel fiber filter for the multiple-wavelength generation is proposed and experimentally demonstrated. The characteristics of multiwavelength fiber-ring lasers can be controlled by changing the physical parameters of cascaded LPFGs such as the separation distance between the gratings, grating length, and number of gratings. The multiwavelength Raman fiber-ring laser with nine wavelength-division-multiplexing channels with 100-GHz spacing and 19 channels with 50-GHz spacing has been achieved by varying the physical parameters of cascaded LPFGs.     

L-band tunable erbium doped fiber ring laser using fiber loop mirror filters

We present a novel and efficient L-band wavelength-tunable Er^3＋ doped fiber laser of ring structure. In the cavity two segments of Er^3＋ doped fiber and a fiber Bragg grating are used to improve pump efficiency. Tunable filters based on fiber loop mirrors are also applied inside the cavity to act as both a wavelength selector and a line-width compressor. Using these techniques, a tunable laser with tuning range up to 42 nm, output power larger than 1 mW, power uniformity controlled within 1.75 dB and side mode suppression ratio about 40 dB is achieved.     

光纤光栅在高功率连续光纤激光器中的发展及展望

目前光纤光栅在高功率连续光纤激光器中的应用主要有两个方面,一是作为谐振腔腔镜,二是用来抑制激光器的非线性效应。首先论述了光纤光栅作为腔镜技术的发展现状,然后着重论述了能够抑制光纤激光器中非线性效应的特殊光纤光栅的发展状况。并详细描述了倾斜布拉格光纤光栅抑制受激拉曼散射和受激布里渊散射、长周期光纤光栅抑制受激拉曼散射以及相移长周期光纤光栅抑制自相位调制或四波混频等非线性效应引起的光谱展宽的研究进展。最后展望了光纤光栅在高功率光纤激光器领域的发展趋势,认为光纤光栅将朝着更高承载功率与长波长方向发展,同时认为基于飞秒激光刻写的光纤光栅技术、能够同时抑制多种非线性效应的光纤光栅技术、以及基于光纤光栅的光纤激光器激光偏振控制技术等将成为新的研究热点。     

Wavelength-switched optical pulse generation in a fiber ring laserwith a Fabry-Perot semiconductor modulator and a sampled fiber Bragggrating

A simple mode-locked fiber ring laser for generating wavelength-switched picosecond pulses was developed in which a laser diode played the role of both an intensity modulator and a tunable filter. A serially cascaded sampled fiber Bragg grating predefined the set of four allowable output wavelengths spaced 1.6 nm apart. Wavelength switching between the longest and shortest wavelengths required only a temperature change of the laser diode by 7.63°C     

All-optical wavelength conversions based on MgO-doped LiNbO/sub 3/ QPM waveguides using an EDFA as a pump source

We propose and demonstrate cascaded /spl chi//sup (2)/ wavelength conversion in an MgO-doped LiNbO/sub 3/ quasi-phase-matched waveguide at reduced pump cost by using only an erbium-doped fiber amplifier (EDFA) as the exclusive pump source in a fiber-ring resonator. A fiber Bragg grating in conjunction with an optical circulator isolates the pump light and confines it to the resonator. A conversion efficiency of -30 dB was obtained with a 3-dB gain-saturation output power of only +12 dBm from the EDFA. It is anticipated that -14-dB conversion efficiency is possible, if an EDFA with a 3-dB gain-saturation output power of +20 dBm is used.     

Stable single-mode compound-ring erbium-doped fiber laser

In this paper we report the fabrication of a robust, tunable single-longitudinal-mode compound-ring Er³⁺-doped fiber laser. The laser is fundamentally structured on an all-fiber compound-ring resonator in which a dual-coupler fiber ring is inserted into the main cavity. When combined in tandem with a mode-restricting intracavity tunable bandpass filter, the compound-ring resonator ensures single-longitudinal-mode laser oscillation. The laser can provide up to 20 mW output power over much of its 1525 to 1570 nm wavelength tuning range. The short-term linewidth of the laser output measured is less than 5 kHz. The laser frequency is actively stabilized for a long time by exploiting the inherent filter nature of the compound-ring resonator. The reduction of an associated frequency modulation is also discussed in detail     

Tunable fiber laser based on a cascaded structure consisting of in-line MZI and traditional MZI

A tunable erbium-doped fiber (EDF) laser with a cascaded structure consisting of in-line Mach-Zehnder interferometer (MZI) and traditional MZI is proposed. The transmission spectrum of the in-line MZI is modulated by the traditional MZI, which determines the period of the cascaded structure, while the in-line MZI’s transmission spectrum is the outer envelope curve of the cascaded structure’s transmission spectrum. A stable single-wavelength lasing operation is obtained at 1 527.14 nm. The linewidth is less than 0.07 nm with a side-mode suppression ratio (SMSR) over 48 dB. Fixing the in-line MZI structure on a furnace, when the temperature changes from 30 °C to 230 °C, the central wavelength can be tuned within the range of 12.4 nm.     

基于可调谐法珀腔解调的光纤法珀应变传感系统

本文提出了一种基于可调谐法珀腔解调的光纤法珀应变传感器系统，阐述了该系统的测量原理，提出了可调谐法珀腔的一种设计方案。     

Studies on strain and temperature characteristics of a slanted multimode fiber Bragg grating and its application in multiwavelength fiber Raman ring laser

Detailed strain and temperature characteristics of a 2/spl deg/ slanted multimode fiber Bragg grating (MFBG) are developed theoretically and observed experimentally. Results show that the strain and temperature sensitivities are almost the same for different transmission dips of the 2/spl deg/ slanted MFBG. Utilizing two characteristics of the 2/spl deg/ slanted MFBG, namely 1) resonant wavelength intensities strongly affected by excited mode propagating before the grating and 2) uniform strain sensitivities of different resonant wavelengths, a switchable and tunable multiwavelength fiber Raman ring laser is realized. The configuration is simple and multipurpose. Results show that the laser can generate single-, dual-, three-, four-, and five-wavelength lasing by switching between each operation if a mode scrambler (MS) that is inserted in front of the slanted MFBG is adjusted; furthermore, a 4.2-nm continuous wavelength-tuning range is achieved by straining the slanted MFBG when the MS is fixed.     

Simultaneous dual-wavelength operation in cascaded stronglygain-coupled DFB lasers

Using cascaded strongly gain-coupled (SGC) DFB lasers, simultaneous dual-wavelength operation can be obtained with better than a 40-dB side-mode suppression ratio (SMSR) under simple operating conditions at various temperatures. Dual-wavelength operation with various spacing can be achieved by grating fabrication and by simply activating the lasing section of the cascaded SGC DFB lasers. The lasing wavelengths can be tuned within several nanometers by base temperature variation and their spacing can be fine tuned by individual injection current