Short multiwavelength fiber laser made of a large-band distributed Fabry-Pe/spl acute/rot structure

Multiwavelength fiber lasers are obtained by writing two superimposed chirped fiber Bragg gratings in a photosensitive Er/sup 3+/--Yb/sup 3+/ codoped optical fiber. The chirped gratings create a distributed Fabry-Pe/spl acute/rot structure in which the resonating fields of the different laser lines are spatially separated, thus, reducing cross-gain modulation. We demonstrate multiwavelength lasers emitting simultaneously over 8 and 16 lines spaced by 50 GHz. The active structure is very compact having a total active length of 8 cm. We discuss how the properties of the device are governed by the parameters of the chirped gratings giving high flexibility in the laser design.     

Dual-Wavelength DFB Fiber Laser Based on Unequalized Phase Shifts

A novel structure for dual-wavelength distributed feedback (DFB) fiber laser is proposed and experimentally demonstrated. This structure is based on a uniform fiber Bragg grating with two unequalized phase shifts, which markedly suppress the mode competition of the two lasing wavelengths; and then a 52-pm-spaced dual-wavelength DFB fiber laser operating at single-longitudinal-mode and single-polarization is achieved at room temperature. A simple method is also implemented to fabricate the phase shifts with high precision     

Time-resolved chirp evaluations of Gbit/s NRZ and gain-switched DFB laser pulses using narrowband Fabry-Perot spectrometer

A compact, easy-to-use, low-cost spectrometer for solving the chirped spectrum of DFB lasers is demonstrated using narrowband Fabry-Perot etalons with resolutions comparable to grating spectrometers. Time-resolved chirp measurements of Gbit/s NRZ and gain-switched DFB laser pulses are presented.<>     

Multiwavelength DFB laser array transmitters for ONTCreconfigurable optical network testbed

We discuss the design, fabrication, and performance of experimental multiwavelength laser array transmitters that have been used in the reconfigurable optical network testbed for the Optical Network Technology Consortium (ONTC). The experimental four-node multiwavelength network testbed is SONET/ATM compatible. It has employed multiwavelength DFB laser arrays with 4 nm wavelength spacing for the first time. The testbed has demonstrated that multiwavelength DFB laser arrays are indeed practical and reproducible. For the DFB laser arrays used in such a network the precise wavelength spacing in the array and the absolute wavelength control are the most challenging tasks. We have obtained wavelength accuracy better than ±0.35 nm for all lasers, with some registered to better than ±0.2 nm. We have also studied the array yield of our devices and used wavelength redundancy to improve the array yield. Coupling efficiencies between -2.1 to -4.5 dB for each wavelength channel have been obtained. It is achieved by using specially designed lensed fiber arrays placed on a silicon V-grooved substrate to exactly match the laser spacing. The transmitter consisted of a multichip module containing a DFB laser array, an eight-channel driver array based on GaAs IC's, and associated RF circuitry     

Detuning adjustable multiwavelength MQW-DFB laser array grown byeffective index/quantum energy control selective area MOVPE

A multiwavelength MQW DFB laser array with novel structure Is described. Oscillation wavelength and gain peak wavelength were simultaneously controlled on the same epitaxial wafer by using modulated grown thicknesses of selectively grown InGaAs/InGaAsP/InP MQW active waveguides. The laser array with constant-pitch built-in corrugation fabricated by a simple DFB laser process demonstrated 10.1 nm controllable range for lasing wavelength and 45 nm for gain peak wavelengths, with uniform lasing properties and narrow spectral linewidths. The technique is attractive for light sources used in WDM/FDM applications     

Photonics True-Time-Delay Unit for Phased-Array Antenna Using Multiwavelength Fiber Laser Based on a Sagnac Interferemetric Filter

A photonics true-time-delay system for phased array beamforming using a chirped grating-based time-delay element and a novel multiwavelength erbium-doped fiber ring laser source employing a Sagnac filtering mirror is proposed. The Sagnac filtering mirror consists of a polarization maintaining directional coupler and two pieces of polarization maintaining fibers. The lasing wavelength and number are determined by properly adjusting the polarization controller within the unidirectional ring cavity and are very stable. A chirped-grating-based true-time-delay system using the proposed laser source is constructed and demonstrated experimentally.     

Compact high frequency true-time-delay beamformer using bidirectional reflectance of the fiber gratings

A compact high frequency true time delay (TTD) beamformer using bidirectional reflectance of the fiber gratings (FGs) is proposed. The FGs can be a set of fiber Bragg gratings (FBGs) or chirped fiber gratings (CFGs). The number and the length of the time delay lines are greatly reduced compared to the previous systems. A phase array antennas system using this TTD beamformer has many advantages including being compact, low requirement on the bandwidth of the tunable laser source and working at high microwave frequency. The proof-of-concept experiment results demonstrated the feasibility of the proposed scheme.     

Multiwavelength erbium-doped fiber ring laser incorporating an SOA-based phase Modulator

A novel room-temperature multiwavelength erbium-doped fiber (EDF) laser is demonstrated. Stable multiwavelength lasing at room temperature is realized by incorporating a semiconductor optical amplifier (SOA)-based phase modulator in the laser cavity. The SOA is biased below the transparent point with a sinusoidal signal applied to achieve phase modulation, to suppress the homogenous line broadening of the EDF. Stable multiwavelength lasing with wavelengths up to 26 and wavelength spacing as small as 0.19 nm is demonstrated at room temperature.     

Bidirectional 10-GHz optical comb generation with an intracavityfiber DFB pumped Brillouin/erbium fiber laser

We present multiwavelength and bidirectional operation of a novel Brillouin/erbium fiber ring laser. Multiwavelength operation is seeded by an Er³⁺:Yb³⁺ fiber distributed-feedback (DFB) laser inserted into the ring cavity. We realized lasing at up to eight wavelengths separated by 10.6 GHz     

Longitudinal mode competition in chirped grating distributedfeedback lasers

Gain competition often inhibits the simultaneous lasing of multiple longitudinal modes in homogeneously broadened laser systems. A stability analysis is developed to demonstrate that the two lowest order degenerate longitudinal modes in an index-coupled distributed feedback (DFB) laser will lase simultaneously when the index grating is chirped asymmetrically along the axis of the device. This chirped grating structure is shown to decrease the gain competition by reducing the spatial overlap between the degenerate modes. Stable mode beating between the two lowest order lasing modes results, and this beating produces high-frequency output self-pulsations which can be used for millimeter-wave and soliton pulse train generation. An exact closed-form expression for the output intensity of an antisymmetrically chirped index-coupled DFB laser, as a function of the unsaturated gain, is also derived. The expression is valid for arbitrary levels of gain saturation     

Tunable dual-mode operation in a chirped gratingdistributed-feedback laser

We report on the tunable dual-mode operation of a chirped grating distributed-feedback (DFB) laser device with two integrated modulators which act as tuning sections. A transfer-matrix model is used to simulate the amplified spontaneous emission spectrum for a chirped grating DFB laser. Several types of dual-mode operation are observed for wavelength spacings of 0.5 nm and 1.4 nm corresponding to frequency detunings of 63 GHz and 175 GHz     

Simple and Accurate Optical Frequency Domain Ranging Using Off-the-Shelf DFB Lasers Subject to Frequency-Shifted Optical Feedback

It is demonstrated that accurate distance measurement may be effected using a commercially available distributed feedback (DFB) semiconductor laser subject to frequency-shifted optical feedback. A simple experimental arrangement is employed wherein a chirped frequency comb is generated in an external cavity DFB laser using an intracavity acoustic-optic modulator. The frequency comb generates a beat frequency which is proportional to the path difference of a target and reference arm. An estimate of the accuracy and resolution of the measurement is given.     

Multiwavelength Fiber Optical Parametric Oscillator

We demonstrate, for the first time to the best of our knowledge, a multiwavelength fiber ring laser using a continuous-wave dual-pump fiber optical parametric amplifier (FOPA) as gain medium. In the ring cavity, two high-power pumps are injected into a spool of 1-km highly nonlinear dispersion-shifted fiber to generate the parametric gain, and a superimposed chirped fiber Bragg grating is used as the comb-like filter. Benefiting from the high and flat gain of the dual-pump FOPA, seven lasing lines around 1.55 mum with wavelength spacing of 1 nm have been obtained. Each lasing line has a linewidth of as narrow as 20 pm and an extinction ratio of > 30 dB. The proposed mechanism using a dual-pump FOPA as gain medium is a promising alternative for generating multiwavelength laser.     

色散补偿法获得5GHz,6.8ps超短光脉冲

利用色散位移光纤压缩从１．５５μｍ增益调制ＤＦＢ激光器中出射的红移啁啾光脉冲。在最优光纤压缩长度下，光脉冲宽度由４２．６ｐｓ压缩至６．８ｐｓ，压缩比为６．３     

低掺杂铒纤上分布反馈布拉格光纤激光器的制作

采用准分子激光器成功地在低掺杂普通铒纤上制作出5 cm的光纤光栅分布反馈布拉格(DFB)激光器,铒纤的峰值吸收率为5 dB/m,在100 mW,980 nm抽运光条件下,光纤激光器的输出功率为50μW,边模抑制比为50 dB。使用耦合模理论分析了一段5 cm带相移的分布反馈布拉格光纤激光器输出光强同腔内损耗及相移量的关系,计算结果表明,光纤腔内的损耗对激光器的输出具有非常重要的影响,大的损耗对应获得最大功率的光栅耦合强度相应减小,因此,在低掺杂铒纤上制作分布反馈布拉格激光器必须正确估计光纤激光器的腔内损耗,选择合适的光栅耦合强度,可以获得较大的输出功率。     

基于啁啾光纤光栅的五波长掺铒光纤激光器

提出并实验验证了一种新型的基于啁啾光纤光栅的全光纤的可切换的五波长掺铒光纤激光器,该激光器采用简洁的线性腔结构,使用一段高掺铒的光纤作为增益介质,利用一个内含宽带啁啾光纤光栅的萨格纳克环作为激光器的谐振腔腔镜,担当了一个梳状滤波器的作用,另一个腔镜由一个宽带光纤反射镜担当,适当调整环中的偏振控制器,可以获得最多五波长的激光输出,并具有4种不同的激光输出模式,所有激发线均具有大于32 dB的光学信噪比,小于0.6 nm的线宽以及小于8 dB的峰值功率差异。     

Modeling and experimental demonstration of ultracompact multiwavelength distributed Fabry-Pe/spl acute/rot fiber lasers

This work presents a complete model for the design and optimization of multiwavelength distributed Fabry-Pe/spl acute/rot (DFP) fiber lasers that are made by superimposing two chirped fiber Bragg gratings in a photosensitive codoped erbium-ytterbium (Er-Yb) fiber. The model is based on a matrix formulation of coupled-mode equations taking into account the chirped grating superstructure and including a spectrally resolved gain medium. The performed analysis reveals that the signal power of each channel is strongly localized near a minimum of the superstructured-grating envelope. As a consequence, the overlap between the power distributions in neighboring cavities is small, thus reducing the effect of cross-gain saturation and allowing a high number of channels in a short piece of fiber. The simulations also show how the saturation of the cross-relaxation mechanism between ytterbium and erbium leads to flat output spectra without the need for an additional equalization scheme such as a complex grating apodization profile. Furthermore, to validate the theoretical model, we present the experimental realization and characterization of a multiwavelength laser emitting in a single-mode and single-polarization over 16 wavelengths spaced by 50 GHz and with a total output power of 52 mW.     

Integrated Electro-Absorption Modulation DFB Laser Based Optical True Time-Delay Feeder for X-Band Phased Array Antennas

A 4-bit optical true-time-delay feeder incorporating an integrated electro-absorption modulation distributed feedback (DFB) laser for X-band phased array antennas is demonstrated. The integrated electro-absorption modulation DFB laser is an attractive device that provides a very compact, low-cost solution for optical true-time-delay systems. The variable delay line is constructed by cascaded magneto-optic switches, which have fast switching speed. The integrated electro-absorption modulation DFB laser system shows high signal-to-noise ratio up to 58dB, and the transmission performance of the system is relatively good and accredited.     

Single-longitudinal-mode multiwavelength fiber ring laser

A single-longitudinal-mode multiwavelength fiber ring laser is proposed and demonstrated. The single-longitudinal-mode operation is realized using a fiber loop mirror with a saturable absorber. The fiber loop mirror acts as a passive self-tracking narrow multiband optical filter. Single-longitudinal-mode multiwavelength lasing is generated by using either a Lyot-Sagnac filter or a fiber grating array.     

基于光纤DFB激光器的高分辨折射率传感器

分析一种基于腐蚀相移DFB激光器的高分辨率折射率传感器。外界折射率通过改变腐蚀DFB激光器的相移影响激光器的输出特性。通过详细分析相移和增益对激光输出特性的影响,获得了相移激光输出波长的关系。根据激光器基模和高阶模波长差对温度的自补偿特性,设计了高分辨率的折射率传感器。理论上获得了该传感方案在激光线宽为100 kHz时,折射率传感分辨率高达10-7数量级。