Segmented-clad fiber design for inherently gain-flattened L/sup +/-band TDFA

We present here an efficient design for high gain, inherently gain-flattened L/sup +/-band thulium-doped fluoride fiber amplifier (TDFA), based on a novel segmented clad fiber refractive index profile. Detailed simulations show that the designed amplifier is able to achieve 20-dB gain, with /spl plusmn/0.7-dB gain ripple over 40-nm bandwidth (1600-1640) nm. Performance comparisons of the proposed module with an L/sup +/-TDFA based on conventional W-fiber designs and on a conventional step-index fiber have also been carried out.     

S-band single-stage EDFA with 25-dB gain using distributed ASE suppression

We propose a novel compact design for a single-stage S-band erbium-doped fiber amplifier, wherein distributed suppression of C-band amplified spontaneous emission is provided by optimized bend loss in a coaxial core fiber. Simulations show that /spl sim/25-dB unsaturated gain over 30-nm bandwidth (1495-1525) nm is achievable with the designed module, using a nominal pump power of 500 mW. The noise figure of the amplifier varies between 4.5 and 8 dB from 1495 to 1525 nm. By proper designing, we have also ensured that the gain ripple over the entire 30-nm bandwidth is 相似文献   

A low-noise and gain-flattened amplifier composed of a silica-based and a fluoride-based Er/sup 3+/-doped fiber amplifier in a cascade configuration

We propose a novel low noise and gain-flattened Er/sup 3+/-doped fiber amplifier (EDFA) with a cascade configuration for wavelength division multiplexing (WDM) signals. In this configuration, a 1480-nm pumped fluoride-based EDFA is joined to a 980-nm pumped silica-based EDFA through an optical isolator. By adjusting the silica-based Er/sup 3+/-doped fiber length in the silica-based EDFA, we realized an excellent flat gain EDFA with a gain excursion of less than 0.9 dB and noise figure of 5.7/spl plusmn/0.2 dB, and a low noise EDFA with a noise figure of 5/spl plusmn/0.2 dB and a gain excursion of less than 1.4 dB, for 8 channel WDM signal in the 1532-1560-nm wavelength region.     

A novel design for dispersion compensating photonic crystal fiber Raman amplifier

This letter presents a novel design for dispersion compensating photonic crystal fiber (DCPCF) which shows inherently flattened high Raman gain of 19 dB (/spl plusmn/1.2-dB gain ripple) over 30-nm bandwidth. The proposed design module has been simulated through an efficient full-vectorial finite element method. The designed DCPCF has a high negative dispersion coefficient (-200 to -250 ps/nm/km) over C-band wavelength (1530-1568 nm). The proposed fiber module of 5.2-km length not only compensates the accumulated dispersion in conventional single-mode fiber (SMF-28) but also compensates for the dispersion slope. Hence, the designed DCPCF module acts as the gain-flattened Raman amplifier and dispersion compensator.     

Novel fiber design for flat gain Raman amplification using single pump and dispersion compensation in S band

This paper reports on a novel fiber design that has an inherently flattened effective Raman gain spectrum. Simulations show that gain-flattened broad-band Raman amplification, using a single pump, can be achieved in any wavelength band by suitably choosing the fiber parameters and the pump wavelength. The fiber also has a high negative dispersion coefficient-(380-515) ps/km/spl middot/nm over the operating range of wavelengths-and the shape of the dispersion curve is such that the total link dispersion can be not only compensated but also flattened. Hence, the designed fiber can serve as a lossless, broad-band, dispersion-flattening, and dispersion-compensating module for the S band, wherein lossless operation is achieved using inherently gain-flattened single-pump Raman amplification. The performance characteristics of such a module was modeled taking into account wavelength-dependent splice loss as well as background loss, and it has been shown through simulations that lossless operation with /spl plusmn/0.2-dB gain ripple is achievable over (1480-1511) nm using a single pump. Moreover, dispersion compensation for five spans of transmission in a 10-Gb/s system, over this 32-nm bandwidth in the S band, should be attainable using the proposed design.     

Fiber design for broad-band gain-flattened Raman fiber amplifier

We report here a novel fiber design which has inherently flattened effective Raman gain spectrum, with a relative 3-dB bandwidth of /spl sim/90 nm. Gain-flattened broad-band amplification can be achieved in any wavelength band by suitably choosing the fiber parameters and the pump wavelength. Simulations show that the proposed fiber also has high negative dispersion coefficient /spl sim/(-300 to -600) ps/km /spl middot/ nm in the operating range of wavelength. Hence, the designed fiber serves the purpose of a gain-flattened broad-band amplifier and dispersion compensator.     

Gain-flattened Er/sup 3+/-doped fiber amplifier for a WDM signal in the 1.57-1.60-/spl mu/m wavelength region

A gain-flattened Er/sup 3+/-doped silica-based fiber amplifier (EDFA) has been constructed for a 1.58-/spl mu/m band WDM signal. This EDFA exhibits uniform amplification characteristics with a gain excursion of 0.9 dB for a four-channel WDM signal in the 1.57-1.60 /spl mu/m wavelength region. The average signal gain and the noise figure for the WDM signal are 29.5 dB and less than 6.3 dB, respectively. The use of this EDFA in parallel with a 1.55-/spl mu/m band EDFA will expand the WDM transmission wavelength region.     

Very flat gain erbium-doped fiber amplifier using samarium-doped fiber

A two-stage erbium-doped fiber amplifier (EDFA) with extremely flat gain (/spl plusmn/0.1 dB) over 17-nm bandwidth is demonstrated. The gain flatness is achieved by incorporating samarium-doped fiber in the mid section of the amplifier.     

High-gain coefficient long-wavelength-band erbium-doped fiberamplifier using 1530-nm band pump

A 1530-nm band has been studied as a pump wavelength for the long-wavelength-band erbium-doped fiber amplifier (L-band EDFA). The pump source is built using a tunable light source and cascaded conventional-band (C-band) EDFA. The L-band EDFA uses a forward pumping scheme. Within the 1530-nm band, the 1545-nm pump demonstrates 0.45-dB/mW gain coefficient, which is twice better than that of conventional 1480-nm pumped EDFA. The noise figure of the 1530-nm pump is at worst 6.36 dB, which is 0.75 dB higher than that of the 1480-nm pumped EDFA. Such high-gain coefficient indicates that the L-band EDFA consumes low power     

Inherent enhancement of gain flatness and achievement of broad gainbandwidth in erbium-doped silica fiber amplifiers

We report new methods to inherently increase the flatness and bandwidth of erbium-doped silica fiber amplifiers from three perspectives: fiber design, pump-signal WDM coupler optimization, and amplifier structure. First, to achieve inherent control of the gain spectrum, a new type of composite fiber structure with an Er-doped core and a Sm-doped cladding ring is proposed and experimentally demonstrated. Interaction of the optical field with the Sm-doped cladding to produce evanescent wave filtering is modeled, which provides an in-line control of gain fluctuation in the erbium-doped flier amplifier (EDFA) C band, 1530-1560 nm. Second, the effect of the spectral characteristics of WDM couplers over the L band of an EDFA is explored. A fused taper fiber coupler for a 1480-nm pump is optimized for signals in the wavelength range of 1570-1610 nm by measuring the small-signal gain, gain tilt, and noise figure in an L-band EDFA. Finally, a new all-fiber structure for a wide-band EDFA, where the L and C bands were coupled serially, is demonstrated with optimized pump-signal couplers. Further optimization of the new composite fiber structure and the transient effects in the serially coupled EDFAs are also discussed     

Actively gain-flattened erbium-doped fiber amplifier over 35 nm byusing all-fiber acoustooptic tunable filters

We demonstrate an actively gain-flattened erbium-doped fiber amplifier (EDFA) using an all-fiber gain-flattening filter with electronically controllable spectral profiles. A good gain flatness (<0.7 dB) over a broad wavelength span (>35 nm) is achieved for a wide range of operational gain levels as well as input signal and pump powers     

27-dB gain unidirectional 1300-nm polarization-insensitive multiplequantum well laser amplifier module

An unidirectional polarization-insensitive multiple quantum well laser amplifier module for the 1300-nm window with a record high gain of 27 dB and a 3-dB saturation output power of 13 dBm is demonstrated. The module gain has a 3-dB width exceeding 60 nm and shows a typical polarization sensitivity and gain ripple as low as 0.3 dB. To provide immunity for backscattered or reflected light, polarization independent optical isolators were inserted in the input and output coupling optics of the package. A practical optical amplifier module for the 1300-nm window is very desirable, because most of the presently installed fiber has its zero dispersion wavelength around 1310 mm, while much of the older fiber often only can be operated around this wavelength     

A temperature-insensitive erbium-doped fiber amplifier for terrestrial wavelength-division-multiplexing systems

We have evaluated a variation in the temperature dependence of an erbium-doped fiber gain spectrum by a pump wavelength in the 980-nm band for the first time. By optimizing both the pump wavelength in the 980-nm band and a temperature-sensitive gain flattening filter, the gain change of an erbium-doped fiber amplifier was successfully suppressed to 0.18 dB/sub pp/ in the temperature range between 0/spl deg/C and 65/spl deg/C and the wavelength range of 37.0 nm.     

Low-noise intelligent cladding-pumped L-band EDFA

We present results on a low-cost cladding-pumped L-band amplifier based on side pumping (GTWave) fiber technology and pumped by a single 980-nm multimode diode. We show that simultaneous noise reduction and transient suppression can be achieved by using gain clamping by a seed signal (/spl lambda/=1564 nm). In the gain-clamping regime, the amplifier exhibits 30-dB gain over 1570-1605-nm spectral band with noise figure below 7 dB. The noise figure can be further reduced to below 5 dB by utilizing a low power single-mode pump at 980 nm. The erbium-doped fiber amplifier is relatively insensitive to input signal variations with power excursions below 0.15 dB for a 10-dB channel add-drop.     

Optimization and fabrication of stitched long-period gratings for gain flattening of ultrawide-band EDFAs

We present the optimization and fabrication of the stitched long-period fiber gratings (SLPGs) for gain flattening of an ultrawide-band erbium-doped fiber amplifier (EDFA). With an improved genetic algorithm, the gain spectrum of a practical EDFA with bandwidth of 80 nm is flattened within /spl plusmn/0.69 dB by an optimized SLPG. Furthermore, the SLPG is designed specially for a point-by-point grating writing technique. A superior control of the fabrication procedure of the designed SLPG has been demonstrated in the experiment.     

Dispersion-Compensating Fiber Raman Amplifiers With Step, Parabolic, and Triangular Refractive Index Profiles

This paper presents a comprehensive analysis of the performance of a gain-flattened coaxial fiber Raman amplifier with respect to the refractive index profile. The variation of the dispersion coefficient and the end-end gain spectrum of the coaxial fiber Raman amplifier against the core structure as a function of the step, parabolic, and triangular profiles are analyzed. The analysis shows that the dispersion coefficient is sensitive to the variation of the core structure of the fiber, whereas the effective Raman gain coefficient remains nearly constant as the structure changes. Simulations of transmissions employing the coaxial fiber Raman amplifier with the three different structures are carried out individually, and the results show that the parabolic and triangular profiles perform better than the step profile, where the parabolic profile gives the best performance over 80 km of G.652 fiber, with a transmission rate of 20 Gb/s and a gain ripple of plusmn1 dB. In addition, the analysis shows that the maximum negative dispersion wavelength of the fiber exhibits a linear relationship with the normalized core radius. Hence, a coaxial fiber Raman amplifier providing a possible operation over the L-band is proposed     

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.     

基于EDFA和级联RFA的混合光纤放大器的设计

基于EDFA的理论模型和受激拉曼散射效应的分析理论,利用EDFA和RFA的增益谱互补特性,对拉曼光纤放大器(RFA)采用两根光纤级联方式,研究并设计了EDFA与级联光纤的RFA相结合的混合放大器结构.仿真结果表明:在不使用增益均衡器的条件下,所设计的混合光纤放大器在输出端得到了近似相等的输出光功率,得到了增益平坦度为0.62 dB、波长带宽为70 nm(1 550～1 620 nm)的结果,在密集波分复用光通信系统中有重要的应用价值.     

Gain clamping in two-stage L-band EDFA using a broadband FBG

A gain-clamped long wavelength band erbium-doped fiber amplifier (L-band EDFA) with an improved gain characteristic is demonstrated by simply adding a broadband conventional band (C-band) fiber Bragg grating (FBG) in a two-stage amplifier system. The FBG reflects backward C-band amplified spontaneous emission (ASE) from the second stage back into the system to clamp the gain. The gain is clamped at about 22.4 dB with a gain variation below 0.4 dB for input signal powers of -40 to -15 dBm. Compared with an unclamped amplifier of similar noise figure values, the small signal gain has improved by 2.4 dB due to the FBG which blocks the backward propagating ASE. At wavelengths from 1570 to 1600 nm, gain of the clamped amplifier varies from 19.4 to 26.7 dB. The corresponding noise figure varies by /spl plusmn/0.35 dB around 5 dB, which is not much different compared to that of the unclamped amplifier.     

用增益钳制法观察烧孔效应

掺铒光纤放大器(EDFA)的烧孔效应(SHB)是导致放大器增益不平坦主要因素，进而影响长距离波分复用(wDM)光纤传输系统的性能。与此同时，对于EDFA的非均匀加宽作用的物理学研究并不成熟，所提出的几个理论模型也只是从经验和统计方面对SHB在一定程度上进行分析。为此，我们首次提出了利用放大器恒定增益控制来研究SHB的实验方法，分析了室温下1530～1564nm波长范围内SHB的深度、宽度与饱和信号波长的关系，以及SHB的深度与饱和信号功率的关系。