超短环形腔布里渊掺铒光纤激光器

提出了一种超短环形腔布里渊掺铒光纤激光器(BEFL),腔长仅为10m。该BEFL以4m长的普通掺铒光纤(EDF)为激光增益介质,腔外布里渊抽运光和980nm抽运光的注入在掺铒光纤中,分别引入非线性布里渊增益和线性掺铒光纤放大器(EDFA)增益。实验结果表明,BEFL工作在单纵模状态,输出信噪比高(>40dB),抽运阈值低(～20mW),输出功率大(>10mW),且布里渊抽运光不仅决定BEFL的输出波长,更对其抽运阈值和出光功率有重要影响。     

Stimulated Brillouin Scattering in a Single-Mode Tellurite Fiber for Amplification, Lasing, and Slow Light Generation

In this paper, Brillouin gain performances of tellurite fiber are investigated for photonics applications. We demonstrate stimulated Brillouin amplification and lasing and the simulated performance of slow light generation in a single-mode tellurite fiber. A Brillouin gain of 29 dB is achieved in a 100-m tellurite fiber with a pump power of 10 mW at 1550 nm. A peak value of Brillouin gain coefficients of 1.6989 X 10^-10 m/W is measured on the base of gain characteristics. An all-fiber Brillouin laser with the maximum unsaturated power of 54.6 mW at 1550 nm and a slope efficiency of 38.2% is achieved from a 200-m tellurite fiber by employing a ring cavity. Furthermore, widely tunable (~27 nm) Brillouin comb laser with 26 lines spaced at 7.97 GHz is obtained from the ring laser cavity including an erbium-doped fiber amplifier (EDFA). A simple theoretical model based on laser threshold theory successfully explains the properties of Brillouin comb lasers. Stimulated Brillouin scattering (SBS)-induced time delay per unit power and per unit length is also calculated using the measured data of Brillouin gain coefficients. A peak value of 0.09246 ns/mW/m and a time delay slope efficiency of 1.75 ns/dB are obtained for this tellurite fiber. Potential performance of a tellurite fiber for slow light generation is clarified on the base of Brillouin gain characteristic. Our results show that tellurite fiber is a promising gain medium for Brillouin fiber amplifiers, lasers, and slow light generation due to its low background loss and large Brillouin gain coefficient.     

Noise figure improvement in semiconductor optical amplifiers by holding beam at transparency scheme

We have studied the noise properties of a semiconductor optical amplifier (SOA) under the injection of a pump laser. The laser wavelength is set within the transparency region of SOA. The noise figure (NF) is found to decrease, strongly depending on the relative injection direction of signal and pump (i.e., copropagating or counterpropagating beams). In the copropagating scheme, an improvement in NF is obtained, ranging from 2.5 dB in the low current regime (40 mA, 13-dB chip gain) to 0.5 dB at high currents (150 mA, 23-dB chip gain). In the counterpropagating scheme, NF improvement is less pronounced. We explain the effect by an advantageous carrier redistribution along the SOA under the presence of the pump beam at transparency. A detailed simulation reproduces the observed results.     

基于受激布里渊散射的可调谐多波长激光器

可调谐多波长布里渊掺铒光纤激光器将光纤中的SBS非线性放大同掺铒光纤的线性放大相结合得到室温稳定的多波长输出,具有波长间隔一致、线宽窄、功率谱相对平坦等优点。设计了一种基于光纤布拉格(FBG)反射的线性可调谐多波长布里渊掺铒光纤激光器。该线性腔激光器的一端利用光纤布拉格光栅作为反射镜,有效抑制了腔内自激模的影响,增加激光器输出波长数。布里渊泵浦信号进入布里渊增益介质之前经过掺铒光纤放大器的两次放大,降低了布里渊增益的阈值。该多波长激光器实现了1 530～1 560 nm之间30 nm可调谐范围的输出。在布里渊泵浦信号功率2 mW,980 nm泵源抽运功率60 mW情况下,1 540～1 554 nm范围内,获得了波长间隔0.088 nm的16个波长的输出。     

Optical demodulation and amplification of FSK signals using AlGaAslasers

Stimulated Brillouin scattering is used as a narrowband amplifier to demodulate and amplify FSK signals at bit rates up to 250 Mbit/s. Gain of as much as a factor of 1000 is obtained for a pump over of 12 mW. Both pump and signal lasers are simple AlGaAs lasers     

Long span coherent transmission with erbium ytterbium doped fibre power amplifier over a 70 dB loss budget

A combination of a high power Er/Yb fibre optic amplifier and a coherent transmission system are used to achieve very large optical link loss budgets of 70 dB at 167 Mbit/s and 67 dB at 622 Mbit/s. A transmit power of +18.2 dBm was launched into low loss optical fibre without evidence of stimulated Brillouin scattering.<>     

宽带可调谐双频移多波长布里渊光纤激光器

提出了一种采用高非线性光纤作为布里渊增益介质 的双倍布里渊频移间隔的多波长布里渊光纤激光器(MW-BEFL)。激光器利用两个环形器构成 双倍频移结构,将奇数阶的斯托克斯信号隔离在腔内循环,仅有泵浦 信号和偶数阶的斯托克斯信号能够耦合输出,实现了双倍布里渊频移的多波长输出。激光器 腔内没有引入 任何的有源增益介质对斯托克斯信号进行放大,消除了腔内自激模的影响。激光器的调谐范 围由布里渊泵 浦的工作波长和掺铒光纤放大器(EDFA)的增益带宽决定。实验中,在布里渊 抽运 功率为0dBm、EDFA的输出功率为20 dBm的情况下,在1536~1605nm之间得到双频移间隔的多 波长输出,调谐范围是69nm。     

Vertical-cavity amplifying modulator at 1.3 μm

The modulation/switching properties of a vertical-cavity semiconductor optical amplifier operating at 1.3 μm wavelength are investigated. The device was optically pumped and operated in reflection mode. A 150-mV (100 mA) modulation of the drive to the pump source produced a 7-dB modulation of the pump power, which produced a 35-dB modulation in the output signal. The maximum extinction ratio was 35 dB, and limited by device heating. Frequency response measurements revealed a modulation bandwidth of 1.8 GHz when the amplifier was saturated. This enabled 2.5-Gb/s modulation of a -10 dBm input signal with 5.5-dB fiber-to-fiber gain     

180 W单频全光纤激光器

高功率单频光纤激器在相干探测、功率光谱合成等方面具有广泛的应用前景。分析了高功率单频光纤激光器中受激布里渊散射效应的抑制方法,研究了放大级特性对受激布里渊散射效应的影响。采用线宽为70 kHz的单频光纤激光器作为种子源,经两级光纤放大,实现了中心波长1 064.1 nm、线宽70 kHz、最高功率为180 W的单频全光纤激光输出,光-光转换效率71.1%,光束质量Mx2=1.2,My2=1.21。分析了改变放大级特性前后输出功率提升的原因,认为改变放大级的温度分布减小了受激布里渊散射效应的增益系数,提高了输出激光的受激布里渊散射阈值,促使改变放大级温度分布后的输出功率大幅提高。该激光器的输出功率仅受限于泵浦功率,进一步提高泵浦功率,有望实现更高功率的单频光纤激光输出。     

1.3-μm vertical-cavity amplifier

We demonstrate the first 1.3-μm vertical-cavity optical amplifier. The amplifier was optically pumped and operated in reflection mode. Optimization of the top mirror reflectivity resulted in a 9.4-dB continuous wave fiber-to-fiber gain, a gain-bandwidth product of 220 GHz, and a saturation output power of -6.1 dBm, all at room temperature. By modulating the pump source, an extinction ratio of 27 dB in the output signal power was obtained     

Theory and design of an ultra-linear square-law approximated LDMOSpower amplifier in class-AB operation

This paper describes a power amplifier, employing parallel-connected laterally diffused metal-oxide semiconductor (LDMOS) devices with optimized channel widths and bias offsets to approximate ideal square-law behavior of the overall transconductance in class-AB operation. The proposed method results in a significant linearity improvement over a large dynamic range in comparison to a conventional amplifier in class-A or class-AB operation. Measurements demonstrate an improvement of 20 dB in third-order intermodulation distortion and 10 dB in adjacent channel power ratio for wide-band code-division multiple access at 12-dB output power backoff from the 1-dB gain compression point. Consequently, this amplifier can be operated more toward the compression region with better linearity and drain efficiency compared to a conventional LDMOS power-amplifier design     

Long wavelength vertical-cavity semiconductor optical amplifiers

This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-μm wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, rye demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of -3.5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature     

2-Gbit/s signal amplification at λ=1.53 μm in anerbium-doped single-mode fiber amplifier

The gain, saturation power, and noise of an erbium-doped single-mode traveling-wave fiber amplifier operating at a wavelength λ=1.53 μm are characterized. In continuous-wave (CW) measurements amplification at 2 Gbit/s was demonstrated with up to 17-dB gain for 1×10^-9 bit error rate at 1.531 μm and a 3-dB full bandwidth of 14 nm. From the determination of the fiber-amplifier's output signal-to-noise ratio versus input signal power during data transmission, it was concluded that, with signal levels used here, signal-spontaneous beat noise limited the receiver sensitivity improvement. With the fiber amplifier acting as an optical preamplifier of the receiver, the best sensitivity was -30 dBm, obtained after installing a polarizer at the fiber amplifier output to reject half of the applied spontaneous emission power. This sensitivity was 6 dB better than without the fiber amplifier, proving that the fiber amplifier can be used as a preamplifier     

Bandwidth-reconfigurable single-passband microwave photonic filter based on stimulated Brillouin scattering

A bandwidth-reconfigurable filter is necessary to meet the need of growing communication capacity and signal coverage frequency range. The stimulated Brillouin scattering (SBS) gain spectrum as a filter passband is used to extract desired microwave signals. Due to the fact that the passband is formed by mapping the Brillouin gain spectrum, bandwidth reconfigurability can be implemented by changing Brillouin gain linewidth. In this paper, a scheme using a 5-lines optical comb acting as a Brillouin pump is experimentally demonstrated. The spectrum of the 5-lines optical comb is extended by a binary phase shift keying (BPSK) pulse modulated signal. Experiments have shown that the 3-dB and 20-dB bandwidths of the filter are 196 MHz and 257 MHz, respectively, and its 20-dB shape factor is 1.31. The passband ripple is ~3.5 dBm with stop-band rejection of 20 dBm under 15 dBm optical pump power.     

A highly stable low-RIN hybrid Brillouin/erbium amplified laser source

We demonstrate a low-noise all-fiber hybrid Brillouin/erbium amplified source consisting of a Brillouin/erbium fiber laser with a subsequent Brillouin amplifier to boost the power and reduce the noise. The same single-mode fibers used in the fiber laser and the amplifier lead to the same amount of Stokes frequency shifts in spite of the environmental variation, ensuring stable Brillouin amplification. The hybridly amplified source features temperature insensitivity, low noise, potentially high power, and low cost. The relative intensity noise of the hybridly amplified source is /spl sim/10 dB lower than that of the erbium-doped fiber amplifier (EDFA)-based source at radio frequencies >200 MHz due to the filtering characteristics of the Brillouin amplification. Compared with an EDFA amplified fiber system, the spurious-free dynamic range of an analog transmission system employing such a laser source is improved by 7.7 dB owning to the lower RIN.     

Gain characteristics of an Er3+-doped multicomponentglass single-mode optical fiber

Experimental results on gain characteristics of an Er³⁺-doped multicomponent glass single-mode optical-fiber amplifier are reported. This amplifier shows a gain spectrum with twin gain peaks of 1.535 and 1.543 μm, providing a broadened gain bandwidth. The apparent 6-dB gain bandwidth is 12 nm. Furthermore, the signal gain of 17 dB and 15-mW pump power is realized at a signal wavelength of 1.536 μm, and a signal gain coefficient of 1.4 dB/mW is achieved     

Tunable multiwavelength Brillouin-erbium fiber laser with a polarization-maintaining fiber Sagnac loop filter

We demonstrate the generation of 12-wavelength comb with 14.5-nm tunable range in the Brillouin-Erbium fiber laser. This is achieved through tuning the gain profile of Erbium-doped fiber by a Sagnac loop filter with 18-cm polarization-maintaining fiber, in conjunction with modifying the wavelength of Brillouin pump. The experiment also demonstrates that the tunable range is closely equal to the 3-dB bandwidth of Sagnac loop filter due to its periodic transmission profile. Meanwhile, the effect of the 980-nm pump on the tunable multiwavelength generation is investigated. The power of 980-nm pump has a great effect on the wavelength number and the output power of the generated multiwavelength comb, but little on the tunable range. This technique may be applicable to multiwavelength operation lasers with a large tunable range.     

Tunable wavelength conversion in a semiconductor-fiber ring laser

A tunable wavelength converter is demonstrated using highly nondegenerate four-wave mixing in a semiconductor-fiber ring cavity with no external pump light and low input signal power requirements. This device allows continuous tuning of both pump and converted wavelengths over the semiconductor optical amplifier gain bandwidth. Results for 11.8-nm down- and 6.9-nm up-wavelength conversion with input signal power as low as -10 dBm have been obtained at 1 Gb/s with less than 1.6-dB power penalty     

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.     

Amplification Effect on Rayleigh Scattering and SBS in 25 km Distributed Fiber Raman Amplifier

The amplification effect on stimulated Brillouin scattering （SBS） and Rayleigh scattering in the backward pumped G652 fibers Raman amplifier have been researched. The signal source is a tunable narrow spectral bandwidth （〈10 MHz） ECL laser and is pumped by the tunable power 1427.2 nm fiber Raman laser. The Rayleigh scattering lines are amplified by fiber Raman amplifier, and Stokes stimulated Brillouin scattering lines are amplified by fiber Raman amplifier and fiber Brillouin amplifier. The SBS lines total gain is a production of the gain of Raman and the gain of Brillouin amplifier. In experiment, the gain of SBS is about 42 dB and the saturation gain of 25 Ion G652 backward FRA is about 25 dB, so the gain of fiber Brillouin amplifier is about 17 dB.