Brillouin fibre laser enhanced by Raman amplification

A multiple-wavelength Brillouin fibre laser is demonstrated, with channel spacings of /spl sim/10.5 GHz, using Raman amplification in dispersion-shifted optical fibre. More than 20 frequency lines with /spl sim/2 kHz linewidths are obtained using a 14.5 km length of fibre and a 1.3 MHz linewidth Brillouin pump. Gain depletion due to amplified spontaneous emission limits the total number of cascaded Brillouin lines. At high Raman pump powers, the laser produces a pulse train at the repetition rate corresponding to the cavity round-trip time.     

Cascaded Raman fibre laser for stable dual-wavelength operation

The authors have demonstrated a stable and tunable dual-wavelength Raman fibre laser, which can be used as a pump source for a hybrid type and gain controlled C- and L-band distributed Raman and lumped erbium-doped fibre amplifiers. Intensity and wavelength tuning of the two lasing modes at 1480 nm and 1500 nm are achieved by tuning one and both of the fibre gratings used in the laser cavity, respectively     

Six-wavelength Raman fibre laser for C- and L-band Ramanamplification and dynamic gain flattening

A novel six-wavelength Raman fibre laser exhibiting a dynamic gain flattening capability in the C + L optical telecommunications band is demonstrated. The power distribution in the six lasing wavelengths is adjusted with voltage-controlled Bragg-grating output couplers. The fibre laser was used as a pump source for distributed Raman amplification in several transmission span lengths. For example, the multiwavelength laser provides an on/off gain of 19 dB over a 100 km span of True-Wave RS optical fibre. The measured gain flatness is 1.7 dB peak-peak and the effective noise figure ranges from 1.6 to -5.2 dB in the 1530 to 1600 nm bandwidth     

Highly efficient and tunable Nd/sup 3+/ doped fluoride fibre laser operating in 1-3 mu m band

A highly efficient and tunable Nd/sup 3+/ doped fluoride fibre laser operating in the 1.3 mu m band pumped at 0.8 mu m is demonstrated. The pump laser is a titanium sapphire laser and the tuning element is a dielectric multicoated bandpass filter inserted in the cavity. The oscillation wavelength was successfully tuned from 1.315 to 1.348 mu m for the first time.<>     

Output-power-clamped Raman fibre laser with suppression of low-frequency RIN transfer from pump sources

An optical approach is demonstrated for suppressing low-frequency relative intensity noise (RIN) transfer from pump sources to the author's proposed Raman fibre laser (RFL). Low-frequency RIN transfer suppression is accomplished by outputting not the second- but first-order Stokes, which output power is clamped by the lasing second-order Stokes in the cavity and can be easily tuned in a large dynamic range. Thus, this technique fits the RFL for use as pump sources in Raman fibre amplifiers.     

Raman amplification at 1.118 ?m in single-mode fibre and its limitation by Brillouin scattering

A forward Raman gain of 2.9 dB has been measured in a 1.1 km low-loss fibre using an LED at 1.118 ?m as a signal source and a CW Nd: YAG laser as a pump. Backward Brillouin scattering, which depletes the pump power towards the end of the fibre, is found to enhance the Raman gain at the front end.     

Double-cavity Raman fibre lasers with suppressed pump-to-Stokes transfer of low-frequency RIN

Double-cavity Raman fibre lasers with two longitudinally concatenated Stokes cavities are shown to permit the suppression of low-frequency relative-intensity-noise (RIN) transfer from the pump laser to the Stokes output. This concept can provide low-noise Raman fibre lasers for use as pump sources in co-pumped Raman amplifiers.     

Switchable dual-wavelength Raman erbium-doped fibre laser

A fibre Bragg grating feedback fibre laser with both Raman and erbium-doped fibre pumps is proposed. Dual-wavelength switching is achieved by controlling the power of the Raman pump. The characteristics of the dual-wavelength switching are studied experimentally, and the mechanism is explained physically.     

High-gain, monolithic, cascaded fibre Raman amplifier operating at1.3 μm

A 39 dB-gain silica fibre Raman amplifier is demonstrated at 1.3 μm using a 1064 nm pump. Cascaded Raman generation and amplification are achieved in a monolithic ring cavity constructed solely from conventional fibre components, i.e. fusion WDM couplers and standard silica fibre     

Profile dependence and measurement of absolute Raman scattering cross-section in optical fibres

A simple measurement method for the absolute Raman scattering cross-section of an optical fibre is presented. This method does not require a high power pump laser and it measures the fibre directly. It is also shown that the calculation of the cross-section depends on the fibre structure, such as its refractive index profile and the differential attenuation between the pump wavelength and Raman wavelength.<>     

Erbium doped fluorozirconate fibre laser operating at 1.66 and 1.72 mu m

Pulsed laser emission at 1.66 and 1.72 mu m has been observed in a multimode fluorozirconate fibre doped with erbium under excitation at 514 nm. The threshold absorbed pump power for laser oscillation was measured as 90 mW.<>     

Semiconductor laser pumping of continuous-wave Pr/sup 3+/-doped ZBLAN fibre laser

Blue semiconductor laser pumped continuous-wave laser oscillation of a Pr-doped ZrF/sub 4/-BaF/sub 2/-LaF/sub 3/-AlF/sub 3/-NaF fibre in the red spectral range is reported for the first time. The pump power is provided by a frequency-doubled optically pumped semiconductor laser system. When pumped with 300 mW at a wavelength of 479.7 nm, the Pr/sup 3+/-laser emitted 94 mW of output power at a wavelength of 635 nm. Threshold pump power and slope efficiency with respect to the incident pump power were determined to be 49.7 mW and 41.5%, respectively.     

High efficiency diode pumped thulium-doped silica fibre lasers withintracore Bragg gratings in the 1.9-2.1 μm band

Diode pumped continuous wave laser oscillation at wavelengths between 1.9 and 2.1 μm in a thulium doped silica fibre that uses Bragg reflectors for cavity feedback is reported. These lasers exhibit low pump power thresholds and quantum efficiencies close to unity     

Raman amplifier based long-distance, remote FBG strain sensor with EDF broadband source recycling residual Raman pump

A novel and simple Raman amplifier based long-distance fibre Bragg grating (FBG) sensing system without any additional broadband light source is demonstrated. With the simplified system configuration recycling residual Raman pump power for generation of amplified spontaneous emission in an erbium-doped fibre (EDF), the high quality of remote strain sensing operation at a location of 50 km is achieved.     

Wavelength tunable CW Raman fibre ring laser operating at 1486-1551nm

A continuous-wave, wavelength tunable Raman fibre ring laser has been demonstrated operating at 1485-1551 nm with peak output power of over 400 mW, pumped at 1420 nm by a 1.58 W fibre laser     

抽运功率配置对双向喇曼放大器性能的影响

为了研究抽运功率配置对双向抽运光纤喇曼放大器性能的影响,基于已有的耦合方程,采用数值仿真方法,分析了不同抽运功率配置对双向抽运光纤喇曼放大器的增益、增益饱和以及抽运功率转换效率的影响。结果表明,双向抽运光纤喇曼放大器的增益、增益饱和以及抽运功率转换效率特性均介于同向和反向抽运光纤喇曼放大器之间,并且随着同向抽运功率在抽运总功率中所占比例的升高,增益、增益饱和功率和抽运功率转换效率的数值增加;大信号、抽运功率较大时,抽运功率配置对双向抽运光纤喇曼放大器性能的影响显著。这对双向抽运光纤喇曼放大器和光纤激光研究具有一定的参考价值。     

Tunable fibre Raman oscillator in the 1.32?1.41 ?m spectral region using a low-loss, low OH? single-mode fibre

We report the first tunable fibre Raman oscillator in the 1.32?1.41 ?m spectral region using a 1 km-long low-loss (0.32 dB/km at 1.32 ?m) and low OH? (1 dB/km at 1.39 ?m) single-mode fibre as the nonlinear medium, and a CW mode-locked Nd: YAG laser at 1.32 ?m as the pump source.     

Theory of the synchronously pumped fiber Raman laser

Analyses of the synchronously pumped fiber Raman laser are presented under the parabolic approximation for gain shaping in both frequency and time domains. A master equation for the Stokes pulse consists of the group velocity dispersion of the fiber, the gain dispersion of the stimulated Raman scattering, a gain-shaping term due to the pump curvature, small depletion, and a walk-off effect. The pump power dependences of the Stokes power and the pulse width and the threshold condition are revealed. The frequency tunability of the present laser is also discussed. It is shown that the oscillation wavelength (carrier frequency of the Stokes pulse) will change linearly with Stokes power because of walk off during depletion.     

激光二极管抽运主动调Q Nd:GdVO4自受激拉曼激光器

采用激光二极管（LD）抽运、主动调Q的方式，利用c向切割的Nd：GdVO4晶体的自受激拉曼散射（self-SRS）效应，实现了结构紧凑、高效的脉冲拉曼激光器。在输入功率为1．8W，主动调Q10kHz时，自受激拉曼激光器产生了稳定的1176nm的斯托克斯（Stokes）脉冲光，斯托克斯光的单脉冲能量为10μJ，脉冲宽度为19ns。此时，自受激拉曼散射的阈值仅为510mW，斯托克斯光的转换效率为5．6％。实验结果表明，有效的自受激拉曼变频可以通过一个c向切割的Nd：GdVO4晶体，采用主动调Q的方式来实现。     

High-gain optical amplification of laser diode signal by Raman scattering in single-mode fibres

The letter reports, for the first time, a 45 dB amplification gain of a laser diode signal emitting at 1.24 ?m, in a single-mode fibre, with low pump power, using the stimulated Raman scattering effect.