Noise characteristics of Er3+-doped fiber amplifierspumped by 0.98 and 1.48 μm laser diodes

Measured noise characteristics of Er³⁺-doped optical fiber amplifiers pumped by 0.98- and 1.48-μm laser diodes (LDs) are reported. The noise figures estimated from the beat noise between signal and spontaneous emission are 3.2 dB for pumping by 0.98-μm LD and 4.1 dB for pumping by 1.48-μm LD. The beat noise between spontaneous emission components and the spontaneous shot noise for the 0.98-μm pumping are lower than those for the 1.48-μm pumping     

Application of an Er3+-doped fibre amplifier to an OTDRoperating at 1.6 μm

An erbium-doped fibre amplifier with a high gain coefficient at 1.6 μm is constructed employing a dual pumping scheme. The amplifier is successfully applied to an OTDR, producing output optical pulses characterised by a peak power of 476 mW for a duration of 1 μs     

Laser diode pumped Er3+-doped fiber amplifier in a 565Mbit/s DPSK coherent transmission experiment

A laser-diode-pumped erbium-doped fiber amplifier, exhibiting 9-dB gain, has been operated as an in-line optical repeater in a 565-Mb/s coherent optical communications system. A sensitivity penalty of 0.4 dB was observed when the amplifier was positioned 35 dB away from the receiver, thus indicating a system improvement of 8.6 dB. By progressively reducing the coupling loss between amplifier and receiver, the noise figure of the contradirectionally pumped amplifier was calculated to be 5.4 dB, a value which is consistent with simple noise theory     

Stable relaxation-oscillation Er3+-doped fiber laser

We demonstrate a simple method to produce high-energy pulses with peak powers up to 100 times their average power and with duration on the order of 1 μs using the synchronization of relaxation oscillations by drive current modulation of the intracavity pump laser diode. The forced sustained relaxation oscillations are shown to depend on wavelength, and the frequency locking curve exhibits a strong asymmetry with hysteresis behavior     

Fundamental limits on Nd3+-doped fiber amplifierperformance at 1.3 μm

To explore the fundamental limits on performance at 1.3 μm, a model for Nd³⁺-doped fiber amplifiers which includes signal saturation and excited state absorption (ESA) at the signal wavelength has been constructed. Ignoring ESA, the difference in pump efficiency between a low-performance and a high-performance glass host is ≈60%, indicating that ESA is the critical parameter distinguishing experimental results reported for different materials. The pump efficiency for a linear Nd³⁺ amplifier is an order of magnitude less than for an Er³⁺ amplifier without ESA and degrades still further with its inclusion. Applications as power amplifiers are more promising, because, in principle, high power conversion efficiencies can be obtained     

Laser diode pumped operation of Er3+-doped fibreamplifier

Semiconductor laser-diode pumped operation of an erbium-doped fibre amplifier, exhibiting 6 dB gain and operating at 1536 nm, is reported. The amplifier was optically pumped at 807 nm using a self-injection-locked semiconductor laser diode array     

Optimum Er3+-doped fiber amplifier design for optical AMvideo signal distribution systems

An investigation into the transmission characteristics of erbium-doped fiber amplifiers for use in optical AM frequency division multiplexing (FDM) video distribution systems is reported. The output signal power and noise characteristics of erbium-doped fibers were measured for different fiber lengths and different pump powers. The experimental results confirm that there exists an optimum amplifier design which gives the maximum distribution number when the pump power and the required video quality are given     

结构稳定的掺Er3+光纤环形腔激光器

报道了一种腔体结构稳定的掺Er     

A unidirectional Er3+-doped fiber ring laser withoutisolator

An Er³⁺-doped fiber ring laser with unidirectional operation without optical isolator has been investigated for different cavity conditions. The fiber ring laser cavity is built in such a way that the optical fields propagating in the two directions suffer different losses. As a consequence, the laser oscillation appears in a quasi-unidirectional form. By incorporating a fiber pigtailed bandpass filter to enhance mode competition, a purely unidirectional tunable fiber ring laser is obtained with high efficiency and broad tunability     

Spectral noise figure of Er3+-doped fiber amplifiers

The erbium-doped fiber amplifier noise figure spectrum and its evolution under various pumping regimes is analyzed. The analysis shows that noise figures in the range ±0.15 dB around the 3-dB quantum limit are possible within a spectral band of 50 nm. This demonstrates the possibility of quantum-limited amplification for broadband wavelength-division multiplexed (WDM) signals     

Modeling and optimization of short Yb3+-sensitized Er3+-doped fiber amplifiers

Short high-concentration Yb³⁺-sensitized Er³⁺-doped fiber amplifiers are modeled and numerically investigated in the small-signal domain. Concentration quenching is included with a term quadratic in the concentration of excited Er³⁺ . We find that for fibers shorter than 1 m, the small-signal gain can be larger for sensitized fibers than for non-sensitized ones (31 dB gain vs. 22 dB at 5 cm). Without concentration quenching (e.g. for long fibers), Yb³⁺-free amplifiers have a higher small-signal gain. The achievable gain of the sensitized amplifier is independent of the pump laser wavelength, if the Yb-concentration is correspondingly optimized. However, restrictions on allowable Yb-concentrations imply that for a specific pump wavelength, a finite range of amplifiers lengths is suitable     

被动锁模掺Er3+氟化物光纤激光器理论研究

根据非线性薛定谔方程建立了基于可饱和吸收体被动锁模掺Er3+氟化物光纤激光器的理论模型,研究了中红外超短脉冲在掺Er3+氟化物光纤激光器中形成的物理机制,数值模拟了被动锁模掺Er3+氟化物光纤激光器中中红外超短脉冲的演化过程,重点分析了掺Er3+增益光纤长度,可饱和吸收体不饱和损耗对被动锁模掺Er3+氟化物光纤激光器产生中红外超短脉冲的影响,并给出了参数设置范围。研究发现:当小信号增益系数、可饱和吸收体不饱和损耗、腔内净色散量为一定值,掺Er3+氟化物光纤长度在一定范围时,才会出现稳定的锁模脉冲,且随着掺Er3+氟化物光纤长度增加脉冲宽度变窄、光谱变宽、峰值功率增高;当掺Er3+氟化物光纤长度、腔内净色散量、小信号增益系数为一定值时,可饱和吸收体不饱和损耗在一定的范围时可以得到稳定的锁模脉冲,且随着可饱和吸收体不饱和损耗的增加脉冲宽度变窄,光谱先变宽后变窄变化范围不大,峰值功率增加。     

Pr3+-doped 1.3 μm fibre laser using direct coateddichroic mirrors

A 1.3 μm fibre laser consisting of a 1000 ppm (mol) Pr³⁺ -doped fluoride glass fibre with dichroic mirrors coated onto the fibre endfaces and an Nd-YLF pump laser is presented. The output mirror reflectivity R is calculated to be 50% at the lasing wavelength. Producing a maximum output power of 50 mW. The laser threshold and slope efficiency are 300 mW and 8%, respectively. The theoretically predicted values correspond with the experimental values     

基于重叠光栅的双波长掺铒光子晶体光纤激光器

提出了一种基于光纤重叠光栅的双波长光子晶体光纤激光器。激光器采用线形腔结构,掺铒光子晶体光纤为激光器的增益介质,反射率均高于99%的光纤重叠光栅用作激光器的波长选择器件。基于增益均衡技术,抑制谐振腔内的模式竞争,在室温下获得了稳定的双波长激光同时输出。实验结果表明:其3 dB线宽小于0.02 nm,30 dB线宽小于0.25 nm,SMSR为54.34 dB,双波长激光的中心波长间隔为0.932 nm。该双波长激光器输出的双波长激光具有较好的稳定性。     

High-gain and high-efficiency diode laser pumped fiber amplifier at1.56 μm

Gain of an erbium-doped amplifier was optimized for operation at 1.56 μm, resulting in gains of up to 20 dB and slope efficiencies of 0.66 dB/mW. The amplifier is plug compatible with existing fiber networks. The gains of up to 20 dB were achieved using 1.48-1.49 μm laser diode pump sources with powers of 30 mW launched into the input of the system. The erbium-doped fiber used had an Er³⁺ concentration of roughly 30 p.p.m. in a GeO₂-Al₂O ₃SiO₂ host, and a core diameter of 7.0 μm     

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     

On the dynamics of population inversion for 3 μm Er3+lasers

A generalized model for 3-μm (⁴I_11/2 →⁴I_13/2)Er lasers is proposed. The essential energy transfer processes present in the single-doped Er ³⁺ systems (up-conversion from ⁴I_13/2, up-conversion from ⁴ I_11/2, cross-relaxation from ⁴S _3/2), as well as those present in Cr³⁺ codoped Er ³⁺ systems, are taken into account. In the frame of this model, the main features of 3 μm Er³⁺ lasers, such as long pulse or CW operation, the change of emission wavelength as a function of pumping conditions, and the effects of codoping with Ho³⁺ or Tm³⁺ ions, are explained     

Upconversion pumped thulium-doped fluoride fiber amplifier andlaser operating at 1.47 μm

A 1.064-μm band upconversion pumped Tm³⁺-doped fluoride fiber amplifier and a laser both operating at 1.47 μm are investigated in detail. The two devices are based on the ³F ₄→³H₄ transition in a trivalent thulium ion, which is a self-terminating system. When pumped at 1.064 μm, the amplifier has a gain of over 10 dB from 1.44 to 1.51 μm and a low-noise characteristic. Also, the fiber laser generates a high-output power of over 100 mW with a slope efficiency of 59% at around 1.47 μm. These levels of performance will be important for optical communication systems     

Gain enhanced L-band Er3+-doped fiber amplifierutilizing unwanted backward ASE

A novel method of enhancing gain in the long wavelength band erbium-doped fiber amplifier is described using the unwanted amplified spontaneous emission (ASE) self-pumping technique. A dual-stage amplifier is deployed, where the unwanted backward ASE from the first stage is fully utilized to pump the second stage amplifier. Gain improvement is observed that enables support for higher channel capacities in wavelength-division-multiplexed systems with negligible noise figure penalties. Flat-gain values in excess of 24 dB and noise figures <5 dB are obtained from the proposed amplifier with a higher channel counts compared to the conventional amplifier     

Compact and highly efficient fiber amplifier modules pumped by a0.98-μm laser diode

Highly efficient and small-size erbium-doped fibers with a gain coefficient of 4.9 dB/mW and a strained quantum-well-type InGaAs laser diode with a lasing wavelength of 0.98 μm as a pumped light source. As a result, the module 4×6×1.5 cm, realized a maximum net gain of 33 dB with an electricity consumption of only 175 mW, which corresponds to a drive current of 80 mA. The module consists of four individual components: a pumping laser diode submodule, a wavelength-division-multiplexing-type fiber coupler, a polarization-insensitive optical isolator, and an erbium-doped single-mode fiber coil