Switchable multiwavelength erbium-doped fiber ring laser with a multisection high-birefringence fiber loop mirror

We proposed and demonstrated a new concept of switchable multiwavelength erbium-doped fiber ring laser with a multisection high-birefringence fiber loop mirror (HiBi-FLM). The HiBi-FLM results in the laser operating on different allowed wavelengths. The wavelength switching can be achieved by modifying the reflection spectrum of HiBi-FLM through two polarization controllers. The experiment demonstrates the switchable lasing operation within the random combination of three wavelengths, as well as with a large (/spl sim/40 dB) output signal to background noise ratio.     

Modeling erbium-doped fiber amplifiers

Erbium-doped fiber amplifiers are modeled using the propagation and rate equations of a homogeneous two-level laser medium. Numerical methods are used to analyze the effects of optical modes and erbium confinement on amplifier performance, and to calculate both the gain and amplified spontaneous emission (ASE) spectra. Fibers with confined erbium doping are completely characterized from easily measured parameters: the ratio of the linear ion density to fluorescence lifetime, and the absorption of gain spectra. Analytical techniques then allow accurate evaluation of gain, saturation, and noise in low-gain amplifiers (G≲20 dB)     

Gain flattening of an erbium-doped fiber amplifier using ahigh-birefringence fiber loop mirror

We propose a flexible method for flattening the gain profile of an erbium-doped fiber amplifier (EDFA). The method is based on a high-birefringence fiber loop mirror (HiBi-FLM), which contains a number of high-birefringence fiber sections and polarization controllers. We show that, by setting the polarization controllers properly, the reflection spectrum of the loop mirror can be adjusted to compensate for the variations in the gain profile of the EDFA. The method is demonstrated experimentally by using a single-section HiBi-FLM and a two-section HiBi-FLM, respectively, With a two-section HiBi-FLM, we are able to flatten the gain profile of an EDFA to within ±0.9 dB over a bandwidth of 33 nm at the center wavelength of 1543 nm, under different operating conditions of the EDFA     

Mode-locked erbium-doped fiber ring laser using intracavity polarization-maintaining loop mirror

Erbium-doped fiber lasers at repetition rate of 40 and 80 GHz are demonstrated in an injection-locked and rational harmonic mode-locked ring cavity. The cavity has a polarization-maintaining loop mirror. The injection-locking pulse is generated at repetition rates of 20 and 40 GHz from another rational harmonic mode-locked fiber laser. When these pulses are injected into the second fiber laser, pulses at twice the repetition rates viz. 40 and 80 GHz are produced.     

A simple black box model for erbium-doped fiber amplifiers

We demonstrate a simple black box model to evaluate both saturated gain and corresponding noise figure. This approach is simple and very suitable for system modeling with satisfied accuracy     

全保偏非线性偏振环形镜锁模掺铒光纤激光器

研究了基于非线性偏振环形镜锁模的全保偏光纤激光器锁模机制。在非线性偏振环形镜中,用偏振分束器取代传统的非线性放大环形镜锁模激光器中的光纤耦合器,并辅以非互易性元件和增益光纤,作为全保偏光纤激光器中实现稳定锁模的核心器件。构建了一台基于非线性偏振环形镜的掺铒光纤锁模激光振荡器,实现了重复频率75 MHz,时域脉冲宽度141 fs,总输出功率约30 mW的稳定锁模脉冲序列输出。该激光器具有双向输出,且通过调节腔内波片可调节输出功率。此外,对激光器输出功率和重复频率的稳定性进行了评价,在自由运转情况下,1 h内输出脉冲序列的平均功率波动小于0.05%,重复频率的1 s相对稳定度为2.010-8。该结构的全保偏光纤激光器可开机自启动锁模,且环境稳定性高、重复频率较高、脉冲宽度窄,能满足激光测距、激光加工、激光光谱成像、航天等应用对超短脉冲光源的需求。     

Design optimization for efficient erbium-doped fiber amplifiers

The gain and pumping efficiency of aluminosilicate erbium-doped fiber amplifiers (EDFAs) are analyzed as a function of guiding parameters and Er-doping profile for two pump wavelengths of λ _p=980 nm and λ_p=1.47 μm. Three designs of fiber-amplifier waveguides are considered: one with the same mode size as standard 1.5-μm communication fibers (type 1); one with the same mode size as standard 1.5-μm dispersion-shifted fibers (type 2); and one with mode size smaller than those of communication fibers (type 3). For the 1.47-μm pump, fundamental LP₀₁ mode excitation is assumed, while for the λ_p=980-nm pump, concurrent excitation of LP₁₁ modes is considered. It is shown that excitation of higher-order pump modes at 980 nm does not significantly affect the amplifier gain performance. The effect of concentrating the Er³⁺ doping near the center of the fiber core is shown to increase the amplifier gain coefficients by a factor of 1.5 to 2     

基于可调谐光纤环形镜滤波器的多波长布里渊掺铒光纤激光器

通过使用非线性放大的光纤环形 镜滤波器(AFLMF),构造了一种新颖的多波长布里渊掺铒光纤激光器(E DFL)线形结构。非线性AFLMF由掺铒光纤放大器(EDFA,由980n m泵浦抽运 一段EDF构成)、偏振控制器(PC)和耦合器构成,减少了腔内基于波长的损耗,并且能够灵 活地控制反射 光以及激光腔内输入和输出光的强度。在布里渊泵浦功率为25mW、 980nm泵浦功率为200mW时,获得了波 长间隔为0.08nm的14个波长的激光输出以及50nm的可调谐范围。通过调节980nm抽运光功率、PC以及布里渊泵浦光波长,实现了可调谐的多波长输出。研究 了980nm抽运光功率以及PC对斯托克斯光波数的影响。     

Circulating loop transmission experiments for the study oflong-haul transmission systems using erbium-doped fiber amplifiers

A circulating loop transmission experiment is a useful tool for the research and development of long-haul transmission systems that use erbium-doped fiber-amplifier repeaters. Circulating loop techniques, applied to an amplifier chain of modest length, can provide an experimental platform to study a broad range of transmission phenomena for EDFA-based transmission systems. A loop experiment attempts to simulate the transmission performance of a multi-thousand kilometer long system by reusing or recirculating an optical signal through a modest length amplifier chain of tens to hundreds of kilometers. This paper reviews original loop techniques developed to study various parameters of long-haul transmission using erbium-doped fiber-amplifiers repeaters for undersea systems. Transmission experiments were performed at transoceanic distances with 33 and 46 km amplifier spacing, operating at 5 and 10 Gb/s. Experimental data is provided here for various parameters, including bit error ratio, Q-factor, and spectral broadening     

Nonlinear optical loop mirror based on standard communication fiber

We numerically analyze the effectiveness of a nonlinear optical loop mirror (NOLM) based on standard communication fiber with randomly varying birefringence for demultiplexing streams of picosecond pulses at 100 GHz. A broad switching window of about three pulse full-width at half maximum (FWHM) can be obtained. The device performance is defined by the pulse duration, the dispersion of the fiber, and the fiber length. We show that imperfect averaging of the randomly varying birefringence causes amplitude fluctuations on the NOLM transmission curve. We also show that the Raman self-frequency shift does not affect the NOLM switching characteristics at picosecond pulse durations     

Average power analysis technique for erbium-doped fiber amplifiers

It is shown that an average power analysis technique similar to that used for semiconductor optical amplifiers can be used to analyze both the discrete and the distributed fiber amplifier for multiwavelength operation without the need for numerical integration. It is also shown to give results that are in excellent agreement with those from other studies. This approach gives performance insights that are not otherwise readily available     

Novel fiber sensor arrays using erbium-doped fiber amplifiers

We examine the signal-to-noise ratio (SNR) performance of a novel type of time domain multiplexed sensor arrays in which low gain (1-10 dB) fiber amplifiers are incorporated to compensate for splitting losses between sensors. The system noise figure for passive and amplified sensor arrays is presented, along with expressions to optimize the array parameters for high SNRs. We show that practical amplified sensor arrays exhibit low system noise figures that allow much larger arrays (hundreds of sensors) than passive arrays     

Performance of high-concentration erbium-doped fiber amplifiers

The full characteristics for two high-concentration erbium-doped fibers are reported. The comparison of the fibers characteristics indicates that design of fiber geometry can be used to partially compensate for the degradation of the amplifiers performance due to upconversion processes. For high NA fiber the 22-dB small-signal gain, and 3.5-dB noise figure are obtained from a 24-cm length of fiber. We report a photon quantum conversion efficiency of 28%, which corresponds to the highest efficiency obtained in heavily doped fibers     

Transient analysis of erbium-doped fiber amplifiers

The transient response of an erbium-doped fiber amplifier (EDFA) pumped at 1.48 μm, taking into account the gain-saturation effects due to the amplified spontaneous emission (ASE), is studied theoretically and experimentally. The theoretical model is used to predict the gain saturation and recovery times of an EDFA and its effects to the amplification of optical pulses     

Modulation instability in erbium-doped fiber amplifiers

The onset of modulation instability in erbium-doped fiber amplifiers (EDFAs) is studied through a stability analysis of the underlying nonlinear Schrodinger equation. The existence of gain in EDFAs lowers the threshold for modulation instability considerably compared with the case of undoped fibers. Modulation instability generates multiple pulses when a single pulse is amplified. It can also create multiple subpulses in mode-locked fiber lasers, a feature observed experimentally. Numerical simulations show that EDFAs can convert a continuous-wave optical signal into a train of high-repetition rate femtosecond pulses     

Measuring gain and noise figure of erbium-doped fiber amplifiers using a broad-band source and a transmission filter

We report a unique low-cost technique for measuring gain and noise figure (NF) in erbium-doped fiber amplifiers using a broad-band amplified spontaneous emission source and a transmission filter, by extracting the slope and intercept of output power spectral density versus input power spectral density at filter edges. The required filter depth is 30 dB. Discrepancies of /spl les/0.3 dB are found between gain or NF obtained from this technique and those measured using conventional spectral-interpolation technique employing multiple lasers at 100-GHz spacing across the C-band.     

Efficient erbium-doped fiber amplifiers incorporating an opticalisolator

A composite-EDFA configuration which incorporates an optical isolator has been investigated theoretically and experimentally. The isolator prevents the build-up of the backward-ASE and results in an amplifier with high gain and near-quantum-limited noise figure (NF). The optimum position of the isolator has been calculated as a function of the pump power so that minimum NF and maximum gain are achieved simultaneously. It is shown that under practical pump powers, the optimized composite EDFA exhibits a gain improvement of about 5 dB and a NF reduction in excess of 1.5 dB when compared with an optimized conventional EDFA. It is also shown that with further optimization the composite EDFA can be employed in a practical fiber link as a pre-amplifier without the use of an input isolator. Finally, a high-gain composite EDFA has been experimentally demonstrated which exhibits a gain of 51 dB (54 dB) and NF of 3.1 dB for only 435 mW (93 mW) of pump power     

Switchable dual-wavelength erbium-doped fiber laser based on the photonic crystal fiber loop mirror and chirped fiber Bragg grating

The switchable dual-wavelength erbium-doped fiber laser(EDFL) with a two-mode photonic crystal fiber(PCF) loop mirror and a chirped fiber Bragg grating(CFBG) at room temperature is proposed and experimentally demonstrated.The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror,with the air-holes of the PCF intentionally collapsing at the splices.By adjusting the state of the polarization controller(PC) appropriately,the laser can be switched between ...     

Spectral hole burning in erbium-doped fiber amplifiers

A new theoretical/numerical model of the spectral hole burning (SHB) effect in erbium-doped fiber amplifiers (EDFAs) is suggested. A new measurement technique for SHB measurement is developed. Experiments are conducted to identify the particular mechanism of SHB. A computer simulation program is developed using this approach. The shape and depth of the spectral hole are in accordance with the suggested theory.