High pumping-efficiency L-band erbium-doped fiber ASE source using double-pass bidirectional-pumping configuration

We present a high pumping-efficiency L-band (1565/spl sim/1605 nm) erbium-doped fiber amplified spontaneous-emission (ASE) source using a double-pass bidirectional pumping configuration. Such design gives rise to relaxing the danger in resonant lasing, allowing high pumping-power operation, and therefore, enhancing the pumping-conversion efficiency. The ASE source has a mean wavelength of 1584.3 nm, a spectral linewidth of 41.6 nm, and an output power of 71.8 mW with a ripple of 0.5 dB without using any external spectral filters. The high pumping efficiency of 42.2% is achieved.     

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     

The contribution to cross-phase modulation in L-band WDM systemsfrom erbium-doped fiber amplifiers

It has been suggested that the level of cross-phase modulation (XPM) produced in erbium-doped fiber amplifiers (EDFA's) may be greater than that produced in the transmission fiber. We measure and compare the levels of XPM produced in an EDFA to that produced in both dispersion-shifted fiber (DSF) and conventional transmission fiber for a 10-Gb/s L-band wavelength-division-multiplexed system. Our results show that, for a system with twenty channels, the levels of XPM produced by our amplifier was negligible compared to that from the DSF, and a factor of approximately nine smaller than for the conventional fiber     

Demonstration of highly efficient flat-gain L-band erbium-doped fiber amplifiers by incorporating a fiber Bragg grating

A flat-gain output of 13.5 (15.5) dBm is obtained over 30 nm in the L-band with only a 97 (130)-mW pumping of a 980-nm laser diode. Such highly efficient flat-gain L-band erbium-doped fiber amplifiers are achieved by simply adding a regular fiber Bragg grating. An efficient and simple gain-clamping operation is also demonstrated.     

Layout optimization for erbium-doped waveguide amplifiers

The optical layout of erbium-doped waveguide amplifiers (EDWAs) based on spiral and folded spiral planar lightwave circuits is considered. It is shown that layouts may be ranked according to their ability to provide maximum gain within a given chip area and an optimum layout based on a spiral containing both straight and curved waveguide sections is identified from an initial set. The analysis is initially based on simple geometric principles. A detailed optical simulation is then carried out using an algorithm that links a five-level rate equation model with beam propagation by the method of lines. The results confirm the choice of optimum layout     

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     

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     

Noise figure for erbium-doped optical fibre amplifiers

A rate equation model is used to calculate the excess noise figure for erbium-doped fibre amplifiers. It is shown that erbium amplifiers can operate with high gain and can have noise figures only 0.2 dB above the quantum limit     

A novel frequency-independent third-order intermodulation distortion cancellation technique for BJT amplifiers

Second-harmonic control is implemented in a balanced common-emitter configuration to facilitate frequency-independent third-order intermodulation distortion cancellation. Moreover, this circuit configuration facilitates a simultaneous match for either power and linearity or noise and linearity. Experiments demonstrated an improvement of over 15 dB in the output third-order intercept point while maintaining freedom in the choice of load and source impedance.     

Optimum pumping configuration for L-band EDFA incorporating ASE pump source

L-band gain improvement through usage of secondary pumping sources in the form of amplified spontaneous emission (ASE) was conducted. A simulation of the three-level rate equation that precedes the experimental approach provides a limited overview of the behavior of various inputs into the active medium-the erbium-doped fiber. Gain improvement as high as 6 dB was attained while incurring minimal noise figure penalty; in this case as low as 1 dB. For an L-band amplifier system employing ASE to improve gain, pumping the system counterdirectionally with ASE while the 980- or 1480-nm pumps are being used in a copropagating configuration would yield the best overall performance in terms of gain.     

A novel technique for suppression of parasitic superfluorescence in backward Raman amplifiers

The major parasitic modes of backward Raman amplifiers are different forms of superfluorescent forward Raman scattering. It is shown that spatial, and/or temporal variation of the Raman frequency in the scattering medium can inhibit amplification of spontaneously scattered light by creating off-resonant conditions in the forward direction. If the frequencies of the optical pulses are properly varied in time (the pulses are chirped), the required resonance condition for amplification of a counterpropagating Stokes wave can be maintained throughout the medium. Raman transition frequencies can be varied in an atomic vapor by application of a magnetic field via the Zeeman effect. The use of thallium (T1) metal vapors for scattering XeCl or KrF excimer laser radiation is considered as a particular example.     

A standard fiber-based loop mirror as a gain-flattening filter for erbium-doped fiber amplifiers

We report flattening of the amplified spontaneous emission (ASE) spectrum from an erbium-doped fiber (EDF) using a standard fiber-based loop mirror (FLM), realized with an "over-coupled" fiber coupler. Through simulation, a bend-induced birefringent FLM as a gain-flattening filter is designed. Subsequently, an over-coupled coupler with a free spectral range of 140 nm is fabricated to realize the FLM, which is integrated to an EDF that is pumped by a 980-nm laser diode. By introducing an appropriate amount of bend-induced birefringence in the loop, the ASE spectrum of the EDF could be flattened within /spl plusmn/0.5 dB over a wavelength range of 32 nm in the C-band.     

Optimum core design for erbium-doped integrated optical amplifiers in silica-on-silicon

The gain an Er/P-doped integrated optical waveguide amplifier has been calculated as a function of waveguide core design, pump power, and background loss. The optimum core width varies from 2 to 3 mu m for pump powers close to the threshold for amplification up to 3-5 mu m for high gain operation.<>     

1.58-μm band gain-flattened erbium-doped fiber amplifiers forWDM transmission systems

This paper describes the amplification characteristics of gain-flattened Er³⁺-doped fiber amplifiers (EDFAs) by using 0.98-μm and 1.48-μm band pumping for a 1.58-μm band WDM signal. Silica-based Er³⁺-doped fiber (S-EDF) and fluoride-based Er ³⁺-doped fiber (F-EDF) have gain-flattened wavelength ranges from 1570 to 1600 nm and from 1565 to 1600 nm, respectively, and exhibit uniform gain characteristics with gain excursions of 0.7 and 1.0 dB, and the figure of merit of the gain flatness (gain excursion/average signal gain) of 3 and 4.3%, respectively, for an eight-channel signal in the 1.58-μm band. We show that 1.48-μm band pumping has a better quantum conversion efficiency and gain coefficient, and that 0.98-μm band pumping is effective for improving the noise characteristics. We also show that the EDFAs consisting of two cascaded amplification units pumped in the 0.98-μm and 1.48-μm bands are effective in constructing low-noise and high-gain 1.58-μm band amplifiers     

A noise optimization technique for integrated low-noise amplifiers

Based on measured four-noise parameters and two-port noise theory, considerations for noise optimization of integrated low-noise amplifier (LNA) designs are presented. If arbitrary values of source impedance are allowed, optimal noise performance of the LNA is obtained by adjusting the source degeneration inductance. Even for a fixed source impedance, the integrated LNA can achieve near NF/sub min/ by choosing an appropriate device geometry along with an optimal bias condition. An 800 MHz LNA has been implemented in a standard 0.24 /spl mu/m CMOS technology. The amplifier possesses a 0.9 dB noise figure with a 7.1 dBm third-order input intercept point, while drawing 7.5 mW from a 2.0 V power supply, demonstrating that the proposed methodology can accurately predict noise performance of integrated LNA designs.     

一种测量光纤喇曼放大器增益的方法

根据喇曼放大器的增益和噪声的定义,提出一种独特的低成本的测量噪声和增益的方法.该方法是用一个梳状滤波器对宽带ASE信号进行调制,并在输入和输出信号的凹陷的较陡处进行取点,从而得出某个局部的输入和输出信号的线性关系,进一步计算出光纤喇曼放大器的增益和噪声系数.对该方法进行了数值模拟,以便进一步阐明测量原理.     

Gain-shifted thulium-doped fibre amplifiers employing novel highconcentration doping technique

A novel high thulium concentration doping technique is proposed for shifting the gain band in thulium-doped fibre amplifiers (TDFAs). The gain peak shifts from 1473 to 1505 nm when the Tm³⁺ concentration is increased from 2000 to 8000 ppm. The authors have achieved gains of >18 dB and a noise figure (NF) of <7 dB from 1480 to 1510 nm (30 nm bandwidth) for a total pump power of 500 mW     

Analysis of gain dynamics of erbium-doped fiber amplifiers for wavelength-division-multiplexing networks

The gain dynamics in erbium-doped fibers (EDFs) with various numerical apertures (NAs) and cutoff wavelengths used in amplifiers employed in wavelength-division-multiplexing (WDM) networks is investigated by using the time-dependent amplifier model. The calculation shows that the transient response at a time immediately after some channels have been dropped depends on the cutoff wavelength, and the cutoff wavelength for the highest transient response is independent of NA. The calculation also shows that the transient response for a constant cutoff wavelength increases with an increase in NA. Experimental results for the transient response of EDFs with similar NAs and different cutoff wavelengths agree with the calculated results for various input signal powers, input signal power changes, and surviving channel wavelengths when there is no influence of neglection of amplified spontaneous emission and EDF background loss on the calculation.     

A review of the fabrication and properties of erbium-doped fibersfor optical amplifiers

Erbium-doped fiber has become the central component of nearly all optical amplifiers. Applications reported include repeaters, power amplifiers, preamplifiers, and distributed amplifiers. To date, nearly all the fiber used in these devices has been silica based and fabricated by variations on the major telecommunications fiber technology. Disadvantages of the silica-based host glass, such as low solubility of the rare-earth ions and narrowband fluorescence, have been carefully addressed and solutions have been found to overcome these potential drawbacks. Details of the current status of fabrication methods, matching particular fibers for specific applications, together with optimizing the fiber for high efficiency, are presented