Bidirectional Pumping Scheme Research Articles

Optimum configuration for high-power low-noise-figure erbium-doped fiber amplifiers for lightwave CATV applications

We theoretically investigate various 980-nm-pumping configurations for simultaneously achieving high-power, low-noise-figure erbium-doped fiber amplifiers (EDFAs) acted as power amplifiers and in-line amplifiers for lightwave analog cable-television (CATV) applications. The target of saturated output power and noise figure is ≥100 mW and ≤5 dB, respectively. Those configurations considered include single-stage and two-stage designs in dual-forward, dual-backward, and bidirectional pumping schemes, each with and without the midway optical isolator. The bidirectional pumping scheme includes the forward-and-backward, and the backward-and-forward cases. A total of nine configurations are examined and compared in this paper. We find that the midway isolator for all amplifier configurations operated at large input signal level (>0 dBm) in CATV analog systems did not contribute to noise figure reduction, but the additional insertion loss reduced the output power. This is quite opposite to the case for an amplifier operated at small input signal power in the digital systems. From both system power budget and carrier-to-noise ratio (CNR) points of view, among all configurations, the single-staged forward-and-backward bidirectional pumping scheme without using inter-staged components is the best amplifier configuration to offer the highest output power with fairly low noise figure and highly satisfied CNR performance. It is also the simplest scheme with the shortest required EDF length. This conclusion provides the configuration selection of designing both power and in-line amplifiers for AM CATV lightwave systems.

High-bit-rate soliton transmission using distributed amplification and dispersion management

We show through numerical simulations that the use of distributed amplification together with dispersion management can permit single-channel speeds of 40 Gb/s over transoceanic distances while maintaining 100-km spacing between pumping stations. We achieve this performance by using a bidirectional pumping scheme and optimizing the dopant density such that the peak-power variations over each fiber span remain below 0.4 dB. The required pump power is less than 80 mW for a dopant density of 200 ions/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Development of an efficient praseodymium-doped fiber amplifier

This paper describes the development of an efficient praseodymium-doped fluoride fiber amplifier (PDFA) using newly developed PbF/sub 2/-InF/sub 3/-based fluoride single-mode fiber. First, the spectroscopic properties of Pr/sup 3+/ in PbF/sub 2/-InF/sub 3/-based and ZrF/sub 4/-based fluoride glass are compared and then the fabrication of high-NA PbF/sub 2/-InF/sub 3/-based fluoride single-mode fiber is presented. The gain coefficients obtained with the developed fiber are 0.36 dB/mW with a forward pumping scheme and 0.4 dB/mW with a bidirectional pumping scheme. We use this newly developed fiber to construct two types of an efficient PDFA module. We realized a 19-in rack size PDFA module with a master oscillator/power amplifier laser diode (MOPA-LD) and a plug-in type PDFA module with a wavelength-stabilized 1.017-/spl mu/m LD and describe their amplification characteristics.

Investigation of efficient pump scheme for Pr/sup 3+/-doped fluoride fiber amplifiers

Numerical analysis reveals that a bi-directional pump scheme suppresses the population reduction of the /sup 1/G/sub 4/ level due to pump ESA and cooperative upconversion. It is confirmed experimentally that the gain coefficient increases from 0.21 to 0.24 dB/mW, which is the maximum single pass gain coefficient ever reported, with the bi-directional pump scheme. It is shown that this pump scheme is effective in extracting the potential of Pr/sup 3+/-doped fluoride fibers. >

Design of long distance distributed erbium doped fibre amplifier

A comprehensive theoretical analysis of a distributed erbium doped fibre amplifier has been carried out, using a highly accurate model. Designs based on bidirectional pumping schemes are evaluated. Optimum step index profile designs are given based on the tradeoff between dispersion and nonlinearities of the optical fibre.

Noise performance evaluation of distributed erbium-doped fiber amplifiers with bidirectional pumping at 1.48 mu m

An accurate model for unsaturated fiber amplifiers with fiber background loss is used to determine optimal parameters for distributed amplification in erbium-doped fibers. Pump power at 1.48 mu m and erbium-doping levels required for transparency are studied for both unidirectional and bidirectional pumping schemes. An optimal erbium absorption coefficient which minimizes the required pump power is found. However, this case corresponds to the highest amplifier noise figure. The authors conclude that, in practice, distributed erbium-doped fiber amplifiers are not significantly advantageous compared to 980-nm-pumped lumped amplifier schemes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Fundamental design of a distributed erbium-doped fiber amplifier for long-distance transmission

Comprehensive theoretical analysis on the design of a distributed erbium-doped fiber amplifier for long-distance transmission has been carried out, using a highly accurate model. The dispersion of the optical fiber as a function of the numerical aperture and the cutoff wavelength is included. Designs based on a bidirectional pumping scheme are evaluated, taking nonlinearities into account. The optimum value of the numerical aperture will be evaluated for cutoff wavelengths where the propagating pump power is single moded. For distances between each pumping station in the region between 10 and 100 km, the optimum ratio of copropagating and counterpropagating pump power will also be evaluated. >

Excited-state absorption cross sections in the 800-nm band for Er-doped, Al/P-silica fibers: Measurements and amplifier modeling

Excited-state absorption (ESA) cross sections were determined for the 800-nm band of Er-doped, Al/P-silica fibers. The oscillator strength of the ESA transition exceeds that of the 800 nm, ground-state absorption (GSA) transition by a factor of approximately= 2.3, in reasonable agreement with a Judd-Ofelt calculation. The extended, long-wavelength tail of the GSA band leads to a region around 820 nm where the GSA cross section approximately= ESA cross section. The cross sections were incorporated into an amplifier model for pumping in the 800-nm band. Codirectional and the bidirectional pumping schemes were analyzed for excitation near the peak and in the long wavelength tail of the GSA band. Pumping in the tail for either pumping scheme or pumping near the peak for the bidirectional scheme are predicted to produce a significant improvement in the small-signal gain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Erbium-doped fibres pumped in 800 nm band

Erbium-doped silica and fluorophosphate fibre amplifiers pumped at 800 nm are examined using a highly quantitative model. The bidirectional pumping scheme is more efficient when excited state absorption is significant. The fluorophosphate glass host is at least 60% more efficient than the Al/P silica.

High gain two-stage amplification with erbium-doped fibre amplifier

Unsaturated net gain of 51 dB is obtained for 1.551 mu m signal light by using two-stage erbium-doped fibre amplifiers pumped by 1.48 mu m laser diodes. This is achieved by using both an optical bandpass filter to suppress amplified spontaneous emission from the first stage amplifier and a bidirectional pumping scheme in the second amplifier to increase saturation output power. >