Optimum signal wavelength for a distributed erbium-doped fiberamplifier

Theoretical analysis of a 100-km-long transparent germanosilicate distributed erbium-doped optical fiber has been carried out. It is shown that the optimum signal wavelength is 1.554 μm both considering the noise performance and the necessary pump power for achieving unity gain when the distributed erbium-doped fibers are pumped at 1.48 μm     

Trunk and distribution network application of erbium-doped fiberamplifier

Recent research on erbium-doped fiber amplifiers and their applications to trunk and distribution networks is described. Simple methods to estimate amplification performances from only three basic erbium-doped fiber parameters are proposed. It is clarified that optical amplifiers greatly influence the development of future optical communication systems     

Efficient multiwavelength dynamic model for erbium-doped fiberamplifier

An efficient full spectrum (1480-1600 nm) large-signal transient dynamic model of an erbium-doped fiber amplifier (EDFA) is developed. A technique to speed up the simulation by a factor of 1000 using artificial delay lines based on the transmission-line model (TLM) is presented. Simulations and experimental results show the delay line method is not detrimental to the accuracy of the model. The efficiency of this model means it is ideal for simulating the dynamics of large wavelength division multiplexed (WDM) networks if included in a network simulator     

Automatic optical loss compensation with erbium-doped fiberamplifier

The effect of unwanted optical loss varying over 15 dB is automatically offset with an erbium-doped fiber amplifier used in an optical feedback configuration. The loss compensation is possible for signal wavelengths over a 13 nm range centered at about 1550 nm. The system dynamic range for loss fluctuation frequencies is zero to several kilohertz. The proposed loss compensation scheme simultaneously provides an automatic gain control function that stabilizes the gain against slow changes in input signal power or pump power     

Gain flattening by using dual-core fiber in erbium-doped fiberamplifier

We show that a dual-core optical fiber in which one core is doped with erbium and the other core is undoped can be used as an optical amplifier with very flat gain over the wavelength range 1520 nm to 1560 nm. The gain variation over this range is less than 0.7 db. The noise floor is less than 4 dB     

High-gain coefficient long-wavelength-band erbium-doped fiberamplifier using 1530-nm band pump

A 1530-nm band has been studied as a pump wavelength for the long-wavelength-band erbium-doped fiber amplifier (L-band EDFA). The pump source is built using a tunable light source and cascaded conventional-band (C-band) EDFA. The L-band EDFA uses a forward pumping scheme. Within the 1530-nm band, the 1545-nm pump demonstrates 0.45-dB/mW gain coefficient, which is twice better than that of conventional 1480-nm pumped EDFA. The noise figure of the 1530-nm pump is at worst 6.36 dB, which is 0.75 dB higher than that of the 1480-nm pumped EDFA. Such high-gain coefficient indicates that the L-band EDFA consumes low power     

Ultralong dispersion-shifted erbium-doped fiber amplifier and itsapplication to soliton transmission

Distributed, dispersion-shifted erbium-doped fiber amplifiers with doping concentrations as low as 0.1-0.5 p.p.m. (0.1-0.5×10^-4 wt.%) were fabricated and their grain characteristics studied for the purpose of soliton amplification. A 9.4-km dual-shape-core-type amplifier with a 0.5-p.p.m. concentration had a gain of more than 20 dB at 1.535 μm and 10 dB at 1.552 μm with a forward pumping configuration, and it could successfully amplify and transmit a 20-ps soliton pulse train at a 2.5-GHz repetition rate. The soliton transmission characteristics of an 18.2 km long fiber amplifier were studied using backward and forward pumping. It was found that A=1.5 soliton pulses with a pulse width of 20 ps could be amplified over 18.2 km at a repetition rate of 5 GHz, where soliton narrowing to 16 ps was observed     

A high-gain, high-output saturation power erbium-doped fiberamplifier pumped at 532 nm

An erbium-doped fiber amplifier with a high small-signal gain of 42 dB at the gain peak of 1536.4 nm, a pumping efficiency of 1.6 dB/mW, and an output saturation power of 10 dBm is obtained with a pump power of 60 mW at 532 nm using the second harmonic of a Nd:YAG laser as the pump source. These experimental results indicate that diode-laser-pumped mini-Nd:YAG lasers with intracavity frequency-doubling have an output power at 532 nm of 100-150 mW that can be of great interest for practical system applications using high-gain, high-output-power erbium-doped fiber amplifiers     

An erbium-doped tellurite fiber amplifier for WDM systems with dispersion-shifted fibers

This letter investigates the feasibility of an erbium-doped tellurite fiber amplifier (EDTFA) with a 1581- to 1616-nm amplification band for a wavelength-division-multiplexing transmission system in the L-band that employs dispersion-shifted fiber (DSF). A 10-Gbit/s, 40-channel-transmission from 1581 to 1616 nm in the L-band, where EDTFA's are employed as a post-amplifier, repeaters, and a pre-amplifier, is error-free through a 320-km DSF. The EDTFA can increase both the transmission capacity and the allowable maximum input power launched into a DSF.     

Transmission and saturation performance of dispersion-shifted distributed erbium fibre

The gain spectra for a bidirectionally pumped 30 km length of lightly doped dispersion shifted erbium fibre and the amplification performance in saturation of a 54 km length of similar fibre are presented. The longer length comprised six spliced fibres with an average erbium concentration in the core of approximately 60 p.p.b. and could be rendered lossless with 2*30 mW of pump power for low power signals. With 2*55 mW of pump power a peak fibre gain of 17 dB at 1536 nm was realised; as the input signal power was increased the gain was suppressed but the fibre remained transparent for signal powers up to -2 dBm.<>     

Fundamental design of a distributed erbium-doped fiber amplifierfor 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     

Transmission line with distributed erbium-doped fiber amplifier

We show the advantages of distributed erbium-doped fiber amplifiers (EDFAs) over lumped EDFAs. Using the distributed EDFA for 50%-100% of the transmission line lessens the signal degradation compared to the conventional transmission line. We also show the feasibility of the gain-flattened d-EDFA transmission line. An experiment shows that the gain peak is shifted and flattened at low pump powers     

Utilization of a dispersion-shifted fiber for simultaneousmeasurement of distributed strain and temperature through Brillouinfrequency shift

We propose and realize a new method that utilizes a dispersion-shifted fiber having compound compositions with different temperature coefficients in core to simultaneously measure the distributed strain and temperature based on Brillouin frequency shift. In a 3682-m sensing length of large-effective-area nonzero dispersion-shifted fiber, a temperature resolution of 5°C, a strain resolution of 60 με, and a spatial resolution of 2 m are achieved simultaneously     

Performance of optical cable composed of dispersion-shifted single-mode fibers

A low-loss dispersion-shifted single-mode fiber cable has been fabricated. The index-profile of the fiber is nearly parabolic and the relative index difference is 0.8 percent. An average cable loss is 0.229 dB/km at 1.55 μm, and excellent loss stability has been achieved in the cabling process and in the temperature and mechanical test.     

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     

Analysis of distributed erbium-doped fiber amplifiers with fiber background loss

An accurate model for erbium-doped fiber amplifiers with fiber background loss applicable to the unsaturated gain regime is presented. Exact analytical solutions are derived for the output pump power, gain, and amplified spontaneous noise as a function of input pump power in the cases of unidirectional or bidirectional pumping. An exact relation is also derived between the pump threshold and the pump required for fiber transparency. Such expressions are particularly useful to model distributed fiber amplifiers and to determine the optimal fiber parameters corresponding to a given pumping scheme. As an example, the analytical solutions are used to study the pump power requirement for distributed fiber amplifiers unidirectionally pumped at 1.48 mu m, and to determine an optimum Er/sup 3+/ absorption coefficient.<>     

UV generation by frequency quadrupling of a Yb-doped fiberamplifier

The pulsed output of a Yb-doped fiber amplifier was frequency doubled and quadrupled to generate visible and UV radiation. When pumped with 150-200 mW at 980 nm and seeded at 1064 nm, the amplifier produced an average power of 90 mW at 1064 nm, 45 mW at 532 nm, and 1.4 mW at 266 nm. These results indicate that frequency-converted fiber lasers and amplifiers will be able to replace conventional tunable UV sources (e,g,, frequency-converted dye lasers) in a number of applications     

Design of unidirectional erbium-doped waveguide ring laser with asymmetric distributed Bragg grating

Proposed is the employment of a second-order asymmetric Bragg grating as an intra-cavity element enabling unidirectional operation of integrated ring lasers. This idea is examined by means of numerical simulations for the case of erbium-doped silica-on-silicon waveguide ring lasers. It is shown that suppression of lasing in one direction can be designed to achieve 20 dB.     

Nonlinear, dispersion-free 10 GHz optical pulse train transmission in distributed erbium-doped fibre

The transmission of a 10 GHz repetition rate optical pulse train over a 28.5 km long distributed erbium-doped fibre amplifier is reported. In the linear dispersion regime, the pulses broaden so that the tails of adjacent pulses overlap. However, given sufficiently high signal powers, the optical Kerr effect causes pulse narrowing back to the original 18 ps pulsewidth.<>     

Performance analysis of an optical serial-to-parallel converterwith erbium-doped fiber amplifier

In this paper, we develop a performance analysis of an surface-emitting second harmonic generation (SESHG) optical serial-to-parallel converter using an erbium-doped fiber amplifier (EDFA) as a preamplifier. The analysis is complicated by the fourth-order nonlinearity that acts on the signal plus amplified spontaneous emission (ASE) noise to create many beat noises at the binary decision device. However, we demonstrate that Gaussian approximation for the beat noise statistics is reasonable. We calculate the BER of the system as a function of the SHG nonlinear cross section (A^NL), EDFA gain, the bandwidth of the optical filter that band-limits the ASE noise, and the timing pulse-to-data pulse power ratio. We find that for reasonable values of these and other parameters, the EDFA/SESHG serial-to-parallel converter combination should be able to operate at or below a BER of 10^-12. We find that small increments (0-2 dB) in the signal power that is input to the EDFA are enough to compensate the effects of ASE noise for most of the parameter variations we consider. From this point of view, the ASE noise has little effect on system performance. However, when the input power is fixed, we show evidence in terms of BER that the ASE noise plays a significant role, particularly in the high A^NL, high gain case. Also in this case, we show that the optimal timing pulse-to-data pulse power ratio is somewhat different from the value that is optimal for the system without an EDFA