Two-stage Erbium-doped Fiber Amplifier Research Articles

Investigation of System Impairments of Wavelength Division Multiplexing Optical Link with Two-Stage Erbium-Doped Fiber Amplifiers under the Influence of Linear and Nonlinear Effects and Burst-Mode Packet Traffic

Investigation of System Impairments of Wavelength Division Multiplexing Optical Link with Two-Stage Erbium-Doped Fiber Amplifiers under the Influence of Linear and Nonlinear Effects and Burst-Mode Packet Traffic

Investigation of C-band pumping for extended L-band EDFAs

In this study, we present systematic numerical and experimental analysis of high-power C-band light pumping in extended L-band erbium-doped fiber amplifiers (EDFAs). We investigate, for the first time to the best of our knowledge, how C-band light sources can be used as pump sources to extend the bandwidth of L-band EDFAs beyond 1610 nm. Results show that, when using a C-band light source as the sole pump, efficient amplification is obtained over the extended L-band, but at the expense of a higher noise figure. However, the advantage of C-band pumping in terms of power conversion efficiency can be exploited when using a two-stage EDFA, with a first stage pumped by 1480 nm to maintain good noise figure performance and a high-power C-band light source (up to several hundred mW) as the pump source for the second stage. Thus, a 20 dB gain covering 1570–1618 nm with a maximum noise figure of 5.7 dB is demonstrated.

Optimization with genetic algorithm of temperature-dependent fiber length of L-band EDFA gain

Erbium-doped fiber amplifiers (EDFAs) have great importance in long-distance communication. It is required to have equal gain for all signals that are transferred and to avoid loss in the receiver of long-distance communication systems. However, temperature dependence changes the output spectrum of the designed gain-flattening systems. In this study, each erbium-doped fiber (EDF) length of a two-stage L-band EDFA has been optimized using a genetic algorithm method; because of the temperature dependence of EDFAs, there is no general rule. Thus, a simple, fast, dynamic, and highly accurate model has been developed and obtained for different EDF lengths that will fix gain along the L-band. The results have been shown to be very compatible with the previously obtained numerical values.

Arbitrary pulse shaping in Er-doped fiber amplifiers—Possibilities and limitations

Abstract A temporal deformation of nanosecond laser pulses occurring during an amplification process in a two-stage erbium-doped fiber amplifier operating in saturation is presented. We discuss distortion of rectangular laser pulses with duration ranging from 5 ns to 300 ns, generated at 20 kHz repetition rate. Calculations of a suitable peak power scaling factor for distorted pulses are presented. A simple compensation method of temporal pulse distortion, based on the direct current modulation with the use of arbitrary function generator (AFG), is also reported. An appropriate input pulse shape modification leads to obtaining an output amplified pulse with any desired shape. The main limitation of pulse shaping in a fiber amplifier seeded by a narrow linewidth laser diode turns out to be stimulated Brillouin scattering (SBS). However, the pulse shaping method can also improve the amplifier performance by increasing the power threshold of SBS. SBS phenomenon in the context of arbitrary pulse shaping have been also discussed.

Modeling and characterization of all possible triple pass EDFA configurations

The main purpose of designing multi-stage erbium-doped fiber amplifiers (EDFAs) is to achieve higher gain and lower noise figure for long haul optical communication. Among the multi-stage EDFAs, triple pass EDFAs were chosen in this research. This paper presents all possible triple pass EDFA configurations. The well-established one-stage mathematical models were modified to design two-stage and three-stage triple pass EDFAs. Performances of all the configurations were analyzed with pump power ratio and signal power. Optimum length and Optimum pump power ratio were also determined for each and every configuration. From the performance analysis, best triple pass EDFA was recommended for practical design. Key word: Erbium-doped fiber amplifier (EDFA), triple pass, amplified spontaneous emission.

Dispersion-insensitive low-coherent pulses emerging from nonlinear polarization switching

We have experimentally investigated low-repetition nanosecond pulses delivered from an erbium-doped fiber (EDF) laser operating in ultra-large anomalous dispersion regime. The output pulses with rectangular profile and Gaussian spectrum almost keep invariable when they propagate through either normal- or anomalous-dispersion fibers. After nanosecond pulses are amplified via a two-stage EDF amplifier, they are broken up and exhibited as flatly broadened supercontinuum from 1520 to 1700 nm if amplified pulses are launched into a 10-km single-mode fiber, whereas the pulses retain the same duration with a broadband supercontinuum from 1200 to 1750 nm if they are input into a 100-m highly-nonlinear low-dispersion photonic-crystal fiber (PCF). The experimental observations demonstrate that the nanosecond pulses result from nonlinear polarization switching and can be regarded as dispersion-insensitive low-coherent pulses rather than compressible pulses.

Generation and amplification of high-energy nanosecond pulses in a compact all-fiber laser

We have experimentally investigated high-energy rectangular pulses delivering from an erbium-doped fiber laser operating in ultra-large net-negative-dispersion regime. The laser oscillator emits rectangular pulses with approximately Gaussian spectral profiles, adjustable nanoseconds durations, and multi-ten nanojoule energies. The outputted pulses can be further amplified to over 2 μJ without distortion by a two-stage erbium-doped fiber amplifier. Thus, rectangular pulses with controllable durations and energies can be achieved from the compact all-fiber fiber laser system.

Gain optimization of an erbium-doped fiber amplifier and two-stage gain-flattened EDFA with 45 nm flat bandwidth in the L-band

An erbium-doped fiber amplifier (EDFA) is simulated. The variation of gain with different parameters is obtained and the values of these parameters are optimized to achieve a maximum value of gain. A two-stage gain-flattened EDFA consisting of two EDFAs in series is also simulated. In the operating range of 1565–1610 nm, the flat gain of 46 dB is obtained.

Optimization of the two-stage single-pump erbium-doped fiber amplifier with high amplification for low frequency nanoscale pulses

We report the two-stage single-pump configuration of an erbium-doped fiber amplifier, in which a Sagnac interferometer is introduced to reduce the most important contribution of amplified spontaneous emission (ASE) noise, providing significant improvement on the amplifier performance. A Sagnac interferometer, made from a high-birefringence fiber loop, is included between the first and second stages. It is designed to provide transmittance with a period of 46 nm that allows us to adjust the minimum transmission around 1530 nm (peak of ASE noise) and maximum transmission at 1550 nm (signal wavelength). For optimizing the configuration, we measure the erbium-doped fiber parameters and simulate the amplification of the signal along the fiber. In the experiment, a significant absorption coefficient for pump and signal is found. The absorption looks to be too strong for the background absorption, and we suppose that it may be caused at least partly by excited-state absorption (ESA). Including the absorption coefficient allows very good correspondence between simulation and experiment. Experimental results show that with a simple configuration, we obtain up to 53-dB amplification with only 73 mW of pump power.

A hybrid fiber amplifier with 36.9-dBm output power and 70-dB gain

A high-power and extremely high-gain hybrid fiber amplifier with the good noise figure (NF) performance is developed and investigated. It comprises a two-stage erbium-doped fiber amplifier as a pre-amplifier and an erbium/ytterbium co-doped double-cladding fiber amplifier as a post-amplifier. At the signal wavelength of 1550nm, the signal gains of up to 70dB and the maximum output power of 36.9dBm or 4.90W have been demonstrated when the total pump power is 12.5W. We have obtained that the NFs of the hybrid fiber amplifier is varying from 6.12 to 7.72dB for the 1550-nm signal wavelength with the input power range from −21 to +6dBm.

Two‐stage S‐band erbium‐doped fiber amplifier using a depressed‐cladding fiber

AbstractA two‐stage short‐wavelength‐band erbium‐doped fiber amplifier (S‐band EDFA) is demonstrated using a depressed‐cladding erbium‐doped fiber (EDF). The EDF has a fundamental‐mode cutoff wavelength of about 1525 nm in order to suppress amplified spontaneous emission at the longer wavelength. The highest gain curve is obtained by setting the first‐ and second‐stage pumps at 85 and 190 mW, respectively, where the unsaturated gains are obtained at about 28 dB. The gain was limited by the 12‐dBm saturation power of the amplifier. The unsaturated noise figure ranged from 8.5 to 9.3 dB for all pump combinations tested. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 92–94, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20910

Wide-Band Two-Stage Erbium-Doped Fiber Amplifier Module in Parallel Configuration

We propose and experimentally demonstrate a two-stage broadband erbium-doped fiber amplifier module with a coupled structure over a gain bandwidth of 1520 to 1600 nm. As a result, 35.4 and 38.1 dB peak gains can be achieved at 1532 and 1568 nm, respectively, over the operation range. This proposed amplifier can also be used as a broadband amplified-spontaneous-emission light source.

EDFA로 증폭된 고출력 펄스 신호의 소광비 향상

높은 peak 값의 광 펄스 신호를 얻기 위하여 대역통과 필터(band pass filter)를 사용한 2단 구조 erbium-doped fiber amplifier (EDFA)를 구성하여 125 W peak 값과 32 ㏈ 소광비(extinction ratio)를 갖는 펄스 신호를 얻었다. 이때 pulse off power는 79 ㎽이다. pulse off power를 낮추고 소광비를 높이기 위하여 nonlinear optical loop mirror(NOLM)을 사용하였다. NOLM 을 통과한 펄스 신호는 35 W peak 값과 0.3 ㎽ pulse off power, 50.4 ㏈ 소광비를 갖는다. A two-stage erbium-doped fiber amplifier (EDFA) with a band pass filter is used to get optical pulses of high peak value. The pulse signal has a 32 ㏈ extinction ratio, 125 W peak power and 79 ㎽ pulse off power. A nonlinear optical loop mirror (NOLM) is used to lower the pulse off power so as to increase the extinction ratio. The pulse signal after the NOLM has a 50.4 ㏈ extinction ratio, 35 W peak power and 0.3 ㎽ pulse off power.

Comparison of the static and dynamic properties of single- and double-pass partially gain-clamped two-stage L-band EDFAs

We investigate the static and dynamic properties of partially gain-clamped two-stage L-band erbium-doped fiber amplifiers (EDFAs) in single- and double-pass configurations. While both amplifiers can be designed to provide the same gain-clamped performance, the double-pass configuration requires /spl ap/40% less pump power and /spl ap/22% shorter length of EDF in the second stage, and has a corresponding improvement in power conversion efficiency of 45%, but at the expense of an increase in noise figure (/spl ap/0.5 dB) and dynamic gain variation.

Comparison of Performances Between Two-stage and Single-stage L-Band EDFA

Gain enhancement in a long wavelength (L-band) erbium-doped fiber amplifier (EDFA) using a two-stage configuration with dual forward pumping scheme is demonstrated. Compared to a conventional single-stage amplifier, the two-stage amplifiers can improve the small signal gain over the wavelength region from 1560 to 1612 nm. A maximum gain enhancement of 9.6 dB is obtained for a two-stage type II amplifier at the signal wavelength of 1568 nm. The corresponding noise figure is also improved by 0.2 dB.

Two-stage L-band EDFA with gain-clamped characteristics using partial gain-clamping

We theoretically and experimentally investigate the static and dynamic properties of two-stage L-band erbium-doped fiber amplifiers (EDFAs) that are partially gain-clamped. Partial (all-optical) gain-clamping is obtained by forming a fiber grating laser in either the first or the second stage of the two-stage EDFA. Although the amplifiers are only partially gain-clamped, results show that they exhibit good gain-clamped characteristics. Furthermore, the amplifier configuration in which the second stage is gain-clamped can have a very low noise figure and a small transient gain (power) excursion.

Two-stage reflective-type erbium-doped fiber amplifier with enhanced noise figure characteristics

We demonstrate a two-stage reflective-type erbium-doped fiber amplifier with enhanced noise figure characteristics by placing an optical circulator between two erbium-doped fiber segments. Compared to the previous one-stage reflective amplifier, the proposed two-stage reflective amplifier provides noise figure enhancement of more than 2 dB and relatively flat small signal gain characteristics.

Analytical formula for the transient response of erbium-doped fiber amplifiers

In wavelength-division-multiplexing systems with optical amplifiers, channel drop or add can cause power changes in the existing channels. We present an analytical formula for the transient power of the existing channels as a function of time when one or more input channel is dropped or added on an erbium-doped fiber amplifier (EDFA). Although this formula was originally derived from perturbation theory of single-stage EDFA's, it is a good approximation of large-power excursion cases as well as two-stage EDFA's.

All optical gain-clamping in erbium-doped fiber amplifier using stimulated Brillouin scattering

A novel structure of gain clamping in an erbium doped fiber amplifier (EDFA) is demonstrated. Stimulated Brillouin scattering (SBS) from a dispersion compensating fiber module is used as feedback to clamp the gain of the conventional two-stage EDFA. A counter propagating continuous-wave probe beam at 1559 nm operating effectively at -9.5 dBm is used as the SBS pump source. For a dynamic range of 10 dB per channel, gain variation is kept below 1 dB for a single surviving channel in an eight-channel wavelength-division multiplexer.

A gain-flattened two-stage EDFA for WDM optical networks with a fast link control channel

A two-stage erbium-doped fiber amplifier (EDFA) providing constant output power and flat gain regardless of abrupt variations of the number of channels and upstream losses is designed and fabricated by controlling each stage's pump power and mid-stage attenuation. The two-stage EDFAs were successfully applied in the 10 Gbit/s/channel WDM network with a fast link control channel having a 1.6 μs response time to transmit one surviving channel over a 180 km DSF when 7 out of 8 channels are added/dropped.