Co-doped Fiber Amplifier Research Articles

Gain and noise figure enhancement of Er+3/Yb+3 co-doped fiber/Raman hybrid amplifier

An Er/Yb co-doped fiber/Raman hybrid amplifier (HA) is proposed and studied theoretically and analytically to improve the gain and noise figure of optical amplifiers. The calculations are performed under a uniform dopant and steady-state conditions. The initial energy transfer efficiency for Er/Yb co-doped fiber amplifier (EYDFA) is introduced, while the amplified spontaneous emission (ASE) is neglected. The glass fiber used for both Er/Yb and Raman amplifiers is phosphate. Different pump powers are used for both EYDFA and RA with 1μW input signal power, 1m length of Er/Yb amplifier and 25km length of Raman amplifier (RA). The proposed model is validated for Er/Yb co-doped amplifier and Raman amplifier separately by comparing the calculating results with the experimental data. A high gain and low noise figure at 200mW Raman pump power and 500mW Er/Yb pump power are obtained for the proposed HA as compared with the experimental results of EYDFA, Raman amplifier and the EDFA/Raman hybrid amplifier.

Effects of macro-bending on 1500-nm amplified spontaneous emission, gain, and noise figure of erbium-gallium co-doped fiber

The relationships among macro-bending loss, power of the 1500-nm amplified spontaneous emission (ASE), gain, and noise figure of an erbium-gallium co-doped silica fiber amplifier are investigated and explained. The dependence of macro-bending loss on different bending radii is examined. Using different fiber lengths and bending radii, the effects of macro-bending on ASE, gain, and noise figure are analyzed in comparison to an unbent fiber. The ASE power changes because macro-bending alters the number of Er3+ ions in the I13/24 level that decay to the I15/24 level emitting photons of shorter and longer wavelengths. The trade-off relationship that exists between the change in the ASE power and signal loss, where both result from macro-bending, explains the gain change. Fiber length also affects the changes in the ASE power and gain. Noise figure in the longer-wavelength region increases. In the shorter-wavelength region, for a long fiber, the noise figure improves only slightly. For a short fiber, it worsens due to gain decrement. The findings from this study explain the reason for gain improvement upon suppressing either a competing or a noncompeting ASE via filters or macro-bending in other rare-earth-doped fibers.

Enhanced Erbium–Zirconia–Yttria–Aluminum Co-Doped Fiber Amplifier

An efficient optical amplifier is demonstrated using an improved erbium–zirconia–yttria–aluminum co-doped fiber (Zr-EDF) as the gain medium. With a combination of both Zr and Al, we could achieve a high erbium doping concentration with an absorption loss of around 80.0 dB/m at 980 nm. The Zr-EDF is obtained from a fiber preform, which is fabricated in a ternary glass host, i.e., a zirconia–yttria–aluminum co-doped silica fiber, using a modified chemical vapor deposition, in conjunction with a solution doping process. At the optimum length of 1 m, the Zr-EDF amplifier produces a flat gain of 38 dB within a wavelength region between 1530 and 1565 nm with a gain variation of less than 3 dB when the input signal power and 980 nm pump power are fixed at $-$ 30 dBm and 130 mW, respectively. The highest gain of 40.3 dB is obtained at 1560 nm wavelength. Compared with the previous Zr-EDF amplifier, the proposed Zr-EDFA shows improved gain, particularly at longer wavelengths. The gain is enhanced by about 15.8 dB at a wavelength of 1560 nm for an input signal of $-$ 30 dBm.

Gain dynamics in Er(3+):Yb(+) co-doped fiber amplifiers.

Understanding the gain dynamics of fiber amplifiers is essential for the implementation and active stabilization of low noise amplifiers or for coherent beam combining schemes. The gain dynamics of purely Er3+ or Yb3+ doped fiber amplifiers are well studied, whereas no analysis for co-doped systems, especially for Er3+:Yb3+ co-doped fiber amplifiers has been performed, so far. Here, we analyze for the first time the gain dynamics of Er3+:Yb3+ co-doped fiber amplifiers theoretically and experimentally. It is shown that due to the energy transfer between the Yb3+ and Er3+ ions a full analytical solution is not possible. Thus, we used numerical simulations to gain further insights. Comparison of experimental and numerical results shows good qualitative agreement. In addition, we were able to determine the Yb3+-Er3+ transfer function of the energy transfer experimentally.

High Gain / Low NF EYDFA with Distributed Pumping

Optical amplifiers are an indispensable part of today’s network and face increasingly stringent demands on their performance in terms of peak gain, noise figure, cost, compactness, etc with growing transmission rates, increasing link lengths, wavelength division multiplexing and the continual improvisation of technology. Erbium-Ytterbium codoped fiber amplifier ( EYDFA ) an improvement of Erbium doped fiber amplifier (EDFA), helps overcome the limitation of increase in the concentration of excited erbium ions by countering the pairs quenching phenomenon. This paper investigates the role of optical pumping in dual stage single pass EYDFA and the strong dependence of gain on the pump power till a stage of saturation is reached is observed. Further, an amplifier with high gain of 40-46 dB at 1550nm with low noise figure is simulated for very short lengths of active fiber. General Terms Compact in-line amplifier, dual stage configuration, high gain, low noise figure, optical amplifier

Research on High-Power, High-Speed Laser Modulation and Enlarge Experiment

A laser modulation and amplification system is designed to meet the demand of long-range space optical communication, which uses the high-speed semiconductor laser to integrate electro-absorption (EA) modulator as a seed source. Two optical fiber amplifier technologies are used. The erbium-doped fiber amplifier (EDFA) and single-mode semiconductor laser pumping are used in the first-level; erbium ytterbium co-doped fiber amplifier (EYDFA) and 2-4 multimode fiber laser pumping with good temperature characteristics are used in the second level, and the control method is automatic gain control. The experimental result shows that the modulation rate achieves to 10Gbps, and the output optical power achieves to 5W.

Comparative study of all Optical Amplifiers

All Optical Systems exploiting Dense Wavelength Division Multiplexing Systems (DWDMs) have emerged through implementation of optical amplifiers. The performance of DWDM system is enhanced throgh Optical Amplifier. In this review paper several optical amplifiers have been discussed that are suitable for the low-cost, high performance applications of DWDM systems. The different amplifiers, such as Erbium Doped Fiber Amplifiers (EDFA), Raman amplifiers (RA), Semiconductor Optical Amplifier (SOA), Ytterbium Doped Fiber Amplifier (YDFA), Erbium Ytterbium Co-Doped Fiber Amplifier (EYCDFA) and Thulium Doped Fiber Amplifier (TDFA) have different properties that make them suitable for a variety of applications and their advantages can be integrated to improve the performance of all optical systems.

Tm–Ho codoped fiber based all fiber amplification of a gain-switched 2 μm fiber laser

A Tm–Ho codoped fiber amplifier system is built. And, amplification of a gain-switched Tm–Ho codoped fiber laser is investigated. Average output of 300mW is obtained at repetition rate of tens of kHz with an amplification gain bigger than 11dB. And, pulse amplification efficiency of resonantly pumped Tm–Ho codoped single clad fiber is comparable with 793nm pumped Tm-doped double clad fiber. The maximal pulse energy generated is about 13.1μJ, corresponding to a peak power of 282W at 20kHz. During the amplification process, gain-switching, partially modulated gain-switched mode-locking and 100% modulated gain-switched mode-locking are observed sequentially. At gain-switching mode, the laser output enjoys a narrow linewidth of 0.31nm, while at gain-switched mode-locking mode, the spectral linewidth broadens to 0.6nm.

Optimization of the Design of High Power <formula formulatype="inline"><tex Notation="TeX"> $\hbox{Er}^{3+}/\hbox{Yb}^{3+}$</tex></formula>-Codoped Fiber Amplifiers for Space Missions by Means of Particle Swarm Approach

In this paper, the optimization of the design of rare earth-doped cladding-pumped fiber amplifiers is investigated to improve their performance with respect to the constraints associated with space missions. This work is carried out by means of a computer code based on particle swarm optimization (PSO) and rate equation model. We consider a fiber that is radiation tolerant at the space dose levels, and we characterize the radiation response of the amplifier based on it. By simulations, we study how the design of the radiation-tolerant double-cladding Er3+/Yb3+-codoped fiber amplifiers (EYDFAs) can improve the global system response in space. The rate equations model includes the first and secondary energy transfer between Yb3+ and Er3+, the amplified spontaneous emission and the most relevant upconversion and cross relaxation mechanism among the Er3+ ions. The obtained results highlight that the developed PSO algorithm is an efficient and reliable tool to perform the recovering of the most relevant spectroscopic parameters and the optimum design of this kind of devices. These results demonstrated that the performance of high power optical amplifiers can be optimized through such a coupled approach, opening the way for the design of radiation-hardened devices for the most challenging future space missions.

Wavelength tunable single longitudinal mode fiber laser pinned to 25 GHz spacing

ABSTRACTA wavelength tunable single longitudinal mode (SLM) fiber laser is demonstrated with a high power Er‐Yb codoped fiber amplifier (EDFA) used as gain medium. A fiber Fabry‐Perot filter and a bandpass filter ensure single wavelength lasing. To realize SLM operation, a section of unpumped EDF in a Sagnac loop is adopted as a saturable absorber, which results in a self‐induced FBG (frequency band gap) with an ultranarrow bandwidth. The proposed laser is very stable and in SLM operation. The signal to noise ratio is measured about 65 dB. The output laser has a tuning range over 30 nm from 1535 to1565 nm. The tuning step of the proposed laser is 0.20 nm pinned to the ITU grid. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2404–2406, 2014

Optimized flat supercontinuum generation in high nonlinear fibers pumped by a nanosecond Er/Yb Co-doped fiber amplifier

Flat supercontinuum generation has been demonstrated in high nonlinear fibers with zero dispersion wavelengths at 1480 and 1500 nm, which were pumped by a MOPA structured Er/Yb co-doped fiber amplifier based on a modulated nanosecond seed laser with the wavelength of 1552 nm. The spectra and output powers affected by the zero dispersion wavelengths, fiber lengths and pump pulse widths were investigated experimentally. A flat spectrum with 5 dB bandwidth from 1220 nm to beyond 1700 nm (assuming the pump peak was filtered) in the optical spectrum analyzer detectable range was finally obtained by optimizing the fiber length and pump pulse width. The maximum output power was 1.02 W, including the peaks near 1550 nm.

高功率脉冲抽运Er-Yb共掺光纤放大器的理论研究

高功率脉冲抽运Er-Yb共掺光纤放大器的理论研究

Modeling and Experiments of the Gain and Noise Figure for an Irradiated Erbium-Ytterbium Co-Doped Fiber Amplifier

It is crucial to study the effect of radiation on the fiber amplifier devices. In the present paper, the Erbium-ytterbium co-doped fiber amplifier (EYDFA) has been irradiated by a neutron beam of different doses for various exposure times from an Am-241/Be-9 neutron source. The gain and noise figure of the EYDFA have been calculated theoretically and recorded after and before the irradiation to test its performance under the effect of irradiation. In order to show the enhancement in the gain of the fiber amplifier devices, a comparison between the gain of the irradiated EYDFA and Erbium doped Fiber amplifier (EDFA) has been carried out. The calculated results by the proposed model are in good agreement with the experimental ones. It indicates that the gain of EYDFA deteriorates after being irradiated by a neutron dose. Moreover, the gain of irradiated EYDFA has been reduced to 13.8 dB at a dose of 720 Gy.

Double-Seeding of Er/Yb Co-Doped Fiber Amplifiers for Controlling of Yb-ASE

In this paper, we present our investigations on controlling the amplified spontaneous emission from Yb ions in erbium/ytterbium co-doped fiber amplifier by double-seeding of the amplifier with nominal (1.55 μm) and auxiliary (1 μm). The dependence of the amplifier output power on the auxiliary seed wavelength and input power is analyzed. The obtained results are discussed and compared to a conventional amplifier setup without auxiliary seed signal. Our studies show that introducing an auxiliary seed at proper wavelength from the Yb-band provides stable amplifier operation without parasitic lasing at 1 μm and can also increase output power of the nominal 1550 nm signal.

Several hundred kHz repetition rate nanosecond pulses amplification in Er–Yb co-doped fiber amplifier

We have experimentally investigated several hundred kHz repetition rate 1,550-nm nanosecond pulses amplification in Er–Yb co-doped fiber amplifier (EYDFA). The experimental setup has three stage fiber amplifiers. At the output of the second stage EYDFA, Yb3+ ions induced amplified spontaneous emission (Yb-ASE) is not observed owing to the low pump power. In the third stage EYDFA, a simultaneously seeded 1,064-nm continuous-wave laser is used to control Yb-ASE. Without any additional 1,064-nm signal, significantly backward Yb-ASE which caused loss-induced heat accumulation at the input port of the pump combiner can be observed. The monitored temperature at the input port of the pump combiner rapidly grows from 30 to 80 °C when the pump power is turned from 20 to 32 W. When a 196-mW forward 1,064-nm laser is added, the monitored backward Yb-ASE power is significantly declined, and the monitored temperature is kept below 35 °C. But, the additional signal caused a large power fraction at 1,064 nm in the output laser. In our experiment at the maximum pump power of 48.5 W, the total output power is 20 W with ~6.4-W 1,550-nm pulsed laser and ~13-W 1,064-nm continuous-wave laser.

Mid-IR supercontinuum generation in Tm/Ho codoped fiber amplifier

We demonstrate all-fiber-integrated mid-IR supercontinuum generation in a Tm/Ho codoped fiber amplifier, where the codoped fiber is both nonlinear and a gain medium. The observed supercontinuum spectrum ranges from 1760 to 2600 nm and has an extremely high spectral flatness, with a 3 dB bandwidth ∼635 nm (from 1845 to 2480 nm). In the Tm/Ho codoped fiber, as well as the nonlinear optical processes, the Tm3+ and Ho3+ ions also play important roles in mid-IR supercontinuum generation. The 3F4–3H6 transition for Tm3+ radiates a laser in the 1.8–2.1 μm spectral region, the 5I7–5I8 transition for Ho3+ radiates a laser around 2.1 μm and the 3H4–3H5 transition for Tm3+ radiates a laser in the 2.2–2.5 μm spectral region. All of these energy level transitions contribute towards supercontinuum generation.

Quantitative analysis of energy transfer processes in Thulium–Bismuth germanate co-doped fiber amplifier

Energy transfer processes in Thulium–Bismuth co-doped germanate fiber amplifier at 1800nm region have been studied quantitatively in this work. Energy transfer models are utilized in order to investigate the effect of dopants concentration on energy transfer parameters. A series of non-linear rate equations were derived using the energy transfer parameters and solved by means of a semi-analytical method. A general model of optical fiber amplifier in conjunction with rate equations is employed to simulate Thulium and Bismuth ions population distribution along the fiber. Thulium and Bismuth concentrations are noted as critical factors that control the output power and saturation length. The optimum values of Thulium and Bismuth concentration which result in maximum gain at 1800nm are 0.5wt.% and 2wt.% respectively.

56 dB Gain EYDFA with improved noise figure with dual-stage partial double pass configuration

An efficient erbium/ytterbium co-doped fiber amplifier (EYDFA) is demonstrated by using a dual-stage partial double pass structure with a band pass filter (BPF). The amplifier achieves the maximum small signal gain of 56dB and the corresponding noise figure of 4.66dB at 1536nm with an input signal power and total pump power of −50dBm and 140mW, respectively. Compared with a conventional single-stage amplifier, the maximum gain enhancement of 16.99dB is obtained at 1544nm with the corresponding noise figure is improved by 2dB. The proposed amplifier structure only uses a single pump source with a partial double pass scheme to provide a high gain and dual-stage structure to provide the low noise figure.

A Review of Recent Development of Efficient High-Power Continuous- Wave Er-Yb Codoped Fiber Amplifiers

Abstract: In this paper, we will review the recent developments of high-power continuous-wave (CW) Er-Yb codoped fi-ber amplifiers (EYDFAs). Several related patents and a couple of methods of improving the performance of high-power EYDFAs are reviewed. Current research results show that the Yb-band amplified spontaneous emission (Yb-ASE) is the main reason that limits the efficiency and stability of an EYDFA at high pump power. Several methods and experimental results dedicated to suppress the Yb-ASE are introduced. Current and potential future developments of high-power EYD-FAs are summarized in the last part of this paper. Keywords: Erbium, fiber amplifiers, fiber lasers, MOPA, ytterbium 1. INTRODUCTION High-power fiber laser sources in the 1.5-μm band have made a great progress in recent years. Due to their many advantages, such as relatively eye-safe nature, low atmos-phere transmission loss, light weight, low loss in communi-cation fibers, and readily available reliable and cost-effective fiber communication components, they are of great potential for both military and civilian applications, such as laser in-frared radars (LIDARs), free-space communications, mate-rial processing and so on [1-3]. To flexibly control the linewidth, wavelength, and beam quality of a high-power fiber laser source, a master-oscillator power-amplifier (MOPA) configuration is commonly used. In this configuration, the master-oscillator generates a low-power high beam quality seed, and then the seed is amplified through several stages of power-amplifier until the desired output power is achieved. Apparently, the available power and performance of a MOPA system is largely determined by the performance of the power-amplifier(s). The details of the MOPA configuration will be introduced in the next sec-tion. In the 1.5-μm band high-power MOPAs, double-clad erbium-ytterbium codoped fibers (EYDFs) are usually used as the gain media of the power-amplifier. This fiber has an inner cladding surrounding the core and its refractive index is lower than the core but larger than the outer cladding [4]. The cross-sectional shape of the inner cladding is usually non-circular, which can enhance the mode mixing to pro-mote the pump absorption [5].

Er/Yb co-doped fiber amplifier with wavelength-tuned Yb-band ring resonator

Erbium-ytterbium co-doped fiber amplifier with wavelength-tuned Yb-band loop resonator is presented. The amplified spontaneous emission (ASE) from Yb ions is utilized to stimulate a laser emission at several wavelengths from the 1μm band in the 1550nm amplifier. The wavelength of this lasing is tuned by introducing a fiber Bragg grating (FBG). The results show, that the overall efficiency of the amplifier at nominal 1550nm wavelength can be increased by introducing a feedback loop with 1040nm and 1050nm FBG. This loop also protects the Er/Yb amplifier from parasitic lasing at 1μm and allows significant output power scaling without risk of self-pulsing.