Erbium-ytterbium Doped Fiber Amplifier Research Articles

FWM crosstalk reduction and performance investigation of SC-DWDM system employing ML techniques

This article presents a comprehensive approach towards mitigation of four-wave mixing (FWM) induced crosstalk for a super-combined dense wavelength division multiplexing (SC-DWDM) system with in-line erbium-ytterbium doped fiber amplifier (EYDFA) + Raman hybrid optical amplifier (HOA). The performance of modified duo-binary return to zero (MDRZ) and differential phase-shift keying (DPSK) modulation formats employed on alternate channels of the 40-channel system have been compared considering equal (ECSA) and unequal channel spacing allocation (UECSA) schemes at a data rate of 40 Gbps. In the case of the UECSA scheme, the DPSK modulated channels have shown a reduction of FWM crosstalk components and intensities of up to 80% and 40 dB, respectively at a low bit error rate (BER) of 2.5 × 10−14. Different artificial neural network (ANN) techniques have been compared for gain spectrum estimation of HOA has been carried out based on input features of channel spacing, the number of channels and wavelength. Levenberg-Marquardt's (LM) model proves to be the best fit as compared to other ANN techniques. The k-nearest neighbours (KNN), support vector machine (SVM) and decision tree (DT) algorithms have been applied for the estimation of impairments based on root mean square error (RMSE) and coefficient of determination (R2) values as performance metrics. The best-performing model results applying an ANN approach with predicted R2 values of quality - factor (Q-factor) and noise figure (NF) of 0.74 and 0.56, respectively.

FTTH 방송 오버레이용 EYDFA 부품과 핵심 시스템 개발 및 연구

In this study, erbium ytterbium doped fiber amplifier components and core systems for fiber to the home broadcast overlays are developed and evaluated to ensure stable high-power light even during long-distance data transmission in broadcast networks. Consequently , data transmission in the broadcasting network is found to be low in loss, long-distance transmission is deemed possible, and stable optical signals can be amplified using domestic equipment instead of expensive foreign equipment. The tools developed in this study provide an opportunity to reduce dependence on overseas products by allowing domestic technology, which lacks optical amplifier technology, to compete with overseas products at a low price. In the future, these tools are expected to accommodate more members from the optical communication field and be applied to various fields that use high-power light.

Optimization of the Radiation Response of Backup Optical Fiber Amplifiers for Space Missions

We investigated the X-ray radiation impact on the performances of “backup” erbium-doped fiber amplifiers (EDFAs) and erbium-ytterbium-doped fiber amplifier (EYDFA). These devices are exposed to the space radiation constraints, unpowered in the “OFF” mode, up to their hypothetic activation during the mission. This atypical profile of use must be considered as it could lead to a higher radiation vulnerability. To carry out this study, active optical fibers differing in terms of radiation hardness have been exposed to steady-state X-rays under different profiles of amplifier use: the gain degradation is measured by varying the pumping conditions, that drive the photobleaching (PB) phenomenon, during the radiation exposure: “ON” (100% ON), “OFF” (0% ON), and “OFF–ON–OFF” with powering 2% or 10% of the time. Our results show that the impact of the pump and its related PB efficiency depend on the selected active fiber to build the amplifier. An important result is that the “backup” EDFA designed with radiation-hardened Ce-doped fiber does not suffer from an extra-degradation due to the “OFF” mode, contrary to the one designed with a nonrad-hard fiber. For this latter one, it is indeed possible to reduce the extra-gain degradation by powering the amplifier for short time periods during the “OFF” state; otherwise, the EDFA recovers this extra-gain degradation in a few hours after turning “ON” in our test conditions. For the tested radiation-tolerant EYDFA, an enhanced vulnerability is observed for the “OFF” amplifier, that can be reduced too by briefly powering the amplifier. The origins of these effects are discussed based on the properties of point defects related to the aluminosilicate (EDFA) and phosphosilicate (EYDFA) glasses of the fiber.

Q-switched fiber laser employing a passive polarization-maintaining thulium-doped fiber as a saturable absorber

We present the application of polarization-maintaining thulium-doped fiber (PM-TDF) as a saturable absorber in an erbium-ytterbium-doped fiber laser. A commercial erbium-ytterbium-doped fiber amplifier (EYDFA) was employed in a ring cavity laser configuration with a sub-cavity that allowed bidirectional light propagation through PM-TDF. The Q-switched pulse operation was attained at 1563 nm with EYDFA output power of 720 – 980 mW. At maximum output power, the shortest pulse width of 1.4 µs was attained at 29.4 kHz repetition rate, with up to 41.7 mW of average output power and 1.44 µJ of pulse energy. The proposed fiber laser architecture demonstrated good stability in the time and frequency domains, thus recognizing its potential for applications that require high damage threshold saturable absorber devices.

Widely interval-adjustable multiwavelength erbium-ytterbium doped fiber laser based on micro-air cavity

We propose a widely interval-adjustable multiwavelength erbium-ytterbium doped fiber laser (EYDFL) based on a micro-air cavity (MAC). The fabricated MAC functions as a selective channel filter for multiwavelength generation with adjustable wavelength interval. By adjusting the MAC length from 0.10 to 2.40 mm, the wavelength interval can be continuously tuned from 8.61 to 0.47 nm, respectively. When the MAC length is set at 2.40 mm and erbium-ytterbium doped fiber amplifier at 300 mW, 12 multiple wavelength lasers with 0.47 nm spacing are obtained. The generated channels have an average optical signal-to-noise ratio of 40 dB and an average peak power of −35 dBm. The proposed laser introduces the advantages of a relatively simple structure and ease of operation at any wavelength band for potential applications including optical communication systems and sensing.

Investigation and optimization of EYDFA + Raman + EYDFA hybrid optical amplifier for SD-WDM systems in C+L band

In this paper, we present a novel erbium–ytterbium doped fiber amplifier (EYDFA) + Raman + EYDFA hybrid optical amplifier (HOA) for a super-dense wavelength division multiplexing (SD-WDM) system application. The performance of the 100-channel system has been investigated for an overall data rate and channel spacing of 100[Formula: see text]Gb/s and 0.4[Formula: see text]nm, respectively, over a wavelength span of 1550–1589.9[Formula: see text]nm. HOA has been optimized for Raman length, EYDFA lengths, pump powers and Er[Formula: see text] concentrations to achieve high average gain and low gain variation ratio of 40.41[Formula: see text]dB and 0.40[Formula: see text]respectively. The optimized configuration of the proposed HOA has been compared with EYDFA + Raman and Raman + EYDFA HOA configurations. The achieved high and flat gain with an acceptable output optical signal to noise ratio (OSNR) in case of EYDFA + Raman + EYDFA HOA; makes it an optimum choice for SD-WDM systems.

Combined Temperature and Radiation Effects on the Gain of Er- and Er–Yb-Doped Fiber Amplifiers

We investigated the coupled radiation and temperature effect on the gain degradation of erbium-doped fiber amplifier (EDFA) and erbium-ytterbium-doped fiber amplifier (EYDFA). The irradiation temperatures range from -40 °C to 120 °C. Steady-state X-ray (40 keV, 300 krad (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), ~27 rad/s) experiments provide evidence for a minor coupled radiation and temperature effect on the gains of both reference and radiation-tolerant EDFA and EYDFA. This is an important result as it validates the reliance on room-temperature testing in establishing the suitability of fiber amplifiers for space applications. Furthermore, we also investigated the radiation-induced attenuation (RIA) kinetics during and after the various rare-earth-doped fiber irradiations to improve our knowledge of the basic radiation-effects mechanisms and their dependence on the temperature during irradiation. It appears that these effects also depend on the presence of cerium, a codopant that is incorporated to passivate the Al- or P-related defects and then to enhance the amplifier radiation tolerance.

A Wide Flat Triple Brillouin Frequency Spacing Multiwavelength Fiber Laser Assisted by Four Wave Mixing

In order to improve the triple frequency spacing operation, we introduce a simplified arrangement of multiwavelength Brillouin-erbium-ytterbium fiber laser that incorporates only a single amplifier source. The strong responses amongst the interacting waves in the 500 m highly nonlinear fiber help in forming wider multiwavelength bandwidth and self-flattening of the output spectra. A total of 146 Stokes lines within 3-dB span are produced with a channel spacing of 0.246 nm. These are completed when the Brillouin pump (BP) wavelength is set at 1533 nm, BP power at -12 dBm and erbium-ytterbium doped fiber amplifier at 950 mW. A quality optical signal-to-noise ratio of 46.2 dB estimation is realized along the 36 nm lasing bandwidth that starts at 1533 nm wavelength. As a result of efficient suppression of self-lasing modes, the tunability covers the entire C-band which is associated to the lowest attenuation regime. For this particular area of fiber lasers, the results confirm dramatic advancements in spectral flatness and Stokes lines count combination especially with the additional benefit of high stability at only 1.22 dB fluctuation.

Flat amplitude and wide multiwavelength Brillouin/erbium fiber laser based on Fresnel reflection in a micro-air cavity design.

In this report, we demonstrate a wide multiwavelength Brillouin-erbium fiber laser (MBEFL) with improved flatness that integrates a micro-air cavity. This air-gap introduces a cavity loss to overcome the gain saturation as well as providing efficient pump recycling scheme through Fresnel back-reflection. In addition, the efficient four-wave mixing in the highly nonlinear fiber contributes to the self-flattening of the output spectra. During operation, the optimized pumping values are set at 13 dBm Brillouin power and 600 mW erbium-ytterbium doped fiber amplifier when the air-gap length is fixed at 10 µm. A total of 180 Stokes lines are produced with a channel spacing of 0.08 nm. The flat lasing bandwith is 14 nm that consists of 1557 to 1571 nm wavelengths within 3-dB span. The average optical signal-to-noise ratio is 18 dB, having high peak power of -8 dBm. To our knowledge, this is the best result attained in MBEFLs with respect to the spectral flatness. In fact, the power stability of 0.76 dB order over 45 minute durations merits it applications in optical fiber sensing and communications.

Triple Brillouin frequency spacing multiwavelength fiber laser with double Brillouin cavities and its application in microwave signal generation

We propose and experimentally investigate a multiwavelength Brillouin fiber laser (MBFL) with triple frequency spacing by employing a modular structure. In this scheme, we obtain nine channels optimized with frequency spacing of 0.259 nm. The single, double, and triple Brillouin frequency spacing for the MBFL can be easily realized by utilizing this modular structure. The impact of Brillouin pump (BP) power, BP wavelength, and erbium-ytterbium-doped fiber amplifier (EYDFA) output power on the performance of the MBFL is investigated, respectively. We also study the generation of beating frequency microwave signals based on single, double, and triple frequency spacing MBFL. 10.5 GHz, 21.48 GHz, and 31.77 GHz microwave signals with 3 dB linewidth of 16.4 MHz, 15.2 MHz, and 12.8 MHz are generated, respectively.

Modulation instability initiated high power all-fiber supercontinuum lasers and their applications

High average power, all-fiber integrated, broadband supercontinuum (SC) sources are demonstrated. Architecture for SC generation using amplified picosecond/nanosecond laser diode (LD) pulses followed by modulation instability (MI) induced pulse breakup is presented and used to demonstrate SC sources from the mid-IR to the visible wavelengths. In addition to the simplicity in implementation, this architecture allows scaling up of the SC average power by increasing the pulse repetition rate and the corresponding pump power, while keeping the peak power, and, hence, the spectral extent approximately constant. Using this process, we demonstrate >10W in a mid-IR SC extending from ∼0.8 to 4μm, >5W in a near IR SC extending from ∼0.8 to 2.8μm, and >0.7W in a visible SC extending from ∼0.45 to 1.2μm. SC modulation capability is also demonstrated in a mid-IR SC laser with ∼3.9W in an SC extending from ∼0.8 to 4.3μm. The entire system and SC output in this case is modulated by a 500Hz square wave at 50% duty cycle without any external chopping or modulation. We also explore the use of thulium doped fiber amplifier (TDFA) stages for mid-IR SC generation. In addition to the higher pump to signal conversion efficiency demonstrated in TDFAs compared to erbium/ytterbium doped fiber amplifier (EYFA), the shifting of the SC pump from ∼1.5 to ∼2μm is pursued with an attempt to generate a longer extending SC into the mid-IR. We demonstrate ∼2.5 times higher optical conversion efficiency from pump to SC generation in wavelengths beyond 3.8μm in the TDFA versus the EYFA based SC systems. The TDFA SC spectrum extends from ∼1.9 to 4.5μm with ∼2.6W at 50% modulation with a 250 Hz square wave. A variety of applications in defense, health care and metrology are also demonstrated using the SC laser systems presented in this paper.

Experimental and theoretical studies on ytterbium sensitized erbium-doped fiber amplifier

The performance of a high power erbium–ytterbium doped fiber amplifier (EYDFA) is investigated experimentally and theoretically. The EYDFA provides a flat gain with an output power higher than 23 dBm in the wavelength region from 1541 to 1565 nm using a multimode pumping at 927 nm. In the theoretical analysis, the rate and power propagation equations are solved to examine the effect of fiber length on the bandwidth of the gain spectra. In the C-band region, the small signal gain of the EYDFA varies from 30 to 34 dB with 10 m long erbium–ytterbium doped fiber (EYDF) while the 927 nm pump power is fixed at 3.5 W. It is shown that the calculated output power is in good agreement with the experimental results, verifying the feasibility of our theoretical model. However, the experimental result shows a relatively lower gain compared to the theoretical result due to the spurious reflection in the cavity and the insertion loss of the EYDF which were neglected in our theoretical model.

High output power Erbium-Ytterbium doped cladding pumped fiber amplifier

The performance of a high output power Erbium-Ytterbium doped fiber amplifier (EYDFA) pumped by a 927 nm laser diode are proposed and experimentally investigated. The EYDFA provides a flat gain and output power higher than 23 dBm in the wavelength region from 1545 to 1566 nm using a double-pass configuration. A broadband fiber Bragg grating is used in the double-pass EYDFA to allow a double-propagation of the test signal in the gain medium and thus improves the gain and output power characteristics of the amplifier. The maximum output power of 390 mW is obtained at the maximum 927 nm pump power of 4.1 W which translates to a power conversion efficiency of about 10%.

COMPACT AND EFFICIENT Er–Yb-DOPED FIBER AMPLIFIER

A compact and efficient optical amplifier is demonstrated using an erbium–ytterbium-doped fiber amplifier (EYDFA) with a double-pass configuration. It uses only 3 m of doped fiber with 20 mW pump power. This forward-pumped amplifier achieves a maximum low signal gain of 37 dB and a corresponding noise figure of 5.5 dB. Compared with the backward-pumping double-pass EYDFA, the gain obtained is 7 dB higher, with a lower noise figure of 5.5 dB. In addition, the gain obtained in this study is 17 dB higher than that of a conventional forward-pumping single-pass amplifier, while its noise figure is only 0.5 dB higher. These results show that the forward-pumped double-pass design holds great promise in the development of practical and cost-efficient optical amplifiers which can be pumped by using LEDs or low cost laser diodes.