Erbium-ytterbium Doped Fiber 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.

High power passively mode-locked laser with Sb2Te3 deposited tapered fiber in Er/Yb doped fiber laser

Antimony telluride (Sb2Te3), one of the materials from the topological insulator (TI) family, was studied as a saturable absorber (SA) for producing high-power ultrafast lasers in the C-band region. In order to achieve a mode-locked operation, a tapered fiber with a tapered waist of 6 μm was coated with Sb2Te3 to provide the interaction of the evanescent field with the material. Non-linear optical properties of the constructed SA include a 4.05 % modulation depth and a saturation intensity of 0.35 MW/cm2. Mode-locked pulses were generated when the SA was placed inside the cavity. The mode-locked pulses were solitonic, having a center wavelength of 1561.5 nm and a pulse duration of 1.8 ps at a pump power of 461 mW. The fundamental frequency measured was 18 MHz within pump power ranging from 461 mW to 657 mW. The maximum average output power, pulse energy, and peak power obtained from the generated mode-locked pulses were 269 mW, 14.9 nJ, and 8.3 kW, respectively. The measured signal to noise (SNR) of 55 dB indicates the excellent stability of the mode-locked pulses. This is the first demonstration of mode-locked pulses utilizing Sb2Te3 coated tapered fiber as an SA in a double-clad erbium-ytterbium doped fiber (DC-EYDF) laser cavity that we are aware of.

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.

Multiple mode-locked regimes of an Er/Yb double-clad fiber laser based on NPR

In this paper, we experimentally demonstrate generation of diverse structures of robust optical pulses obtained with a ring cavity passively mode-locked fiber laser based on a double-clad erbium-ytterbium doped fiber, and operating at net-anomalous cavity dispersion. A half-wave and a quarter-wave retarder plates allow adjustable saturable absorbing action by the nonlinear polarization rotation technique. Pulsed laser operation in quasi- continuous wave, molecules of solitons, and single-wavelength noise-like pulses (NLPs) regimes is obtained by properly adjusting the wave retarders. In the soliton and NLPs operating regimes, the central laser wavelength lies in the 1540 nm region. The obtained NLPs exhibit narrow peak coherence of ∼231 fs.

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.

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.

Broadband amplification of high power 40 Gb/s channels using multimode Er-Yb doped fiber

Broadband amplification of several high power communication channels is demonstrated using a multimode Erbium-Ytterbium doped fiber (EYDF) amplifier. The multimode feature of this amplifier aims at simultaneously enabling wide gain bandwidth and high output power. The amplifier provides a gain bandwidth spanning over the 1535.0 nm-1565.8 nm band. The amplifier also provides a high output power of >30.2 dBm, with ± 2.4 dB natural gain flatness over the bandwidth of interest. The performance of the amplifier is assessed in a 40 Gb/s WDM system, featuring no trace of modal dispersion in the eye diagram and a low power penalty (< 0.4 dB) on the bit error ratio (BER).

SINGLE MODE ERBIUM YTTERBIUM-DOPED FIBER LASER WITH MULTIMODE PUMPING

An efficient and stable laser action from a double-clad erbium/ytterbium-doped fiber (EYDF) is demonstrated using a fiber Bragg grating at room temperature. The fiber laser operates at wavelength of 1552.3 nm with a slope efficiency of 38% when pumped by multi-mode 915 nm laser diodes. However, the slope efficiency is higher in the EYDF laser configured with double-sided output due to the high splicing loss between the multi-mode combiner and double-clad EYDF. The laser also has a spectral bandwidth of 0.2 nm and signal to noise ratio of more than 25 dB. The threshold power to achieve lasing is measured to be approximately 500 mW for this laser.

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.