Multi-wavelength Pumping Research Articles

ОСОБЛИВОСТІ МОДЕЛЮВАННЯ ВКР ПІДСИЛЮВАЧА НА ОСНОВІ ВОЛОКНА З КОМПЕНСОВАНОЮ ДИСПЕРСІЄЮ З РІВНОМІРНОЮ СМУГОЮ ПІДСИЛЕННЯ У C+L ТЕЛЕКОМУНІКАЦІЙНИХ ВІКНАХ

The results of the modeling of a broadband optical fiber Raman amplifier (FRA) with a multi-wavelength pumping and a uniform gain band covering C+L telecommunication windows in an active fiber with compensation of dispersion type DCF are presented. It has been demonstrated that the SRS gain profile, that is, the distribution of the optical radiation gain over the frequency range of the Stokes shift in Raman scattering, is the main characteristic of the FRA. Optimum values of the parameters of the pump sources are presented, namely spectral distribution of wavelengths and relative power of all pump sources, at which it is possible to obtain a minimum non-uniformity of the gain band. Based on the results of the calculations, a minimum non-uniformity of the SRS gain profile on almost the whole operating range was obtained for 6 pumping sources. It is shown that the analytical form of the gain profile greatly simplifies the procedure of modeling of the main gain parameters for FRA with multi-wavelength pumping for 3-6 wavelengths of pump sources. Furthermore, the proposed simplified analytical model makes it possible to quickly obtain theoretical estimates of the main parameters of the operating wavelength band of FRA with an arbitrary number of pumping lasers in the multiwave pump source.

Simulations of multiwavelength cladding pumping of high-power fiber Raman amplifiers

We numerically simulate and optimize a high-power fiber Raman amplifier cladding pumped by spectrally combined diode lasers at wavelengths from ∼0.9 to ∼1 μm in the continuous-wave regime. This amplified a signal at the first-Stokes wavelength of 1024 nm. We found that it was possible to add pumps over an increasingly wide wavelength span up to ∼90 nm, while still maintaining an incremental conversion efficiency higher than 60%, even though the Raman linewidth is only ∼15 nm. We investigated the dependence on the power of individual diode lasers and on the wavelength spacing and found that the total conversion efficiency reaches ∼70 % with realistic pump sources based on state-of-the-art diode lasers. We believe this study shows the potential for high-power fiber Raman lasers pumped by spectrally combined multiwavelength diode and fiber laser sources.

Comprehensive Theoretical Study of Mode Instability in High-Power Fiber Lasers by Employing a Universal Model and Its Implications

We present comprehensive theoretical study of mode instability with a universal model for the first time, which includes quantitative study on the various influence factors and mitigation methods. With large numerical results, the influence of various fiber and system parameters has been studied to summarize mitigation methods. The mode instability threshold behavior of multiwavelength pumping configurations has been studied for the first time, and the influence of pump wavelength shifting in the tandem pumping technique and amplitude modulation have also been given for the first time. The mitigation methods are discussed with review of the latest development in experimental results. The drawbacks and possible overcome measures are also discussed. By properly combining the mitigation methods, an approach to achieve beyond 10-kW diode pumped fiber laser with near diffraction limited beam quality has been proposed, which provides a creative way to overcome the mode instability limitation on diode pumped fiber lasers, and demonstrates the effectiveness of the mitigation methods.

Performance optimization of hybrid optical amplifier for dense wavelength division multiplexed system

Today’s high capacity dense wavelength division multiplexed (DWDM) systems required the flattened gain spectra with large gain bandwidth. This required properly broadening the gain bandwidth of the optical amplifiers with proper amplification of the signals. In order to achieve this, a competent flat gain hybrid optical amplifier is demonstrated that comprised of a erbium doped fiber amplifier (EDFA) and Raman amplifier with multi-wavelength backward pumping scheme. Attempts were done in order to design a (E-R) hybrid optical amplifier (HOA) for 16 channels, 20 Gbps DWDM systems at reduced channel spacing of 0.2 nm and also compared with conventional amplifiers. The performance of the system is evaluated on the behalf of different parameters viz. gain, noise figure, output power, Optical Signal to Noise Ratio (OSNR). Numerous parameters of EDFA and Raman amplifiers are optimize to find the gain spectrum of E-R HOA. It is found that E-R HOA provides better gain uniformity with noise figure less than 5 dB. It is also found that for wavelength range 1553.13–1556.15 nm, a uniform gain of 38.85 dB is achieved for input power of “0” dB with noise figure variation of 0.29 dB without using any gain flattering scheme. The output power and OSNR of all the channels is measured at 0 dBm input power and found maximum power and SNR at 1556.15 nm channel frequency is 26.44 dBm and 40.71 dB respectively.

Broadband silica-based thulium doped fiber amplifier employing multi-wavelength pumping.

A multi-wavelength pumped thulium doped fiber amplifier is investigated to extend the spectral gain coverage of the amplifier in the 1.7-1.9μm wavelength range. Through the use of a combination of 791 nm, 1240 nm, and 1560 nm laser diode pumping, the amplifier gain can be improved significantly and overall gain bandwidth enhancement of ~47% as compared to single-wavelength pumping achieved. A nominal gain of 15 dB is achieved over a bandwidth of more than 250 nm spanning from 1700 to 1950 nm with a maximum gain of 29 dB and a noise figure of less than 5 dB.

Design and Performance Analysis of Raman Amplified XG-PON System

This paper describes the design considerations and performance analysis for an XG-PON Raman amplification scheme. The experimental results and theoretical calculations presented in this paper demonstrate the feasibility of Raman amplification in O-band access systems; thus, enhancing the performance of existing access installations while still preserving the passive nature of these networks. With the availability of cost-effective quantum dot laser diodes as high-power pumps, Raman amplification is proving to be an attractive candidate for access applications. We experimentally demonstrate that it is possible to achieve a total pump power of 759 mW using polarization multiplexed quantum dot laser diodes (QD-LDs), and using a backward pumping scheme we can support a purely passive XG-PON system with 50 km reach and 64 splits. With system level numerical simulations, we illustrate the use of forward or bi-directional pumping scheme to increase the splits further. We also confirm that the Raman pump output in the experiments, despite being below the single mode cut off for the standard SMF, was efficiently coupled into the trunk fibre using off-the-shelf components. We also show using numerical simulations that a flat gain spectrum can be obtained with less than 0.7 dB gain variation across the XG-PON upstream wavelength band (1260–1280 nm) using a multi-wavelength pumping scheme with just two pump wavelengths. From a detailed system analysis, we discuss the impact of broadband filtering (20 nm) at the receiver adopted by the XG-PON standards, and show that lower class (N1) receivers can be adopted for Raman gains higher than 16 dB.

Ultrabroad supercontinuum generation in tellurite equiangular spiral photonic crystal fiber

Simulations are presented of a very broad and flat supercontinuum (SC) in both the normal and anomalous group velocity dispersion regimes of the same equiangular spiral photonic crystal fiber at low pumping powers. For a pump wavelength at 1557 nm and average pump power of 11.2 mW, we obtained a bandwidth >3 μm (970 nm–4100 nm) at 40 dB below the peak spectral power with fiber dispersion ∼2.1 ps/km nm at 1557 nm. In the same fiber, at pump wavelength 1930 nm and average pump power of 12 mW the SC bandwidth was more than two octaves (1300 nm–3700 nm) and dispersion was ∼1.3 ps/km nm at 1930 nm. This demonstrates the potential use of the fiber for multi-wavelength pumping with commercially available sources at fairly low power.

Polarization and dispersion properties of elliptical hole golden spiral photonic crystal fiber

An elliptical air-hole golden spiral photonic crystal fiber (EGS-PCF) is analyzed with the full-vectorial finite element method. The air-holes in the EGS-PCF are arranged in a spiral pattern governed by the Golden Ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The EGS-PCF exhibits extremely high birefringence (∼0.022 at operating wavelength 1550 nm) which is particularly useful for generating a polarization stable supercontinuum (SC). The fiber can also be designed to have a Zero Dispersion Wavelength (ZDW) at a suitable wavelength for only one polarization and large negative dispersion for the other, leading to a single-polarization SC. In addition, the fiber dispersion can be designed to obtain ZDWs at 800 nm and 1064 nm simultaneously, which can facilitate broadband supercontinuum generation (SCG) through multi-wavelength pumping.

Broadband Wavelength-swept Raman Laser for Fourier-domain Mode Locked Swept-source OCT

A novel broadband wavelength-swept Raman laser was used to implement Fourier-domain mode locked (FDML) swept-source optical coherence tomography (SS-OCT). Instead of a conventional semiconductor optical amplifier, this study used broadband optical fiber Raman amplification, over 50 nm centered around 1545 nm, using a multi-wavelength optical pumping scheme, which was implemented with the four laser diodes at the center wavelengths of 1425, 1435, 1455 and 1465 nm, respectively, and the maximum operating power of 150 mW each. The operating swept frequency of the laser was determined to 16.7 kHz from the FDML condition of 12 km optical fiber in the ring cavity. The OCT images were obtained using the novel broadband wavelengthswept Raman laser source.

General and effective dynamic gain spectrum control of broadband raman amplifiers with multi-wavelength pumping

An effective feedback algorithm is proposed to dynamically control the gain spectra of multi-wavelength pumped broadband Raman amplifiers. Based on Raman coupling power equations, a simple saturation factor is introduced to achieve the adjusting matrix. By using this method, efficient pump adjustment can be carried out to accomplish wide-range dynamic gain spectrum control (larger than 22dB dynamic range) as well as automatic gain clamping even for 90nm bandwidth, highly-saturated RAs. Moreover, this algorithm can be well applied to different fiber types as well as pumping schemes. Some useful guidelines are also demonstrated.

Supercontinuum generation using continuous-wave multiwavelength pumping and dispersion management

We experimentally demonstrate that continuous-wave supercontinuum generation in optical fibers can be significantly enhanced by using both multiwavelength pumping and dispersion management. We show by detailed spectral analysis that continuum enhancement is achieved mainly through a combination of Raman-assisted modulation instabilities, soliton compression, and dispersive wave generation. With this technique, an 800 nm wide (from 1.2 to 2.0 microm) 2 W supercontinuum source is reported that uses a three-wavelength pump and a dispersion-tailored four-optical fibers arrangement.

Automatic gain control in Raman amplifier with multi-wavelength pumps

Automatic gain control method in Raman amplifier with multi-wavelength pumping scheme is presented. Monitoring of several channel power and feedback pump control is used in the gain control method. The condition to minimize the gain deviation is investigated by numerical simulation. Two monitoring channels are necessary to confine gain deviation in ±0.2dB at two pumps C-band Raman amplifier. In the experiment, gain deviation of 1.5dB is controlled to 0.2dB at 38/40 channels drop, and fast suppression of transient gain excursion is achieved.

Spectroscopic Analysis of Gain Bandwidth in Raman Amplifier with Multiwavelength Pumping Scheme Using Actual Band Model

The spectroscopic model is proposed to analyze the gain bandwidth of a fiber Raman amplifier (FRA) with a multiple wavelength pumping scheme based on Raman gain theory. The oscillatory lineshape, which is the analytic function to analyze Raman gain spectra, allows us to estimate the gain bandwidth of the FRA. Based on the proposed theoretical modeling, we design and analyze the characteristics of the FRA using the combined multiwavelength pumping sources. We achieved the extended gain bandwidth of the FRA over 80 nm with the small gain ripple less than 0.5 dB. Threshold pumping power and effective noise figure for the FRA can be also analyzed by using the proposed model, which is also applicable for versatile fibers with other doping materials. The proposed analysis method can be useful for the design of FRA with the multiwavelength pumping scheme.

White-light supercontinuum generation in normally dispersive optical fiber using original multi-wavelength pumping system

We report on the experimental demonstration of a white-light supercontinuum generation in normally dispersive singlemode air-silica microstructured fiber. We demonstrate that the simultaneous excitation of the microstuctured fiber in its normal and anomalous dispersion regimes using the fundamental and second harmonic signals of a passively Q-switched microchip laser leads to a homogeneous supercontinuum in the visible range. This pumping scheme allows the suppression of the cascaded Raman effect predominance in favor of an efficient spectrum broadening induced by parametric phenomena. A flat supercontinuum extended from 400 to 700 nm is achieved.

Experiments on long-haul broadband WDM transmissionwith Ramanamplification

It is experimentally confirmed that Raman amplification with multi-wavelength pumping sources enables the pass bandwidth to be expanded to 33 nm even over transoceanic distances. It is also shown that the transmission performance of Raman amplifiers, which is dominated by not only OSNR but nonlinear effects, is superior to that of EDFAs.