Praseodymium-doped Fluoride Fiber Research Articles

Compact and efficient O-band bismuth-doped phosphosilicate fiber amplifier for fiber-optic communications

During last decades there has been considerable interest in developing a fiber amplifier for the 1.3-upmu m spectral region that is comparable in performance to the Er-doped fiber amplifier operating near 1.55 upmu m. It is due to the fact that most of the existing fiber-optic communication systems that dominate terrestrial networks could be used for the data transmission in O-band (1260–1360 nm), where dispersion compensation is not required, providing a low-cost increase of the capacity. In this regard, significant efforts of the research laboratories were initially directed towards the study of the praseodymium-doped fluoride fiber amplifier having high gain and output powers at the desired wavelengths. However, despite the fact that this type of amplifiers had rapidly appeared as a commercial amplifier prototype it did not receive widespread demand in the telecom industry because of its low efficiency. It stimulated the search of novel optical materials for this purpose. About 10 years ago, a new type of bismuth-doped active fibers was developed, which turned out to be a promising medium for amplification at 1.3 upmu m. Here, we report on the development of a compact and efficient 20-dB (achieved for signal powers between -40 and -10 dBm) bismuth-doped fiber amplifier for a wavelength region of 1300–1350 nm in the forward, backward and bi-directional configurations, which can be pumped by a commercially available laser diode at 1230 nm with an output power of 250 mW. The compactness of the tested amplifier was provided by using a depressed cladding active fiber with low bending loss, which was coiled on a reel with a radius of 1.5 cm. We studied the gain and noise figure characteristics at different pump and signal powers. A record gain coefficient of 0.18 dB/mW (at the pump-to-signal power conversion efficiency of above 27%) has been achieved.

Optically Modulated Tunable O-Band Praseodymium-Doped Fluoride Fiber Laser Utilizing Multi-Walled Carbon Nanotube Saturable Absorber**Supported by the Ministry of Higher Education of Malaysia under Grant Nos LRGS(2015)/NGOD/UM/KPT and GA 010-2014 (ULUNG), and the University of Malaya under Grant Nos RU 013-2018 and HiCoE Funding Phase 2.

A tunable and optically modulated fiber laser utilizing a multi-walled carbon nanotube based saturable absorber is demonstrated for operation in the O-band region. A praseodymium-doped fluoride fiber is used as the gain medium and the system is capable of generating modulated outputs at 1300 nm. Pulsed output is observed at pump powers of 511 mW and above, with repetition rates and pulse widths that can be tuned from 41 kHz and 3.4 μs to 48 kHz and 2.4 μs, respectively, at the maximum pump power available. A maximum average output power of 100 μW with a corresponding single pulse energy of 2.1 nJ is measured, while the tunability of the proposed laser is from 1290 nm to 1308 nm. The output is stable, with peak power fluctuations of ∼4 dB from the average value.

Generation of sub-nanosecond pulse in dual-wavelength praseodymium fluoride fibre laser

In this paper, we demonstrate a stable dual-wavelength pulsed output from a praseodymium doped fluoride fiber laser. These dual functions are induced by intensity-dependent transmission and loss due to the cavity birefringence. The two lasing wavelengths centered at 1298.26 nm and 1299.91 nm with a spacing of 1.65 nm and a 3 dB bandwidth of 0.11 nm and 0.13 nm respectively are obtained. The pulse width induced by the dual-wavelength laser falls within the picosecond region, with a repetition rate of 389 KHz and a maximum average pulse energy of 5.4 nJ.

Dissipative soliton resonance in a passively mode-locked praseodymium fiber laser

Dissipative soliton resonance (DSR) operation in a passively mode-locked praseodymium-doped fluoride fiber laser with a nonlinear optical loop mirror is proposed and demonstrated. A praseodymium-doped fluoride fiber is employed as the gain medium to allow lasing in the 1.3 μm region, and a stable square pulse emission at 1303 nm is observed. The width of the square pulse broadens with the increment of pump power, from 83 ns to 239 ns, whereas the peak power remains at a comparable level. The highest single pulse energy is recorded at around 2.3 nJ without the appearance of pulse breaking, validating the predicted DSR operation. To the best of author’s knowledge, this work is the first study of DSR operation in the 1.3 μm region.

All-fiber, wavelength-tunable ultrafast praseodymium fiber laser

The interest in tunable ultrafast fiber lasers operating in the 1.3 µm region has seen a significant increase due to rising demands for bandwidth as well as the zero-dispersion characteristic of silica fibers in this wavelength region. In this work, a tunable mode-locked praseodymium-doped fluoride fiber (PDFF) laser using single-walled carbon nanotubes as a saturable absorber is demonstrated. The mode-locked pulses are generated at a central wavelength of 1302 nm with a pulse repetition rate of 5.92 MHz and pulse width of 1.13 ps. The tunability of the mode-locked PDFF laser covers a tuning range of 11 nm.

Multi-wavelength Praseodymium fiber laser using stimulated Brillouin scattering

A multi-wavelength Brillouin Praseodymium fiber laser (MWBPFL) operating at 1300 nm region is demonstrated based on the hybrid scheme by utilizing Brillouin gain medium and Praseodymium-doped fluoride fiber as linear gain medium. A 15 µm air gap is incorporated into the cavity to allow the switching of Brillouin frequency spacing from double to single spacing. Under the Brillouin pump of 8 dBm and the 1020 nm pump power of 567.2 mW, 36 Stokes lines with a wavelength spacing of 0.16 nm and 24 Stokes lines with a wavelength spacing of 0.08 nm are achieved. The wavelength tunability of 8 nm is realized for both MWBPFLs by shifting the Brillouin pump wavelength. The MWBPFLs exhibit an excellent stability in the number of generated Stokes and power level over one-hour period.

Passively Q‐switched O‐band praseodymium doped fluoride fibre laser with PVA/graphene based SA

A 1.3 μm Q-switched fibre laser using a praseodymium doped fluoride fibre and a polyvinyl alcohol (PVA)/graphene based saturable absorber (SA) is proposed and demonstrated. Stable Q-switched outputs are obtained over a pumping range between 472.4 and 567.2 mW at 1.02 μm. A pulse repetition rate and pulse width of 34.86 kHz and 3.50 μs, respectively, is obtained at a maximum pump power of 567.2 mW along with an average output power of 25 µW and output energy of 0.73 nJ. The Q-switched pulses have a 1.8 nm full width at half maximum and 32 dB signal-to-noise ratio.

Holmium, praseodymium-doped fluoride fiber laser operating near 2.87 /spl mu/m and pumped with a Nd:YAG laser

The operation of a single-clad Ho/sup 3+/, Pr/sup 3+/-fluoride [zirconium, barium, lanthanum, aluminum, and sodium (ZBLAN)] fiber laser pumped by an Nd: yttrium-aluminum-garnet (YAG) solid-state laser operating at 1064 nm has been demonstrated. An output power of more than 600 mW was generated at a slope efficiency of 9% after a threshold of /spl sim/ 200 mW was reached. The center wavelength was 2854 nm for low-launched powers of < 2 W and was shifted to 2874 nm for higher launched pump powers. Excitation is predominantly into the Ho/sup 3+/ (/sup 5/I/sub 6/) level, with the Pr/sup 3+/ acting to deplete the Ho/sup 3+/ lower laser level. The relatively small slope efficiency and low output power is attributed to the small absorption coefficient of Ho/sup 3+/ at 1064 nm, as well as to the additional loss that was caused by excited-state absorptions (ESAs) at the pump wavelength from both Ho/sup 3+/ and Pr/sup 3+/ ions.

Experimental investigation of gain transients in praseodymium-doped fluoride fiber amplifiers

We experimentally analyze power excursions on a surviving data channel due to praseodymium-doped fluoride fiber amplifier (PDFFA) gain transients. These transients are a result of the equivalent time-varying power for adding or dropping up to 15 wavelength division multiplexed (WDM) signals from a 16-channel WDM system at 1310 nm. We find that power excursions for the surviving 10-Gbit/s data channel increase with an increase in the number of channels added or dropped from the system. Bit error rate (BER) measurements on the surviving channel indicate that a power penalty of up to 3.5 dB as compared to the steady-state condition results from a 15-channel add-drop event. These results provide indication of the applicability of PDFFA amplification to dynamic reconfigurable optical networks in future DWDM systems that incorporate wavelengths in the 1310-nm region.

Gain Characterization of All-Optical Gain-Clamped PDFFA for WDM Networks Using the Feedback Theory

Using feedback theory, we analyze the gain of an all-optical gain-clamped praseodymium-doped fluoride fiber amplifier (AOGC PDFFA) for eight-channel multiwavelength operation. We demonstrate by numerical simulation that gain stabilization is achieved when the open-loop gain is higher than the feedback path attenuation. If this condition is fulfilled, the gain stabilizes to a value equal to the feedback path attenuation and is not influenced by the pump power, input signal power, number of channels, doped fiber length, or any other doped fiber parameter. In our setup the AOGC PDFFA noise figure is 0.12 dB lower than the open-loop PDFFA noise figure.

Gain Stabilization in All-Optical Gain-Clamped Cascade of Praseodymium-Doped Fluoride Fiber Amplifiers

The authors present theoretical results of an analysis of an all-optical gain-clamped (AOGC) praseodymium-doped fluoride fiber amplifier (PDFFA) for protecting surviving channels in an amplified wavelength division multiplexed (WDM) network with six cascaded PDFFAs. The theoretical analysis is based on application of a large-signal numerical model that takes into account propagation of pump, signal, and downstream and upstream amplified spontaneous emission and includes time variation effects in a four-level laser system. It is shown that power excursions caused in an eight-channel WDM network by loss addition of six channels could be lower than 1 dB and free of relaxation oscillations if the AOGC PDFFA is strongly inverted and the total loss of the ring resonator is appropriately set.

Development of an efficient praseodymium-doped fiber amplifier

This paper describes the development of an efficient praseodymium-doped fluoride fiber amplifier (PDFA) using newly developed PbF/sub 2/-InF/sub 3/-based fluoride single-mode fiber. First, the spectroscopic properties of Pr/sup 3+/ in PbF/sub 2/-InF/sub 3/-based and ZrF/sub 4/-based fluoride glass are compared and then the fabrication of high-NA PbF/sub 2/-InF/sub 3/-based fluoride single-mode fiber is presented. The gain coefficients obtained with the developed fiber are 0.36 dB/mW with a forward pumping scheme and 0.4 dB/mW with a bidirectional pumping scheme. We use this newly developed fiber to construct two types of an efficient PDFA module. We realized a 19-in rack size PDFA module with a master oscillator/power amplifier laser diode (MOPA-LD) and a plug-in type PDFA module with a wavelength-stabilized 1.017-/spl mu/m LD and describe their amplification characteristics.

Analysis of a tunable -doped fluoride fibre ring laser

The output power and tuning range of a praseodymium-doped fluoride fibre ring laser are investigated using a comprehensive large-signal numerical model. The four-level laser model incorporates the mode radial field distribution in a step-index single-mode fibre and experimentally obtained emission and absorption cross sections. It has been found that the ring laser could be tuned in the range from 1265 to and the slope efficiency could reach 37.5%. The model has also been used to optimize the waveguiding parameters of a step-index -doped fluoride fibre for maximum output power.

Modelling of the temporal response of -doped fluoride fibre amplifiers

This paper presents a theoretical modelling and a numerical evaluation of the performance in the kHz regime of a typical praseodymium-doped fluoride fibre amplifier. The transient response of the amplifier is studied and amplifier characteristics such as saturation-induced second- and third-order distortion and interchannel interference, which become important in real telecommunication systems, are analysed in detail for amplitude-modulated signals.

Advanced materials for fibre and waveguide amplifiers

Recent research into optical fibre and waveguide amplifiers has been characterized by steady progress. Advances in the lowest fibre loss 1.5 μm telecommunications window, where newly installed optical networks operate, include erbium-doped materials with flatter gain spectra and planar amplifiers in a broad range of materials including oxide glasses, dielectric crystals and semiconductors. At 1.3 μm, substantial improvements have been made in praseodymium-doped fluoride fibre amplifiers and chalcogenide glasses have shown promise for enhanced gain efficiency.

Upconversion mechanisms of a praseodymium-doped fluoride fibre amplifier

We develop a simple method leading to the determination of important parameters for the praseodymium-doped fluoride fibre amplifier (PDFFA), such as the non-radiative energy transfer upconversion coefficient or pump-excited state absorption cross section . We apply this method to five ZBLAN bulks of different concentration (from 10 000 down to 500 wt ppm) and to a ZBLAN: 500 wt ppm single-mode fibre. The resulting non-radiative energy transfer upconversion coefficients are at 500 wt ppm and at 1000 wt ppm. When the pump wavelength is set at 1017 nm, is very weak: less than . We measured that the population varies according to the pump power raised to the power 2.7. We conclude that the upconversion mechanism leading to the excitation of states in the PDFFA is different from all that which has been previously suggested and we propose a three-photon process. The application of our method requires the measurement of radiative emission branching ratios from levels and that we compare to the values calculated with the Judd - Ofelt analysis. We show that this analysis has to be used very cautiously with ions. Finally, we discuss the distribution of ions in ZBLAN glass. The fitting of fluorescence decay curves from level with the Inokuti-Hirayama model shows that the distribution of ions in ZBLAN is nearly homogeneous and no clustering effects are detected. Nevertheless, the non-exponential fluorescence decay curve of level even at very low concentrations is explained by the fact that the ions do not all have exactly the same environment in the glass.

Subpicosecond pulse generation from a 1.3 [micro sign]m DFB laser gain-switched at 1 GHz

Pulses from a 1.3 µm gain-switched DFB laser are amplified using a praseodymium doped fluoride fibre amplifier, and then compressed to as short as 240 fs using higher-order soliton compression. Techniques for pedestal minimisation are investigated.

Transmission of 5 ps solitons at 1.32 [micro sign]m over 50 km of standard fibre using praseodymium doped fluoride fibre amplifiers

The authors report the amplification of 5 ps duration pulses from a gain-switched 1.32 µm DFB laser using a praseodymium doped fluoride fibre amplifier, and their subsequent soliton transmission over 50 km of standard telecommunications fibre.

Crosstalk in 1.3 μm praseodymium fluoride fiber amplifiers

Praseodymium-doped fluoride fiber amplifiers have been demonstrated to provide good gain, output power, and noise performance in the second telecommunications window. This paper presents a study of the crosstalk performance of these amplifiers. A theoretical analysis is presented from which a numerical model is developed and is used to predict the crosstalk performance of a typical amplifier. Experimental results, using two separate signals within the gain band, show good agreement between measurement and theory, indicating that it is unlikely that crosstalk will present a problem in anticipated amplifier applications. From the measured crosstalk, an upper limit is placed on the lower level lifetime, indicating that the population of this level will have a negligible effect amplifier gain. A novel technique for measuring the upper state lifetime in an amplifier, based on pump power dependence of crosstalk, is described and experimental results which are in agreement with fluorescent decay are presented.

Second Window Optical Amplifiers: Comparison of Different Pumping Wavelengths and Fibers

Praseodymium-doped fluoride fiber amplifiers at 1300 nm with different configurations and pumping sources have been developed. Performances obtained with various pumping wavelengths and active fibers are compared. The best results obtained with pumping at 1047 nm are 32.4 dB internal gain and 13.4 dBm saturation power.