Thulium-doped Fiber Amplifier Research Articles

Accurate Modeling of Transverse Mode Instability in Thulium-Doped Optical Fiber Amplifiers

Accurate Modeling of Transverse Mode Instability in Thulium-Doped Optical Fiber Amplifiers

Observation of modulation instability in a coherently driven active fiber ring resonator at 2 μm wavelength.

We report the first, to our knowledge, observation of the nonlinear phenomenon known as modulation instability (MI) in a coherently driven fiber resonator pumped at 1972 nm. To compensate for the very high losses in this spectral region, we have integrated a thulium-doped fiber amplifier inside the cavity. Lower losses allow a lower MI threshold, leading to the observation of this phenomenon at a moderate input power. The results align closely with the numerical simulations of the system. Our study shows that active compensation of loss can be implemented in the 2 µm wavelength range to construct fiber ring cavities with high finesse. It paves the way to the observation of more complex nonlinear effects optical frequency comb through cavity soliton generation.

Dual-wavelength single-frequency Tm:ZBLAN fiber amplifier operating at 1.94 and 2.33 μm

We report here, to the best of our knowledge, the first dual-wavelength single-frequency thulium-doped fiber amplifier operating at 1.94 and 2.33 μm. The single-stage, Tm3+-doped ZBLAN fiber amplifier, ground-state pumped by a 793-nm laser diode, yielded a stable output power of 1.45 W at 2332 nm and 7.4 W at 1939 nm. The injection of 1.94-μm seed effectively suppresses parasitic lasing in the 2.33-μm Tm fiber amplifier. The experiment investigated the competitive relationship between the 2-μm transition and the 2.3-μm transition, and the results suggest that the injection of 1.94-μm seeds is beneficial to the improvement of 2.33-μm efficiency, while the injection of 2.33-μm seed slightly reduces the 1.94-μm efficiency.

Design, optimization, and analysis of thulium-doped optical fiber amplifiers for E-band communication

Design, optimization, and analysis of thulium-doped optical fiber amplifiers for E-band communication

Scalable narrow linewidth high power laser for barium ion optical qubits

The linewidth of a laser plays a pivotal role in ensuring the high fidelity of ion trap quantum processors and optical clocks. As quantum computing endeavors scale up in qubit number, the demand for higher laser power with ultra-narrow linewidth becomes imperative, and leveraging fiber amplifiers emerges as a promising approach to meet these requirements. This study explores the effectiveness of thulium-doped fiber amplifiers (TDFAs) as a viable solution for addressing optical qubit transitions in trapped barium ion qubits. We demonstrate that by performing high-fidelity gates on the qubit while introducing minimal intensity noise, TDFAs do not significantly broaden the linewidth of the seed lasers. We employed a Voigt fitting scheme in conjunction with a delayed self-heterodyne method to accurately measure the linewidth independently, corroborating our findings through quadrupole spectroscopy with trapped barium ions. Our results show linewidth values of 160 ± 15 Hz and 156 ± 16 Hz, respectively, using these two methods, underscoring the reliability of our measurement techniques. The slight variation within the error-bars of the two methods can be attributed to factors such as amplified spontaneous emission in the TDFA or the influence of 1/f noise within the heterodyne setup delay line. These contribute to advancing our understanding of laser linewidth control in the context of ion trap quantum computing as well as stretching the availability of narrow linewidth, high-power tunable lasers beyond the C-band.

Broadband thulium fiber amplifier for spectral region located beyond the L-band

We present the development of a pair of silica-based thulium-doped fiber amplifiers working together in a broad spectral range from 1.65 µm to 2.02 µm. For the one optimized for shorter wavelengths, we designed and prepared optical fiber with a depressed cladding. We show the performance of the amplifiers achieving small-signal gain of at least 10 dB over 350 nm range from 1670 nm to 2020 nm, maximum gain of 40.7 dB with a noise figure as low as 6.45 dB and an optical signal-to-noise ratio of up to 50 dB. To the best of our knowledge, it is the first time that thulium fiber amplifiers of straightforward design without using redundant spectral filters operating efficiently in such a wide spectral region are demonstrated.

Microresonator Brillouin laser and multi-Stokes generation at 2µm

Brillouin scattering in microresonators has emerged as the driving process for developing high-coherence lasers for applications such as coherent optical communications, optical atomic clocks, microcomb solitons, and quantum communications. However, most of the demonstrations of microresonator Brillouin lasers have been limited to a 1550 nm wavelength regime, which benefits from the development of low-loss microresonator devices on different material platforms and the availability of tunable pump lasers. The development of wide bandwidth thulium-doped fiber amplifiers and low two-photon absorption in silicon around 2µm makes this wavelength region a potential candidate for applications in future optical communications, gravitation wave sensing, and atmospheric sensing. All these applications will benefit from the development of Brillouin lasers. However, there has not been much progress on microresonator-based 2µm Brillouin lasers. Here, we present a demonstration of a 2µm microresonator Brillouin laser. We use whispering gallery mode resonances in a ∼330µm silica microsphere to demonstrate a Brillouin lasing threshold of 35 mW. We achieve generation of second- and third-order Brillouin Stokes using pump powers of ∼60mW and 104 mW, respectively. By tuning the pump laser wavelength, we demonstrate high-resolution (∼10 pm) tuning of the Brillouin laser. From the beat signal of the first- and third-order Brillouin Stokes, we estimate a Brillouin laser linewidth of ∼135kHz, which is 15 times smaller than the pump linewidth. This work may find applications in optical communications, soliton combs, and atmospheric sensing in the 2µm wavelength region. Published by the American Physical Society 2024

Power-aware high-capacity elastic optical networks

The power consumption of telecommunication equipment has been identified as a relevant contributor to global energy consumption. In fact, new-generation optical transponders employ power-intensive electronic application-specific integrated circuits (ASICs) for digital signal processing (DSP). DSP design has traditionally prioritized meeting transmission requirements over power consumption optimization. In general, the evolutions of transmission techniques and network design have always been mainly driven by traffic increase; in this context, in order to operate network resources more efficiently, margin reduction has been investigated in the past few years. Indeed, traditionally, high physical layer margins are used to ensure reliability over an extended period, resulting in overprovisioning the optical connections for both physical layer conditions and capacity. On the other hand, super-channels have emerged as a suitable solution for accommodating the continuous traffic growth. However, power consumption has not been deeply considered in the optimization of super-channel transmission. This paper first investigates the power efficiency of super-channels operated with designed and reduced margins. Low-margin operation is enabled by adapting sub-carrier spacing and filter bandwidth. Power-aware super-channel optimization is then experimentally demonstrated leveraging a 600 Gbit/s transponder in the SDN-controlled elastic optical network (EON). The results have identified a trade-off between power consumption and spectrum efficiency. Furthermore, the ongoing bandwidth demand has motivated the investigation of multi-band (MB) transmission for scaling the capacity of the existing infrastructures. However, novel networking devices (e.g., optical amplifiers operating beyond the C- and L-bands) will affect the overall power consumption. In this context, experimental power analysis of a thulium doped fiber amplifier (TDFA) is performed based on the traffic load and corresponding configuration. The results show that TDFA power consumption varies with configuration and increases with output power.

High-power, air-cooled Thulium doped fiber amplifier with 71% slope efficiency

High-power, air-cooled Thulium doped fiber amplifier with 71% slope efficiency

Stimulated brillouin scattering in double-clad thulium-doped fiber amplifier

Stimulated brillouin scattering in double-clad thulium-doped fiber amplifier

2.3-µm single-frequency Tm: ZBLAN fiber amplifier with output power of 1.41 W.

We present here the first watt-level single-frequency thulium-doped ZBLAN fiber amplifier system operating at a wavelength of 2.3 µm. Continuous-wave output of up to 1.41 W was generated from a two-stage Tm: ZBLAN fiber amplifier with direct ground-state pumping at 793 nm. Seeded by a single-frequency distributed feedback diode laser at 2332 nm, the thulium-doped ZBLAN fiber amplifier emitted a laser with linewidth no more than 10 MHz at maximal output power. This study examines the impact of a 2.3-µm seed on the competitive laser transition of 2 µm. The findings indicate that direct pumping of a Tm fiber amplifier holds the potential for achieving higher power output within the 2.3-µm band.

Gain optimization and data modeling of S-band of Tm-doped fiber amplifier based on genetic algorithm

At present, fiber amplifiers are indispensable in the field of communication, Erbium-doped fiber amplifiers (EDFA) are currently more mature fiber amplifiers, but because of electronic bottlenecks, they have approached saturation in recent years. Thus, the study and application of fiber amplifiers doped with other rare earth elements has become a new goal at present. At the same time, expanding the available bandwidth of the fiber amplifier to a higher or lower direction has also become a major task. This article discusses the gain of thulium-doped fiber amplifiers at 1400 nm – 1450 nm (S-band) and uses the genetic algorithm to optimize the fiber length and doping concentration to find the optimal solution, this article also analyzes the change in gain at different fiber lengths and doping concentrations. The results show that the fiber length is 56.2705 meters, and the doping concentration is 59.9502 ×1024 per square meter, at which the gain reaches the peak is 65.19. The results show that the thulium-doped fiber amplifier (TDFA) in this band has good amplification characteristics, and it can be meticulously studied based on this method in the future to obtain more accurate results. It can also be solved using other algorithms, such as Quantum Genetic Algorithms.

Gain maximization of thulium-doped fiber amplifiers based on genetic algorithm with 1900 nm signal

With the development of fiber communication technology, the existing operating wavelength band of fiber amplifiers, such as 1530-1560 nm and 1480-1510 nm, may not be satisfied with the growing requirement in many fields. Therefore, this research emphasizes expanding the available band (1800-2000 nm) and maximizing the gain of the thulium doped fiber amplifier at the central wavelength (1900 nm). The study is based on the two-level energy system of thulium ion, which can cover the objective wavelength. According to the related rate equations solved by the symbol function method and power propagation equations solved by the Fourth order Runge-Kutta method, use MATLAB to simulate a fiber amplifier and study the coeffect amplification effect of thulium doped fiber amplifier to 1900 nm signal light. Use the Genetic algorithm to find the best parameters match (fiber length 1m and doping concentration 3.5) when the gain reaches the maximum (27.5 dB). Through optimizing the collocation of parameters, the gain can be maximized.

Modeling and numerical simulation optimization of gain spectrum of thulium-doped broadband fiber amplifier based on cat swarm algorithm

With the development of light technology, especially the maturation of WDM/DWDM technology, the demand for optical amplification of the S-band and S+ band (1450nm~1520nm) is increasing day by day, and the energy level structure of Tm3+ has energy level transitions to meet the requirements of S-band and S+ band amplification. Although thulium ion has a very complex energy level structure, TDFA is one of the most promising optical fiber amplifiers for S and S+ bands. At the same time, with the continuous development of computer technology and mathematical theory, the optimization algorithm has been rapidly developed and widely used in recent decades, based on genetic algorithm, simulated annealing algorithm, and other traditional optimization algorithms that have been proved to get good convergence speed and optimization results. In this paper, the thulium-doped fiber amplifier's gain is optimized by using a cat swarm intelligent optimization algorithm to obtain the maximum fiber length and doping concentration.

Watt-level broadband PM Tm-doped fiber amplifier for the 1750–1910 nm window

We report broadband experimental and simulated performance of a single-clad polarization-maintaining (PM) thulium-doped fiber amplifier (TDFA) optimized for operation in the 1750–1910 nm wavelength band. With the two-stage amplifier architecture, a maximum output power of 2.4 W was obtained at 1850 nm for 7.0 W of launched pump power at 1567 nm, with a corresponding optical-to-optical efficiency of 31.4 %. The measured polarization extinction ratio (PER) was larger than 22.6 dB, and the long-term power stability exhibited a peak-to-peak variation of 2.4 %. By employing a tunable seed laser covering the 1750–1910 nm wavelength range, we measured a maximum output power level of 2.38 W with an optical signal-to-noise ratio (OSNR) greater than 53 dB/0.1 nm. Our simulations are in good agreement with the experimental data over the whole 160 nm operating spectral bandwidth.

Maximum gain optimization of thulium-doped fiber amplifier based on genetic algorithm for peak gain spectrum at 1800- 2000nm

The optical fiber amplifier doped with rare earth elements has the characteristics of high gain, high doping concentration and short length. Compared with other fiber optic systems, the fiber used is shorter, also known as lumped fiber amplifier. At present, Er, Pr, Tm, Nd and Yb doped fiber amplifiers and lasers are mainly studied more. To further extend the transmission distance, improve the transmission quality and increase the transmission capacity, it is very important for the research of fiber amplifier. In this research, using a two-level structure, we investigate the maximum of the peak gain of the gain spectrum of a thulium-doped broadband fiber amplifier in the 1800-2000 nm wavelength range. Signal gain is inversely proportional to fiber length, doping concentration, and pump power in both the absorption spectrum and the emission spectrum, as shown by the relationship diagram of signal gain with these variables. And through the genetic algorithm data optimization, we get that when the fiber length is 2.2 m, the maximum gain is 42.7 dB.

Modeling and numerical simulation optimization of output spectrum of thulium-doped broadband fiber optic light source

In this research, the performance of thulium-doped fiber lasers is analyzed and a mathematical model is established. Thulium-doped fiber amplifiers are the focus of this article. A large number of simulations have been carried out in the MATLAB simulation environment, and the main work and innovation points are as follows: firstly, the energy level structure characteristics of thulium were studied, and its spectral characteristics were analyzed. After consulting some information, 3H4 to 3H6 energy level has been selected in modeling. Secondly, use the rate equations and the power propagation equations to provide a theoretical analysis of the pumping mode of thulium-doped fiber lasers. And a mathematical model of a thulium-doped fiber laser was established. The parameters such as fiber length and doping concentration in the model are discussed. Finally, to find the appropriate parameters, the genetic optimization algorithm is used to optimize the fiber length and doping concentration, and then we can get the parameters corresponding to the maximum output power of the thulium-doped fiber amplifier.

Gain flattened S+C+L-band bidirectional thulium doped fiber/multi-section fiber optical parametric hybrid amplifier

This article demonstrates the achievement of optical amplification across the S, C, and L-bands. A hybrid amplifier is proposed that utilizes a combination of bidirectional thulium-doped fiber amplifier (TDFA) and multi-section fiber optical parametric amplifier. With careful selection of TDFA and parametric amplifier parameters, gain can be achieved over complementary bandwidth regions. Resultantly, better gain flatness is achieved over the whole effective bandwidth of 170 nm. The amplifier being proposed is evaluated for a system consisting of 18 wavelength division multiplexed channels, each with a capacity of 100 Gb/s, and a channel spacing of 10 nm. By setting the input power per channel to an optimal value of –30 dBm, the parameters are adjusted to attain a flat gain exceeding 23.52 dB, accompanied by a gain ripple of only 2.09 dB. These parameters are optimized over a wavelength range between 1460 nm and 1630 nm.

Demonstration of the First Outdoor 2-μm-Band Real-Time Video Transmission Free-Space Optical Communication System Using a Self-Designed Single-Frequency Fiber Laser

In the present paper, we demonstrate the first outdoor free-space optical communication (FSOC) system with real-time video transmission in a 2-μm-band with a state-of-the-art data rate performance of 10 Gbit/s and a communication distance of ∼177 m. The measured wide-open eye diagram and zero bit-error-rate also validated the high communication quality. The FSOC system is constructed with all homemade components, including a single-frequency (SF) thulium-holmium co-doped fiber laser (THDFL), a modulation module, a demodulation module, three thulium-doped fiber amplifiers, an optical bandpass filter, two optical-antennas, and a display system. As the most important component, the SF THDFL, enabled by a uniform fiber Bragg grating and a passive fiber ring-compound cavity, is self-designed and fabricated by our group, presenting high lasing stability centered at 2048.98 nm, an optical signal-to-noise ratio of >81 dB, a relative intensity noise of <-128.18 dB/Hz at >0.5 MHz and a linewidth of 5.290 kHz under a measurement integration time of 0.001 s. Our work is an important step forward for practical outdoor FSOC in a 2-μm-band, proving useful for engineers and scientists when our SF THDFL is implemented as a low-cost, high-performance laser source for the FSOC system.

Design of an efficient thulium-doped fiber amplifier for dual-hop earth to satellite optical wireless links

Optical wireless communication (OWC) links enable high-speed data transmission between earth stations and satellites. The propagation of optical signals through the atmosphere suffer from atmospheric attenuation and turbulence due to rain, fog, snow, clouds, and wind. The impact of these impairments on propagation of optical signals becomes more pronounced in the case of deep space links. Therefore, optical amplifiers of high output power and gain are extremely useful in deep space links to achieve error free transmission by improving the link budget. In this paper, we propose the design of an efficient Thulium-doped fiber amplifier (TDFA) as booster as well as an in-line based on dual-stage pumping scheme for employment in a dual-hop earth to satellite OWC Link. The pumping scheme, length of Thulium-doped fiber (TDF), and Tm 3+ concentration in the proposed design of TDFA are optimized in such a way so that high output power and gain are achieved for booster and in-line stages, respectively. Output power and gain of 4.6 W and 18.8 dB, respectively are achieved for signal power of 0 dBm at 1807.143 nm when TDFA is used as booster amplifier. Similarly, gain and output power of 66.6 dB and 1.5 W, respectively are achieved for signal power of −35 dBm at 1807.143 nm when TDFA is used as in-line amplifier. A noise figure (NF) of 4.4 dB is achieved for signal wavelength of 1807.143 nm and power of 0 dBm. Finally, the system level performance of the designed TDFA is investigated using bit error rate (BER) metric for a dual-hop earth to satellite OWC wavelength division multiplexed (WDM) transmission system of four quadrature phase shift keying (QPSK) modulated optical signals with an aggregate data rate of 104 Gbps. The BER results showed different possible ranges of error-free transmission at the forward error correction (FEC) limit of 10 - 4 for different values of atmospheric attenuation.