Fiber Optical Parametric Amplifier Research Articles

Online digital compensation of pump dithering induced phase and amplitude distortions in transmission links with cascaded fibre-optical parametric amplifiers

We present an advanced online digital signal processing (DSP) method for correcting the phase and amplitude distortions caused by the phase modulation of the pump source and its interaction with the dispersive fibre channel in transmission systems using cascaded fibre-optical parametric amplifiers. The proposed algorithm is numerically demonstrated to achieve significant (up to 3.7 dB for a four-tone pump-phase modulation scheme) Q2-factor performance improvement over conventional DSP in 16 quadrature-amplitude modulation signal transmission.

Comparative study of single pump all optical fiber amplifiers (POAs) with ultra wide band and high gain fiber optic parametric amplifiers in highly nonlinear fibers

Abstract This paper has clarified comparative study of single pump all optical fiber amplifiers with ultrawide band and high gain fiber optic parametric amplifiers in highly nonlinear fibers. Different amplifiers gain is demonstrated versus system distance for different light amplifiers in highly nonlinear fiber channel. As well as amplifier gain is clarified against system distance for different light amplifiers in DCF, DSF and NZDSF fiber channel. The mechanism of generation of single idler signal is studied based on single signal and pump signal. Moreover the mechanism of generation of single idler signal is analyzed and investigated clearly based on signal and two pump signals. Amplifier bandwidth is demonstrated against system distance for different fiber channel types in the presence of POA amplifiers based on 100 mW, 300 mW and 500 mW pumping power. The map of the signal losses is discussed and clarified versus wavelength band in the presence of all amplification techniques. Light signal per noise ratio and bit error rates are demonstrated against system distance for different fiber channel types in the presence of POA amplifiers based on 100 mW, 300 mW and 500 mW pumping power. POA is more suitable for the operation in HNLF fiber channel in compared to other proposed fiber communication channels. All optical amplifiers operation performance gain efficiency is compared together in different fiber channel media. The system can be employed with POAs for the fiber reach up to 100 km distance with a suitable amplifier gain and bandwidth. An important criteria for any amplifier is its gain and bandwidth for the compensation of the system loss and dispersion together. The optimum suitable pumping power is clarified for upgrade the system amplifier performance signature.

A Comprehensive Study on Phase Sensitive Amplification and Stimulated Brillouin Scattering in Nonlinear Fibers with Longitudinally Varying Dispersion

Fiber optic parametric and phase sensitive amplifiers (PSA) are interesting for modern day communication technologies due to their low noise and high gain amplification properties with a potential for all optical signal processing and wide band operation. PSAs are typically employed in either a single pump or dual pump configuration. In this article we explore the utilities of both configurations, however considering a fiber with a longitudinally varying dispersion profile. For the single pump case, PSA operation at large pump-signal detunings, that arise due to the longitudinal dispersion variation, were studied numerically, and recipes of using the system as a wide band wavelength selective filter were laid out. For the dual-pump case, emphasis was laid on achieving a larger signal gain, by reducing stimulated Brillouin scattering (SBS) that prevents large pump power transport through the nonlinear fiber. First, the effects of dispersion variation on the gain of a dual pump PSA were studied analytically and numerically in order to optimize the dispersion variation profile, neglecting SBS processes. Then we independently studied the SBS dynamics of the system numerically. A sinusoidally dispersion oscillating fiber (DOF) was found to be an optimal candidate with respect to its PSA and SBS performances. To establish this claim, we also experimentally compared the performance of an available DOF over a standard highly nonlinear fiber (HNLF) that has a constant dispersion profile and established its utility for designing a high gain PSA system, thanks to the SBS mitigation due to the longitudinal dispersion variation of the fiber.

Impact of Zero-Dispersion Wavelength Fluctuations in a Coupled Dual-Core Fiber Optical Parametric Amplifier

We have studied the impact of zero dispersion wavelength (ZDW) fluctuations in coupled dual-core fiber optical parametric amplifiers (FOPAs) and compared it to the single-core single-pump FOPA. We have designed a Monte Carlo model, that simulates a multidimensional Ornstein-Uhlenbeck process, describing accurately ZDW fluctuations in single and multicore fibers. In order to validate our results we have developed an analytical model, based on Taylor expansion of the average gain and successfully compared both models, with experimental results published in the literature. We have found that a significant reduction of the impact of ZDW fluctuations can be obtained in dual-core FOPAs compared to single-core ones.

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.

Noise analysis in a seeded four-wave mixing process generated in a photonic crystal fiber pumped by a chirped pulse.

Four-wave mixing is investigated when chirped pump and signal pulses are injected in a photonic crystal fiber. The shot-to-shot stability of the amplified coherent signal was measured by using the dispersive Fourier transform method and compared with numerical simulations. We highlight that the signal-to-noise ratio (SNR) of the pulsed signal increases with the injected power and show that it is not deteriorated through the amplification when the fiber optical parametric amplifier is strongly saturated. The SNR of the signal remains nearly constant after the amplifier.

Design of an interferometric fiber optic parametric amplifier for the rejection of unwanted four-wave mixing products.

We introduce a novel (to our knolwedge) interferometric fiber optic parametric amplifier (FOPA), allowing for the suppression of unwanted four-wave mixing products. We perform simulations of two configurations where one rejects idlers and, the other rejects nonlinear crosstalk from the signal output port. The numerical simulations presented here demonstrate the practical feasibility of suppressing idlers by >28 dB across at least 10 THz enabling the reuse of the idler frequencies for signal amplification and thus doubling the employable FOPA gain bandwidth. We demonstrate it can be achieved even when the interferometer employs real-world couplers by introducing a small attenuation in one of the interferometer arms.

Machine learning enabled digital compensation of phase-to-amplitude distor-tion in fibre-optical parametric amplifier based transmission links

We numerically demonstrate an advanced digital signal processing method for compensating the phase-to-amplitude distortion conversion caused by the interaction of the phase noise induced by pump dither-ing with the dispersive fibre channel in fibre-optical parametric amplifier based transmission systems.

Dual-pump few-mode fiber optical parametric amplification: analytical model and optimization strategy

The realization of long-haul mode-division multiplexing (MDM) transmission requires a matched optical amplifier with similar gain profiles among all guided modes. The fiber optical parametric amplifier (FOPA) has several attractive characteristics, including wideband, high gain, and fast transient response. Here, we demonstrate an analytical model for the dual-pump few-mode FOPA (FM-FOPA), by taking all types of intramodal and intermodal four-wave mixing (FWM) interactions arising in a highly nonlinear few-mode fiber (HN-FMF) into account. Meanwhile, we provide a detailed description of corresponding phase-matching conditions, including the effect of high-order dispersion coefficients up to the fourth order. Equipped with this tool, we outline the optimization strategy of the dual-pump FM-FOPA. Next, we design a graded-index HN-FMF to satisfy the dispersion requirements of the dual-pump FM-FOPA. Under the optimal HN-FMF design, the dual-pump FM-FOPA can simultaneously amplify two modes with the simultaneous features of wide bandwidth ( ∼ 35 n m ), high gain ( > --> 56.29 d B ), low differential mode gain (DMG) ( < 0.59 d B ), and low wavelength-dependent gain ripple (WDGR) ( < 1.92 d B ).

All-polarization-maintaining and high-energy fiber optical parametric chirped-pulse amplification system using a solid core photonic hybrid fiber.

We present an all-fiber optical parametric chirped-pulse amplification integrated system delivering a single-mode polarized beam. The system makes use of a specifically designed solid-core photonic hybrid fiber (i.e., combining modified total internal reflection and photonic bandgap mechanisms) that ensures sufficient birefringence to maintain the signal polarization. Moreover, the fiber combines a large mode area to handle energetic pump pulses (without generating damage or unwanted nonlinear effects) and weak dispersion to generate parametric gain bands broad enough to amplify ultrashort pulses. An efficient parametric process allows for obtaining a very high gain (>45 dB) with an output pulse energy reaching µJ range at 1053 nm by using a single 5-m hybrid fiber amplifier.

A dispersion engineered PCF for broadband fiber optic parametric amplification

A dispersion engineered PCF for broadband fiber optic parametric amplification

Dual-band fiber optic parametric amplifier for bi-directional transient-sensitive fiber optical transmission links.

We demonstrate an in-line polarization-insensitive fiber optic parametric amplifier (PI-FOPA) to simultaneously amplify burst and non-burst signals transmitted in opposite directions in C and L bands. The PI-FOPA provides >16 dB polarization insensitive net gain for signals which are 53 nm apart and counter-propagating in an extended reach link: an upstream bursty signal at 1533 nm and a downstream non-burst signal at 1586 nm. The PI-FOPA potential application as an in-line dual-band amplifier in transient-sensitive communication links is demonstrated by its employment in an extended reach access network with a symmetric 10 Gbps capacity.

Modeling pulse propagation in fiber optical parametric amplifier by a long short-term memory network

The ultrashort pulse evolution in fiber optical parametric amplifier (FOPA) systems is a highly complex nonlinear dynamic. Here, the long short-term memory network (LSTM) is applied to predicting the pulse propagation of signal waves in the FOPA system, rather than calculating the nonlinear Schrödinger equation (NLSE) numerically. The LSTM network only requires the initial signal power waveform, and the signal pulse propagation is realized in the feedback loop. Besides, we focus on predicting the evolution of signal pulse by varying the initial signal power and the initial signal pulse width to test the performance of our proposed method. The predictions of the LSTM network show great consistency with the NLSE results in each propagation stage of two cases, which reveal that the signal pulse evolution in FOPA is achieved precisely. The realization reduces the computational burden and further gives an effective way to optimize and guide the experiment and application in the FOPA systems.

Gain prediction of dual-pump fiber optic parametric amplifier based on artificial neural network

Optimized parameters of dual-pump fiber optic parametric amplifier (FOPA) to give optimized FOPA gain can be obtained through optimization techniques. However, it is complicated to determine the multi-objective functions (gain, bandwidth and flatness), multi decision variables and multiple global solutions. Optimization works only considered undepleted pump configuration or pump depletion but without fiber loss. Recently, a machine learning approach was applied to design a Raman amplifier. Thus, this study intends to design a desired dual-pump FOPA gain utilizing an artificial neural network (ANN) to predict pump powers and pump wavelength by considering pump depletion and fiber loss. First of all, the FOPA training gain data were obtained through the 6-wave model and supplied into the ANN to learn the relation between the gains with their pump wavelengths and pump powers. Once the smallest mean square error (MSE) between input and target was obtained, the ANN model was saved. The ANN model can be used to predict the desired pump wavelengths and pump powers if the desired gain is given. The desired gains of constant values from 10 to 45 dB over 1540–1589 nm for optical communication are predicted very well with mean absolute error (MAE) of 1 dB variations.

Investigation Of Dual-Pump Fiber Optical Parametric Amplifier Performance Driven by Energy Transfer Between Four-Wave Mixing Process

Fiber optical parametric amplifier (FOPA) is operated based on energy transfer from pump waves to signal wave and at the end of the fiber, an idler wave is generated. This process is called four-wave mixing (FWM). Even though effects of higher-order dispersion coefficients, fiber length, fiber nonlinearity, fiber attenuation, pump powers, pump wavelength separation and distance of central pump wavelength with ZDW on gain profiles have been examined by previous researchers, but on different fiber or numerically studied using the Optisys system, analytical model or different amplitude equations. Thus, in this study, the above-mentioned parameters on the gain performance of dual pump fiber optical parametric amplifier (FOPA) using highly nonlinear shifted fiber (HNL-DSF) as a medium will be numerically investigated using ode45 function in Matlab. The gain at a certain wavelength can be obtained by solving 4 coupled amplitude equations with fiber loss and pump depletion that govern the four-wave mixing (FWM) process of pumps, signal and idler waves. Simulations results indicate positive gives poor or no gain, meanwhile, an addition of to negative widens the bandwidth, but there is no significant effect with the addition of . Besides, an increase of fiber length, nonlinearity and pump powers improve gain performance, but an increase of fiber loss decays the gain amplitude. Increment of pump separation will enhance flatness of gain at wavelength far from central wavelength but results in an increase of gain reduction at the central wavelength. Lastly, must be positive, not too small and not bigger than 1.125nm to get a high, broader and lesser ripples gain.

Two-pump parametric amplification in the presence of fiber dispersion fluctuations: a comparative study.

Fiber optical parametric amplifiers (FOPAs) operating based on four-wave mixing (FWM) are versatile devices with increasing applications in optical communication systems. In this paper, the effects of dispersion fluctuations on the performance of bandwidth, ripple, parametric gain, and saturation power of a two-pump FOPA based on four-wave and six-wave models are studied and compared. Coupled-amplitude equations representing the non-degenerate FWM process in optical fiber are solved numerically to compute the parametric gain over the communication wavelengths. The behaviors of the performance parameters are critically analyzed and compared with different types of fluctuation strengths (or amplitudes) specified by the combinations of correlation length (Lc) and fluctuation amplitude (σ). Based on the results, it was found that the flat gain bandwidth for the four-wave model remains unchanged and is insensitive to the strengths of fluctuations. The gain ripples, however, get higher as the fluctuation strengths increase. On the other hand, the flat gain bandwidths of the six-wave model are hardly identified due to the tremendous and continuous ripples within the pump wavelengths. In addition, the minimum parametric gain values for both four-wave and six-wave models reduce as the fluctuation strengths increase. Also, the lowest value of parametric gain leads to the highest saturation power and vice versa. The dispersion fluctuations affect the FWM process's efficiency and deteriorate the overall amplifier performance, particularly for the six-wave model. The numerical analysis obtained via the six-wave model is especially useful since this model closely matches with practical circumstances.

Deep learning based pulse prediction of nonlinear dynamics in fiber optics

The initial state of a nonlinear optical fiber system plays a vital role in the ultrafast pulse evolution dynamic. In this work, a data-driven compressed convolutional neural network, named inverse network, is proposed to predict initial pulse distribution through a series of discrete power profiles at different propagation distances. The inverse network is trained and tested based on two typical nonlinear dynamics: (1) the pulse evolution in a fiber optical parametric amplifier system and (2) soliton pair evolution in high-nonlinear fibers. Great prediction accuracy is reached when the epoch grows to 5000 in both cases, with the normalized root mean square errors below 0.01 on the entire testing set. Meanwhile, the lightweight network is highly effective. In this work, it takes approximately 30 seconds for 5,000 epochs training with a dataset size of 900. The inverse network is further tested and analyzed on the dataset with different signal-to-noise ratios and input sizes. The results show fair stability at the deviation on the testing set. The proposed inverse network demonstrates a promising approach to optimizing the initial pulse of fiber optics systems.

Maintaining chromatic dispersion and signal gain performances in a chalcogenide buffer step-index optical fiber.

Aiming at maintaining the chromatic dispersion properties and fiber optical parametric amplification (FOPA) performance when fiber core fluctuation occurs, we propose a buffer step-index optical fiber. The AsSe2 chalcogenide glass is employed as the core material due to its high nonlinearity and broad transmission spectrum. The calculated results in this study show that the chromatic dispersion variation due to the change of core diameter can be greatly suppressed and a continuous and very broad FOPA signal gain spectrum can be obtained and maintained by carefully controlling the core, buffer and cladding properties such as refractive index and diameters. The calculated results in this study showed that by using the proposed 3-cm-long fiber pumped at 5.02 µm, a broad signal gain bandwidth from 3 to 14 µm at about 15 dB is attainable although the fiber core diameter Dc drastically fluctuated from 2 to 5 µm and the buffer diameter Db varies from 8.9 to 9.3 µm. Moreover, when Dc varies in smaller range from 3 to 4 µm, the FOPA signal gain spectra calculated at different fixed values of Db in the range from 8.9 to 9.3 µm are highly maintained. When Db is kept at 9.0 µm and Dc varies from 3 to 4 µm, the calculated FOPA signal gain spectra at different pump wavelengths from 4.98 to 5.02 µm are also nearly identical in the wavelength range from 3 up to 13 µm.

Looped Polarization-Insensitive Fiber Optical Parametric Amplifiers for Broadband High Gain Applications

We investigate polarization insensitive fiber optical parametric amplifiers (FOPAs) employing a balanced polarization diversity loop with at least two unidirectional gain fibers. We describe and compare three variants of looped polarization insensitive FOPAs optimized for noise figure, mitigation of nonlinear impairments and their trade-off, respectively. The test scenario consists of amplifying, by up to 14 dB, a set of 21 × 50 GHz-spaced channels including a 35 GBaud PDM-QPSK signal, and evaluating a power of nonlinear crosstalk, noise figure and amplified signal BER for each variant. For the first time we demonstrate a polarization insensitive FOPA amplifying WDM signals with a noise figure as low as 5.8 dB, and a polarization insensitive FOPA with output WDM signal power of 23 dBm. The testing results let us identify likely application scenarios for each looped FOPA variant. We justify potential implementation of polarization-insensitive FOPAs in future optical communication systems by arguing its ability to deliver low noise figure <6 dB for output signal power as high as 29 dBm and to enable polarization insensitive gain for the most prominent single-polarization FOPA achievements realizing ultrawide high gain.

Achieving gain flattening over 110 nm bandwidth using Er-Yb co-doped fiber/multi-section fiber optical parametric hybrid amplifier

This work demonstrates optical amplification in the entire C- and L-bands. A hybrid amplifier consisting of one stage of Er-Yb co-doped fiber amplifier (EYDFA) and two stages of fiber optical parametric amplifier is proposed. The EYDFA and parametric amplifier parameters have been carefully selected to achieve gain over complementary bandwidth regions, resulting in better gain flatness over 110 nm bandwidth. The proposed amplifier is investigated for 12 × 100 Gb/s wavelength division multiplexed system at channel spacing of 10 nm. Results show a flat gain of >27.42 dB with gain ripple of 3.17 dB, obtained over a wavelength range of 1530 to 1640 nm.