Fiber Optical Parametric Amplifier Research Articles

Raman and loss induced quantum noise in depleted fiber optical parametric amplifiers

We present a semi-classical approach for predicting the quantum noise properties of fiber optical parametric amplifiers. The unavoidable contributors of noise, vacuum fluctuations, loss-induced noise, and spontaneous Raman scattering, are included in the analysis of both phase-insensitive and phase-sensitive amplifiers. We show that the model agrees with earlier fully quantum approaches in the linear gain regime, whereas in the saturated gain regime, in which the classical equations are valid, we predict that the amplifier increases the signal-to-noise ratio by generating an amplitude-squeezed state of light. Also, in the same process, we analyze the quantum noise properties of the pump, which is difficult using standard quantum approaches, and we discover that the pump displays complicated dynamics in both the linear and the nonlinear gain regimes.

Gain saturation in a Raman-assisted fiber optical parametric amplifier

We investigate the gain saturation characteristics in a backward-pumped Raman-assisted fiber optical parametric amplifier (FOPA). It is experimentally observed that the onset of saturation occurs at a higher input power as compared to the case of a conventional FOPA with the same unsaturated gain. The output power under strong saturation is also enhanced. Simulations are performed on the power profile of the parametric pump to explain the distinct saturation behaviors. The monotonic increase of the parametric pump power in the Raman-assisted FOPA results in highly efficient power transfer to the signal while it suppresses the signal conversion to high-order idlers in the saturation regime.

Dynamic characterization and amplification of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers

We show a first-time demonstration of amplification of 400 fs pulses in a fiber optical parametric amplifier. The 400 fs signal is stretched in time, amplified by 26 dB and compressed back to 500 fs. A significant broadening of the pulses is experimentally shown due to dispersion and limited gain bandwidth both in saturated and unsaturated gain regimes.

Parametric amplification and phase preserving amplitude regeneration of a 640 Gbit/s RZ-DPSK signal

We report the first experimental demonstration of parametric amplification and all-optical phase-preserving amplitude regeneration for a 640 Gbit/s return-to-zero (RZ) differential phase-shift keying (DPSK) optical time division multiplexed (OTDM) signal. In the designed gain-flattened single-pump fiber optical parametric amplifier (FOPA), 620 fs short optical pulses are successfully amplified with 15 dB gain with error-free performance and less than 1 dB power penalty. Phase-preserving amplitude regeneration based on gain saturation in the FOPA is carried out for optical signals with degraded optical signal-to-noise ratio. An improvement of 2.2 dB in receiver sensitivity at a bit-error-ratio of 10(-9) has been successfully achieved after regeneration, together with 13.3 dB net gain.

Gain optimization of fiber optical parametric amplifier based on genetic algorithm with pump depletion

A method to optimize the gain of a fiber optical parametric amplifier (FOPA) is presented by using a genetic algorithm (GA), which can determine the parameters of FOPA and avoid the trouble of trial and error to achieve it. The effect of pump depletion on the gain characteristic of the FOPA is emphasized, and the effects of the fiber length, the wavelength, and the power of two pumps on bandwidth, flatness, and magnitude of the gain spectrum are also studied. According to the presentation, fiber length and the wavelength of the two pumps are selected to be the variable parameters in the GA. When the parameters of the fiber are determined, with the numerical simulation, the optimum combination scheme between those chosen variables could be obtained by the algorithms with the result of the gain optimization of FOPA.

Dynamic Control of Gain Profile in Fiber-Optical Parametric Amplifier by Gain-Transparent SBS

We propose and experimentally demonstrate dynamic control of gain profile in a single-pump fiber-optical parametric amplifier (FOPA) assisted by gain-transparent stimulated Brillouin scattering. The FOPA gain can be enhanced/reduced through controlling the phase-matching condition without disturbing the initial parameters of the FOPA. Both the maximum and minimum gain profiles are obtained, offering operational flexibility in randomly synthesizing the profile to satisfy different requirements. Our synthesis can turn the conventional M-shaped profile into spectrally flat gain with 0.1-dB variation over 24 nm. This scheme can be potentially applied to dual-pump FOPA and can benefit other applications of parametric processes.

Multimode theory of pulsed-twin-beam generation using a high-gain fiber-optical parametric amplifier

Using the Bogoliubov transformation in multi-frequency modes to describe the evolution of the non-degenerate signal and idler twin beams, we theoretically investigate the quantum noise properties of the pulse pumped high gain fiber optical parametric amplifiers (FOPA). The results show that the noise figure of the FOPA is generally greater than the 3 dB quantum limit unless the joint spectral function is factorable and the spectrum of the input signal well matches the gain spectrum in the signal band. However, the intensity difference noise of the twin beams, which weakly depends on the joint spectral function, can be significantly less than the shot-noise limit when the temporal modes of the pump and the input signal are properly matched. Moreover, to closely resemble the real experimental condition, the quantum noise of twin beams generated from a broadband FOPA is numerically studied by taking the various kinds of experimental imperfections into account. Our study is not only useful for developing a compact fiber source of twin beams, but also helpful for understanding the quantum noise limit of a pulse pumped FOPA in the fiber communication system.

Modelling of noise suppression in gain-saturated fiber optical parametric amplifiers

Noise properties of both one-pump (1-P) and two-pump (2-P) fiber optical parametric amplifiers (FOPAs) are theoretically investigated and particularly the unique feature of FOPAs for the noise suppression in the gain-saturated regime is modeled. For the 1-P FOPAs, the simulation results are compared with the available experimental data and a very good agreement is obtained. Also, for the 2-P FOPA where no experimental work has been reported regarding their noise properties in the saturation regime, the noise behavior of the amplified signal is simulated for the first time. It is shown that for a specific power in the deep saturation regime, the signal noise is suppressed; and with further increase of the signal power when the gain saturation reaches its new cycle, a periodic behavior of noise suppression is observed originating from the phase-matching condition. The existence of a negative feedback mechanism which is responsible to the suppression of the excess noise in the first cycle of the gain saturation is confirmed both for 1-P and 2-P FOPAs. Generally, it is shown that the noise suppression can be observed for several specific powers at which the slope of the output signal power versus the input one is zero. The results of this paper may have some applications in signal processing, e.g., cleaning noisy signals.

A Fourier domain mode-locked fiber laser based on dual-pump fiber optical parametric amplification and its application for a sensing system

A Fourier domain mode-locked (FDML) fiber laser based on dual-pump fiber optical parametric amplification (FOPA) is proposed and demonstrated. The output spectrum of the proposed FDML fiber laser covers a sweeping wavelength range from 1540.8 to 1559.8 nm with a sweeping frequency of 31.688 kHz. A comparison of two FDML fiber lasers which are based on dual-pump FOPA and one-pump FOPA is also presented. A novel sensing system based on the FDML laser and a fiber Bragg grating, by which the sensing signal can be measured in the time domain instead of the frequency domain, is also demonstrated.

Amplification of ultra-short optical pulses in a two-pump fiber optical parametric chirped pulse amplifier

We demonstrate with realistic numerical simulations that fiber optical parametric chirped pulse amplification is able to amplify ultra-short optical pulses. Such amplifiers driven by two-pump waves can amplify pulse bandwidth twice as large as the one of a single pump configuration. We show that pulses as short as 50 fs can be directly amplified. In addition, we take benefit from the saturation regime to achieve spectral broadening which makes possible to reduce pulse duration down to 15 fs.

Performance Evaluation of DWDM Communication Systems With Fiber Optical Parametric Amplifiers

We derive analytical expressions for the performance of a long-haul DWDM communication system employing in-line phase insensitive fiber optic parametric amplifiers (FOPA). In our analysis the impairments of both transmission fibers and FOPAs are taken into account. The analytical model is verified with simulations. The performance of FOPA is compared with EDFA and it is shown that a broad band long-haul DWDM transmission system based on FOPAs as in-line amplifiers could be feasible.

A Nonlinear Model for the Operation of Fiber Optical Parametric Oscillators in the Steady State

In contrast to fiber optical parametric amplification, theoretical studies on the dynamics of fiber optical parametric oscillation are rare. In this letter, we propose a precise nonlinear model to predict the saturation gain and the output power of a fiber optical parametric oscillator (FOPO) in the steady state. This model utilizes the sinusoidal-input describing function as a quasi-linear approximation of the nonlinear dynamics of parametric amplification. To complete the nonlinear model of a FOPO, a model for the linear part of the FOPO cavity is established, and then the block diagram of a FOPO is derived. Based on this block diagram and the related transfer function, a graphical approach to attain the saturation gain and output power is introduced. In addition, a simplified graphical approach and a theoretical upper bound for the output power are investigated. Finally, the proposed model is experimentally verified, in which the theory is in agreement with the experiment.

Erratum: Analysis of crosstalk between 10 Gb/s × 64 channels in two-pump fiber optical parametric amplifier

Originally published Microwave Opt Technol Lett 55:926–929, 2013. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1703, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27668 (Original article DOI 10.1002/mop.27408)

In-line one-pump parametric amplifier with independent polarization gain: A field-trial demonstration

We present a one-pump parametric amplifier with polarization independent gain working as an in-line amplifier within an experimental field-trial optical network. The polarization independent gain is obtained by using a polarization diversity technique (PDT). Five signals modulated at 10 Gb/s were transmitted through the network, and a gain variation as low as 0.05 dB, independent of the signal polarization, was obtained. The bit-error-rate (BER) for the amplified signals was measured. For a BER of 10−9, a power penalty as low as 0.7 dB is shown. These measurements were compared with the identical ones obtained when the parametric amplifier with the PDT was replaced by an Erbium-doped fiber amplifier (EDFA). The fiber optical parametric amplifier (FOPA) with the PDT presents a power penalty of 0.7 dB in relation to the value obtained with the EDFA. These results show that parametric amplifiers that use the PDT are able to reach a performance comparable to those obtained with the current technology of optical amplifiers based on rare earth doped fibers. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1104–1107, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27481

Experimental investigation of saturation effect on pump-to-signal intensity modulation transfer in single-pump phase-insensitive fiber optic parametric amplifiers

We present an experimental characterization of how signal gain saturation affects the transfer of intensity modulation from the pump to the signal in single-pump, phase-insensitive fiber optic parametric amplifiers (FOPAs). In this work, we demonstrate experimentally for the first time, to our knowledge, how gain saturation of a FOPA reduces the noise contribution due to the transfer of pump power fluctuations to the signal. In a particular example, it is shown that the transferred noise is significantly reduced by a factor of 3, while the FOPA gain remains above 10 dB.

Analysis of crosstalk between 10 Gb/s x 64 channels in two-pump fiber optical parametric amplifier

We present a numerical study of 64 signals amplified by a two-pump fiber optical parametric amplifier. The amplifier was alternatively simulated with two fibers with different values of nonlinear coefficient but the same length. The gain remained constant in both cases. The performance of the amplifier is improved when it is designed with the fiber of lower nonlinear coefficient. Also, it was observed that the performance of the amplifier is strongly dependent on channel separation. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:926–929, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27408

Polarization-Insensitive Phase-Preserving Regenerator Based on a Fiber Optical Parametric Amplifier With Dual Orthogonal Pumps

We investigate the gain-saturation characteristics of a dual-orthogonal-pump fiber optical parametric amplifier. Nearly uniform power transfer functions have been obtained for various input signal polarizations by adjusting the total pump power. Based on this physical behavior, we demonstrate polarization-insensitive phase-preserving amplitude regeneration of 40-Gb/s nonreturn-to-zero differential phase-shift keying signals. The receiver sensitivity has been improved by a maximum value of 4.7 dB.

Amplification paramétrique dans les fibres optiques - Fondements et applications

Fiber optical parametric amplifiers rely on the phase-matched four wave mixing process. This class of optical amplifier differs by nature from other fiber-based optical amplifiers such as Raman or erbium-doped ones. As a consequence, their intrinsic properties such as wide spectral gain band, wavelength tunability and quasi-instantaneous time response make them very attractive for telecommunication applications or all-optical processing.

Impact of dispersion slope on performance of fibre‐optic‐parametric‐amplifier‐based all‐optical amplitude limiter

The high-speed amplitude limiting performance of a saturated fibre-optic parametric amplifier is numerically studied. It is shown that walk-off between the pump and signal pulses caused by a large dispersion slope makes the saturation behaviour less efficient and induces interaction between neighbouring signal pulses mediated by temporally-broadened pump depletion, both of which degrade the limiter performance.

An all-fiber source of pulsed twin beams for quantum communication

Motivated by the pursuit of a simple system to produce a continuous variable non-classical light source for long-distance quantum communication, we construct an all-fiber source of pulsed twin beams in the 1550 nm band by using a high gain fiber optical parametric amplifier. The intensity-difference noise of the twin beams is below the shot noise limit by 3.1 dB (10.4 dB after correction for losses). A detailed study reveals a number of limiting factors for noise reduction. Therefore, further noise reduction will be feasible once care is taken for these limiting factors.