One-pump Fiber Optical Parametric Amplifiers Research Articles

Saturation behavior of a one-pump fiber optical parametric amplifier in the presence of the fourth-order dispersion coefficient and dispersion fluctuation

The influence of the fourth-order dispersion coefficient on the behavior of parametric gain and saturation power of a one-pump fiber optical parametric amplifier over a signal wavelength span in the presence of fiber random dispersion fluctuations was investigated. The output signal power for the parametric gain calculation was obtained by numerically solving the three-coupled amplitude equations. Based on the calculations of the parametric gain over a variation of the signal wavelength, it is found that the saturation power behavior is dependent on the behavior of parametric gain. The manipulations of signal wavelength and the fourth-order dispersion coefficient changed the phase-matching condition, thereby affecting the resulting parametric gain and saturation power.

One-pump fiber optical parametric amplifiers: from the pulsed to the continuous wave operation

The characteristics of one-pump fiber optical parametric amplifiers (1-P FOPAs) are theoretically investigated as the temporal width of the input pump increases from the pulsed to the continuous wave (CW) regime. Coupled nonlinear Schrodinger equations are numerically solved, and the pulse width of the pump is gradually increased to simulate the evolution of the gain and output spectra of the 1-P FOPA from the pulsed to the CW operation. The results show that the quasi-CW operation is achieved when the pulse width is about 500 fs. Also, when the temporal width of the pump increases and lies in the picosecond regime, the characteristics of FOPA recover those of the FOPA operated in the CW regime.

One-pump fiber optical parametric amplifier in presence of dispersion fluctuations: impact of fourth-order dispersion coefficient.

The impact of random dispersion fluctuations on the gain and saturation behavior of a one-pump fiber optical parametric amplifier (1-P FOPA) in the presence of fourth-order dispersion coefficient (β4) is investigated. Three coupled amplitude equations with fiber losses are solved numerically for the calculation of the pump, signal, and idler. The performances of 1-P FOPA are also analyzed with variation of dispersion fluctuation amplitude (σ) and correlation length (Lc). Based on the numerical results, it is found that the gain spectra and saturation curves exhibit some differences when β4 is considered. In comparison with the case where β4 is ignored, the peak gain remains the same, but the 3dB bandwidth increases when β4 exists. Another notable difference is that the saturation power is shifted to lower or higher values, depending on the σ and Lc parameters. In general, the peak gain reduces as σ increases, and the peak gain reduction is greater for the case of shorter Lc. The numerical analysis is probably useful, especially for the case where the signal wavelength is detuned far from the pump wavelength.

Numerical Simulation of Highly-Nonlinear Dispersion-Shifted Fiber Optical Parametric Gain Spectrum with Fiber Loss and Higher-Order Dispersion Coefficients

The previous study investigated the fiber parameters on the analytical one-pump fiber optical parametric amplifier (FOPA) gain spectrum of a loss-free highly-nonlinear dispersion-shifted fiber (HNL-DSF) and got the optimum results for each parameter. However, the FOPA gain of the combination of all the optimum values of the considered parameters was not reported. Hence, this paper intends to investigate the analytical FOPA gain of the combination of all the optimum values of the considered parameters from the previous study. Later, the analytical gain was compared with the numerical gain from the fourth-order Runge-Kutta (RK4) method and Matlab built-in function, ode45. Next, the effect of fiber loss and higher order dispersion coefficients such as fourth and sixth-order dispersion coefficients were studied. It is found that RK4 gives a smaller error and the gain reduces while the bandwidth remains same in presence of fiber loss. The fourth-order dispersion coefficient broadens the bandwidth a bit while maintaining the gain and there are two narrow-band gains generated to the left and right-side of the broad-band gain. The sixth-order dispersion coefficient just shifts the two narrow-band gains toward or away from the broadband gain depending on the positive or negative signs of the sixth-order dispersion coefficient.

Gain-saturated one-pump fiber optical parametric amplifiers in presence of longitudinal dispersion fluctuations

In this paper, we investigate the impact of longitudinal dispersion fluctuations of the optical fiber on the gain spectrum and the saturation behavior of one-pump fiber-optical parametric amplifiers (1-P FOPAs). The gain spectra and the saturation curves of 1-P FOPAs are simulated by solving the coupled amplitude equations numerically and taking into account the dispersion fluctuations as a stochastic process with a given standard deviation and correlation length. Results show that the shape and the level of the gain spectrum and also the saturation power of 1-P FOPAs are considerably changed in the presence of dispersion fluctuations in comparison with the case when dispersion fluctuations are ignored. This feature is also totally different compared with the small-signal gain spectrum of the FOPA in the presence of dispersion fluctuations. Moreover, the value of the change in the gain and the saturation power depends strongly on the fluctuation parameters, i.e., the standard deviation and the correlation length.

Designing one-pump fiber optical parametric amplifiers for an insensitive amplification to dispersion fluctuations

Small-signal gain spectrum of one-pump fiber optical parametric amplifiers (1-P FOPAs) is investigated in the presence of dispersion fluctuations. By assuming the dispersion fluctuations along the fiber as a stochastic process and using the matrix approach, the full gain spectrum of 1-P FOPAs is simulated. We have examined the gain spectrum of 1-P FOPAs for a wide range of fluctuation parameters, and it is shown for the first time that there are two specific wavelengths at which the dispersion fluctuations play no role. Analytical formulas are also presented to design 1-P FOPAs for amplifying signals with a gain insensitive to dispersion fluctuations.

Gain optimization of one-pump fiber-optical parametric amplifier with optical band-pass filter reducing the idler wave

The gain optimization characteristics of a one-pump fiber-optical parametric amplifier with an optical band-pass filter (OBPF) reducing the idler wave is investigated numerically. The phase mismatching is compensated, thus both the maximum gain and the gain bandwidth are optimized with the OBPF inserted in, and the flatter gain can be obtained; meanwhile, the conversion efficiency of the pump power to the signal power is increased. The influence of filter attenuation on the gain is also discussed. It is shown that, by properly selecting the parameters of the fiber, signal wave, pump wave, and filter, the optimized gain can be obtained, which is extremely useful for the optical communication systems.

Solutions for first- and second-order four-wave mixing cross talk in one-pump fiber optical parametric amplifiers

We show that the set of two coupled differential equations governing a four-wave mixing (FWM) component and its associated idler in a one-pump fiber optical parametric amplifier are the same as for standard parametric amplification, but with additional source terms arising from FWM between already-calculated waves. We show how to solve this new set of equations in general: this involves multiplication by an exponential matrix and its inverse, and integration. Hence it is in principle possible to write the exact expressions for the cross-talk fields, in terms of a large number of exponentials. The results show that the power of the first- and second-order cross-talk terms scales, respectively, like the first and second power of the signal power. In the case of two input signals, the powers of the cross-talk terms are independent of the phases of the signals, hence phase control cannot be used for reducing cross talk. In a particular case, cross talk scales like the inverse of pump power, which confirms a general trend noted in numerical simulations, and experiments.

Polarization independent wavelength conversion in fibers using incoherent pumps

We report polarization independent wavelength conversion based on one-pump fiber optical parametric amplifiers. A spectrum-sliced amplified spontaneous emission (ASE) light source is used to provide a non-polarized pump. The signal is coherent lights coming from a tunable laser. When adjusting the polarization of the signal using a polarization controller, the variation of wavelength conversion efficiency is less than 0.2 dB. We use the vector theory of four-wave mixing to analyze the polarization independent nature of wavelength conversion by using randomly polarized pumps.

Wide-Band Tuning of the Gain Spectra of One-Pump Fiber Optical Parametric Amplifiers

By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra. These can range from a very wide single region to two symmetric narrow gain regions far away from the pump. We have experimentally verified these predictions. With a highly nonlinear fiber, we have inferred the existence of gain over a single 400-nm region and measured a maximum on-off gain of 65 dB. With a common dispersion-shifted fiber, we have obtained tunable gain regions less than 1 nm wide, up to 200 nm from the pump; we have also shifted these by several nanometers by lowering the fiber temperature to 0/spl deg/C.

Polarization-independent one-pump fiber-optical parametric amplifier

One-pump fiber optical parametric amplifiers (OPAs) can be rendered polarization independent by using a polarization-diversity technique. We have experimentally demonstrated a fiber OPA with peak signal gain of 9 /spl plusmn/ 0.2 dB when the signal polarization angle was varied from 0/spl deg/ to 90/spl deg/. Power penalty of less than 1 dB was measured in a 10-Gb/s transmission system.

200-nm-bandwidth fiber optical amplifier combining parametric and Raman gain

Theory shows that the gain bandwidth of a one-pump fiber optical parametric amplifier (OPA) using highly nonlinear fiber (HNLF) could be more than 200 nm. Under these circumstances, the OPA gain would overlap the pump-induced Raman gain. We have studied the combined effects of OPA and Raman gain theoretically and experimentally. The experimental results demonstrate a 200-nm bandwidth from a single fiber-optical amplifier and also verify that the influence of the Raman effect is relatively small, as predicted by the theory.

92% pump depletion in a continuous-wave one-pump fiber optical parametric amplifier

Theory shows that near-complete pump depletion can be obtained in uniform fiber-optic parametric amplifiers (OPA's) for a particular phase-matching condition. We have demonstrated 92% pump depletion in a cw fiber OPA, with a 200-mW pump at 1560 nm in an 11-km-long dispersion-shifted fiber.

High-nonlinearity fiber optical parametric amplifier with periodic dispersion compensation

Theory shows that the maximum gain and bandwidth of one-pump fiber optical parametric amplifiers made from high-nonlinearity fiber, operated with a pump wavelength /spl lambda//sub p/ far from the fiber zero-dispersion wavelength /spl lambda//sub 0/ can greatly be improved by periodic dispersion compensation. We have performed experiments and obtained good agreement with theory: for /spl lambda//sub p/=1542 and /spl lambda//sub 0/=1591 nm, we have increased the bandwidth from 7 to 28 nm, and the maximum gain from 15 to 20 dB, by splicing three pieces of standard fiber at regular intervals in a 40-m long nonlinear fiber.