Fiber Optical Parametric Amplifier Research Articles

Phase-to-phase and phase-to-amplitude transfer characteristics of a nondegenerate-idler phase-sensitive amplifier

For the first time to our knowledge, the phase-to-phase and phase-to-amplitude transfer functions of a nondegenerate-idler phase-sensitive fiber optic parametric amplifier are experimentally measured. Additionally, analytically and numerically obtained transfer curves show excellent agreement with the experimental curves. The experimental results were obtained by imposing a linear phase modulation onto the signal and idler wave simultaneously, and detecting the input and output signal using a self-homodyne coherent receiver.

6-channel photonic generation of ultra-wideband signals using multiple nonlinear characteristics in a parallel FOPA structure

We propose an approach to generating 6-channel polarity-inverted ultra-wideband (UWB) doublets by utilizing the parallel fiber-optical parametric amplifier (FOPA) configuration. The pulse-splitting effect in a highly nonlinear fiber (HNLF) is exploited to generate the double-overshoot and the double-undershoot, which are the basic components required to form a UWB pulse. Under the circumstances of different relative time advance/delays (RTADs) and different initial Gaussian pulse durations, the key parameters, including center frequency (Fc), 10-dB bandwidth (BW10dB) and fractional bandwidth (FBW) for a UWB doublet are systematically investigated, eventually proved in line with the U. S. Federal Communications Commission (FCC) regulation.

Influence of Raman effect on the noise characteristics in a dual pump FOPA

Influence induced by Raman effect on the noise characteristics of a depleted and lossy dual pump fiber optical parametric amplifier (FOPA) is investigated. Taking the Raman effect into account, the modified coupled amplitude equations are firstly built, then the influences of Raman effect on the Stokes and anti-Stokes wavelengths with different initial signal powers are further analyzed. Besides, the effect on the FOPA gain is also shown with the same initial signal power and constant noise figure (NF).

Dynamics of fiber optical parametric chirped pulse amplifiers

We numerically and experimentally investigate the complete dynamics of the amplification process occurring in fiber optical parametric chirped pulse amplifiers. We show that, in the linear amplification regime, more than 30% of the pump can be converted into the signal with a very good temporal contrast higher than 65 dB. Under strong saturation, this efficiency is kept constant but the temporal contrast of the signal significantly degrades.

Polarization independence and phase-sensitive parametric amplification

We investigate the possibility of obtaining phase-sensitive amplification (PSA) in a fiber-optic parametric amplifier (OPA), with gain independent of the state of polarization of the input signal, i.e., polarization-independent amplification. We consider both a single OPA with two orthogonal pumps and a polarization-diversity scheme. In either case, PSA with maximum gain is possible, provided that the signal and idler are in suitably matched polarization states; this condition is naturally satisfied by the output fields of an upstream polarization-insensitive amplifier of the same type. Two polarization-multiplexed signals can then be simultaneously amplified in the PSA. The low noise figure can also be obtained with these types of PSA. However, in general, this favorable situation is not maintained if the signal and idler states of polarization drift together due to birefringence fluctuations in a transmission fiber preceding the PSA.

Continuous-Wave Parametric Amplifier With 6.9-ExaHz Gain-Bandwidth Product

A continuous-wave two-pump fiber-optic parametric amplifier with a record small-signal gain-bandwidth product of 6.9 EHz is reported. The amplifier was used to achieve errorless amplification of a 10.7-Gb/s nonreturn-to-zero differential-phase-shift-keyed signal. The receiver performance limit was defined by pump depletion, with the maximal gain limit set by the gain saturation of amplified quantum noise. The record performance was achieved using a bandwidth-efficient pump dithering technique.

Multiple Raman Pump Assisted Fiber Optical Parametric Amplifiers

We studied the use of multiple Raman pumps to assist fiber optical parametric amplifiers (FOPAs). We derived a theoretical model to describe the performance of multiple Raman pump assisted FOPAs. We demonstrated that the over 40 nm flat gain bandwidth provided by the multiple Raman pumps can be used to support the parametric gain bandwidth of Raman-assisted FOPAs (RA-FOPAs). We also found that if indirect Raman gain contribution dominates, by using dispersion-flattened highly nonlinear fiber with small dispersion slope and polarization-mode dispersion effect, broadband FOPA with broad parametric pump wavelength tuning range can be obtained by using multiple Raman pump assistance. On the other hand, if direct Raman gain contribution dominates, the parameters of the multiple Raman pumps have to be chosen carefully to ensure that the Raman gain bandwidth matches the parametric gain bandwidth in order to achieve a flat gain with broad gain bandwidth in the RA-FOPAs.

Numerical modelling of the pump-to-signal relative intensity noise transfer in two-pump fibre optical parametric amplifiers

An accurate numerical model to investigate the pump-to-signal relative intensity noise (RIN) transfer in two-pump fibre optical parametric amplifiers (2-P FOPAs) for low modulation frequencies is presented. Compared to other models in the field, this model takes into account the fibre loss, pump depletion as well as the gain saturation. As a result, the model allows to include a wide range of practical circumstances, both in and beyond the undepleted pump regime, related to different applications of FOPAs. In the small-signal or undepleted pump regime, the model predicts the ripples of the RIN spectrum very well and yields better results than those of other models. It is shown that beyond the small-signal regime, pump power variations do not remain unchanged over the length of the amplifier and for high signal powers, when the FOPA saturates, minimum pump-to-signal RIN transfer occurs. The results of the model are also compared with the available experimental data in the field and a very good agreement can be seen.

Polarization-insensitive fiber optical parametric amplifier based on polarization diversity technique with dual parallel pumps

By analyzing the principle of dual-pump parametric amplification and the polarization dependent gain of fiber optical parametric amplifier (FOPA), a polarization-insensitive FOPA based on polarization-diversity technique with dual parallel pumps is presented. The performances of polarization-insensitivity, gain and BER are theoretically analyzed and numerically simulated by comparing the proposed scheme with parallel pump solution and orthogonal pump solution. The presented solution can reduce the complexity of state of polarization (SoP) of pumps.

Fiber-Optical Parametric Amplifier With High-Speed Swept Pump

We experimentally demonstrate and characterize a high-speed frequency-swept pump in a fiber-optical parametric amplifier (FOPA). The high-speed swept pump is achieved with the swept rate as high as 78 MHz by a technique called dispersive Fourier transformation (DFT), which circumvents the fundamental speed limitation shown in the conventional swept-sources based on the cavity configurations. Based on such swept pump FOPA, the idler can be generated with a wavelength range twice the pump bandwidth. Such an all-optical approach offers an order-of-magnitude higher swept rate and thus lends itself to many applications such as high-speed signal processing and optical imaging.

Wavelength-spacing tunable multi-wavelength fiber optical parametric oscillator based on multiple four-wave mixing

We propose a wavelength-spacing tunable multi-wavelength fiber optical parametric oscillator (MW-FOPO) with a simple line cavity and one pump source based on multiple four-wave mixing (MFWM). Stable multi-wavelength lasing at room temperature is achieved due to the four-wave mixing effect and the broadband gain of the fiber optical parametric amplifier based on a highly nonlinear fiber. The wavelength spacing of the proposed MW-FOPO can be tuned by adjusting the wavelength of the pump light or the central wavelength of the fiber Bragg grating. Seventeen lasing lines with a wavelength spacing of 2.89 nm and an extinction ratio larger than 10 dB, which covers the wavelength region from 1540 to 1568 nm is demonstrated.

DPSK Signal Regeneration With a Dual-Pump Nondegenerate Phase-Sensitive Amplifier

We demonstrate, for the first time to our knowledge, regeneration of a 42.66-Gb/s differential phase-shift keyed signal using a dual-pump nondegenerate four-wave-mixing-based fiber-optic parametric amplifier. The regenerative performance of the subsystem is characterized in terms of bit-error rate against narrowband and wideband introduced noise. While a strong receiver sensitivity improvement, up to 20 dB, is noticed against narrowband noise, against quasi-random (wideband) noise we observe a regeneration of 2.7 dB.

Optimization of Raman-Assisted Fiber Optical Parametric Amplifier Gain

We studied the gain of Raman-assisted fiber optical parametric amplifiers (RA-FOPAs) both theoretically and experimentally. We investigated the relationship between the overall gain and different combinations of Raman and parametric pump powers using contour maps. We derived a normalized phase-matched model to determine the general behavior the peak gains of RA-FOPAs operating in the small signal region. The contour maps of the combined gain enhancement can be used to optimize both indirect and direct Raman gain of the signal/idler in RA-FOPAs. We showed that, in a given fiber, it is possible to optimize the Raman and parametric pump powers in RA-FOPAs for high gain and high efficiency.

160-Gb/s Polarization-Insensitive Demultiplexer Based on a Fiber-Optical Parametric Amplifier

We report the experimental demonstration of a 160-Gb/s polarization-insensitive demultiplexer based on a pulsed-pump fiber-optical parametric amplifier. Switching window and 12-dB conversion gain are measured with polarization scrambled signal. No more than 1.5-dB power penalty is achieved for 16 demultiplexed 10-Gb/s tributaries.

Full and semi-analytic analyses of two-pump parametric amplification with pump depletion

This paper solves the four coupled equations describing non-degenerate four-wave mixing, with the focus on amplifying a signal in a fiber optical parametric amplifier (FOPA). Based on the full analytic solution, a simple approximate solution describing the gain is developed. The advantage of this new approximation is that it includes the depletion of the pumps, which is lacking in the usual quasi-linearized approximation. With the proposed model it is thus simple to predict the gain of a FOPA, which we demonstrate with a highly nonlinear fiber to show that an undepleted FOPA can produce a flat gain spectrum with a bandwidth in the 100-nm range, centered on the zero-dispersion wavelength. When running the FOPA in depletion, this range can be slightly increased.

Tunable slow and fast light with large bandwidth in the band-edge of gain spectrum of the wide band fiber optical parametric amplifier

We propose a novel method theoretically to generate the slow and fast light with large bandwidth and low gains, which is based on the parametric process in fiber. In our scheme, the wide band fiber optical parametric amplifier is employed and the whole signal bandwidth should be located at a certain frequency range of the band-edge of gain spectrum, and then signal waves will be delayed or advanced with low signal gains because of the peculiar feature of signal gain and phase shift. By changing the pump power, the delay time is continuously-tunable optically. The ultimate delay bandwidth and the delay bandwidth product are constrained by the shape of time delay spectrum. Our simulation verifies that 22.4 ps delay or advanced time for the bandwidth of 10 GHz with little distortion can be obtained at certain wavelengths in the optical communication waveband, and their gains are nearly zero. The tunable range is from 0 ps to 22.4 ps for the signal bandwidth of 10 GHz, and it is from 0 ps to 15.6 ps for the bandwidth of 15 GHz. This type of slow and fast light in wide band FOPA has the potential capability to produce the tunable slow and fast light for large bandwidth with low signal gains in future.

Impact of Zero-Dispersion-Wavelength Distributions on the Noise Figure Nonreciprocity of a Fiber Parametric Amplifier

For the first time we both theoretically and experimentally show that the zero-dispersion-wavelength (ZDW) variations in highly nonlinear fibers (HNLFs) will modify the output noise figure (NF) of a fiber optical parametric amplifier and make it nonreciprocal, due to the Raman phonon induced excess noise. The results show that a longer ZDW (but still below the pump wavelength) close to fiber input will give a better noise performance. The experimental results agree well with theory.

An all-optical 3R regenerator for 40-Gbit/s system based onsignal-pump fiber optical parametric amplification

A novel scheme of all-optical 3R regeneration has been proposed in this paper. Using degraded data signal rather than clock as a pump, all-optical 40Gbps 3R regeneration based on a fiber optical parametric amplification effect (FOPA) is realized with improved performance compared with previous regeneration schemes. Theoretical analysis of the noise suppression mechanism under different pump power (corresponding to "0" code or "1" code) is provided. By properly adjusting the parameters of FOPA, amplitude noise on both "0" code and "1" code can be suppressed simultaneously. The clock extraction is based on wavelenth conversion and a Fabry-Pérot (F-P) filter with a high Q value of 1000. The theoretical analysis conclusions are verified through experiments, and the imbalance of the 3R regeneration using fiber optical parametric amplication is eliminated. The root mean square (RMS) jitter of the clock extracted is only 180fs. The signal-to-noise ratio of the regenerated signal is improved from 4.52 to 11.43.

Two-Wavelength Square-Waveform Generation Based on Fiber Optical Parametric Oscillator

A square-waveform generator based on a fiber optical parametric oscillator (FOPO) is proposed and demonstrated experimentally. The FOPO works fundamentally by extracting the longitudinal modes beating signal to drive the intracavity amplitude modulator. In order to broaden the longitudinal mode spacing, two sub-ring cavities with a short cavity length are used. The longitudinal modes are phase locked, which ensures the generated microwave signal with very low phase noise. By biasing the amplitude modulator, the even-order beating signals are suppressed, while the odd-order beating signals are enhanced. Thus, the FOPO is self-starting and can provide stable square-waveform output with the repetition rate of 1.133 GHz at the signal and idler simultaneously. It is tunable over 10 nm, which is only limited by the gain bandwidth of the fiber optical parametric amplifier of the current configuration.

High-gain fiber, optical-parametric, chirped-pulse amplification of femtosecond pulses at 1 μm

Fiber-based optical-parametric chirped-pulse amplification is reported at 1μm in a microstructured fiber in the femtosecond regime. The signal has been highly stretched by an Öffner triplet and then amplified with an all-fiber, pulsed-pump, fiber optical-parametric amplifier. More than 30dB gain has been achieved over 8.3nm, and the amplified signal has been recompressed.