Fiber Optical Parametric Amplifier Research Articles

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.

Fibre optic parametric amplifier for high capacity burst-mode access networks.

We compare performance of a polarization insensitive fiber optic parametric amplifier (PI-FOPA), a commercial erbium doped fiber amplifier (EDFA) and a discrete Raman amplifier (DRA) in a 50 km long-reach optical access network transmitting bursts of 10 Gbps signal with traffic density ranged from 5% to 97%. We demonstrate that for the same power budget the PI-FOPA allows for transmission of bursty traffic with density up to 97% while DRA and EDFA are limited to 30% and 15%, respectively. Alternatively, we demonstrate PI-FOPA to allow for 3 dB and 5 dB higher power budget than the DRA and EDFA, respectively, for the worst case scenario of 75% traffic density.

Ultra‐compact tunable fiber laser for coherent anti‐Stokes Raman imaging

AbstractThis work describes the construction of an ultra‐compact narrowband fiber laser source for coherent anti‐Stokes Raman scattering microscopy of Raman tags, that is, for addressing Raman resonances of deuterated molecules and alkyne tags in the spectral range from 2080 to 2220 cm−1. A narrowband and fast electronically tunable cw seed source based on a semiconductor optical amplifier (SOA) emitting around 1335 nm has been employed to seed four‐wave mixing (FWM) in an endlessly single mode fiber (ESM) pumped by a ps pulse duration Yb‐fiber laser. A conversion efficiency of 50% is demonstrated. This compact fiber optical parametric amplifier (FOPA) has been used to perform coherent anti‐Stokes Raman imaging experiments of crystalline deuterated palmitic acid.

Dual-band fiber optical parametric amplification in a structure of highly nonlinear photonic crystal fiber

We investigate fiber optical parametric amplification (FOPA) in a structure of an As2S3 core and TeO2 cladding photonic crystal fiber (PCF). Various amplification features such as wavelength area, parametric gain value, and bandwidth are investigated. In order to design the FOPA system with optimal features, effects of different structural parameters variation on optical features of the PCF and parametric gain subsequently are also investigated numerically based on the finite-difference time domain numerical method. Using 15 cm of this fiber and a continuous wave pump laser of 1.1 W, we attain a gain spectrum of 350 nm with a maximum value of 37 dB around 1550 and 1310 nm, which are favored wavelengths in optical telecommunication systems. In fact, our structure ends in a wideband amplifier in an absolutely compact size, which is optimized exactly for optical telecommunication applications.

Dual pump broadband fiber-optic parametric amplifier based on near-zero dispersion photonic crystal fiber with single zero dispersion wavelength

A broadband fiber-optic parametric amplifier (FOPA) based on near-zero dispersion profile with single zero dispersion wavelength (ZDW) by selective liquid infiltration technique is numerically investigated. Here, the gain and bandwidth for an FOPA incorporating “dual pumping” scheme are thoroughly investigated by varying the fiber length, operating wavelength (central wavelength), and pump power. The structure is engineered in such a way that the dispersion profile is having near-zero dispersion value (negative β2) for a wide wavelength range and small positive β4 around the pump wavelength; thereby, the phase mismatch term remains within the favorable value for a wide wavelength leading to wider FOPA sources. The structure also supports reasonable high nonlinearity and low propagation loss. Our numerical investigation results in an FOPA with optimized bandwidth of around 180 nm close to communication wavelength. Finally, a detailed comparative study of the single pump scheme and dual pump scheme for FOPA/amplifier gain and spectrum bandwidth has been performed for identical fiber parameters. It has been observed that dual pump scheme provides smoother/flatter spectrum (lesser gain fluctuation) around the center of the optimized profile with slightly lesser bandwidth compared to single pump operation. Additionally, it was observed that the dual pump FOPA supports higher pump power thereby enabling higher FOPA unaltered peak gain (3 dB) throughout the bandwidth (the peak and dip of the gain spectrum difference remaining within 3 dB) than that of single pump scheme.

Raman Assisted Fiber Optical Parametric Amplifier for S-Band Multichannel Transmission System

In this paper we present results from the study of optical signal amplification using Raman assisted fiber optical parametric amplifier with considerable benefits for S-band telecommunication systems where the use of widely used erbium-doped fiber amplifier is limited. We have created detailed models and performed computer simulations of combined Raman and fiber optical parametric amplification in a 16-channel 40 Gbps/channel wavelength division multiplexed transmission system. Achieved gain bandwidth, as well as transmission system parameters—signal-to-noise ratio and bit-error-ratio—were analyzed by comparing the Raman assisted fiber optical parametric amplifier to the single pump fiber optical parametric amplifier. Results show that the 3 dB gain bandwidth in the case of combined amplification is up to 0.2 THz wider with 1.9 dB difference between the lowest and highest gain.

Gain-saturated two-pump fiber optical parametric amplifiers in the presence of dispersion fluctuation and fourth-order dispersion coefficient

The saturated gain performance of the two-pump fiber optical parametric amplifier (2-P FOPA) in the presence of random dispersion fluctuation as well as fourth-order dispersion coefficient are investigated. The gain spectra of the 2-P FOPA is simulated by solving the coupled equations numerically, considering the dispersion fluctuations along the fiber as a stochastic process with a given standard deviation and correlation length. The gain performance of 2-P FOPA is analysed with the variation of correlation length, standard deviation and fourth-order dispersion coefficient, respectively. It shows that, the gain saturation curves of 2-P FOPA exhibit obvious differences in the presence of dispersion fluctuations and fourth-order dispersion coefficients. The peak gain reduces with the increase of the standard deviation and the reduction is higher in case of shorter correlation lengths, also the variations of 2-P FOPA saturation powers are affected by the standard deviation and correlation length significantly. In addition, the performance of the 2-P FOPA varies greatly while considering the fourth-order dispersion coefficient, where the peak gain remains the same, but the 3 dB bandwidth is wider with considering the fourth-order dispersion coefficient. The numerical analysis is meaningful for the research of 2-P FOPA saturated gain performance, which having attracted great research interests in the optical fiber communication systems.

Cascaded Fiber Optical Parametric Amplifier with Dispersion Compensation Fiber

Cascaded Fiber Optical Parametric Amplifier with Dispersion Compensation Fiber

Implementation of Multi-Wavelength Source for DWDM-PON Fiber Optical Transmission Systems

Abstract Four-wave mixing (FWM) is one of the well-known nonlinear optical effects (NOE), and it is considered as an adverse impact in fibre optical communication lines. This nonlinear optical effect as a productive one can be used in fibre optical communication systems for various optical processing functions, like wavelength conversion, high-speed time-division multiplexing (TDM), pulse compression, fibre optical parametric amplifiers (FOPA), etc. In most of the fibre optical communication systems, each data transmission channel requires one light source (e.g., laser) as a carrier, which can make these transmission systems expensive. For example, to provide operation of 4-channel dense wavelength-division-multiplexed (DWDM) system four separate lasers at specific operation wavelengths are needed. On the contrary, through the FWM effect, which can be obtained in highly nonlinear optical fibre (HNLF) by using two high-power pump lasers, the generation of new multiple carriers forming the laser array or a multi-wavelength source is possible. Accordingly, within the present research, we investigate the latter approach for FWM light source implementation in DWDM passive optical networks (DWDM-PONs). We analyse up to 16-channel 50 GHz spaced DWDM-PON system with a bitrate of up to 10 Gbit/s per channel, constructed on the basis of two high-power continuous wave (CW) pump lasers. We evaluate the system performance against the number of its channels by changing it from 4 to 16 and in each case find the most optimal HNLF fibre length (for a 4-channel system it is 0.9 km; for an 8-channel system – 1.39 km; and for a 16-channel system – 1.05 km) and laser pump powers (for a 4-channel system it is 20 dBm; for an 8-channel system – 24.1 dBm; and for a 16-channel system – 26.3 dBm). These optimal parameters were found in order to get the highest system performance, respectively, the lowest BER (threshold BER≤10−10), and minimal power fluctuations among FWM generated carriers. The obtained results show that the proposed transmission system can be a promising solution for next-generation high-speed PONs.

Influence of chirped pump shape on the two-pump fiber optical parametric amplification

The gain performance of two-pump fiber optical parametric amplifier (FOPA) pumped by different kinds of chirped pump pulses is investigated numerically. It shows that the gain performances of FOPA are evidently influenced by the shapes of chirped pump pulses. The highest and broadest gain spectrum is obtained with the 10th-order super-Gaussian pulse in case of identical energy and full width at half-maximum of the pump pulses. Finally, the signal gain is also affected by the poor symmetry of pump pulse, which leads to a low gain performance.

Enhanced analog-optical link performance with noiseless phase-sensitive fiber optical parametric amplifiers.

In this paper, we investigate the enhancement of analog optical link performance with noiseless phase-sensitive fiber optical parametric amplifiers. The influence of different noise sources in the link impacts the quality of analog optical signals, especially with low optical signal power, which has not been investigated before. Theoretically, the increase in signal-to-noise ratio and spurious-free dynamic range can be up to ∼6 dB and ∼4 dB, respectively, if the noise figure of optical pre-amplifier drops 3 dB when the received optical power is less than -65 dBm. In addition, experiments based on a 1.3 dB-noise-figure phase-sensitive fiber optical parametric amplifier and conventional optical pre-amplifiers are implemented, and the measured results agree with the theoretical expectations. This illustrates that noiseless phase-sensitive optical amplification may pave the way to long-haul distribution of analog optical signals and find applications in microwave-photonic systems.

One-Pump Phase Sensitive Fiber Optical Parametric Amplifier With Dual-Core Fiber

The gain performance of one pump phase sensitive fiber optical parametric amplifier (PS-FOPA) in the dual-core fiber is numerically investigated without pump depleting. The effects of the core coupling coefficient(C), the pump wavelength and the initial signal phase on the gain of PS-FOPA are analyzed in detail. It shows that, the signal gain is greatly affected by different core coupling coefficients, and a flatter gain is achieved with suitable C value. Also, when the pump wavelength is greater than the zero-dispersion wavelength (ZDW), both the peak gain and gain bandwidth decrease with the increase of C, but the trend is opposite in case of the pump wavelength less than the ZDW. Additionally, the flatter and broader gain spectra are obtained by adjusting the initial signal phase in core 2. This simulation provides a detail analysis for the dual-core PS-FOPA, which is significant for the all optical fiber amplifier systems.

Experimental comparison of fiber optic parametric, Raman and erbium amplifiers for burst traffic for extended reach PONs.

We experimentally compare the performance of a polarization-independent fiber optic parametric amplifier (FOPA), a discrete Raman amplifier and a commercial erbium doped fiber amplifier (EDFA) for burst traffic amplification in extended reach passive optical networks (PON). We demonstrate that EDFA and Raman amplifiers suffer from severe transient effects, causing penalty on receiver sensitivity >5 dB for traffic bursts of 10 Gbps on-off keying signal shorter than 10 µs. On the other hand, we demonstrate that FOPA does not introduce a penalty on receiver sensitivity when amplifying signal bursts as short as 5 µs as compared to a non-burst signal. Therefore, FOPA used as a drop-in replacement for an EDFA or Raman amplifier allows us to improve receiver sensitivity by >3 dB for short signal bursts. We conclude that FOPA allows substantially increased power budget for an extended reach PON transmitting variable duration bursts. In addition, we identify the maximum burst duration tolerated by each examined amplifier.

Design guidelines for normal-dispersion fiber optical parametric chirped-pulse amplifiers.

We theoretically investigate methods of controlling pulse generation in normal-dispersion fiber optical parametric chirped-pulse amplifiers. We focus on high-energy, ultrashort pulses at wavelengths widely separated from that of the pump, and find that within this regime, a number of simple properties describe the essential phase and gain dynamics. Of primary importance are the relationships between the chirps of the pump, seed, and parametric gain, which we theoretically predict and then experimentally validate. By properly arranging these parameters, the signal and idler waves can be widely customized to fulfill a remarkable range of application requirements, spanning from narrowband to few-cycle.

Raman-amplified pump and its use for parametric amplification and phase conjugation

Abstract We experimentally demonstrate the use of a discrete Raman amplifier for generating a high power, narrow linewidth pump for use within a fiber optical parametric amplifier (FOPA). We demonstrate the suitability of the Raman-amplified pump for parametric amplification by characterizing its optical signal to noise ratio and relative intensity noise (RIN). The amplified pump is subsequently employed within a FOPA obtaining net gain of up to 24.9 dB and a gain of >11 dB over 35 nm. The approach described here offers the key advantage over traditional EDFA-based pump generation of wavelength tuneability outside the EDFA bands. In principle this allows to place the parametric pump at any wavelength within the low fiber attenuation window. Here we additionally demonstrate Raman-assisted optical phase conjugation to provide positive conversion efficiency over 60 nm whilst employing the phase-conjugating pump power of

Enhanced slow and fast light in strong dispersion region of the Raman assisted narrow band fiber optical parametric amplifier

Narrow band fiber optical parametric amplifier with normal second order dispersion is deemed as a potential approach to delay the wide band signal in future optical telecommunication. Due to the combined effect of Raman and four-wave mixing, the slow and fast light is complex in this case. By considering both the real and imaginary part of the Raman susceptibility, two formulas for the phase shift and delay time in the stimulated Raman scattering assisted fiber optical parametric amplifier are presented. The wavelengths with maximum delay and advanced time are calculated numerically. Then we find some narrow frequency regions with the enhanced slow and fast light in both stokes and anti-stokes wave regions, which is the result of strong dispersion generated by the interaction between the stimulated Raman scattering and four-wave-fixing effect at the strong absorption region. In a narrow frequency region around the wavelength with maximum delay or advanced time, the case with low pump power and longer fiber can generate large delay(advanced) time if the signal wave has low bandwidth. Meanwhile, the delay or advanced times in these regions are sensitive to the signal wavelength due to the drastic change of the delay time spectrum. Simulation shows that the delay or advanced time will drop with the signal bandwidth. The time difference between two 1 GHz signal waves with 0.02 nm wavelength separation can reach 290ps in the Raman enhanced slow light region when we employ 2.4W pump power and 1km NZ-DSF. These features of enhanced slow and fast light in the interaction between the stimulated Raman scattering and four wave mixing effect has the potential to be applied in the optical signal processing.

Phase Preserving Amplitude Saturation Through Tone Synthesis Assisted Saturated Four-Wave Mixing

When processing a data carrying signal with amplitude saturation in a fibre-optic parametric amplifier, the signal can be subject to a deleterious conversion of its amplitude noise into phase noise. To overcome this, we propose and demonstrate a scheme in which the products of four-wave mixing are instead synthesised using spectral shaping of multicast replicas of the signal, rather than naturally through four-wave mixing itself. This allows us to emulate the advancement of four-wave mixing without incurring unwanted amplitude noise to phase noise conversion. A final stage of four-wave mixing is used to bring about amplitude squeezing, with little impact on the phase noise of the signal. Using this technique, we are able to demonstrate phase preserving amplitude squeezing of a 10 GBd QPSK signal using as a medium, a highly nonlinear fibre in which the traditional, single pump approach fails.

Impact of Random Dispersion Fluctuations on Two-Pump Fiber Optical Parametric Amplifier Performances

The impact of random dispersion fluctuations on two-pump (2-P) fiber optical parametric amplifier (FOPA) performance in terms of parametric gain, 3-dB amplification bandwidth and saturation power is numerically investigated. The four-coupled amplitude equations which represent the parametric process in optical fiber are solved using the Runge-Kutta method. Based on the results, it was observed that the random dispersion fluctuations reduced the parametric gain, increased the saturation power and had no significant effect on 3-dB amplification bandwidth. The resulted behaviors are mainly due to the changes of phase-matching condition in optical fiber. All in all, the random dispersion fluctuations are potentially limited the 2-P FOPA performances.

Pulsed entanglement measured by parametric amplifier assisted homodyne detection.

Balanced homodyne detection relies on a beam splitter to superpose the weak signal input and strong local oscillator. However, recent investigation shows that a high gain phase sensitive amplifier (PSA) can be viewed as homodyne detector, in which the strong pump of PSA serves as the local oscillator [1]. Here, we analyze a new method of measuring the continuous variable entanglement by assisting a balanced homodyne detector with the PSA and implement it experimentally. Before measuring quadrature amplitude with the balanced homodyne detectors, two entangled fields generated from a pulse pumped fiber optical parametric amplifier are simultaneously coupled into the PSA. We find that the normalized noise for both the difference and sum of the quadrature amplitudes of the two entangled fields fall below the shot noise limit by about 4.6 dB, which is the record degree of entanglement measured in optical fiber systems. The experimental results illustrate that the advantages of the new measurement method include but not limit to tolerance to detection loss and characterizing entanglement with only one homodyne detector. The influence of mode-mismatching due to multi-mode property of entanglement on the measured noise reduction can also be greatly mitigated, indicating the new method is advantageous over the traditional measurement in multi-mode case.

Impact of the Four-Sideband and Two-Sideband Theories in Designing of Fiber Optical Parametric Amplifiers

In this paper, we seek to compare the two design theories for fiber optical parametric amplifier through simulation. The two-sideband method (standard method) has been the most widely used method in fiber optical parametric amplifier design, but it does not predict the gain shrinkage around the pumps. This technique does not consider the gain shrinking dynamics around the pump(s). The four-sideband analytical technique is an alternative technique for fiber optical parametric amplifier design, and it allows for a simplified investigation of the gain shrinking dynamics around the pump(s) due to the interaction of the various arising high-order idlers within the vicinity of the pump waves. The undertaking in this paper is to present a dual-pump fiber amplifier based on the highly nonlinear fiber and another one based on the photonic crystal fiber and ascertain if gain shrinking affects both FOPAs.