We demonstrate a fully automated polarization-insensitive fiber optical parametric amplifier (PI-FOPA) self-adjusting its parameters to compensate for drifts in real-time. The automation algorithm adjusts the PI-FOPA parameters to set and maintain the target polarization independent gain for a selected channel. We employ this PI-FOPA in a long-reach access network scenario to simultaneously amplify WDM downstream in the C band and WDM upstream in the L band, whereas the downstream and the upstream are equivalent to 10x 100 Gbit/s polarization-division multiplexed QPSK signals and 10x bursty 10 Gbit/s on-off keying signals respectively. The PI-FOPA provides net gain >17dB across all channels and the total output signal power up to 24.6 dBm. This demonstration denotes the first ever simultaneous amplification of WDM signals by a PI-FOPA in C&L bands and on both sides of the PI-FOPA pump.

We present our recent achievements with polarisation-insensitive fibre optical parametric amplifiers (PI-FOPAs) for optical communications.We have demonstrated a robust fully automated (black-box) PI-FOPA operation in the C and L bands simultaneously with gain of ~20dB and output power over 23dBm when amplifying polarisation-multiplexed WDM QAM signals and a bursty traffic.Additionally, we have demonstrated a PI-FOPA to amplify WDM signals in the S band and across a continuous bandwidth of 40nm.Finally, we have demonstrated a power budget improvement of a transient-sensitive link by up to 8 dB when employing a PI-FOPA with noise figure of ~6 dB as a drop-in replacement of an EDFA.

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.

We demonstrate a polarization insensitive fiber optic parametric amplifier to provide net gain > 10dB and polarization dependent gain <1dB for up to 19 WDM channels in the range 1508- 1530nm. © 2022 The Author(s)

We experimentally demonstrate all-optical wavelength conversion with efficiency above -5 dB from any wavelength to any other wavelength across a whole of the C band by employing two narrow-linewidth pumps in Al-doped HNLF.

A dither-free polarization insensitive optical phase conjugate is generated in Al-doped HNLF with two orthogonally polarized pumps of 2 W each. Approximately 15nm OPC wavelength tunability is obtained with a conversion efficiency > -5 dB.

In this paper we experimentally show parametric amplification and wavelength conversion in a custom manufactured dual-core highly nonlinear fiber. On-off gain $>$ 10 dB and conversion efficiencies between $-1$ and $-8.5$ dB were measured for both cores. The estimated effective nonlinear parameter for the cores of the fiber are 6.6 W $^{-1}\mathrm{km}^{-1}$ and 6.3 W $^{-1}\mathrm{km}^{-1}$ , while the zero-dispersion wavelength for the individual cores is shown to be relatively close from each other. Furthermore, complementary analytical and numerical results show that coupled cores fiber optical parametric amplifier offer the potential of wide-band gain even when they have significantly distinct zero-dispersion wavelengths.

All-optical wavelength conversion of dual-polarization signals over 9.6 nm in C+L-band is demonstrated in a twin-core highly nonlinear fibre for the first time. Conversion efficiencies between -1 dB and -8.5 dB for both cores are obtained simultaneously.

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.

We demonstrate, for the first time, a real-time stabilized polarization-insensitive fiber optic parametric amplifier to simultaneously amplify WDM C&L band traffic in an extended-reach PON scenario with gain >17dB and output power >23 dBm.

We experimentally find a practical stimulated Brillouin scattering (SBS) threshold for broadband high-performance fiber optical parametric devices relying on dispersion-stable GeO2-doped silica highly nonlinear fibers. We demonstrate that SBS limits the nonlinear phase shift in such fibers to ~0.3 rad per pump unless the SBS is mitigated in some way. We consequently derive corresponding limits on signal gain and conversion efficiency and find the required SBS mitigation factor for a range of fiber optic parametric devices' applications. Finally, we examine the level of SBS mitigation using air gaps and fiber tapers for implementation in polarization-insensitive fiber optic parametric devices employing bidirectional loops. We observe that an air gap or fiber taper are not very efficient for SBS mitigation as they provided an increase in SBS threshold up to 0.7 dB attributed primarily to their excess loss.

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.

We experimentally demonstrate a polarisation-insensitive fibre optic parametric amplifier (PI-FOPA) with the record wide gain bandwidth of 35 nm. We employ the PI-FOPA to amplify the full C- band equivalent 42x100GHz-spaced channels with net gain >10 dB and polarisation-dependent gain <0.5 dB in the wavelength range between 1580 nm and 1615 nm.

Several polarization-insensitive configurations for single-pump phase-insensitive fiber optical parametric amplifier are experimentally evaluated using 35GBaud PDM-QPSK signals. An equivalent noise figure of 9.1±1dB is experimentally derived by comparison with a variable noise figure EDFA.

We employ a polarisation-insensitive fibre optical parametric amplifier (PI-FOPA) to demonstrate a dual-band bi-directional 50-km reach symmetric 10G-PON link with a splitter power budget of 14dB. The PI-FOPA provides >16dB gain for a bursty upstream and non-burst downstream signals at 1533nm and 1586nnm respectively.

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.

Gaussian distribution of nonlinear inter-channel crosstalk noise is numerically shown in fiber optical parametric amplifiers with over 16 dB gain. Confidence of signal-to-crosstalk power ratio measurements is justified by consistency with error vector magnitude calculations.