All-optical Phase Regeneration Research Articles

Towards a photonic integrated all-optical phase regenerator.

All-optical phase regeneration aims at restoring the phase information of coherently encoded data signals directly in the optical domain so as to compensate for phase distortions caused by transceiver imperfections and nonlinear impairments along the transmission link. Although it was proposed two decades ago, all-optical phase regeneration has not been seen in realistic networks to date, mainly because this technique entails complex bulk modules and relies on high-precision phase sensitive nonlinear dynamics, both of which are adverse to field deployment. Here, we demonstrate a new, to the best of our knowledge, architecture to implement all-optical phase regeneration using integrated photonic devices. In particular, we realize quadrature phase quantization by exploring the phase-sensitive parametric wave mixing within on-chip silicon waveguides, while multiple coherent pump laser tones are provided by a chip-scale micro-cavity Kerr frequency comb. Multi-channel all-optical phase regeneration is experimentally demonstrated for 40 Gbps QPSK data, achieving the best SNR improvement of more than 6 dB. Our study showcases a promising avenue to enable the practical implementation of all-optical phase regeneration in realistic long-distance fiber transmission networks.

Phase Regeneration of QPSK Signals Based on Kerr Soliton Combs

We demonstrate a phase-sensitive and amplification-based all-optical phase regenerator by utilizing on-chip Kerr soliton combs. In the experiment, we demonstrate the direct generation of a Kerr soliton comb in a silicon nitride micro-ring at the receiver side of optical communication systems by applying the transmitted signal as a pump light. The mutual coherence between the signal and the regenerated Kerr comb is excellent, and the all-optical phase regeneration of a 20 GBaud/s QPSK signal is achieved. In contrast to the traditional scheme, our solution shows better SWaP (size, weight, and power) factors. Our study will enhance the relay and reception performance of all-optical communication systems.

All-optical simultaneous amplitude and phase regeneration for MPSK signal with ASE noise based on two-wave PSA

A phase sensitive amplification (PSA) regeneration model for M-ary phase shift keying (MPSK) signals with amplified spontaneous emission (ASE) noise based on the interference between signal and its (M+1)th harmonic is proposed. Compared with the existing models based on different combinations of signal and harmonics, the new regeneration model is optimal in theory to deal with the MPSK signal degraded by ASE noise. The QPSK format is taken as an example for simulation verification and two existing classic models are also performed with the same parameters for comparison. The regeneration performance is evaluated by input–output constellations, phase and amplitude regeneration factors, and the relay distance at the bit error rate (BER) of 3.8×10−3 by measuring the transmission reach after the regenerator. The results show that the new model has the optimal relay performance for ASE-noise MPSK format, which is promising to be applied in large-capacity, flexible, and reliable optical transport networks.

All-optical phase regeneration for DP-QPSK/8PSK signals based on dual-conjugate pump degenerate phase sensitive amplification

An all-optical phase regeneration scheme for advanced modulated signals is proposed using dual-conjugate pump degenerate phase sensitive amplification. By engineered placement of the pump and signal wavelengths as well as the reduction of required conjugate harmonics’ order, viable phase squeezing of up to eighth-order is achieved. Feasibility of the scheme is verified through theoretical analysis and simulations. Key parameters such as signal-to-idler power ratio are investigated to optimize the phase regeneration performance. Combined with a subsequent phase-preserving amplitude regenerating device, the overall error vector magnitude decreases of regenerated DP-QPSK and DP-8PSK signals are about from 19% to 3% and from 9%. Furthermore, optical signal noise ratio improvements of 1.9 dB and 2.1 dB are achieved for phase noise of 20 degrees and 10 degrees, respectively. This shows the potential of the scheme to recover dual polarization signals’ quality and prolong transmission reach.

空间激光通信网络中的全光相位再生技术

空间激光通信网络中的全光相位再生技术

All-Optical Multi-Level Phase Quantization Based on Phase-Sensitive Amplification With Low-Order Harmonics

A novel scheme is proposed for all-optical multi-level phase quantization by mixing two lower-order harmonics, rather than mixing the signal with its conjugate $(M\,{-}\,1)\text{th}$ harmonic, which is difficult to be generated but necessary for the traditional quantization method. The low-order harmonics used in the proposed scheme are determined as the conjugate $(M/2\,{-}\,1)\text{th}$ and the $(M/2\,{+}\,1)\text{th}$ harmonics for $M=4n$ , or the conjugate $(M/2-2)\text{th}$ and the $(M/2+2)\text{th}$ harmonics for $M=4n+2$ , or the conjugate $[(M\,{-}\,1)/2]\text{th}$ and the $[(M+1)/2]\text{th}$ harmonics for $M=2n+1$ , $n=1,2,3\ldots$ . The simulations show the effectiveness of the scheme for the eight- and nine-level all-optical phase quantization. Furthermore, the application of the scheme to the all-optical phase regeneration is validated. An improved method with two cascading stages is also proposed and validated to achieve a monotonic step-like phase–phase transfer characteristic for the optimized all-optical phase quantization. This proposed scheme provides a new way for multi-level phase quantization and multi-level phase shift keying regeneration to meet the ever increasing demand for the bandwidth in fiber-optic communication.

All-optical simultaneous multichannel quadrature phase shift keying signal regeneration based on phase-sensitive amplification

A scheme is proposed to realize the all-optical phase regeneration of four-channel quadrature phase shift keying (QPSK) signal based on phase-sensitive amplification. By utilizing conjugate pump and common pump in a highly nonlinear optical fiber, degenerate four-wave mixing process is observed, and QPSK signals are regenerated. The number of waves is reduced to decrease the cross talk caused by undesired nonlinear interaction during the coherent superposition process. In addition, to avoid the effect of overlapping frequency, frequency spans between pumps and signals are set to be nonintegral multiples. Optical signal-to-noise ratio improvement is validated by bit error rate measurements. Compared with single-channel regeneration, multichannel regeneration brings 0.4-dB OSNR penalty when the value of BER is 10−3, which shows the cross talk in regeneration process is negligible.

Experimental demonstration of phase-sensitive regeneration of a binary phase-shift keying channel without a phase-locked loop using Brillouin amplification.

All-optical phase regeneration of a binary phase-shift keying signal is demonstrated at 10-30 Gb/s without a phase-locked loop in a phase-sensitive amplification-based system using Brillouin amplification of the idler. The system achieves phase noise reduction of up to 56% and up to 11 dB OSNR gain at 10-5 bit error rate for the 10 Gb/s signal. The system's sensitivity to different parameters and stability is also evaluated.

All-optical Phase Regeneration with Record PSA Extinction Ratio in a Low-birefringence Silicon Germanium Waveguide

We report a low-power continuous wave-pumped phase sensitive amplifier (PSA)-based phase regenerator implemented in a passive silicon-based waveguide. A polarization assisted-PSA, consisting of two orthogonally-polarized pumps and a phase-locked signal copolarized to one of them, was implemented in a low-birefringence silicon germanium (SiGe) waveguide. The strong TE/TM modal symmetry of the waveguide and its large nonlinear coefficient enabled the achievement of an extremely large phase sensitive extinction ratio of approximately 29 dB for a total input power of only 21.3 dBm. This SiGe-based PSA was used to demonstrate phase regeneration on a 20 Gb/s differential phase-shift keying signal, thereby reducing its error vector magnitude and phase error by three and six times respectively and enabling a bit-error ratio improvement of up to 2 dB.

Phase Regeneration of QPSK Signal in SOA Using Single-Stage, Wavelength Converting PSA

We demonstrate, for the first time, all-optical phase regeneration of a quaternary phase shift keying signal through phase sensitive amplification in nonlinear semiconductor optical amplifiers (SOAs), using a scheme only previously demonstrated in highly nonlinear fibre. We make use of a highly tunable phase quantizing scheme to circumvent some of the limitations imposed by the use of SOAs and show that it may function in either a conjugating or nonconjugating manner.

Reducing bit-error rate with optical phase regeneration in multilevel modulation formats

We investigate theoretically the benefits of using all-optical phase regeneration in a long-haul fiber optic link. We also introduce a design for a device capable of phase regeneration without phase-to-amplitude noise conversion. We simulate numerically the bit-error rate of a wavelength division multiplexed optical communication system over many fiber spans with periodic reamplification and compare the results obtained with and without phase regeneration at half the transmission distance when using the new design or an existing design. Depending on the modulation format, our results suggest that all-optical phase regeneration can reduce the bit-error rate by up to two orders of magnitude and that the amplitude preserving design offers a 50% reduction in bit-error rate relative to existing technology.

All-optical phase and amplitude regeneration of return-to-zero differential phase shift keying data

We report a novel implementation of an all-optical rephasing, reshaping, and reamplification differential phase shift keying (DPSK) regenerator. The rephasing is based on converting phase noise into amplitude noise by using an interferometric configuration and then eliminating the amplitude noise by using a semiconductor optical amplifier (SOA). The reshaping is performed using gain competition and gain compression in a saturated SOA. The scheme was tested using 10Gbit/s, 2(23)-1 pseudorandom bit sequence return-to-zero DPSK data. The measurement shows removal of the degraded data error floor with a 6 order-of-magnitude improvement in bit-error rate. The measured negative power penalty is about 4dB. Mathematical analysis shows a reduction in DPSK phase-noise power by half.