Karen Solis-Trapala

Nearly-Ideal Optical Phase Conjugation based Nonlinear Compensation System

A nearly-ideal system design for fiber nonlinearity compensation is experimentally demonstrated showing an unprecedented 10 dB nonlinear threshold improvement in 4×12 Gbaud 16QAM WDM signals. The same results are predicted for a 4×67.25 Gbaud 16QAM 2000 km long transmission.

Optimized WDM Transmission Impairment Mitigation by Multiple Phase Conjugations

Multiple phase conjugations within a transmission-optimized fiber link enable significant nonlinearity cancellation in the wavelength division multiplexed (WDM) systems. In particular, we demonstrate the fiber impairment mitigation of WDM 24×48 Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) signals using 12 optical phase conjugations (OPC). The power excursion and dispersion-tailored transmission line in which the phase conjugations acted periodically, enabled an 8-dB higher nonlinearity threshold for the WDM 1.1-Tb/s DP-QPSK signals. With the nearly perfect nonlinearity cancellation, large input powers per span became available. Under these circumstances, we also present a first approach to the analysis of the impact of multiple phase conjugations in a distributed Raman amplified link. The analysis considers the performance of the experimentally measured OPC subsystem within an optimized transmission line limited only by an amplified spontaneous emission noise. This raw estimate gives insight into the linear noise performance limit of the employed phase conjugator when inserted multiple times in such a transmission system.

Signal power asymmetry tolerance of an optical phase conjugation-based nonlinear compensation system

Nearly perfect nonlinear compensation of 4× 12Gbaud-16QAM WDM signals is experimentally demonstrated to achieve nonlinear threshold improvement greater than 10dB, in which symmetric power evolution is essential. We also numerically investigate Q2-penalty versus power symmetry for varying 4×67.25Gbaud-16QAM WDM transmission distances.

On the Cascadability of All-Optical Wavelength Converter for High-Order QAM Formats

With the evolution to ever more complex modulation formats for optical signals, all-optical wavelength converters offer great benefits to optical networks, thanks to the possibility of translating the wavelength of an optical signal regardless of its data rate or modulation format. To deliver its full advantages over conventional optical-electrical-optical conversion, an all-optical wavelength converter has to possess important features in terms of transparency, bandwidth, and cascadability for practical applications in real systems. In this paper, we review a recent development of an all-optical wavelength converter, which exhibits seamless conversion in the C-band with a low noise figure of 6.2 dB for dual-polarization (DP) phase-modulated signals. We then carry out an investigation by both experiment and calculation of the cascaded operation of the developed wavelength converter for high-order quadrature amplitude modulation (QAM) formats. A cascadability comparable to an erbium-doped fiber amplifier is achieved for DP-QPSK, DP-16QAM, and DP-64QAM signals, thanks to the exemplary characteristics of the wavelength converter.

Multi-tone counter dithering of terabit/s polarization multiplexed signals for enhanced FWM with a single pump

We demonstrate low-noise degenerate four-wave mixing (FWM) of a 24×100Gb/s DP-QPSK signal with a high 50% conversion-efficiency, enabled by counter-phase modulating it and a CW pump at two frequencies. An improved signal Q2-factor by an average of 5.3 dB is achieved.

Low noise frequency comb carriers for 64-QAM via a Brillouin comb amplifier

Optical frequency comb lines with poor carrier to noise ratio (CNR) are significantly improved by Brillouin amplification using its extreme narrow bandwidth gain to suppress out of band noise, enabling higher quality signal modulation. Its application to spectral lines of narrow 10 GHz pitch and poor CNR is shown to suppress the otherwise strong phase distortion caused by poor CNR after encoding with 96 Gb/s DP-64-QAM signals and restore the bit error rate (BER) to below the limit for standard forward error correction (FEC). This is also achieved with the required frequency shifted optical pump for amplification obtained by seeding it from the comb itself, sparing the need for lasers and frequency locking. Simultaneous CNR improvement for 38 comb lines is also achieved with BER restored to below the FEC limit, enabled by a multi-line pump that is pre-dispersed to suppress its spectral distortion from the Kerr effect in the gain medium. Carrier performance at minimum BER shows minimal noise impact from the Brillouin amplifier itself. The results highlight the unique advantage of Brillouin gain for phase sensitive communications in transforming otherwise noisy spectral lines into useful high quality signal carriers.

First demonstration of wavelength conversion of DP-64QAM signal using an improved counter-dithering pump scheme

Wavelength conversion of a 144-Gbit/s DP-64QAM signal is demonstrated for the first time. An improved counter-dithering pump scheme realizes high efficiency and negligible phase noise, resulting in only 1-dB Q-factor penalty at 36-dB output OSNR.

Signal phase regeneration through multiple wave coherent addition enabled by hybrid optical phase squeezer.

A newly proposed concept, which is called hybrid optical phase squeezer (HOPS), achieves multi-level optical phase quantization through coherent addition of two (dual-wave scheme) or three (triple-wave scheme) optical waves exploiting optical parametric processes and electro-optic modulation. The triple-wave scheme enables signal phase regeneration free from phase-to-amplitude noise transfer, which is inevitable in the dual-wave scheme. By using HOPS in the dual-wave scheme, 3-fold phase-noise reduction was achieved for 24-Gb/s QPSK signals with a slight increase of amplitude noise. On the other hand, HOPS in the triple-wave scheme allowed phase regeneration of 12-Gb/s BPSK signal with a suppression of phase-to-amplitude noise transfer.

Tunable Optical Parametric Regenerator Assessment in a 43 Gb/s RZ-DPSK Signal Transmission Link

We study a wavelength-tunable optical parametric regenerator (OPR) demonstrated experimentally by assessing numerically its performance as an inline component of a 43-Gb/s return-to-zero differential phase-shift keying transmission system. The device features wide input wavelength range operation and regenerative wavelength conversion. The improvement in the transmission reach that it provides is predicted by simulations benchmarked against the experimental data. An up to fourfold improvement at a bit error ratio of ~ 10-4 is estimated for a 360-km long regeneration span. We show that the improvement is achieved by a combination of the amplitude regeneration capabilities with the phase noise blocking character of the OPR, despite of the small amount of phase fluctuations induced by the regenerator itself.

Low noise degenerate FWM of 12×100 Gb/s DP-QPSK signals with counter-dithering of pump and idler waves

We demonstrate degenerate four-wave mixing of a 12×100 Gb/s DP-QPSK signal with counter-phase dithering by a phase modulator embedded in a fiber-loop. A ≈9 dB higher conversion efficiency enables an OSNR penalty of 0.7 dB at 10-3 BER.