All-optical multilevel amplitude regeneration in a single nonlinear optical loop mirror

Abstract

We experimentally demonstrate all-optical amplitude regeneration of 4-level pulse amplitude modulated signals (PAM4) based on a single nonlinear optical loop mirror (NOLM). Four power-plateau regions are achieved using return-to-zero (RZ) pulses of narrow pulse-width, enabling large nonlinear phase shifts within the highly nonlinear fiber (HNLF). We quantify noise suppression characteristics at each amplitude level and obtain an overall EVM improvement of 0.92dB by optimizing input power and distortion strength. A theoretical analysis has been also carried out matching the experimental results and revealing the design characteristics of the regenerator's nonlinear transfer function.

Cascaded Nonlinear-Optical Loop Mirror-Based All-Optical PAM Regenerator

“…Figure 7 depicts the BER improvement achieved at every input SNR points, which confirms the regeneration behavior obtained by the proposed cascaded two-NOLMs subsystem. We observe a 2.69 dB SNR improvement at lg(BER) = −3, 1.69 dB higher than the conventional PAM-4 regenerator [12]. By appropriately designing the structure parameters of two NOLMs in series, we can also obtain a PAM-8 regenerator with = 0.989 and = 0.975, whose optimal WPs correspond to the eighth level (first stage) and the fourth level (second stage), respectively.…”

“…Figure 7 depicts the BER improvement achieved at every input SNR points, which confirms the regeneration behavior obtained by the proposed cascaded two-NOLMs subsystem. We observe a 2.69 dB SNR improvement at lg(BER) = −3, 1.69 dB higher than the conventional PAM-4 regenerator [12]. We also test the bit error rate (BER) versus input SNR when the proposed regenerator located in the middle of the transmission link.…”

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

“…Amplitude regeneration [1]- [3] is an essential member of our developing all-optical signal processing toolkit and, along with phase regeneration [4], [5], phase conjugation [6], [7], harmonic generation [8] and wavelength conversion [9], [10], is an important part of any future all-optical network [11]. There is interest in performing such operations purely in the optical domain owing to the ultra-wide bandwidth, low latency and high energy efficiency that all-optical schemes could offer over optical-electronic-optical (OEO) approaches [12], [13].…”

“…Polarisation multiplexed signals can, however, be supported using a polarisation diversity scheme [20]. Techniques for all-optical regeneration not based on FWM include nonlinear optical loop mirror based approaches for both single [21] and multi-level signals [1], [22], single-level saturation in semiconductor optical amplifiers [23] as well as multi-level regeneration in a Mamyshev regenerator [24].…”

All-Optical Multilevel Amplitude Regeneration Based on Polarization-Orthogonal Continuous-Wave-Light-Assisted Nonlinear-Optical Loop Mirror (PC-NOLM) Subsystem

“…By cascading three-stage NOLMs a high bit rate-160Gb/s all-optical regeneration and de-multiplexing have been experimentally demonstrated, but only working on the simple data format [9]. For those advanced modulated formats, a single NOLM for the 4-level pulse amplitude modulated signal (PAM4) in our previous work [10] and a modified NOLM for the star 8-level quadrature amplitude modulated signal (star-8QAM) [11] have been experimentally achieved. Even for higher constellation orders, i.e.…”