All-optical sampling and magnification based on XPM-induced focusing

Abstract

We theoretically and experimentally investigate the design of an all-optical noiseless magnification and sampling function free from any active gain medium and associated high-power continuous wave pump source. The proposed technique is based on the co-propagation of an arbitrary shaped signal together with an orthogonally polarized intense fast sinusoidal beating within a normally dispersive optical fiber. Basically, the strong nonlinear phase shift induced by the sinusoidal pump beam on the orthogonal weak signal through cross-phase modulation turns the defocusing regime into localized temporal focusing effects.This periodic focusing is then responsible for the generation of a high-repetition-rate temporal comb upon the incident signal whose amplitude is directly proportional to its initial shape. This internal redistribution of energy leads to a simultaneous sampling and magnification of the signal intensity profile. This process allows us to experimentally demonstrate a 40-GHz sampling operation as well as an 8-dB magnification of an arbitrary shaped nanosecond signal around 1550 nm in a 5-km long normally dispersive fiber. The experimental observations are in quantitative agreement with numerical and theoretical analysis.In modern photonic systems, the sampling process has widespread applications in the fields of optical communications, metrology, clocking, sensing, spectral comb or arbitrary waveform generation.In this context, nonlinear effects have been demonstrated as potential key technologies to develop alloptical sampling devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14] . In most of these techniques, an ultrashort pulse train acts as an optical gate and the basic physical phenomena under use include four-wave mixing (FWM) 10 , cross-phase modulation (XPM) 11 , nonlinear polarization rotation 13 and Raman soliton self-frequency shifting 14 . On the other hand, signal amplification is also a critical function in many area of physics. Basically, optical amplification process refers to multiply an incident signal by increasing its global energy through an active gain medium pumped by an external pump beam. The large range of current and mature amplification techniques at telecommunication wavelengths involves Erbium doped fiber amplifiers, Raman-based amplifiers,

Linear sampling and magnification technique based on phase modulators and dispersive elements: The temporal lenticular lens

“…Inspired by a previous nonlinear sampler where Kerr nonlinearity and dispersion act simultaneously and adiabatically in a km-long fiber [10], here we proposed a new linear implementation where tailoring of the temporal and spectral phase profiles are achieved independently by use of compact devices. Moreover, our new implementation has relaxed the need of an external optical high power sampling beam while the use of a programmable spectral shaper offers flexibility to find the optimum operating parameters according to the frequency and amplitude of the temporal phase modulation.…”

“…Compared to our previous work of ref. [10], the use of the PM offers significant advantages in terms of stability and controllability and does not require to involve any high power pulsed wave that has to be polarization multiplexed. The parabolic spectral phase is imprinted on the signal thanks to a liquid-crystal on silicium programmable filter [24] (Finisar Waveshaper device).…”

“…In a recent work, we have suggested and experimentally demonstrated an all-fibered sampling technique based on the XPM induced by a sinusoidal pump beam on the signal under test (SUT) combined to a simultaneous adiabatic compensation through normal chromatic dispersion [10]. In this configuration, the SUT experiences periodic local compression, leading to an efficient sampling and magnification of its waveform.…”

“…Note that in contrast to our preceding work published in ref. [10] and for which the regime of chromatic dispersion had to be normal, here it can be chosen either anomalous or normal.…”

“…More recently, an alternative nonlinear approach has been experimentally demonstrated at a sampling rate of 40 GHz, whilst providing a simultaneous 8-dB magnification factor of the waveform [10]. Basically, during its co-propagation in a km-long fiber with a high-power sinusoidal pump beam, the waveform under test experiences a strong temporal phase modulation due to the XPM coupling.…”