J. Hauden

Ferroelectric domain inversion by electron beam on LiNbO3 and Ti:LiNbO3

Periodically poled titanium in-diffused lithium niobate (Ti:LiNbO3) seems to be an attractive candidate for applications in the field of integrated optics for wavelength division multiplexed networks it could allow building of polarization-independent devices. In this study, we present the fabrication of reversed ferroelectric domain gratings by direct electron beam writing on both clear LiNbO3 and Ti:LiNbO3. First, a preliminary study was carried out on clear lithium niobate in order to determine the irradiation parameters (voltage, probe current, scanning speed) needed to create inverted ferroelectric domains, and then the same irradiation parameters were used for Ti:LiNbO3. The irradiated patterns were observed after chemical etching using a scanning electron microscope and optical microscopy. HeNe laser diffraction through the samples shows that the irradiation induces a variation of the linear optical refractive index in Ti:LiNbO3 but not in LiNbO3. Moreover, no topographical modification was observe...

Coherent Digital Polarization Diversity Receiver for Real-Time Polarization-Multiplexed QPSK Transmission at 2.8 Gb/s

This letter presents a coherent digital polarization diversity receiver for real-time polarization-multiplexed synchronous quadrature phase-shift keying transmission with distributed feedback lasers at a data rate of 2.8 Gb/s. The tolerance against fast polarization changes and polarization-dependent loss is evaluated for different filter widths in the carrier recovery circuit. The minimum achieved bit-error rate is 3.4 times 10-7.

Modeling and optimization of low chirp LiNbO/sub 3/ Mach-Zehnder modulators with an inverted ferroelectric domain section

Domain inversion under coplanar waveguide electrodes is proposed to improve the frequency-chirping behavior of Z-cut LiNbO/sub 3/ Mach-Zehnder modulators. This is achieved by introducing a phase reversal electrode section in tandem with inverted ferroelectric domains. The method opens the way to broad-band single-drive modulators with predetermined chirp parameter. The experimental results obtained at 10 Gb/s confirm the possibility of lowering the chirp parameter of a Z-cut modulator, while keeping a halfwave voltage lower than 5 V.

PDL-Tolerant Real-time Polarization-Multiplexed QPSK Transmission with Digital Coherent Polarization Diversity Receiver

This paper presents the implementation of a real-time electronic polarization tracking algorithm which enables robust optical polarization-multiplexed synchronous quadrature phase shift keying transmission with DFB lasers. The achieved BER at a data rate of 2.8 Gbit/s is well below the FEC threshold.

Electron-Beam Poling on Ti:LiNbO(3).

The periodic domain inversion by direct electron-beam (EB) bombardment on Ti:LiNbO(3) is presented. Gratings with a 6.6-mum period are achieved. The inverted patterns are observed after chemical etching by use of a scanning electron microscope, and they exhibit a high resolution, as expected. Next, the influence of the EB parameters on the inversion phenomenon is developed for both LiNbO(3) and Ti:LiNbO(3). In this way we can provide an explanation of the phenomenon of domain inversion with an EB, which is not completely understood. Finally, quasi-phase-matched second-harmonic generation is presented in bulk LiNbO(3) by use of a Nd:YAG laser light. These experiments allowed us to achieve the characteristics of the inverted domains along the crystal in particular.

Differential Phase-Shift-Keying Technique-Based Brillouin Echo-Distributed Sensing

In this letter, we experimentally demonstrate Brillouin echoes-based distributed optical fiber sensing with centimeter spatial resolution. It is based on a differential phase-shift-keying technique using a single Mach-Zehnder modulator to generate a pump pulse and a π-phase-shifted pulse with an easy and accurate adjustment of delay. The results are compared to those obtained in standard Brillouin echo-distributed sensing system with two optical modulators and clearly show a resolution of 5 cm in a spliced segment between two fibers by applying a π -phase-shifted pulse of 500 ps.

Dual-drive LiNbO 3 interferometric Mach-Zehnder architecture with extended linear regime for high peak-to-average OFDM-based communication systems

A dual-drive LiNbO(3) architecture modulator with chirp management is proposed and developed offering SFDR > 25 dB in a 1.4 V bias excursion compared to only 0.5 V bias excursion in a conventional Mach-Zehnder electro-optical modulator (MZ-EOM). The architecture effectively extends the linear regime and enables the optical transmission of wireless systems employing orthogonal division multiplexing (OFDM) modulation such as ultra-wide band (UWB) which require high linearity over a broad frequency range due to their high peak-to-average power ratio (PARP). Radio-over-fiber UWB transmission in a passive optical network is experimentally demonstrated employing this technique, exhibiting an enhancement of 2.2 dB in EVM after 57 km SSMF when the dual-drive developed modulator is employed.

Distributed Brillouin Fiber Sensor With Enhanced Sensitivity Based on Anti-Stokes Single-Sideband Suppressed-Carrier Modulation

We demonstrate an alternative technique to reduce pump depletion and to improve sensitivity in the long-range Brillouin optical time-domain analysis (BOTDA) sensor. Our BOTDA system uses an anti-Stokes single-sideband suppressed-carrier modulation technique that balances the pump depletion due to fiber loss. With this technique, we show both numerically and experimentally a great improvement compared to the dual sideband standard technique.

Periodic Anticoupling Structures for Parallel Optical Waveguides on LiNbO

We report the design and the fabrication of an anticoupling structure allowing to bring close waveguides without inducing evanescent coupling between them. This method, inspired from a well-known phenomenon of quantum physics, consists in the introduction of a periodic perturbation of the waveguide structure. The aim is to optimize the relative position of the waveguides to the electrodes so as to increase the electro-optical overlaps, in particular in lithium niobate integrated modulator (LiNbO3).

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We report the fabrication of an integrated LiNbO3 Y-junction synchronized double phase modulator fully packaged for RF-application up to 40 GHz. This optical modulator allows for delivering simultaneously counter-phase high-speed modulation and coupling for two input channels. It was designed for application to fiber-optical parametric amplifier and wavelength converters for suppressing idler spectral broadening and signal gain distortion caused by phase modulation itself. With this component, Idler spectral broadening suppression is experimentally demonstrated over all the parametric gain band of a two-pump parametric amplifier operating in the 1.55-mum region. In addition, we present a useful technique for straightforward and full coupling of the pumps and the signal.