Santiago Tainta

Ultrafast electrooptic dual-comb interferometry

Dual-comb interferometry is a particularly compelling technique that relies on the phase coherence of two laser frequency combs for measuring broadband complex spectra. This method is rapidly advancing the field of optical spectroscopy and empowering new applications, from nonlinear microscopy to laser ranging. Up to now, most dual-comb interferometers were based on modelocked lasers, whose repetition rates have restricted the measurement speed to ~kHz. Here we demonstrate a dual-comb interferometer that is based on electrooptic frequency combs and measures consecutive complex spectra at an ultra-high refresh rate of 25 MHz. These results pave the way for novel scientific and metrology applications of frequency comb generators beyond the realm of molecular spectroscopy, where the measurement of ultrabroadband waveforms is of paramount relevance.

Periodic Time-Domain Modulation for the Electrically Tunable Control of Optical Pulse Train Envelope and Repetition Rate Multiplication

An electrically tunable system for the control of optical pulse sequences is proposed and demonstrated. It is based on the use of an electrooptic modulator for periodic phase modulation followed by a dispersive device to obtain the temporal Talbot effect. The proposed configuration allows for repetition rate multiplication with different multiplication factors and with the simultaneous control of the pulse train envelope by simply changing the electrical signal driving the modulator. Simulated and experimental results for an input optical pulse train of 10 GHz are shown for different multiplication factors and envelope shapes.

WDM compatible and electrically tunable SPE-OCDMA system based on the temporal self-imaging effect

A coding/decoding setup for a spectral phase encoding optical code-division multiple access (SPE-OCDMA) system has been developed. The proposal is based on the temporal self-imaging effect and the use of an easily tunable electro-optic phase modulator to achieve line-by-line coding of the transmitted signal, thus assuring compatibility with WDM techniques. Modulation of the code is performed at the same rate as the data, avoiding the use of high-bandwidth electro-optic modulators. As proof of concept of the technique, experimental results are presented for a back-to-back coder/decoder setup transmitting a 10 GHz unmodulated optical pulse train within an 80 GHz optical window and using 8-chip Hadamard codes.

Temporal self-imaging effect for periodically modulated trains of pulses

In this paper, the mathematical description of the temporal self-imaging effect is studied, focusing on the situation in which the train of pulses to be dispersed has been previously periodically modulated in phase and amplitude. It is demonstrated that, for each input pulse and for some specific values of the chromatic dispersion, a subtrain of optical pulses is generated whose envelope is determined by the Discrete Fourier Transform of the modulating coefficients. The mathematical results are confirmed by simulations of various examples and some limits on the realization of the theory are commented.

Experimental Electrically Reconfigurable Time-Domain Spectral Amplitude Encoding/Decoding in an Optical Code Division Multiple Access System

Abstract An electrically reconfigurable time-domain spectral amplitude encoding/decoding scheme is proposed herein. The setup is based on the concept of temporally pulse shaping dual to spatial arrangements. The transmitter is based on a short pulse source and uses two conjugate dispersive fiber gratings and an electro-optic intensity modulator placed in between. Proof of concept results are shown for an optical pulse train operating at 1.25 Gbps using codes from the Hadamard family with a length of eight chips. The system is electrically reconfigurable, compatible with fiber systems, and permits scalability in the size of the codes by modifying only the modulator velocity.

Spectrally Efficient Phase Encoded Optical CDMA System in Time Domain

A novel WDM-compatible spectrally phase encoded-optical CDMA scheme based on second order dispersion is presented. Proof of concept results are given for a system transmitting at 2.5 Gbps within an 80 GHz optical window.

Optical signal processing with electrooptic modulators and dispersion

A review of the main techniques that have been proposed for temporal processing of optical pulses that are the counterpart of the well-known spatial arrangements will be presented. They are translated to the temporal domain via the space-time duality and implemented with electrooptical phase and amplitude modulators and dispersive devices. We will introduce new variations of the conventional approaches and we will focus on their application to optical communications systems.

Optical Code Division Multiple Access coder/decoder pairs based on temporal optical pulse shaping with fiber Bragg Gratings and electrooptic modulators

This paper presents recent proposals that have been made in the field of optical pulse shaping techniques based on the space-time duality, with an especial attention to their application for the design of encoder/decoder pairs in all-fibre Optical Code Division Multiple Access (OCDMA) systems. Two different proposals are presented, one based on an Optical Fourier Transformer using a dispersive media and the other based on the temporal self-imaging effect. Fiber Bragg Gratings are used as dispersive elements and electro-optic modulators for the amplitude or phase coding, allowing the electrical reconfiguration of the codes. Experimental results, both for coherent and incoherent schemes, are shown for the two systems transmitting at data rates of 1.25 Gbps and 10 Gbps respectively with a fixed codification rate of 10 Gcps and using a subset of the Hadamard codes with a length of 8 chips.

Optical pulse train repetition rate and envelope control based on the optical fourier transform

We propose a scheme for an electrically tunable pulse-train control system based on phase modulation and dispersive elements. Experimental results are shown for different multiplication factors and envelope shapes.

Phase Reconstruction for the Frequency Response Measurement of FBGs

A signal processing algorithm is applied to optical spectral analyzer measurements in order to reconstruct phase response of FBGs from easy-to-obtain module data, so avoiding the use of costly and complex equipment for direct measurement of frequency response. In order to prove validity, reconstructed phase, both in transmission and reflection, is then compared to measures from three different techniques (interferometric, modulation phase-shift, and single-sideband modulation).