Synthesis of 1D Bragg gratings by a layer-aggregation method

We present what we believe to be a novel method for the synthesis of complex 1D (fiber and waveguide) Bragg gratings, which is based on an impedance reconstruction layer aggregation technique. The main advantage brought by the method is the possibility of synthesizing structures containing defects or discontinuities of the size of the local period, a feature that is not possible with prior reported methods. In addition, this enhanced spatial resolution allows the synthesis of very strong fiber Bragg grating devices providing convergent solutions. The method directly renders the refractive index profile n(z) as it does not rely on the coupled-mode theory.     

Integrated microwave photonics

Microwave photonics (MWP) is an emerging field in which radio frequency (RF) signals are generated, distributed, processed and analyzed using the strength of photonic techniques. It is a technology that enables various functionalities which are not feasible to achieve only in the microwave domain. A particular aspect that recently gains significant interests is the use of photonic integrated circuit (PIC) technology in the MWP field for enhanced functionalities and robustness as well as the reduction of size, weight, cost and power consumption. This article reviews the recent advances in this emerging field which is dubbed as integrated microwave photonics. Key integrated MWP technologies are reviewed and the prospective of the field is discussed.     

Experimental demonstration of subcarrier multiplexed quantum key distribution system

We provide, to our knowledge, the first experimental demonstration of the feasibility of sending several parallel keys by exploiting the technique of subcarrier multiplexing (SCM) widely employed in microwave photonics. This approach brings several advantages such as high spectral efficiency compatible with the actual secure key rates, the sharing of the optical fainted pulse by all the quantum multiplexed channels reducing the system complexity, and the possibility of upgrading with wavelength division multiplexing in a two-tier scheme, to increase the number of parallel keys. Two independent quantum SCM channels featuring a sifted key rate of 10 Kb/s/channel over a link with quantum bit error rate <2% is reported.     

Metropolitan Optical Networks: When to Change to DWDM

In this article we propose a new methodology to estimate the change in the bandwidth demand in time, mainly in residential areas. The bandwidth demand forecast is a basic aspect to decide the evolution of metropolitan optical networks. The word evolution refers to the necessity of making changes in networks, either by upgrading or replacing different elements that are part of the network. This analysis, along with a technological alternatives analysis, provides the operator the needed information to achieve the appropriate network planning and to make investment decisions.     

Continuous-wave laser properties of 4F3/2?4I13/2 channel in the Nd3+LiNbO3:ZnO non-linear crystal

This work reports for the first time continuous-wave laser action at room temperature around 1.3 7m in Nd³⁺ doped LiNbO₃:ZnO. Optical spectroscopy has been used to determine the main laser characteristics of ⁴F_3/2‘⁴I_13/2 channel, such as emission cross section and excited-state absorption cross section at laser wavelengths. Internal optical losses have been estimated from laser gain experiments. Under non-optimal conditions laser slope efficiencies of 30% have been obtained.     

Continuous wave laser radiation at 693 nm from LiNbO3:ZnO:Nd3+ nonlinear laser crystal

Red laser radiation at 693 nm has been obtained from a LiNbO:ZnO:Nd crystal by self-frequency-doubling its fundamental laser line at 1386 nm. Pumping was achieved by means of a Ti:sapphire laser. In preliminary experiments a red laser power of 2.3 mW has been obtained for a total absorbed pump power of 800 mW. External second-harmonic experiments (1386–693 nm) are used to investigate some basic non-linear properties such as phase-matching angle, angular and thermal acceptances of this process. Received: 21 June 1999 / Revised version: 15 August 1999 / Published online: 30 November 1999     

Double-cavity fiber structures as all optical timing extraction circuits for gigabit networks

In this paper we propose the application of double cavity fiber resonators as timing extraction circuits for gigabit networks. Spectral properties of double cavity fiber resonators, including the spectral enhancement achieved by means of the vemier effectare outlined. We investigate their suitability to obtain low cost all-fiber timing extraction circuits in broadband optical networks where single cavity structures previouslyproposed in the literature cannot be efficiently applied.     

Microwave photonic filters with negative coefficients based on phase inversion in an electro-optic modulator

We report on a novel technical approach to the implementation of photonic rf filters that is based on the pi phase inversion that a rf modulating signal suffers in an electro-optic Mach-Zehnder modulator, which depends on whether the positive or the negative linear slope of the signal's modulation transfer function is employed. Experimental evidence is provided of the implementation of filters with negative coefficients that shows excellent agreement with results predicted by the theory.