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We present in this article two secure multiplexing and demul- tiplexing schemes that use homomorphic properties from known public key cryptosystems. One scheme is suitable for cryptosystems with addi- tive homomorphic properties such as Paillier and Benaloh cryptosystems. The proposed scheme employs a modification of Hadamard codes to generate a set of orthogonal codes over Z3. The other one is suitable for cryptosystems with multiplicative homomorphic properties such as RSA and ElGamal. Both schemes might be used in voting and auction systems where anonymity of the individuals is crucial.

In this paper a proof of concept of a switchable erbium doped fiber ring laser (EDFRL) system, demonstrated for temperature sensors multiplexing, was carried out showing a high linearity and a sensitivity of 1.55 GHz/°C. The system is based on the detection in the electrical domain of the resulting beat signal of two different laser lines generated by an EDFRL that operates in single longitudinal mode regime (SLM). The SLM operation is achieved by the use of phase shift fiber Bragg gratings (PSFBGs) with ultra-narrow bandwidths (BW) of 6 pm. Two Independent cavities for the reference signal and sensor signal generation are used to avoid the wavelength competition and to improve the stability. This configuration allows the control of the temperature operation point of the system by adjusting the temperature in the reference side. ; The authors are grateful to the Spanish government project TEC2010-20224-C02, to the Spanish Ministry of Education and Culture, and to the grant AP2009-1403.

This article shows the methodology used to evaluate the linear and non-linear effects present in a radio over fiber system (RoF) by employing the multiplexing technique used for dense wave division, the Dense Wavelength Division Multiplexing (DWDM) technique. It is completed with a dissemination of 50 GHz, in accordance to the standards of the International Telecommunication Union (ITU), through a channel speed of 10 Gbps, at an input power in the optical channel of 30mW, for optical fiber stretches of 40km, 60km and 80km. It presents the modeling of the RoF system graphically through a block diagram by means Matlab, a computational tool, whereby each of the stages of the RoF system are implemented using the libraries offered by the 'simulink' toolbox of Matlab. As a result, it is obtained that the methodology proposed for the evaluation of the RoF system using the DWDM technique allows for the analysis of linear and non-linear effects; where it is observed that the effects that degrade the signal are proportional to the established distances of the optical fiber and that the optical input power used is optimal for the optical fiber to behave as a non-linear medium.

Expanding the functionalities of plasmon-assisted lasers is essential for emergent applications in nanoscience and nanotechnology. Here, we report on a novel ability of plasmonic structures to induce dual-wavelength lasing in the near-infrared region in a Yb 3+ solid-state laser. By means of the effects of disordered plasmonic networks deposited on the surface of a Yb 3+ -doped nonlinear RTP crystal, room-temperature dual-wavelength lasing, with a frequency difference between the lines in the THz range, is realized. The dual-wavelength laser is produced by the simultaneous activation of two lasing channels, namely, an electronic- and a phonon-terminated laser transition. The latter is enabled by the out-of-plane field components that are generated by the plasmonic structures, which excite specific Raman modes. Additionally, multiline radiation at three different wavelengths is demonstrated in the visible spectral region via two self-frequency conversion processes, which occur in the vicinities of the plasmonic structures. The results demonstrate the potential of plasmonic nanostructures for inducing drastic modifications in the operational mode of a solid-state laser and hold promise for applications in a variety of fields, including multiplexing, precise spectroscopies, and THz radiation generation via a simple and cost-effective procedure ; L.S.-G., M.O.R., and L.E.B. gratefully acknowledge support from the Spanish Government under project MAT2016-76106-R and Comunidad de Madrid under grant S2013/MIT-2740. R.S., J.J.C., and F.D. acknowledge funding from the Spanish Government under projects MAT2016-75716-C2-1-R (AEI/FEDER, UE) and TEC2014-55948-R and from Generalitat de Catalunya under project 2017SGR755. L.S.G. acknowledges grant FPU13/02476 from the Spanish Ministry of Education. L.E.B. and M.O.R. also acknowledge financial support from the Spanish Government, through The "María de Maeztu" Programme for Units of Excellence in R&D (MDM-2014-0377)"

In this paper, a theoretical and experimental study of two interferometric sensor multiplexing schemes has been carried out by means of the fast Fourier transform (FFT) analysis. This work addresses one of the main drawbacks of photonic crystal fiber (PCF) sensors, that is, its multiplexing capability. Using a commercial optical interrogator combined with a simple FFT measurement technique, the simultaneous real-time monitoring of several PCF sensors is achieved. A theoretical analysis has been performed where simulations matched with the experimental results. For the experimental verification, highly birefringent (HiBi) fiber sections that operated as sensing elements were multiplexed and tested in two configurations. Due to the FFT analysis, both multiplexing schemes can be properly interrogated by monitoring the FFT phase change at the characteristic spatial-frequency of each sensor. For this purpose a commercial interrogator and a custom Matlab program were used for computing the FFT and for monitoring the FFT phase change in real-time (1 Hz). ; This work was supported by the Spanish Government projects TEC2010-20224-C02-01, TEC2013-47264-C2-2-R, INNOCAMPUS, by the European SUDOE-Interreg Project ECOALMGT and the FEDER funds.

ICT services are a key element of communications and important for socio-economic development. In recognition of the importance of this, the Tanzanian Government started to implement a National ICT Broadband Infrastructure Fibre Optic Backbone (NICTBB) in 2009; this development was planned to be implemented in four phases using an optical dense wavelength division multiplexing (DWDM) network technology in collaboration with the Chinese Government through the Chinese International Telecommunications Construction Corporation (CITCC) under a bilateral agreement. This paper briefly explores the NICTBB network technologies implementation, operations and Internet bandwidth costs. It also provides an in depth assessment of the delivery of ICT services such as e-services and m-services in both urban and rural areas following commissioning of the NICTBB system. Following quantitative and qualitative approaches, the study shows that there have been significant improvements in utilization efficiency, effectiveness and the reliability of the ICT service such as e-services and m-services the NICTCBB was commissioned.

ICT services are a key element of communications and important for socio-economic development. In recognition of the importance of this, the Tanzanian Government started to implement a National ICT Broadband Infrastructure Fibre Optic Backbone (NICTBB) in 2009; this development was planned to be implemented in four phases using an optical dense wavelength division multiplexing (DWDM) network technology in collaboration with the Chinese Government through the Chinese International Telecommunications Construction Corporation (CITCC) under a bilateral agreement. This paper briefly explores the NICTBB network technologies implementation, operations and Internet bandwidth costs. It also provides an in depth assessment of the delivery of ICT services such as e-services and m-services in both urban and rural areas following commissioning of the NICTBB system. Following quantitative and qualitative approaches, the study shows that there have been significant improvements in utilization efficiency, effectiveness and the reliability of the ICT service such as e-services and m-services the NICTCBB was commissioned

Integrated rare-earth-ion-doped dielectric lasers have found numerous applications in the medical, scientific, military and industrial fields, thanks to their high stability, low noise, narrow linewidth emission and broad wavelength tunability. Its favorable optical properties and compatibility with existing silicon waveguide technology make rare-earth-ion-doped aluminum oxide (Al2O3) a very promising gain medium to realize such integrated lasers. Al2O3:Er3+ waveguide lasers are of interest due to their emission near 1.55 μm in the telecommunication C-band. The fabrication of low-loss Al2O3:Er3+ waveguides and internal optical gain over an 80-nm wavelength range with a peak gain of 2.0 dB/cm enabled the realization of various integrated Al2O3:Er3+ lasers on standard thermally oxidized silicon substrates. We report on the fabrication and performance of optically pumped channel waveguide ring and distributed feedback (DFB) lasers in Al2O3:Er3+. The low threshold ring-cavity lasers provide laser wavelength selection in the range 1530–1557 nm when varying the length of the output coupler from the ring. The DFB lasers exhibit output powers of more than 3 mW with slope efficiencies as high as 6.2% in single-frequency operation at 1545.2 nm with linewidths below 15 kHz. These performance data illustrate the significance of Al2O3:Er3+ as a laser gain medium in dense wavelength division multiplexing in telecommunication networks.

In this paper, a new multipoint optical fiber system for relative humidity measurements based on Sn02-FP (Fabry-Pérot) sensing heads and an optical interrogator as single active device is presented and characterized. The interrogation of the sensing heads is carried out by monitoring the Fast Fourier Transform phase variations of the FP (Fabry-Pérot) interference frequencies. This method allows to multiplex several sensors with different wavelength spacing interference pattern. The sensors operate within a wide humidity range (20%-90% relative humidity) with low crosstalk between them. Five sensing heads have been measured using two different channels of the optical interrogator. The availability of four channels in the interrogator allows to multiplex a higher number of sensors, reducing proportionally the cost of each sensing point. ; The authors thank the Spanish Government projects TEC 2013-47264-C2-2-R, TEC2016-76021-C2-1-R, TEC2013- 43679-R Innocampus and the INTERREG SUDOE Project SOE3/P2/P714 as well as to the FEDER Funds.

This work has been supported by the FC-15-GRUPIN14-021 project from the Asturias Regional Government and the CTQ2014- 58826-R project from the Spanish Ministry of Economy and Competitiveness (MINECO, Spain)

The internet is composed of thousands of networks, linking millions of users at academic, industrial and governmental institutions all over the world, offering opportunities to collaborate and to share resources, such as documents, software and data. The ever-increasing number of users confronts the network with an expansion in traffic density, leading to congestion situations during transfer of the data. In addition, future network services which offer an increasing amount of voice and video applications, demand more bandwidth and a high throughput. A cost-effective way to deliver bandwidth is to send multiple wavelengths through a single fibre through an optical network at very high data rates, using a (dense) wavelength-division multiplexing technology that operates in the 1550 nm wavelength window. Considering this context, packet switched all-optical networks not only offer much higher bandwidths than electronic networks due to their ultrafast serial processing, but they also provide for protocol heterogeneity (i.e. transparency of transport layer). In realizing such a network, the following requirements must be met. Optical buffering and contention within the network must be avoided, trading in bandwidth must minimize processing and electronic bottlenecks must be overcome by pushing all electronics to the periphery of the network. An integral part of an optical communication node is a wavelength routing mechanism, sorting optical packets along three dimensions: space, time and wavelength. This paper outlines the basis ideas of a Kohonen self-organizing feature map controlled all-optical router system, providing optimal paths between users without suffering contention problems.

In this paper, a 50 Km remote and switchable fiber optic sensing system based on an erbium doped fiber ring laser is proposed. The system allows the integration of different interrogation methods based on the detection of wavelength or amplitude variations of the laser. This integration is carried out by sequentially activating different ring cavities by using an optical switch. With this scheme, the maximum gain zone of the erbium doped fiber amplifier can be used to increase the distance of the sensor system. A bending intensity sensor and a FBG based strain sensor were successfully tested for high and low-strain measurements respectively. This system includes all the active elements inside the monitoring station, enabling the remote monitoring of the sensors. ; The authors are grateful to the Spanish government project TEC2010-20224-C02, to the Spanish Ministry of Education and Culture, and to the grant AP2009-1403.