David Izquierdo

Multiple-bit all-optical logic based on cross-gain modulation in a semiconductor optical amplifier

In this paper we have evaluated the non-linear response of a semiconductor optical amplifier (SOA) in terms of Cross Gain Modulation effect (XGM). The different ranges of optical power that make the SOA work as a logic gate have been determined, as well as the optimum relation between inputs to obtain the best response. Taking into account the SOA response, a schematic model for an all-optical 4-input NOR gate using a single SOA has been proposed. Our experimental set-up has been tested with four streams of 10 Gbps RZ data to verify the proper and stable operation of the NOR gate under diverse power levels for each data input. The logic output has been evaluated for different inputs using an optical eye diagram to verify its quality; in addition, the possibility of using the NOR output as the input to other logical semiconductor structures, which would allow to chain multiple gates, has been demonstrated. The concatenation of NOR gates allows to build more complex all-optical devices which will permit the design of advanced mechanisms in the field of transparent networks, such as comparators or look-up tables for switching nodes, without the necessity of optical-electrical conversion.

1Gbps full-duplex links for ultra-dense-WDM 6.25GHz frequency slots in optical metro-access networks

1 Gbps full-duplex optical links for 6.25 GHz ultra dense WDM frequency slots are demonstrated and optimized for cost-effective metro-access networks. The OLT-ONU downlinks are based on 1 Gbps Nyquist-DPSK using MZM and single-detector heterodyne reception obtaining a sensitivity of -52 dBm. The ONU-OLT uplinks are based on 1 Gbps NRZ-DPSK by directly phase modulated DFB and also single-detector heterodyne reception obtaining same sensitivity of -52 dBm. The power budget of full-duplex link is 43 dB. These proposed links can provide service to 16 (32) users at each 100 (200) GHz WDM channel.

Cost-Effective Transceiver Based on an RSOA and a VCSEL for Flexible uDWDM Networks

A cost-effective transceiver for a 1-Gb/s full-duplex ultra-dense wavelength division multiplexing optical link is proposed for flexible metro-access and 5G networks. The transceiver is based on a vertical cavity surface emitting laser, which is used as the local oscillator for a heterodyne receiver and also feeds a phase-modulated reflective semiconductor optical amplifier (RSOA) transmitter. The modulation format used in the RSOA is a nonreturn-to-zero differential binary phase shift keying (DPSK) for the uplink, while the downlink is based on a Nyquist DPSK format. The central frequencies of the links are 2 GHz separated, and both links can be placed inside a 6.25-GHz frequency slot. The sensitivity of this transceiver is -43.5 dBm over a 50-km fiber.

Integrated Multi-Bit All-Optical NOR Gate for High Speed Data Processing

In this paper, we study the use of integrated semiconductor optical amplifiers as the basic building block for larger-scale programmable photonic circuits. Making use of the non-linear response of these devices, we study the performance of 4-bit all-optical NOR gates based on fully integrable components for high speed all-optical look up tables. Feasibility of the proposed architecture is demonstrated by proof-of-concept experiments using both commercially available devices and photonic integrated circuits.

Programmable all-optical logic gates based on semiconductor optical amplifiers

In this paper, we discuss the feasibility of optical programmable logic devices based on non-linear processing with semiconductor optical amplifiers. We report results from the simulation of the architecture of an all-optical 4-bit Look-up Table, which is the basic logic element of larger-scale programmable devices, and experimental results from a proof-of-concept setup using commercially available devices. Experimental work with photonic integrated circuits to assess the feasibility of integration of such architectures is also presented.

Dual-wavelength measurement system for absorbance chemical sensing

A novel compact dual-wavelength measurement system for absorbance chemical sensing incorporating digital lock-in amplifiers is reported. Its main innovation is the introduction of a reference wavelength to correct the possible non-specific optical changes of the system. The performance of the instrumentation has been tested on a laboratory setup and with integrated optical absorbance sensors.

SDN-enabled flexible optical node designs and transceivers for sustainable metro-access networks convergence

The Internet data traffic constant growth caused by the popularization of cloud services, mobile and social networks, is being stressed by the advent of 5G technologies. Hence, architectural changes are required at the underlying networks to support the expected traffic volume growth, whereas providing a highly dynamic connectivity. Cost-effective and energy efficient solutions for flexible network subsystems are required in order to provide future sustainable networks. In this paper, we present flexible optical node designs (ROADM and OXC) and transceivers, remotely managed by a Software Defined Networking (SDN) controller, able to satisfy the requirements of future metro-access networks in support of 5G services. In particular, the overall architecture including both the novel data plane devices and the SDN control plane is discussed.

Survey of Faster-Than-Nyquist for Flexible Passive Optical Networks

The constant growing in traffic demands has driven to look for new methods with which to reduce the occupied bandwidth and efficient use of the optical spectrum. Despite non-orthogonal signalling lead to intersymbolic interference introduction, it can be considered as a promising solution if interference is introduced in a controlled manner. In this paper the modulation scheme called Faster-Than-Nyquist (FTN) is presented for Flexible Passive Optical Networks application. Different ratios of bandwidth reduction vs. power penalty are presented and compared to the Nyquist modulation.

Chirp-based direct phase modulation of VCSELs for cost-effective transceivers

A 2.5  Gb/s differential binary phase-shift keying (DPSK) transmitter based on direct phase modulation of a vertical cavity surface emitting lasers (VCSEL) using its own chirp is proposed. The VCSEL, which has a wavelength of 1539.84 nm, has been characterized both statically and dynamically. The sensitivity of a single photodiode heterodyne receiver using the proposed 2.5  Gb/s VCSEL transmitter is -39.5  dBm. Thus, this transmitter is an extremely cost-effective solution for future access networks.

Four-input NOR gate using cross gain modulation in a single Semiconductor Optical Amplifier

We demonstrate all-optical NOR logic operation of four data signals in one SOA. Exploiting XGM, wavelength multiplexing and optical filtering for signal discrimination, we purpose an implementation in which an all-one optical probe signal is modulated by the optical sum of four different data signals at 10 Gbps each. Data signals act as pump and reduce the gain of the SOA producing on-off keying of the probe and, hence, the NOR behavior. We derive the feasibility of a multiple-bit NOR from a simple XGM setup working at a wide range of pump power by means of a characterization with all-one RZ streams. High-resolution measures of the signals are presented to illustrate nonlinear effects and wavelength management. Signals traces are showed to prove logic functioning and 4-bit gate quality is reported by means of eye diagrams of the output signal for different input powers.