Compensation of carrier lifetime in double-pass semiconductor optical amplifiers

Bi-directional light propagation is expected to enable enhanced functionality of all-optical signal processing operations compared to unidirectional approaches. In this work, we report on compensation of slow gain recovery in semiconductor optical amplifiers (SOAs) in a double-pass condition. The unsaturated gain of the employed SOA is increased by 12.6 dB, and the corresponding normalized conjugate output of four-wave mixing is enhanced by 16.3 dB. The theory attributes this efficiency improvement to the unsaturated gain enlargement which, in turn, compensates for the inherently long carrier lifetimes of SOAs by 50%. The saturation output power remains virtually unchanged

2x2 waveguide based thermooptic photonic switch

We demonstrate a waveguide based thermooptic photonic switch with low electric power consumption using polymer material. The buried square core waveguides structure has been adopted for single mode operation at third telecommunication window. The index contrast of the upper cladding and the waveguiding layers is 0.2%, the lateral section of the waveguiding and lower cladding layer is 0.35%. The asymmetrical fabricated switch exhibits very low switching power of 12.26 mW. The crosstalk level of -30 dB for the initial and switching states have been achieved, respectively

Enhanced gain saturation model of non-linear semiconductor optical amplifiers

This study proposes an enhanced gain saturation model of non-linear semiconductor optical amplifiers (SOAs) by incorporating material-dependent gain compression factor. The rate equations are utilised with the extra gain compression term for Indium-Gallium-Arsenide material-based SOA to account for the steep relaxation oscillations behaviour of non-linear SOAs. The proposed gain saturation model is verified with experimental results that showed very good agreements with a mean square error of 0.094

Design and analysis of different optical attocells deployment models for indoor visible light communication system

Visible light communication (VLC) is a promising candidate that is expected to revolutionize indoor environment communications performance and fulfill fifth generation and beyond (5GB) technologies requirements. It offers high and free bandwidth, electromagnetic interference immunity, low-cost front end and low power consumption. Also, VLC has dual functions that could be utilized in both illumination and communication concurrently. The number of optical attocells (OAs) and their deployment in the room represent the main issue that should be taken into consideration in designing an optimal VLC system. In this paper, we have introduced a new model of five OAs in the typical room. In addition to an investigation of various optical attocells (OAs) deployment models, in which a multi-variable evaluation was performed in terms of received power, illumination, SNR and RMS delay spread in order to determine the optimal OAs model. Also, various modulation schemes performances were investigated which included NRZ-OOK, BPSK, and QPSK in order to improve the BER performance. Results indicated that BPSK modulation had superior BER performance when compared with all OAs models. Further, a comprehensive results analysis and comparison of all proposed models was conducted over various parameters, in which our new proposed OAs model achieved an optimal performance in comparison with the other models

Performance analysis of EDFA for SCM/WDM radio over fiber communication link

The radio-over-fiber (RoF) system is one of the potential schemes for the future broadband wireless communication systems such as mobile communications, hotspots and suburban areas. In this paper, we present 16 channels of RF carrier modulation of the Sub Carrier Multiplexing (SCM), which then integrated, with Wavelength Division Multiplexing (WDM) for the Radio over Fibre Link. The integration of the two systems is responding to the demands for high data rate applications and reasonable mobility for broadband communication. The work also investigates the performance of EDFA for the optical fiber length up to 200km. The EDFA introduced as the optical amplifier in the designed system model to encounter the effects of attenuation, distortion and Rayleigh scattering. The deploying of RF carrier performs by double side band and single side band of the SCM for bandwidth utilization shown to be much better than conventional optical WDM. However, by applying EDFA with the length varies from 0m – 5m, the performance show that total power transmission has magnifying the optical signal significantly and the optical fiber length expanded to 150 km. The simulation result has shown that pre-amplifier EDFA in 150km of SCM/WDM RoF system significantly boost the performance of optical signal strength over the link

A ridge waveguide for thermo-optic application

A thermal analysis and structure of a ridge single mode waveguide with a metal heater are presented. The steady-state temperature increases linearly and the thermal response becomes slower at the same power consumption, when the under-etched depth in the lower cladding increases. When the upper cladding thickness decreases, the thermal response becomes faster. This shows that a thinner upper cladding and a deeper etching are preferred to achieve a faster thermal response and lower power consumption, respectively. The numerical simulation also shows the power consumption of the present ridge waveguide is almost third of that for conventional one and the response time is half of that of the conventional one

Fabrication and characterization of polymer thermo-optic switch based on MMI coupler

The 2×2 polymer thermo-optic switch based on MMI coupler is realized. This device is fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of -36.2 dB is achieved at cross and bar states. A power consumption of 1.85 mW is applied to change the state of the switch from the cross to the bar state. A switching time of less than 0.7 ms is traced to change a state of the realized switch

Thermo-optic multimode interference switches with air and silicon trenches

A novel thermo-optic multimode interference (MMI) switch with air and silicon trenches was proposed, and the performance of the switch was simulated. In the design, one heating electrode is used to alter the refractive index at a spot image which changes the phase of this image to realize the switching function. The simulation results clearly indicate that the MMI switch can satisfy −39 dB crosstalk at two states. The electric power consumption for the MMI switch with these trenches is less than half of that of a conventional MMI switch

Low loss 1x2 optical coupler based on cosine s-bend with segmented waveguides

This paper presents an optimization of 1x2 polymer Y-junction optical coupler. The optimized optical coupler comprises straight polymer waveguide as the input waveguide, tapered waveguide, modified cosine S-bend and linear waveguide. At the branching point, N short waveguides with small width are introduced to reduce evanescent field. At operating wavelength of 1550 nm the excess loss of the coupler is ~0.18 dB. In term of polarization dependence loss (PDL), the proposed coupler also shows a good performance with PDL value of less than 0.015 dB for wavelength range of 1470 nm-1550 nm. The proposed coupler could reduce excess loss more than 25% compared to conventional Y junction optical coupler

Capacity improvement of TWDM-PONs exploiting the 16-qam technique for downstream side with a nonlinearity effect study for upstream DML

Currently, the main goal of developing time-wavelength-division multiplexing passive optical networks (TWDM-PONs) is to acquire capacity improvement in a scalable and cost-effective manner. In response to the challenge, this paper demonstrates a full-system TWDM-PON through physical layer simulation that provides 56 Gb/s downstream and 40 Gb/s upstream bandwidths. We propose a simple and cost-effective scheme to improve the capacity of the downstream signal by utilizing highly spectrally efficient 16 quadrature amplitude modulation (QAM) with 20 GHz radio-over-fiber signal distribution using a single sideband signal that is generated by an optical dual-arm modulator. In addition, we study the effect of nonlinearity on a directly modulated laser (DML) as the upstream laser of an optical network unit. The outcomes obtained revealed good transmission quality in both directions, where bit error ratios of 10-6 and 10-5 are obtained for the downstream and upstream transmissions, respectively. This leads to the ability to support up to 128 users over 40 km of single-mode fiber