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We present a detailed simulation study on plasmonic-organic hybrid electro-optic modulators based on coupled symmetric or asymmetric plasmonic slots. An electro-optic polymer is exploited as an active material, and the device is compatible with a silicon photonics platform. The proposed device operates at 1550 nm wavelength, typical of data center or long-haul telecommunication systems. The device performance in terms of area, plasmonic losses, optical bandwidth, intrinsic modulation bandwidth and energy dissipation are comparable to already proposed Mach-Zehnder solutions, but with potentially better extinction ratio, coupling losses due to photonic-plasmonic transitions, and flexibility in exploiting, without any performance penalty, asymmetric slots to shift the ON and OFF states bias. Finally, the bias dependence of the modulation chirp is investigated, comparing through and cross-coupling configurations.

In this paper, we present a novel transmission line architecture in thin-film lithium niobate (TFLN) platforms to improve the velocity match between the microwave and the optical wave. Compared to conventional coplanar waveguide (CPW), the microwave index ($n_m$) of the proposed slotted electrodes can be optimized from 2.1 to 3 while maintaining the high modulation efficiency and 50-$\Omega$ impedance match. Equivalent-circuit model analysis and finite-element simulation are performed. The simulated half-wave voltage (V$_\pi$) of 1.2 V and E-O modulation bandwidth greater than 80 GHz is obtained for a 2-cm-long modulator. By utilizing the slotted slow-wave electrode, TFLN Mach-Zehnder modulators with CMOS-compatible operating voltage and 3-dB modulation bandwidth greater than 100 GHz are potentialized.

In this work, a hybrid code division multiplexing (CDM) coding and digital filtering method for optical intensity modulation and direct detection (IM-DD) link is investigated to address multipath interference (MPI) and channel bandwidth limitation. CDM signaling already provides robustness to MPI through suppressing the unsynchronized paths by orthogonal (de)coding. As for digital filtering based on square root raised cosine (SRRC) waveforms, its advantage to IM-DD link includes robustness to channel bandwidth limitation due to pulse shaping. Additionally, matching filters achieve the best orthogonality only when they are synchronized well, thus robustness to MPI can be expected on the basis of CDM. We study the performance of such hybrid coding and filtering method over IM-DD link in the presence of MPI and bandwidth limitations through simulation. This is followed by experimental demonstrations of single point-to-point transmission with capacity at 112 Gbps. BER comparison between CDM only and hybrid filtering and coding method is performed by emulating MPI using a Mach-Zehnder interferometer. Furthermore, bidirectional transmission over a single fiber verifies its performance advantage and demonstrates potentials for reducing implementation costs of end-to-end optical communications.

A new optical frequency shifter is presented. It is based on a double sideband suppressed carrier radio-frequency (RF) modulated optical signal into a Brillouin-assisted filter, which is formed by a Brillouin medium between a pair of optical circulators. The frequency shifting operation is realized by utilizing multiple stimulated Brillouin scattering gain and loss spectra to amplify one of the third-order sidebands but attenuate the other sidebands. The frequency shifter has a simple structure and a high frequency shifted to unwanted frequency component ratio. It also has the ability to realize a very large frequency shift, which is three times the input electrical driving signal frequency. The frequency shifter is experimentally demonstrated with the results showing a 32.53 GHz optical frequency shift of a continuous wave light at 1551.016 nm with over 34 dB difference between the wanted frequency shifted and unwanted frequency components.

We propose and demonstrate a novel method to narrow the linewidth of a laser diode at 1550 nm by an electronics-assisted feedforward path and weak locking to a femtosecond comb line simultaneously. By using a femtosecond comb as an ideal ultranarrow-linewidth optical reference, the laser diode is down converted, and its phase noise is “recorded” by the resulted intermediate frequency tone, which is filtered by a 40-MHz electronic filter. The consequentially introduced electronic delay is designed to match the optical delay, which is experienced by the same laser diode for upconversion. The delay match ensures that the phase noise of laser diode can be counteracted by its former “record” in upconversion and realizes linewidth reduction. As a result, the 20-dB linewidth of final radiation has been measured as 26 kHz, which is 1/35 of that of the laser diode.

The frequency-dependent dispersion impairment of high-speed printed analog traces in next-generation pluggable modules is studied. This frequency dependence is considered for the first time in optical fiber communication systems. Transmission of ultra-broadband electrical signals over such traces dramatically enhances the frequency-dependent dispersion effect. Here, for the first time, an extended model of the ultrabroadband signal transmission that includes this frequency-dependent dispersion effect of the printed analog traces is proposed. Additionally, a novel approach to compensate for this frequency-dependent dispersion impairment is introduced. Inclusive analysis reveals that a significant performance improvement of up to 4 dB is achieved by using the proposed symbol-spaced sampling and reduced-complexity digital signal processing technique.

The atmospheric influence on wave propagation was investigated during the First European South African Transmission ExpeRiment from June 2015 to February 2016. The focus in this article was set on optical turbulence, the main atmospheric factor affecting the position and strength of Laser beams, the performance of electro-optical systems and imaging. Measurements were performed continuously during the campaign on three sites over the northwestern part of False Bay. The optical turbulence measurements include in situ measurements using an ultrasonic anemometer at the Roman Rock Island. Integrated optical turbulence measurements were performed at two sites, over a path of 1.8 km and a long distance path of 8.6 km. The sites may be affected by local effects of the coastal environment. For comparison, the optical turbulence was modeled using micrometeorological parameterization. Additionally, the optical turbulence was determined by simulations using the weather research and forecast model WRF. Simulation results were compared to measurements considering seasonal and meteorological variations. The representativeness of the measurements locations for offshore measurements will be discussed. © 2018 SPIE.

A simple optoelectronic regenerator for differential quadrature phase-shift keying (QPSK) signals is demonstrated. The regenerator consists of two parallel delay interferometers followed by balanced detectors, limiting and driving amplifiers, and a dual-parallel Mach-Zehnder modulator that regenerates noise-suppressed optical QPSK signals. We experimentally show that the regenerator improves the receiver sensitivity by about 8 dB at an input optical signal-to-noise ratio (OSNR) of 19 dB at a signal speed of 10 Gbaud. Numerical simulation is conducted for higher speed operation at 56 Gbaud to study the impact of the bandwidth of electrical circuits inside the regenerator on the regenerator performance. Electrical power consumption of the regenerator is assessed, and it is shown that the optoelectronic regenerator consumes a similar amount of electrical power as that consumed by an all-optical version of the regenerator using semiconductor optical amplifiers as a nonlinear element.

The two-, three-, and four-channel mapping multiplexing technique (MMT) is demonstrated to increase the data capacity of multilevel intensity-modulated transmission formats to 2, 3, and 4 bits/symbol with a substantial reduction in power penalty. This paper outlines the $N$ -channel MMT design metric consideration influence on the performance enhancement of higher order amplitude modulated systems in terms of power penalty, receiver sensitivity, and spectral efficiency. The signal space model has been developed for $N$ -channel MMT, where the average electrical and optical power expressions are derived. Transmission of 2, 3, and 4 bits/symbol using MMT system shows better performance in terms of the average optical power penalty, in comparison with pulse amplitude modulation (M-PAM) formats, with respect to the information capacity. The proposed scheme can be considered as an alternative to M-PAM systems with enhanced power efficiency.

We present a silicon photonic traveling-wave Mach–Zehnder modulator operating near 1550 nm with a 3-dB bandwidth of 35 GHz. A detailed analysis of traveling-wave electrode impedance, microwave loss, and phase velocity is presented. Small- and large-signal characterization of the device validates the design methodology. We further investigate the performance of the device in a short-reach transmission system. We report a successful 112-Gb/s transmission of four-level pulse amplitude modulation over 5 km of SMF using 2.2 ${\rm V}_{{\rm p} - {\rm p}} $ drive voltage. Digital signal processing is applied at the transmitter and receiver. 56-GBaud PAM-4 and 64-Gb/s PAM-2 transmission is demonstrated below a pre-FEC hard decision threshold of $4.4 \times 10^{-3}$ .

We embody a miniature reflection-type optical displacement sensor tapping into a projected beam that features high structural tolerance. A code scale with periodic patterns spatially encrypts the projected beam, which is established by imaging a collimated beam from a vertical-cavity surface-emitting laser via an aspheric lens, and linearly expands it, so as to be decoded by a receiver that comprises four serially cascaded identical photodetector cells. For the modulated beam, we observe a pitch increase with a rate of 18 μm/mm along the propagation direction. The two quadrature signals Sig-A and Sig-B derived from the PD signals exhibit a 900 phase relationship. The proposed sensor has been designed via ray-optic simulations and embodied through passive alignment, combined with plastic injection mold. We achieve a positional resolution of 10 μm from either of Sig-A and Sig-B. By concurrently considering the two quadrature outputs, we efficiently enhance the resolution to 2.5 μm, with the discovered direction of displacement. Finally, we thoroughly investigate the crucial dependence of the sensor performance on the positional tolerance pertaining to the constituent elements, which is discovered to be as large as +/-100 μm, under a certain resolution.

The atmospheric influence on wave propagation was investigated during the First European South African Transmission ExpeRiment from June 2015 to February 2016. The focus in this article was set on optical turbulence, the main atmospheric factor affecting the position and strength of Laser beams, the performance of electro-optical systems and imaging. Measurements were performed continuously during the campaign on three sites over the northwestern part of False Bay. The optical turbulence measurements include in situ measurements using an ultrasonic anemometer at the Roman Rock Island. Integrated optical turbulence measurements were performed at two sites, over a path of 1.8 km and a long distance path of 8.6 km. The sites may be affected by local effects of the coastal environment. For comparison, the optical turbulence was modeled using micrometeorological parameterization. Additionally, the optical turbulence was determined by simulations using the weather research and forecast model WRF. Simulation results were compared to measurements considering seasonal and meteorological variations. The representativeness of the measurements locations for offshore measurements will be discussed. © 2018 SPIE.

Here in this work, we study the electro-refractive modulation of CVD grown single layer graphene placed on top of a silicon microring resonator biased using a polymer electrolyte gate. A voltage length product for a phase shift of π, VπL = 2.7 Vmm has been extracted, which is better compared to silicon depletion horizontal and interleaved pn junction type phase modulators and competitive with Silicon-Insulator-Silicon Capacitor modulators.

Fiber-optic research in signal processing for the first generation of coherent communication systems was dominated by receivers with blind adaptation. Next-generation systems will require a scalable and modular design for higher order modulation formats. Due to the nature of the fiber channel and the required parallelization in high-speed receivers, data-aided and blind algorithms call for a general reassessment when used in coherent optic receivers employing higher order modulation formats. In this paper, blind and data-aided receivers are compared for coherent single-carrier optical systems in terms of complexity, tracking ability, and convergence speed. Methods for equalization are discussed for time-domain- and frequency-domain-based receivers covering the most important algorithms. The general superiority of data-aided frequency-domain equalization is demonstrated.

©Cranfield University, This thesis reports a summary of the PhD programme for the assessment of person‘s emotional anxiety using Electro-optical technology. The thesis focuses mainly on the understanding of fundamental properties of physiological responses to emotional anxiety and how they can be captured by using Electro-optical (EO) imaging methods such as hyperspectral imaging (HSI) and thermal imaging (TI) techniques. The thesis summarises three main areas of work that have been undertaken by the author in the programme: (a) Experimental set up including HSI system and data acquisition software design and implementation, (b) fundamental understanding of physiological responses to emotional anxiety from the EO perspective and (c) the development of a novel remote sensing technique for the assessment of emotions without the requirement of base line information. One of our main results is to provide evidence to prove that the mean temperature in the periorbital region remains the same within 0.2°C during emotional anxiety. Furthermore, we have shown that it is the high temperature pixels within the periorbital, which increases in numbers by a huge amount after 2 minutes of the onset of anxiety. We have also developed techniques to allow the assessment anxiety without the need of base line information. The method has been tested using a sample size of about 40 subjects, and achieved promising result. Technologies for the remote sensing of heart beat rate has been in great demand, this study also involves the development of heart beat detection using TI system. Moreover, we have also attempted for the first time to sense glucose concentration from the blood sample in-vivo using HSI technique remotely.

In harbour environments operators should perform tasks as detection and classification. Present-day threats of smallobjects, as jet skis etc, should be detected, classified and recognized. Furthermore threat intention should be analysed. As harbour environments contain several hiding spaces, due to fixed and floating neutral objects, correct assessment of the threats is complicated when detection tracks are intermittently known. For this purpose we have analysed the capability of our image enhancement and detection technology to assess the performance of the algorithms in a harbour environment. Data were recorded in a warm harbour location. During these trials several small surfaces targets were used, that were equipped with ground truth equipment. In these environments short-range detection is mandatory, followed by immediate classification. Results of image enhancement and detection are shown. An analysis was made into the performance assessment of the detection algorithms

In harbour environments operators should perform tasks as detection and classification. Present-day threats of smallobjects, as jet skis etc, should be detected, classified and recognized. Furthermore threat intention should be analysed. As harbour environments contain several hiding spaces, due to fixed and floating neutral objects, correct assessment of the threats is complicated when detection tracks are intermittently known. For this purpose we have analysed the capability of our image enhancement and detection technology to assess the performance of the algorithms in a harbour environment. Data were recorded in a warm harbour location. During these trials several small surfaces targets were used, that were equipped with ground truth equipment. In these environments short-range detection is mandatory, followed by immediate classification. Results of image enhancement and detection are shown. An analysis was made into the performance assessment of the detection algorithms

For the first time, we propose and experimentally demonstrate millimeter-wave (mm-wave) generation in the E-band (71-76 GHz and 81-86 GHz) based on photonics generation technique. We also experimentally demonstrate a bidirectional full-duplex optical/wireless integration system in the E-band with 1.5-m wireless delivery, in which 2- and 2.5-Gb/s on_off keying (OOK) signals are independently carried by 74- and 84-GHz mm-wave carriers and can be implemented error-free transmission in two opposite directions at the same time. Furthermore, there is no obvious difference whether distributed feedback (DFB) laser (with linewidth less than 5 MHz) or external cavity laser (ECL) (with linewidth less than 100 kHz) is used.