5G is emerging, but the current fronthaul transmission technologies used for 3G and 4G may not be efficient and appropriate for 5G. It has been found that frequency division multiple access (FDMA) and time-division multiple access (TDMA) based radio over fiber (RoF) may be considered the most appropriate for 5G fronthaul transmission technology. Due to analog RoF transmission, broadband linearization is required. In this work, both electrical and optical broadband linearization techniques are reviewed.
There is an emerging market today for indoor positioning systems capable of working alongside global navigation satellite systems, such as the global positioning system, in indoor environments. Many systems have been proposed in the literature but all of them have fundamental flaws that hold them back from widescale implementation. We review angle-of-arrival (AOA) and angle-difference-of-arrival (ADOA) optical indoor positioning systems which have been proven to be robust, accurate, and easily implementable. We build an AOA/ADOA optical indoor positioning system out of a simple commercial high-speed camera and white light light emitting diodes (LEDs) which operate over a working area of 1 m3, and compare its performance to other indoor positioning methods. The AOA and ADOA systems achieve positioning with low errors of 1.2 and 3.7 cm, respectively.
A brief overview of recent experimental research on coherent optical fiber transmission systems at Queen’s University is presented. Exemplary results are described that exploit real-time signal processing to assess the impact of cascaded optical filtering.
Entangled optical quantum states are essential towards solving questions in fundamental physics and are at the heart of applications in quantum information science. For advancing the research and development of quantum technologies, practical access to the generation and manipulation of photon states carrying significant quantum resources is required. Recently, integrated photonics has become a leading platform for the compact and cost-efficient generation and processing of optical quantum states. Despite significant advances, most on-chip non-classical light sources are still limited to basic bi-photon systems formed by two-dimensional states (i.e., qubits). An interesting approach bearing large potential is the use of the time or frequency domain to enabled the scalable on-chip generation of complex states. In this manuscript, we review recent efforts in using on-chip optical frequency combs for quantum state generation and telecommunications components for their coherent control. In particular, the generation of bi- and multi-photon entangled qubit states has been demonstrated, based on a discrete time domain approach. Moreover, the on-chip generation of high-dimensional entangled states (quDits) has recently been realized, wherein the photons are created in a coherent superposition of multiple pure frequency modes. The time- and frequency-domain states formed with on-chip frequency comb sources were coherently manipulated via off-the-shelf telecommunications components. Our results suggest that microcavity-based entangled photon states and their coherent control using accessible telecommunication infrastructures can open up new venues for scalable quantum information science.
In classical optics, interference occurs between two optical fields when they are indistinguishable from one another. The same holds true in quantum optics, where a particular experiment, the Franson interferometer, involves the interference of a photon pair with a time-delayed version of itself. The canonical version of this interferometer requires that the time delay be much shorter than the coherence length of the pump used to generate the photon pair, so as to guarantee indistinguishability. However, when this time delay is comparable to the coherence length, conventional wisdom suggests that interference visibility degrades significantly. In this work, though, we show that the interference visibility can be restored through judicious temporal post-selection. Utilizing correlated photon pairs generated by a pump whose pulsewidth (460 ps) is shorter than the interferometer’s time delay (500 ps), we are able to observe a fringe visibility of 97.4±4.3%. We believe this new method can be used for the encoding of high-dimensional quantum information in the temporal domain.
Much attention has been focused on the use of scalar modes for space division multiplexing (SDM). Alternative vector mode bases offer another solution set for SDM, expanding the available trade-offs in system performance and complexity. We present two types of ring core fiber conceived and designed to explore SDM with fibers exhibiting low interactions between supported modes. We review demonstrations of fiber data transmission for two separate vector mode bases: one for orbital angular momentum (OAM) modes and one for linearly polarized vector (LPV) modes. The OAM mode demonstrations include short transmissions using commercially available transceivers, as well as kilometer length transmission at extended data rates. The LPV demonstrations span kilometer length transmissions at high data rate with coherent detection, as well as a radio over fiber experiment with direct detection of narrowband signals.
This paper reviews the work done by researchers at INRS and UBC in the field of integrated microwave photonics (IMWPs) using silicon based waveguide Bragg gratings (WBGs). The grating design methodology is discussed in detail, including practical device fabrication considerations. On-chip implementations of various fundamental photonic signal processing units, including Fourier transformers, Hilbert transformers, ultrafast pulse shapers etc., are reviewed. Recent progress on WBGs-based IMWP subsystems, such as true time delay elements, phase shifters, real time frequency identification systems, is also discussed.
In recent years, our research group has developed and studied new rare-earth doped materials for the promising technology of solid-state laser cooling, which is based on anti-stokes fluorescence. To the best of our knowledge, our group is the only one in Canada leading the research into the properties of nanoparticles, glasses and glass-ceramics for optical refrigeration applications. In the present work, optical properties of 50GeO2-30PbF2-18PbO-2YbF3 glass-ceramics for laser cooling are presented and discussed as a function of crystallization temperature. Spectroscopic results show that samples have near infrared photoluminescence emission due to the 2F5/2 – 2F7/2 Yb3+ transition, centered at ~1016 nm with an excitation wavelength of 920 nm or 1011 nm, and the highest photoluminescence emission efficiency occurs for heat-treatment for 5 h at 350°C. The internal photoluminescence quantum yield varies between 99% and 80%, depending on the temperature of heat-treatment, being the most efficient under 1011 nm excitation. The 2F5/2 lifetime increases from 1.472 to 1.970 ms for heat treatments at 330°C to 350°C, respectively, due to energy trapping and the low phonon energy of the nanocrystals. The sample temperature dependence was measured with a fiber Bragg grating sensor, as a function of input pump laser wavelength and processing temperature. These measurements show that the heating process approaches near zero for an excitation wavelength between 1020 and 1030 nm, which is an indication that phonons are removed effectivelly from the glass-ceramic materials, and they can be used for optical laser cooling applications. On the other hand, the temperature increase as a function of input laser power into samples remains constant between 920 and 980 nm wavelength excitation, a temperature variation of 36 K/W (temperature of 58°C/W) was attained under excitation at 950 nm, showing a possible use for biomedical applications to be explored.