Use Of Avalanche Photodiodes Research Articles

Optical fiber deformation and vibration monitoring at distinct data rates with distinct photo-detectors devices

The transmission of the high data rate and information over the optical fiber is restricted by various dispersion phenomenon which further results into intersymbol interference (ISI). This article proposes two different methodologies for optical fiber deformation aiding vibration monitoring one using the pin diode as a photo-detector device and another manifesting the avalanche photo-detector. The novelty of this article lies in optical signal conversion using photo-detector processing followed by low pass Gaussian filter in order to reduce the extra contortion. This work is approaching electronic dispersion compensation technique (EDC) for compensation of chromatic dispersion at two distinct bit rates of 25 and 30 Gbps over 120 km of single mode fiber. Both the diodes have tested for theory performance using factors like Q-factor, bit error rate and eye height. It is found that pin diode is exhibiting a quality factor of 67.150 and 40.5944 at 25 and 30 Gbps, respectively. When avalanche pin diode is used at the same data rates, quality factor of 73.0240 and 43.3523 are obtained, respectively. Hence, use of avalanche photodiode at high bit rates is utilized and the simulations showed the optimum photo-diode for efficacious dispersion compensation at such a long transmission distance.

Simulation and experimental investigation of cross-phase modulation effect on 5G fronthaul wavelengths

Dense wavelength-division multiplexing is conceived as an appropriate solution for the 5G fronthaul system to cope with the rapidly increasing demand for bandwidth. While the cross-phase modulation (XPM) would appear when the signals are transmitted simultaneously in the single-mode fiber. The XPM effect on the 5G fronthaul wavelengths is investigated through both simulation and experimental campaigns. Simulation results show that the electrical spectrum crosstalk will occur with the wavelengths transmitting synchronously, when the channel spacing is 100 GHz and the speed is 25 Gbit / s per channel in the 10-km link. Also, the intensity of the electrical spectrum crosstalk becomes stronger when the launch power increases from 10 until 14 dBm. While comparing with the results obtained from the positive-intrinsic-negative (PIN) detector, the XPM-induced sensitivity penalty can be alleviated by 0.3 dB in use of avalanche photodiode (APD), which can provide higher signal-to-noise ratio. Consistent with the simulation results, the electrical spectrum crosstalk also appears in the experimental campaign under the same conditions. Furthermore, a sensitivity improvement of 0.5 dB is obtained using 25-GHz APD receiver, compared with the adoption of 35-GHz PIN receiver case.

Coverage Extension of Indoor 5G Network Using RoF-Based Distributed Antenna System

We propose and demonstrate a cascaded distributed antenna system (DAS) for efficiently extending the coverage of the mmWave-based 5G indoor network. For this, we exploit the radio-over-fiber (RoF) system based on the intermediate-frequency-over-fiber (IFoF) transmission technique that is enabled to add/drop the specific wavelength to the designated remote antenna unit (RAU) with using optical splitters and coarse wavelength division multiplexing (CWDM) filters. Moreover, the IFoF transceivers (TRx) perform the subcarrier multiplexing (SCM) in order to transmit 2 × 8 frequency allocation (FA) 5G signals per a single optical carrier, where each FA has 100 MHz bandwidth, leading each RAU to support 2 × 2 MIMO operation. Consequently, the cascaded structure allows for the adaptive and flexible configuration of the order of MIMO in accordance of the required data throughput at the specific indoor area. We introduce the cascaded IFoF link structure that can support up-to 13.5 dB optical power budget with following errorvector-magnitude (EVM) performance characterizations. And then we experimentally demonstrate the RoFbased cascaded DAS network, showing that more than 1 Gb/s total throughput can be achieved per a single antenna. Furthermore, we examine the use of avalanche photodiode (APD) to further increase the optical power budget (i.e., the coverage) based on experiment as well as simulation.

Compact lidar system using laser diode, binary continuous wave power modulation, and an avalanche photodiode-based receiver controlled by a digital signal processor

We analyze the practical limits of a lidar system based on the use of a laser diode, random binary continuous wave power modulation, and an avalanche photodiode (APD)-based photereceiver, combined with the control and computing power of the digital signal processors (DSP) currently available. The target is to design a compact portable lidar system made all in semiconductor technology, with a low-power demand and an easy configuration of the system, allowing change in some of its features through software. Unlike many prior works, we emphasize the use of APDs instead of photomultiplier tubes to detect the return signal and the application of the system to measure not only hard targets, but also medium-range aerosols and clouds. We have developed an experimental prototype to evaluate the behavior of the system under different environmental conditions. Experimental results provided by the prototype are presented and discussed.

High-capacity mixed fiber-wireless backhaul networks using MMW radio-over-MCF and MIMO

In this paper, we have proposed a high-capacity backhaul network, which is based on mixed fiber-wireless systems using millimeter-wave radio-over-multi-core fiber (MMW RoMCF) and multiple-input multiple-output (MIMO) transmission, for next generation mobile access networks. In addition, we also investigate the use of avalanche photodiode (APD) to improve capacity of the proposed backhaul downlink. We then theoretically analyze the system capacity comprehensively while considering various physical impairments including noise, MCF crosstalk, and fading modeled by Rician MIMO channel. The feasibility of the proposed backhaul architecture is verified via the numerical simulation experiments. The research results demonstrate that our developed backhaul solution can significantly enhance the backhaul capacity; the system capacity of 24 bps/Hz can be achieved with 20-km 8-core MCF and 8 × 8 MIMO transmitted over 100-m Rician fading link. It is also shown that the system performance, in term of channel capacity, strongly depend on the MCF inter-core crosstalk, which is governed by the mode coupling coefficient, the core pitch, and the bending radius.

Systematic afterpulsing-estimation algorithms for gated avalanche photodiodes.

We present a method designed to efficiently extract optical signals from InGaAs avalanche photodiodes (APDs) operated in gated mode. In particular, our method permits an estimation of the fraction of counts that actually results from the signal being measured, as opposed to being produced by noise mechanisms, specifically by afterpulsing. Our method in principle allows the use of InGaAs APDs at high detection efficiencies, with the full operation bandwidth, either with or without resorting to the application of a dead-time. As we show below, our method can be used in configurations where afterpulsing exceeds the genuine signal by orders of magnitude, even near saturation. The algorithms that we have developed are suitable to be used either in real-time processing of raw detection probabilities or in post-processing applications, after a calibration step has been performed. The algorithms that we propose here can complement technologies designed for the reduction of afterpulsing.

Recent Advances in Avalanche Photodiodes

Until the early 2000's, the avalanche photodiode (APD) was widely deployed in high-performance optical receivers that operated up to 10 Gb/s. In subsequent years, the use of APDs for high-capacity systems declined as a result of their limited gain bandwidth, the transition to coherent detection, and the development of high-efficiency modulation techniques. Recently, the rapid growth of optical-fiber communications systems that utilize baud rates up to 25 Gb/s represented by a 100-Gb/s Ethernet has led to a resurgence of research on APDs and the development of low-noise APDs with enhanced gain bandwidth. This paper presents a brief review of APD fundamentals and describes some of the recent advances.

In‐orbit performance of avalanche photodiode as radiation detector on board the picosatellite Cute‐1.7+APD II

The Cute‐1.7+APD II, 10 × 15 × 20 cm3 in size and 5 kg in mass, is the third picosatellite developed by students at the Tokyo Institute of Technology. One of the primary goals of the Cute‐1.7+APD II mission is to validate the use of avalanche photodiodes (APDs) as a radiation detector for the first time in a space experiment. While the mission itself is immature compared to the forefront satellites of space plasma physics, use of APDs offers various possibilities regarding a brand‐new electron energy analyzer for medium‐energy electrons and ions (1–100 keV), as well as a high‐performance light sensor for the future X‐ray astronomy missions. The satellite was successfully launched by ISRO PSLV‐C9 rocket on 28 April 2008 and has since been in operation for more than a year. The Cute‐1.7+APD II carries two reverse‐type APDs to monitor the distribution of low‐energy particles (mainly electrons and protons) down to 9.2 keV trapped in a low Earth orbit (LEO), including the South Atlantic Anomaly (SAA) as well as aurora bands. We present the design parameters and various preflight tests of the APDs prior to launch, particularly, the high counting response and active gain control system for the Cute‐1.7+APD II mission. Examples of electron/proton distribution, obtained in continuous 12 h observations, will be presented to demonstrate the initial flight performance of the APDs in orbit.

Characterization of avalanche photodiodes (APDs) for the electromagnetic calorimeter in the ALICE experiment

The Electromagnetic Calorimeter (EMCal) of the ALICE experiment at LHC will extensively make use of avalanche photodiodes (APDs) for the readout of scintillation light. The large sensitive area, high quantum efficiency and low dark current make this type of photosensors well-suited for the EMCal requirements. A testing activity is currently in progress in order to characterize the main properties of these APDs and find the best working conditions. Fundamental tasks are the individual test of all APDs after presetting their nominal gain via the bias control and the study of APD gain coefficients as a function of the applied bias voltage and temperature. An overview of the adopted procedure will be presented, together with a description of preliminary results obtained on a first sample of APDs during the testing activity.

Thomson scattering diagnostics in the Globus-M tokamak

Specific features of the Thomson scattering diagnostics, its main characteristics and capabilities, and the results of its experimental testing in the Globus-M tokamak are described. A powerful multipulse neodymium-glass laser is designed for investigating both fast and slow processes in the tokamak plasma. The laser is capable of generating up to 20 pulses uniformly distributed in time during one tokamak discharge. In order to investigate fast transient processes, the laser repetition rate can be increased within a specified time interval. The possibility of varying the time interval between laser pulses from 0.5 ms to 1.0 s makes this diagnostics highly informative. The optical scheme developed in the course of these studies allowed one to simplify the power supply system and create a comparatively inexpensive laser system. The use of avalanche photodiodes and filtering polychromators with a high optical transparency provides high sensitivity of the diagnostics. A special software was designed that allows automatic processing of several hundred signals during one shot and provides data on the electron density and temperature immediately in the course of measurements. The diagnostics allows one to trace the time behavior of the spatial profiles of the electron temperature and density in both ohmic discharges and discharges with auxiliary heating, as well as in experiments with particle injection with a plasma gun.

The use of avalanche photodiodes for the detection of soft x rays

Avalanche photodiodes (APDs) offer an attractive alternative to the gas flow proportional counter (GFPC) for the counting of individual soft x-ray photons. They are reasonably efficient detectors and have the capability of handling higher count rates than a GFPC. With the advent of intense monochromatic x-ray beams from synchrotron radiation sources, the ability to handle high count rates is becoming more important than the need for any energy resolution. Another attraction of using solid-state detectors is the possibility of multielement fabrication of devices: configured detector arrays can then be considered for a number of applications. For example, in the scanning transmission x-ray microscope such a detector system allows much more sophisticated imaging techniques, such as differential phase contrast imaging with a quadrant APD array. In this paper we compare results for several commercially available APDs used as photon counters with a GFPC over the energy range 200–700 eV. APDs operated in the Geiger mode with a simple passive circuit to quench the avalanche current pulses can achieve count rates of the order of 106 s−1, and this can be greatly improved upon with the use of an active quenching circuit.

Avalanche photo-diodes for high frequency applications

The aim of this paper is to encourage the use of avalanche photo-diodes in optical communication systems, especially if high speeds are required. The basic theory of the device is first briefly reviewed. This is followed by a few examples of the possible performance compared to that of a PIN photodiode. Some frequency response measurements of recent avalanche photodiodes are then presented.