Many researchers and engineers designing laser drivers for data rates at or above 10 gigabits per second (Gbps) implemented their designs using integrated circuit technologies that provide high bandwidth and good quality passive components such as GaAs, silicon bipolar, and InP. However, in low-cost and high volume short-haul applications at data rates of around 10 Gbps (such as LAN, MAN, and board-to-board interconnection), there has been an increasing interest in commercial CMOS technology for implementing the laser driver. This is because CMOS technology has unique advantages such as low power and low cost of fabrication that are the result of high yield and a high degree of integration. Therefore, the objective of this research in this dissertation is to investigate the possibility of implementing a high-speed CMOS laser driver for these cost sensitive applications. The high-speed CMOS laser drivers designed in this research are of two types. The first type is a low power laser driver for driving a vertical cavity surface emitting laser (VCSEL). The other driver type is a high current laser driver for driving edge-emitting lasers such as double-heterojunction (DH), multiquantum well (MQW), or Febry-Perrot (FP) lasers. The parasitic effects of the layout geometry are crucial in the design of the high-speed laser drivers. Thus, in this research, all simulations contain a complete set of parasitic elements extracted from the layout of the laser driver. To test laser drivers, chip-on-board (COB) technology is employed, and printed circuit boards (PCBs) to test the laser drivers are designed at the same time as the laser drivers themselves and manufactured specifically for these tests. This research makes two significant new contributions to the technology that are reported and described here. One is the first 10 Gbps performance of a differential CMOS laser driver with better than 10-14 bit-error-rate (BER). The second is the first demonstration of a heterogeneous integration method to integrate independently grown and customized thin film lasers onto CMOS laser driver circuits to form an optical transmitter.

This thesis presents the design and analysis of two high speed analog laser driver stages (LDS) for use in a passive optical network (PON) upstream burst-mode transmitter (BM-Tx) using low cost complementary metal oxide semiconductors (CMOS) technology. The maturation of CMOS technology has lead to aggressive scaling of device sizes which has made it an increasingly attractive technology for high speed analog design. CMOS provides high levels of integration as it is the industry standard for digital circuits, analog and digital systems can share one substrate reducing costs. Additionally CMOS is a more cost effective solution than traditional expensive high speed analog substrates. A 2.5 Gbps LDS fabricated in 0.18 um CMOS technology is presented. The LDS uses a two stage per-amplifier. Stage one consists of a cascode differential pair with a source follower voltage buffer, while stage two consists of a shunt inductively peaked differential pair using active inductors. A differential pair composed of large transistors is used in an open drain configuration for the output stage. Measurements of S-parameters are presented which accurately agree with simulations. Electrical eye diagram measurements are presented which demonstrate the LDS is able to provide a modulation current of 14.6-58 mA. 10%-90% approximate rise/fall times of 230/260 ps was obtained for a modulation current of 58 mA. Power consumption of the core was determined to be 68.5 mW, while the chip consumed an area of 0.8 mm x 0.7 mm including pads. A 10 Gbps LDS fabricated in 0.18 um CMOS technology is also presented. The LDS uses a cascode differential pair for the output stage. The per-amplifier for this design consists of a differential pair and utilizes spiral inductors for series inductive peaking between the per-amplifier and output stage. Measurements of S-parameters are presented which accurately agree with simulations. Electrical eye diagram measurements are presented which demonstrate the LDS is able to provide a modulation current of 22.6-62 mA. 10%-90% rise/fall time of 87 ps and 75 ps are respectively obtained while operating at maximum modulation current. The core of the LDS consumes a power of 287 mW, while the chip consumed an area of 0.79 mm x 0.7mm. The measured electrical eye diagrams for the 2.5 Gbps and the 10 Gbps meet the timing requirements for the GPON standard. Further work is needed to investigate whether or not the timing requirements would still be met once the CMOS chips are integrated with commercial laser diodes. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-09-24 10:43:33.418

This thesis deals with the design and subsequent realization of laser diode control devices. The circuit will be able to control the diode with using a laser driver, via a computer network or via the display for control current values, setting of initial values and more. The device will be connected also with a SD card for saving of settings. In the theoretical part there are described individual components that are needed for functionality of the device. The practical part contains a block diagram, in which is described complete feature of the device, then a draft scheme with a description of all integrated circuits and important components. At the end of this work is described the software that controls the entire designed device.

The main aim of this thesis is the design of an optical wireless link that is transmitted in free space, in the atmosphere. The thesis describes the composition of heads of the atmospheric optical link. One part of this work focuses on the issue of the spread of optical beam in the atmosphere. The facts which have a major impact on the transmission of optical radiation in free space are pointed out here as well. In this work phenomena of absorption, refraction of light, turbulence and dispersion are discussed. Wavelengths spread in the atmosphere with different decline and therefore this thesis provides an analysis of the use of wavelengths between 750 and 1600 nm depending on the meteorological visibility. It describes the basis of the design of AOS through stationary model using power balance equation. It depicts the description of the statistical model, which makes possible to determine the availability on the basis of probability. Current possibilities of AOS are in general described in this work. The practical part of the work is focused on the design of simulation model of transmitter and receiver AOS in the program Pspice. The receiver and transmitter are designed to replace transiver in the media converter. The receiver plays a key role, and therefore big part of the thesis is given to it. Receiver model is composed of a photodiode and of an transimpedance amplifier. The receiver circuit has been tested. The model of transmitter shows the principle of modulating of current, which flows in laser diode. This work does not carried the model of atmosphere, which would serve as a link between the receiver and the transmitter. The circuit of the receiver is subjected to the noise analysis. Parameter NEP and SNR is designed. Link budget is calculated for models of the receivers and the transmitters. The maximum distance of heads is set based on the requirements for a BER error rate which combine this condition. The design of the practical implementation results from the models of transmitters and receivers. Printed circuit boards are designed in EAGLE. Within the frame of this thesis no curcuit diagram is carried out.

This paper discusses the challenges and the trade-offs in the design of laser drivers for very-short distance optical communications. A prototype integrated circuit is designed and fabricated in 28 nm super-low-power CMOS technology. The power consumption of the transmitter is 17.2 mW excluding the VCSEL that in our test has a DC power consumption of 10 mW. The active area of the driver is only 0.0045 mm². The driver can achieve an error-free (<BER < 10^12) electrical data-rate of 25 Gbit/s using a pseudo random bit sequence of 2^7-1. When the driver is connected to the VCSEL module an open optical eye is reported at 15 Gbit/s. In the tested bias point the VCSEL module has a measured bandwidth of 10.7 GHz.

Cavity ring-down spectroscopy has been used over the last twenty years as a highly sensitive absorption spectroscopic technique to measure light attenuation in gases, liquids, and solid samples. An optical cavity is used as a multi-pass cell, and the decay time of the light intensity in the cavity is measured, thereby rendering the techniques insensitive to light intensity fluctuations. Optical waveguides are used to build the optical cavities presented in this work. The geometries of such waveguides permit the use of very small liquid sample volumes while retaining the advantages of cavity ring-down spectroscopy. In this thesis cavity ring-down measurements are conducted, both, in the time domain and by measuring phase-shifts of sinusoidally modulated light, and the two methods are theoretically connected using a simple mathematical model, which is then experimentally confirmed. A new laser driver, that is compatible with high powered diode lasers, has to be designed to be able to switch from time domain to frequency domain measurements. A sample path length enhancement within the optical cavity is explored with the use of liquid core waveguides. The setup was optimised with respect to the matrix liquid, the geometrical matching of waveguide geometries, and the shape of liquid core waveguide ends. Additionally, a new technique of producing concave lenses at fibre ends has been developed and the output of a general fibre lens is simulated. Finally, liquid core waveguides are incorporated into a fibre-loop ring-down spectroscopy setup to measure the attenuation of two model dyes in a sample volume of <1 µL. The setup is characterized by measuring concentrations of Allura Red AC and Congo Red from 1 µM to a limit of detection of 5 nM. The performance of the setup is compared to other absorption techniques measuring liquid samples. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-04-23 14:08:16.33