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Papers by Richard L. Lachance

Research paper thumbnail of Super-Gaussian output from a CO_2 laser by using a graded-phase mirror resonator

Research paper thumbnail of High-Density Gas Column Abundance Measurements Using New Low-Cost Autonomous Sensors, A Solution For Gas Flux Monitoring

AGU Fall Meeting Abstracts, Dec 1, 2016

Research paper thumbnail of Turbulence reduction algorithm in hyperspectral images using four-port imaging spectroradiometer

Research paper thumbnail of Tunable chromatic dispersion compensator

IEEE Convention of Electrical and Electronics Engineers in Israel, Nov 30, 2004

One of the major bottlenecks in optical telecommunication systems is chromatic dispersion. Each f... more One of the major bottlenecks in optical telecommunication systems is chromatic dispersion. Each frequency component of an optical pulse travels at a different group velocity, hence the pulse width broadens, thereby leading to system penalties. A demand for tunable compensators has arisen from DWDM systems with dynamic routing where the degree of pulse broadening is unknown. Another demand comes from the increased sensitivity of 40 Gb/s systems. We have suggested a novel design based on periodically poled lithium niobate (PPLN) which can compensate the dispersion of three 40 GHz channels with 200 GHz spacing in the range of 200-1000 ps/nm. Tunability is achieved by changing the ratio between the length of the sections, where the refractive index is modulated, and the length of the phase shifters. To the best of our knowledge, this is the first publication suggesting this approach.

Research paper thumbnail of Optical structure for the compensation of chromatic dispersion and dispersion slope in a light signal

Research paper thumbnail of Power efficient assemblies for applying a temperature gradient to a refractive index grating

Research paper thumbnail of Fine-tuning assembly for optical gratings

Research paper thumbnail of Tunable optical structure for the compensation of chromatic dispersion in a light signal

Research paper thumbnail of Methods for the alignment and calibration of the spectral responses of optical filters

Research paper thumbnail of Étude D'Un Résonateur Laser Adapté Supergaussien À Miroir À Gradient De Phase /

Research paper thumbnail of Étude D'Une Fibre Optique À Profil D'Indice Parabolique Divergent /

Thèse (M. Sc.) - Université Laval, 1990. Bibliogr. : f. 102-106.

Research paper thumbnail of Study of a Custom Supergaussian Laser Resonator Using a Graded-Phase Mirror

In this thesis are presented the design, the fabrication, and the analysis of a new type of laser... more In this thesis are presented the design, the fabrication, and the analysis of a new type of laser resonator called custom resonator, characterized by the presence of an aspherical mirror shaped to force oscillation in a particular output mode specified by the designer. Two of these resonators, included in a pulsed CO_2-TEA laser of semiconfocal geometry, are designed to generate supergaussian beams of order 4 and 6 in the fundamental mode. The graded -phase mirrors (GPM) were made by using the diamond cutting technique on a copper substrate. This particular geometry generates a large fundamental mode, which is well suited for extracting a maximum of monomode energy from the gain medium. This configuration also enables higher discrimination, which improves general characteristics and performance of the laser. A numerical model, based on an incoherent superposition of modes in a saturated gain medium, gives an adequate simulation of the observed experimental behavior.

Research paper thumbnail of <title>Fiber Bragg gratings and chromatic dispersion</title>

Applications of Photonic Technology 5, 2003

Since the late 1990s, steady advances in wavelength division multiplexing (WDM) technology have p... more Since the late 1990s, steady advances in wavelength division multiplexing (WDM) technology have provided better ways to increase the capacity of optical networks. As the industry makes the transition to advanced optical networks, three significant trends become evident in long-haul transmission system, namely the continual increase in the number of dense WDM channels, the increase in data rates from 2.5 Gb/s to today's 10 Gb/s, to tomorrow's 40 Gb/s, and finally longer distances between electrical regeneration sites. These trends towards an increased optical network capacity are now clashing with chromatic dispersion. The management of chromatic dispersion due to the optical fiber and optical components is one of the critical challenges for present and future telecommunication systems operating at data rates of 10 Gb/s and higher. Chromatic dispersion, while inherently troublesome, does however bring with it some advantages, in that it keeps undesirable non-linear effects (such as self-phase modulation and four-wave mixing) to acceptable levels. Hence, rather than eliminating completely chromatic dispersion with specialized fiber like dispersion-shifted fiber, it is better to compensate for it using additional devices. This paper will discuss the application of high-end FBGs to telecommunication systems, focusing on their performances with respect to chromatic dispersion. Two types of components will be discussed: low-dispersion FBG WDM filters and FBG dispersion compensators. High-quality ultra-low dispersion FBGs have been fabricated successfully and their key attributes will be discussed. Advanced applications of FBGs for chromatic dispersion compensation, such as broadband multi-channel dispersion and slope compensation, will be covered. In particular, FBG dispersion slope compensators can be used in conjunction with Dispersion Compensating Fiber (DCF) to fully manage the dispersion over a large number of WDM channels. The need for tunable dispersion compensation at 40 Gb/s transmission rates will be discussed. Experimental results will also be presented.

Research paper thumbnail of Adjustable athermal package for optical fiber devices

Research paper thumbnail of Grating Based Soluti Ons for Chromatic Dispersion Management in DWDM Systems

Abstract: In this paper, we present an innovative multi-channel solution to dispersion management... more Abstract: In this paper, we present an innovative multi-channel solution to dispersion management based on complex fiber Bragg grating (FBG) technology. The grating-based slope compensator takes into account dispersion variation by optimizing the dispersion ...

Research paper thumbnail of Recent progress on FBG-based tunable dispersion compensators for 40 Gb/s applications

OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007

Abstract The optical performance of state-of-the-art FBG-based tunable dispersion compensators is... more Abstract The optical performance of state-of-the-art FBG-based tunable dispersion compensators is given in view of the recent advances. Results are given for a 33-channel device with 80 GHz-bandwidth and for a 51-channel device with 40 GHz-bandwidth.

Research paper thumbnail of 50 and 100 GHz multichannel tunable chromatic dispersion slope compensator

Journal of Lightwave Technology, 2003

A novel grating-based multichannel tunable dispersion compensator is reported. The dispersion is ... more A novel grating-based multichannel tunable dispersion compensator is reported. The dispersion is settable on a per-channel basis to match a given dispersion slope. Both the absolute dispersion and the dispersion slope can be tuned thermally.

Research paper thumbnail of Group delay ripple in fibre Bragg grating tunable dispersion compensators

Electronics Letters, 2002

A low-loss higher-ordcr-mode dispcnian compensator that enables practical implemenlation of lumpe... more A low-loss higher-ordcr-mode dispcnian compensator that enables practical implemenlation of lumped UT multi-span dispersion compensation schemes is demonstiuted. The C~nneCtOT-tO-COnnCCtoT module loss is 3.16 dB, and yiclds-886 psinm of dispersion, corresponding to compensation of 200 h of NZDSF.

Research paper thumbnail of WILL YOUR 25 GHZ FILTERS STAND THE HEAT? Environmental challenges facing high spectral density networks

Research paper thumbnail of Limb Sensing, on the Path to Better Weather Forecasting

Research paper thumbnail of Super-Gaussian output from a CO_2 laser by using a graded-phase mirror resonator

Research paper thumbnail of High-Density Gas Column Abundance Measurements Using New Low-Cost Autonomous Sensors, A Solution For Gas Flux Monitoring

AGU Fall Meeting Abstracts, Dec 1, 2016

Research paper thumbnail of Turbulence reduction algorithm in hyperspectral images using four-port imaging spectroradiometer

Research paper thumbnail of Tunable chromatic dispersion compensator

IEEE Convention of Electrical and Electronics Engineers in Israel, Nov 30, 2004

One of the major bottlenecks in optical telecommunication systems is chromatic dispersion. Each f... more One of the major bottlenecks in optical telecommunication systems is chromatic dispersion. Each frequency component of an optical pulse travels at a different group velocity, hence the pulse width broadens, thereby leading to system penalties. A demand for tunable compensators has arisen from DWDM systems with dynamic routing where the degree of pulse broadening is unknown. Another demand comes from the increased sensitivity of 40 Gb/s systems. We have suggested a novel design based on periodically poled lithium niobate (PPLN) which can compensate the dispersion of three 40 GHz channels with 200 GHz spacing in the range of 200-1000 ps/nm. Tunability is achieved by changing the ratio between the length of the sections, where the refractive index is modulated, and the length of the phase shifters. To the best of our knowledge, this is the first publication suggesting this approach.

Research paper thumbnail of Optical structure for the compensation of chromatic dispersion and dispersion slope in a light signal

Research paper thumbnail of Power efficient assemblies for applying a temperature gradient to a refractive index grating

Research paper thumbnail of Fine-tuning assembly for optical gratings

Research paper thumbnail of Tunable optical structure for the compensation of chromatic dispersion in a light signal

Research paper thumbnail of Methods for the alignment and calibration of the spectral responses of optical filters

Research paper thumbnail of Étude D'Un Résonateur Laser Adapté Supergaussien À Miroir À Gradient De Phase /

Research paper thumbnail of Étude D'Une Fibre Optique À Profil D'Indice Parabolique Divergent /

Thèse (M. Sc.) - Université Laval, 1990. Bibliogr. : f. 102-106.

Research paper thumbnail of Study of a Custom Supergaussian Laser Resonator Using a Graded-Phase Mirror

In this thesis are presented the design, the fabrication, and the analysis of a new type of laser... more In this thesis are presented the design, the fabrication, and the analysis of a new type of laser resonator called custom resonator, characterized by the presence of an aspherical mirror shaped to force oscillation in a particular output mode specified by the designer. Two of these resonators, included in a pulsed CO_2-TEA laser of semiconfocal geometry, are designed to generate supergaussian beams of order 4 and 6 in the fundamental mode. The graded -phase mirrors (GPM) were made by using the diamond cutting technique on a copper substrate. This particular geometry generates a large fundamental mode, which is well suited for extracting a maximum of monomode energy from the gain medium. This configuration also enables higher discrimination, which improves general characteristics and performance of the laser. A numerical model, based on an incoherent superposition of modes in a saturated gain medium, gives an adequate simulation of the observed experimental behavior.

Research paper thumbnail of <title>Fiber Bragg gratings and chromatic dispersion</title>

Applications of Photonic Technology 5, 2003

Since the late 1990s, steady advances in wavelength division multiplexing (WDM) technology have p... more Since the late 1990s, steady advances in wavelength division multiplexing (WDM) technology have provided better ways to increase the capacity of optical networks. As the industry makes the transition to advanced optical networks, three significant trends become evident in long-haul transmission system, namely the continual increase in the number of dense WDM channels, the increase in data rates from 2.5 Gb/s to today's 10 Gb/s, to tomorrow's 40 Gb/s, and finally longer distances between electrical regeneration sites. These trends towards an increased optical network capacity are now clashing with chromatic dispersion. The management of chromatic dispersion due to the optical fiber and optical components is one of the critical challenges for present and future telecommunication systems operating at data rates of 10 Gb/s and higher. Chromatic dispersion, while inherently troublesome, does however bring with it some advantages, in that it keeps undesirable non-linear effects (such as self-phase modulation and four-wave mixing) to acceptable levels. Hence, rather than eliminating completely chromatic dispersion with specialized fiber like dispersion-shifted fiber, it is better to compensate for it using additional devices. This paper will discuss the application of high-end FBGs to telecommunication systems, focusing on their performances with respect to chromatic dispersion. Two types of components will be discussed: low-dispersion FBG WDM filters and FBG dispersion compensators. High-quality ultra-low dispersion FBGs have been fabricated successfully and their key attributes will be discussed. Advanced applications of FBGs for chromatic dispersion compensation, such as broadband multi-channel dispersion and slope compensation, will be covered. In particular, FBG dispersion slope compensators can be used in conjunction with Dispersion Compensating Fiber (DCF) to fully manage the dispersion over a large number of WDM channels. The need for tunable dispersion compensation at 40 Gb/s transmission rates will be discussed. Experimental results will also be presented.

Research paper thumbnail of Adjustable athermal package for optical fiber devices

Research paper thumbnail of Grating Based Soluti Ons for Chromatic Dispersion Management in DWDM Systems

Abstract: In this paper, we present an innovative multi-channel solution to dispersion management... more Abstract: In this paper, we present an innovative multi-channel solution to dispersion management based on complex fiber Bragg grating (FBG) technology. The grating-based slope compensator takes into account dispersion variation by optimizing the dispersion ...

Research paper thumbnail of Recent progress on FBG-based tunable dispersion compensators for 40 Gb/s applications

OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007

Abstract The optical performance of state-of-the-art FBG-based tunable dispersion compensators is... more Abstract The optical performance of state-of-the-art FBG-based tunable dispersion compensators is given in view of the recent advances. Results are given for a 33-channel device with 80 GHz-bandwidth and for a 51-channel device with 40 GHz-bandwidth.

Research paper thumbnail of 50 and 100 GHz multichannel tunable chromatic dispersion slope compensator

Journal of Lightwave Technology, 2003

A novel grating-based multichannel tunable dispersion compensator is reported. The dispersion is ... more A novel grating-based multichannel tunable dispersion compensator is reported. The dispersion is settable on a per-channel basis to match a given dispersion slope. Both the absolute dispersion and the dispersion slope can be tuned thermally.

Research paper thumbnail of Group delay ripple in fibre Bragg grating tunable dispersion compensators

Electronics Letters, 2002

A low-loss higher-ordcr-mode dispcnian compensator that enables practical implemenlation of lumpe... more A low-loss higher-ordcr-mode dispcnian compensator that enables practical implemenlation of lumped UT multi-span dispersion compensation schemes is demonstiuted. The C~nneCtOT-tO-COnnCCtoT module loss is 3.16 dB, and yiclds-886 psinm of dispersion, corresponding to compensation of 200 h of NZDSF.

Research paper thumbnail of WILL YOUR 25 GHZ FILTERS STAND THE HEAT? Environmental challenges facing high spectral density networks

Research paper thumbnail of Limb Sensing, on the Path to Better Weather Forecasting