Rose-Hulman Institute of Technology has 35 years of graduating optical scientists and engineers. The change from the Applied Optics degree program to the Optical Engineering degree program occurred in 2003, which paved the way for ABET accreditation. The past and present program reinforces the idea that we are educating our students in optics applications to deal with real-world problems and practice the profession of optical engineers. The RHIT program has been at the forefront of developing project-based learning since its inception in 1983. Since the name changed, the optical engineering program (OE) has completed three cycles of ABET accreditation. We are continuously improving our OE curriculum to meet the current and future needs of the industry and cutting-edge research. To lead the ABET review, Rose-Hulman initiated the dialogue with SPIE to be the lead society for optical engineering in 2004. This paper will discuss several steps taken to develop a world-class OE program with state-of-the-art laboratory facilities for undergraduate optical engineering education.
The optical engineering program at Rose-Hulman recently developed a course titled “Optomechanics and Optical Engineering Lab.” This course focuses on the design, assembly, and alignment of benchtop optical systems in an effort to expose students to the synthesis of concepts from the areas of geometrical optics, physical optics, photonic devices, and optomechanics. Minimal guidance is provided to the students regarding procedure – students must devise their own methodology and data collection/analysis plan. We present results from the implementation of this new course and details on the projects that the students carry out in the areas of spectroscopy, interferometry, photonics, and imaging.
The Accreditation Board for Engineering and Technology (ABET) recently revised their published list of programspecific criteria. Beginning during the 2014-15 cycle, all engineering programs which include “optical” and “photonic” in their titles must meet new specific criteria to receive ABET accreditation. One portion of the wording under the curriculum section states “The curriculum must prepare students to have knowledge of and appropriate laboratory experience in: geometrical optics, physical optics, optical materials, and optical and/or photonic devices and systems.” Last year, the Rose-Hulman optical engineering curriculum committee revised our baccalaureate degree program. A portion of this effort sought to improve alignment to the ABET program-specific criteria. Here we review the outcomes of this effort, including our documented continuous improvement process, the realignment of our existing courses along the four tracks laid out by ABET, and the introduction of new undergraduate courses to improve student learning.
Capstone senior design is the culmination of a student’s undergraduate engineering education that prepares them for engineering practice. In fact, any engineering degree program that pursues accreditation by the Engineering Accreditation Commission of ABET must contain “a major design experience based on the knowledge and skills acquired in earlier course work and incorporating appropriate engineering standards and multiple realistic constraints.” At Rose-Hulman, we offer an interdisciplinary Optical Engineering / Engineering Physics senior design curriculum that meets this requirement. Part of this curriculum is a two-course sequence where students work in teams on a design project leading to a functional prototype. The students begin work on their capstone project during the first week of their senior year. The courses are deliverable-driven and the students are held accountable for regular technical progress through weekly updates with their faculty advisor and mid-term design reviews. We have found that client-sponsored projects offer students an enriched engineering design experience as it ensures consideration of constraints and standards requirements similar to those that they will encounter as working engineers. Further, client-sponsored projects provide teams with an opportunity for regular customer interactions which help shape the product design. The process that we follow in both soliciting and helping to scope appropriate industry-related design projects will be described. In addition, an outline of the capstone course structure as well as methods used to hold teams accountable for technical milestones will be discussed. Illustrative examples of past projects will be provided.
This paper presents a hybrid opto-electronic asynchronous delta-sigma modulator,
implemented in the form of a fiber-optic Analog-to-Digital converter (ADC). This architecture
was chosen for its independence of an external clock and ease of demodulation through a single
low-pass filter stage. The fiber-optic prototype consists of an input laser (wavelength λ1) which
is modulated with an input RF signal, a high-speed comparator circuit working as bi-stable
quantizer, and a fiber-optic loop that includes a SOA and a band-pass filter that act as a leaky
integrator. The fiber-optic loop acts as a fiber-ring resonator (FRR), and defines the resonance
wavelength λ2 of the system. The gain within this loop is modified through cross-gain
modulation (XGM) by the input wavelength λ1, and thus achieves the desired modulation effect.
The proposed architecture has been constructed and characterized at a sampling rate of 15.4
MS/s processing input analog signals in the range of dc-3 MHz with a signal-to-noise ratio of 36
dB and an effective number of bits of 5.7.
The delta sigma modulator (DSM) is a device which transforms the amplitude information of an analog input signal
to the duty cycle and frequency of a binary output. This device, typically employed in oversampled analog-to-digital
converters, is based on a feedback loop which includes at least one integrator and one quantizer in the forward path. In
this paper, a novel photonic second-order DSM is proposed and experimentally demonstrated. The system is composed
of two inverted leaky integrator and one electro-optic quantizer. The maximum input frequency is around 2 MHz,
limited by the fiber length of the accumulator and feedback loops, and the quantizer rise/fall times. The system is
characterized at different input frequencies and waveforms (sinusoidal and saw tooth) to analyze the modulator
performance and linearity. The binary output is acquired, processed and demodulated using a personal computer, in
order to reconstruct the input analog signal. The reported fiber-optic DSM is very promising for future integration
increasing the operation frequency up to GHz range.
A wideband photonic RF vector modulator with novel architecture is presented and demonstrated with capability of
continuous amplitude modulation and 0°-360° phase shifting. In-phase and quadrature-phase components of the output
signal are used to produce 360° continuous phase shifting and optical attenuation is used to control the signal amplitude.
A novel 8-tap all-optical transverse-filter implementing a Hilbert transform is proposed and demonstrated to produce 90° quadrature phase-shift for the broadband RF signal. Experimental apparatus and results for continuous vector modulation
will be presented for the frequency range of 1-6 GHz.
A novel optical bistable device based on an electrically coupled semiconductor optical amplifier (SOA) and a bipolar
juncture transistor (BJT) is proposed and experimentally demonstrated. The measured switching time is about 0.9-1.0 us,
mainly limited by the electrical capacitance of the SOA and the parasitic inductance of the electrical connections.
However, the effects of parasitic components can be reduced employing current electronic-photonic integration circuits
(EPIC). Numerical simulations confirm that for capacitance values in tens of femtofarads switching speed can reach tens
of GHz.
A novel optical inverted bistable switch based on a nonlinear fiber ring resonator (FRR), which contains a
semiconductor optical amplifier (SOA) in the loop, have been analyzed and experimentally demonstrated. The optical
bistability phenomenon is obtained due to the combined nonlinear effects of the transmission characteristics of the
resonator and the SOA's gain property. A complete theoretical analysis and supporting simulations are presented. A
working prototype is build using commercial optical components. Experimental results show switching speed in tens of
MHz with rising and falling times lower than 10 ns. Limitations in switching speed are caused by the length of the fiber
loop. Therefore, improvements in operating frequencies can be increased up to GHz range if the length of the loop is
reduced to the order of centimeters.
This paper presents a novel optical leaky integrator for an all-optical A/D converter based-on sigma-delta modulation.
The device consists of two main components: a fiber ring resonator (FRR) and a wavelength converter. The FRR
comprises a SOA and an optical filter that defines the resonance wavelength λ2. The modulated input signal, at
wavelength λ1, changes the gain of the loop through cross-gain modulation (XGM) and thus modifies the loop
accumulation. A theoretical model for the system is developed that accounts for critical design parameters such as the
loop coupling ratio, length, and XGM in the SOA. The system is characterized for square input signals ranging 0.5-
5MHz. The integrator time constant is adjusted between 5% and 25% of the input signal period through modifications in
the loop coupling ratio and the SOA driving-current. Experimental results show excellent agreements with the numerical
simulations. Due to the length of the fiber-loop, the operation frequency of the integrator is limited to the MHz range.
However, the operating frequency can be increased up to hundreds of MHz by shrinking the components' optical fibers,
or up to GHz range, by using current photonic integration technologies.
We developed a three quarter capstone project course sequence for our ABET accredited optical engineering program. In
the first course of the sequence we teach design methodology based on a mini-project done concurrently with lectures
outlining the product development process. The mini-project is centered on the design of an imaging system. The kit
used for this design project consists of a webcam, 20 lenses, and a collection of lens tubes and adaptors. Over the next
two quarters the students choose from a selection of client-based projects, where the focus is on team work that
culminates in a functional prototype.
A novel optical switching technique based on two electrically coupled SOAs (S-SOAD) operating in reverse-bias mode
is proposed and experimentally demonstrated. The device produces electrical and optical outputs with both non-inverted
and inverted hysteresis behavior. The S-SOAD operates on the basis of two optoelectronic effects. The first is an
electrical bistability resulting from the connection of two p-i-n structures in series. The second is the quantum-confined
Stark effect in the multi-quantum-well structure of the SOA which is responsible for the optical bistability. This effect
causes an electro-absorption modulation of the transmitted light based on the switching voltages across the p-i-n
structures.
Experiments show optical switching at MHz frequencies and rise/fall times lower than 1.1 us, limited mainly by the
electrical capacitance of the SOAs and the parasitic inductance of the connecting wires. The electrical effects can be
mitigated by photonic integrated circuit manufacturing. Predictions of the device performance at high frequencies are
based on a proposed hybrid optoelectronic model of the S-SOAD. In this model each SOA is modeled as a set of parallel
and series electronic components including optical parameters such as the responsivity and optical transmission of the
SOA. System simulations confirm that for capacitance values in tens of femto-Farads the switching-speed increases up
to GHz range. Results for the bistability behavior and switching time as a function of the electrical and optical
parameters will be presented.
We report on two types of wavelength conversion techniques that are based on gain saturation effect in semiconductor
optical amplifier (SOA) and erbium doped fiber amplifier (EDFA). In these amplifiers the gain saturation occurs when
the optical density at the gain medium is high enough to result in depletion of the population inversion by stimulated
emission. In each case, the fiber ring laser is assembled using a variable fiber coupler, a narrowband optical filter and the
gain medium. For external input power values higher than the determined threshold value of the ring resonator, the gain
will be saturated. Because the wavelength of the external laser is different from the oscillating wavelength of the ring
resonator, the optical power at the output of the resonator is drastically decreased (low-state). On the other hand, when
the input of the external laser is below the threshold value the output power of the resonator increases (high-state). In our
experiment the operating wavelengths of the ring resonators are 1314 nm and 1553 nm for the SOA and EDFA
respectively. The input signal is modulated around the threshold value for frequencies of 20 MHz and 1 MHz and
resonator lengths of around 8 m and 16 m for the SOA and EDFA cases respectively. Both systems exhibit high contrast
modulation of 41 dB and 33 dB at the output port for the low/high states of the SOA and EDFA ring lasers respectively.
The Physics and Optical Engineering department at Rose-Hulman Institute of Technology offers three degrees at the undergraduate level; physics, optical engineering, and engineering physics. The department recently transitioned a science-based applied optics degree into a B.S (Optical Engineering) degree. With this transition we began the process of seeking accreditation for the optical engineering program through the Accreditation Board of Engineering and Technology (ABET). This paper describes several assessment components of the accreditation process which includes a detailed curriculum mapping exercise to meet engineering standards. We discuss the overall outcome based optical engineering education.
UV light from an Excimer laser operating at 248 nm with fluence of 800 mJ/cm2 per pulse at 30 Hz repetition rate is used for writing process of a fiber Bragg Grating (FBG). Multiple FBGs with different center wavelength and reflectivity are produced by varying strain and exposure time on a single strand of a SMF where 1552.75 nm is the center wavelength of the unstretched FBG. The in-situ measurement of the reflectivity, bandwidth and center wavelength of each Bragg grating will be described. We will also present an RF technique for measuring the separation between two adjacent FBGs.
An optical beamformer capable of controlling a phased array antenna in receive/transmit mode for multiple simultaneous independent rf beams is proposed. The processor can be programmed to sweep the antenna aperture following an independent angular sequence for each rf beam. A two-beam two-channel version of the beamformer has been experimentally demonstrated. The optical beamformer processes two rf beams and it is based on a ternary array of three delay lines. Measurements are performed for both receive and transmit modes and for rf signals between 0.5 and 1.5 GHz. We present beampattern results showing that two independent beams can be steered simultaneously. In the transmit mode both rf beams are characterized for a broadside target position. In the receive mode the beamformer performance is characterized by detecting two rf beams independently.
We present a new architecture for a programmable disperions matrix for optical beamforming. A 2-channel prototype is constructed to demonstrate beam steering for angles of ±70° in the receive/transmit mode in RF0.1-1 GHz frequency range.
We propose a novel architecture for an optical programmable dispersion matrix (PDM) able to process simultaneous independent RF beams. The proposal is demonstrated by processing the transmission of two independent RF signals in two-channels with a resolution of 3-bit. The optical beamformer processes two independent RF-beams, for eight different angular directions, and it is based on a binary array of three delay lines. Each delay line is composed of four fiber Bragg gratings whose center wavelengths are channels 30 to 33 of the ITU grid. Beampatterns are characterized in transmit mode for two simultaneous RF beams in 0.6-1.5 GHz frequency range and azimuth angles from 0° to 70°.
We demonstrate an optical two-channel receive beamformer at 1310 nm using fiber Bragg grating arrays for producing true time delay. The antenna beam patterns are measured for broadside targets at several RF frequencies ranging from 40 MHz to 1 GHz. These results compare favorably with theoretical calculations.
Over the past four years, 2000-2003, undergraduates have participated in summer research at Rose-Hulman Institute of Technology (RHIT) carrying out a wide range of optics projects.
We propose and demonstrate a novel architecture for a programmable dispersion matrix (PDM) able to process two simultaneous independent RF beams with a resolution of 3 bits. The processor takes advantage of wavelength division multiplexing (WDM) encoding. In our two-channel approach, four adjacent ITU optical WDM channels are used as optical carriers. The odd and even optical carriers are independently modulated with each received RF-beam using electro-optic modulators. Thus, each pair of optical carriers directs RF information of one beam. The PDM is programmed to introduce independent true-time delays for even and odd optical channels. The PDM is based on three optical delay lines, arranged in a binary configuration. Each delay line consists of four fiber-Bragg gratings (FBG), with each FBG having a center-wavelength at one of the optical WDM channels. Beampatterns are characterized in receive mode for RF signals in 0.5-1.5 GHz frequency range obtained for target angles of 0° to 70°. The measurement results demonstrate the simultaneous processing of two received RF-beams and the squint free nature of the beamformer.
In this paper we implement and characterize a two-channel optical programmable beamformer. The system is designed to achieve four-bit resolution. The architecture of the programmable dispersion matrix is based on an array of four delay-lines each having two spliced fiber Bragg gratings. We have experimentally investigated the optical signal processing performance of the optical beamformer in receive and transmit modes. Beampatterns for RF range 40 - 200 MHz are presented along with the theoretical calculations. The main lobe of the beampattern is shown to be independent of frequency for several target positions thus demonstrating a “squint-free” characteristic of this optical processor.
A single sideband suppressed-carrier (SSB-SC) optical modulator is demonstrated. The sideband is suppressed by means of a fiber Mach-Zehnder interferometer with amplitude electro-optical modulators in each branch. The attenuation of the carrier is achieved by proper biasing of the integrated modulators. The proposal was demonstrated by modulating at 285 MHz. Suppression of 30.8 dB in the carrier and 26.3 dB in the sideband were obtained.
This paper describes implemented methods for characterizing a 5-bit programmable dispersion matrix (PDM) that is built to control a two-channel Receive beamformer in the 1550 nm region. The architecture of the PDM, is based on an array of 5 delay lines each having two spliced fiber Bragg gratings. Phase measurements for 32 possible delay configurations of the PMD are presented. Beam-patterns of this Receive beamformer at RF frequencies of 0.2, 0.5 and 1 GHz agrees well with the theoretical calculations. The main lobe of the beam pattern is shown to be independent of frequency for several target positions thus demonstrating a 'squint-free' characteristic of this optical processor.
We present a simple scheme for implementation of optical single sideband suppressed carrier (OSSB-SC) modulation based on the use of standard MZM and passive fiber optic components. The function of the proposed modulator is also theoretically predicted. A Sagnac interferometer structure is used for sideband suppression. The light propagating in one direction is orthogonally linearly polarized to the oppositely propagating light. The orthogonal polarization is implemented by a non-reciprocal optical element. The optical carrier is attenuated by appropriately setting the Mach-Zender Modulator (MZM) at quadrature bias point. We will experimentally demonstrate sideband suppression and carrier attenuation up to 28 dB by using all commercially available components.
We perform double sideband and single sideband suppressed- carrier modulators using a Mach-Zehnder interferometer in free space. Two bulk LiNbO3 crystals are used to modulate the optical beam at 1319 nm in both branches of the interferometer. We present experimental results of the optical spectrum using heterodyne measurement technique. These results show maximum carrier and sideband suppression of 24 dB and 12 dB respectively for 1 GHz modulation frequency.
The expression of the field amplitude associated with ultra- short light pulses is analyzed using the phase-space formalism for the Wigner distribution function (WDF). By properly modifying the diffraction integral to take into account the dispersion effects, we derive a 2D WDF, from which the on-axis intensity is obtained for varying time and defocus. Thus, the behavior of the optical system can be visualized as a 3D irradiance display in a combined space- temporal domain. The performance of three different pupil functions are investigated, by comparing their imaging properties.
The optical implementation of the Radon-Wigner display for 1D objects is used in two different applications. First, it is used in the study of some properties of the wave field diffracted by unidimensional fractal gratings in the Fresnel region. Second, this optical representation is profited to perform a parallel space-variant optical correlation. Computer simulations and experimental results are presented.
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