Traditional electronic communications curriculum spends large amount of time to cover the electronic circuits for communications. Since highly integrated circuits for communications are now available, in many cases a blockdiagram level analysis is sufficient. On the other hand, fiber optics for communications has been used not only for long haul transmission of information, but also local area networks and computer networks. To stay relevant and keep up with industry trends without adding new courses, we revised existing two-semester electronic communications curriculum by replacing some circuit details with topics on optical fiber communications fundamentals and wavelength division multiplexing techniques. Since optical fiber communications itself can be a course of one or two semesters, we are not intending to cover the topic in all aspects. Instead, our goal is to introduce the highlights of the major topics necessary for students to understand basics of optical fiber communications. To make the topic transition logically we introduced the light source in fiber optics topic, after establishing the modulation/demodulation concept, as an alternative carrier signal for modulation process. We then introduced optical fibers as transmission channel for modulated optical carriers, followed by other components (optical sources, detectors, and etc.). Wavelength division multiplexing had also been introduced as one of the major multiplexing techniques, after introducing the time division multiplexing and frequency division multiplexing concepts, for both long haul and high speed Ethernet applications. Through the midterm/final examinations students demonstrated similar level of understanding of the traditional materials as before. At the same time their basic knowledge on optical fiber communications were established.
This paper presents the optical and lens design for alignment to meet the challenging position specifications. Fabrication
of the prototypes and testing results and analysis are also presented. The system components as well as their interaction
with each other were simulated with Zemax software and tested in an experimental setup in order to conduct tolerance
study and provide specifications for the mechanical fixtures used in the system. The epoxy is used to affix the parts
together in a cost effective manner for prototyping. The position accuracy of ±3 μm compared to the golden unit has
Temperature stability is one of the major obstacles that prevent the application of optical current sensors (OCSs) in the power industry. A simple yet effective method using thermoelectric effect and software packages to compensate for temperature drift of an OCS based on the Faraday effect is reported. A self-excited thermoelectric component is used to monitor the temperature of the Faraday element. The resolution of 1°C in temperature range from -40 to 80°C can be achieved. Combining accurate temperature information with software, the OCS with improved temperature stability has been demonstrated.
Because PDMS is viscous, it's impossible to form thin films of PDMS using spin coating without dilute it
with solvents. We examine the optimal solvents and spin parameters for spin-coating the PDMS elastomer on glass
substrates. Chloroform, Benzene, and Toluene have been attempted to study the influences of solvent on forming
thin films of high uniformity. The experiments conclude: the solvent with lower evaporation rate produces more
uniform films. No strong relationship between spin speeds and film uniformity has been observed when spin speed
is high. However, the film uniformity begins to decline when lower spin speed is used. In addition, we find that the
refractive index of the thin film can be modified by curing temperature.
The Michelson interferometer-based interleaver is widely used in wavelength-division multiplexing (WDM) systems. A performance comparison for a 10-gigabit/s WDM system with a Michelson interferometer-based interleaver of different designs is presented. The trade-off between the designs that improve the passband bandwidth and reduce chromatic dispersion is discussed. It is concluded that a comprehensive design, including analysis at both the component and system levels, is necessary.
We report a simple yet effective method to improve the accuracy of an optical current sensor (OCS) by compensating the
temperature dependency of the Verdet constant with a low-power source operating at a known frequency combined with
a lookup table. Neither a complex digital signal processing system nor extra rare earth bulk glass material is used to
achieve the accuracy of the current's measurement. Modeling and simulations are carried out. An OCS has been
designed and fabricated. The dynamic range of 1620 RMS ampere with a sensitivity of 0.36 ampere is achieved with a
single-path SF57 bulk glass.
Dynamic DWDM channel blocking and equalizing is proposed based on liquid crystal (LC) and bulk grating technology. A dispersion compensation and enhancement unit is employed so that low center-frequency shift small footprint could be achieved at the same time. The inter-channel crosstalk is also studied. With the optimized design of dispersion unit and LC module, a 32-channel, 100-GHz spacing sample is demonstrated with the insertion loss (IL) of 5.5 dB and 45dB extinction ratio. Application of our device to reconfigurable optical add-and-drop (ROADM) network is discussed
Inter-channel crosstalk for a liquid crystal-based dynamic channel blocker/equalizer has been experimentally studied.
With the optimal interpixel width, a 32-channel, 100-GHz channel-spacing sample is fabricated and characterized. The
maximum insertion loss (IL) of 5 dB and the polarization dependent loss (PDL) of 0.5 dB within the ITU ± 14 GHz are
achieved. The 45 dB extinction ratio is obtained. The variations of the IL and PDL within the temperature range from - 5°C to 65°C cross the C-band are less than 1 dB and 0.4 dB respectively.
The effect of an interpixel gap on light leakage in a free-space liquid-crystal-based dynamic channel blocker/equalizer is studied. The electric field components along the driving electric field within the liquid crystal interpixel gap are numerically calculated. The results show nonuniform distributions in both width and thickness. The numeric results on the relation between gap width and electric field distribution are also presented. A 20-channel, 200-GHz channel-spacing blocker/equalizer on the C band with flat tops and a 40-dB extinction ratio is fabricated and examined.
All-polymer capacitors are fabricated using the laser direct pattering combined with a novel lifting procedure. This
parallel plate capacitor is achieved by using a highly doped silicon wafer and poly(3,4-ethylenedioxythiophene) as the
electrodes and Norland Optical Adhesive 61 as the dielectric material. The resulting polymeric capacitor is characterized
and analyzed for suitability in electronic circuits. The method offers an attractive processing technique as it does not
require high temperatures, the need of a vacuum environment, or masks, providing a low cost prototyping with quick
turn around time in the design and realization of capacitors that have applications in all polymer IC technology.
The effect of an imperfect antireflection (AR) coating on a birefringent interleaver (an important optical communication component) and on an optical communications system containing such a birefringent interleaver is investigated. We demonstrate how the imperfect AR coating on the rhomb surfaces affects the birefringent interleaver's intensity spectrum and generates undesirable chromatic dispersion (CD) ripples for an interleaver that should be dispersion-free by design. Our results show that a rhomb with a close-to-perfect AR surface coating (T=99.8%) can still generate a ±30-ps/nm CD ripple, causing a nonnegligible power penalty in an optical communications system. We also demonstrate a simple and practical approach to reduce the CD ripple caused by the imperfect AR coating.
We report the study of chromatic dispersion ripples in birefringent crystal-based optical interleavers. The simulation indicates that for a 99.8% transmittance AR coating surface, the chromatic dispersion ripples caused by the Rhomb etalon effect could be as high as ±30 ps/nm. The experimental results are in agreement with the simulation results. We also demonstrate a practical approach to eliminate the chromatic dispersion ripples to be coupled into the output collimators. The overall interleaver chromatic dispersion, of less than 15 ps/nm within the passband, is demonstrated.
A focused 375 nm laser diode module is used to fabricate optical channel waveguides on Si wafers using commercially
available inorganic-organic hybrid polymers. The fabrication process eliminates all the complex steps associated with
the definition of structures using photolithographic techniques, making rapid prototyping of integrated optic devices
possible. Channel waveguides with smooth side-walls are fabricated and characterized. The losses, measured using
cutback loss measurement method, are typically less than 1dB/cm, making them especially applicable to Si based optical