This work reports the experimental demonstration of supercontinuum (SC) generation with broad spectral output of 950 nm maximum or a 3.7 dB variation within the range from 1300 to 1600 nm and demonstrate how some fiber properties enhance nonlinearities and shows different SC output spectrum. Broad spectrum was achieved throughout a subnanosecond microchip pulsed laser operating at 1064 nm. Three different conventional fibers were employed: highnumerical aperture fiber (HNAF), dispersion shifted fiber (DSF) and single mode fiber (SMF). SMF was wrapped in different diameters to induce fiber losses. Several combinations of these three fibers and diameters resulted in high spectral width as well as high flatness in the telecom band.
Performance of optical heterodyning and external modulation by using an electro-optical modulator technique is evaluated. The first approach is carried out by beating two optical signals with a wavelength spacing corresponding to the desired microwave or millimeter-wave frequency continually tuned. The second technique requires only a single laser source along with a Mach-Zehnder Intensity Modulator (MZ-IM). Due to the available electrical bandwidth of the photodetector used, the experimental results are limited to the frequency range of 13 GHz. All experimental results are validated by a series of simulations using the VPI software. Signal-to-Noise ratio (SNR) and Phase-Noise parameters are measured.
KEYWORDS: Analog electronics, Microwave radiation, Bandpass filters, Microwave photonic filters, Optical filters, Optical fibers, Electronic filtering, Signal to noise ratio, Dispersion, Fiber to the x
A practical application of a bidirectional microwave photonic filter (MPF) to transmit simultaneous analog TV signals coded on microwave carriers is experimentally demonstrated. The frequency response of the bidirectional MPF is obtained by the interaction of an externally modulated multimode laser diode emitting at 1.55 μm associated to the free-spectral range of the optical source, the chromatic dispersion parameter of the optical fiber, as well as the length of the optical link. The filtered microwave bandpass window generated around 2 GHz is used as electrical carrier in order to simultaneously transmit TV signals of 67.25 and 61.25 MHz in both directions. The obtained signal-to-noise ratios for the transmitted signals of 67.25 and 61.25 MHz are 37.62 and 44.77 dB, respectively.
The aim of this paper is to describe the design and simulation of an optical waveguide for its potential integration with
an optical source based on silicon rich oxide (SRO), on a silicon substrate. SRO deposited by Low Pressure Chemical
Vapor Deposition (LPCVD) has emission of light in the visible range, and then our goal is to integrate this optical source
with an appropriate optical waveguide. In this sense, we describe the methodology followed for the design of the optical
waveguide able to transmit light emitted in the wavelength range from 400 to 800 nm. Due to its optical properties and
compatibility with silicon technology the core material selected for the waveguide is silicon nitride (Si3N4), surrounded by silicon oxide (SiO2). The optimal dimensions and geometry that reduces losses and confine the light into the core zone are obtained by simulation.
A modulator fundamental part of Mach Zhender interferometer is studied. This interferometer has applications such as a sensor or spectral analyzer. The modulator was designed on a SOI substrate comprising a dual capacitor structure that allows the electro optical modulation through the overlap of the plasma dispersion effect (variations of the free carriers density due to electric field induced carrier depletion) with the guidewave mode that induce the change of the effective refractive index. The modulator is excited by a tension ramp between 0 and 2V yielding performance exceeding 7 GHz.
We describe an analog microwave photonic link system, which is used to transmit in a multiplexed way a TV signal over 30 km of standard optical fiber. The experimental setup is composed mainly by two distributed feedback (DFB) laser diodes emitting at 1500 nm. When these DFB lasers are operated in the low laser threshold current region, relaxation oscillation frequencies are obtained. Relaxation oscillations in the laser intensity can be seen as sidebands on both sides of the main laser line. The optical emissions generated in each laser are combined and amplified by using an erbium-doped fiber amplifier. Next, the amplified optical signal is detected by a fast photo-detector using direct detection method, and as result of this photo-detection, microwave signals are generated. Since microwave signals obtained by using this technique are tuned continuously; we can use them as electrical carriers to transmit simultaneously a TV signal at 4 and 5 GHz and over 30 km of standard optical fiber by using a Mach-Zehnder modulator. At the end of the optical link the modulated light is photo-detected in order to recover efficiently and successfully the analog TV signal.
In this paper we describe an analog microwave photonic link system used to transmit simultaneously two TV signals.
The experimental setup is composed mainly by two distributed feedback (DFB) laser diodes emitting at 1500 nm. When
DFB lasers are operated in the low laser threshold current region, relaxation oscillation frequencies are obtained.
Relaxation oscillations in the laser intensity can be seen as sidebands on both sides of the main laser line. The optical
emissions generated in each laser are combined and amplified by using an Erbium-Doped Fiber Amplifier (EDFA).
Next, the amplified optical signal is detected by a fast photo-detector using direct detection method and as result of this
photo-detection microwave signals are generated. Microwave signals obtained by this technique are used as electrical
carriers to transmit analog TV signals over 30 km of standard optical fiber by using a Mach-Zehnder modulator (MZM).
At the end of the optical link the modulated light is photo-detected in order to recover efficiently and successfully the
analog TV signals.
We demonstrate Ge metal-semiconductor-metal (MSM) photodetectors monolithically integrated with silicon-oxynitride
(SiOxNy) waveguides. Ge photodetector layer was epitaxially grown by an UHVCVD system and the
waveguide was formed on top of the Ge photodetector by PECVD. The entire process is found to be completely
compatible with the standard CMOS process. Light is evanescently coupled from silicon-oxynitride (SiOxNy)
waveguide to the underlying Ge photodetector, achieving at 2 V a responsivity of 0.33 A/W at 1.55 μm wavelength
and a dark current of 1 μA for a 10 μm long photodetector.
Relaxation oscillation frequency is produced when a laser is operated in the low laser threshold current region. In this
operation region, a semiconductor laser shows a smooth curve, where we can observe uncertainty into defining the onset
of laser oscillation. Relaxation oscillations in the laser intensity can be seen as sidebands on both sides of the main laser
line. In this context, a communication system by using a relaxation oscillation frequency as an information carrier is
proposed in this paper. The experimental setup is based on operation principle of direct detection, where the obtained
microwave signal at the output of a fast photodetector is located on C band and it is modulated with an analog NTSC TV
signal.
In this work we report the photonic generation of microwave signals for distributing point to point analog TV signals by
using microstrip antennas. The experimental setup is based on optical heterodyne technique where two optical waves at
different wavelengths are mixed and applied to a photodetector. The microwave signal obtained by using this technique
is used in a wireless communication system for transmitting and receiving analog TV signals.
The generation, distribution and processing of microwave signals in the optical domain is a topic of research
due to many advantages such as low loss, light weight, broadband width, and immunity to electromagnetic
interference. In this sense, a novel all-optical microwave photonic filter scheme is proposed and experimentally
demonstrated in the frequency range of 0.01-15.0 GHz. A microwave signal generated by optical mixing drives the
microwave photonic filter. Basically, photonic filter is composed by a multimode laser diode, an integrated Mach-
Zehnder intensity modulator, and 28.3-Km of single-mode standard fiber. Frequency response of the microwave
photonic filter depends of the emission spectral characteristics of the multimode laser diode, the physical length
of the single-mode standard fiber, and the chromatic dispersion factor associated to this type of fiber. Frequency
response of the photonic filter is composed of a low-pass band centered at zero frequency, and several band-pass
lobes located periodically on the microwave frequency range. Experimental results are compared by means of
numerical simulations in Matlab exhibiting a small deviation in the frequency range of 0.01-5.0 GHz. However,
this deviation is more evident when higher frequencies are reached. In this paper, we evaluate the causes of
this deviation in the range of 5.0-15.0 GHz analyzing the parameters involved in the frequency response. This
analysis permits to improve the performance of the photonic microwave filter to higher frequencies.
The filtering and multiplexing of microwave signals in the frequency range of 0.01 to 4 GHz is experimentally demonstrated. Filtering is obtained by the spectral characteristics of a 1.5-µm multimode laser diode (MLD) and the chromatic fiber-dispersion parameter. Multiplexing is based on the use of appropriated optical delays generated by the use of a Michelson interferometer that allows a very precise adjustment of the free spectral range (FSR) of the MLD used. Experimental results are validated by means of numerical simulations. To show potential applications in the area of optical communications, a filtered microwave signal is used as a microwave electric-carrier transmitting TV-video signal on a long-distance optical telecommunication system. This is achieved by using an external modulation technique over 28.3 km of a single-mode standard fiber, and using an MLD diode emitting at an optical wavelength around 1.5 µm.
In this paper, we propose and analyze a versatile structure of electro-optical modulator on a polysilicon rib waveguide. The structure confines both optical field and charge carriers in a micron-size region. The optical field is confined by using a coplanar waveguide (CPW) structure. Software based on the Finite Element Method (FEM), allows a complete analysis of the distribution and penetration of the electric field (E) within the polysilicon rib waveguide. This analysis is validated by the use of Kramers-Kronig dispersion relations.
In this work we developed an integral study of the microwave electro-optic modulators. We have analyzed two possible configurations. The per- unit-length parameters such capacitance and impedance are calculated. The frequency response is calculated considering conductor losses. Results of numeric simulations are included.
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