| 1. |
- Pérez-Millan, Pere, et al.
(författare)
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Optical demultiplexing of millimeter-wave subcarriers for wireless channel distribution employing dual wavelength FBGs
- 2007
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Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018. ; 275:2, s. 335-343
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Tidskriftsartikel (refereegranskat)abstract
- An optical mm-wave demultiplexer is presented. Double sideband modulation with suppressed optical carrier and filtering properties of dual overwritten fiber Bragg gratings are the fundamentals for optical demultiplexing of mm-wave radio-on-fiber signals: using a single optical carrier, Millimeter-wave signals of 20 and 40 GHz frequencies carrying independent data are created, transmitted over fiber, demultiplexed and wireless distributed to be detected and data recovered in a mobile unit. Double sideband modulation with suppressed optical carrier yields no power penalty due to chromatic dispersion, while the filtering properties of the dual overwritten fiber Bragg gratings allow less than −40 dB electrical power interchannel leakage. Independent 2.5 Gb/s On–Off-keyed data have been successfully transmitted through the 20 and 40 GHz channels.
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| 2. |
- Wiberg, Andreas, 1978, et al.
(författare)
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Fiber-Optic 40-GHz mm-Wave Link With 2.5-Gb/s Data Transmission
- 2005
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 17:9, s. 1938-1940
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Tidskriftsartikel (refereegranskat)abstract
- A broad-band millimeter-wave (mm-wave) transmission link for downstream transmission is investigated. The mm-wave carrier is created by a dual-frequency optical source based on suppressed-carrier double-sideband modulation of a narrow linewidth laser. The optical sidebands generated in the modulation are divided into two separate fibers by filtering with fiber Bragg gratings. One of the waves is modulated with baseband data up to 2.5 Gb/s. The fibers are combined and connected with the base station (BS) via a single-mode fiber. At the BS, the mm-wave modulated signal with data is created with a wide bandwidth photodetector through heterodyne mixing of the two optical waves. This mm-wave signal is amplified and transmitted to the mobile unit, where the reception is performed using self-homodyne mixing, in order to ensure carrier frequency independence. Error-free data transmission was demonstrated for the downlink after 44 km of single-mode optical fiber.
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| 3. |
- Ghatnekar-Nilsson, Sara, et al.
(författare)
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Resonators with integrated CMOS circuitry for mass sensing applications, fabricated by electron beam lithography
- 2005
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 16:1, s. 98-102
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Tidskriftsartikel (refereegranskat)abstract
- A resonator system has been fabricated directly on a pre-processed CMOS chip. The system is to be used for high sensitivity mass sensing applications in air and vacuum. The resonator system, corresponding of a cantilever and structures for electrostatic actuation and capacitive read-out, have been defined by electron beam lithography on top of a charge and radiation sensitive CMOS layer in predefined areas as a post-process step. This has been accomplished without affecting the electronic properties of the pre-processed CMOS circuits. The subsequent etching steps to fully release the cantilevers have been obtained without stiction of the cantilevers to the substrate. Cantilevers are driven at their mechanical resonance in a lateral mode, and the frequency is monitored by capacitive read-out on the chip. CMOS integration enables signal detection directly on the chip, which radically decreases the parasitic capacitances. Consequently, low-noise electrical measurements with a very high mass sensitivity are obtained. Fabricated resonator systems were characterized to have resonance frequencies of approximately 1.49 MHz, which is in good agreement with a theoretical estimation of 1.41 MHz. The theoretical mass resolution, partial derivativem/partial derivativef, is approximately 17 ag Hz(-1) using a Young modulus value of 160 GPa.
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| 4. |
- Olmos, R., et al.
(författare)
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Anomalous emissions of SO2 during the recent eruption of Santa Ana volcano, El Salvador, Central America
- 2007
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Ingår i: Pure and Applied Geophysics. - : Springer Science and Business Media LLC. - 0033-4553 .- 1420-9136. ; 164:12, s. 2489-2506
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Tidskriftsartikel (refereegranskat)abstract
- Santa Ana volcano in western El Salvador, Central America, had a phreatic eruption at 8:05 am (local time) on October 1, 2005, 101 years after its last eruption. However, during the last one hundred years this volcano has presented periods of quiet degassing with fumarolic activity and an acidic lake within its crater. This paper presents results of frequent measurements of SO2 degassing using the MiniDOAS (Differential Optical Absorption Spectroscopy) system and a comparison with the volcanic seismicity prior to the eruption, during, and after the eruption. Vehicle measurements of SO2 flux were taken every hour during the first nine days of the eruption and daily after that. The period of time reported here is from August to December, 2005. Three periods of degassing are distinguished: pre-eruptive, eruptive, and post-eruptive periods. The intense activity at Santa Ana volcano started in July 2005. During the pre-eruptive period up to 4306 and 5154 ton/day of SO2 flux were recorded on October 24 and September 9, 2005, respectively. These values were of the same order of magnitude as the recorded values just after the October 1(st) eruption (2925 ton/day at 10: 01 am). Hourly measurements of SO2 flux taken during the first nine days after the main eruptive event indicate that explosions are preceded by an increase in SO2 flux and that this parameter reaches a peak after the explosion took place. This behavior suggests that increasing accumulation of exsolved magmatic gases occurs within the magmatic chamber before the explosions, increasing the pressure until the point of explosion. A correlation between SO2 fluxes and RSAM (Real Time Seismic Amplitude Measurements) is observed during the complete sampling period. Periodic fluctuations in the SO2 and RSAM values during the entire study period are observed. One possible mechanism explaining these fluctuations it that convective circulation within the magmatic chamber can bring fresh magma periodically to shallow levels, allowing increasing degasification and then decreasing degasification as the batch of magma lowers its gas content, becomes denser, and sinks to give space to a new magma pulse. These results illustrate that the measurements of SO2 flux can provide important warning signals for incoming explosive activity in active volcanoes.
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| 5. |
- Perez-Millan, Pere, et al.
(författare)
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Dispersion induced effects of high-order optical sidebands in the performance of millimeter-wave fiber-optic links
- 2006
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Ingår i: Microwave and optical technology letters. ; 48:7, s. 1436-1441
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, chirped fiber Bragg gratings (CFBGs) areproposed as signal-phase controllers for microwave-photonic wireless downstream fiber links. The effect of high-order modulation optical sidebands that disturbs the output mm-wave signal due to the chromatic dispersion induced by the gratings is studied theoretically and experimentally. The 1st and 2nd mm-wave harmonics of the output signal have been measured for conventional intensity modulation and for intensity modulation with optical carrier suppression. In the last case, data transmission at 2.5 Gb/s is demonstrated through a chirped grating of 280 ps/nm dispersion in a 40-GHz modulated link.
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| 6. |
- Wiberg, Andreas, 1978, et al.
(författare)
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Evaluation of All-Optical Demultiplexing in Millimeter-Wave Subcarrier-System for Wireless Communication
- 2006
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Ingår i: Proceedings of International Topical Meeting on Microwave Photonics. - 1424402042 ; Paper T2.2
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Konferensbidrag (refereegranskat)abstract
- In this paper, a scheme for multiplexing millimeter-wave carriers on a single optical carrier and using an all-optical millimeter-wave demultiplexer is presented. The optical demultiplexing of radio-over-fiber signals is based on dual sideband modulation with suppressed optical carrier combined with the filtering properties of dual over-written fiber Bragg gratings. The performance of the system is investigated using a single optical carrier and independent data modulated millimeterwave signals at 20 and 40 GHz. The signals are transmitted over optical fiber, demultiplexed and wirelessly distributed to a mobile unit. It is found that performance of the demultiplexing using fiber Bragg gratings gives less than -40 dB electrical power interchannel crosstalk and the spurious free dynamic range is measured to be 80 dB.Hz^(2/3). Furthermore, PSK, QAM and ASK PRBS modulated dataup to 2.5 Gb/s are successfully transmitted through thewireless link.
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| 7. |
- Wiberg, Andreas, 1978, et al.
(författare)
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Microwave-photonic frequency multiplication utilizing optical four-wave mixing and fiber Bragg gratings
- 2006
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 24:1, s. 329-334
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Tidskriftsartikel (refereegranskat)abstract
- A novel technique for optical multiplication of a millimeter-wave carrier is presented. It utilizes optical four-wave mixing (FWM) in a highly nonlinear fiber (HNLF) and the filtering properties of matched fiber Bragg gratings (FBGs). The technique includes a sixfold electrical frequency multiplication in the optical domain. In this experiment, the multiplicator is driven electronically at 6.67 GHz, and the created millimeter wave has a frequency of 40 GHz. The generated carrier has a linewidth lower than 3 Hz and a carrier to noise ratio exceeding 50 dB. Furthermore, successful data transmission over the optical fiber of 2.5 Gb/s on the generated millimeter-wave carrier was performed.
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